WO2013031745A1 - Polyethylene resin foamed particles and molded articles thereof - Google Patents

Polyethylene resin foamed particles and molded articles thereof Download PDF

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Publication number
WO2013031745A1
WO2013031745A1 PCT/JP2012/071633 JP2012071633W WO2013031745A1 WO 2013031745 A1 WO2013031745 A1 WO 2013031745A1 JP 2012071633 W JP2012071633 W JP 2012071633W WO 2013031745 A1 WO2013031745 A1 WO 2013031745A1
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polyethylene resin
particles
expanded particles
polyethylene
resin
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PCT/JP2012/071633
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French (fr)
Japanese (ja)
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清敬 中山
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株式会社カネカ
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
    • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
    • C08L23/04—Homopolymers or copolymers of ethene
    • C08L23/08—Copolymers of ethene
    • C08L23/0807—Copolymers of ethene with unsaturated hydrocarbons only containing more than three carbon atoms
    • C08L23/0815—Copolymers of ethene with aliphatic 1-olefins
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/0014—Use of organic additives
    • C08J9/0023—Use of organic additives containing oxygen
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/0014—Use of organic additives
    • C08J9/0028—Use of organic additives containing nitrogen
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/0061—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof characterized by the use of several polymeric components
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/04—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent
    • C08J9/12—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof using blowing gases generated by a previously added blowing agent by a physical blowing agent
    • C08J9/122—Hydrogen, oxygen, CO2, nitrogen or noble gases
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/16—Making expandable particles
    • C08J9/18—Making expandable particles by impregnating polymer particles with the blowing agent
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/22—After-treatment of expandable particles; Forming foamed products
    • C08J9/228—Forming foamed products
    • C08J9/232—Forming foamed products by sintering expandable particles
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2203/00—Foams characterized by the expanding agent
    • C08J2203/06—CO2, N2 or noble gases
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2205/00—Foams characterised by their properties
    • C08J2205/04—Foams characterised by their properties characterised by the foam pores
    • C08J2205/046—Unimodal pore distribution
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2205/00—Foams characterised by their properties
    • C08J2205/04—Foams characterised by their properties characterised by the foam pores
    • C08J2205/052—Closed cells, i.e. more than 50% of the pores are closed
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
    • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
    • C08J2323/04—Homopolymers or copolymers of ethene
    • C08J2323/08—Copolymers of ethene
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2471/00—Characterised by the use of polyethers obtained by reactions forming an ether link in the main chain; Derivatives of such polymers
    • C08J2471/02—Polyalkylene oxides
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/04—Oxygen-containing compounds
    • C08K5/05—Alcohols; Metal alcoholates
    • C08K5/053—Polyhydroxylic alcohols
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/16—Nitrogen-containing compounds
    • C08K5/34—Heterocyclic compounds having nitrogen in the ring
    • C08K5/3467—Heterocyclic compounds having nitrogen in the ring having more than two nitrogen atoms in the ring
    • C08K5/3477—Six-membered rings
    • C08K5/3492—Triazines
    • C08K5/34922—Melamine; Derivatives thereof

Definitions

  • the present invention relates to polyethylene resin foamed particles and polyethylene resin foamed molded articles made of polyethylene resin foamed particles.
  • Polyethylene-based resin foamed molded articles are excellent in flexibility and heat insulation properties, and are therefore used in various applications as buffer packaging materials and heat insulating materials.
  • foamed particles obtained by foaming polyethylene resin particles with a foaming agent such as butane gas in advance (bead foaming) are filled in a mold, and a heat medium such as water vapor is introduced.
  • a foaming agent such as butane gas in advance
  • a heat medium such as water vapor
  • Patent Document 3 discloses linear low-density polyethylene pre-expanded particles copolymerized with 1-butene having a weight average molecular weight Mw / number average molecular weight Mn of 3 to 7, and molding with a smooth surface. Although the body was obtained, there was a problem that the range of vapor pressure that could be molded was narrow. When the technique disclosed in Patent Document 3 is followed, similar problems occur even when a comonomer having 6 or 8 carbon atoms is copolymerized.
  • Ultrazex 2022L is a linear low density polyethylene resin.
  • Ultrazex 2022L has a density of 0.920 g / cm 3 , a melt flow rate (hereinafter sometimes referred to as “MFR”) of 2.0 g / 10 minutes, and a molecular weight distribution Mw / Mn of 3.8. It is a copolymer with an ⁇ -olefin of formula 6.
  • MFR melt flow rate
  • the foamed particles tend to break and the open cell ratio tends to increase.
  • the average cell diameter of the polyethylene resin foamed particles is too small, there is a problem that the range of vapor pressure that can be molded is narrow, and when the open cell rate is high, the shrinkage of the in-mold foam molded product is remarkably usable. The problem remains that the molded body does not become a proper molded body.
  • a polyethylene resin is a mixture of an ethylene unit and an ⁇ -olefin unit having 3 to 20 carbon atoms, that is, a density of 900 to 940 kg / m 3 and a specific melt.
  • a method of using a mixture of a copolymer having a flow rate, a weight average molecular weight Mw / number average molecular weight Mn, fluid activation energy and a copolymer having a density of 941 to 970 kg / m 3 has also been proposed (Patent Literature). 8).
  • the present invention provides a polyethylene resin foam molded article having a wide range of vapor pressure that can provide a good molded article at the time of molding, a small dimensional shrinkage ratio to the mold after molding, and a beautiful surface. It is in providing a resin-based expanded resin particle.
  • the present inventor has obtained a linear low-density polyethylene-based resin having a specific density and a melt flow rate and having an Mw / Mn of 3 or more and less than 5.
  • the resulting non-crosslinked polyethylene resin foam molded article has a small shrinkage ratio against the mold.
  • the inventors have found that a molded article having a beautiful surface can be obtained, and have completed the present invention.
  • the present invention has the following configuration.
  • Polyethylene resin foamed particles obtained by foaming polyethylene resin particles using a linear low density polyethylene resin satisfying the following conditions (a) to (d) as a base resin, A polyethylene-based resin expanded particle having an average cell diameter of 200 ⁇ m or more and 700 ⁇ m or less and an open cell ratio of 12% or less.
  • the linear low density polyethylene resin is a copolymer of ethylene and an ⁇ -olefin having 6 and / or 8 carbon atoms.
  • the density is 0.920 g / cm 3 or more and less than 0.940 g / cm 3 .
  • the melt flow rate (MFR) is 0.1 g / 10 min or more and 5.0 g / 10 min or less.
  • MFR melt flow rate
  • Mw / Mn molecular weight distribution measured by gel permeation chromatograph (GPC) is 3 or more and less than 5.
  • GPC gel permeation chromatograph
  • the base resin contains 0.01 to 10 parts by weight of a hydrophilic compound with respect to 100 parts by weight of the linear low-density polyethylene resin.
  • Polyethylene resin foam obtained by filling the polyethylene resin foamed particles according to any one of [1] to [6] into a mold and then performing in-mold foam molding Molded body.
  • the first-stage expanded particles are placed in a pressurized tank, and air is introduced into the first-stage expanded particles by pressurizing with an inorganic gas to increase the internal pressure of the expanded particles from atmospheric pressure, and then the first-stage expanded particles are heated with water vapor.
  • the A method for producing expanded polyethylene resin particles having an average cell diameter of 200 ⁇ m or more and 700 ⁇ m or less and an open cell ratio of 12% or less.
  • the linear low-density polyethylene-based resin is a copolymer of ethylene and an ⁇ -olefin having 6 and / or 8 carbon atoms.
  • the density is 0.920 g / cm 3 or more and less than 0.940 g / cm 3 .
  • the melt flow rate (MFR) is 0.1 g / 10 min or more and 5.0 g / 10 min or less.
  • MFR melt flow rate
  • Mw / Mn measured by gel permeation chromatograph (GPC) is 3 or more and less than 5.
  • polyethylene resin foamed particles of the present invention it is easy to obtain a polyethylene resin foam molded article having a wide vapor pressure range, a small mold dimensional shrinkage, and a beautiful surface. Obtainable.
  • the polyethylene-based resin expanded particles of the present invention are obtained by expanding polyethylene-based resin particles having a linear low-density polyethylene-based resin that satisfies the following conditions (a) to (d) as a base resin. Expanded particles, Polyethylene resin foamed particles having an average cell diameter of 200 ⁇ m or more and 700 ⁇ m or less and an open cell ratio of 12% or less.
  • the linear low density polyethylene resin is a copolymer of ethylene and an ⁇ -olefin having 6 and / or 8 carbon atoms.
  • the density is 0.920 g / cm 3 or more and less than 0.940 g / cm 3 .
  • the melt flow rate (MFR) is 0.1 g / 10 min or more and 5.0 g / 10 min or less.
  • MFR melt flow rate
  • Mn molecular weight distribution measured by gel permeation chromatograph
  • the linear low density polyethylene resin used in the present invention is a copolymer of ethylene and an ⁇ -olefin having 6 and / or 8 carbon atoms.
  • the ⁇ -olefin having 6 and / or 8 carbon atoms include 1-hexene, 3,3-dimethyl-1-butene, 4-methyl-1-pentene, and 1-octene. Both ⁇ -olefins having 6 and 8 carbon atoms may be copolymerized.
  • a linear low density polyethylene resin copolymerized with an ⁇ -olefin having 6 carbon atoms and a linear low density polyethylene resin copolymerized with an ⁇ -olefin having 8 carbon atoms are mixed and used. Also good.
  • the ⁇ -olefin is preferably an ⁇ -olefin having 6 carbon atoms and more preferably 4-methyl-1-pentene from the viewpoint of easily obtaining a linear low density polyethylene resin having a density described later.
  • the content of these ⁇ -olefins in 100% by weight of the linear low density polyethylene resin is preferably 1% by weight or more and 20% by weight or less, particularly preferably 3% by weight or more and 10% by weight or less.
  • the ⁇ -olefin content is less than 1% by weight, the steam pressure range during molding tends to be narrow, and when it exceeds 20% by weight, the strength tends to decrease due to bending or compression.
  • the density of the linear low-density polyethylene resin used in the present invention is preferably 0.920 g / cm 3 or more and less than 0.940 g / cm 3 .
  • the density of the linear low density polyethylene resin is less than 0.920 g / cm 3 , the shrinkage of the polyethylene resin foamed molded product tends to increase, and when it is 0.940 g / cm 3 or more, the foamable temperature range is high. There is a tendency to narrow.
  • the density of the linear low density polyethylene resin in the present invention is preferably 0.920 g / cm 3 or more and less than 0.940 g / cm 3 , but the density of the polyethylene resin particles is 0.920 g / cm 3 or more. If the density is less than 0.940 g / cm 3, polyethylene resins having different densities may be mixed, and low-density polyethylene (LDPE) or high-density polyethylene (HDPE) is added to the linear low-density polyethylene resin. It can also be used by mixing. However, LDPE and / or HDPE can be mixed within a range in which the bubble diameter uniformity of the polyethylene resin expanded particles is not impaired. Specifically, in 100% by weight of the polyethylene resin particles, LDPE and / or HDPE. The content of is preferably 10% by weight or less, and more preferably 5% by weight or less.
  • the melt flow rate (MFR) of the linear low density polyethylene resin used in the present invention is preferably 0.1 g / 10 min or more and 5.0 g / 10 min or less, and 1.0 g / 10 min or more 3 More preferably, it is 0.0 g / 10 min or less. If the MFR of the linear low-density polyethylene resin is less than 0.1 g / 10 minutes, the expansion ratio of the obtained expanded particles tends to be too low, and if it exceeds 5.0 g / 10 minutes, the resulting expanded particles are formed. There is a tendency for the bubbles to be formed to be easily connected.
  • the MFR of the linear low-density polyethylene resin is a value measured under conditions of a temperature of 190 ° C. and a load of 2.16 kgf.
  • the molecular weight distribution (Mw / Mn) measured using a gel permeation chromatograph (hereinafter sometimes referred to as “GPC”) of a linear low density polyethylene resin is adjusted.
  • GPC gel permeation chromatograph
  • the molecular weight distribution (Mw / Mn) measured using the gel permeation chromatograph (GPC) of the linear low density polyethylene resin used in the present invention is preferably 3 or more and less than 5, and preferably 3 or more and 4 or less. Is more preferable.
  • Mw / Mn of the linear low-density polyethylene resin is less than 3, the moldable temperature range tends to be narrowed, and when the Mw / Mn is 5 or more, the dimensional shrinkage ratio of the molded product against the mold increases. There is a tendency that the beauty of the surface of the molded body is inferior.
  • the molecular weight distribution (Mw / Mn) is a value obtained by dividing Mw by Mn in polystyrene-equivalent weight average molecular weight Mw and number average molecular weight Mn obtained by gel permeation chromatography (GPC) measurement. .
  • a linear low-density polyethylene resin having a specific density, MFR and molecular weight distribution which is a copolymer of ethylene and an ⁇ -olefin having 6 and / or 8 carbon atoms as described above, is commercially available. Is possible.
  • Japanese Patent Application Laid-Open No. 2001-219517 describes Ultzex 2022L and 3520L, and these are copolymers of ethylene and an ⁇ -olefin having 6 carbon atoms. It is clear from Prime Polymer Co., Ltd./Product Catalog (issued in October 2010).
  • JP-A-9-095545, WO00 / 078828, JP-A-2006-307139, JP-A-2009-197226 and the like describe polymerization methods including catalyst technology for various linear low-density polyethylene resins. Based on these information, it is possible to obtain a prototype other than a commercial product by inquiring a polyethylene resin manufacturer.
  • the base resin in the present invention it is preferable to use a base resin containing 0.01 to 10 parts by weight of a hydrophilic compound with respect to 100 parts by weight of a linear low density polyethylene resin.
  • the hydrophilic compound is a compound containing a hydrophilic group such as a carboxyl group, a hydroxyl group, an amino group, an amide group, an ester group, a sulfo group, or a polyoxyethylene group in the molecule or a derivative thereof.
  • a hydrophilic group such as a carboxyl group, a hydroxyl group, an amino group, an amide group, an ester group, a sulfo group, or a polyoxyethylene group in the molecule or a derivative thereof.
  • examples of the compound containing a carboxyl group include lauric acid and sodium laurate
  • examples of the compound containing a hydroxyl group include ethylene glycol and glycerin.
  • Other hydrophilic organic compounds include organic compounds having a triazine ring such as melamine (chemical name: 1,3,5-triazine-2,4,6-triamine), isocyanuric acid, and isocyanuric acid condensate. Can be mentioned
  • the hydrophilic polymer is a polymer having a water absorption rate of 0.5% by weight or more measured in accordance with ASTM D570, so-called a hygroscopic polymer; from several times its own weight without being dissolved in water. It includes a water-absorbing polymer that absorbs water several hundred times and is difficult to dehydrate even under pressure; and a water-soluble polymer that dissolves in water at room temperature to high temperature.
  • hydrophilic polymer used in the present invention for example, Neutralize carboxylic acid groups of ethylene-acrylic acid-maleic anhydride terpolymer and ethylene- (meth) acrylic acid copolymer with alkali metal ions such as sodium ion and potassium ion and transition metal ions such as zinc ion An ionomer resin in which the molecules are cross-linked; Carboxyl group-containing polymers such as ethylene- (meth) acrylic acid copolymers; Polyamides such as nylon-6, nylon-6,6, copolymer nylon; Nonionic water-absorbing polymers such as polyethylene glycol; Polyether-polyolefin resin block copolymer represented by perestat (trade name, manufactured by Sanyo Kasei Co., Ltd.); Cross-linked polyethylene oxide polymers represented by Aqua Coke (trade name, manufactured by Sumitomo Seika Co., Ltd.) and the like. These may be used alone or in combination of two or more.
  • hydrophilic polymers hydrophilic monomers, nonionic water-absorbing polymers, and polyether-polyolefin resin block copolymers have relatively good dispersion stability in a pressure resistant container, and a relatively small amount. Addition is preferable because it exhibits water absorption. Furthermore, glycerin, polyethylene glycol, and melamine are preferable because the effects of the present invention are great.
  • the polyethylene resin particles of the present invention contain a cell nucleating agent (talc, calcium carbonate, zinc borate, kaolin, silica, etc.), an antioxidant, an antistatic agent, a colorant, a flame retardant and the like. It can be included.
  • a cell nucleating agent talc, calcium carbonate, zinc borate, kaolin, silica, etc.
  • an antioxidant an antistatic agent, a colorant, a flame retardant and the like. It can be included.
  • the polyethylene resin particles used in the present invention can be produced as follows.
  • a linear low density polyethylene resin is mixed with the hydrophilic compound and other additives by a mixing method such as a dry blend method or a master batch method.
  • the obtained mixture is melt-kneaded using an extruder, kneader, Banbury mixer (registered trademark), roll or the like, and the weight of one grain is preferably 0.2 to 10 mg, more preferably 0.5 to 6 mg.
  • the liquid hydrophilic compound may be directly added to the extruder and melt-kneaded.
  • the polyethylene resin expanded particles in the present invention can be produced as follows. For example, polyethylene resin particles are introduced into a pressure vessel together with water, a foaming agent, and a dispersant, and the pressure vessel is maintained at a predetermined temperature and pressure, and then the polyethylene resin particles are placed in a low-pressure atmosphere from the pressure vessel. It can be released and manufactured.
  • the foaming process may be referred to as “one-stage foaming”.
  • the polyethylene resin expanded particles obtained by single-stage expansion may be referred to as “single-stage expanded particles”.
  • the pressure vessel used in the present invention is not particularly limited as long as it can withstand the pressure in the vessel and the temperature in the vessel at the time of producing the polyethylene resin expanded particles, and examples thereof include an autoclave type pressure vessel.
  • the polyethylene-based resin expanded particles of the present invention in order to improve the dispersibility of the polyethylene-based resin particles in water, 100 parts by weight or more and 500 parts by weight of water with respect to 100 parts by weight of the polyethylene-based resin particles. It is preferable to use up to parts by weight.
  • the dispersant used in the present invention it is preferable to use a poorly water-soluble inorganic compound.
  • the poorly water-soluble inorganic compound refers to an inorganic compound having a water solubility at 25 ° C. of less than 1% by weight.
  • Specific examples of the hardly water-soluble inorganic compound include, for example, Alkaline earth metal salts such as calcium carbonate, barium carbonate, tricalcium phosphate, dicalcium phosphate, tribasic magnesium phosphate, tertiary barium phosphate, barium sulfate, calcium pyrophosphate; aluminosilicates such as kaolin and clay; Can be mentioned. These may be used alone or in combination of two or more.
  • the amount of the dispersant used in the present invention varies depending on the type and the type and amount of the polyethylene resin particles to be used, and cannot be generally specified, but is 0.2 to 5 parts by weight with respect to 100 parts by weight of the polyethylene resin particles.
  • the amount is preferably not more than parts by weight, more preferably not less than 0.2 parts by weight and not more than 3.0 parts by weight.
  • a dispersion aid may be used in combination with the dispersant.
  • a surfactant is preferably used, and an anionic surfactant, a nonionic surfactant, an amphoteric surfactant, an anionic polymer surfactant, and a nonionic polymer.
  • Surfactants such as surfactants are listed.
  • the anionic surfactant include sodium dodecylbenzene sulfonate, sodium n-paraffin sulfonate, sodium ⁇ -olefin sulfonate, sodium alkyldiphenyl ether sulfonate, and the like.
  • nonionic surfactants include polyoxyethylene alkyl ethers and polyoxyethylene sorbitan fatty acid esters.
  • amphoteric surfactants include alkyl betaines and alkyl amine oxides.
  • anionic polymer surfactant include polyacrylate, polystyrene sulfonate, maleic acid ⁇ -olefin copolymer salt and the like.
  • nonionic polymer surfactants include polyvinyl alcohol. These may be used alone or in combination of two or more.
  • the preferred dispersion aid type in the present invention varies depending on the type of dispersant used, it cannot be defined unconditionally.
  • an anionic surfactant is used. Is preferable because the dispersion state becomes stable.
  • the amount of the dispersion aid used in the present invention varies depending on the type and the type and amount of the polyethylene resin particles to be used, and cannot be generally defined, but is usually 0.001 weight per 100 parts by weight of water. It is preferable that the amount is not less than 0.2 parts by weight.
  • blowing agent used in the present invention examples include readily volatile hydrocarbons such as butane, pentane, and chlorofluorocarbon; inorganic gases such as nitrogen, carbon dioxide, and air; and water.
  • inorganic gases such as nitrogen, carbon dioxide, and air
  • water it is preferable to use an inorganic gas, and more preferable to use a foaming agent containing carbon dioxide gas, from the viewpoint of obtaining a polyethylene resin foamed molded article having a wide vapor pressure range during molding and a beautiful surface.
  • Polyethylene resin foam particles having a specific average cell diameter and open cell ratio which will be described later, using a foaming agent containing carbon dioxide gas, have a wide vapor pressure range at the time of molding, and have a beautiful surface. Therefore, the effect of the present invention is more manifested.
  • the amount of foaming agent used in the present invention varies depending on the type of polyethylene resin particles used, the type of foaming agent, the target foaming ratio, etc., and cannot be specified unconditionally, but with respect to 100 parts by weight of polyethylene resin particles.
  • the amount is preferably 2 parts by weight or more and 60 parts by weight or less.
  • the aqueous dispersion containing the polyethylene resin particles prepared in the pressure vessel as described above is pressurized to a predetermined pressure with stirring and heated to a predetermined temperature for a certain period of time. (Normally 5 to 180 minutes, preferably 10 to 60 minutes). Thereafter, the pressurized aqueous dispersion containing polyethylene resin particles is released into a low-pressure atmosphere (usually atmospheric pressure) by opening a valve provided at the lower part of the pressure-resistant container. Resin foam particles are produced.
  • the atmospheric temperature at which the aqueous dispersion is released is usually room temperature.
  • a heating medium such as water vapor to heat the atmosphere to 60 to 120 ° C., preferably 80 to 110 ° C.
  • the predetermined temperature for heating the inside of the pressure vessel in the present invention (hereinafter sometimes referred to as “foaming temperature”) varies depending on the melting point [Tm (° C.)], type, etc. of the polyethylene-based resin particles used. Although it cannot be specified, it is preferable to heat to a temperature higher than the softening temperature of the polyethylene resin particles, and it is more preferable to heat to Tm ⁇ 30 (° C.) or higher and Tm + 10 (° C.) or lower.
  • the melting point of the polyethylene resin particles means that the polyethylene resin particles are heated from 10 ° C. to 190 ° C. at a heating rate of 10 ° C./min using a differential scanning calorimeter DSC. After melting the resin particles, the temperature was decreased from 190 ° C. to 10 ° C. at a temperature decrease rate of 10 ° C./min and crystallized, and then the temperature was further increased from 10 ° C. to 190 ° C. at a temperature increase rate of 10 ° C./min. It is a value obtained from the DSC curve obtained at this time as the melting peak temperature at the second temperature increase.
  • the polyethylene resin expanded particles (single-stage expanded particles) obtained by single-stage expansion may be used as they are for in-mold foam molding, or may be expanded again and polyethylene having the desired expansion ratio. After the resin-based resin foamed particles, they may be used for in-mold foam molding.
  • the step of further foaming the first-stage expanded particles may be referred to as “two-stage expansion”.
  • polyethylene resin foam particles obtained by two-stage foaming may be referred to as “two-stage foamed particles”.
  • the two-stage foaming in the present invention a known method can be adopted, for example, as follows. Put the polyethylene resin foam particles in a pressurized tank, pressurize with an inorganic gas of a predetermined pressure, introduce the inorganic gas into the polyethylene resin foam particles, and leave it for a certain time, the internal pressure of the foam particles is atmospheric pressure After further increase, the polyethylene resin expanded particles are preferably heated with steam (water vapor) of 0.01 MPa-G or more and 0.15 MPa-G or less, more preferably 0.02 MPa-G or more and 0.10 MPa-G or less. To make two-stage foaming.
  • steam water vapor
  • the internal pressure of the polyethylene resin expanded particles is preferably adjusted to 0.05 to 0.70 MPa-G, preferably 0.10 to 0.50 MPa-G.
  • the expansion ratio tends not to increase so much, and when it exceeds 0.70 MPa-G, the bubbles constituting the polyethylene resin expanded particles are continuously formed by two-stage expansion. It becomes easy to form bubbles, and when the foamed particles are filled in a mold and subjected to in-mold foam molding, the resulting polyethylene-based resin foam molded article may shrink.
  • G in the unit of pressure MPa-G indicates a gauge pressure.
  • the inorganic gas used in the two-stage foaming in the present invention is not particularly limited, and examples thereof include air, nitrogen, carbon dioxide gas, etc. Air is preferable from the viewpoint of safety and environmental compatibility.
  • the expansion ratio of the polyethylene resin expanded particles in the present invention is not particularly limited, but the effect of the present invention is remarkable in that the shrinkage after molding is small (that is, the shrinkage ratio against the mold is small) even at a high expansion ratio. From the above, it is preferable that the expansion ratio of the polyethylene-based resin foam particles to be molded is 15 times or more and 30 times or less. When the expansion ratio of the polyethylene resin foam particles to be used for molding is less than 15 times, it is possible to obtain a foamed molded article having a small mold shrinkage rate without depending on the present invention when evaluated only from the viewpoint of shrinkage after molding. However, the effect of the present invention becomes remarkable at 15 times or more. When the expansion ratio exceeds 30 times, the mechanical strength of the foamed molded product tends to decrease.
  • the average cell diameter of the polyethylene resin expanded particles of the present invention is preferably 200 ⁇ m or more and 700 ⁇ m or less, and more preferably 300 ⁇ m or more and 600 ⁇ m or less.
  • the average cell diameter of the polyethylene resin foamed particles is less than 200 ⁇ m, the vapor pressure width during molding tends to be narrow, and the shrinkage of the resulting polyethylene resin foam molded product tends to increase.
  • the average cell diameter exceeds 700 ⁇ m, the cells are liable to form a continuous bubble, and the appearance of the resulting polyethylene-based resin foam molded article tends to deteriorate.
  • the vapor pressure width during molding tends to be wider, which is a more preferable embodiment.
  • Such polyethylene foamed resin particles having an average cell diameter of 300 ⁇ m or more and 600 ⁇ m or less tend to be difficult to obtain by the above-mentioned one-stage foaming, but can be easily obtained by carrying out two-stage foaming.
  • the ratio of the bubbles whose average cell diameter is within ⁇ 15% is preferably 80% or more of the entire expanded particles, and 90% or more. It is more preferable that When the ratio of the bubbles whose average bubble diameter is within ⁇ 15% is 80% or more of the entire foamed particles, the molded product obtained from the foamed particles has a uniform color and is beautiful.
  • the ratio of the bubbles whose bubble diameter is within an average bubble diameter of ⁇ 15% is related to the total bubbles in the region of 3000 ⁇ m ⁇ 3000 ⁇ m near the center of the expanded particle cross section when the expanded particle cross section is observed with an optical microscope.
  • the number of bubbles whose average bubble diameter is within ⁇ 15% is measured and divided by the total number of bubbles.
  • the bubble diameter is measured by the following method. A straight line having the maximum length d 1 in the bubble is drawn, a distance d 2 between the contact points of the perpendicular bisector of the straight line and the bubble is obtained, and an average value of d 1 and d 2 is defined as the bubble diameter.
  • a bubble that does not contain the entire bubble in the region for example, a bubble that is contained in the region by half of the bubble is excluded from the measurement.
  • the foamed polyethylene resin particles of the present invention have a uniform cell diameter, the foamability at the time of molding becomes uniform, and the surface beauty of the resulting foamed molded article is excellent.
  • the bubble diameter in the polyethylene resin expanded particles is non-uniform, there is a tendency that voids are conspicuous because the expanded properties differ between the expanded particles even under the same molding conditions.
  • the linear low-density polyethylene resin is a copolymer of ethylene and an ⁇ -olefin having 6 and / or 8 carbon atoms;
  • the density is 0.920 g / cm 3 or more and less than 0.940 g / cm 3 ;
  • the melt flow rate (MFR) is 0.1 to 5.0 g / 10 min.
  • MFR molecular weight distribution
  • GPC gel permeation chromatograph
  • the aforementioned hydrophilic compound in the aforementioned amount. More preferably, at least one selected from the group consisting of glycerin, polyethylene glycol and melamine is contained in an amount of 0.1 part by weight or more and 2 parts by weight or less based on 100 parts by weight of the linear low density polyethylene resin. It is particularly preferable to contain 0.1 to 2 parts by weight of polyethylene glycol.
  • the open cell ratio of the polyethylene resin expanded particles in the present invention is preferably 12% or less, more preferably 10% or less, and particularly preferably 6% or less.
  • the open cell ratio exceeds 12%, shrinkage occurs when in-mold foam molding is performed, and the surface beauty and compressive strength of the polyethylene-based resin in-mold foam molding tend to decrease.
  • the average cell diameter is preferably 200 ⁇ m or more and 700 ⁇ m or less, and the open cell rate is preferably 12% or less.
  • the method using water as a foaming agent cannot achieve both an average cell diameter and an open cell ratio.
  • carbon dioxide gas is used as the foaming agent, both the average cell diameter and the open cell ratio can be achieved, but there is a problem that the range of vapor pressure that can be molded when performing in-mold foam molding is narrow.
  • the present invention uses a linear low-density polyethylene resin that is a copolymer of ethylene and an ⁇ -olefin having 6 and / or 8 carbon atoms, so that an average cell diameter and an open cell ratio are obtained. As a result, the inventors have found that the range of vapor pressures that can be molded also increases.
  • linear low density polyethylene resin, polyethylene resin expanded particles, and polyethylene resin expanded particles used in the present invention are all non-crosslinked.
  • “non-crosslinked” specifically refers to those having a gel fraction insoluble in hot xylene of 3.0% by weight or less.
  • the gel fraction is a weight ratio of the gel component amount measured by the following method to the original resin weight. That is, 0.5 g of linear low density polyethylene resin, polyethylene resin expanded particles, or polyethylene resin expanded particles are put in a 200 mesh wire mesh bag, and the resin or particles do not come out of the bag. Fold the end of the wire mesh so that.
  • the wire mesh bag is immersed in 50 ml of xylene boiled under atmospheric pressure for 3 hours, and then cooled and taken out from xylene three times in total.
  • the wire mesh bag taken out is dried overnight at room temperature, then dried in an oven at 150 ° C. for 1 hour, and then naturally cooled to room temperature.
  • the weight of the component remaining in the wire mesh bag after cooling is measured to obtain the gel component weight.
  • the polyethylene resin foamed particles of the present invention are non-crosslinked, a polyethylene resin foamed molded article having a wide vapor pressure range during molding and a beautiful surface can be obtained.
  • the cross-linked polyethylene-based resin expanded particles the vapor pressure width at the time of molding tends to be narrow, and the surface property of the polyethylene-based resin expanded molded body also tends to be lowered.
  • the foamed polyethylene resin particles obtained as described above are filled in a mold having a predetermined shape and heated with steam or the like, so that the foamed particles are fused together, so-called in-mold foaming.
  • a polyethylene resin foam molded article can be obtained.
  • an in-mold foam molding method for example, B) Pressurizing the polyethylene resin expanded particles with an inorganic gas (for example, air, nitrogen, carbon dioxide, etc.) to impregnate the polyethylene resin expanded particles with an inorganic gas to give a predetermined internal pressure, Filling and heat-sealing with steam, B) A method in which polyethylene resin foam particles are compressed by gas pressure and filled in a mold, and heat recovery is performed with water vapor using the recovery force of the polyethylene resin foam particles. C) A method in which polyethylene resin foamed particles are filled in a mold without any pretreatment and heat-sealed with water vapor. Such a method can be used.
  • an inorganic gas for example, air, nitrogen, carbon dioxide, etc.
  • the polyethylene resin expanded particles are then provided.
  • the method include molding by time, fusing the polyethylene resin pre-expanded particles together, cooling the mold by water cooling, then opening the mold, and obtaining a polyethylene resin in-mold foam molding.
  • the thus obtained polyethylene-based resin foam molded article has a small mold dimensional shrinkage, little deformation, and good surface elongation.
  • the dimensional shrinkage ratio of the polyethylene-based resin foam molded body in the present invention differs depending on the resin used, the foaming ratio of the foamed particles, the vapor pressure during molding, and the shape of the mold, it cannot be specified unconditionally.
  • polyethylene-based resin expanded particles having an expansion ratio of 20 times or more approximately 2 to 4% is preferable.
  • the steam pressure at the time of molding increases, and the expansion force (foaming force) of the expanded particles increases, so that the dimensional shrinkage against the mold generally decreases.
  • the vapor pressure becomes too high, the foamed particles shrink due to heat, so that the shrinkage ratio against the mold tends to increase.
  • the dimensional shrinkage ratio of the mold tends to increase.
  • the deformation of the polyethylene-based resin foam molded body in the present invention is influenced by the resin used, the expansion ratio of the expanded particles, the vapor pressure at the time of molding, and the shape of the mold.
  • the lower the expansion ratio of the expanded particles used for in-mold foam molding the higher the strength, and the easier it is to maintain the shape of the mold.
  • the lower the vapor pressure during molding the less deformation after molding and the easier it is to return to the shape of the mold upon drying.
  • the higher the steam pressure the larger the deformation, and there is a tendency that the deformation does not return even after the drying process.
  • the surface elongation of the polyethylene resin foam molded article in the present invention is preferably in a state where there are no voids between the foamed particles because the surface of the foam molded article is beautiful.
  • the foaming force of the foamed particles is weak and many voids are generated.
  • voids may also occur when the vapor pressure is too high.
  • the range of the vapor pressure in the main heating step in which a good molded body is obtained is defined as “appropriate vapor pressure width”.
  • the vapor pressure in the main heating step is lower than the lower limit value of the appropriate vapor pressure width, there is a problem that the inside of the obtained molded body is not fused, the surface is poorly stretched, and voids are conspicuous.
  • the steam pressure in this heating process is higher than the upper limit of the appropriate steam pressure width, there is a problem that deformation after molding is large, deformation does not return after drying, and the dimensional shrinkage ratio against the mold is large.
  • the vapor pressure is too high, the molded body shrinks and a usable molded body may not be obtained.
  • melt flow rate (MFR) of the polyethylene resin was measured using an MI measuring instrument described in JIS K7210, with an orifice of 2.0959 ⁇ 0.005 mm ⁇ , an orifice length of 8.000 ⁇ 0.025 mm, a load of 2160 g, and 190 ⁇ 0.2. Measured under the condition of ° C.
  • Mw / Mn The molecular weight distribution (Mw / Mn) by GPC of the polyethylene resin was measured under the following conditions.
  • Measuring instrument Alliance GPC2000 type column manufactured by Waters: TSKgel GMH6-HT 2 TSKgel GMH6-HTL 2 [each inner diameter 7.5 mm ⁇ length 300 mm; manufactured by Tosoh Corporation]
  • Mobile phase o-dichlorobenzene for high performance liquid chromatography (containing 0.025% BHT)
  • Flow rate 1.0 mL / min
  • ⁇ Gel fraction> In a 200 mesh wire mesh bag, 0.5 g of linear low density polyethylene resin, polyethylene resin expanded particles, or polyethylene resin expanded particles are put so that the resin or particles do not come out of the bag. Fold the end of the wire mesh.
  • the wire mesh bag is immersed in 50 ml of xylene boiled under atmospheric pressure for 3 hours, and then cooled and taken out from xylene three times in total.
  • the wire mesh bag taken out is dried overnight at room temperature, then dried in an oven at 150 ° C. for 1 hour, and then naturally cooled to room temperature. The weight of the component remaining in the wire mesh bag after cooling is measured to obtain the gel component weight.
  • gel fraction of the polyethylene-type resin expanded particle of an Example and a comparative example description was 1.0 weight% or less, and was a non-crosslinked polyethylene-based resin expanded particle.
  • ⁇ Bubble diameter uniformity> When the cross section of the expanded particle was observed with an optical microscope [manufactured by KEYENCE, microscope VHX-100], the bubble diameter was measured for all the bubbles in the region of 3000 ⁇ m ⁇ 3000 ⁇ m near the center of the expanded particle cross section, and the average cell The ratio of bubbles within a diameter of ⁇ 15% was determined, and the bubble diameter uniformity (bubble diameter variation) was evaluated according to the following criteria.
  • the bubble diameter is measured by the following method. A straight line having the maximum length d 1 in the bubble was drawn, the distance d 2 between the contact points of the perpendicular bisector of the straight line and the bubble was determined, and the average value of d 1 and d 2 was taken as the bubble diameter.
  • ⁇ The ratio of the bubbles whose bubble diameter is within the average bubble diameter ⁇ 15% is 90% or more of the whole.
  • X The proportion of the bubbles whose bubble diameter is within ⁇ 15% of the average bubble diameter is less than 80% of the total.
  • ⁇ Vapor pressure range during molding and proper steam pressure> After the moisture of the obtained polyethylene-based resin expanded particles was blown, the mold was filled in a mold having a molding space of length 400 ⁇ width 300 ⁇ thickness 50 mm, and the inside of the mold chamber was heated with steam for 10 seconds. Thereafter, the exhaust valve was closed and heated with steam for 10 seconds (hereinafter referred to as “main heating step”), thereby fusing the expanded particles. Subsequently, the vapor in the mold was evacuated, the inside of the mold and the surface of the molded body were water-cooled, and then the molded body was taken out to obtain a polyethylene resin foam molded body.
  • Molding was performed by changing the set steam pressure in this heating step by 0.01 MPa within a range of 0.08 to 0.15 MPa-G.
  • the holding time at the set pressure was 4 seconds.
  • ⁇ or ⁇ level was defined as “appropriate steam pressure range”.
  • the most balanced steam pressure was determined as “optimum steam pressure” in terms of fusion property, mold dimensional shrinkage, and surface aesthetics.
  • the vapor pressure width at the time of molding was evaluated according to the following criteria.
  • ⁇ The proper steam pressure width is 0.03 MPa or more.
  • ⁇ The proper steam pressure width is 0.02 MPa or more and less than 0.03 MPa.
  • X The proper steam pressure width is less than 0.02 MPa.
  • the fusion rate is 60% or more and less than 80%.
  • X The fusion rate is less than 60%.
  • Example 1 [Preparation of polyethylene resin particles]
  • 4MP 4-methyl-1-pentene as a copolymerized ⁇ -olefin
  • the dry blended mixture is put into a 50 mm ⁇ twin screw extruder, melt kneaded at a resin temperature of 220 ° C., extruded into a strand through a circular die attached to the tip of the extruder, water cooled, and then cut with a cutter.
  • Polyethylene resin particles having a weight of 4.5 mg / grain were obtained.
  • the set steam pressure in this heating process is changed within a range of 0.08 to 0.15MPa-G by 0.01MPa and molding is performed. Evaluated. Here, out of the heating time of 10 seconds in the main heating step, the holding time at the set pressure was 4 seconds. Table 1 shows the evaluation results regarding the obtained polyethylene resin-in-mold foam. In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G).
  • the present invention relates to a foam in a polyethylene resin mold.
  • Example 2 Polyethylene resin particles were obtained by the same operation as in Example 1.
  • Example 3 Single-stage expanded particles were obtained by the same operation as in Example 1 except that the foaming temperature was changed to 123.0 ° C. with respect to the obtained polyethylene resin. After the water of the obtained first-stage expanded particles was blown, it was placed in a pressure vessel and pressurized with air to impregnate the first-stage expanded particles with air, and an internal pressure of 0.24 MPa-G was applied.
  • the present invention relates to a foam in a polyethylene resin mold.
  • the present invention relates to a foam in a polyethylene resin mold.
  • Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam.
  • the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G).
  • the present invention relates to a foam in a polyethylene resin mold.
  • Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam.
  • the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G).
  • the present invention relates to a foam in a polyethylene resin mold.
  • Example 7 In [Production of polyethylene-based resin expanded particles], the same operation as in Example 2 was carried out under the conditions described in Table 1 except that the hydrophilic compound was not used. A resin foam molding was obtained. Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam. In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
  • Example 8 In [Preparation of polyethylene resin expanded particles], the types and amounts of the hydrophilic compounds are respectively 0.5 parts by weight of polyethylene glycol [manufactured by Lion Corporation, PEG300], melamine [manufactured by Nissan Chemical Industries, Ltd.] 0 Except for the change to 2 parts by weight, the same operations as in Example 2 were performed under the conditions described in Table 1, and single-stage expanded particles, double-stage expanded particles, and a polyethylene-based resin foam molded article were obtained. Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam.
  • the present invention relates to a foam in a polyethylene resin mold.
  • Example 10 Preparation of polyethylene resin particles
  • talc manufactured by Hayashi Kasei Co., Ltd., Talcan powder PK-S
  • monoglyceride as an antistatic agent
  • Riken Vitamin Co., Ltd. Riquemar S-100A
  • dry blending 1.0 part by weight, the same operation as in Example 1 was performed to obtain 1.3 mg / grain of polyethylene resin particles.
  • Example 2 In [Production of polyethylene-based resin foamed particles] and [Production of polyethylene-based resin-in-mold foam], the same operation as in Example 2 was performed to obtain one-stage foamed particles, two-stage foamed particles, and a polyethylene-based resin foam molded article. Obtained.
  • Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam.
  • the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G).
  • the present invention relates to a foam in a polyethylene resin mold.
  • Example 11 In [Preparation of polyethylene resin foamed particles], 0.1 part by weight of talc [manufactured by Hayashi Kasei Co., Ltd., Talcan Powder PK-S] is further added to 100 parts by weight of the linear low density polyethylene resin.
  • Example 1 except that 0.5 parts by weight of a monoglyceride [manufactured by Riken Vitamin Co., Ltd., Riquemar S-100A] as an inhibitor and 1.0 part by weight of carbon black [manufactured by CABOT, N330] as a colorant were dry blended. The same operation was performed to obtain one-stage expanded particles, two-stage expanded particles, and a polyethylene resin foam molded article.
  • Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam.
  • the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G).
  • the present invention relates to a foam in a polyethylene resin mold.
  • Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam.
  • the molded body evaluations (fusing property, mold dimensional stability, surface aesthetics) in the table were obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.12 MPa-G).
  • the present invention relates to a foam in a polyethylene resin mold.
  • Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam.
  • the molded body evaluations (fusing property, mold dimensional stability, surface aesthetics) in the table were obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.12 MPa-G).
  • the present invention relates to a foam in a polyethylene resin mold.
  • Example 14 [Preparation of polyethylene resin particles] Polyethylene resin particles were obtained by the same operation as in Example 1. [Preparation of expanded polyethylene resin particles] After adding 25 parts by weight of isobutane as a foaming agent to the obtained polyethylene-based resin particles and heating to a foaming temperature of 119.0 ° C., isobutane was additionally injected, and the internal pressure of the autoclave was 1.6 MPa-G. Single-stage expanded particles were obtained in the same manner as in Example 1 except that the pressure was increased to the expansion pressure.
  • the present invention relates to a foam in a polyethylene resin mold.
  • the present invention relates to a foam in a polyethylene resin mold.
  • Table 2 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene resin-in-mold foam.
  • the molded body evaluations in the table were obtained by in-mold foam molding at an optimum vapor pressure (vapor pressure of 0.10 MPa-G).
  • the present invention relates to a foam in a polyethylene resin mold.
  • Single-stage expanded particles, double-stage expanded particles and a polyethylene-based resin foam molded article were obtained.
  • Table 2 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene resin-in-mold foam.
  • the molded body evaluations (fusing property, dimensional stability against mold, and surface aesthetics) in the table were obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.13 MPa-G).
  • the present invention relates to a foam in a polyethylene resin mold.
  • the molded body evaluations (fusing property, dimensional stability against mold, and surface aesthetics) in the table were obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.13 MPa-G).
  • the present invention relates to a foam in a polyethylene resin mold.
  • the resulting single-stage expanded particles were two-stage expanded under the conditions shown in Table 2, but the foamed particles were broken to increase the open-cell ratio, resulting in two-stage expanded particles with a reduced expansion ratio. Molding was stopped.
  • Table 2 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene resin-in-mold foam.
  • the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G).
  • the present invention relates to a foam in a polyethylene resin mold.
  • Example 9 [Preparation of polyethylene resin particles] The same operation as in Example 7 was performed to obtain polyethylene resin particles containing no hydrophilic compound. [Preparation of expanded polyethylene resin particles] In a pressure resistant autoclave having a capacity of 0.3 m 3 , 100 parts by weight (75 kg) of the obtained polyethylene resin particles, 250 parts by weight of water, and tribasic calcium phosphate as a sparingly water-soluble inorganic compound [made by Taihei Chemical Industry Co., Ltd.] 4.0 After charging 0.8 parts by weight of sodium alkyl sulfonate [La Kamul PS, manufactured by Kao Corporation] as a surfactant, nitrogen gas was injected under pressure to 1.5 MPa-G with stirring.
  • sodium alkyl sulfonate La Kamul PS, manufactured by Kao Corporation
  • the autoclave contents were heated and heated to a foaming temperature of 125.0 ° C.
  • the internal pressure of the autoclave was 2.2 MPa-G.
  • nitrogen gas was additionally injected to increase the internal pressure of the autoclave to a foaming pressure of 3.5 MPa-G.
  • bulb of the autoclave lower part was opened, the autoclave content was discharge
  • the resulting single-stage expanded particles were two-stage expanded under the conditions shown in Table 2, but the foamed particles were broken to increase the open-cell ratio, resulting in two-stage expanded particles with a reduced expansion ratio. Molding was stopped.
  • polyethylene resin foamed particles of the present invention a polyethylene resin foam molded article having a wide vapor pressure range, a small mold dimensional shrinkage ratio, and a beautiful surface can be easily obtained. Obtainable.
  • the obtained polyethylene-based resin foam molded article is used for various applications as a buffer packaging material, a heat insulating material, and the like.

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Abstract

By causing polyethylene resin particles, which use a linear low-density polyethylene resin as the base resin, to foam, said linear low-density polyethylene resin being a copolymer of ethylene and an alpha-olefin with 6 and/or 8 carbons, a density of 0.920 g/cm3 to less than 0.940 g/cm3, a melt flow rate (MFR) of 0.1 g/10 minutes to 5.0 g/10 minutes, and a molecular weight distribution (Mw/Mn) of 3 to less than 5, as measured by measured by gel permeation chromatography (GPC), polyethylene resin foam molded articles with beautiful surfaces and low shrinkage rates versus mold dimensions can be manufactured at a wide range of vapor pressures at which excellent molded articles can be obtained during molding, and polyethylene resin foamed particles, which have an average foam diameter of 200 μm to 700 μm, and an open cell rate of at least 12%, can be provided.

Description

ポリエチレン系樹脂発泡粒子及びその成形体Polyethylene resin expanded particles and molded articles thereof
　本発明は、ポリエチレン系樹脂発泡粒子および、ポリエチレン系樹脂発泡粒子からなるポリエチレン系樹脂発泡成形体に関する。 The present invention relates to polyethylene resin foamed particles and polyethylene resin foamed molded articles made of polyethylene resin foamed particles.
　ポリエチレン系樹脂発泡成形体（ポリエチレン系樹脂型内発泡体）は、柔軟性、断熱性に優れるため、緩衝包装材や断熱材として種々の用途に利用されている。ポリエチレン系樹脂発泡成形体の製造方法としては、ポリエチレン系樹脂粒子をブタンガス等の発泡剤にて予め発泡（ビーズ発泡）させた発泡粒子を、型内に充填し、水蒸気等の熱媒を導入して加熱融着させる型内発泡成形が知られている。
ビーズ発泡においては、発泡倍率が高く、耐熱性に優れる発泡体が容易に得られることから、架橋ポリエチレンが用いられてきたが、無架橋ポリエチレン系樹脂でも成形性の良い成形体を製造することが提案されている（特許文献１、２参照）。 Polyethylene-based resin foamed molded articles (polyethylene-based resin-in-mold foams) are excellent in flexibility and heat insulation properties, and are therefore used in various applications as buffer packaging materials and heat insulating materials. As a method for producing a polyethylene resin foamed molded product, foamed particles obtained by foaming polyethylene resin particles with a foaming agent such as butane gas in advance (bead foaming) are filled in a mold, and a heat medium such as water vapor is introduced. In-mold foam molding in which heat fusion is performed is known.
In bead foaming, since a foam having a high expansion ratio and excellent heat resistance can be easily obtained, crosslinked polyethylene has been used. However, it is possible to produce a molded article having good moldability even with a non-crosslinked polyethylene resin. It has been proposed (see Patent Documents 1 and 2).
　従来、当該分野で使用されている発泡剤としては、高発泡倍率の発泡粒子が得られることから、特許文献１～３のように揮発性有機発泡剤が使用されてきたが、環境適合性の観点からは、このような揮発性有機発泡剤は敬遠されつつある。
また、特許文献３には、重量平均分子量Ｍｗ／数平均分子量Ｍｎが３～７の１－ブテンを共重合した直鎖状低密度ポリエチレン予備発泡粒子が開示されているが、表面が平滑な成形体が得られるものの、成形可能な蒸気圧力の幅が狭いという問題があった。特許文献３に開示の技術に従った場合、炭素数６や８のコモノマーを共重合した場合であっても、同様の問題があった。 Conventionally, as foaming agents used in this field, volatile organic foaming agents have been used as described in Patent Documents 1 to 3 because foamed particles having a high foaming ratio can be obtained. From the point of view, such volatile organic blowing agents are being avoided.
Patent Document 3 discloses linear low-density polyethylene pre-expanded particles copolymerized with 1-butene having a weight average molecular weight Mw / number average molecular weight Mn of 3 to 7, and molding with a smooth surface. Although the body was obtained, there was a problem that the range of vapor pressure that could be molded was narrow. When the technique disclosed in Patent Document 3 is followed, similar problems occur even when a comonomer having 6 or 8 carbon atoms is copolymerized.
　発泡剤として水を用いる方法が特許文献４および５に開示されており、直鎖状低密度ポリエチレン系樹脂であるウルトゼックス２０２２Ｌを用いて発泡粒子を得ている。
ウルトゼックス２０２２Ｌは、密度０．９２０ｇ／ｃｍ3、メルトフローレート（以降、「ＭＦＲ」と称する場合がある。）２．０ｇ／１０分、分子量分布Ｍｗ／Ｍｎが３．８であるエチレンと炭素数６のα－オレフィンとの共重合体である。ただし、ウルトゼックス２０２２Ｌを基材樹脂とする樹脂粒子に対して発泡剤として水を用いた場合、得られるポリエチレン系樹脂発泡粒子の発泡倍率が低く、平均気泡径も小さくなる傾向があり、発泡倍率及び平均気泡径を増大させる為に二段発泡を行った場合、発泡粒子の気泡が破れて、連続気泡率が高くなる傾向がある。
ここで、ポリエチレン系樹脂発泡粒子の平均気泡径が小さすぎる場合、成形可能な蒸気圧力の幅が狭いという問題があり、連続気泡率が高い場合、型内発泡成形体の収縮が著しく、使用可能な成形体にはならないという問題が残される。 Methods using water as a foaming agent are disclosed in Patent Documents 4 and 5, and foamed particles are obtained by using Ultzex 2022L, which is a linear low density polyethylene resin.
Ultrazex 2022L has a density of 0.920 g / cm 3 , a melt flow rate (hereinafter sometimes referred to as “MFR”) of 2.0 g / 10 minutes, and a molecular weight distribution Mw / Mn of 3.8. It is a copolymer with an α-olefin of formula 6. However, when water is used as a foaming agent for the resin particles having the base resin as Ultzex 2022L, the resulting polyethylene-based resin foam particles tend to have a low expansion ratio and a small average cell diameter. When two-stage foaming is performed to increase the average cell diameter, the foamed particles tend to break and the open cell ratio tends to increase.
Here, when the average cell diameter of the polyethylene resin foamed particles is too small, there is a problem that the range of vapor pressure that can be molded is narrow, and when the open cell rate is high, the shrinkage of the in-mold foam molded product is remarkably usable. The problem remains that the molded body does not become a proper molded body.
　一方、前述のとおり、環境問題への関心の高まりもあり、近年では、発泡剤として炭酸ガスなどの無機ガスが使用されるようになってきた（特許文献６、７参照）。しかし、これらの方法でも、やはり使用する樹脂によっては成形可能な蒸気圧力の幅が狭い（特許文献６の成形可能な蒸気圧力の幅は０．２ｋｇ／ｃｍ2≒０．０２ＭＰａ）場合や、得られる発泡成形体の対金型寸法収縮率が大きい場合があるという問題があった。 On the other hand, as described above, there has been a growing interest in environmental problems, and in recent years, inorganic gases such as carbon dioxide have been used as foaming agents (see Patent Documents 6 and 7). However, even in these methods, depending on the resin to be used, the range of the vapor pressure that can be molded is narrow (the width of the vapor pressure that can be molded in Patent Document 6 is 0.2 kg / cm 2 ≈0.02 MPa). There is a problem that the shrinkage ratio of the foamed molded product to the mold may be large.
　また、前記問題を解決する為に、ポリエチレン系樹脂として、エチレン単位と炭素数３～２０のα－オレフィン単位からなる共重合体の混合物、すなわち、密度９００～９４０ｋｇ／ｍ3で、特定のメルトフローレート、重量平均分子量Ｍｗ／数平均分子量Ｍｎ、流動活性化エネルギーを有する共重合体と、密度９４１～９７０ｋｇ／ｍ3の共重合体との混合物を使用する方法も提案されている（特許文献８参照）。
しかしながら、該方法では、密度が大きく異なる樹脂を混合している為、発泡粒子の発泡倍率がばらついたり、発泡粒子内の気泡がばらついたり、場合によっては気泡膜が破れてしまうなどの問題があり、安定して成形しうる発泡粒子を得ることが困難であった。 In order to solve the above problem, a polyethylene resin is a mixture of an ethylene unit and an α-olefin unit having 3 to 20 carbon atoms, that is, a density of 900 to 940 kg / m 3 and a specific melt. A method of using a mixture of a copolymer having a flow rate, a weight average molecular weight Mw / number average molecular weight Mn, fluid activation energy and a copolymer having a density of 941 to 970 kg / m 3 has also been proposed (Patent Literature). 8).
However, in this method, since resins having greatly different densities are mixed, there is a problem that the expansion ratio of the expanded particles varies, the bubbles in the expanded particles vary, or the bubble film is broken in some cases. It was difficult to obtain foamed particles that could be stably molded.
特許第１６９６６５１号Japanese Patent No. 1696651 特許第２０１７４４９号Patent No. 2017449 特開昭６１－１８５５３６号JP-A 61-185536 特開平１０－２０４２０３号JP-A-10-204203 特開平１０－２３７２１１号JP-A-10-237211 特開２０００－１７０７９号JP 2000-17079 A 特開２０１０－５９３９３号JP 2010-59393 A 特開２０１０－１２６６４１号JP 2010-126641 A
　本発明は、成形時に良好な成形体が得られる蒸気圧力の幅が広く、成形後の対金型寸法収縮率が少なく、表面が美麗なポリエチレン系樹脂発泡成形体を製造することができる、ポリエチレン系樹脂発泡粒子を提供することにある。 The present invention provides a polyethylene resin foam molded article having a wide range of vapor pressure that can provide a good molded article at the time of molding, a small dimensional shrinkage ratio to the mold after molding, and a beautiful surface. It is in providing a resin-based expanded resin particle.
　本発明者は、上記課題を解決すべく鋭意研究を重ねた結果、特定の密度およびメルトフローレートを有し、かつ、Ｍｗ／Ｍｎが３以上５未満である直鎖状低密度ポリエチレン系樹脂から得られる発泡粒子を、型内発泡成形を行うことによって、例えば、成形用ガスの追加による発泡能付与を行わずとも、得られる無架橋ポリエチレン系樹脂発泡成形体の対金型寸法収縮率が小さく、表面が美麗な成形体が得られることを見出し、本発明の完成に至った。 As a result of intensive studies to solve the above problems, the present inventor has obtained a linear low-density polyethylene-based resin having a specific density and a melt flow rate and having an Mw / Mn of 3 or more and less than 5. By performing in-mold foam molding of the obtained foamed particles, for example, without imparting foaming ability by adding a molding gas, the resulting non-crosslinked polyethylene resin foam molded article has a small shrinkage ratio against the mold. The inventors have found that a molded article having a beautiful surface can be obtained, and have completed the present invention.
　すなわち、本発明は以下の構成よりなる。
［１］　次の（ａ）～（ｄ）の条件を満たす直鎖状低密度ポリエチレン系樹脂を基材樹脂とするポリエチレン系樹脂粒子を発泡させて得られるポリエチレン系樹脂発泡粒子であって、
平均気泡径が２００μｍ以上７００μｍ以下、かつ、連続気泡率が１２％以下であることを特徴とする、ポリエチレン系樹脂発泡粒子。
（ａ）直鎖状低密度ポリエチレン系樹脂がエチレンと、炭素数６および／または８のα－オレフィンとの共重合体である。
（ｂ）密度が０．９２０ｇ／ｃｍ3以上０．９４０ｇ／ｃｍ3未満である。
（ｃ）メルトフローレート（ＭＦＲ）が０．１ｇ／１０分以上５．０ｇ／１０分以下である。
（ｄ）ゲル・パーミエーション・クロマトグラフ（ＧＰＣ）により測定される分子量分布（Ｍｗ／Ｍｎ）が３以上５未満である。
［２］　平均気泡径が３００μｍ以上６００μｍ以下であることを特徴とする、［１］に記載のポリエチレン系樹脂発泡粒子。
［３］　気泡径が平均気泡径±１５％以内である気泡の占める割合が、発泡粒子全体に対して８０％以上であることを特徴とする、［１］または［２］記載のポリエチレン系樹脂発泡粒子。
［４］　基材樹脂が、直鎖状低密度ポリエチレン系樹脂１００重量部に対して、親水性化合物を０．０１重量部以上１０重量部以下含有することを特徴とする、［１］～［３］の何れか１項に記載のポリエチレン系樹脂発泡粒子。
［５］　親水性化合物が、グリセリン、ポリエチレングリコールおよびメラミンよりなる群から選ばれる少なくとも１種であることを特徴とする、［４］記載のポリエチレン系樹脂発泡粒子。
［６］　直鎖状低密度ポリエチレン系樹脂１００重量部に対して、グリセリン、ポリエチレングリコールおよびメラミンよりなる群から選ばれる少なくとも１種を０．１重量部以上２重量部以下含有することを特徴とする、［５］記載のポリエチレン系樹脂発泡粒子。
［７］　［１］～［６］の何れか１項記載のポリエチレン系樹脂発泡粒子を、金型内に充填した後、型内発泡成形して得られることを特徴とする、ポリエチレン系樹脂発泡成形体。
［８］　次の（ａ）～（ｄ）の条件を満たす直鎖状低密度ポリエチレン系樹脂を基材樹脂とするポリエチレン系樹脂粒子を、水、炭酸ガスを含む発泡剤、および分散剤と共に耐圧容器内に導入し、耐圧容器内を昇温、昇圧して保持した後、直鎖状低密度ポリエチレン系樹脂粒子を耐圧容器内より低圧雰囲気下に放出して一段発泡粒子を得る工程、
次いで、一段発泡粒子を加圧タンク内に入れ、無機ガスで加圧することにより一段発泡粒子内に空気を導入して、発泡粒子の内圧を大気圧より高めた後、一段発泡粒子を水蒸気で加熱して二段発泡粒子を得る工程、
を経ることを特徴とする、
平均気泡径が２００μｍ以上、７００μｍ以下、かつ、連続気泡率が１２％以下であるポリエチレン系樹脂発泡粒子の製造方法。
（ａ）直鎖状低密度ポリエチレン系樹脂がエチレンと、炭素数６および／または８のα－オレフィンとの共重合体である。
（ｂ）密度が０．９２０ｇ／ｃｍ3以上０．９４０ｇ／ｃｍ3未満である。
（ｃ）メルトフローレート（ＭＦＲ）が０．１ｇ／１０分以上５．０ｇ／１０分以下である。
（ｄ）ゲル・パーミエーション・クロマトグラフ（ＧＰＣ）により測定される分子量分布（Ｍｗ／Ｍｎ）が３以上５未満である。 That is, the present invention has the following configuration.
[1] Polyethylene resin foamed particles obtained by foaming polyethylene resin particles using a linear low density polyethylene resin satisfying the following conditions (a) to (d) as a base resin,
A polyethylene-based resin expanded particle having an average cell diameter of 200 μm or more and 700 μm or less and an open cell ratio of 12% or less.
(A) The linear low density polyethylene resin is a copolymer of ethylene and an α-olefin having 6 and / or 8 carbon atoms.
(B) The density is 0.920 g / cm 3 or more and less than 0.940 g / cm 3 .
(C) The melt flow rate (MFR) is 0.1 g / 10 min or more and 5.0 g / 10 min or less.
(D) The molecular weight distribution (Mw / Mn) measured by gel permeation chromatograph (GPC) is 3 or more and less than 5.
[2] The polyethylene resin expanded particles according to [1], wherein the average cell diameter is 300 μm or more and 600 μm or less.
[3] The polyethylene-based resin according to [1] or [2], wherein the ratio of air bubbles whose average cell diameter is within ± 15% is 80% or more with respect to the entire expanded particles Expanded particles.
[4] The base resin contains 0.01 to 10 parts by weight of a hydrophilic compound with respect to 100 parts by weight of the linear low-density polyethylene resin. [1] to [1] 3] The polyethylene resin expanded particles according to any one of [3].
[5] The polyethylene resin expanded particles according to [4], wherein the hydrophilic compound is at least one selected from the group consisting of glycerin, polyethylene glycol and melamine.
[6] It is characterized by containing 0.1 part by weight or more and 2 parts by weight or less of at least one selected from the group consisting of glycerin, polyethylene glycol and melamine with respect to 100 parts by weight of the linear low density polyethylene resin. The polyethylene resin expanded particles according to [5].
[7] Polyethylene resin foam obtained by filling the polyethylene resin foamed particles according to any one of [1] to [6] into a mold and then performing in-mold foam molding Molded body.
[8] Polyethylene resin particles having a linear low density polyethylene resin that satisfies the following conditions (a) to (d) as a base resin, together with a foaming agent containing water, carbon dioxide gas, and a dispersing agent. Introducing into the vessel, raising the pressure inside the pressure vessel, holding the pressure increased, and then releasing the linear low density polyethylene resin particles in a low pressure atmosphere from inside the pressure vessel to obtain one-stage expanded particles,
Next, the first-stage expanded particles are placed in a pressurized tank, and air is introduced into the first-stage expanded particles by pressurizing with an inorganic gas to increase the internal pressure of the expanded particles from atmospheric pressure, and then the first-stage expanded particles are heated with water vapor. To obtain two-stage expanded particles,
It is characterized by going through the
A method for producing expanded polyethylene resin particles having an average cell diameter of 200 μm or more and 700 μm or less and an open cell ratio of 12% or less.
(A) The linear low-density polyethylene-based resin is a copolymer of ethylene and an α-olefin having 6 and / or 8 carbon atoms.
(B) The density is 0.920 g / cm 3 or more and less than 0.940 g / cm 3 .
(C) The melt flow rate (MFR) is 0.1 g / 10 min or more and 5.0 g / 10 min or less.
(D) The molecular weight distribution (Mw / Mn) measured by gel permeation chromatograph (GPC) is 3 or more and less than 5.
　本発明のポリエチレン系樹脂発泡粒子によれば、成形時に良好な成形体が得られる蒸気圧力の幅が広く、対金型寸法収縮率が小さく、表面が美麗なポリエチレン系樹脂発泡成形体を簡便に得ることができる。 According to the polyethylene resin foamed particles of the present invention, it is easy to obtain a polyethylene resin foam molded article having a wide vapor pressure range, a small mold dimensional shrinkage, and a beautiful surface. Obtainable.
　本発明のポリエチレン系樹脂発泡粒子は、次の（ａ）～（ｄ）の条件を満たす直鎖状低密度ポリエチレン系樹脂を基材樹脂とするポリエチレン系樹脂粒子を発泡させて得られるポリエチレン系樹脂発泡粒子であって、
平均気泡径が２００μｍ以上７００μｍ以下、かつ、連続気泡率が１２％以下であることを特徴とする、ポリエチレン系樹脂発泡粒子である。
（ａ）直鎖状低密度ポリエチレン系樹脂がエチレンと、炭素数６および／または８のα－オレフィンとの共重合体である。
（ｂ）密度が０．９２０ｇ／ｃｍ3以上０．９４０ｇ／ｃｍ3未満である。
（ｃ）メルトフローレート（ＭＦＲ）が０．１ｇ／１０分以上５．０ｇ／１０分以下である。
（ｄ）ゲル・パーミエーション・クロマトグラフ（以降、「ＧＰＣ」と称する場合がある。）により測定される分子量分布（Ｍｗ／Ｍｎ）が３以上５未満である。 The polyethylene-based resin expanded particles of the present invention are obtained by expanding polyethylene-based resin particles having a linear low-density polyethylene-based resin that satisfies the following conditions (a) to (d) as a base resin. Expanded particles,
Polyethylene resin foamed particles having an average cell diameter of 200 μm or more and 700 μm or less and an open cell ratio of 12% or less.
(A) The linear low density polyethylene resin is a copolymer of ethylene and an α-olefin having 6 and / or 8 carbon atoms.
(B) The density is 0.920 g / cm 3 or more and less than 0.940 g / cm 3 .
(C) The melt flow rate (MFR) is 0.1 g / 10 min or more and 5.0 g / 10 min or less.
(D) The molecular weight distribution (Mw / Mn) measured by gel permeation chromatograph (hereinafter sometimes referred to as “GPC”) is 3 or more and less than 5.
　本発明で用いられる直鎖状低密度ポリエチレン系樹脂は、エチレンと、炭素数６および／または８のα－オレフィンとの共重合体である。
前記炭素数６および／または８のα－オレフィンとしては、１－ヘキセン、３，３－ジメチル－１－ブテン、４－メチル－１－ペンテン、１－オクテン等が挙げられる。なお、炭素数６と８のα－オレフィンの両方が共重合されていてもよい。
更に、炭素数６のα－オレフィンが共重合された直鎖状低密度ポリエチレン系樹脂、および炭素数８のα－オレフィンが共重合された直鎖状低密度ポリエチレン系樹脂を混合して用いてもよい。
これらの中でも、後述する密度の直鎖状低密度ポリエチレン系樹脂を得やすい点から、α－オレフィンとしては、炭素数６のα－オレフィンが好ましく、４－メチル－１－ペンテンがより好ましい。 The linear low density polyethylene resin used in the present invention is a copolymer of ethylene and an α-olefin having 6 and / or 8 carbon atoms.
Examples of the α-olefin having 6 and / or 8 carbon atoms include 1-hexene, 3,3-dimethyl-1-butene, 4-methyl-1-pentene, and 1-octene. Both α-olefins having 6 and 8 carbon atoms may be copolymerized.
Further, a linear low density polyethylene resin copolymerized with an α-olefin having 6 carbon atoms and a linear low density polyethylene resin copolymerized with an α-olefin having 8 carbon atoms are mixed and used. Also good.
Among these, the α-olefin is preferably an α-olefin having 6 carbon atoms and more preferably 4-methyl-1-pentene from the viewpoint of easily obtaining a linear low density polyethylene resin having a density described later.
　これらα－オレフィンの直鎖状低密度ポリエチレン系樹脂１００重量％における含有率は、１重量％以上、２０重量％以下が好ましく、特に３重量％以上、１０重量％以下が好ましい。
α－オレフィン含有率が１重量％未満では、成形時の蒸気圧力幅が狭くなる傾向があり、２０重量％を超える場合は、曲げや圧縮等に対する強度低下の傾向がある。 The content of these α-olefins in 100% by weight of the linear low density polyethylene resin is preferably 1% by weight or more and 20% by weight or less, particularly preferably 3% by weight or more and 10% by weight or less.
When the α-olefin content is less than 1% by weight, the steam pressure range during molding tends to be narrow, and when it exceeds 20% by weight, the strength tends to decrease due to bending or compression.
　本発明で用いられる直鎖状低密度ポリエチレン系樹脂の密度は、０．９２０ｇ／ｃｍ3以上０．９４０ｇ／ｃｍ3未満であることが好ましい。
直鎖状低密度ポリエチレン系樹脂の密度が０．９２０ｇ／ｃｍ3未満では、ポリエチレン系樹脂発泡成形体の収縮が大きくなる傾向があり、０．９４０ｇ／ｃｍ3以上では、発泡可能な温度領域が狭くなる傾向がある。 The density of the linear low-density polyethylene resin used in the present invention is preferably 0.920 g / cm 3 or more and less than 0.940 g / cm 3 .
When the density of the linear low density polyethylene resin is less than 0.920 g / cm 3 , the shrinkage of the polyethylene resin foamed molded product tends to increase, and when it is 0.940 g / cm 3 or more, the foamable temperature range is high. There is a tendency to narrow.
　本発明における直鎖状低密度ポリエチレン系樹脂の密度は、０．９２０ｇ／ｃｍ3以上０．９４０ｇ／ｃｍ3未満であることが好ましいが、ポリエチレン系樹脂粒子の密度が０．９２０ｇ／ｃｍ3以上０．９４０ｇ／ｃｍ3未満となるのであれば、密度等が異なるポリエチレン系樹脂を混合しても良く、直鎖状低密度ポリエチレン系樹脂に低密度ポリエチレン（ＬＤＰＥ）や高密度ポリエチレン（ＨＤＰＥ）を混合して使用することもできる。但し、ＬＤＰＥおよび／またはＨＤＰＥは、ポリエチレン系樹脂発泡粒子の気泡径均一性が損なわれない範囲で混合することができ、具体的には、ポリエチレン系樹脂粒子１００重量％中、ＬＤＰＥおよび／またはＨＤＰＥの含有率は１０重量％以下が好ましく、５重量％以下がより好ましい。 The density of the linear low density polyethylene resin in the present invention is preferably 0.920 g / cm 3 or more and less than 0.940 g / cm 3 , but the density of the polyethylene resin particles is 0.920 g / cm 3 or more. If the density is less than 0.940 g / cm 3, polyethylene resins having different densities may be mixed, and low-density polyethylene (LDPE) or high-density polyethylene (HDPE) is added to the linear low-density polyethylene resin. It can also be used by mixing. However, LDPE and / or HDPE can be mixed within a range in which the bubble diameter uniformity of the polyethylene resin expanded particles is not impaired. Specifically, in 100% by weight of the polyethylene resin particles, LDPE and / or HDPE. The content of is preferably 10% by weight or less, and more preferably 5% by weight or less.
　本発明で用いられる直鎖状低密度ポリエチレン系樹脂のメルトフローレート（ＭＦＲ）は、０．１ｇ／１０分以上５．０ｇ／１０分以下であることが好ましく、１．０ｇ／１０分以上３．０ｇ／１０分以下であることがより好ましい。
直鎖状低密度ポリエチレン系樹脂のＭＦＲが０．１ｇ／１０分未満では、得られる発泡粒子の発泡倍率が低くなりすぎる傾向があり、５．０ｇ／１０分超では、得られる発泡粒子に形成される気泡が連泡化しやすくなる傾向がある。
ここで、直鎖状低密度ポリエチレン系樹脂のＭＦＲは、温度１９０℃、荷重２．１６ｋｇｆの条件で測定した値である。 The melt flow rate (MFR) of the linear low density polyethylene resin used in the present invention is preferably 0.1 g / 10 min or more and 5.0 g / 10 min or less, and 1.0 g / 10 min or more 3 More preferably, it is 0.0 g / 10 min or less.
If the MFR of the linear low-density polyethylene resin is less than 0.1 g / 10 minutes, the expansion ratio of the obtained expanded particles tends to be too low, and if it exceeds 5.0 g / 10 minutes, the resulting expanded particles are formed. There is a tendency for the bubbles to be formed to be easily connected.
Here, the MFR of the linear low-density polyethylene resin is a value measured under conditions of a temperature of 190 ° C. and a load of 2.16 kgf.
　本発明においては、直鎖状低密度ポリエチレン系樹脂のゲル・パーミエーション・クロマトグラフ（以降、「ＧＰＣ」と称する場合がある。）を用いて測定される分子量分布（Ｍｗ／Ｍｎ）を調整することにより、成形可能な温度領域が広く、対金型寸法収縮率が小さく、表面美麗性に優れる成形体が得られるポリエチレン系樹脂発泡粒子を製造することができる。 In the present invention, the molecular weight distribution (Mw / Mn) measured using a gel permeation chromatograph (hereinafter sometimes referred to as “GPC”) of a linear low density polyethylene resin is adjusted. As a result, it is possible to produce polyethylene-based resin expanded particles that have a wide temperature range in which molding is possible, have a small dimensional shrinkage against the mold, and provide a molded article with excellent surface aesthetics.
　本発明で用いられる直鎖状低密度ポリエチレン系樹脂のゲル・パーミエーション・クロマトグラフ（ＧＰＣ）を用いて測定される分子量分布（Ｍｗ／Ｍｎ）は、３以上５未満が好ましく、３以上４以下がより好ましい。
直鎖状低密度ポリエチレン系樹脂のＭｗ／Ｍｎが３未満では、成形可能な温度領域が狭くなる傾向があり、Ｍｗ／Ｍｎが５以上では、成形体の対金型寸法収縮率が大きくなる、成形体表面の美麗性に劣る、等の傾向がある。
ここで、分子量分布（Ｍｗ／Ｍｎ）は、ゲル・パーミエーション・クロマトグラフ（ＧＰＣ）測定により得られる、ポリスチレン換算の重量平均分子量Ｍｗと数平均分子量Ｍｎにおいて、ＭｗをＭｎで除した値である。 The molecular weight distribution (Mw / Mn) measured using the gel permeation chromatograph (GPC) of the linear low density polyethylene resin used in the present invention is preferably 3 or more and less than 5, and preferably 3 or more and 4 or less. Is more preferable.
When the Mw / Mn of the linear low-density polyethylene resin is less than 3, the moldable temperature range tends to be narrowed, and when the Mw / Mn is 5 or more, the dimensional shrinkage ratio of the molded product against the mold increases. There is a tendency that the beauty of the surface of the molded body is inferior.
Here, the molecular weight distribution (Mw / Mn) is a value obtained by dividing Mw by Mn in polystyrene-equivalent weight average molecular weight Mw and number average molecular weight Mn obtained by gel permeation chromatography (GPC) measurement. .
　以上のようなエチレンと炭素数６および／または８のα－オレフィンとの共重合体であって、特定の密度、ＭＦＲおよび分子量分布を有する直鎖状低密度ポリエチレン系樹脂は、市販品として入手可能である。
例えば、特開２００１－２１９５１７号には、ウルトゼックス２０２２Ｌや３５２０Ｌの記載があり、これらがエチレンと炭素数６のα－オレフィンとの共重合体であることは、実公平６－４３８０５号公報や株式会社プライムポリマー／製品カタログ（２０１０年１０月発行）から明らかである。
また、特開平９－０９５５４５号、ＷＯ００／０７８８２８、特開２００６－３０７１３９号、特開２００９－１９７２２６号等には、種々の直鎖状低密度ポリエチレン系樹脂の触媒技術を含めた重合方法が記載されており、これらの情報を基に、ポリエチレン系樹脂製造メーカーに問い合わせれば、市販品以外にも試作品として入手することができる。 A linear low-density polyethylene resin having a specific density, MFR and molecular weight distribution, which is a copolymer of ethylene and an α-olefin having 6 and / or 8 carbon atoms as described above, is commercially available. Is possible.
For example, Japanese Patent Application Laid-Open No. 2001-219517 describes Ultzex 2022L and 3520L, and these are copolymers of ethylene and an α-olefin having 6 carbon atoms. It is clear from Prime Polymer Co., Ltd./Product Catalog (issued in October 2010).
In addition, JP-A-9-095545, WO00 / 078828, JP-A-2006-307139, JP-A-2009-197226 and the like describe polymerization methods including catalyst technology for various linear low-density polyethylene resins. Based on these information, it is possible to obtain a prototype other than a commercial product by inquiring a polyethylene resin manufacturer.
　本発明における基材樹脂としては、直鎖状低密度ポリエチレン系樹脂１００重量部に対して、親水性化合物０．０１重量部以上１０重量部以下を含有する基材樹脂を使用することが好ましい。 As the base resin in the present invention, it is preferable to use a base resin containing 0.01 to 10 parts by weight of a hydrophilic compound with respect to 100 parts by weight of a linear low density polyethylene resin.
　前記親水性化合物とは、分子内にカルボキシル基、水酸基、アミノ基、アミド基、エステル基、スルホ基、ポリオキシエチレン基などの親水性基が含有される化合物やその誘導体であり、親水性ポリマーも含む。
具体的には、カルボキシル基を含む化合物としては、ラウリン酸、ラウリン酸ナトリウム等が挙げられ、水酸基を含む化合物として、エチレングリコール、グリセリン等が挙げられる。
また、その他の親水性有機化合物としては、メラミン（化学名：１，３，５－トリアジン－２，４，６－トリアミン）、イソシアヌル酸、イソシアヌル酸縮合物等のトリアジン環を有する有機化合物等が挙げられる。 The hydrophilic compound is a compound containing a hydrophilic group such as a carboxyl group, a hydroxyl group, an amino group, an amide group, an ester group, a sulfo group, or a polyoxyethylene group in the molecule or a derivative thereof. Including.
Specifically, examples of the compound containing a carboxyl group include lauric acid and sodium laurate, and examples of the compound containing a hydroxyl group include ethylene glycol and glycerin.
Other hydrophilic organic compounds include organic compounds having a triazine ring such as melamine (chemical name: 1,3,5-triazine-2,4,6-triamine), isocyanuric acid, and isocyanuric acid condensate. Can be mentioned.
　なお、親水性ポリマーとは、ＡＳＴＭ　Ｄ５７０に準拠して測定された吸水率が０．５重量％以上のポリマーのことであり、いわゆる、吸湿性ポリマー；水に溶けることなく、自重の数倍から数百倍の水を吸収し、圧力がかかっても脱水されがたいポリマーである吸水性ポリマー；および、常温ないし高温状態で水に溶解するポリマーである水溶性ポリマーを包含するものである。 The hydrophilic polymer is a polymer having a water absorption rate of 0.5% by weight or more measured in accordance with ASTM D570, so-called a hygroscopic polymer; from several times its own weight without being dissolved in water. It includes a water-absorbing polymer that absorbs water several hundred times and is difficult to dehydrate even under pressure; and a water-soluble polymer that dissolves in water at room temperature to high temperature.
　本発明に用いられる親水性ポリマーとしては、例えば、
エチレン－アクリル酸－無水マレイン酸三元共重合体、エチレン－（メタ）アクリル酸共重合体のカルボン酸基をナトリウムイオン、カリウムイオンなどのアルカリ金属イオンや亜鉛イオンなどの遷移金属イオンで中和し、分子間を架橋させたアイオノマー系樹脂；
エチレン－（メタ）アクリル酸共重合体などのカルボキシル基含有ポリマー；
ナイロン－６、ナイロン－６，６、共重合ナイロンなどのポリアミド；
ポリエチレングリコール等のノニオン型吸水性ポリマー；
ペレスタット（商品名、三洋化成社製）等に代表されるポリエーテル－ポリオレフィン系樹脂ブロック共重合体；
アクアコーク（商品名、住友精化社製）等に代表される架橋ポリエチレンオキサイド系重合体；などが挙げられる。
これらは、単独で用いてもよく、２種類以上を併用してもよい。 As the hydrophilic polymer used in the present invention, for example,
Neutralize carboxylic acid groups of ethylene-acrylic acid-maleic anhydride terpolymer and ethylene- (meth) acrylic acid copolymer with alkali metal ions such as sodium ion and potassium ion and transition metal ions such as zinc ion An ionomer resin in which the molecules are cross-linked;
Carboxyl group-containing polymers such as ethylene- (meth) acrylic acid copolymers;
Polyamides such as nylon-6, nylon-6,6, copolymer nylon;
Nonionic water-absorbing polymers such as polyethylene glycol;
Polyether-polyolefin resin block copolymer represented by perestat (trade name, manufactured by Sanyo Kasei Co., Ltd.);
Cross-linked polyethylene oxide polymers represented by Aqua Coke (trade name, manufactured by Sumitomo Seika Co., Ltd.) and the like.
These may be used alone or in combination of two or more.
　これら親水性ポリマーの中では、親水性モノマー、ノニオン型吸水性ポリマー、ポリエーテル－ポリオレフィン系樹脂ブロック共重合体が、耐圧容器内での分散安定性が比較的良好であり、かつ比較的少量の添加で吸水性を発揮する為、好ましい。さらには、グリセリン、ポリエチレングリコール、メラミンが、本発明の効果が大きい為、好ましい。 Among these hydrophilic polymers, hydrophilic monomers, nonionic water-absorbing polymers, and polyether-polyolefin resin block copolymers have relatively good dispersion stability in a pressure resistant container, and a relatively small amount. Addition is preferable because it exhibits water absorption. Furthermore, glycerin, polyethylene glycol, and melamine are preferable because the effects of the present invention are great.
　本発明のポリエチレン系樹脂粒子には、必要に応じて、セル造核剤（タルク、炭酸カルシウム、ホウ酸亜鉛、カオリン、シリカ等）、酸化防止剤、帯電防止剤、着色剤、難燃剤等を含有させることができる。 If necessary, the polyethylene resin particles of the present invention contain a cell nucleating agent (talc, calcium carbonate, zinc borate, kaolin, silica, etc.), an antioxidant, an antistatic agent, a colorant, a flame retardant and the like. It can be included.
　本発明で用いられるポリエチレン系樹脂粒子は、以下のようにして、製造することができる。
例えば、直鎖状低密度ポリエチレン系樹脂を上記親水性化合物やその他の添加剤と共に、ドライブレンド法、マスターバッチ法等の混合方法で混合する。得られた混合物を、押出機、ニーダー、バンバリーミキサー（登録商標）、ロール等を用いて溶融混練して、１粒の重量が好ましくは０．２～１０ｍｇ、より好ましくは０．５～６ｍｇのポリエチレン系樹脂粒子に加工する。また、液状の親水性化合物は、押出機に直接添加して溶融混練しても良い。 The polyethylene resin particles used in the present invention can be produced as follows.
For example, a linear low density polyethylene resin is mixed with the hydrophilic compound and other additives by a mixing method such as a dry blend method or a master batch method. The obtained mixture is melt-kneaded using an extruder, kneader, Banbury mixer (registered trademark), roll or the like, and the weight of one grain is preferably 0.2 to 10 mg, more preferably 0.5 to 6 mg. Processed into polyethylene resin particles. The liquid hydrophilic compound may be directly added to the extruder and melt-kneaded.
　本発明におけるポリエチレン系樹脂発泡粒子は、以下のようにして、製造することができる。
例えば、ポリエチレン系樹脂粒子を、水、発泡剤、分散剤と共に耐圧容器内に導入し、耐圧容器内を所定温度、所定圧力に保持した後、ポリエチレン系樹脂粒子を耐圧容器内より低圧雰囲気下に放出して製造することができる。
なお、以降、該発泡工程を、「一段発泡」という場合がある。また、一段発泡で得られたポリエチレン系樹脂発泡粒子を、「一段発泡粒子」という場合がある。 The polyethylene resin expanded particles in the present invention can be produced as follows.
For example, polyethylene resin particles are introduced into a pressure vessel together with water, a foaming agent, and a dispersant, and the pressure vessel is maintained at a predetermined temperature and pressure, and then the polyethylene resin particles are placed in a low-pressure atmosphere from the pressure vessel. It can be released and manufactured.
Hereinafter, the foaming process may be referred to as “one-stage foaming”. In addition, the polyethylene resin expanded particles obtained by single-stage expansion may be referred to as “single-stage expanded particles”.
　本発明で用いられる耐圧容器には特に限定はなく、ポリエチレン系樹脂発泡粒子製造時における容器内圧力、容器内温度に耐えられるものであればよく、例えば、オートクレーブ型の耐圧容器が挙げられる。 The pressure vessel used in the present invention is not particularly limited as long as it can withstand the pressure in the vessel and the temperature in the vessel at the time of producing the polyethylene resin expanded particles, and examples thereof include an autoclave type pressure vessel.
　本発明のポリエチレン系樹脂発泡粒子の製造においては、ポリエチレン系樹脂粒子の水中での分散性を良好なものにする為に、ポリエチレン系樹脂粒子１００重量部に対して、水を１００重量部以上５００重量部以下使用するのが好ましい。 In the production of the polyethylene-based resin expanded particles of the present invention, in order to improve the dispersibility of the polyethylene-based resin particles in water, 100 parts by weight or more and 500 parts by weight of water with respect to 100 parts by weight of the polyethylene-based resin particles. It is preferable to use up to parts by weight.
　本発明で用いられる分散剤としては、難水溶性無機化合物を用いることが好ましい。
ここで、難水溶性無機化合物とは、２５℃での水への溶解量が１重量％未満である無機化合物をいう。
難水溶性無機化合物の具体例としては、例えば、
炭酸カルシウム、炭酸バリウム、第三リン酸カルシウム、第二リン酸カルシウム、第三リン酸マグネシウム、第三リン酸バリウム、硫酸バリウム、ピロリン酸カルシウム等のアルカリ土類金属塩；カオリン、クレー等のアルミノ珪酸塩；などが挙げられる。これらは、単独で用いてもよく、２種類以上を併用してもよい。

　本発明における分散剤の使用量は、その種類や用いるポリエチレン系樹脂粒子の種類や量等によって異なり、一概に規定できないが、ポリエチレン系樹脂粒子１００重量部に対して、０．２重量部以上５重量部以下であることが好ましく、０．２重量部以上３．０重量部以下であることがより好ましい。 As the dispersant used in the present invention, it is preferable to use a poorly water-soluble inorganic compound.
Here, the poorly water-soluble inorganic compound refers to an inorganic compound having a water solubility at 25 ° C. of less than 1% by weight.
Specific examples of the hardly water-soluble inorganic compound include, for example,
Alkaline earth metal salts such as calcium carbonate, barium carbonate, tricalcium phosphate, dicalcium phosphate, tribasic magnesium phosphate, tertiary barium phosphate, barium sulfate, calcium pyrophosphate; aluminosilicates such as kaolin and clay; Can be mentioned. These may be used alone or in combination of two or more.

The amount of the dispersant used in the present invention varies depending on the type and the type and amount of the polyethylene resin particles to be used, and cannot be generally specified, but is 0.2 to 5 parts by weight with respect to 100 parts by weight of the polyethylene resin particles. The amount is preferably not more than parts by weight, more preferably not less than 0.2 parts by weight and not more than 3.0 parts by weight.
　本発明においては、分散剤と共に、分散助剤を併用してもよい。
本発明で用いられる分散助剤としては、界面活性剤を使用することが好ましく、アニオン系界面活性剤、ノニオン系界面活性剤、両性界面活性剤、アニオン系高分子界面活性剤、ノニオン系高分子界面活性剤等の界面活性剤等が挙げられる。
アニオン系界面活性剤としては、例えば、ドデシルベンゼンスルホン酸ナトリウムやｎ－パラフィンスルホン酸ナトリウム、α－オレフィンスルホン酸ナトリウム、アルキルジフェニルエーテルスルホン酸ナトリウム、等が、挙げられる。
ノニオン系界面活性剤としては、例えば、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンソルビタン脂肪酸エステル等が、挙げられる。
両性界面活性剤としては、例えば、アルキルベタイン、アルキルアミンオキシド等が、挙げられる。
アニオン系高分子界面活性剤としては、例えば、ポリアクリル酸塩、ポリスチレンスルホン酸塩、マレイン酸α－オレフィン共重合体塩等が、挙げられる。
ノニオン系高分子界面活性剤としては、例えば、ポリビニルアルコール等が挙げられる。
これらは、単独で用いてもよく、２種類以上を併用してもよい。 In the present invention, a dispersion aid may be used in combination with the dispersant.
As the dispersion aid used in the present invention, a surfactant is preferably used, and an anionic surfactant, a nonionic surfactant, an amphoteric surfactant, an anionic polymer surfactant, and a nonionic polymer. Surfactants such as surfactants are listed.
Examples of the anionic surfactant include sodium dodecylbenzene sulfonate, sodium n-paraffin sulfonate, sodium α-olefin sulfonate, sodium alkyldiphenyl ether sulfonate, and the like.
Examples of nonionic surfactants include polyoxyethylene alkyl ethers and polyoxyethylene sorbitan fatty acid esters.
Examples of amphoteric surfactants include alkyl betaines and alkyl amine oxides.
Examples of the anionic polymer surfactant include polyacrylate, polystyrene sulfonate, maleic acid α-olefin copolymer salt and the like.
Examples of nonionic polymer surfactants include polyvinyl alcohol.
These may be used alone or in combination of two or more.
　本発明における好ましい分散助剤種は使用する分散剤の種類によって変わる為、一概に規定できないが、例えば、分散剤として第三リン酸マグネシウムおよび第三リン酸カルシウムを使用する場合は、アニオン系界面活性剤を使用することが、分散状態が安定になるため好ましい。 Since the preferred dispersion aid type in the present invention varies depending on the type of dispersant used, it cannot be defined unconditionally. For example, when tribasic magnesium phosphate and tribasic calcium phosphate are used as a dispersant, an anionic surfactant is used. Is preferable because the dispersion state becomes stable.
　本発明における分散助剤の使用量は、その種類や用いるポリエチレン系樹脂粒子の種類や量などによって異なり、一概に規定できないが、通常、水１００重量部に対して、分散助剤０．００１重量部以上０．２重量部以下であることが好ましい。 The amount of the dispersion aid used in the present invention varies depending on the type and the type and amount of the polyethylene resin particles to be used, and cannot be generally defined, but is usually 0.001 weight per 100 parts by weight of water. It is preferable that the amount is not less than 0.2 parts by weight.
　本発明で用いられる発泡剤は、ブタン、ペンタン、フロンなどの易揮発性炭化水素；窒素、炭酸ガス、空気などの無機ガス；水が、挙げられる。
これらの中でも、成形時の蒸気圧力幅が広く、また、表面美麗なポリエチレン系樹脂発泡成形体が得られる観点から、無機ガスを用いることが好ましく、炭酸ガスを含む発泡剤を用いることがより好ましい。
炭酸ガスを含む発泡剤を用い、後述する特定の平均気泡径および連続気泡率を有するポリエチレン系樹脂発泡粒子は、成形時の蒸気圧力幅が広くなり、また、表面美麗なポリエチレン系樹脂発泡成形体が得られやすく、本発明の効果がより発現する態様となる。 Examples of the blowing agent used in the present invention include readily volatile hydrocarbons such as butane, pentane, and chlorofluorocarbon; inorganic gases such as nitrogen, carbon dioxide, and air; and water.
Among these, it is preferable to use an inorganic gas, and more preferable to use a foaming agent containing carbon dioxide gas, from the viewpoint of obtaining a polyethylene resin foamed molded article having a wide vapor pressure range during molding and a beautiful surface. .
Polyethylene resin foam particles having a specific average cell diameter and open cell ratio, which will be described later, using a foaming agent containing carbon dioxide gas, have a wide vapor pressure range at the time of molding, and have a beautiful surface. Therefore, the effect of the present invention is more manifested.
　本発明における発泡剤の使用量は、使用するポリエチレン系樹脂粒子の種類、発泡剤の種類、目的とする発泡倍率等により異なり、一概には規定できないが、ポリエチレン系樹脂粒子１００重量部に対して、２重量部以上６０重量部以下であることが好ましい。 The amount of foaming agent used in the present invention varies depending on the type of polyethylene resin particles used, the type of foaming agent, the target foaming ratio, etc., and cannot be specified unconditionally, but with respect to 100 parts by weight of polyethylene resin particles. The amount is preferably 2 parts by weight or more and 60 parts by weight or less.
　以上のようにして、耐圧容器内に調製された、ポリエチレン系樹脂粒子を含んでなる水分散物は、攪拌下、所定の圧力まで加圧され、所定の温度まで昇温された後、一定時間（通常５～１８０分間、好ましくは１０～６０分間）保持される。その後、ポリエチレン系樹脂粒子を含んでなる加圧された水分散物が、耐圧容器下部に設けられたバルブを開放して低圧雰囲気下（通常は大気圧下）に放出されることにより、ポリエチレン系樹脂発泡粒子が製造される。 The aqueous dispersion containing the polyethylene resin particles prepared in the pressure vessel as described above is pressurized to a predetermined pressure with stirring and heated to a predetermined temperature for a certain period of time. (Normally 5 to 180 minutes, preferably 10 to 60 minutes). Thereafter, the pressurized aqueous dispersion containing polyethylene resin particles is released into a low-pressure atmosphere (usually atmospheric pressure) by opening a valve provided at the lower part of the pressure-resistant container. Resin foam particles are produced.
　本発明において、水分散物を放出する雰囲気温度は、通常、常温である。ただし、水蒸気等の加熱媒体を用いて、雰囲気温度を６０～１２０℃、好ましくは８０～１１０℃に加熱することにより、常温雰囲気中に放出する場合に比べて、より高発泡倍率のポリエチレン系樹脂発泡粒子を得ることができる。 In the present invention, the atmospheric temperature at which the aqueous dispersion is released is usually room temperature. However, by using a heating medium such as water vapor to heat the atmosphere to 60 to 120 ° C., preferably 80 to 110 ° C., a polyethylene-based resin having a higher expansion ratio than that in a normal temperature atmosphere. Expanded particles can be obtained.
　本発明における耐圧容器内を加熱する所定温度（以下、「発泡温度」と称す場合がある。）は、用いられるポリエチレン系樹脂粒子の融点［Ｔｍ（℃）］、種類等により異なり、一概には規定できないが、ポリエチレン系樹脂粒子の軟化温度以上に加熱することが好ましく、Ｔｍ－３０（℃）以上、Ｔｍ＋１０（℃）以下に加熱することがより好ましい。 The predetermined temperature for heating the inside of the pressure vessel in the present invention (hereinafter sometimes referred to as “foaming temperature”) varies depending on the melting point [Tm (° C.)], type, etc. of the polyethylene-based resin particles used. Although it cannot be specified, it is preferable to heat to a temperature higher than the softening temperature of the polyethylene resin particles, and it is more preferable to heat to Tm−30 (° C.) or higher and Tm + 10 (° C.) or lower.
　ここで、ポリエチレン系樹脂粒子の融点とは、示差走査熱量計ＤＳＣを用いて、エチレン系樹脂粒子４～６ｍｇを１０℃／分の昇温速度で１０℃から１９０℃まで昇温してポリエチレン系樹脂粒子を融解させた後、１０℃／分の降温速度で１９０℃から１０℃まで降温して結晶化させた後に、さらに１０℃／分の昇温速度で１０℃から１９０℃まで昇温した際に得られるＤＳＣ曲線から、２回目の昇温時の融解ピーク温度として求められる値である。 Here, the melting point of the polyethylene resin particles means that the polyethylene resin particles are heated from 10 ° C. to 190 ° C. at a heating rate of 10 ° C./min using a differential scanning calorimeter DSC. After melting the resin particles, the temperature was decreased from 190 ° C. to 10 ° C. at a temperature decrease rate of 10 ° C./min and crystallized, and then the temperature was further increased from 10 ° C. to 190 ° C. at a temperature increase rate of 10 ° C./min. It is a value obtained from the DSC curve obtained at this time as the melting peak temperature at the second temperature increase.
　以上のようにして、一段発泡により得られたポリエチレン系樹脂発泡粒子（一段発泡粒子）は、そのまま型内発泡成形に使用しても良いし、また、再度発泡させ、目的とする発泡倍率のポリエチレン系樹脂発泡粒子した後に型内発泡成形に使用しても良い。
なお、以降、一段発泡粒子をさらに発泡させる工程を、「二段発泡」と称す場合がある。また、二段発泡で得られるポリエチレン系樹脂発泡粒子を、「二段発泡粒子」と称す場合がある。 As described above, the polyethylene resin expanded particles (single-stage expanded particles) obtained by single-stage expansion may be used as they are for in-mold foam molding, or may be expanded again and polyethylene having the desired expansion ratio. After the resin-based resin foamed particles, they may be used for in-mold foam molding.
Hereinafter, the step of further foaming the first-stage expanded particles may be referred to as “two-stage expansion”. In addition, polyethylene resin foam particles obtained by two-stage foaming may be referred to as “two-stage foamed particles”.
　本発明における二段発泡は、公知の方法を採用でき、例えば、次のようにして行う。
ポリエチレン系樹脂発泡粒子を加圧タンク内に入れ、所定圧力の無機ガスで加圧することによりポリエチレン樹脂発泡粒子内に無機ガスを導入して、一定時間放置することにより、発泡粒子の内圧を大気圧より高めた後、ポリエチレン系樹脂発泡粒子を好ましくは０．０１ＭＰａ－Ｇ以上０．１５ＭＰａ－Ｇ以下、より好ましくは０．０２ＭＰａ－Ｇ以上０．１０ＭＰａ－Ｇ以下の蒸気（水蒸気）で加熱することにより、二段発泡させる。 For the two-stage foaming in the present invention, a known method can be adopted, for example, as follows.
Put the polyethylene resin foam particles in a pressurized tank, pressurize with an inorganic gas of a predetermined pressure, introduce the inorganic gas into the polyethylene resin foam particles, and leave it for a certain time, the internal pressure of the foam particles is atmospheric pressure After further increase, the polyethylene resin expanded particles are preferably heated with steam (water vapor) of 0.01 MPa-G or more and 0.15 MPa-G or less, more preferably 0.02 MPa-G or more and 0.10 MPa-G or less. To make two-stage foaming.
　この際、ポリエチレン系樹脂発泡粒子の内圧は、０．０５～０．７０ＭＰａ－Ｇに、好ましくは０．１０～０．５０ＭＰａ－Ｇに調整されることが好ましい。
ポリエチレン系樹脂発泡粒子の内圧が０．０５ＭＰａ－Ｇ未満では、発泡倍率がそれほど増加しない傾向があり、０．７０ＭＰａ－Ｇを超えると、ポリエチレン系樹脂発泡粒子を構成する気泡が二段発泡により連続気泡化しやすくなり、該発泡粒子を金型内に充填して型内発泡成形すると、得られるポリエチレン系樹脂発泡成形体が収縮したものとなる虞がある。
なお、本明細書において、圧力単位の表記ＭＰａ－ＧのＧはゲージ圧であることを示す。 At this time, the internal pressure of the polyethylene resin expanded particles is preferably adjusted to 0.05 to 0.70 MPa-G, preferably 0.10 to 0.50 MPa-G.
When the internal pressure of the polyethylene resin expanded particles is less than 0.05 MPa-G, the expansion ratio tends not to increase so much, and when it exceeds 0.70 MPa-G, the bubbles constituting the polyethylene resin expanded particles are continuously formed by two-stage expansion. It becomes easy to form bubbles, and when the foamed particles are filled in a mold and subjected to in-mold foam molding, the resulting polyethylene-based resin foam molded article may shrink.
In the present specification, G in the unit of pressure MPa-G indicates a gauge pressure.
　本発明における二段発泡で用いられる無機ガスとしては特に制限はなく、空気、窒素、炭酸ガス等が挙げられるが、安全性や環境適合性の観点からは、空気であることが好ましい。 The inorganic gas used in the two-stage foaming in the present invention is not particularly limited, and examples thereof include air, nitrogen, carbon dioxide gas, etc. Air is preferable from the viewpoint of safety and environmental compatibility.
　本発明におけるポリエチレン系樹脂発泡粒子の発泡倍率は、特に制限はないが、高い発泡倍率でも成形後の収縮が小さい（すなわち、対金型収縮率が小さい）という本発明の効果が顕著となる点からは、成形に供するポリエチレン系樹脂発泡粒子の発泡倍率が１５倍以上、３０倍以下であることが好ましい。
成形に供するポリエチレン系樹脂発泡粒子の発泡倍率が１５倍未満では、成形後の収縮という観点のみで評価すると、本発明に依らなくとも対金型収縮率の小さい発泡成形体を得ることが可能であるが、１５倍以上において本発明の効果が顕著となる。該発泡倍率が３０倍を超えると、発泡成形体の機械的強度が低下する傾向にある。 The expansion ratio of the polyethylene resin expanded particles in the present invention is not particularly limited, but the effect of the present invention is remarkable in that the shrinkage after molding is small (that is, the shrinkage ratio against the mold is small) even at a high expansion ratio. From the above, it is preferable that the expansion ratio of the polyethylene-based resin foam particles to be molded is 15 times or more and 30 times or less.
When the expansion ratio of the polyethylene resin foam particles to be used for molding is less than 15 times, it is possible to obtain a foamed molded article having a small mold shrinkage rate without depending on the present invention when evaluated only from the viewpoint of shrinkage after molding. However, the effect of the present invention becomes remarkable at 15 times or more. When the expansion ratio exceeds 30 times, the mechanical strength of the foamed molded product tends to decrease.
　本発明のポリエチレン系樹脂発泡粒子の平均気泡径は、２００μｍ以上７００μｍ以下であることが好ましく、３００μｍ以上６００μｍ以下であることがより好ましい。
ポリエチレン系樹脂発泡粒子の平均気泡径が２００μｍ未満では、成形時の蒸気圧力幅が狭くなる傾向があり、得られるポリエチレン系樹脂発泡成形体の収縮が大きくなる傾向がある。平均気泡径が７００μｍを超えると、気泡が連泡化しやすくなり、得られるポリエチレン系樹脂発泡成形体の外観が悪くなる傾向がある。
特に、平均気泡径が３００μｍ以上、６００μｍ以下の場合には、成形する際の蒸気圧力幅がより広くなる傾向があり、より好ましい態様である。
このような平均気泡径が３００μｍ以上、６００μｍ以下のポリエチレン系樹脂発泡粒子は、前述の一段発泡では得られ難い傾向があるが、二段発泡を行うことにより容易に得ることができる。 The average cell diameter of the polyethylene resin expanded particles of the present invention is preferably 200 μm or more and 700 μm or less, and more preferably 300 μm or more and 600 μm or less.
When the average cell diameter of the polyethylene resin foamed particles is less than 200 μm, the vapor pressure width during molding tends to be narrow, and the shrinkage of the resulting polyethylene resin foam molded product tends to increase. When the average cell diameter exceeds 700 μm, the cells are liable to form a continuous bubble, and the appearance of the resulting polyethylene-based resin foam molded article tends to deteriorate.
In particular, when the average bubble diameter is 300 μm or more and 600 μm or less, the vapor pressure width during molding tends to be wider, which is a more preferable embodiment.
Such polyethylene foamed resin particles having an average cell diameter of 300 μm or more and 600 μm or less tend to be difficult to obtain by the above-mentioned one-stage foaming, but can be easily obtained by carrying out two-stage foaming.
　ここで、ポリエチレン系樹脂発泡粒子の平均気泡径は、次のようにして測定した値である。
発泡粒子の切断面の顕微鏡観察により得られる画像において、発泡粒子のほぼ中心を通る直線を引き、該直線が貫通している気泡数ｎおよび、該直線と発泡粒子表面との交点から定まる発泡粒子径Ｌ（μｍ）を読み取り、式（１）によって求める。
平均気泡径（μｍ）＝Ｌ／ｎ　・・・式（１）　　。 Here, the average cell diameter of the polyethylene-based resin expanded particles is a value measured as follows.
In an image obtained by microscopic observation of the cut surface of the foamed particle, a straight line passing through substantially the center of the foamed particle is drawn, and the foamed particle is determined from the number of bubbles n passing through the straight line and the intersection of the straight line and the surface of the foamed particle The diameter L (μm) is read and obtained by the equation (1).
Average bubble diameter (μm) = L / n Formula (1).
　本発明のポリエチレン系樹脂発泡粒子の気泡径均一性としては、気泡径が平均気泡径±１５％以内である気泡が占める割合が、発泡粒子全体の８０％以上であることが好ましく、９０％以上であることがより好ましい。
気泡径が平均気泡径±１５％以内である気泡が占める割合が、発泡粒子全体の８０％以上であれば、該発泡粒子から得られる成形体は、色目が均一となり、美麗である。 As the cell diameter uniformity of the polyethylene-based resin expanded particles of the present invention, the ratio of the bubbles whose average cell diameter is within ± 15% is preferably 80% or more of the entire expanded particles, and 90% or more. It is more preferable that
When the ratio of the bubbles whose average bubble diameter is within ± 15% is 80% or more of the entire foamed particles, the molded product obtained from the foamed particles has a uniform color and is beautiful.
　ここで、気泡径が平均気泡径±１５％以内である気泡が占める割合は、発泡粒子断面を光学顕微鏡にて観察した際、発泡粒子断面の中央付近３０００μｍ×３０００μｍの領域内にある全気泡に関して、気泡径を測定した後、気泡径が平均気泡径±１５％以内である気泡の数を計測し、全気泡の数で除した値である。
なお、気泡径は、下記の方法にて測定する。気泡内において最大の長さｄ1となる直線を引き、その直線の垂直二等分線と気泡との接点間距離ｄ2を求め、ｄ1とｄ2の平均値を気泡径とする。
ただし、上記領域内に気泡全体が入っていないもの、例えば、気泡の半分だけ領域内に入っているような気泡については、測定から除く。 Here, the ratio of the bubbles whose bubble diameter is within an average bubble diameter of ± 15% is related to the total bubbles in the region of 3000 μm × 3000 μm near the center of the expanded particle cross section when the expanded particle cross section is observed with an optical microscope. After the bubble diameter is measured, the number of bubbles whose average bubble diameter is within ± 15% is measured and divided by the total number of bubbles.
The bubble diameter is measured by the following method. A straight line having the maximum length d 1 in the bubble is drawn, a distance d 2 between the contact points of the perpendicular bisector of the straight line and the bubble is obtained, and an average value of d 1 and d 2 is defined as the bubble diameter.
However, a bubble that does not contain the entire bubble in the region, for example, a bubble that is contained in the region by half of the bubble is excluded from the measurement.
　一般に、発泡粒子において気泡径が小さいほど、発泡粒子表面が白くなる傾向がある為、ポリエチレン系樹脂発泡粒子の気泡径が不均一である場合、得られた成形体は、表面に色ムラが目立つ傾向がある。この現象は、着色剤を使用した場合に、顕著に現れる。 In general, the smaller the cell diameter in the expanded particles, the more the surface of the expanded particles tends to become white. Therefore, when the cell diameter of the polyethylene resin expanded particles is uneven, the resulting molded product has noticeable color unevenness on the surface. Tend. This phenomenon appears remarkably when a colorant is used.
　本発明のポリエチレン系樹脂発泡粒子は、気泡径が均一である為、成形時の発泡性が均一となり、得られる発泡成形体の表面美麗性にも優れる。これに対して、ポリエチレン系樹脂発泡粒子内の気泡径が不均一な場合、同じ成形条件でも、発泡粒子間で発泡性が異なる為、ボイドが目立つなどの問題が生じる傾向がある。 Since the foamed polyethylene resin particles of the present invention have a uniform cell diameter, the foamability at the time of molding becomes uniform, and the surface beauty of the resulting foamed molded article is excellent. On the other hand, when the bubble diameter in the polyethylene resin expanded particles is non-uniform, there is a tendency that voids are conspicuous because the expanded properties differ between the expanded particles even under the same molding conditions.
　このような気泡径が均一なポリエチレン系樹脂発泡粒子を得る為には、
（ａ）直鎖状低密度ポリエチレン系樹脂がエチレンと、炭素数６および／または８のα－オレフィンとの共重合体である、
（ｂ）密度が０．９２０ｇ／ｃｍ3以上０．９４０ｇ／ｃｍ3未満である、
（ｃ）メルトフローレート（ＭＦＲ）が０．１～５．０ｇ／１０分である、
（ｄ）ゲル・パーミエーション・クロマトグラフ（ＧＰＣ）により測定される分子量分布（Ｍｗ／Ｍｎ）が３以上５未満である、
ことが重要である。
さらに、気泡径をより均一にする観点からは、前述した親水性化合物を前述の量で添加することが好ましい。直鎖状低密度ポリエチレン系樹脂１００重量部に対して、グリセリン、ポリエチレングリコールおよびメラミンよりなる群から選ばれる少なくとも１種を０．１重量部以上、２重量部以下含有することがより好ましく、グリセリンおよび／またはポリエチレングリコールを０．１重量部以上、２重量部以下含有することが特に好ましい。 In order to obtain such polyethylene-based resin foam particles having a uniform cell diameter,
(A) the linear low-density polyethylene resin is a copolymer of ethylene and an α-olefin having 6 and / or 8 carbon atoms;
(B) the density is 0.920 g / cm 3 or more and less than 0.940 g / cm 3 ;
(C) The melt flow rate (MFR) is 0.1 to 5.0 g / 10 min.
(D) The molecular weight distribution (Mw / Mn) measured by gel permeation chromatograph (GPC) is 3 or more and less than 5.
This is very important.
Furthermore, from the viewpoint of making the bubble diameter more uniform, it is preferable to add the aforementioned hydrophilic compound in the aforementioned amount. More preferably, at least one selected from the group consisting of glycerin, polyethylene glycol and melamine is contained in an amount of 0.1 part by weight or more and 2 parts by weight or less based on 100 parts by weight of the linear low density polyethylene resin. It is particularly preferable to contain 0.1 to 2 parts by weight of polyethylene glycol.
　本発明におけるポリエチレン系樹脂発泡粒子の連続気泡率は、１２％以下であることが好ましく、１０％以下であることがより好ましく、６％以下であることが特に好ましい。
連続気泡率が１２％を超えると、型内発泡成形したときに収縮が起こり、ポリエチレン系樹脂型内発泡成形体の表面美麗性および圧縮強度が低下する傾向にある。 The open cell ratio of the polyethylene resin expanded particles in the present invention is preferably 12% or less, more preferably 10% or less, and particularly preferably 6% or less.
When the open cell ratio exceeds 12%, shrinkage occurs when in-mold foam molding is performed, and the surface beauty and compressive strength of the polyethylene-based resin in-mold foam molding tend to decrease.
　本発明のポリエチレン系樹脂発泡粒子においては、平均気泡径としては２００μｍ以上７００μｍ以下であることが好ましく、かつ、連続気泡率が１２％以下であることが好ましい。 In the polyethylene resin foamed particles of the present invention, the average cell diameter is preferably 200 μm or more and 700 μm or less, and the open cell rate is preferably 12% or less.
　従来のように、発泡剤として水を用いる方法では、平均気泡径と連続気泡率を両立することができなかった。一方、発泡剤として炭酸ガスを用いる場合は、平均気泡径と連続気泡率の両立が可能であったが、型内発泡成形する際の成形可能な蒸気圧力の幅が狭いという問題があった。
これに対して、本発明は、エチレンと、炭素数６および／または８のα－オレフィンとの共重合体である直鎖状低密度ポリエチレン系樹脂を用いることにより、平均気泡径と連続気泡率の両立と共に、成形可能な蒸気圧力の幅も広がることを見出したものである。 As in the prior art, the method using water as a foaming agent cannot achieve both an average cell diameter and an open cell ratio. On the other hand, when carbon dioxide gas is used as the foaming agent, both the average cell diameter and the open cell ratio can be achieved, but there is a problem that the range of vapor pressure that can be molded when performing in-mold foam molding is narrow.
On the other hand, the present invention uses a linear low-density polyethylene resin that is a copolymer of ethylene and an α-olefin having 6 and / or 8 carbon atoms, so that an average cell diameter and an open cell ratio are obtained. As a result, the inventors have found that the range of vapor pressures that can be molded also increases.
　本発明で用いられる直鎖状低密度ポリエチレン系樹脂、ポリエチレン系樹脂発泡粒子、およびポリエチレン系樹脂発泡粒子は、いずれも無架橋のものである。
本発明において、「無架橋」とは、具体的には、熱キシレンに不溶なゲル分率が３．０重量％以下のものをいう。 The linear low density polyethylene resin, polyethylene resin expanded particles, and polyethylene resin expanded particles used in the present invention are all non-crosslinked.
In the present invention, “non-crosslinked” specifically refers to those having a gel fraction insoluble in hot xylene of 3.0% by weight or less.
　ここで、ゲル分率とは、以下の方法により測定したゲル成分量の、元の樹脂重量に対する重量比率である。
すなわち、２００メッシュの金網袋中に、０．５ｇの直鎖状低密度ポリエチレン系樹脂、ポリエチレン系樹脂発泡粒子、またはポリエチレン系樹脂発泡粒子を入れて、該樹脂または粒子が袋の外に出ないように、金網の端を折り込む。
該金網袋を、大気圧下で沸騰させたキシレン５０ｍｌ中に３時間浸漬した後、冷却してキシレンから取り出す操作を、計３回行う。
取り出した金網袋を常温下で一晩乾燥させた後に、１５０℃のオーブン中で１時間乾燥させ、常温まで自然冷却させる。冷却後の金網袋内に残留した成分重量を測定して、ゲル成分重量とする。
ゲル分率（％）＝（ゲル成分重量／０．５）×１００の式により、ゲル分率を算出する。 Here, the gel fraction is a weight ratio of the gel component amount measured by the following method to the original resin weight.
That is, 0.5 g of linear low density polyethylene resin, polyethylene resin expanded particles, or polyethylene resin expanded particles are put in a 200 mesh wire mesh bag, and the resin or particles do not come out of the bag. Fold the end of the wire mesh so that.
The wire mesh bag is immersed in 50 ml of xylene boiled under atmospheric pressure for 3 hours, and then cooled and taken out from xylene three times in total.
The wire mesh bag taken out is dried overnight at room temperature, then dried in an oven at 150 ° C. for 1 hour, and then naturally cooled to room temperature. The weight of the component remaining in the wire mesh bag after cooling is measured to obtain the gel component weight.
The gel fraction is calculated by the formula: gel fraction (%) = (gel component weight / 0.5) × 100.
　本発明のポリエチレン系樹脂発泡粒子は無架橋であることから、成形時の蒸気圧力幅が広く、表面美麗なポリエチレン系樹脂発泡成形体を得ることができる。
これに対して、架橋されたポリエチレン系樹脂発泡粒子では、成形時の蒸気圧力幅が狭くなる傾向があり、ポリエチレン系樹脂発泡成形体の表面性も低下する傾向がある。 Since the polyethylene resin foamed particles of the present invention are non-crosslinked, a polyethylene resin foamed molded article having a wide vapor pressure range during molding and a beautiful surface can be obtained.
On the other hand, in the cross-linked polyethylene-based resin expanded particles, the vapor pressure width at the time of molding tends to be narrow, and the surface property of the polyethylene-based resin expanded molded body also tends to be lowered.
　本発明においては、上記のようにして得られたポリエチレン系樹脂発泡粒子を、所定形状の金型内に充填し、水蒸気等で加熱して、発泡粒子を互いに融着させる、いわゆる、型内発泡成形を行うことによって、ポリエチレン系樹脂発泡成形体を得ることができる。 In the present invention, the foamed polyethylene resin particles obtained as described above are filled in a mold having a predetermined shape and heated with steam or the like, so that the foamed particles are fused together, so-called in-mold foaming. By performing the molding, a polyethylene resin foam molded article can be obtained.
　型内発泡成形方法としては、例えば、
イ）ポリエチレン系樹脂発泡粒子を無機ガス（例えば空気や窒素、二酸化炭素、等）で加圧処理してポリエチレン系樹脂発泡粒子内に無機ガスを含浸させ所定の内圧を付与した後、金型に充填し、水蒸気で加熱融着させる方法、
ロ）ポリエチレン系樹脂発泡粒子をガス圧力で圧縮して金型に充填し、ポリエチレン系樹脂発泡粒子の回復力を利用して、水蒸気で加熱融着させる方法、
ハ）特に前処理することなくポリエチレン系樹脂発泡粒子を金型に充填し、水蒸気で加熱融着させる方法、
などの方法が利用し得る。 As an in-mold foam molding method, for example,
B) Pressurizing the polyethylene resin expanded particles with an inorganic gas (for example, air, nitrogen, carbon dioxide, etc.) to impregnate the polyethylene resin expanded particles with an inorganic gas to give a predetermined internal pressure, Filling and heat-sealing with steam,
B) A method in which polyethylene resin foam particles are compressed by gas pressure and filled in a mold, and heat recovery is performed with water vapor using the recovery force of the polyethylene resin foam particles.
C) A method in which polyethylene resin foamed particles are filled in a mold without any pretreatment and heat-sealed with water vapor.
Such a method can be used.
　本発明のポリエチレン系樹脂発泡粒子からポリエチレン系樹脂型内発泡成形体を型内発泡成形する具体的方法としては、例えば、
予めポリエチレン系樹脂発泡粒子を特に前処理することなく、あるいは、耐圧容器内で空気加圧し、ポリエチレン系樹脂予備発泡粒子中に空気を圧入することにより発泡能を付与した後、ポリエチレン系樹脂発泡粒子を２つの金型よりなる閉鎖しうるが密閉し得ない成形空間内に充填し、水蒸気などを加熱媒体として０．０５～０．２０ＭＰａ－Ｇ程度の加熱水蒸気圧で３～３０秒程度の加熱時間で成形し、ポリエチレン系樹脂予備発泡粒子同士を融着させ、金型を水冷により冷却した後、金型を開き、ポリエチレン系樹脂型内発泡成形体を得る方法、などが挙げられる。 As a specific method for in-mold foam molding of a polyethylene-based resin in-mold foam molding from the polyethylene-based resin foam particles of the present invention, for example,
Without pre-treating the polyethylene resin expanded particles in advance, or after applying air pressure in a pressure resistant container and pressurizing the air into the polyethylene resin pre-expanded particles, the polyethylene resin expanded particles are then provided. Is filled in a molding space that can be closed but cannot be sealed with two molds, and heated for about 3 to 30 seconds with a steam pressure of about 0.05 to 0.20 MPa-G using steam as a heating medium Examples of the method include molding by time, fusing the polyethylene resin pre-expanded particles together, cooling the mold by water cooling, then opening the mold, and obtaining a polyethylene resin in-mold foam molding.
　このようにして得られたポリエチレン系樹脂発泡成形体は、対金型寸法収縮率が小さく、変形が少なく、表面伸びが良い。 The thus obtained polyethylene-based resin foam molded article has a small mold dimensional shrinkage, little deformation, and good surface elongation.
　本発明におけるポリエチレン系樹脂発泡成形体の対金型寸法収縮率は、使用する樹脂、発泡粒子の発泡倍率、成形時の蒸気圧力、さらには金型の形状などにより異なる為、一概に規定できないが、発泡倍率が２０倍以上のポリエチレン系樹脂発泡粒子を使用した場合、概ね２～４％が好ましい。 Although the dimensional shrinkage ratio of the polyethylene-based resin foam molded body in the present invention differs depending on the resin used, the foaming ratio of the foamed particles, the vapor pressure during molding, and the shape of the mold, it cannot be specified unconditionally. When polyethylene-based resin expanded particles having an expansion ratio of 20 times or more are used, approximately 2 to 4% is preferable.
　一般に、型内発泡成形に供される発泡粒子の発泡倍率が高いほど、強度がない為、成形後の収縮が大きく、乾燥後の対金型寸法収縮率が大きくなる傾向にある。
また、成形時の蒸気圧力が高くなると共に、発泡粒子の膨らむ力（発泡力）が強くなる為、一般に、対金型寸法収縮率は小さくなる。ただし、蒸気圧力が高くなりすぎると、発泡粒子が熱により収縮する為、対金型寸法収縮率は大きくなる傾向がある。
さらに、金型の形状による影響も受け、変形が発生しやすい形状の成形体の場合は、対金型寸法収縮率が大きくなる傾向にある。 In general, the higher the expansion ratio of the foamed particles used for in-mold foam molding, the less the strength, the greater the shrinkage after molding, and the greater the shrinkage ratio of the mold after drying.
In addition, the steam pressure at the time of molding increases, and the expansion force (foaming force) of the expanded particles increases, so that the dimensional shrinkage against the mold generally decreases. However, if the vapor pressure becomes too high, the foamed particles shrink due to heat, so that the shrinkage ratio against the mold tends to increase.
Furthermore, in the case of a molded body that is also affected by the shape of the mold and is likely to be deformed, the dimensional shrinkage ratio of the mold tends to increase.
　本発明におけるポリエチレン系樹脂発泡成形体の変形は、使用する樹脂、発泡粒子の発泡倍率、成形時の蒸気圧力、さらには金型の形状などに影響を受けるが、変形していないものが好ましい。
型内発泡成形に供される発泡粒子の発泡倍率が低いほど、強度が高い為、金型の形状を保持しやすい。また、一般に成形時の蒸気圧力が低い程、成形後の変形が少なく、乾燥により金型の形状に戻りやすい。一方、蒸気圧力が高い程、変形が大きくなり、乾燥工程を経ても、変形が戻りきらない傾向がある。 The deformation of the polyethylene-based resin foam molded body in the present invention is influenced by the resin used, the expansion ratio of the expanded particles, the vapor pressure at the time of molding, and the shape of the mold.
The lower the expansion ratio of the expanded particles used for in-mold foam molding, the higher the strength, and the easier it is to maintain the shape of the mold. In general, the lower the vapor pressure during molding, the less deformation after molding and the easier it is to return to the shape of the mold upon drying. On the other hand, the higher the steam pressure, the larger the deformation, and there is a tendency that the deformation does not return even after the drying process.
　本発明におけるポリエチレン系樹脂発泡成形体の表面伸びは、発泡粒子の隙間（ボイド）がない状態が、発泡成形体の表面が美麗である為、好ましい。
一般に、成形時の蒸気圧力が低すぎると、発泡粒子の発泡力が弱い為、ボイドが多く発生する。逆に、蒸気圧力が高すぎる場合も、ボイドが発生する場合がある。 The surface elongation of the polyethylene resin foam molded article in the present invention is preferably in a state where there are no voids between the foamed particles because the surface of the foam molded article is beautiful.
Generally, when the vapor pressure at the time of molding is too low, the foaming force of the foamed particles is weak and many voids are generated. Conversely, voids may also occur when the vapor pressure is too high.
　本発明においては、良好な成形体が得られる本加熱工程での蒸気圧力の範囲を、「適正蒸気圧幅」とした。
本加熱工程での蒸気圧力が適正蒸気圧幅の下限値よりも低い場合、得られる成形体内部が融着しておらず、表面の伸びが悪く、ボイドが目立つなどの問題がある。
本加熱工程での蒸気圧力が適正蒸気圧幅の上限値よりも高い場合、成形後の変形が大きく、乾燥後も変形が戻らない、対金型寸法収縮率が大きいなどの問題があり、さらに蒸気圧力が高すぎる場合は、成形体が収縮してしまい、使用できる成形体が得られない場合がある。 In the present invention, the range of the vapor pressure in the main heating step in which a good molded body is obtained is defined as “appropriate vapor pressure width”.
When the vapor pressure in the main heating step is lower than the lower limit value of the appropriate vapor pressure width, there is a problem that the inside of the obtained molded body is not fused, the surface is poorly stretched, and voids are conspicuous.
If the steam pressure in this heating process is higher than the upper limit of the appropriate steam pressure width, there is a problem that deformation after molding is large, deformation does not return after drying, and the dimensional shrinkage ratio against the mold is large. When the vapor pressure is too high, the molded body shrinks and a usable molded body may not be obtained.
　次に、本発明のポリエチレン系樹脂発泡粒子の製造方法を実施例及び比較例を挙げて、詳細に説明するが、これらに限定されるものではない。 Next, although the manufacturing method of the polyethylene-type resin expanded particle of this invention is demonstrated in detail, giving an Example and a comparative example, it is not limited to these.
　実施例および比較例において実施した評価方法に関して、説明する。 The evaluation methods implemented in the examples and comparative examples will be described.
　＜メルトフローレートの測定＞
　ポリエチレン系樹脂のメルトフローレート（ＭＦＲ）は、ＪＩＳ　Ｋ７２１０記載のＭＩ測定器を用い、オリフィス２．０９５９±０．００５ｍｍφ、オリフィス長さ８．０００±０．０２５ｍｍ、荷重２１６０ｇ、１９０±０．２℃の条件下で測定した。 <Measurement of melt flow rate>
The melt flow rate (MFR) of the polyethylene resin was measured using an MI measuring instrument described in JIS K7210, with an orifice of 2.0959 ± 0.005 mmφ, an orifice length of 8.000 ± 0.025 mm, a load of 2160 g, and 190 ± 0.2. Measured under the condition of ° C.
　＜分子量分布（Ｍｗ／Ｍｎ）の測定＞
　ポリエチレン系樹脂のＧＰＣによる分子量分布（Ｍｗ／Ｍｎ）は、以下の条件にて測定した。
測定機器：Ｗａｔｅｒｓ社製Ａｌｌｉａｎｃｅ　ＧＰＣ２０００型
カラム　：ＴＳＫｇｅｌ　ＧＭＨ６－ＨＴ　２本
　　　　　ＴＳＫｇｅｌ　ＧＭＨ６－ＨＴＬ　２本
　　　　［それぞれ、内径７．５ｍｍ×長さ３００ｍｍ；東ソー（株）製］
移動相　：高速液体クロマトグラフ用ｏ－ジクロロベンゼン（０．０２５％ＢＨＴ含有）
カラム温度：１４０℃
流速　　：１．０ｍＬ／分
試料濃度：０．１５％（Ｗ／Ｖ）ｏ－ジクロロベンゼン
標準物質：標準ポリスチレン（Ｓｈｏｄｅｘ　Ｓｔａｎｄａｒｄ；分子量＝７．３０×１０6、３．８５×１０6、２．０６×１０6、７．３６×１０5、１．９７×１０5、２．２０×１０4、１．３９×１０4、７．２０×１０3、２．９７×１０3）、ポリスチレンＡ３００（Ｓｈｏｄｅｘ社製、分子量＝３．７０×１０2）＜計１０種類＞　　。 <Measurement of molecular weight distribution (Mw / Mn)>
The molecular weight distribution (Mw / Mn) by GPC of the polyethylene resin was measured under the following conditions.
Measuring instrument: Alliance GPC2000 type column manufactured by Waters: TSKgel GMH6-HT 2 TSKgel GMH6-HTL 2 [each inner diameter 7.5 mm × length 300 mm; manufactured by Tosoh Corporation]
Mobile phase: o-dichlorobenzene for high performance liquid chromatography (containing 0.025% BHT)
Column temperature: 140 ° C
Flow rate: 1.0 mL / min Sample concentration: 0.15% (W / V) o-dichlorobenzene Standard: Standard polystyrene (Shodex Standard; molecular weight = 7.30 × 10 6 , 3.85 × 10 6 , 2. 06 × 10 6 , 7.36 × 10 5 , 1.97 × 10 5 , 2.20 × 10 4 , 1.39 × 10 4 , 7.20 × 10 3 , 2.97 × 10 3 ), polystyrene A300 (Made by Shodex, molecular weight = 3.70 × 10 2 ) <10 types in total>.
　＜発泡倍率の測定＞
　６０℃で２時間乾燥し、温度２３℃、湿度５０％の室内で１時間静置した発泡粒子の重量ｗ（ｇ）を測定後、水没法にて体積ｖ（ｃｍ3）を測定し、発泡粒子の真比重ρｂ＝ｗ÷ｖを求め、発泡前のポリエチレン系樹脂粒子の密度ρｒとの比から発泡倍率Ｋ＝ρｒ÷ρｂを求めた。
なお、本実施例においては、発泡前のポリエチレン系樹脂粒子の密度としては、基材樹脂となる直鎖状低密度ポリエチレン系樹脂の密度を採用した。 <Measurement of expansion ratio>
After measuring the weight w (g) of the foamed particles dried at 60 ° C. for 2 hours and allowed to stand for 1 hour in a room at a temperature of 23 ° C. and a humidity of 50%, the volume v (cm 3 ) was measured by a submerged method. The true specific gravity ρb = w ÷ v of the particles was determined, and the expansion ratio K = ρr ÷ ρb was determined from the ratio to the density ρr of the polyethylene resin particles before foaming.
In this example, as the density of the polyethylene resin particles before foaming, the density of a linear low-density polyethylene resin serving as a base resin was employed.
　＜ゲル分率＞
　２００メッシュの金網袋中に、０．５ｇの直鎖状低密度ポリエチレン系樹脂、ポリエチレン系樹脂発泡粒子、またはポリエチレン系樹脂発泡粒子を入れて、該樹脂または粒子が袋の外に出ないように、金網の端を折り込む。
該金網袋を、大気圧下で沸騰させたキシレン５０ｍｌ中に３時間浸漬した後、冷却してキシレンから取り出す操作を、計３回行う。
取り出した金網袋を常温下で一晩乾燥させた後に、１５０℃のオーブン中で１時間乾燥させ、常温まで自然冷却させる。冷却後の金網袋内に残留した成分重量を測定して、ゲル成分重量とする。
ゲル分率（％）＝（ゲル成分重量／０．５）×１００の式により、ゲル分率を算出する。
なお、実施例および比較例記載のポリエチレン系樹脂発泡粒子のゲル分率は、いずれも１．０重量％以下であり、無架橋のポリエチレン系樹脂発泡粒子であった。 <Gel fraction>
In a 200 mesh wire mesh bag, 0.5 g of linear low density polyethylene resin, polyethylene resin expanded particles, or polyethylene resin expanded particles are put so that the resin or particles do not come out of the bag. Fold the end of the wire mesh.
The wire mesh bag is immersed in 50 ml of xylene boiled under atmospheric pressure for 3 hours, and then cooled and taken out from xylene three times in total.
The wire mesh bag taken out is dried overnight at room temperature, then dried in an oven at 150 ° C. for 1 hour, and then naturally cooled to room temperature. The weight of the component remaining in the wire mesh bag after cooling is measured to obtain the gel component weight.
The gel fraction is calculated by the formula: gel fraction (%) = (gel component weight / 0.5) × 100.
In addition, the gel fraction of the polyethylene-type resin expanded particle of an Example and a comparative example description was 1.0 weight% or less, and was a non-crosslinked polyethylene-based resin expanded particle.
　＜発泡粒子の平均気泡径の測定＞
得られた発泡粒子を、両刃カミソリ［フェザー製、ハイステンレス両刃］を用いて、発泡粒子の中央で切断した。該切断面を、光学顕微鏡［ＫＥＹＥＮＣＥ社製、マイクロスコープＶＨＸ－１００］を用いて、倍率５０倍にて観察して得られた画像において、発泡粒子のほぼ中心を通る直線を引き、該直線が貫通している気泡数ｎおよび、該直線と発泡粒子表面との交点から定まる発泡粒子径Ｌ（μｍ）を読み取り、式（１）によって求めた。
平均気泡径（μｍ）＝Ｌ／ｎ　・・・式（１）　　　。 <Measurement of average cell diameter of expanded particles>
The obtained foamed particles were cut at the center of the foamed particles using a double-edged razor [manufactured by Feather, high stainless steel double-edged]. In the image obtained by observing the cut surface with an optical microscope [manufactured by KEYENCE, microscope VHX-100] at a magnification of 50 times, a straight line passing through almost the center of the expanded particle is drawn, and the straight line is The number n of penetrating bubbles and the diameter L (μm) of the foamed particle determined from the intersection of the straight line and the surface of the foamed particle were read and obtained by the formula (1).
Average bubble diameter (μm) = L / n Formula (1).
　＜気泡径均一性＞
　発泡粒子断面を光学顕微鏡［ＫＥＹＥＮＣＥ社製、マイクロスコープＶＨＸ－１００］にて観察した際、発泡粒子断面の中央付近３０００μｍ×３０００μｍの領域内にある全気泡に関して、気泡径を測定して、平均気泡径±１５％以内である気泡の占める割合を求め、以下の基準にて、気泡径均一性（気泡径のバラツキ）を評価した。
なお、気泡径は、下記の方法にて測定する。
気泡内において最大の長さｄ1となる直線を引き、該直線の垂直二等分線と気泡との接点間距離ｄ2を求め、ｄ1とｄ2の平均値を気泡径とした。
ところで、上記領域内に気泡全体が入っていないもの、例えば気泡の半分だけ領域内に入っているような気泡については測定から除く。
○：気泡径が平均気泡径±１５％以内である気泡の占める割合が、全体の９０％以上である。　
△：気泡径が平均気泡径±１５％以内である気泡の占める割合が、全体の８０％以上９０％未満である。
×：気泡径が平均気泡径の±１５％以内である気泡の占める割合が、全体の８０％未満である。 <Bubble diameter uniformity>
When the cross section of the expanded particle was observed with an optical microscope [manufactured by KEYENCE, microscope VHX-100], the bubble diameter was measured for all the bubbles in the region of 3000 μm × 3000 μm near the center of the expanded particle cross section, and the average cell The ratio of bubbles within a diameter of ± 15% was determined, and the bubble diameter uniformity (bubble diameter variation) was evaluated according to the following criteria.
The bubble diameter is measured by the following method.
A straight line having the maximum length d 1 in the bubble was drawn, the distance d 2 between the contact points of the perpendicular bisector of the straight line and the bubble was determined, and the average value of d 1 and d 2 was taken as the bubble diameter.
By the way, what does not contain the whole bubble in the said area | region, for example, the bubble which is contained in the area | region only half of a bubble, is excluded from a measurement.
○: The ratio of the bubbles whose bubble diameter is within the average bubble diameter ± 15% is 90% or more of the whole.
(Triangle | delta): The ratio for which the bubble diameter is less than average bubble diameter +/- 15% is 80% or more and less than 90% of the whole.
X: The proportion of the bubbles whose bubble diameter is within ± 15% of the average bubble diameter is less than 80% of the total.
 ＜発泡粒子の連続気泡率＞
　得られたポリエチレン系樹脂発泡粒子に対して、ＡＳＴＭ　Ｄ２８５６－８７の手順Ｃ（ＰＲＯＳＥＤＵＲＥ　Ｃ）に記載の方法に従って、空気比較式比重計［東京サイエンス株式会社製、モデル１０００］を用いて、体積Ｖｃ（ｃｍ3）を測定した。
体積Ｖｃを測定したポリエチレン系樹脂発泡粒子の全量を、エタノールの入ったメスシリンダー内に沈め、メスシリンダーの液面上昇分（水没法）から、見かけ上の体積Ｖａ（ｃｍ3）を測定した。
ポリエチレン系樹脂発泡粒子の連続気泡率（％）は、下記式により算出した。
連続気泡率（％）＝（（Ｖａ－Ｖｃ）×１００）／Ｖａ　　　。 <Open cell ratio of expanded particles>
For the obtained polyethylene-based resin expanded particles, the volume Vc was measured using an air-comparing hydrometer [Model 1000] manufactured by Tokyo Science Co., Ltd. according to the method described in Procedure D (PROSEDURE C) of ASTM D2856-87. (Cm 3 ) was measured.
The total volume of the polyethylene resin expanded particles whose volume Vc was measured was submerged in a graduated cylinder containing ethanol, and the apparent volume Va (cm 3 ) was measured from the liquid level rise of the graduated cylinder (submerged method).
The open cell ratio (%) of the polyethylene resin expanded particles was calculated by the following formula.
Open cell ratio (%) = ((Va−Vc) × 100) / Va.
　＜発泡成形体の密度測定＞
　型内発泡成形により得られた発泡成形体を、７５～８０℃雰囲気下で２４時間乾燥させた後、温度２３℃、湿度５０％の室内で２４時間経過した発泡成形体の重量Ｗを測定する。発泡成形体を水中に水没させたときの体積変化Ｖを測定し、発泡成形体の密度＝Ｗ÷Ｖ（ｇ／Ｌ）を求めた。 <Density measurement of foam molding>
After the foam molded body obtained by in-mold foam molding is dried in an atmosphere of 75 to 80 ° C. for 24 hours, the weight W of the foam molded body after 24 hours in a room at a temperature of 23 ° C. and a humidity of 50% is measured. . The volume change V when the foamed molded product was submerged in water was measured, and the density of the foamed molded product = W ÷ V (g / L) was determined.
　＜成形時の蒸気圧力幅および適正蒸気圧力＞
　得られたポリエチレン系樹脂発泡粒子の水分を飛ばした後、長さ４００×幅３００×厚み５０ｍｍの成形空間を有する金型内に充填し、金型チャンバー内を蒸気にて１０秒間加熱した。その後、排気弁を閉めて１０秒間蒸気にて加熱（以下、「本加熱工程」と称す）することにより、発泡粒子同士を融着させた。続いて、金型内の蒸気を排気して、金型内および成形体表面を水冷した後、成形体を取り出して、ポリエチレン系樹脂発泡成形体を得た。
なお、本加熱工程の設定蒸気圧力を０．０８～０．１５ＭＰａ－Ｇの範囲内で、０．０１ＭＰａずつ変更して、成形を行った。ここで、本加熱工程での加熱時間１０秒のうち、設定圧力での保持時間は４秒であった。
得られた発泡成形体に対して、下記記載の融着性、対金型寸法収縮率、表面美麗性が全て合格レベル（後述する融着性、対金型寸法収縮率、表面美麗性評価において、○あるいは△のレベル）を満たす蒸気圧力を、「適正蒸気圧力幅」とした。
さらに、適正蒸気圧力幅の中において、融着性、対金型寸法収縮率、表面美麗性の３点において、最もバランスのとれた蒸気圧力を、「最適蒸気圧力」とした。
なお、成形時の蒸気圧力幅の評価は、以下の基準で評価した。
○：適正蒸気圧力幅が０．０３ＭＰａ以上。
△：適正蒸気圧力幅が０．０２ＭＰａ以上、０．０３ＭＰａ未満。
×：適正蒸気圧力幅が０．０２ＭＰａ未満。
（１）融着性
　得られた発泡成形体の中央付近にナイフなどで約５ｍｍの深さのクラックを入れた後、該クラックに沿って発泡成形体を割り、破断面を観察する。
破断面の全粒子数における破壊粒子数の割合を求めて、成形体融着率とし、以下の基準にて評価した。
○：融着率が８０％以上。
△：融着率が６０％以上８０％未満。
×：融着率が６０％未満。
（２）対金型寸法収縮率
　得られた発泡成形体の長手寸法（４００ｍｍ方向）を、デジタルノギス［Ｍｉｔｕｔｏｙｏ製］を用いて測定する。
対応する金型寸法をＬ0とし、発泡成形体の寸法をＬ1として、下記の式により、対金型寸法収縮率を算出し、以下の基準にて評価した。
対金型寸法収縮率＝（Ｌ0－Ｌ1）÷Ｌ0×１００
○：対金型寸法収縮率が３％以下。
△：対金型寸法収縮率が３％超、４％以下。
×：対金型寸法収縮率が４％超。
（３）表面美麗性
　得られた発泡成形体の端部を観察し、以下の基準にて評価した。
○：隣り合う発泡粒子同士がいずれの部分においても、きれいに融着しており、発泡粒子間に隙間がない。
△：隣り合う発泡粒子間に隙間がある箇所が、少し見られる。
×：隣り合う発泡粒子間に隙間がある箇所が、多数見られる。
なお、発泡成形体の端部とは、型内発泡成形体の面と面が交差する稜線部である。 <Vapor pressure range during molding and proper steam pressure>
After the moisture of the obtained polyethylene-based resin expanded particles was blown, the mold was filled in a mold having a molding space of length 400 × width 300 × thickness 50 mm, and the inside of the mold chamber was heated with steam for 10 seconds. Thereafter, the exhaust valve was closed and heated with steam for 10 seconds (hereinafter referred to as “main heating step”), thereby fusing the expanded particles. Subsequently, the vapor in the mold was evacuated, the inside of the mold and the surface of the molded body were water-cooled, and then the molded body was taken out to obtain a polyethylene resin foam molded body.
Molding was performed by changing the set steam pressure in this heating step by 0.01 MPa within a range of 0.08 to 0.15 MPa-G. Here, out of the heating time of 10 seconds in the main heating step, the holding time at the set pressure was 4 seconds.
For the obtained foamed molded article, the following fusing properties, dimensional shrinkage ratio against mold, and surface aesthetics are all acceptable levels (in the evaluation of fusion property, dimensional shrinkage ratio against mold, and surface aesthetics described later). , ○ or Δ level) was defined as “appropriate steam pressure range”.
Furthermore, within the appropriate steam pressure range, the most balanced steam pressure was determined as “optimum steam pressure” in terms of fusion property, mold dimensional shrinkage, and surface aesthetics.
The vapor pressure width at the time of molding was evaluated according to the following criteria.
○: The proper steam pressure width is 0.03 MPa or more.
Δ: The proper steam pressure width is 0.02 MPa or more and less than 0.03 MPa.
X: The proper steam pressure width is less than 0.02 MPa.
(1) Fusing property After a crack having a depth of about 5 mm is made in the vicinity of the center of the obtained foamed molded product with a knife or the like, the foamed molded product is broken along the crack and the fracture surface is observed.
The ratio of the number of broken particles to the total number of particles on the fracture surface was determined, and the molded product fusion rate was evaluated according to the following criteria.
○: The fusion rate is 80% or more.
Δ: The fusion rate is 60% or more and less than 80%.
X: The fusion rate is less than 60%.
(2) Mold size shrinkage ratio The longitudinal dimension (400 mm direction) of the obtained foamed molded article is measured using a digital caliper [manufactured by Mitutoyo].
The corresponding mold dimension was set to L 0, and the dimension of the foamed molded product was set to L 1 , and the mold shrinkage against the mold was calculated by the following formula and evaluated according to the following criteria.
Die dimensional shrinkage ratio = (L 0 −L 1 ) ÷ L 0 × 100
○: Shrinkage ratio against mold is 3% or less.
(Triangle | delta): Mold shrinkage ratio with respect to metal mold | dies exceeds 3%, and 4% or less.
X: Die size shrinkage ratio exceeds 4%.
(3) Surface beautifulness The edge part of the obtained foaming molding was observed, and the following references | standards evaluated.
○: Adjacent foamed particles are fused well in any part, and there is no gap between the foamed particles.
(Triangle | delta): The location with a clearance gap between adjacent expanded particles is seen a little.
X: Many places with gaps between adjacent expanded particles are seen.
In addition, the edge part of a foaming molding is a ridgeline part which the surface and surface of an in-mold foaming molding cross | intersect.
　（実施例１）
［ポリエチレン系樹脂粒子の作製］
　ポリエチレン系樹脂である直鎖状低密度ポリエチレン［共重合α－オレフィンとして４－メチル－１－ペンテン（以降、「４ＭＰ」と称する場合がある。）８．２重量％含有、樹脂密度０．９２６ｇ／ｃｍ3、ＭＦＲ＝２．１ｇ／１０分、Ｍｗ／Ｍｎ＝３．３、融点１２３℃、］１００重量部に対して、親水性化合物としてグリセリン［ライオン（株）製、精製グリセリンＤ］０．２重量部をドライブレンドした。ドライブレンドされた混合物を、５０ｍｍφ２軸押出機に投入し、樹脂温度２２０℃で溶融混練し、押出機の先端に取り付けられた円形ダイを通して、ストランド状に押出し、水冷後、カッターで切断して、一粒の重量が４．５ｍｇ／粒のポリエチレン系樹脂粒子を得た。
［ポリエチレン系樹脂発泡粒子の作製］
　容量０．３ｍ3の耐圧オートクレーブ中に、得られたポリエチレン系樹脂粒子１００重量部（７５ｋｇ）、水２００重量部、難水溶性無機化合物としての第三リン酸カルシウム［太平化学産業社製］０．５重量部、界面活性剤としてのアルキルスルホン酸ナトリウム［（株）花王製、ラテムルＰＳ］０．０３重量部を仕込んだ後、攪拌下、発泡剤として炭酸ガスを７重量部添加した。
オートクレーブ内容物を昇温し、１２３．８℃の発泡温度まで加熱した。その後、炭酸ガスを追加圧入して、オートクレーブ内圧を３．０ＭＰａ－Ｇの発泡圧力まで昇圧した。前記発泡温度および発泡圧力を３０分間保持した後、オートクレーブ下部のバルブを開き、直径４．０ｍｍφの開口オリフィス（１穴）を通して、オートクレーブ内容物を１００℃雰囲気下に放出して、ポリエチレン系樹脂発泡粒子（一段発泡粒子）を得た。
得られたポリエチレン系樹脂発泡粒子に関する評価結果を、表１に示す。
［ポリエチレン系樹脂型内発泡成形体の作製］
　得られたポリエチレン系樹脂発泡粒子（一段発泡粒子）の水分を飛ばした後、内圧を付与することなく、長さ４００×幅３００×厚み５０ｍｍの成形空間を有する金型内に充填し、金型チャンバー内を蒸気にて１０秒間加熱した。その後、排気弁を閉めて１０秒間蒸気にて加熱（以下、「本加熱工程」と称す）することにより、発泡粒子同士を融着させた。続いて、金型内の蒸気を排気し、金型内および成形体表面を水冷した後、成形体を取り出して、ポリエチレン系樹脂発泡成形体を得た。
なお、本加熱工程の設定蒸気圧力を０．０８～０．１５ＭＰａ－Ｇの範囲内で、０．０１ＭＰａずつ変更して、成形を行い、融着性、対金型寸法収縮率、表面美麗性を評価した。
ここで、本加熱工程での加熱時間１０秒のうち、設定圧力での保持時間は４秒であった。
得られたポリエチレン系樹脂型内発泡体に関する評価結果を、表１に示す。
なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１１ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Example 1)
[Preparation of polyethylene resin particles]
Linear low-density polyethylene which is a polyethylene resin [containing 4-8.2% by weight of 4-methyl-1-pentene as a copolymerized α-olefin (hereinafter sometimes referred to as “4MP”), resin density of 0.926 g / Cm 3 , MFR = 2.1 g / 10 min, Mw / Mn = 3.3, melting point 123 ° C.], 100 parts by weight of glycerin [manufactured by Lion Corporation, purified glycerin D] 0 2 parts by weight were dry blended. The dry blended mixture is put into a 50 mm φ twin screw extruder, melt kneaded at a resin temperature of 220 ° C., extruded into a strand through a circular die attached to the tip of the extruder, water cooled, and then cut with a cutter. Polyethylene resin particles having a weight of 4.5 mg / grain were obtained.
[Preparation of expanded polyethylene resin particles]
In a pressure resistant autoclave having a capacity of 0.3 m 3 , 100 parts by weight (75 kg) of the obtained polyethylene resin particles, 200 parts by weight of water, tricalcium phosphate as a poorly water-soluble inorganic compound [manufactured by Taihei Chemical Sangyo Co., Ltd.] 0.5 After adding 0.03 part by weight of sodium alkyl sulfonate as a surfactant [manufactured by Kao Corporation, Latemul PS], 7 parts by weight of carbon dioxide gas as a foaming agent was added under stirring.
The autoclave contents were warmed and heated to a foaming temperature of 123.8 ° C. Thereafter, carbon dioxide gas was additionally injected, and the internal pressure of the autoclave was increased to a foaming pressure of 3.0 MPa-G. After maintaining the foaming temperature and the foaming pressure for 30 minutes, the valve at the bottom of the autoclave is opened, and the autoclave contents are discharged into an atmosphere of 100 ° C. through an opening orifice (1 hole) having a diameter of 4.0 mmφ to foam a polyethylene resin. Particles (single-stage expanded particles) were obtained.
Table 1 shows the evaluation results regarding the obtained polyethylene-based resin expanded particles.
[Preparation of foamed molded product in polyethylene resin mold]
After the moisture of the obtained polyethylene-based resin foamed particles (single-stage foamed particles) is blown, the mold is filled into a mold having a molding space of length 400 × width 300 × thickness 50 mm without applying an internal pressure. The inside of the chamber was heated with steam for 10 seconds. Thereafter, the exhaust valve was closed and heated with steam for 10 seconds (hereinafter referred to as “main heating step”), thereby fusing the expanded particles. Subsequently, the vapor in the mold was evacuated and the mold and the surface of the molded body were cooled with water, and then the molded body was taken out to obtain a polyethylene resin foam molded body.
In addition, the set steam pressure in this heating process is changed within a range of 0.08 to 0.15MPa-G by 0.01MPa and molding is performed. Evaluated.
Here, out of the heating time of 10 seconds in the main heating step, the holding time at the set pressure was 4 seconds.
Table 1 shows the evaluation results regarding the obtained polyethylene resin-in-mold foam.
In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（実施例２）
［ポリエチレン系樹脂粒子の作製］
　実施例１と同様の操作により、ポリエチレン系樹脂粒子を得た。
［ポリエチレン系樹脂発泡粒子の作製］
　得られたポリエチレン系樹脂に対して、発泡温度を１２３．０℃に変更した以外は、実施例１と同様の操作により、一段発泡粒子を得た。
得られた一段発泡粒子の水分を飛ばした後、耐圧容器に入れ、空気で加圧して一段発泡粒子に空気を含浸し、０．２４ＭＰａ－Ｇの内圧を付与した。
次いで、内圧を付与した一段発泡粒子を予備発泡機に投入し、０．０６ＭＰａ－Ｇの蒸気と接触させることで二段発泡させ、二段発泡粒子を得た。
［ポリエチレン系樹脂型内発泡成形体の作製］
　得られた二段発泡粒子に対して、実施例１と同様の操作により、ポリエチレン系樹脂型内発泡体を得た。
一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体の評価結果を表１に示す。 (Example 2)
[Preparation of polyethylene resin particles]
Polyethylene resin particles were obtained by the same operation as in Example 1.
[Preparation of expanded polyethylene resin particles]
Single-stage expanded particles were obtained by the same operation as in Example 1 except that the foaming temperature was changed to 123.0 ° C. with respect to the obtained polyethylene resin.
After the water of the obtained first-stage expanded particles was blown, it was placed in a pressure vessel and pressurized with air to impregnate the first-stage expanded particles with air, and an internal pressure of 0.24 MPa-G was applied.
Next, the single-stage expanded particles to which the internal pressure was applied were put into a pre-expanding machine and brought into two-stage expansion by contacting with 0.06 MPa-G vapor to obtain two-stage expanded particles.
[Preparation of foamed molded product in polyethylene resin mold]
For the obtained two-stage expanded particles, a polyethylene resin internal foam was obtained by the same operation as in Example 1.
Table 1 shows the evaluation results of the first-stage expanded particles, the second-stage expanded particles, and the polyethylene resin-in-mold foam.
　（実施例３）
［ポリエチレン系樹脂発泡粒子の作製］において、直鎖状低密度ポリエチレン系樹脂として、４ＭＰ含有量５．３重量％、樹脂密度０．９３１ｇ／ｃｍ3、ＭＦＲ＝２．４ｇ／１０分、Ｍｗ／Ｍｎ＝４．４、融点１２４℃の直鎖状低密度ポリエチレンを使用した以外は、表１記載の条件にて実施例２と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表１に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１１ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Example 3)
In [Preparation of polyethylene resin expanded particles], as a linear low density polyethylene resin, 4MP content 5.3 wt%, resin density 0.931 g / cm 3 , MFR = 2.4 g / 10 min, Mw / Except for using linear low density polyethylene with Mn = 4.4 and melting point of 124 ° C., the same operation as in Example 2 was carried out under the conditions described in Table 1, and one-stage expanded particles, two-stage expanded particles, and a polyethylene series A resin foam molding was obtained.
Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam. In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（実施例４）
　［ポリエチレン系樹脂発泡粒子の作製］において、直鎖状低密度ポリエチレン系樹脂として、４ＭＰ含有量５．１重量％、樹脂密度０．９３３ｇ／ｃｍ3、ＭＦＲ＝２．３ｇ／１０分、Ｍｗ／Ｍｎ＝４．８、融点１２４℃の直鎖状低密度ポリエチレンを使用した以外は、表１記載の条件にて実施例２と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表１に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１１ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Example 4)
In [Preparation of Polyethylene Resin Expanded Particles], as a linear low density polyethylene resin, 4MP content 5.1 wt%, resin density 0.933 g / cm 3 , MFR = 2.3 g / 10 min, Mw / Except for using linear low density polyethylene with Mn = 4.8 and melting point of 124 ° C., the same operation as in Example 2 was carried out under the conditions described in Table 1, and one-stage expanded particles, two-stage expanded particles, and a polyethylene series A resin foam molding was obtained.
Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam. In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（実施例５）
　［ポリエチレン系樹脂発泡粒子の作製]において、直鎖状低密度ポリエチレン系樹脂として、４ＭＰ含有量９．１重量％、樹脂密度０．９２３ｇ／ｃｍ3、ＭＦＲ＝１．２ｇ／１０分、Ｍｗ／Ｍｎ＝４．３、融点１２２℃の直鎖状低密度ポリエチレンを使用し、発泡温度を１２２．０℃に変更した以外は、表１記載の条件にて実施例２と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表１に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１１ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Example 5)
In [Production of polyethylene-based resin expanded particles], as a linear low-density polyethylene-based resin, a 4MP content of 9.1% by weight, a resin density of 0.923 g / cm 3 , MFR = 1.2 g / 10 min, Mw / The same operation as in Example 2 was performed under the conditions described in Table 1, except that linear low density polyethylene having a Mn = 4.3 and a melting point of 122 ° C. was used and the foaming temperature was changed to 122.0 ° C. Single-stage expanded particles, double-stage expanded particles and a polyethylene-based resin foam molded article were obtained.
Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam. In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（実施例６）
　［ポリエチレン系樹脂発泡粒子の作製]において、直鎖状低密度ポリエチレン系樹脂として、４ＭＰ含有量３．９重量％、樹脂密度０．９３７ｇ／ｃｍ3、ＭＦＲ＝４．３ｇ／１０分、Ｍｗ／Ｍｎ＝３．４、融点１２７℃の直鎖状低密度ポリエチレンを使用し、発泡温度を１２７．０℃に変更した以外は、表１記載の条件にて実施例２と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表１に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１１ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Example 6)
In [Production of polyethylene-based resin expanded particles], the linear low-density polyethylene-based resin has a 4MP content of 3.9% by weight, a resin density of 0.937 g / cm 3 , MFR = 4.3 g / 10 min, Mw / The same operation as in Example 2 was performed under the conditions described in Table 1, except that linear low density polyethylene having a Mn = 3.4 and a melting point of 127 ° C. was used and the foaming temperature was changed to 127.0 ° C. Single-stage expanded particles, double-stage expanded particles and a polyethylene-based resin foam molded article were obtained.
Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam. In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（実施例７）
　［ポリエチレン系樹脂発泡粒子の作製］において、親水性化合物を使用しなかった以外は、表１記載の条件にて実施例２と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表１に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１１ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Example 7)
In [Production of polyethylene-based resin expanded particles], the same operation as in Example 2 was carried out under the conditions described in Table 1 except that the hydrophilic compound was not used. A resin foam molding was obtained.
Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam. In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（実施例８～９）
　［ポリエチレン系樹脂発泡粒子の作製］において、親水性化合物の種類・量を、それぞれ、ポリエチレングリコール［ライオン（株）製、ＰＥＧ３００］０．５重量部、メラミン［日産化学工業（株）製］０．２重量部に変更した以外は、表１記載の条件にて実施例２と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表１に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１１ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Examples 8 to 9)
In [Preparation of polyethylene resin expanded particles], the types and amounts of the hydrophilic compounds are respectively 0.5 parts by weight of polyethylene glycol [manufactured by Lion Corporation, PEG300], melamine [manufactured by Nissan Chemical Industries, Ltd.] 0 Except for the change to 2 parts by weight, the same operations as in Example 2 were performed under the conditions described in Table 1, and single-stage expanded particles, double-stage expanded particles, and a polyethylene-based resin foam molded article were obtained.
Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam. In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（実施例１０）
［ポリエチレン系樹脂粒子の作製］
　直鎖状低密度ポリエチレン系樹脂１００重量部に対して、さらに、タルク［林化成（株）製、タルカンパウダーＰＫ－Ｓ］０．１重量部、帯電防止剤としてモノグリセリド［理研ビタミン（株）製、リケマールＳ－１００Ａ］１．０重量部をドライブレンドした以外は、実施例１と同様の操作を行い、１．３ｍｇ／粒のポリエチレン系樹脂粒子を得た。
［ポリエチレン系樹脂発泡粒子の作製］および［ポリエチレン系樹脂型内発泡体の作製］においては、実施例２と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表１に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１１ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Example 10)
[Preparation of polyethylene resin particles]
For 100 parts by weight of linear low density polyethylene resin, talc [manufactured by Hayashi Kasei Co., Ltd., Talcan powder PK-S] 0.1 parts by weight, monoglyceride as an antistatic agent [manufactured by Riken Vitamin Co., Ltd. , Riquemar S-100A] Except for dry blending 1.0 part by weight, the same operation as in Example 1 was performed to obtain 1.3 mg / grain of polyethylene resin particles.
In [Production of polyethylene-based resin foamed particles] and [Production of polyethylene-based resin-in-mold foam], the same operation as in Example 2 was performed to obtain one-stage foamed particles, two-stage foamed particles, and a polyethylene-based resin foam molded article. Obtained.
Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam. In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（実施例１１）
［ポリエチレン系樹脂発泡粒子の作製］において、直鎖状低密度ポリエチレン系樹脂１００重量部に対して、さらに、タルク［林化成（株）製、タルカンパウダーＰＫ－Ｓ］０．１重量部、帯電防止剤としてモノグリセリド［理研ビタミン（株）製、リケマールＳ－１００Ａ］０．５重量部、着色剤としてカーボンブラック［ＣＡＢＯＴ製、Ｎ３３０］１．０重量部をドライブレンドした以外は、実施例１と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表１に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１１ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Example 11)
In [Preparation of polyethylene resin foamed particles], 0.1 part by weight of talc [manufactured by Hayashi Kasei Co., Ltd., Talcan Powder PK-S] is further added to 100 parts by weight of the linear low density polyethylene resin. Example 1 except that 0.5 parts by weight of a monoglyceride [manufactured by Riken Vitamin Co., Ltd., Riquemar S-100A] as an inhibitor and 1.0 part by weight of carbon black [manufactured by CABOT, N330] as a colorant were dry blended. The same operation was performed to obtain one-stage expanded particles, two-stage expanded particles, and a polyethylene resin foam molded article.
Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam. In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（実施例１２）
　[ポリエチレン系樹脂発泡粒子の作製]において、直鎖状低密度ポリエチレン系樹脂として、共重合α－オレフィンとして１－ヘキセン７．４重量％含有、樹脂密度０．９２８ｇ／ｃｍ3、ＭＦＲ＝１．７ｇ／１０分、Ｍｗ／Ｍｎ＝３．５、融点１２３℃の直鎖状低密度ポリエチレンを使用し、発泡温度を１２３．１℃に変更した以外は、表１記載の条件にて実施例２と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表１に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１２ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 Example 12
In [Preparation of Polyethylene Resin Expanded Particles], the linear low density polyethylene resin contains 7.4% by weight of 1-hexene as a copolymerized α-olefin, the resin density is 0.928 g / cm 3 , and MFR = 1. Example 2 under the conditions described in Table 1 except that linear low-density polyethylene having 7 g / 10 min, Mw / Mn = 3.5, melting point 123 ° C. was used, and the foaming temperature was changed to 123.1 ° C. The same operation was carried out to obtain one-stage expanded particles, two-stage expanded particles and a polyethylene resin foam molded article.
Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam. The molded body evaluations (fusing property, mold dimensional stability, surface aesthetics) in the table were obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.12 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（実施例１３）
　[ポリエチレン系樹脂発泡粒子の作製]において、直鎖状低密度ポリエチレン系樹脂として、共重合α－オレフィンとして１－オクテン２．８重量％含有、樹脂密度０．９３８ｇ／ｃｍ3、ＭＦＲ＝２．１ｇ／１０分、Ｍｗ／Ｍｎ＝３．４、融点１２４℃の直鎖状低密度ポリエチレンを使用し、発泡温度を１２３．９℃に変更した以外は、表１記載の条件にて実施例２と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表１に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１２ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Example 13)
In [Preparation of Polyethylene Resin Expanded Particles], a linear low density polyethylene resin containing 2.8% by weight of 1-octene as a copolymerized α-olefin, a resin density of 0.938 g / cm 3 , MFR = 2. Example 2 under the conditions described in Table 1 except that linear low-density polyethylene having 1 g / 10 min, Mw / Mn = 3.4, melting point 124 ° C. was used, and the foaming temperature was changed to 123.9 ° C. The same operation was carried out to obtain one-stage expanded particles, two-stage expanded particles and a polyethylene resin foam molded article.
Table 1 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene-based resin-in-mold foam. The molded body evaluations (fusing property, mold dimensional stability, surface aesthetics) in the table were obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.12 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（実施例１４）
［ポリエチレン系樹脂粒子の作製］
　実施例１と同様の操作により、ポリエチレン系樹脂粒子を得た。
［ポリエチレン系樹脂発泡粒子の作製］
　得られたポリエチレン系樹脂粒子に対して、発泡剤としてイソブタンを２５重量部添加し、１１９．０℃の発泡温度まで加熱した後、イソブタンを追加圧入して、オートクレーブ内圧を１．６ＭＰａ－Ｇの発泡圧力まで昇圧した以外は、実施例１と同様の操作により、一段発泡粒子を得た。
［ポリエチレン系樹脂型内発泡成形体の作製］
　得られた一段発泡粒子に対して、表１記載の条件にて実施例１と同様の操作により、ポリエチレン系樹脂型内発泡体を得た。
一段発泡粒子およびポリエチレン系樹脂型内発泡体の評価結果を、表１に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１１ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Example 14)
[Preparation of polyethylene resin particles]
Polyethylene resin particles were obtained by the same operation as in Example 1.
[Preparation of expanded polyethylene resin particles]
After adding 25 parts by weight of isobutane as a foaming agent to the obtained polyethylene-based resin particles and heating to a foaming temperature of 119.0 ° C., isobutane was additionally injected, and the internal pressure of the autoclave was 1.6 MPa-G. Single-stage expanded particles were obtained in the same manner as in Example 1 except that the pressure was increased to the expansion pressure.
[Preparation of foamed molded product in polyethylene resin mold]
For the resulting single-stage expanded particles, a polyethylene resin-in-mold foam was obtained by the same operation as in Example 1 under the conditions described in Table 1.
Table 1 shows the evaluation results of the first-stage expanded particles and the polyethylene resin-in-mold foam. In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　（比較例１）
［ポリエチレン系樹脂発泡粒子の作製］において、直鎖状低密度ポリエチレン系樹脂として、４ＭＰ含有量６．２重量％、樹脂密度０．９２６ｇ／ｃｍ3、ＭＦＲ＝１．９ｇ／１０分、Ｍｗ／Ｍｎ＝２．４、融点１２３℃の直鎖状低密度ポリエチレンを使用した以外は、表２記載の条件にて実施例２と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表２に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１１ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Comparative Example 1)
In [Preparation of Polyethylene Resin Expanded Particles], as a linear low density polyethylene resin, the content of 4MP is 6.2% by weight, the resin density is 0.926 g / cm 3 , MFR = 1.9 g / 10 min, Mw / Except for using a linear low density polyethylene having a Mn = 2.4 and a melting point of 123 ° C., the same operation as in Example 2 was carried out under the conditions described in Table 2, and one-stage expanded particles, two-stage expanded particles and a polyethylene series A resin foam molding was obtained.
Table 2 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene resin-in-mold foam. In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（比較例２）
［ポリエチレン系樹脂発泡粒子の作製］において、直鎖状低密度ポリエチレン系樹脂として、４ＭＰ含有量６．０重量％、樹脂密度０．９２０ｇ／ｃｍ3、ＭＦＲ＝１．１ｇ／１０分、Ｍｗ／Ｍｎ＝５．３、融点１２０℃の直鎖状低密度ポリエチレンを使用し、発泡温度を１２０．０℃に変更した以外は、表２記載の条件にて実施例２と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表２に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１１ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Comparative Example 2)
In [Production of polyethylene resin expanded particles], as a linear low density polyethylene resin, the content of 4MP is 6.0% by weight, the resin density is 0.920 g / cm 3 , MFR = 1.1 g / 10 min, Mw / The same operation as in Example 2 was performed under the conditions described in Table 2 except that linear low density polyethylene having a Mn = 5.3 and a melting point of 120 ° C. was used and the foaming temperature was changed to 120.0 ° C. Single-stage expanded particles, double-stage expanded particles and a polyethylene-based resin foam molded article were obtained.
Table 2 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene resin-in-mold foam. In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（比較例３）
［ポリエチレン系樹脂発泡粒子の作製］において、直鎖状低密度ポリエチレン系樹脂として、共重合α－オレフィンとして１－ブテン５．２重量％含有、樹脂密度０．９２０ｇ／ｃｍ3、ＭＦＲ＝０．８ｇ／１０分、Ｍｗ／Ｍｎ＝１７．３、融点１１７℃の直鎖状低密度ポリエチレンを使用し、発泡温度を１１７．０℃に変更した以外は、表２記載の条件にて実施例２と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表２に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１０ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Comparative Example 3)
In [Production of polyethylene resin expanded particles], the linear low-density polyethylene resin contains 5.2% by weight of 1-butene as a copolymerized α-olefin, the resin density is 0.920 g / cm 3 , and MFR = 0. Example 2 under the conditions described in Table 2 except that linear low density polyethylene having 8 g / 10 min, Mw / Mn = 17.3, melting point 117 ° C. was used and the foaming temperature was changed to 117.0 ° C. The same operation was carried out to obtain one-stage expanded particles, two-stage expanded particles and a polyethylene resin foam molded article.
Table 2 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene resin-in-mold foam. The molded body evaluations in the table (fusing property, dimensional stability against mold, and surface aesthetics) were obtained by in-mold foam molding at an optimum vapor pressure (vapor pressure of 0.10 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（比較例４）
［ポリエチレン系樹脂発泡粒子の作製］において、直鎖状低密度ポリエチレン系樹脂として、共重合α－オレフィンとして１－ブテン０．７３重量％含有、樹脂密度０．９３６ｇ／ｃｍ3、ＭＦＲ＝３．１ｇ／１０分、Ｍｗ／Ｍｎ＝２．２、融点１２６℃の直鎖状低密度ポリエチレンを使用し、発泡温度を１２６．０℃に変更した以外は、実施例２と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表２に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１３ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Comparative Example 4)
In [Production of polyethylene resin expanded particles], the linear low density polyethylene resin contains 0.73% by weight of 1-butene as a copolymerized α-olefin, the resin density is 0.936 g / cm 3 , and MFR = 3. 1 g / 10 minutes, Mw / Mn = 2.2, using a linear low density polyethylene having a melting point of 126 ° C., and performing the same operation as in Example 2 except that the foaming temperature was changed to 126.0 ° C. Single-stage expanded particles, double-stage expanded particles and a polyethylene-based resin foam molded article were obtained.
Table 2 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene resin-in-mold foam. The molded body evaluations (fusing property, dimensional stability against mold, and surface aesthetics) in the table were obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.13 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（比較例５）
［ポリエチレン系樹脂発泡粒子の作製］において、直鎖状低密度ポリエチレン系樹脂として、４ＭＰ含有量４．９重量％、樹脂密度０．９４８ｇ／ｃｍ3、ＭＦＲ＝４．０ｇ／１０分、Ｍｗ／Ｍｎ＝４．１、融点１２８℃の高密度ポリエチレンを使用し、発泡温度を１２８．０℃に変更した以外は、表２記載の条件にて実施例２と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表２に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１３ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Comparative Example 5)
In [Production of polyethylene resin expanded particles], as a linear low density polyethylene resin, 4MP content 4.9% by weight, resin density 0.948 g / cm 3 , MFR = 4.0 g / 10 min, Mw / One-stage foamed particles were prepared in the same manner as in Example 2 under the conditions shown in Table 2, except that high-density polyethylene with Mn = 4.1 and melting point 128 ° C. was used and the foaming temperature was changed to 128.0 ° C. Two-stage expanded particles and a polyethylene resin expanded foam were obtained.
Table 2 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene resin-in-mold foam. The molded body evaluations (fusing property, dimensional stability against mold, and surface aesthetics) in the table were obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.13 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（比較例６）
［ポリエチレン系樹脂発泡粒子の作製］において、直鎖状低密度ポリエチレン系樹脂として、共重合α－オレフィンとして１－オクテン５．３重量％含有、樹脂密度０．９１７ｇ／ｃｍ3、ＭＩ＝６．０ｇ／１０分、Ｍｗ／Ｍｎ＝３．４、融点１２３℃の直鎖状低密度ポリエチレンを使用した以外は、表２記載の条件にて実施例２と同様の操作を行い、一段発泡粒子を得た。
得られた一段発泡粒子を表２記載の条件で二段発泡したが、発泡粒子の気泡が破れて連続気泡率が高くなり、発泡倍率が低下した二段発泡粒子となった為、型内発泡成形は中止した。 (Comparative Example 6)
In [Preparation of Polyethylene Resin Expanded Particles], the linear low density polyethylene resin contains 5.3% by weight of 1-octene as a copolymerized α-olefin, the resin density is 0.917 g / cm 3 , MI = 6. The same procedure as in Example 2 was carried out under the conditions described in Table 2 except that a linear low density polyethylene having 0 g / 10 minutes, Mw / Mn = 3.4, and a melting point of 123 ° C. was used. Obtained.
The resulting single-stage expanded particles were two-stage expanded under the conditions shown in Table 2, but the foamed particles were broken to increase the open-cell ratio, resulting in two-stage expanded particles with a reduced expansion ratio. Molding was stopped.
　（比較例７）
［ポリエチレン系樹脂発泡粒子の作製］において、発泡温度を１２０．３℃に変更した以外は、実施例７と同様の操作により、一段発泡粒子を得た。
［ポリエチレン系樹脂型内発泡成形体の作製］
　得られたポリエチレン系樹脂発泡粒子（一段発泡粒子）に対して、実施例１と同様の操作により、ポリエチレン系樹脂型内発泡体を得た。
一段発泡粒子およびポリエチレン系樹脂型内発泡体の評価結果を、表２に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１１ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Comparative Example 7)
In [Production of polyethylene resin expanded particles], single-stage expanded particles were obtained in the same manner as in Example 7, except that the expansion temperature was changed to 120.3 ° C.
[Preparation of foamed molded product in polyethylene resin mold]
The obtained polyethylene-based resin expanded particles (single-stage expanded particles) were subjected to the same operation as in Example 1 to obtain a polyethylene-based resin in-mold foam.
Table 2 shows the evaluation results of the first-stage expanded particles and the polyethylene resin-in-mold foam. In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（比較例８）
［ポリエチレン系樹脂発泡粒子の作製］において、直鎖状低密度ポリエチレン系樹脂として、共重合α－オレフィンとして１－ブテン４．３重量％含有、樹脂密度０．９２５ｇ／ｃｍ3、ＭＦＲ＝２．０ｇ／１０分、Ｍｗ／Ｍｎ＝３．５、融点１２１℃の直鎖状低密度ポリエチレンを使用し、発泡温度を１２１．３℃に変更した以外は、表２記載の条件にて実施例２と同様の操作を行い、一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂発泡成形体を得た。
得られた一段発泡粒子、二段発泡粒子およびポリエチレン系樹脂型内発泡体に関する評価結果を、表２に示す。なお、表中の成形体評価（融着性、対金型寸法安定性、表面美麗性）は、最適蒸気圧力（０．１１ＭＰａ－Ｇの蒸気圧力）で、型内発泡成形して得られたポリエチレン系樹脂型内発泡体に関するものである。 (Comparative Example 8)
In [Preparation of Polyethylene Resin Expanded Particles], the linear low density polyethylene resin contains 4.3% by weight of 1-butene as a copolymerized α-olefin, the resin density is 0.925 g / cm 3 , and MFR = 2. Example 2 under the conditions described in Table 2 except that linear low-density polyethylene having 0 g / 10 min, Mw / Mn = 3.5, melting point 121 ° C. was used, and the foaming temperature was changed to 121.3 ° C. The same operation was carried out to obtain one-stage expanded particles, two-stage expanded particles and a polyethylene resin foam molded article.
Table 2 shows the evaluation results regarding the obtained one-stage expanded particles, two-stage expanded particles, and the polyethylene resin-in-mold foam. In addition, the molded body evaluation (fusing property, dimensional stability against mold, and surface aesthetics) in the table was obtained by in-mold foam molding at the optimum vapor pressure (vapor pressure of 0.11 MPa-G). The present invention relates to a foam in a polyethylene resin mold.
　（比較例９）
［ポリエチレン系樹脂粒子の作製］
実施例７と同様の操作を行い、親水性化合物を含有しないポリエチレン系樹脂粒子を得た。
［ポリエチレン系樹脂発泡粒子の作製］
容量０．３ｍ3の耐圧オートクレーブ中に、得られたポリエチレン系樹脂粒子１００重量部（７５ｋｇ）、水２５０重量部、難水溶性無機化合物としての第三リン酸カルシウム［太平化学産業社製］４．０重量部、界面活性剤としてのアルキルスルホン酸ナトリウム［（株）花王製、ラテムルＰＳ］０．８重量部を仕込んだ後、攪拌下、１．５ＭＰａ－Ｇまで窒素ガスを圧入した。その後、オートクレーブ内容物を昇温し、１２５．０℃の発泡温度まで加熱した。この時、オートクレーブ内圧は２．２ＭＰａ－Ｇであった。この状態で３０分間保持した後、窒素ガスを追加圧入して、オートクレーブ内圧を３．５ＭＰａ－Ｇの発泡圧力まで昇圧した。その後、オートクレーブ下部のバルブを開き、直径４．０ｍｍφの開口オリフィス（１穴）を通して、オートクレーブ内容物を１００℃雰囲気下に放出して、一段発泡粒子を得た。
得られた一段発泡粒子を表２記載の条件で二段発泡したが、発泡粒子の気泡が破れて連続気泡率が高くなり、発泡倍率が低下した二段発泡粒子となった為、型内発泡成形は中止した。 (Comparative Example 9)
[Preparation of polyethylene resin particles]
The same operation as in Example 7 was performed to obtain polyethylene resin particles containing no hydrophilic compound.
[Preparation of expanded polyethylene resin particles]
In a pressure resistant autoclave having a capacity of 0.3 m 3 , 100 parts by weight (75 kg) of the obtained polyethylene resin particles, 250 parts by weight of water, and tribasic calcium phosphate as a sparingly water-soluble inorganic compound [made by Taihei Chemical Industry Co., Ltd.] 4.0 After charging 0.8 parts by weight of sodium alkyl sulfonate [La Kamul PS, manufactured by Kao Corporation] as a surfactant, nitrogen gas was injected under pressure to 1.5 MPa-G with stirring. Thereafter, the autoclave contents were heated and heated to a foaming temperature of 125.0 ° C. At this time, the internal pressure of the autoclave was 2.2 MPa-G. After maintaining in this state for 30 minutes, nitrogen gas was additionally injected to increase the internal pressure of the autoclave to a foaming pressure of 3.5 MPa-G. Then, the valve | bulb of the autoclave lower part was opened, the autoclave content was discharge | released in 100 degreeC atmosphere through the opening orifice (1 hole) of diameter 4.0mm (phi), and the 1st stage | paragraph expanded particle was obtained.
The resulting single-stage expanded particles were two-stage expanded under the conditions shown in Table 2, but the foamed particles were broken to increase the open-cell ratio, resulting in two-stage expanded particles with a reduced expansion ratio. Molding was stopped.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　本発明のポリエチレン系樹脂発泡粒子によれば、成形時に良好な成形体が得られる蒸気圧力の幅が広く、対金型寸法収縮率が小さく、表面が美麗なポリエチレン系樹脂発泡成形体を簡便に得ることができる。得られるポリエチレン系樹脂発泡成形体は、緩衝包装材、断熱材、等として種々の用途に利用されている。 According to the polyethylene resin foamed particles of the present invention, a polyethylene resin foam molded article having a wide vapor pressure range, a small mold dimensional shrinkage ratio, and a beautiful surface can be easily obtained. Obtainable. The obtained polyethylene-based resin foam molded article is used for various applications as a buffer packaging material, a heat insulating material, and the like.

Claims (8)

  1. 　次の（ａ）～（ｄ）の条件を満たす直鎖状低密度ポリエチレン系樹脂を基材樹脂とするポリエチレン系樹脂粒子を発泡させて得られるポリエチレン系樹脂発泡粒子であって、
    平均気泡径が２００μｍ以上７００μｍ以下、かつ、連続気泡率が１２％以下であることを特徴とする、ポリエチレン系樹脂発泡粒子。
    （ａ）直鎖状低密度ポリエチレン系樹脂がエチレンと、炭素数６および／または８のα－オレフィンとの共重合体である。
    （ｂ）密度が０．９２０ｇ／ｃｍ3以上０．９４０ｇ／ｃｍ3未満である。
    （ｃ）メルトフローレート（ＭＦＲ）が０．１ｇ／１０分以上５．０ｇ／１０分以下である。
    （ｄ）ゲル・パーミエーション・クロマトグラフ（ＧＰＣ）により測定される分子量分布（Ｍｗ／Ｍｎ）が３以上５未満である。     Polyethylene resin foam particles obtained by foaming polyethylene resin particles having a linear low density polyethylene resin satisfying the following conditions (a) to (d) as a base resin,
    A polyethylene-based resin expanded particle having an average cell diameter of 200 μm or more and 700 μm or less and an open cell ratio of 12% or less.
    (A) The linear low density polyethylene resin is a copolymer of ethylene and an α-olefin having 6 and / or 8 carbon atoms.
    (B) The density is 0.920 g / cm 3 or more and less than 0.940 g / cm 3 .
    (C) The melt flow rate (MFR) is 0.1 g / 10 min or more and 5.0 g / 10 min or less.
    (D) The molecular weight distribution (Mw / Mn) measured by gel permeation chromatograph (GPC) is 3 or more and less than 5.
  2. 　平均気泡径が３００μｍ以上６００μｍ以下であることを特徴とする、請求項１に記載のポリエチレン系樹脂発泡粒子。 The polyethylene resin expanded particles according to claim 1, wherein the average cell diameter is 300 μm or more and 600 μm or less.
  3. 　気泡径が平均気泡径±１５％以内である気泡の占める割合が、発泡粒子全体に対して８０％以上であることを特徴とする、請求項１または２記載のポリエチレン系樹脂発泡粒子。 3. The polyethylene resin foamed particles according to claim 1 or 2, wherein the ratio of the bubbles having a bubble diameter within an average cell diameter of ± 15% is 80% or more with respect to the whole foamed particles.
  4. 　基材樹脂が、直鎖状低密度ポリエチレン系樹脂１００重量部に対して、親水性化合物を０．０１重量部以上１０重量部以下含有することを特徴とする、請求項１～３の何れか１項に記載のポリエチレン系樹脂発泡粒子。 The base resin contains 0.01 to 10 parts by weight of a hydrophilic compound with respect to 100 parts by weight of a linear low-density polyethylene-based resin. 2. The polyethylene resin expanded particles according to item 1.
  5. 　親水性化合物が、グリセリン、ポリエチレングリコールおよびメラミンよりなる群から選ばれる少なくとも１種であることを特徴とする、請求項４記載のポリエチレン系樹脂発泡粒子。 The polyethylene resin expanded particles according to claim 4, wherein the hydrophilic compound is at least one selected from the group consisting of glycerin, polyethylene glycol and melamine.
  6. 　直鎖状低密度ポリエチレン系樹脂１００重量部に対して、グリセリン、ポリエチレングリコールおよびメラミンよりなる群から選ばれる少なくとも１種を０．１重量部以上２重量部以下含有することを特徴とする、請求項５記載のポリエチレン系樹脂発泡粒子。 It is characterized by containing at least one selected from the group consisting of glycerin, polyethylene glycol and melamine with respect to 100 parts by weight of a linear low density polyethylene-based resin in an amount of 0.1 parts by weight or more and 2 parts by weight or less. Item 6. The polyethylene resin expanded particles according to Item 5.
  7. 　請求項１～６の何れか１項記載のポリエチレン系樹脂発泡粒子を、金型内に充填した後、型内発泡成形して得られることを特徴とする、ポリエチレン系樹脂発泡成形体。 A polyethylene-based resin foam molded article obtained by filling the polyethylene-based resin expanded particles according to any one of claims 1 to 6 into a mold and then performing in-mold foam molding.
  8. 　次の（ａ）～（ｄ）の条件を満たす直鎖状低密度ポリエチレン系樹脂を基材樹脂とするポリエチレン系樹脂粒子を、水、炭酸ガスを含む発泡剤、および分散剤と共に耐圧容器内に導入し、耐圧容器内を昇温、昇圧して保持した後、直鎖状低密度ポリエチレン系樹脂粒子を耐圧容器内より低圧雰囲気下に放出して一段発泡粒子を得る工程、
    次いで、一段発泡粒子を加圧タンク内に入れ、無機ガスで加圧することにより一段発泡粒子内に空気を導入して、発泡粒子の内圧を大気圧より高めた後、一段発泡粒子を水蒸気で加熱して二段発泡粒子を得る工程、
    を経ることを特徴とする、
    平均気泡径が２００μｍ以上、７００μｍ以下、かつ、連続気泡率が１２％以下であるポリエチレン系樹脂発泡粒子の製造方法。
    （ａ）直鎖状低密度ポリエチレン系樹脂がエチレンと、炭素数６および／または８のα－オレフィンとの共重合体である。
    （ｂ）密度が０．９２０ｇ／ｃｍ3以上０．９４０ｇ／ｃｍ3未満である。
    （ｃ）メルトフローレート（ＭＦＲ）が０．１ｇ／１０分以上５．０ｇ／１０分以下である。
    （ｄ）ゲル・パーミエーション・クロマトグラフ（ＧＰＣ）により測定される分子量分布（Ｍｗ／Ｍｎ）が３以上５未満である。     Polyethylene resin particles based on a linear low density polyethylene resin satisfying the following conditions (a) to (d) are placed in a pressure vessel together with water, a blowing agent containing carbon dioxide gas, and a dispersing agent. Introducing, holding the temperature inside the pressure vessel by raising the temperature, raising the pressure, releasing the linear low density polyethylene resin particles from the inside of the pressure vessel in a low pressure atmosphere to obtain single-stage expanded particles,
    Next, the first-stage expanded particles are placed in a pressurized tank, and air is introduced into the first-stage expanded particles by pressurizing with an inorganic gas to increase the internal pressure of the expanded particles from atmospheric pressure, and then the first-stage expanded particles are heated with water vapor. To obtain two-stage expanded particles,
    It is characterized by going through the
    A method for producing expanded polyethylene resin particles having an average cell diameter of 200 μm or more and 700 μm or less and an open cell ratio of 12% or less.
    (A) The linear low density polyethylene resin is a copolymer of ethylene and an α-olefin having 6 and / or 8 carbon atoms.
    (B) The density is 0.920 g / cm 3 or more and less than 0.940 g / cm 3 .
    (C) The melt flow rate (MFR) is 0.1 g / 10 min or more and 5.0 g / 10 min or less.
    (D) The molecular weight distribution (Mw / Mn) measured by gel permeation chromatograph (GPC) is 3 or more and less than 5.
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WO2023067954A1 (en) 2021-10-21 2023-04-27 株式会社ジェイエスピー Polyethylene resin foam particles, and method for producing same
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WO2014136933A1 (en) * 2013-03-08 2014-09-12 株式会社カネカ Method for manufacturing foamed polypropylene-resin particles
JPWO2014136933A1 (en) * 2013-03-08 2017-02-16 株式会社カネカ Method for producing expanded polypropylene resin particles
WO2016158686A1 (en) * 2015-03-27 2016-10-06 株式会社カネカ Method for manufacturing polyethylene resin foam molded article
JPWO2016158686A1 (en) * 2015-03-27 2018-01-25 株式会社カネカ Method for producing polyethylene resin foam molding
US10100166B2 (en) 2015-03-27 2018-10-16 Kaneka Corporation Method for manufacturing polyethylene resin foam molded article
WO2021106354A1 (en) * 2019-11-29 2021-06-03 株式会社カネカ Device and method for producing expanded particles
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WO2022196372A1 (en) 2021-03-15 2022-09-22 株式会社ジェイエスピー Polyethylene resin foamed particle, and method for producing same
WO2023067954A1 (en) 2021-10-21 2023-04-27 株式会社ジェイエスピー Polyethylene resin foam particles, and method for producing same
WO2023067953A1 (en) 2021-10-21 2023-04-27 株式会社ジェイエスピー Polyethylene resin foam particles, and method for producing same

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