CN110862569B - Preparation method of polypropylene foaming particles with low melt strength - Google Patents
Preparation method of polypropylene foaming particles with low melt strength Download PDFInfo
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- 239000004743 Polypropylene Substances 0.000 title claims abstract description 41
- 238000005187 foaming Methods 0.000 title claims abstract description 37
- 239000002245 particle Substances 0.000 title claims abstract description 33
- -1 polypropylene Polymers 0.000 title claims abstract description 31
- 229920001155 polypropylene Polymers 0.000 title claims abstract description 30
- 238000002360 preparation method Methods 0.000 title claims abstract description 9
- 239000000463 material Substances 0.000 claims abstract description 39
- 239000007789 gas Substances 0.000 claims description 28
- 239000000203 mixture Substances 0.000 claims description 21
- 239000000498 cooling water Substances 0.000 claims description 14
- 238000002156 mixing Methods 0.000 claims description 13
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 8
- 238000001816 cooling Methods 0.000 claims description 8
- 239000004088 foaming agent Substances 0.000 claims description 8
- 239000000314 lubricant Substances 0.000 claims description 8
- 239000000155 melt Substances 0.000 claims description 8
- 238000002844 melting Methods 0.000 claims description 8
- 230000008018 melting Effects 0.000 claims description 8
- 238000000034 method Methods 0.000 claims description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 239000012752 auxiliary agent Substances 0.000 claims description 6
- 239000002216 antistatic agent Substances 0.000 claims description 5
- 239000002667 nucleating agent Substances 0.000 claims description 5
- VBICKXHEKHSIBG-UHFFFAOYSA-N 1-monostearoylglycerol Chemical compound CCCCCCCCCCCCCCCCCC(=O)OCC(O)CO VBICKXHEKHSIBG-UHFFFAOYSA-N 0.000 claims description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical group O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 4
- 239000001569 carbon dioxide Substances 0.000 claims description 4
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 4
- 238000001125 extrusion Methods 0.000 claims description 4
- 238000000048 melt cooling Methods 0.000 claims description 4
- QIQXTHQIDYTFRH-UHFFFAOYSA-N octadecanoic acid Chemical group CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 3
- 239000001273 butane Substances 0.000 claims description 2
- FPAFDBFIGPHWGO-UHFFFAOYSA-N dioxosilane;oxomagnesium;hydrate Chemical compound O.[Mg]=O.[Mg]=O.[Mg]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O FPAFDBFIGPHWGO-UHFFFAOYSA-N 0.000 claims description 2
- 239000000395 magnesium oxide Substances 0.000 claims description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 2
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims description 2
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 claims description 2
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- 239000000377 silicon dioxide Substances 0.000 claims description 2
- 235000012239 silicon dioxide Nutrition 0.000 claims description 2
- RUBCRQCHASKLFN-UHFFFAOYSA-N n-ethoxydodecanamide Chemical group CCCCCCCCCCCC(=O)NOCC RUBCRQCHASKLFN-UHFFFAOYSA-N 0.000 claims 1
- 229920000642 polymer Polymers 0.000 abstract description 4
- 238000001035 drying Methods 0.000 description 23
- 238000000465 moulding Methods 0.000 description 13
- 230000000052 comparative effect Effects 0.000 description 6
- 238000002347 injection Methods 0.000 description 6
- 239000007924 injection Substances 0.000 description 6
- 239000011148 porous material Substances 0.000 description 4
- 210000004027 cell Anatomy 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 210000002421 cell wall Anatomy 0.000 description 2
- 239000006260 foam Substances 0.000 description 2
- HQKMJHAJHXVSDF-UHFFFAOYSA-L magnesium stearate Chemical compound [Mg+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O HQKMJHAJHXVSDF-UHFFFAOYSA-L 0.000 description 2
- DZGWFCGJZKJUFP-UHFFFAOYSA-N Tyramine Natural products NCCC1=CC=C(O)C=C1 DZGWFCGJZKJUFP-UHFFFAOYSA-N 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 235000019359 magnesium stearate Nutrition 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 229920006126 semicrystalline polymer Polymers 0.000 description 1
- 229960003732 tyramine Drugs 0.000 description 1
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- 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
- C08J9/0014—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
- C08J9/0095—Mixtures of at least two compounding ingredients belonging to different one-dot groups
-
- 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
- C08J9/04—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
- C08J9/14—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 organic
- C08J9/141—Hydrocarbons
-
- 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
- C08J2203/00—Foams characterized by the expanding agent
- C08J2203/08—Supercritical fluid
-
- 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
- C08J2203/14—Saturated hydrocarbons, e.g. butane; Unspecified hydrocarbons
-
- 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
- C08J2323/10—Homopolymers or copolymers of propene
- C08J2323/12—Polypropene
Abstract
The invention belongs to the field of preparation of polymer foaming materials, and particularly relates to a preparation method of polypropylene foaming particles with low melt strength.
Description
Technical Field
The invention belongs to the field of preparation of polymer foaming materials, and particularly relates to a preparation method of polypropylene foaming particles with low melt strength.
Background
Polymer foaming generally needs to be performed in a state that the polymer is softened, while polypropylene is generally a linear semi-crystalline polymer, the molecular chain is less branched, the molecular weight distribution is relatively narrow, and the softening point and the melting point are very close. Therefore, before the temperature reaches the melting point, the polypropylene does not flow basically, namely, the ideal softening state, namely, the foaming state cannot be achieved, and when the temperature is further increased, the melt strength of the polypropylene is rapidly reduced while the polypropylene is softened, so that the melt is difficult to enclose gas, the polypropylene foaming process is difficult to control, and the problems of cell wall breakage, gas escape, cell collapse, bubble combination and the like in the foaming process are easily caused. Many polypropylenes are therefore modified to increase their melt strength before being used for foaming, which undoubtedly increases the production process and the costs.
Disclosure of Invention
In order to solve the technical problems, the invention provides a preparation method of polypropylene foaming particles with low melt strength, which comprises the following steps: adding polypropylene and an auxiliary agent into a high-speed mixer, uniformly mixing, adding the obtained mixture into an extruder, carrying out melt blending, injecting supercritical gas into the mixture in the extruder as a foaming agent, extruding and cooling the mixture section by section, then foaming in a heating environment to obtain a polypropylene foaming material, cooling,
the auxiliary agent comprises a lubricant, and the mass ratio of the lubricant to the polypropylene is 5-10: 100, the lubricant is stearate or stearate,
wherein the polypropylene is homopolymerized polypropylene,
the auxiliary agent can also comprise nucleating agent, antistatic agent and the like, the nucleating agent is silicon dioxide, talcum powder, magnesium oxide and the like, the antistatic agent is ethoxy lauryl tyramine, glycerol-stearate and the like,
the mass ratio of the nucleating agent to the antistatic agent to the polypropylene is 0.1-5: 0.1-1: 100,
the extruder is preferably a double-screw extruder, after the polypropylene is fully melted in the extruder, supercritical gas is injected into the mixture, the supercritical gas is supercritical carbon dioxide, supercritical nitrogen, supercritical butane and the like, the mass fraction of the supercritical gas injected into the mixture is controlled to be 4-10% (the weight ratio of the injected supercritical gas to the mixture after the supercritical gas is injected),
extruding and cooling section by section, the mixture passes through a screw section and a melt cooling section of an extruder in sequence and is extruded into cooling water through a mouth mold,
controlling the melting and blending temperature of the screw section to the mixture to be 200-230 ℃, setting the temperature of the melt cooler to be 160-130 ℃, setting the temperature of the neck mold to be 120-110 ℃, setting the water temperature of cooling water to be 10-15 ℃,
the extruded material enters a drying tunnel to be foamed after being discharged with water, and is cut into granules after being foamed,
the drying tunnel temperature during foaming is 135-145 ℃.
In conclusion, the scheme directly uses the polypropylene with lower melt strength to extrude and prepare the foaming particles, the supercritical gas is injected into the extruder as the foaming agent in the melting and extruding process, when the foaming agent gas loses the supercritical state, the foaming agent gas expands and expands, for the polypropylene with low melt strength in a softening state, the conventional extrusion foaming often forms a large amount of open pore structures, and the mechanical strength of the obtained foaming material is very low,
in the scheme, the material passes through the melt cooler firstly in the process of being extruded by the extruder and then passes through the neck mold with relatively low temperature setting, so that the temperature of the material strip extruded from the neck mold is lower than the melting temperature of the material and has higher strength; meanwhile, at the moment that the material strip leaves the neck mold, the expansion of the foaming agent gas in the material strip after losing the supercritical state is limited by the strength of the material strip and cannot be fully expanded, so that the phenomenon that a large number of open pores are formed by the rupture of the cell wall is objectively avoided, and the expansion of the foaming agent gas in the material strip is further limited by the water cooling measure after the material strip leaves the neck mold; under the condition that the foaming gas is wrapped, the material strips enter a drying tunnel for high-temperature treatment, the foaming agent gas in the material strips can be further expanded and foamed at a relatively low temperature (relative to the softening temperature of the material), and a large amount of holes can not be formed and broken due to the fact that the wall of the foam hole is broken.
Drawings
FIG. 1 is a morphology chart of the foamed particles in stick form prepared in example 1,
FIG. 2 is a morphology chart of the foamed stripe particles prepared in example 2,
FIG. 3 is a morphology chart of a PP foamed sheet formed by molding and processing the foamed particles in strip form prepared in example 1,
fig. 4 is a morphology diagram of a PP foamed sheet formed by molding the foamed particles in a strip shape prepared based on comparative example 1.
Detailed Description
Example 1
Calculated according to the parts by weight, the following components are added
Uniformly mixing in a high-speed mixer (the mixing temperature is controlled to be below 50 ℃), adding the obtained mixture into a double-screw extruder to perform melt blending extrusion operation, wherein the screw section of the extruder is totally divided into 10 sections, and the temperature setting is as follows in sequence: the first section is 200 ℃, the second section is 200 ℃, the third section is 210 ℃, the fourth section is 210 ℃, the fifth section is 230 ℃, the sixth section is 230 ℃, the seventh section is 220 ℃, the eighth section is 220 ℃, the ninth section is 200 ℃ and the tenth section is 200 ℃, wherein, a gas injection port is arranged at the seventh section, supercritical carbon dioxide with the mass fraction of 4.5% (the weight ratio of the injected supercritical gas to the weight of the mixture after the supercritical gas is injected) is injected into the mixture of the screw of the extruder through the gas injection port, the pressure of the gas injection port is kept at 8MPa (the mixture reaches the state of full melting and mixing in the screw section of the extruder before entering the seventh section, the same is true);
the material passes through the screw rod section and then the melt cooling section, and is extruded into cooling water through the mouth mold,
wherein the temperature of the melt cooler is controlled to 145 ℃ (the material reaches the temperature when leaving the melt cooler, the same below), the temperature of the neck ring mold is controlled to 115 ℃ (the material reaches the temperature when leaving the neck ring mold, the same below), the diameter of the discharge nozzle (round) on the neck ring mold is 0.98mm,
the water temperature of the cooling water is kept between 12 and 13 ℃, and the length of a water containing cavity of a cooling water tank along the advancing direction of the extruded material is 3.5 m;
the material strips are immediately conveyed into a drying tunnel with the temperature of 140 ℃ for foaming after leaving the cooling water, the length of the drying tunnel is 20m, the length direction of the drying tunnel is consistent with the advancing direction of the extruded material, the transmission rate of the material strips in the cooling water and the drying tunnel is 0.7m/s, the material strips are firstly cut according to the length of 5 m/section after leaving the drying tunnel, and are naturally cooled to the normal temperature (25 ℃, the same below) and then are crushed into strip-shaped particles (as shown in figure 1).
The length of the obtained strip-shaped particles is 5mm, the radial diameter of the obtained strip-shaped particles is 3.1-4 mm, and the radial diameter (1.03-1.09 mm) of the obtained strip-shaped particles is obviously increased compared with the radial diameter of the strip before entering the drying channel, so that the strip-shaped particles have obvious foaming behavior after entering the drying channel.
The foamed particles obtained in example 1 were found to have an average foaming density of 0.06g/cm3The foamed particles are processed and molded by steam molding equipment to obtain a PP foamed sheet with the thickness of 2cm (a mold is a concave-convex plate with the depth of 2cm, the molding pressure is 0.5MPa, the molding time is 5 minutes, and the mold peak is 20mm), and after the PP foamed sheet is placed at normal temperature for 24 hours after demolding, the appearance is as shown in figure 3, and the PP foamed sheet refers to ISO 1798: 2008, the tensile strength is 0.8 MPa.
Example 2
Calculated according to the parts by weight, the following components are added
Uniformly mixing in a high-speed mixer (the mixing temperature is controlled to be below 50 ℃), adding the obtained mixture into a double-screw extruder to perform melt blending extrusion operation, wherein the screw section of the extruder is totally divided into 10 sections, and the temperature setting is as follows in sequence: the gas injection port is arranged at the seventh section, supercritical carbon dioxide with the mass fraction of 4% (the ratio of the weight of the injected supercritical gas to the weight of the mixture after the supercritical gas is injected) is injected into the mixture of the machine screw through the gas injection port, and the pressure of the gas injection port is kept at 8 MPa;
the material passes through the screw rod section and then the melt cooling section, and is extruded into cooling water through the mouth mold,
wherein the temperature of the melt cooler is controlled to be 140 ℃, the temperature of the neck ring mold is controlled to be 115 ℃, the diameter of a discharge nozzle (round) on the neck ring mold is 0.98mm,
the water temperature of the cooling water is kept between 12 and 13 ℃, and the length of a water containing cavity of a cooling water tank along the advancing direction of the extruded material is 3.5 m;
the material strips are immediately conveyed into a drying tunnel with the temperature of 137 ℃ for foaming after leaving the cooling water, the length of the drying tunnel is 20m, the length direction of the drying tunnel is consistent with the advancing direction of the extruded material, the transmission rate of the material strips in the cooling water and the drying tunnel is 0.7m/s, the material strips are firstly cut according to the length of 5 m/section after leaving the drying tunnel, and are naturally cooled to the normal temperature (25 ℃, the same below) and then are crushed into strip-shaped particles (as shown in figure 2).
The radial diameter of the strip-shaped particles with the length of 5mm is 1.9-2.4 mm, and is obviously increased compared with the radial diameter (1.00-1.04 mm) of the material strips before entering the drying channel, which shows that the material strips have obvious foaming behavior after entering the drying channel.
The foamed particles obtained in example 2 were found to have an average foaming density of 0.20g/cm3The foamed particles are processed and molded by steam molding equipment to obtain a PP foamed sheet with the thickness of 2cm (a mold is a concave-convex plate with the depth of 2cm, the molding pressure is 0.5MPa, the molding time is 5 minutes, and the mold peak is 20mm), and after demolding, the PP foamed sheet is placed at normal temperature for 24 hours, and the PP foamed sheet is prepared according to ISO 1798: 2008, the tensile strength is 2.65 MPa.
Comparative example 1
The amount of the lubricant magnesium stearate is reduced to 3 parts by mass, and the rest components and operation are the same as those in the example 1:
the material is smoothly extruded out of the neck mold without being blocked, the radial diameter of the material strip before entering the drying channel is 1.02-1.05 mm, after the material strip is foamed, cooled and cut into particles through the drying channel, the length of the strip-shaped particles is 5mm, the radial diameter of the strip-shaped particles is 1.13-1.22 mm, and the subsequent foaming phenomenon basically does not exist.
Comparative example 2
On the basis of comparative example 1, the average foaming density of the obtained foaming material is up to 0.06g/cm of example 1 only by raising the temperature of the drying tunnel3The temperature of the drying tunnel is 168 ℃, a phenomenon of knife sticking occurs when the material strip leaving the drying tunnel is cut into a length of 5 m/section, and strip-shaped particles are obtained after cooling and grain cuttingThe length of the particles is 5mm, the radial diameter is 2.6-3.7 mm,
and (3) processing and molding the obtained foaming particles by using steam molding equipment to obtain a PP foaming sheet with the thickness of 2cm (a mold is a concave-convex plate with the depth of 2cm, the molding pressure is 0.5MPa, the molding time is 5 minutes, and the mold peak is 20mm), and after demolding, placing at normal temperature for 24 hours, wherein the appearance is as shown in the attached figure 4, and referring to ISO 1798: 2008, the tensile strength was 0.34 MPa.
The difference in mechanical properties between example 1 and comparative example 2 at the same foam density is evident because: the drying tunnel foaming temperature is increased to cause the interior of the material strip to have a large number of open pore structures after foaming, while low-temperature foaming is realized in the embodiment 1 on the basis of the content of the lubricant, and most of formed cells have uniform closed pore structures. This is also seen in comparative example 2 where the radial dimension of the strands after foaming is less than in example 1; meanwhile, the stable morphology of the PP foamed sheet obtained by forming the foamed particles also illustrates the point: comparing fig. 3 and fig. 4, on the basis of the same molding operation, the PP foamed sheet shown in fig. 4 has a large area of overall depressions on the panel surface, which is caused by too many open cell structures in the foamed resin, and this defect is not substantially present in the reverse view of fig. 3.
Claims (5)
1. A preparation method of polypropylene foaming particles with low melt strength is characterized by comprising the following steps: the preparation method comprises adding polypropylene and auxiliary agent into a high-speed mixer, mixing uniformly, adding the obtained mixture into an extruder, melting and blending, injecting supercritical gas into the mixture in the extruder as foaming agent, extruding and cooling the mixture section by section, then foaming in a heating environment to obtain polypropylene foaming material, cooling,
the auxiliary agent comprises a lubricant, and the mass ratio of the lubricant to the polypropylene is (5-10): 100, the lubricant is stearate or stearate;
the extrusion and the section-by-section cooling are that the mixture sequentially passes through a screw section and a melt cooling section of the extruder and is extruded into cooling water through a mouth mold,
controlling the melting and blending temperature of the screw section to the mixture to be 200-230 ℃, setting the temperature of the melt cooler to be 160-130 ℃, setting the temperature of the neck mold to be 120-110 ℃, and setting the water temperature of cooling water to be 10-15 ℃;
the temperature of the heating environment is 135-145 ℃.
2. The method for preparing low melt strength polypropylene foamed particles according to claim 1, wherein: the polypropylene is homopolymerized polypropylene.
3. The method for preparing low melt strength polypropylene foamed particles according to claim 1, wherein: the auxiliary agent also comprises a nucleating agent and an antistatic agent, wherein the nucleating agent is silicon dioxide, talcum powder or magnesium oxide, and the antistatic agent is ethoxy lauroyl amide or glycerol-stearate.
4. The method for preparing low melt strength polypropylene foamed particles according to claim 1, wherein: the supercritical gas is supercritical carbon dioxide, supercritical nitrogen or supercritical butane.
5. The method for preparing low melt strength polypropylene foamed particles according to claim 1, wherein: the mass fraction of the supercritical gas injected into the mixture is 4-10%.
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| CN101538387B (en) * | 2008-03-17 | 2012-05-02 | 合肥会通中科材料有限公司 | Polypropylene foaming material and production method thereof |
| CN107189213A (en) * | 2017-06-29 | 2017-09-22 | 义乌市中科院兰州化物所功能材料中心 | A kind of natural aromatic type expanded material and preparation method |
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| CN103042647B (en) * | 2012-11-08 | 2015-05-20 | 江苏微赛新材料科技有限公司 | Method for producing polypropylene micro-porous foamed thick board |
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| CN101538387B (en) * | 2008-03-17 | 2012-05-02 | 合肥会通中科材料有限公司 | Polypropylene foaming material and production method thereof |
| CN107189213A (en) * | 2017-06-29 | 2017-09-22 | 义乌市中科院兰州化物所功能材料中心 | A kind of natural aromatic type expanded material and preparation method |
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