WO2020158886A1 - Multilayer foam sheet - Google Patents

Multilayer foam sheet Download PDF

Info

Publication number
WO2020158886A1
WO2020158886A1 PCT/JP2020/003509 JP2020003509W WO2020158886A1 WO 2020158886 A1 WO2020158886 A1 WO 2020158886A1 JP 2020003509 W JP2020003509 W JP 2020003509W WO 2020158886 A1 WO2020158886 A1 WO 2020158886A1
Authority
WO
WIPO (PCT)
Prior art keywords
layer
resin
resin layer
foam sheet
multilayer foam
Prior art date
Application number
PCT/JP2020/003509
Other languages
French (fr)
Japanese (ja)
Inventor
晶啓 浜田
Original Assignee
積水化学工業株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 積水化学工業株式会社 filed Critical 積水化学工業株式会社
Priority to JP2020516941A priority Critical patent/JPWO2020158886A1/en
Priority to KR1020217023847A priority patent/KR20210121049A/en
Priority to CN202080011075.3A priority patent/CN113348072A/en
Publication of WO2020158886A1 publication Critical patent/WO2020158886A1/en

Links

Images

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/18—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by features of a layer of foamed material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/065—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of foam
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/022—Mechanical properties
    • 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
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/20—Adhesives in the form of films or foils characterised by their carriers
    • C09J7/22—Plastics; Metallised plastics
    • C09J7/26—Porous or cellular plastics
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/20—Adhesives in the form of films or foils characterised by their carriers
    • C09J7/29—Laminated material

Definitions

  • the present invention relates to a multilayer foam sheet comprising at least one layer of foam.
  • foam sheets made of foam are widely used as seal materials or shock absorbers.
  • the foamed sheet may be used as an adhesive tape by applying an adhesive on at least one surface inside an electronic device.
  • a foamed sheet used in these applications a crosslinked polyolefin resin foamed sheet obtained by foaming and crosslinking a foamable polyolefin resin sheet containing a thermal decomposition type foaming agent is known (for example, Patent Document 1). 1).
  • foam sheets used inside electronic devices have been required to be thinner as electronic devices have become smaller and thinner.
  • the mechanical strength such as tensile strength tends to be low, and therefore, for example, when the foamed sheet is used as an adhesive tape, the foamed sheet is easily damaged during reworking.
  • the foamed sheet if the foaming ratio is lowered to increase the mechanical strength, the compression strength becomes high, and the characteristics originally possessed by the foamed sheet such as impact absorption may be impaired.
  • a multilayer foam sheet having both properties is being studied.
  • the radius of curvature is different between the layer on the winding core side (inner layer) and the layer on the opposite side (outer layer). Therefore, the inner layer may be bent toward the base material layer side, and a defect due to a crease may occur.
  • the present invention has been made in view of the above problems, and provides a multilayer foam sheet that can suppress appearance defects such as folds and wrinkles while improving flexibility and mechanical strength. It is an issue.
  • the inventors of the present invention set the bending stress of at least one resin layer among the resin layers provided on both surfaces of the base material layer (foam) within a specific range in the multilayer foam sheet.
  • the inventors have found that the above-mentioned problems can be solved by the above and completed the following invention.
  • the present invention provides the following [1] to [15].
  • a first resin layer made of a resin film or a foam, a second resin layer made of a foam, and a third resin layer made of a resin film or a foam are provided in this order, and the radius of curvature (R) is A multilayer foam sheet in which the bending stress of the third resin layer defined by the following formula (1) when it is 152.4 mm is 1.6 MPa or less.
  • the total thickness of the first resin layer and the third resin layer is 50% or less of the total thickness of the multilayer foam sheet, according to any one of the above [1] to [4].
  • the bending stress of the third resin layer defined by the above formula (1) is 1.6 MPa or less when the radius of curvature (R) is 101.6 mm, and the above [1] to [5] The multilayer foam sheet according to any one of 1.
  • the bending stress of the third resin layer defined in the above (1) is 1.6 MPa or less when the radius of curvature (R) is 76.2 mm.
  • the bending stress of the first resin layer defined by the above formula (2) is 1.6 MPa or less when the radius of curvature (R2) is 76.2 mm, [8] or [9] above.
  • the multilayer foam sheet according to. [11] The multilayer foam sheet according to any one of the above [1] to [10], wherein the tensile strength of the first resin layer is 1.5 N or more.
  • the resin constituting the second resin layer is one or more selected from the group consisting of a polyolefin resin, a polyurethane resin, an acrylic resin, and a thermoplastic elastomer. ]
  • the present invention it is possible to provide a multilayer foam sheet that can suppress appearance defects such as folds and wrinkles while improving flexibility and mechanical strength.
  • the multilayer foam sheet of the present invention includes a first resin layer made of a resin film or foam, a second resin layer (base material layer) made of foam, and a third resin layer made of resin film or foam.
  • first to third resin layers may be referred to as first to third layers for the sake of simplicity.
  • the multilayer foam sheet 10 is composed of three layers, and the first layer 11 and the third layer 13 may be directly laminated on both surfaces of the second layer 12. ..
  • the multilayer foam sheet 10 includes first to third layers 11, 12 and 13, and a first adhesive layer, an adhesive layer, and other adhesive layers 14 and 15 interposed therebetween.
  • Each of the first layer 11 and the third layer 13 may be laminated on both surfaces of the second layer 12.
  • the first and third layers 11 and 13 may be outermost layers in the multilayer foam sheet 10.
  • the bending stress of the third layer defined by the following formula (1) is 1.6 MPa or less when the radius of curvature (R) is 152.4 mm.
  • Bending stress of third layer D ⁇ S/R (1)
  • D Tensile elastic modulus (MPa) of the third layer in the MD direction
  • S Distance from the neutral point of the first layer to the surface of the third layer on the side opposite to the second layer (mm)
  • R radius of curvature Note that the neutral point is, as shown in FIGS. 1 and 2, an intermediate point C in the thickness direction of the first layer 11, and a distance S is from the intermediate point C to the surface of the third layer 13. It is the distance to 13A.
  • the multilayer foam sheet is generally wound around a core such as a paper core and stored, but at that time, a radius of curvature differs between the layer on the core side and the layer on the opposite side. Wrinkles will occur in the layer.
  • a radius of curvature differs between the layer on the core side and the layer on the opposite side. Wrinkles will occur in the layer.
  • the bending stress of one surface of the multilayer foam sheet is adjusted to a specific range, at least one surface of the multilayer foam sheet becomes sufficiently flexible and is wound around the winding core. Even if it is, it becomes possible to suppress the generation of creases.
  • "MD" means Machine Direction and means the direction which corresponds with the extrusion direction etc. of a film layer.
  • the above formula (1) means that the bending stress when the third layer is bent with a predetermined radius of curvature is 1.6 MPa or less. Therefore, the multilayer foam sheet of the present invention has a bending stress of only 1.6 MPa or less even when it is wound around a core such as a paper core having a radius of 152.4 mm (6 inches), thereby causing a crease. It is possible to suppress the occurrence of.
  • the paper core having a radius of 6 inches is generally used as a core for winding a foam sheet or the like.
  • the multilayer foam sheet of the present invention has a multilayer structure having three resin layers, it is easy to improve both flexibility and mechanical strength.
  • the bending stress of the third layer when the radius of curvature is 152.4 mm (6 inches) is more preferably 1.55 MPa or less, and further preferably 1.5 MPa or less from the viewpoint of sufficiently suppressing creases. It is 0 MPa or less, more preferably 0.6 MPa or less.
  • the bending stress when the radius of curvature is 152.4 mm (6 inches) is preferably 0.1 MPa or more, and more preferably 0.2 MPa or more, in order to give the third layer a certain tensile strength or more. ..
  • the bending stress of the third layer calculated by the formula (1) is preferably 1.6 MPa or less even when the radius of curvature (R) is 101.6 mm (4 inches).
  • a core such as a paper core having a radius of about 4 inches and a smaller diameter may be used.
  • the pressure is 1.6 MPa or less, a crease does not occur even when wound around a winding core having a small diameter.
  • the bending stress of the third layer calculated by the formula (1) is more preferably 1.6 MPa or less even when the radius of curvature is 76.2 mm (3 inches).
  • a core such as a paper core is generally used that has a minimum diameter of about 3 inches, but as described above, even when the radius of curvature is 76.2 mm.
  • the bending stress is 1.6 MPa or less, a crease does not occur even when wound on a winding core having an extremely small diameter.
  • the multilayer foam sheet in which the resin film or the foam is provided on both sides of the base material layer (second layer) is any one of the resin films or the foam provided on both sides. Is the first layer, and the other is the third layer. Therefore, in the present invention, it is preferable that one of the resin film or the foam provided on both surfaces has a bending stress calculated by the formula (1) of 1.6 MPa or less. This is because if the bending stress of one layer (that is, the third layer) is 1.6 MPa or less, creases will not occur if the third layer is wound so as to be on the winding core side (inside). ..
  • both the resin film and the foam provided on both surfaces have a bending stress of 1.6 MPa or less. That is, when the radius of curvature (R2) is 152.4 mm, the bending stress of the first layer defined by the following formula (2) is preferably 1.6 MPa or less.
  • the bending stress of both the first and third layers is 1.6 MPa or less, so that both the first and third layers are wound so as to be on the winding core side (inner side). Since wrinkles do not occur even when taken, the multilayer foam sheet can be wound without limitation.
  • the bending stress of the first layer when the radius of curvature is 152.4 mm (6 inches) is more preferably 1.55 MPa or less, and further preferably 1.5 MPa or less from the viewpoint of sufficiently suppressing creases. It is 0 MPa or less, more preferably 0.6 MPa or less. Further, when the radius of curvature is 152.4 mm (6 inches), the bending stress of the first layer is preferably 0.1 MPa or more in order to give the first layer a certain tensile strength or more, 2 MPa or more is more preferable.
  • the bending stress of the first layer calculated by the equation (2) has a radius of curvature (R2) of 101 even from the viewpoint that the winding of the multilayer foam sheet can be performed without limitation on a winding core having a small diameter. Even when it is 0.6 mm (4 inches), it is more preferably 1.6 MPa or less. Further, from the viewpoint that the multi-layer foam sheet can be wound around the winding core having an extremely small diameter without limitation, the bending stress of the first layer calculated by the formula (2) has a radius of curvature of 76. Even in the case of 0.2 mm (3 inches), the pressure is more preferably 1.6 MPa or less.
  • the tensile elastic modulus (D) of the third layer in the MD direction is preferably 40 to 500 MPa, more preferably 60 to 450 MPa, still more preferably 150 to 400 MPa.
  • the tensile elastic modulus (D2) in the MD direction of the first layer is preferably 40 to 500 MPa, more preferably 60 to 450 MPa, still more preferably 150 to 400 MPa.
  • the tensile elastic moduli of the first layer and the third layer in the MD direction may be obtained by measuring as described in the examples.
  • the tensile strength of the third layer in the MD direction is 1.5 N or more, and preferably 2.5 N or more.
  • the tensile strength of the third layer is 2.5 N or more, it is possible to improve the mechanical strength without causing creases and maintaining the flexibility of the multilayer foam sheet.
  • the tensile strength in the MD direction of the third layer is more preferably 4N or more.
  • the tensile strength is, for example, 200 N or less, and preferably 100 N or less, from the viewpoint of keeping the bending stress constant or less.
  • the tensile strength in the MD direction of the first layer is 1.5 N or more, but from the viewpoint of improving mechanical strength while maintaining flexibility, 2.5 N or more is preferable. It is also preferable that the tensile strengths in the MD direction of both the first and third layers are 2.5 N or more. When the tensile strengths of both the first and third layers are 2.5 N or more, it becomes easier to improve the mechanical strength of the multilayer foam sheet.
  • the tensile strength in the MD direction of the first layer is more preferably 4N or more, and further preferably, the tensile strength in the MD direction of both the first and third layers is 4N or more. Further, the tensile strength may be, for example, 200 N or less, and preferably 100 N or less, from the viewpoint of keeping the bending stress below a certain level. The tensile strength can be measured according to JIS K6767.
  • the 25% compressive strength of the multilayer foam sheet of the present invention is preferably 800 kPa or less.
  • the 25% compressive strength of the multilayer foam sheet is 800 kPa or less, the flexibility of the multilayer foam sheet is improved, and the impact absorbency and the like are also improved.
  • the adhesive strength of the adhesive tape is easily improved when it is used as a base material of the adhesive tape. From these viewpoints, the 25% compressive strength of the multilayer foam sheet is preferably 700 kPa or less, more preferably 300 kPa or less, and further preferably 100 kPa or less.
  • the 25% compressive strength of the multilayer foam sheet is preferably 20 kPa or more, more preferably 30 kPa or more, still more preferably 40 kPa or more.
  • the 25% compressive strength can be measured according to JIS K6767.
  • the total thickness of the multilayer foam sheet is not particularly limited, but is preferably 50 to 2000 ⁇ m, more preferably 80 to 1800 ⁇ m, and further preferably 150 to 1200 ⁇ m. By making the total thickness of the multilayer foam sheet within such a range, it becomes possible to make the multilayer foam sheet thin and it becomes easy to obtain a multilayer foam sheet having good flexibility and mechanical strength.
  • the total thickness of the first layer and the third layer is preferably 50% or less, more preferably 30% or less, and further preferably 25% or less of the total thickness of the multilayer foam sheet. preferable.
  • the total thickness is preferably 2% or more, more preferably 4% or more, still more preferably 7% or more of the total thickness of the multilayer foam sheet.
  • the total thickness of the multilayer foam sheet 10 is the total of the three layers in the case of the three-layer structure of the first layer 11, the second layer 12, and the third layer 13. Is T1.
  • FIG. 1 the total thickness of the multilayer foam sheet 10 is the total of the three layers in the case of the three-layer structure of the first layer 11, the second layer 12, and the third layer 13. Is T1.
  • the total thickness is equal to that between the first layer 11 and the second layer 12 or between the second layer 12 and the third layer 13 (adhesive layers 14 and 15).
  • the thickness T2 is the total thickness of the first to third layers 11 to 13 plus the thickness of the adhesive layers 14 and 15.
  • each of the first layer and the third layer is preferably 1 to 500 ⁇ m, more preferably 5 to 250 ⁇ m, and further preferably 10 to 90 ⁇ m. Within such a range, the multilayer foam sheet can be made thinner. Moreover, it becomes easy to adjust the tensile strength of the first layer and the third layer and the 25% compressive strength of the multilayer foam sheet within the above range.
  • the thicknesses of the first layer and the third layer may be the same or different.
  • the thickness of the second layer is not particularly limited, but is preferably 40 to 1900 ⁇ m, more preferably 70 to 1600 ⁇ m, and further preferably 100 to 1000 ⁇ m. By setting the thickness of the second layer within such a range, it becomes possible to make the multilayer foam sheet thin and it is easy to obtain a multilayer foam sheet having good flexibility.
  • the thickness of the second layer is typically larger than the thickness of each of the first and third layers. By making the thickness of the second layer larger than that of each of the first and third layers, it becomes easy to increase the flexibility of the multilayer foam sheet.
  • the second layer of the present invention is made of resin foam.
  • the type of resin forming the second layer is not particularly limited, but examples thereof include polyolefin-based resin, acrylic resin, polyurethane-based resin, and thermoplastic elastomer. These may be used alone or in combination of two or more. Of these, polyolefin resins and thermoplastic elastomers are preferable, and polyolefin resins are more preferable. By using the polyolefin resin and the thermoplastic elastomer, it becomes easy to secure the flexibility and mechanical strength of the second layer while improving the foamability and the like.
  • the resin used in the second layer may be used alone or in combination of two or more.
  • the polyolefin resin is a thermoplastic resin, and specific examples thereof include polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer, and the like, and among these, polyethylene resin is preferable.
  • the polyethylene resin include polyethylene resins polymerized with a polymerization catalyst such as a Ziegler-Natta compound, a metallocene catalyst and a chromium oxide compound, and preferably a polyethylene resin polymerized with a metallocene catalyst is used.
  • metallocene catalyst examples include compounds such as a bis(cyclopentadienyl) metal complex having a structure in which a transition metal is sandwiched by ⁇ -electron unsaturated compounds. More specifically, tetravalent transition metals such as titanium, zirconium, nickel, palladium, hafnium, and platinum have one or more cyclopentadienyl rings or their analogs as ligands. The compound can be mentioned. Such a metallocene catalyst has uniform properties of active sites and each active site has the same activity. Polymers synthesized using a metallocene catalyst have high homogeneity in molecular weight, molecular weight distribution, composition, composition distribution, etc.
  • the crosslinking is uniform. Proceed to. Since the uniformly crosslinked sheet is uniformly foamed, it becomes easy to stabilize the physical properties. Further, since the film can be stretched uniformly, the thickness of the foam can be made uniform.
  • Examples of the ligand include a cyclopentadienyl ring and an indenyl ring. These cyclic compounds may be substituted with a hydrocarbon group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group.
  • Examples of the hydrocarbon group include a methyl group, an ethyl group, various propyl groups, various butyl groups, various amyl groups, various hexyl groups, 2-ethylhexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups. , Various cetyl groups, phenyl groups and the like.
  • cyclic compound as an oligomer may be used as a ligand.
  • monovalent anion ligands such as chlorine and bromine or divalent anion chelate ligands, hydrocarbons, alkoxides, arylamides, aryloxides, amides, arylamides, phosphides, aryls. You may use phosphide etc.
  • the metallocene catalyst containing a tetravalent transition metal or a ligand examples include cyclopentadienyl titanium tris(dimethylamide), methylcyclopentadienyl titanium tris(dimethylamide), bis(cyclopentadienyl)titanium dichloride, and dimethyl. Examples thereof include silyltetramethylcyclopentadienyl-t-butylamide zirconium dichloride.
  • the metallocene catalyst when combined with a specific co-catalyst (co-catalyst), exhibits an action as a catalyst during the polymerization of various olefins.
  • cocatalysts include methylaluminoxane (MAO) and boron compounds.
  • the ratio of the cocatalyst used to the metallocene catalyst is preferably 100 to 1,000,000 mol times, more preferably 50 to 5,000 mol times.
  • linear low density polyethylene is preferable.
  • the linear low-density polyethylene is obtained directly by copolymerizing ethylene (for example, 75% by mass or more, preferably 90% by mass or more with respect to the total amount of monomers) and a small amount of ⁇ -olefin as necessary. Chain low density polyethylene is more preferable.
  • Specific examples of the ⁇ -olefin include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and the like. Of these, ⁇ -olefins having 4 to 10 carbon atoms are preferable.
  • Polyethylene resin for example the density of the above-mentioned linear low density polyethylene, from the viewpoint of flexibility, preferably 0.870 ⁇ 0.925g / cm 3, more preferably 0.890 ⁇ 0.925g / cm 3, 0 It is more preferably 0.910 to 0.925 g/cm 3 .
  • the polyethylene resin a plurality of polyethylene resins may be used, and a polyethylene resin having a density outside the above range may be added.
  • Examples of the ethylene-vinyl acetate copolymer used as the polyolefin resin include an ethylene-vinyl acetate copolymer containing 50% by mass or more of ethylene.
  • Examples of the polypropylene resin include homopolypropylene and a propylene- ⁇ -olefin copolymer containing 50% by mass or more of propylene. These may be used alone or in combination of two or more.
  • ⁇ -olefin constituting the propylene- ⁇ -olefin copolymer examples include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1- Examples thereof include octene, and of these, ⁇ -olefin having 6 to 12 carbon atoms is preferable.
  • thermoplastic elastomer examples include olefin-based thermoplastic elastomer, styrene-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polyester-based thermoplastic elastomer, and polyamide-based thermoplastic elastomer.
  • these components may be used alone or in combination of two or more.
  • olefin-based thermoplastic elastomers and styrene-based thermoplastic elastomers are preferable, and styrene-based thermoplastic elastomers are more preferable.
  • thermoplastic elastomer examples include blend type, dynamically cross-linking type, and polymerization type. More specifically, a thermoplastic crystalline polyolefin such as polypropylene or polyethylene is used for the hard segment and a soft segment is used for the soft segment. Thermoplastic elastomers using fully vulcanized or partially vulcanized rubber are mentioned. Examples of the thermoplastic crystalline polyolefin include homopolymers of ⁇ -olefins having 1 to 4 carbon atoms or copolymers of two or more types of ⁇ -olefins, with polyethylene or polypropylene being preferred. Examples of the soft segment component include butyl rubber, halobutyl rubber, EPDM, EPM, acrylonitrile/butadiene rubber, NBR and natural rubber, and among these, EPDM is preferable.
  • a block copolymer type may be mentioned as the olefinic thermoplastic elastomer.
  • the block copolymer type include those having a crystalline block and a soft segment block, and more specifically, a crystalline olefin block-ethylene/butylene copolymer-crystalline olefin block copolymer (CEBC) is exemplified.
  • CEBC crystalline olefin block-ethylene/butylene copolymer-crystalline olefin block copolymer
  • the crystalline olefin block is preferably a crystalline ethylene block
  • examples of commercially available products of such CEBC include "DYNARON 6200P" manufactured by JSR Corporation.
  • styrene-based thermoplastic elastomer examples include a block copolymer having a polymer or copolymer block of styrene and a polymer or copolymer block of a conjugated diene compound.
  • conjugated diene compound examples include isoprene and butadiene.
  • the styrene-based thermoplastic elastomer used in the present invention may or may not be hydrogenated. When hydrogenating, hydrogenation can be performed by a known method.
  • the styrene-based thermoplastic elastomer is usually a block copolymer, such as styrene-isoprene block copolymer, styrene-isoprene-styrene block copolymer, styrene-butadiene block copolymer, styrene-butadiene-styrene block copolymer.
  • SEBS styrene-ethylene/butylene-styrene block copolymer
  • SEPS styrene-ethylene/propylene-styrene block copolymer
  • SEB styrene-ethylene/butylene block copolymer
  • SEP block copolymers
  • SEBC styrene-ethylene/butylene-crystalline olefin block copolymers
  • styrene-based thermoplastic elastomers are manufactured by JSR Co., Ltd., product name “DYNARON 8600P” (styrene content 15% by mass), product name “DYNARON 4600P” (styrene content 20% by mass), product name Examples include “DYNARON 1321P” (styrene content 10% by mass).
  • the second layer used in the present invention is preferably obtained by foaming a foamable composition containing the above resin and a foaming agent.
  • a foaming agent a thermal decomposition type foaming agent is preferable.
  • an organic foaming agent or an inorganic foaming agent can be used.
  • the organic foaming agent include azodicarbonamide, metal salts of azodicarboxylic acid (barium azodicarboxylic acid), azo compounds such as azobisisobutyronitrile, nitroso compounds such as N,N'-dinitrosopentamethylenetetramine, and hydra.
  • Examples thereof include hydrazine derivatives such as zodicarbonamide, 4,4′-oxybis(benzenesulfonylhydrazide) and toluenesulfonylhydrazide, and semicarbazide compounds such as toluenesulfonylsemicarbazide.
  • Examples of the inorganic foaming agent include ammonium carbonate, sodium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, anhydrous monosodium citrate and the like.
  • an azo compound is preferable, and an azodicarbonamide is more preferable, from the viewpoints of obtaining fine bubbles, economical efficiency, and safety.
  • the thermal decomposition type foaming agents may be used alone or in combination of two or more.
  • the blending amount of the foaming agent in the foamable resin composition is preferably 1 to 20 parts by mass, more preferably 1.5 to 15 parts by mass, and even more preferably 2 to 10 parts by mass with respect to 100 parts by mass of the resin.
  • a decomposition temperature adjusting agent may be added to the foamable resin composition.
  • the decomposition temperature adjusting agent is added to lower the decomposition temperature of the thermal decomposition type foaming agent or to accelerate or control the decomposition rate, and specific compounds include zinc oxide, zinc stearate and urea. Etc.
  • the decomposition temperature adjusting agent is mixed, for example, in an amount of 0.01 to 5 parts by mass with respect to 100 parts by mass of the resin in order to adjust the surface condition of the second layer and the like.
  • An antioxidant may be added to the foamable resin composition.
  • the antioxidant include phenolic antioxidants such as 2,6-di-t-butyl-p-cresol, sulfur antioxidants, phosphorus antioxidants, amine antioxidants and the like.
  • the antioxidant is mixed, for example, in an amount of 0.01 to 5 parts by mass with respect to 100 parts by mass of the resin.
  • the resin is the main component, and the content of the resin is, for example, 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, based on the total amount of the second layer.
  • the foamable resin composition if necessary, contains additives generally used in foams such as heat stabilizers, colorants, flame retardants, antistatic agents, and fillers in addition to the above. Good.
  • the expansion ratio of the second layer is not particularly limited, but is preferably 1.1 to 20 cm 3 /g. By setting the expansion ratio to 1.1 cm 3 /g or more, the flexibility of the multilayer foam sheet is increased, and the expansion ratio is set to 20 cm 3 /g or less. The strength of the multilayer foam sheet is improved.
  • the expansion ratio of the second layer is more preferably 2.5 to 18 cm 3 /g, and further preferably 7.5 to 16 cm 3 /g.
  • the expansion ratio of the second layer is represented by the reciprocal of the apparent density of the second layer.
  • the degree of crosslinking of the second layer is not particularly limited, but is, for example, 5 to 65%, preferably 10 to 55%, more preferably 20 to 50%.
  • the degree of crosslinking of the second layer is set to the lower limit value or more, it is possible to prevent the flexibility from increasing more than necessary and to secure a certain mechanical strength.
  • the content is not more than the above upper limit, the flexibility and the impact absorption are improved.
  • the first layer and the third layer are resin films or foams, respectively, as described above, and preferably resin films.
  • the resin film is a non-foamed resin layer.
  • both the first layer and the third layer are resin films will be described in more detail.
  • the kind of the resin constituting the resin film is not particularly limited as long as it satisfies the relations of the above formulas (1) and (2).
  • the resin include polyolefin resin, acrylic resin, polyurethane resin, and thermoplastic elastomer.
  • vinyl chloride resin, styrene resin, polyester resin, polyamide resin, ionomer resin, etc. may be used.
  • the resin may be used alone or in combination of two or more.
  • the resin used for the first layer and the resin used for the third layer may be the same kind of resin or different resins, but from the viewpoint of productivity and both layers. From the viewpoint of easily making the physical properties of the same or similar, it is preferable that they are the same kind.
  • the resin constituting each of the first layer and the third layer is preferably a thermoplastic resin, and by using the thermoplastic resin, the first layer and the third layer are easily bonded to the second layer. It is possible to in addition, as the resin used for each of the first layer and the third layer, a polyolefin resin is preferable among the above. By using the polyolefin-based resin, it becomes easy to increase the mechanical strength of the multilayer foam sheet while reducing the bending stress. Further, when a polyolefin resin or a thermoplastic elastomer is used for the second layer, the adhesion of the first and third layers to the second layer can be made particularly good.
  • polystyrene resin examples include polyethylene resin and polypropylene resin. Further, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer and the like may be used.
  • polyethylene resin examples include polyethylene resins polymerized with a polymerization catalyst such as a Ziegler-Natta compound, a metallocene catalyst and a chromium oxide compound, and preferably a polyethylene resin polymerized with a metallocene catalyst is used.
  • Examples of the polyethylene resin include low-density polyethylene (density: less than 0.930 g/cm 3 ), medium-density polyethylene (density: 0.930 g/cm 3 or more and less than 0.942 g/cm 3 ), high-density polyethylene ( Density: 0.942 g/cm 3 or more).
  • examples of the low-density polyethylene include linear low-density polyethylene. Since the details of the linear low-density polyethylene are as described in the description of the second layer, the details are omitted. Further, since the details of the polypropylene resin are as described in the description of the second layer, the details thereof will be omitted.
  • the ethylene-vinyl acetate copolymer used in the first and third layers includes, for example, an ethylene-vinyl acetate copolymer containing 50% by mass or more of a constitutional unit derived from ethylene.
  • the ethylene-ethyl acrylate copolymer includes an ethylene-ethyl acrylate copolymer containing 50% by mass or more of constituent units derived from ethylene.
  • ethylene resin particularly linear low-density polyethylene is preferable.
  • ethylene-vinyl acetate copolymer is also preferable.
  • the resin is the main component, and the resin content is, for example, 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, based on the total amount of each layer.
  • the first layer and the third layer may contain additives such as an antioxidant, a heat stabilizer, a colorant, a flame retardant, an antistatic agent and a filler, in addition to the above resins.
  • the first and third layers may be crosslinked.
  • the first and third layers may be cross-linked at the same time as the second layer is cross-linked, as described in the production method 1 described later, and thus are preferably cross-linked by ionizing radiation.
  • Each of the first and third layers may be foam, as described above.
  • the resin that can be used in the first and third layers is mixed with a foaming agent or the like as described in the second layer. Then, the first and third layers may be foamed.
  • the expansion ratio is low and the bubble ratio indicating the ratio of bubbles contained in each layer is low from the viewpoint of ensuring a certain mechanical strength.
  • the bubble ratio of each of the first layer and the third layer is preferably 66% or less, more preferably 33% or less, and further preferably 0%.
  • the bubble ratio is 0%.
  • the bubble ratio can be obtained, for example, by observing the cross section of the first layer and the third layer and calculating the ratio of the area occupied by the bubbles to the area of each layer. Specifically, a cross section is cut out along the thickness direction, and the cross section is photographed with an optical microscope. After that, the air bubbles and the resin portion may be binarized to be divided, and the area of the air bubbles/total area may be calculated.
  • the first layer and the second layer, or the second layer and the third layer may be directly adhered, but another layer (that is, an adhesive layer) is used. May be bonded together.
  • the adhesive layer a known adhesive or pressure-sensitive adhesive may be used. Further, it may be a double-sided pressure-sensitive adhesive tape in which a pressure-sensitive adhesive layer is provided on both sides of the base material.
  • the adhesive layer may have a thickness that does not significantly affect physical properties such as mechanical strength and flexibility in the multilayer foam sheet. Therefore, the thickness of the adhesive layer for bonding the first layer and the second layer is preferably thinner than that of the first layer, and more preferably 1/2 or less of the thickness of the first layer. Similarly, the thickness of the adhesive layer that bonds the second layer and the third layer is preferably thinner than that of the third layer, and more preferably 1/2 or less of the thickness of the third layer.
  • the multilayer foam sheet of the present invention is not particularly limited, but for example, a method of obtaining a multilayer laminate sheet by laminating a plurality of layers made of a resin composition, and then foaming the multilayer laminate sheet ( Hereinafter, it can be manufactured by "manufacturing method 1").
  • resin composition also includes a case where it is composed of one type of resin alone.
  • the manufacturing method 1 includes the following steps I to II.
  • (I) Multilayer laminate comprising a layer made of a foamable resin composition, a first layer formed on one surface of the layer, and a third layer formed on the other surface of the layer Step of obtaining a sheet
  • the method for obtaining the multilayer laminate sheet in step (I) is not particularly limited, but coextrusion molding is preferable. Specifically, a resin for forming the first layer and the third layer, and other additives to be blended as necessary are supplied to the first and third extruders respectively and melt-kneaded. , To obtain a resin composition for forming the first and third layers. Further, a resin for forming the second layer, a foaming agent such as a thermal decomposition type foaming agent, and an additive to be blended as necessary are supplied to the second extruder and melt-kneaded, A foamable resin composition for forming the layer is obtained.
  • the resin compositions supplied from the first to third extruders are merged so that the composition supplied from the second extruder becomes an intermediate layer, and the mixture is extruded into a sheet by a T-die or the like.
  • a multilayer laminate sheet having a three-layer structure can be obtained.
  • either the feed block method or the multi-manifold method may be used, but the feed block method is preferable.
  • the step (I) it is preferable to further crosslink the multilayer laminate sheet obtained above.
  • a cross-linking method there is also a method of previously blending an organic peroxide and heating the multi-layer laminate sheet obtained in the step (I) to cross-link, but the multi-layer laminate sheet is irradiated with ionizing radiation. It is preferable to crosslink.
  • the ionizing radiation include electron beams and ⁇ rays, but electron beams are preferable.
  • the dose of ionizing radiation is preferably 1 to 10 Mrad, more preferably 1.5 to 5 Mrad.
  • the multilayer laminate sheet obtained in the step (I) is subjected to a foaming treatment to foam a layer made of the foamable resin composition.
  • the layer made of the foamable resin composition may be treated so that the foaming agent foams.
  • the foaming agent is a pyrolytic foaming agent
  • the multilayer laminate sheet is heated to foam.
  • the heating temperature may be equal to or higher than the temperature at which the pyrolytic foaming agent decomposes, and is, for example, about 150 to 320°C.
  • the method for heating the multilayer laminate sheet is not particularly limited, and examples thereof include a method of heating the multilayer laminate sheet with hot air, a method of heating with infrared rays, a method of heating with a salt bath, and a method of heating with an oil bath. However, these may be used in combination. Further, the multilayer laminate sheet may be appropriately stretched while foaming or after foaming. In the above description, an example in which the first and third layers are resin films (non-foamed bodies) has been described, but when the first and third layers are foamed, A foaming agent such as a pyrolyzable foaming agent may be added as an additive to the resin composition for forming the first and third layers, and foamed in step (II).
  • a foaming agent such as a pyrolyzable foaming agent may be added as an additive to the resin composition for forming the first and third layers, and foamed in step (II).
  • the method for producing the multilayer foam sheet of the present invention can also be produced by another method. Specifically, a foam forming the second layer is manufactured in advance, and a resin film or a foam (first and third layers) is superposed on both surfaces of the foam (second layer). , And a method of bonding (also referred to as “second manufacturing method”).
  • a resin for forming the second layer, a pyrolytic foaming agent, and an additive to be blended as necessary are melt-kneaded to obtain a second layer. It is advisable to obtain a foamable resin composition for forming a layer and form the foamable resin composition into a sheet shape (foamable resin composition sheet).
  • the method of melting and kneading the foamable resin composition to form a sheet is not particularly limited, but it is preferable to use an extruder.
  • the obtained foamable resin composition sheet is preferably further cross-linked before foaming described later.
  • a cross-linking method there is also a method of pre-blending an organic peroxide and heating the foamable resin composition sheet to cross-link it, but the cross-linking is performed by irradiating the foamable resin composition sheet with ionizing radiation. Is preferred.
  • the type of ionizing radiation and the irradiation amount are as described in the above-mentioned first manufacturing method.
  • the foamable resin composition sheet may be foamed.
  • the layer made of the foamable resin composition may be treated so that the foaming agent foams.
  • the foaming agent is a pyrolytic foaming agent
  • the multilayer laminate sheet is heated to foam.
  • the heating temperature and the heating method are as described in the first manufacturing method described above. Further, the foamable resin composition sheet may be appropriately stretched while foaming or after foaming.
  • a resin film for forming the first layer and the third layer, or a foam, which is separately prepared, is placed on the foam for forming the second layer, and the foam is adhered to the multilayer foam sheet.
  • it may be heated and pressed by a press machine or the like to perform thermocompression bonding.
  • an adhesive, an adhesive, or the like is applied to the adhesive surface between the second layer and the first layer and the adhesive surface between the second layer and the third layer, or a double-sided adhesive tape is attached. You may put on and stick together with an adhesive, an adhesive, a double-sided adhesive tape, etc.
  • the multilayer foam sheet of the present invention is not particularly limited, but is preferably used, for example, inside an electronic device. For example, it is placed between two members and used as a shock absorber, a sealant, or the like. it can. Further, the multilayer foam sheet can be formed into a frame shape and used in a portable electronic device. Examples of the mobile electronic device include a mobile phone, a camera, a game device, an electronic notebook, and a personal computer. Further, the multilayer foam sheet of the present invention may be used as an adhesive tape described later and used inside an electronic device.
  • the multilayer foam sheet of the present invention may be wound into a roll such as a paper core.
  • a core having a radius of about 3 to 6 inches (76.2 to 152.4 mm) may be used as the core.
  • the multilayer foam sheet When wound on the core, the multilayer foam sheet may be wound so that the layer having a bending stress of not more than a predetermined value is on the core side (inside) as described above. Therefore, it suffices if the third layer is wound so as to be on the winding core side.
  • the layer may be wound so that the layer is on the winding core side (inside).
  • the multilayer foam sheet of the present invention may be used for an adhesive tape having the multilayer foam sheet as a base material.
  • the adhesive tape comprises, for example, a multilayer foam sheet and an adhesive material provided on at least one surface of the multilayer foam sheet.
  • the adhesive tape can be adhered to another member via the adhesive material.
  • the adhesive tape may be a multi-layer foam sheet provided with an adhesive material on both sides, or may be provided with an adhesive material on one side.
  • the pressure-sensitive adhesive may be at least one having a pressure-sensitive adhesive layer, and may be provided on the surface of the multilayer foam sheet (that is, the surfaces 11A and 13A of the first or third layers 11 and 13; see FIGS. 1 and 2). It may be a laminated pressure-sensitive adhesive layer alone or a double-sided pressure-sensitive adhesive sheet attached to the surface of the multilayer foam sheet, but it is preferably a pressure-sensitive adhesive layer alone.
  • the double-sided pressure-sensitive adhesive sheet includes a base material and a pressure-sensitive adhesive layer provided on both surfaces of the base material. The double-sided pressure-sensitive adhesive sheet is used to bond one pressure-sensitive adhesive layer to the multilayer foam sheet and the other pressure-sensitive adhesive layer to another member.
  • the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, and for example, an acrylic pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, a rubber pressure-sensitive adhesive, or the like can be used. Further, a release sheet such as release paper may be further attached on the adhesive material.
  • the thickness of the adhesive material is preferably 5 to 200 ⁇ m, more preferably 7 to 150 ⁇ m, and further preferably 10 to 100 ⁇ m.
  • the pressure-sensitive adhesive tape of the present invention may be wound around a winding core to form a roll.
  • the radius of the winding core is as described above.
  • the multilayer foam sheet is bent in a radius of curvature generally according to the size of the winding core because the thickness of the adhesive material is thin as described above even when wound in a state of an adhesive tape.
  • Measurement method The methods for measuring and evaluating each physical property are as follows.
  • ⁇ Tensile Elastic Modulus of First Layer and Third Layer> The tensile elastic moduli of the first layer and the third layer were measured using a tensile tester (Yamato Scientific Co., Ltd., Tensilon RTF series). The measurement conditions were based on JIS K6767.
  • ⁇ Tensile Strength of First Layer and Third Layer The first layer and the third layer were cut into dumbbell-shaped No. 1 type specified in JIS K6251 4.1. Using this as a sample, the tensile strength was measured by a tensile tester (product name: Tensilon RTF235, manufactured by A&D Company) at a measurement temperature of 23° C. according to JISK6767. ⁇ 25% compressive strength> The 25% compressive strength of the multilayer foam sheet was measured according to JIS K6767.
  • ⁇ Apparent density and expansion ratio> The apparent density of the foam was measured according to JIS K7222, and the reciprocal thereof was taken as the expansion ratio.
  • Example 1 Linear low density polyethylene resin obtained by metallocene catalysis as the polyolefin resin for the second layer (Nippon Polyethylene Co., Ltd., trade name “Kernel KF283", density: 0.921g / cm 3) (metallocene LLDPE), Azodicarbonamide was prepared as a thermal decomposition type foaming agent. Further, zinc oxide (trade name “OW-212F” manufactured by Sakai Chemical Industry Co., Ltd.) is used as a decomposition temperature adjusting agent, and 2,6-di-t-butyl-p-cresol, which is a phenolic antioxidant as an antioxidant. Prepared.
  • a foamable resin composition 100 parts by mass of a polyethylene resin, 8.0 parts by mass of a thermal decomposition type foaming agent, 1 part by mass of a decomposition temperature adjusting agent, and 0.5 parts by mass of an antioxidant are respectively supplied to a second extruder and melt-kneaded at 130°C. Then, a foamable resin composition was produced.
  • a linear low-density polyethylene resin (Tama Poly Co., Ltd., trade name "SK615P") was prepared as the polyethylene resin for the first layer and the third layer.
  • the polyethylene resin was supplied to the first extruder and the third extruder, respectively, and melt-kneaded at 130°C.
  • an unfoamed multilayer laminate sheet comprising a layer (second layer) made of a foamable resin composition and resin films (first layer and third layer) laminated on both surfaces of the layer Got Next, the multilayer laminate sheet was irradiated with an electron beam having an accelerating voltage of 500 kV at 2.5 Mrad to crosslink, and then continuously fed into a foaming furnace kept at 250° C. by hot air and an infrared heater to be heated. By foaming, a multilayer foam sheet having a first layer (resin film), a second layer (foam body), and a third layer (resin film) in this order was obtained.
  • Examples 2-14, Comparative Examples 1-2 The types of resin used for the first to third layers, the thickness of the second layer, and the thicknesses of the first and third layers were changed as shown in Table 1. Moreover, the expansion ratio of the second layer was changed as shown in Table 1 by changing the blending amount of the foaming agent. Further, the bubble ratio of the third layer was changed as shown in Table 1 by blending a foaming agent. A multilayer foam sheet was produced in the same manner as in Example 1 except for the above. The details of each resin are as follows.
  • SEBS SEBS, manufactured by JSR Corporation, product name "DYNARON 8600P”
  • SF625P Linear low-density polyethylene, manufactured by TamaPoly Co., Ltd., trade name "SF625P”
  • SB-7 Ethylene-vinyl acetate copolymer, manufactured by TamaPoly Co., Ltd., trade name "SB-7" HD: High-density polyethylene, Tama Poly Co., Ltd., trade name "HD"
  • Table 1 shows the characteristics of the multilayer foam sheets obtained in the examples and comparative examples, and the evaluation results of creases.
  • Multilayer Foam Sheet 11 First Resin Layer 12 Second Resin Layer 13 Third Resin Layer 14, 15 Adhesive Layer C, C2 Neutral Point S, S2 Distance

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Laminated Bodies (AREA)
  • Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)

Abstract

This multilayer foam sheet (10) is provided with a first resin layer (11) comprising a resin film or a foam, a second resin layer (12) comprising a foam, and a third resin layer (13) comprising a resin film or a foam, the layers being arranged in the stated order, and the multilayer foam sheet (10) being such that when the curvature radius (R) is 152.4 mm, the bending stress in the third resin layer (13) as stipulated by formula (1) is 1.6 MPa or less. This makes it possible to provide a multilayer foam sheet with which it is possible to suppress defects in appearance, such as creases.　Formula (1): bending stress in third resin layer = D × S/R (where D is the tensile modulus of elasticity (MPa) in the MD direction of the third resin layer, S is the distance (mm) from the center point of the first resin layer to the surface of the third resin layer that faces the second resin layer, and R is the curvature radius)

Description

多層発泡体シートMultilayer foam sheet
　本発明は、少なくとも１層の発泡体を備える多層発泡体シートに関する。 The present invention relates to a multilayer foam sheet comprising at least one layer of foam.
　携帯電話、カメラ、ゲーム機器、電子手帳、及びパーソナルコンピューター等の電子機器では、発泡体からなる発泡シートがシール材又は衝撃吸収材として広く使用されている。また、発泡シートは、電子機器内部において、例えば少なくとも一方の面に粘着剤を塗布して、粘着テープにして使用されることもある。従来、これら用途において使用される発泡シートとしては、熱分解型発泡剤を含む発泡性ポリオレフィン系樹脂シートを発泡かつ架橋させて得られる架橋ポリオレフィン系樹脂発泡シートが知られている（例えば、特許文献１参照）。 In electronic devices such as mobile phones, cameras, game machines, electronic organizers, and personal computers, foam sheets made of foam are widely used as seal materials or shock absorbers. In addition, the foamed sheet may be used as an adhesive tape by applying an adhesive on at least one surface inside an electronic device. Conventionally, as a foamed sheet used in these applications, a crosslinked polyolefin resin foamed sheet obtained by foaming and crosslinking a foamable polyolefin resin sheet containing a thermal decomposition type foaming agent is known (for example, Patent Document 1). 1).
特開２０１４－２８９２５号公報JP, 2014-28925, A
　近年、電子機器内部で使用される発泡シートは、電子機器の小型化、薄型化が進むことで、薄くすることが要求されている。しかし、発泡シートは、薄くなると引張り強度等の機械強度が低くなりやすいため、例えば、発泡シートを粘着テープとして使用する場合には、リワークする際等に破損されやすくなる。一方で、発泡シートは、機械強度を高めるために発泡倍率を低くすると、圧縮強度が高くなり、衝撃吸収性等の発泡シートが本来有する特性を損なうことがある。 In recent years, foam sheets used inside electronic devices have been required to be thinner as electronic devices have become smaller and thinner. However, when the foamed sheet becomes thin, the mechanical strength such as tensile strength tends to be low, and therefore, for example, when the foamed sheet is used as an adhesive tape, the foamed sheet is easily damaged during reworking. On the other hand, in the foamed sheet, if the foaming ratio is lowered to increase the mechanical strength, the compression strength becomes high, and the characteristics originally possessed by the foamed sheet such as impact absorption may be impaired.
　そこで、柔軟性を備える発泡体（基材層）の両面に強度を備える層を積層することにより、両方の性質を兼ね備えた多層発泡体シートが検討されている。しかし、このような多層発泡体シートは、例えば製造時に紙芯などの巻芯に巻き付けた場合、巻芯側の層（内層）とその反対側の層（外層）との間で曲率半径に差が生じるため、内層が基材層側に折れ曲がり、折れジワによる不良が発生することがある。 Therefore, by laminating layers with strength on both sides of a flexible foam (base material layer), a multilayer foam sheet having both properties is being studied. However, when such a multilayer foam sheet is wound around a winding core such as a paper core at the time of manufacturing, the radius of curvature is different between the layer on the winding core side (inner layer) and the layer on the opposite side (outer layer). Therefore, the inner layer may be bent toward the base material layer side, and a defect due to a crease may occur.
　本発明は、以上の問題点を鑑みてなされたものであって、柔軟性と機械強度とを良好にしつつ、折れジワなどの外観不良を抑制することができる多層発泡体シートを提供することを課題とする。 The present invention has been made in view of the above problems, and provides a multilayer foam sheet that can suppress appearance defects such as folds and wrinkles while improving flexibility and mechanical strength. It is an issue.
　本発明者らは、鋭意検討した結果、多層発泡体シートにおいて、基材層（発泡体）の両面に設けられた樹脂層のうち少なくとも１つの樹脂層の曲げ応力を特定の範囲内とすることにより上記課題が解決できることを見出し、以下の本発明を完成させた。 As a result of diligent studies, the inventors of the present invention set the bending stress of at least one resin layer among the resin layers provided on both surfaces of the base material layer (foam) within a specific range in the multilayer foam sheet. The inventors have found that the above-mentioned problems can be solved by the above and completed the following invention.
　すなわち、本発明は、次の［１］～［１５］を提供するものである。
［１］樹脂フィルム又は発泡体からなる第１の樹脂層、発泡体からなる第２の樹脂層、及び樹脂フィルム又は発泡体からなる第３の樹脂層をこの順に備え、曲率半径（Ｒ）が１５２．４ｍｍである場合に下記式（１）で規定される前記第３の樹脂層の曲げ応力が１．６ＭＰａ以下である多層発泡体シート。
　第３の樹脂層の曲げ応力＝Ｄ×Ｓ／Ｒ　・・・（１）
　Ｄ：第３の樹脂層のＭＤ方向の引張弾性率（ＭＰａ）
　Ｓ：第１の樹脂層の中立点から、第３の樹脂層における第２の樹脂層とは反対側の面までの距離（ｍｍ）
　Ｒ：曲率半径
［２］２５％圧縮強度が８００ｋＰａ以下である、上記［１］に記載の多層発泡体シート。
［３］前記多層発泡体シートの総厚みが５０～２０００μｍである、上記［１］又は［２］に記載の多層発泡体シート。
［４］前記第３の樹脂層のＭＤ方向の引張強度が１．５Ｎ以上である、上記［１］～［３］のいずれか１項に記載の多層発泡体シート。
［５］前記第１の樹脂層と前記第３の樹脂層の合計厚みが、多層発泡体シートの総厚みの５０％以下である、上記［１］～［４］のいずれか１項に記載の多層発泡体シート。
［６］ 曲率半径（Ｒ）が１０１．６ｍｍである場合に上記式（１）で規定される前記第３の樹脂層の曲げ応力が１．６ＭＰａ以下である、上記［１］～［５］のいずれか１項に記載の多層発泡体シート。
［７］曲率半径（Ｒ）が７６．２ｍｍである場合に上記（１）で規定される前記第３の樹脂層の曲げ応力が１．６ＭＰａ以下である、上記［１］～［６］のいずれか１項に記載の多層発泡体シート。
［８］曲率半径（Ｒ２）が１５２．４ｍｍである場合に下記式（２）で規定される前記第１の樹脂層の曲げ応力が１．６ＭＰａ以下である上記［１］～［７］のいずれか１項に記載の多層発泡体シート。
　第１の樹脂層の曲げ応力＝Ｄ２×Ｓ２／Ｒ２　・・・（２）
　Ｄ２：第１の樹脂層のＭＤ方向の引張弾性率（ＭＰａ）
　Ｓ２：第３の樹脂層の中立点から、第１の樹脂層における第２の樹脂層とは反対側の面までの距離（ｍｍ）
　Ｒ２：曲率半径
［９］ 曲率半径（Ｒ２）が１０１．６ｍｍである場合に上記式（２）で規定される前記第１の樹脂層の曲げ応力が１．６ＭＰａ以下である、上記［８］に記載の多層発泡体シート。
［１０］曲率半径（Ｒ２）が７６．２ｍｍである場合に上記式（２）で規定される前記第１の樹脂層の曲げ応力が１．６ＭＰａ以下である、上記［８］又は［９］に記載の多層発泡体シート。
［１１］前記第１の樹脂層の引張強度が１．５Ｎ以上である、上記［１］～［１０］いずれか１項に記載の多層発泡体シート。
［１２］前記第２の樹脂層を構成する樹脂が、ポリオレフィン系樹脂、ポリウレタン系樹脂、アクリル系樹脂、及び熱可塑性エラストマーからなる群から選ばれる１種以上である、上記［１］～［１１］のいずれか１項に記載の多層発泡体シート。
［１３］前記第２の樹脂層を構成する樹脂が、ポリオレフィン樹脂、及び熱可塑性エラストマーからなる群から選ばれる１種以上である、上記［１］～［１２］のいずれか１項に記載の多層発泡体シート。
［１４］前記第１の樹脂層及び前記第３の樹脂層の気泡率が６６％以下である、上記［１］～［１３］のいずれか１項に記載の多層発泡体シート。
［１５］上記［１］～［１４］のいずれか１項に記載の多層発泡体シートと、前記多層発泡体シートの少なくとも一方の面に設けられる粘着材とを備える、粘着テープ。 That is, the present invention provides the following [1] to [15].
[1] A first resin layer made of a resin film or a foam, a second resin layer made of a foam, and a third resin layer made of a resin film or a foam are provided in this order, and the radius of curvature (R) is A multilayer foam sheet in which the bending stress of the third resin layer defined by the following formula (1) when it is 152.4 mm is 1.6 MPa or less.
Bending stress of third resin layer=D×S/R (1)
D: MD tensile modulus of the third resin layer (MPa)
S: Distance from the neutral point of the first resin layer to the surface of the third resin layer opposite to the second resin layer (mm)
R: radius of curvature [2] 25% compressive strength is 800 kPa or less, the multilayer foam sheet according to the above [1].
[3] The multilayer foam sheet according to the above [1] or [2], wherein the total thickness of the multilayer foam sheet is 50 to 2000 μm.
[4] The multilayer foam sheet according to any one of the above [1] to [3], wherein the tensile strength in the MD direction of the third resin layer is 1.5 N or more.
[5] The total thickness of the first resin layer and the third resin layer is 50% or less of the total thickness of the multilayer foam sheet, according to any one of the above [1] to [4]. Multilayer foam sheet.
[6] The bending stress of the third resin layer defined by the above formula (1) is 1.6 MPa or less when the radius of curvature (R) is 101.6 mm, and the above [1] to [5] The multilayer foam sheet according to any one of 1.
[7] In the above [1] to [6], the bending stress of the third resin layer defined in the above (1) is 1.6 MPa or less when the radius of curvature (R) is 76.2 mm. The multilayer foam sheet according to any one of claims.
[8] In the above [1] to [7], when the radius of curvature (R2) is 152.4 mm, the bending stress of the first resin layer defined by the following formula (2) is 1.6 MPa or less. The multilayer foam sheet according to any one of claims.
Bending stress of first resin layer=D2×S2/R2 (2)
D2: MD elastic modulus of the first resin layer (MPa)
S2: Distance from the neutral point of the third resin layer to the surface of the first resin layer on the side opposite to the second resin layer (mm)
R2: radius of curvature [9] When the radius of curvature (R2) is 101.6 mm, the bending stress of the first resin layer defined by the above formula (2) is 1.6 MPa or less, [8] The multilayer foam sheet according to.
[10] The bending stress of the first resin layer defined by the above formula (2) is 1.6 MPa or less when the radius of curvature (R2) is 76.2 mm, [8] or [9] above. The multilayer foam sheet according to.
[11] The multilayer foam sheet according to any one of the above [1] to [10], wherein the tensile strength of the first resin layer is 1.5 N or more.
[12] The above-mentioned [1] to [11], in which the resin constituting the second resin layer is one or more selected from the group consisting of a polyolefin resin, a polyurethane resin, an acrylic resin, and a thermoplastic elastomer. ] The multilayer foam sheet according to any one of [1].
[13] The resin according to any one of the above [1] to [12], wherein the resin forming the second resin layer is at least one selected from the group consisting of a polyolefin resin and a thermoplastic elastomer. Multilayer foam sheet.
[14] The multilayer foam sheet according to any one of the above [1] to [13], wherein the first resin layer and the third resin layer have a bubble ratio of 66% or less.
[15] An adhesive tape comprising the multilayer foam sheet according to any one of the above [1] to [14] and an adhesive material provided on at least one surface of the multilayer foam sheet.
　本発明によれば、柔軟性と機械強度とを良好にしつつ、折れジワなどの外観不良を抑制することができる多層発泡体シートを提供することが可能である。 According to the present invention, it is possible to provide a multilayer foam sheet that can suppress appearance defects such as folds and wrinkles while improving flexibility and mechanical strength.
多層発泡体シートの一実施形態を示す断面図である。It is sectional drawing which shows one Embodiment of a multilayer foam sheet. 多層発泡体シートの別の一実施形態を示す断面図である。It is sectional drawing which shows another embodiment of a multilayer foam sheet.
　以下、本発明について実施形態を用いて詳細に説明する。
［多層発泡体シート］
　本発明の多層発泡体シートは、樹脂フィルム又は発泡体からなる第１の樹脂層、発泡体からなる第２の樹脂層（基材層）、及び樹脂フィルム又は発泡体からなる第３の樹脂層をこの順に備える。なお、以下の説明においては、説明の簡略化のために、第１～第３の樹脂層をそれぞれ、第１～第３の層ということがある。 Hereinafter, the present invention will be described in detail with reference to embodiments.
[Multilayer foam sheet]
The multilayer foam sheet of the present invention includes a first resin layer made of a resin film or foam, a second resin layer (base material layer) made of foam, and a third resin layer made of resin film or foam. Are provided in this order. In the following description, the first to third resin layers may be referred to as first to third layers for the sake of simplicity.
　本発明では、図１に示すように、多層発泡体シート１０は、３層からなり、第２の層１２の両面に、第１の層１１及び第３の層１３が直接積層されてもよい。また、図２に示すように、多層発泡体シート１０は、第１～第３の層１１、１２、１３を備えるとともに、粘着剤層、接着剤層などの接着層１４、１５を介して第２の層１２の両面に、第１の層１１、第３の層１３それぞれが積層されてもよい。図１，２に示すように、第１及び第３の層１１、１３は、多層発泡体シート１０において最外層となるとよい。 In the present invention, as shown in FIG. 1, the multilayer foam sheet 10 is composed of three layers, and the first layer 11 and the third layer 13 may be directly laminated on both surfaces of the second layer 12. .. In addition, as shown in FIG. 2, the multilayer foam sheet 10 includes first to third layers 11, 12 and 13, and a first adhesive layer, an adhesive layer, and other adhesive layers 14 and 15 interposed therebetween. Each of the first layer 11 and the third layer 13 may be laminated on both surfaces of the second layer 12. As shown in FIGS. 1 and 2, the first and third layers 11 and 13 may be outermost layers in the multilayer foam sheet 10.
　本発明の多層発泡体シートは、曲率半径（Ｒ）が１５２．４ｍｍである場合に下記式（１）で規定される第３の層の曲げ応力が１．６ＭＰａ以下となるものである。
　第３の層の曲げ応力＝Ｄ×Ｓ／Ｒ　・・・（１）
　Ｄ：第３の層のＭＤ方向の引張弾性率（ＭＰａ）
　Ｓ：第１の層の中立点から、第３の層における第２の層とは反対側の面までの距離（ｍｍ）
　Ｒ：曲率半径
　なお、中立点とは、図１、２に示すとおり、第１の層１１の厚さ方向の中間点Ｃであり、距離Ｓは、中間点Ｃから第３の層１３の表面１３Ａまでの距離である。 In the multilayer foam sheet of the present invention, the bending stress of the third layer defined by the following formula (1) is 1.6 MPa or less when the radius of curvature (R) is 152.4 mm.
Bending stress of third layer=D×S/R (1)
D: Tensile elastic modulus (MPa) of the third layer in the MD direction
S: Distance from the neutral point of the first layer to the surface of the third layer on the side opposite to the second layer (mm)
R: radius of curvature Note that the neutral point is, as shown in FIGS. 1 and 2, an intermediate point C in the thickness direction of the first layer 11, and a distance S is from the intermediate point C to the surface of the third layer 13. It is the distance to 13A.
　多層発泡体シートは、一般的に紙芯等の巻芯に巻き付けられて保管されるが、その際に巻芯側の層と反対側の層との曲率半径に差が生じるため、巻芯側の層に折れジワが生じてしまう。これに対して本発明では、多層発泡体シートの一方の面の曲げ応力を特定の範囲に調整されているため、多層発泡体シートの少なくとも一方の面が十分に柔軟になり、巻芯に巻き付けても折れジワの発生を抑制することが可能になる。
　なお、本発明において「ＭＤ」は、Ｍａｃｈｉｎｅ　Ｄｉｒｅｃｔｉｏｎを意味し、フィルム層の押出方向等と一致する方向を意味する。 The multilayer foam sheet is generally wound around a core such as a paper core and stored, but at that time, a radius of curvature differs between the layer on the core side and the layer on the opposite side. Wrinkles will occur in the layer. On the other hand, in the present invention, since the bending stress of one surface of the multilayer foam sheet is adjusted to a specific range, at least one surface of the multilayer foam sheet becomes sufficiently flexible and is wound around the winding core. Even if it is, it becomes possible to suppress the generation of creases.
In addition, in this invention, "MD" means Machine Direction and means the direction which corresponds with the extrusion direction etc. of a film layer.
　上記式（１）は、所定の曲率半径で第３の層を曲げた時の曲げ応力が１．６ＭＰａ以下であることを意味する。したがって、本発明の多層発泡体シートは、半径が１５２．４ｍｍ（６インチ）である紙芯等の巻芯に巻き付けても、曲げ応力が１．６ＭＰａ以下しか作用されず、それにより、折れジワの発生を抑制することが可能になる。なお、半径６インチの紙芯は、発泡体シートなどを巻き取る巻芯として汎用的に使用されるものである。
　さらに、本発明の多層発泡体シートは、樹脂層を３層有する多層構造であるので、柔軟性と機械強度の両方を良好にしやすくなる。
　本発明において、曲率半径が１５２．４ｍｍ（６インチ）である場合の第３の層の曲げ応力は、折れジワを十分に抑制する観点から、より好ましくは１．５５ＭＰａ以下、更に好ましくは１．０ＭＰａ以下、より更に好ましくは０．６ＭＰａ以下である。また、曲率半径が１５２．４ｍｍ（６インチ）である場合の曲げ応力は、第３の層に一定以上の引張強度を付与するために、０．１ＭＰａ以上が好ましく、０．２ＭＰａ以上がより好ましい。 The above formula (1) means that the bending stress when the third layer is bent with a predetermined radius of curvature is 1.6 MPa or less. Therefore, the multilayer foam sheet of the present invention has a bending stress of only 1.6 MPa or less even when it is wound around a core such as a paper core having a radius of 152.4 mm (6 inches), thereby causing a crease. It is possible to suppress the occurrence of. The paper core having a radius of 6 inches is generally used as a core for winding a foam sheet or the like.
Furthermore, since the multilayer foam sheet of the present invention has a multilayer structure having three resin layers, it is easy to improve both flexibility and mechanical strength.
In the present invention, the bending stress of the third layer when the radius of curvature is 152.4 mm (6 inches) is more preferably 1.55 MPa or less, and further preferably 1.5 MPa or less from the viewpoint of sufficiently suppressing creases. It is 0 MPa or less, more preferably 0.6 MPa or less. In addition, the bending stress when the radius of curvature is 152.4 mm (6 inches) is preferably 0.1 MPa or more, and more preferably 0.2 MPa or more, in order to give the third layer a certain tensile strength or more. ..
　本発明では、式（１）で算出される第３の層の曲げ応力は、曲率半径（Ｒ）が１０１．６ｍｍ（４インチ）である場合においても、１．６ＭＰａ以下であることが好ましい。多層発泡体シートの巻取りにおいて、紙芯などの巻芯は、半径４インチ程度のさらに小径のものが使用されることがあるが、上記のように、曲率半径が１０１．６ｍｍである場合でも１．６ＭＰａ以下であると、小径の巻芯に巻き取っても折れジワが生じることがない。 In the present invention, the bending stress of the third layer calculated by the formula (1) is preferably 1.6 MPa or less even when the radius of curvature (R) is 101.6 mm (4 inches). In winding the multilayer foam sheet, a core such as a paper core having a radius of about 4 inches and a smaller diameter may be used. However, as described above, even when the radius of curvature is 101.6 mm. When the pressure is 1.6 MPa or less, a crease does not occur even when wound around a winding core having a small diameter.
　また、式（１）で算出される第３の層の曲げ応力は、曲率半径が７６．２ｍｍ（３インチ）である場合においても、１．６ＭＰａ以下であることがより好ましい。多層発泡体シートの巻取りにおいて、紙芯などの巻芯は、汎用的に極小径の半径３インチ程度のものが使用されるが、上記のように、曲率半径が７６．２ｍｍである場合でも曲げ応力が１．６ＭＰａ以下であると、極小径の巻芯に巻き取っても折れジワが生じることがない。 Further, the bending stress of the third layer calculated by the formula (1) is more preferably 1.6 MPa or less even when the radius of curvature is 76.2 mm (3 inches). In winding the multi-layer foam sheet, a core such as a paper core is generally used that has a minimum diameter of about 3 inches, but as described above, even when the radius of curvature is 76.2 mm. When the bending stress is 1.6 MPa or less, a crease does not occur even when wound on a winding core having an extremely small diameter.
　なお、上記のように、基材層（第２の層）の両面に、樹脂フィルム又は発泡体が設けられる多層発泡体シートは、両面に設けられた樹脂フィルム又は発泡体のうち、任意の一方が第１の層となり、任意の他方が第３の層となる。したがって、本発明では、両面に設けられた樹脂フィルム又は発泡体のうち一方が、式（１）で算出される曲げ応力が１．６ＭＰａ以下であるとよい。一方の層（すなわち、第３の層）の曲げ応力が１．６ＭＰａ以下であると、その第３の層を巻芯側（内側）になるように巻き取れば折れジワが発生しないからである。 As described above, the multilayer foam sheet in which the resin film or the foam is provided on both sides of the base material layer (second layer) is any one of the resin films or the foam provided on both sides. Is the first layer, and the other is the third layer. Therefore, in the present invention, it is preferable that one of the resin film or the foam provided on both surfaces has a bending stress calculated by the formula (1) of 1.6 MPa or less. This is because if the bending stress of one layer (that is, the third layer) is 1.6 MPa or less, creases will not occur if the third layer is wound so as to be on the winding core side (inside). ..
　ただし、本発明では、両面に設けられた樹脂フィルム又は発泡体のいずれも（すなわち、第１の層及び第３の層のいずれも）曲げ応力が１．６ＭＰａ以下であることが好ましい。すなわち、曲率半径（Ｒ２）が１５２．４ｍｍである場合に下記式（２）で規定される第１の層の曲げ応力が１．６ＭＰａ以下であることが好ましい。
　第１の層の曲げ応力＝Ｄ２×Ｓ２／Ｒ２　・・・（２）
　Ｄ２：第１の層のＭＤ方向の引張弾性率（ＭＰａ）
　Ｓ２：第３の層の中立点から、第１の層における第２の層とは反対側の面までの距離（ｍｍ）
　Ｒ２：曲率半径
　式（２）における中立点とは、図１、２に示すとおり、第３の層１３の厚さ方向の中間点Ｃ２であり、距離Ｓ２は、中間点Ｃ２から第１の層１１の表面１１Ａまでの距離である。 However, in the present invention, it is preferable that both the resin film and the foam provided on both surfaces (that is, both the first layer and the third layer) have a bending stress of 1.6 MPa or less. That is, when the radius of curvature (R2) is 152.4 mm, the bending stress of the first layer defined by the following formula (2) is preferably 1.6 MPa or less.
Bending stress of the first layer=D2×S2/R2 (2)
D2: tensile modulus in the MD direction of the first layer (MPa)
S2: Distance from the neutral point of the third layer to the surface of the first layer opposite to the second layer (mm)
R2: radius of curvature The neutral point in the equation (2) is the midpoint C2 in the thickness direction of the third layer 13 as shown in FIGS. 1 and 2, and the distance S2 is from the midpoint C2 to the first layer. 11 is the distance to the surface 11A.
　多層発泡体シートは、第１及び第３の層の曲げ応力がいずれも１．６ＭＰａ以下となることで、第１及び第３の層のいずれを、巻芯側（内側）になるように巻き取っても折れジワが発生しなくなるので、多層発泡体シートの巻取りを制限なく行うことができる。
　本発明において、曲率半径が１５２．４ｍｍ（６インチ）である場合の第１の層の曲げ応力は、折れジワを十分に抑制する観点から、より好ましくは１．５５ＭＰａ以下、更に好ましくは１．０ＭＰａ以下、より更に好ましくは０．６ＭＰａ以下である。また、曲率半径が１５２．４ｍｍ（６インチ）である場合の第１の層の曲げ応力は、第１の層に一定以上の引張強度を付与するために、０．１ＭＰａ以上が好ましく、０．２ＭＰａ以上がより好ましい。 In the multilayer foam sheet, the bending stress of both the first and third layers is 1.6 MPa or less, so that both the first and third layers are wound so as to be on the winding core side (inner side). Since wrinkles do not occur even when taken, the multilayer foam sheet can be wound without limitation.
In the present invention, the bending stress of the first layer when the radius of curvature is 152.4 mm (6 inches) is more preferably 1.55 MPa or less, and further preferably 1.5 MPa or less from the viewpoint of sufficiently suppressing creases. It is 0 MPa or less, more preferably 0.6 MPa or less. Further, when the radius of curvature is 152.4 mm (6 inches), the bending stress of the first layer is preferably 0.1 MPa or more in order to give the first layer a certain tensile strength or more, 2 MPa or more is more preferable.
　小径の巻芯に対しても、多層発泡体シートの巻取りを制限なく行うことができる観点から、式（２）で算出される第１の層の曲げ応力は、曲率半径（Ｒ２）が１０１．６ｍｍ（４インチ）である場合においても、１．６ＭＰａ以下であることがより好ましい。また、極小径の巻芯に対しても、多層発泡体シートの巻取りを制限なく行うことができる観点から、式（２）で算出される第１の層の曲げ応力は、曲率半径が７６．２ｍｍ（３インチ）である場合においても、１．６ＭＰａ以下であることがさらに好ましい。 The bending stress of the first layer calculated by the equation (2) has a radius of curvature (R2) of 101 even from the viewpoint that the winding of the multilayer foam sheet can be performed without limitation on a winding core having a small diameter. Even when it is 0.6 mm (4 inches), it is more preferably 1.6 MPa or less. Further, from the viewpoint that the multi-layer foam sheet can be wound around the winding core having an extremely small diameter without limitation, the bending stress of the first layer calculated by the formula (2) has a radius of curvature of 76. Even in the case of 0.2 mm (3 inches), the pressure is more preferably 1.6 MPa or less.
〔引張弾性率（Ｄ）、（Ｄ２）〕
　本発明の多層発泡体シートは、第３の層のＭＤ方向の引張弾性率（Ｄ）が、４０～５００ＭＰａが好ましく、６０～４５０ＭＰａがより好ましく、１５０～４００ＭＰａが更に好ましい。第３の層の引張弾性率（Ｄ）を上記範囲内とすることで、圧縮強度などを良好にしつつ、曲げ応力も高めやすくなる。
　同様の観点から、第１の層のＭＤ方向の引張弾性率（Ｄ２）は、４０～５００ＭＰａが好ましく、６０～４５０ＭＰａがより好ましく、１５０～４００ＭＰａが更に好ましい。
　なお、第１の層、及び第３の層のＭＤ方向の引張弾性率は、実施例で記載されるとおりに測定して求めるとよい。 [Tensile modulus (D), (D2)]
In the multilayer foam sheet of the present invention, the tensile elastic modulus (D) of the third layer in the MD direction is preferably 40 to 500 MPa, more preferably 60 to 450 MPa, still more preferably 150 to 400 MPa. By setting the tensile elastic modulus (D) of the third layer within the above range, the bending stress can be easily increased while improving the compressive strength and the like.
From the same viewpoint, the tensile elastic modulus (D2) in the MD direction of the first layer is preferably 40 to 500 MPa, more preferably 60 to 450 MPa, still more preferably 150 to 400 MPa.
The tensile elastic moduli of the first layer and the third layer in the MD direction may be obtained by measuring as described in the examples.
〔第１の層及び第３の層の引張強度〕
　本発明の多層発泡体シートは、例えば、第３の層のＭＤ方向の引張強度が１．５Ｎ以上であるが、２．５Ｎ以上であることが好ましい。第３の層の引張強度を２．５Ｎ以上とすると、折れジワを生じさせず、かつ多層発泡体シートの柔軟性を維持しつつ、機械強度を向上させることが可能になる。これら観点から、第３の層のＭＤ方向の引張強度は４Ｎ以上がより好ましい。また、上記引張強度は、曲げ応力を一定以下とする観点から、例えば、２００Ｎ以下とするとよく、好ましくは１００Ｎ以下である。 [Tensile Strength of First Layer and Third Layer]
In the multilayer foam sheet of the present invention, for example, the tensile strength of the third layer in the MD direction is 1.5 N or more, and preferably 2.5 N or more. When the tensile strength of the third layer is 2.5 N or more, it is possible to improve the mechanical strength without causing creases and maintaining the flexibility of the multilayer foam sheet. From these viewpoints, the tensile strength in the MD direction of the third layer is more preferably 4N or more. The tensile strength is, for example, 200 N or less, and preferably 100 N or less, from the viewpoint of keeping the bending stress constant or less.
　多層発泡体シートは、例えば、第１の層のＭＤ方向の引張強度が１．５Ｎ以上であるが、柔軟性を維持しつつ、機械強度を向上させる観点からは、２．５Ｎ以上が好ましい。また、第１及び第３の層の両方のＭＤ方向の引張強度が２．５Ｎ以上であることも好ましい。第１及び第３の層の両方の引張強度を２．５Ｎ以上とすると、多層発泡体シートの機械強度をより向上させやすくなる。
　第１の層のＭＤ方向の引張強度は、４Ｎ以上がより好ましく、第１及び第３の層の両方のＭＤ方向の引張強度が４Ｎ以上であることがさらに好ましい。また、引張強度は、曲げ応力を一定以下とする観点から、例えば、２００Ｎ以下とするとよく、好ましくは１００Ｎ以下である。
　なお、引張強度は、ＪＩＳ　Ｋ６７６７に準拠して測定することができる。 In the multilayer foam sheet, for example, the tensile strength in the MD direction of the first layer is 1.5 N or more, but from the viewpoint of improving mechanical strength while maintaining flexibility, 2.5 N or more is preferable. It is also preferable that the tensile strengths in the MD direction of both the first and third layers are 2.5 N or more. When the tensile strengths of both the first and third layers are 2.5 N or more, it becomes easier to improve the mechanical strength of the multilayer foam sheet.
The tensile strength in the MD direction of the first layer is more preferably 4N or more, and further preferably, the tensile strength in the MD direction of both the first and third layers is 4N or more. Further, the tensile strength may be, for example, 200 N or less, and preferably 100 N or less, from the viewpoint of keeping the bending stress below a certain level.
The tensile strength can be measured according to JIS K6767.
＜多層発泡体シートの２５％圧縮強度＞
　本発明の多層発泡体シートの２５％圧縮強度は８００ｋＰａ以下であることが好ましい。多層発泡体シートの２５％圧縮強度が８００ｋＰａ以下であると、多層発泡体シートの柔軟性が向上すると共に、衝撃吸収性等も向上する。さらに、追従性に優れるため、粘着テープの基材として使用した場合には、粘着テープの接着力が向上しやすい。これら観点から、多層発泡体シートの２５％圧縮強度は、好ましくは７００ｋＰａ以下であり、より好ましくは３００ｋＰａ以下であり、更に好ましくは１００ｋＰａ以下である。
　また、多層発泡体シートの２５％圧縮強度は、好ましくは２０ｋＰａ以上、より好ましくは３０ｋＰａ以上、さらに好ましくは４０ｋＰａ以上である。これら下限値以上とすることで、必要以上に柔軟性が高くなりすぎるのを防止し、多層発泡体シートの機械強度などを高めやすくなる。
　２５％圧縮強度はＪＩＳ　Ｋ６７６７に準拠して測定することができる。 <25% compressive strength of multilayer foam sheet>
The 25% compressive strength of the multilayer foam sheet of the present invention is preferably 800 kPa or less. When the 25% compressive strength of the multilayer foam sheet is 800 kPa or less, the flexibility of the multilayer foam sheet is improved, and the impact absorbency and the like are also improved. Further, since the followability is excellent, the adhesive strength of the adhesive tape is easily improved when it is used as a base material of the adhesive tape. From these viewpoints, the 25% compressive strength of the multilayer foam sheet is preferably 700 kPa or less, more preferably 300 kPa or less, and further preferably 100 kPa or less.
The 25% compressive strength of the multilayer foam sheet is preferably 20 kPa or more, more preferably 30 kPa or more, still more preferably 40 kPa or more. By setting the content to the lower limit or more, it is possible to prevent the flexibility from becoming too high, and it becomes easy to increase the mechanical strength and the like of the multilayer foam sheet.
The 25% compressive strength can be measured according to JIS K6767.
〔各層の厚み、及び厚み比率〕
　多層発泡体シートの総厚みは、特に制限されないが、５０～２０００μｍであることが好ましく、８０～１８００μｍであることがより好ましく、１５０～１２００μｍであることが更に好ましい。多層発泡体シートの総厚みをこのような範囲にすることにより多層発泡体シートの薄型化が可能となると共に、柔軟性及び機械強度が良好な多層発泡体シートを得やすくなる。 [Thickness of each layer, and thickness ratio]
The total thickness of the multilayer foam sheet is not particularly limited, but is preferably 50 to 2000 μm, more preferably 80 to 1800 μm, and further preferably 150 to 1200 μm. By making the total thickness of the multilayer foam sheet within such a range, it becomes possible to make the multilayer foam sheet thin and it becomes easy to obtain a multilayer foam sheet having good flexibility and mechanical strength.
　本発明においては、第１の層及び第３の層の合計厚みは、多層発泡体シートの総厚みの５０％以下が好ましく、３０％以下であることが好ましく、２５％以下であることがさらに好ましい。合計厚みを上記範囲内とすることにより、折れジワの発生を抑制しつつ、圧縮強度を低くして柔軟性を高めやすくなる。また、機械強度を高める観点から、上記合計厚さは、多層発泡体シートの総厚みの２％以上が好ましく、４％以上がより好ましく、７％以上がさらに好ましい。
　なお、図１に示すように、多層発泡体シート１０の総厚みとは、第１の層１１、第２の層１２、及び第３の層１３の３層構造の場合は当該３層の合計の厚みＴ１である。また、図２に示すように、総厚みは、第１の層１１と第２の層１２、又は第２の層１２と第３の層１３との間に層（接着層１４、１５）が存在する場合は、第１～第３の層１１～１３の合計厚みに接着層１４、１５の厚みを加えた厚みＴ２である。 In the present invention, the total thickness of the first layer and the third layer is preferably 50% or less, more preferably 30% or less, and further preferably 25% or less of the total thickness of the multilayer foam sheet. preferable. By setting the total thickness within the above range, it is easy to increase the flexibility by suppressing the compressive strength while suppressing the generation of creases. Further, from the viewpoint of increasing the mechanical strength, the total thickness is preferably 2% or more, more preferably 4% or more, still more preferably 7% or more of the total thickness of the multilayer foam sheet.
As shown in FIG. 1, the total thickness of the multilayer foam sheet 10 is the total of the three layers in the case of the three-layer structure of the first layer 11, the second layer 12, and the third layer 13. Is T1. In addition, as shown in FIG. 2, the total thickness is equal to that between the first layer 11 and the second layer 12 or between the second layer 12 and the third layer 13 (adhesive layers 14 and 15). When present, the thickness T2 is the total thickness of the first to third layers 11 to 13 plus the thickness of the adhesive layers 14 and 15.
　第１の層及び第３の層それぞれの厚みは、好ましくは１～５００μｍ、より好ましくは５～２５０μｍ、更に好ましくは１０～９０μｍである。このような範囲であると、多層発泡体シートの薄型化が可能となる。また、第１の層及び第３の層の引張強度、及び多層発泡体シートの２５％圧縮強度を上記範囲内に調整しやすくなる。なお、第１の層及び第３の層の厚みは、同一であっても異なっていてもよい。 The thickness of each of the first layer and the third layer is preferably 1 to 500 μm, more preferably 5 to 250 μm, and further preferably 10 to 90 μm. Within such a range, the multilayer foam sheet can be made thinner. Moreover, it becomes easy to adjust the tensile strength of the first layer and the third layer and the 25% compressive strength of the multilayer foam sheet within the above range. The thicknesses of the first layer and the third layer may be the same or different.
　第２の層の厚みは、特に制限されないが、４０～１９００μｍであることが好ましく、７０～１６００μｍであることがより好ましく、１００～１０００μｍであることが更に好ましい。第２の層の厚みをこのような範囲内にすることにより多層発泡体シートの薄型化が可能となると共に、柔軟性が良好な多層発泡体シートを得やすくなる。なお、第２の層の厚みは、典型的には第１及び第３の層それぞれの厚みよりも大きくなる。第２の層の厚みを第１及び第３の層それぞれよりも厚くすることで、多層発泡体シートの柔軟性を高くしやすくなる。 The thickness of the second layer is not particularly limited, but is preferably 40 to 1900 μm, more preferably 70 to 1600 μm, and further preferably 100 to 1000 μm. By setting the thickness of the second layer within such a range, it becomes possible to make the multilayer foam sheet thin and it is easy to obtain a multilayer foam sheet having good flexibility. The thickness of the second layer is typically larger than the thickness of each of the first and third layers. By making the thickness of the second layer larger than that of each of the first and third layers, it becomes easy to increase the flexibility of the multilayer foam sheet.
　以下、第１～第３の層についてより詳細に説明する。
＜第２の層＞
　本発明の第２の層は、樹脂発泡体からなる。第２の層を構成する樹脂の種類は特に限定されないが、ポリオレフィン系樹脂、アクリル系樹脂、ポリウレタン系樹脂、及び熱可塑性エラストマー等が挙げられる。これらは１種単独で使用してもよいし、２種以上を併用してもよい。これらの中ではポリオレフィン系樹脂、熱可塑性エラストマーが好ましく、ポリオレフィン系樹脂がより好ましい。ポリオレフィン系樹脂、熱可塑性エラストマーを使用することで、発泡性等を良好にしつつ、第２の層の柔軟性及び機械強度等を確保しやすくなる。第２の層に使用する樹脂は、１種単独で使用してもよいし、２種以上を併用してもよい。 Hereinafter, the first to third layers will be described in more detail.
<Second layer>
The second layer of the present invention is made of resin foam. The type of resin forming the second layer is not particularly limited, but examples thereof include polyolefin-based resin, acrylic resin, polyurethane-based resin, and thermoplastic elastomer. These may be used alone or in combination of two or more. Of these, polyolefin resins and thermoplastic elastomers are preferable, and polyolefin resins are more preferable. By using the polyolefin resin and the thermoplastic elastomer, it becomes easy to secure the flexibility and mechanical strength of the second layer while improving the foamability and the like. The resin used in the second layer may be used alone or in combination of two or more.
　ポリオレフィン系樹脂は、熱可塑性樹脂であり、その具体例としてはポリエチレン樹脂、ポリプロピレン樹脂、エチレン－酢酸ビニル共重合体等が挙げられ、これらの中ではポリエチレン樹脂が好ましい。
　ポリエチレン樹脂としては、チーグラー・ナッタ化合物、メタロセン触媒、酸化クロム化合物等の重合触媒で重合されたポリエチレン樹脂が挙げられ、好ましくは、メタロセン触媒で重合されたポリエチレン樹脂が用いられる。 The polyolefin resin is a thermoplastic resin, and specific examples thereof include polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer, and the like, and among these, polyethylene resin is preferable.
Examples of the polyethylene resin include polyethylene resins polymerized with a polymerization catalyst such as a Ziegler-Natta compound, a metallocene catalyst and a chromium oxide compound, and preferably a polyethylene resin polymerized with a metallocene catalyst is used.
（メタロセン触媒）
　メタロセン触媒としては、遷移金属をπ電子系の不飽和化合物で挟んだ構造を有するビス（シクロペンタジエニル）金属錯体等の化合物を挙げることができる。より具体的には、チタン、ジルコニウム、ニッケル、パラジウム、ハフニウム、及び白金等の四価の遷移金属に、１又は２以上のシクロペンタジエニル環又はその類縁体がリガンド（配位子）として存在する化合物を挙げることができる。
　このようなメタロセン触媒は、活性点の性質が均一であり各活性点が同じ活性度を備えている。メタロセン触媒を用いて合成した重合体は、分子量、分子量分布、組成、組成分布等の均一性が高いため、メタロセン触媒を用いて合成した重合体を含むシートを架橋した場合には、架橋が均一に進行する。均一に架橋されたシートは、均一に発泡されるため、物性を安定させやすくなる。また、均一に延伸できるため、発泡体の厚さを均一にできる。 (Metallocene catalyst)
Examples of the metallocene catalyst include compounds such as a bis(cyclopentadienyl) metal complex having a structure in which a transition metal is sandwiched by π-electron unsaturated compounds. More specifically, tetravalent transition metals such as titanium, zirconium, nickel, palladium, hafnium, and platinum have one or more cyclopentadienyl rings or their analogs as ligands. The compound can be mentioned.
Such a metallocene catalyst has uniform properties of active sites and each active site has the same activity. Polymers synthesized using a metallocene catalyst have high homogeneity in molecular weight, molecular weight distribution, composition, composition distribution, etc. Therefore, when a sheet containing a polymer synthesized using a metallocene catalyst is crosslinked, the crosslinking is uniform. Proceed to. Since the uniformly crosslinked sheet is uniformly foamed, it becomes easy to stabilize the physical properties. Further, since the film can be stretched uniformly, the thickness of the foam can be made uniform.
　リガンドとしては、例えば、シクロペンタジエニル環、インデニル環等を挙げることができる。これらの環式化合物は、炭化水素基、置換炭化水素基又は炭化水素－置換メタロイド基により置換されていてもよい。炭化水素基としては、例えば、メチル基、エチル基、各種プロピル基、各種ブチル基、各種アミル基、各種ヘキシル基、２－エチルヘキシル基、各種ヘプチル基、各種オクチル基、各種ノニル基、各種デシル基、各種セチル基、フェニル基等が挙げられる。なお、「各種」とは、ｎ－、ｓｅｃ－、ｔｅｒｔ－、ｉｓｏ－を含む各種異性体を意味する。
　また、環式化合物をオリゴマーとして重合したものをリガンドとして用いてもよい。
　さらに、π電子系の不飽和化合物以外にも、塩素や臭素等の一価のアニオンリガンド又は二価のアニオンキレートリガンド、炭化水素、アルコキシド、アリールアミド、アリールオキシド、アミド、アリールアミド、ホスフィド、アリールホスフィド等を用いてもよい。 Examples of the ligand include a cyclopentadienyl ring and an indenyl ring. These cyclic compounds may be substituted with a hydrocarbon group, a substituted hydrocarbon group or a hydrocarbon-substituted metalloid group. Examples of the hydrocarbon group include a methyl group, an ethyl group, various propyl groups, various butyl groups, various amyl groups, various hexyl groups, 2-ethylhexyl groups, various heptyl groups, various octyl groups, various nonyl groups, various decyl groups. , Various cetyl groups, phenyl groups and the like. In addition, "various" means various isomers including n-, sec-, tert-, and iso-.
Moreover, what polymerized the cyclic compound as an oligomer may be used as a ligand.
In addition to π-electron unsaturated compounds, monovalent anion ligands such as chlorine and bromine or divalent anion chelate ligands, hydrocarbons, alkoxides, arylamides, aryloxides, amides, arylamides, phosphides, aryls. You may use phosphide etc.
　四価の遷移金属やリガンドを含むメタロセン触媒としては、例えば、シクロペンタジエニルチタニウムトリス（ジメチルアミド）、メチルシクロペンタジエニルチタニウムトリス（ジメチルアミド）、ビス（シクロペンタジエニル）チタニウムジクロリド、ジメチルシリルテトラメチルシクロペンタジエニル－ｔ－ブチルアミドジルコニウムジクロリド等が挙げられる。
　メタロセン触媒は、特定の共触媒（助触媒）と組み合わせることにより、各種オレフィンの重合の際に触媒としての作用を発揮する。具体的な共触媒としては、メチルアルミノキサン（ＭＡＯ）、ホウ素系化合物等が挙げられる。なお、メタロセン触媒に対する共触媒の使用割合は、１０～１００万モル倍が好ましく、５０～５，０００モル倍がより好ましい。 Examples of the metallocene catalyst containing a tetravalent transition metal or a ligand include cyclopentadienyl titanium tris(dimethylamide), methylcyclopentadienyl titanium tris(dimethylamide), bis(cyclopentadienyl)titanium dichloride, and dimethyl. Examples thereof include silyltetramethylcyclopentadienyl-t-butylamide zirconium dichloride.
The metallocene catalyst, when combined with a specific co-catalyst (co-catalyst), exhibits an action as a catalyst during the polymerization of various olefins. Specific examples of cocatalysts include methylaluminoxane (MAO) and boron compounds. The ratio of the cocatalyst used to the metallocene catalyst is preferably 100 to 1,000,000 mol times, more preferably 50 to 5,000 mol times.
　また、ポリエチレン樹脂としては、直鎖状低密度ポリエチレンが好ましい。直鎖状低密度ポリエチレンは、エチレン（例えば、全モノマー量に対して７５質量％以上、好ましくは９０質量％以上）と必要に応じて少量のα－オレフィンとを共重合することにより得られる直鎖状低密度ポリエチレンがより好ましい。α－オレフィンとして、具体的には、プロピレン、１－ブテン、１－ペンテン、４－メチル－１－ペンテン、１－ヘキセン、１－ヘプテン、及び１－オクテン等が挙げられる。なかでも、炭素数４～１０のα－オレフィンが好ましい。
　ポリエチレン樹脂、例えば上記した直鎖状低密度ポリエチレンの密度は、柔軟性の観点から、０．８７０～０．９２５ｇ／ｃｍ３が好ましく、０．８９０～０．９２５ｇ／ｃｍ３がより好ましく、０．９１０～０．９２５ｇ／ｃｍ３が更に好ましい。ポリエチレン樹脂としては、複数のポリエチレン樹脂を用いることもでき、また、上記した密度範囲以外のポリエチレン樹脂を加えてもよい。 As the polyethylene resin, linear low density polyethylene is preferable. The linear low-density polyethylene is obtained directly by copolymerizing ethylene (for example, 75% by mass or more, preferably 90% by mass or more with respect to the total amount of monomers) and a small amount of α-olefin as necessary. Chain low density polyethylene is more preferable. Specific examples of the α-olefin include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and the like. Of these, α-olefins having 4 to 10 carbon atoms are preferable.
Polyethylene resin, for example the density of the above-mentioned linear low density polyethylene, from the viewpoint of flexibility, preferably 0.870 ~ 0.925g / cm 3, more preferably 0.890 ~ 0.925g / cm 3, 0 It is more preferably 0.910 to 0.925 g/cm 3 . As the polyethylene resin, a plurality of polyethylene resins may be used, and a polyethylene resin having a density outside the above range may be added.
　ポリオレフィン系樹脂として使用するエチレン－酢酸ビニル共重合体は、例えば、エチレンを５０質量％以上含有するエチレン－酢酸ビニル共重合体が挙げられる。
　また、ポリプロピレン樹脂としては、例えば、ホモポリプロピレン、プロピレンを５０質量％以上含有するプロピレン－α－オレフィン共重合体等が挙げられる。これらは１種を単独で用いてもよく、２種以上を併用してもよい。プロピレン－α－オレフィン共重合体を構成するα－オレフィンとしては、具体的には、エチレン、１－ブテン、１－ペンテン、４－メチル－１－ペンテン、１－ヘキセン、１－ヘプテン、１－オクテン等が挙げることができ、これらの中では、炭素数６～１２のα－オレフィンが好ましい。 Examples of the ethylene-vinyl acetate copolymer used as the polyolefin resin include an ethylene-vinyl acetate copolymer containing 50% by mass or more of ethylene.
Examples of the polypropylene resin include homopolypropylene and a propylene-α-olefin copolymer containing 50% by mass or more of propylene. These may be used alone or in combination of two or more. Specific examples of the α-olefin constituting the propylene-α-olefin copolymer include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1- Examples thereof include octene, and of these, α-olefin having 6 to 12 carbon atoms is preferable.
　熱可塑性エラストマーとしては、オレフィン系熱可塑性エラストマー、スチレン系熱可塑性エラストマー、塩化ビニル系熱可塑性エラストマー、ポリウレタン系熱可塑性エラストマー、ポリエステル系熱可塑性エラストマー、ポリアミド系熱可塑性エラストマー等が挙げられる。熱可塑性エラストマーは、これら成分を１種単独で用いてもよく、２種以上を併用してもよい。
　これらの中では、オレフィン系熱可塑性エラストマー、スチレン系熱可塑性エラストマーが好ましく、スチレン系熱可塑性エラストマーがより好ましい。 Examples of the thermoplastic elastomer include olefin-based thermoplastic elastomer, styrene-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polyester-based thermoplastic elastomer, and polyamide-based thermoplastic elastomer. With regard to the thermoplastic elastomer, these components may be used alone or in combination of two or more.
Among these, olefin-based thermoplastic elastomers and styrene-based thermoplastic elastomers are preferable, and styrene-based thermoplastic elastomers are more preferable.
　オレフィン系熱可塑性エラストマーとしては、ブレンド型、動的架橋型、重合型のものが挙げられ、より具体的には、ハードセグメントにポリプロピレンやポリエチレン等の熱可塑性結晶性ポリオレフィンを使用し、ソフトセグメントに完全加硫又は部分加硫したゴムを使用した熱可塑性エラストマーが挙げられる。
　前記熱可塑性結晶性ポリオレフィンとしては、例えば、１～４個の炭素原子を有するα－オレフィンのホモポリマー又は二種以上のα－オレフィンの共重合体が挙げられ、ポリエチレン又はポリプロピレンが好ましい。ソフトセグメント成分は、プチルゴム、ハロブチルゴム、ＥＰＤＭ、ＥＰＭ、アクリロニトリル／ブタジエンゴム、ＮＢＲ、天然ゴム等が挙げられ、これらの中ではＥＰＤＭが好ましい。 Examples of the olefin-based thermoplastic elastomer include blend type, dynamically cross-linking type, and polymerization type. More specifically, a thermoplastic crystalline polyolefin such as polypropylene or polyethylene is used for the hard segment and a soft segment is used for the soft segment. Thermoplastic elastomers using fully vulcanized or partially vulcanized rubber are mentioned.
Examples of the thermoplastic crystalline polyolefin include homopolymers of α-olefins having 1 to 4 carbon atoms or copolymers of two or more types of α-olefins, with polyethylene or polypropylene being preferred. Examples of the soft segment component include butyl rubber, halobutyl rubber, EPDM, EPM, acrylonitrile/butadiene rubber, NBR and natural rubber, and among these, EPDM is preferable.
　また、オレフィン系熱可塑性エラストマーとしては、ブロックコポリマータイプも挙げられる。ブロックコポリマータイプとしては、結晶性ブロックと、ソフトセグメントブロックとを有するものが挙げられ、より具体的には、結晶性オレフィンブロック－エチレン・ブチレン共重合体－結晶性オレフィンブロックコポリマー（ＣＥＢＣ）が例示される。ＣＥＢＣにおいて、結晶性オレフィンブロックは、結晶性エチレンブロックであることが好ましく、そのようなＣＥＢＣの市販品としては、ＪＳＲ株式会社製の「ＤＹＮＡＲＯＮ　６２００Ｐ」等が挙げられる。 Also, a block copolymer type may be mentioned as the olefinic thermoplastic elastomer. Examples of the block copolymer type include those having a crystalline block and a soft segment block, and more specifically, a crystalline olefin block-ethylene/butylene copolymer-crystalline olefin block copolymer (CEBC) is exemplified. To be done. In CEBC, the crystalline olefin block is preferably a crystalline ethylene block, and examples of commercially available products of such CEBC include "DYNARON 6200P" manufactured by JSR Corporation.
　スチレン系熱可塑性エラストマーとしては、スチレンの重合体又は共重合体ブロックと、共役ジエン化合物の重合体又は共重合体ブロックとを有するブロックコポリマーなどが挙げられる。共役ジエン化合物としては、イソプレン、ブタジエンなどが挙げられる。
　本発明に用いるスチレン系熱可塑性エラストマーは、水素添加していてもよいし、していなくてもよい。水素添加する場合、水素添加は公知の方法で行うことができる。 Examples of the styrene-based thermoplastic elastomer include a block copolymer having a polymer or copolymer block of styrene and a polymer or copolymer block of a conjugated diene compound. Examples of the conjugated diene compound include isoprene and butadiene.
The styrene-based thermoplastic elastomer used in the present invention may or may not be hydrogenated. When hydrogenating, hydrogenation can be performed by a known method.
　スチレン系熱可塑性エラストマーとしては、通常ブロック共重合体であり、スチレン－イソプレンブロック共重合体、スチレン－イソプレン－スチレンブロック共重合体、スチレン－ブタジエンブロック共重合体、スチレン－ブタジエン－スチレンブロック共重合体、スチレン－エチレン／ブチレン－スチレンブロック共重合体（ＳＥＢＳ）、スチレン－エチレン／プロピレン－スチレンブロック共重合体（ＳＥＰＳ）、スチレン－エチレン／ブチレンブロック共重合体（ＳＥＢ）、スチレン－エチレン／プロピレンブロック共重合体（ＳＥＰ）、スチレン－エチレン／ブチレン－結晶性オレフィンブロック共重合体（ＳＥＢＣ）などが挙げられる。
　上記したスチレン系熱可塑性エラストマーとしては、ブロック共重合体が好ましく、中でもＳＥＢＳ、ＳＥＢＣがより好ましい。 The styrene-based thermoplastic elastomer is usually a block copolymer, such as styrene-isoprene block copolymer, styrene-isoprene-styrene block copolymer, styrene-butadiene block copolymer, styrene-butadiene-styrene block copolymer. Coal, styrene-ethylene/butylene-styrene block copolymer (SEBS), styrene-ethylene/propylene-styrene block copolymer (SEPS), styrene-ethylene/butylene block copolymer (SEB), styrene-ethylene/propylene Examples thereof include block copolymers (SEP) and styrene-ethylene/butylene-crystalline olefin block copolymers (SEBC).
As the above-mentioned styrene-based thermoplastic elastomer, a block copolymer is preferable, and SEBS and SEBC are more preferable.
　なお、スチレン系熱可塑性エラストマーの市販品としては、株式会社ＪＳＲ製、商品名「ＤＹＮＡＲＯＮ　８６００Ｐ」（スチレン含有量１５質量％）、商品名「ＤＹＮＡＲＯＮ　４６００Ｐ」（スチレン含有量２０質量％）、商品名「ＤＹＮＡＲＯＮ　１３２１Ｐ」（スチレン含有量１０質量％）などが挙げられる。 Commercially available styrene-based thermoplastic elastomers are manufactured by JSR Co., Ltd., product name “DYNARON 8600P” (styrene content 15% by mass), product name “DYNARON 4600P” (styrene content 20% by mass), product name Examples include "DYNARON 1321P" (styrene content 10% by mass).
〔添加剤〕
　本発明において用いる第２の層は、好ましくは、上記樹脂と、発泡剤とを含む発泡性組成物を発泡することで得られる。発泡剤としては、熱分解型発泡剤が好ましい。
　熱分解型発泡剤としては、有機発泡剤、無機発泡剤が使用可能である。有機発泡剤としては、アゾジカルボンアミド、アゾジカルボン酸金属塩（アゾジカルボン酸バリウム等）、アゾビスイソブチロニトリル等のアゾ化合物、Ｎ，Ｎ’－ジニトロソペンタメチレンテトラミン等のニトロソ化合物、ヒドラゾジカルボンアミド、４，４’－オキシビス（ベンゼンスルホニルヒドラジド）、トルエンスルホニルヒドラジド等のヒドラジン誘導体、トルエンスルホニルセミカルバジド等のセミカルバジド化合物等が挙げられる。
　無機発泡剤としては、炭酸アンモニウム、炭酸ナトリウム、炭酸水素アンモニウム、炭酸水素ナトリウム、亜硝酸アンモニウム、水素化ホウ素ナトリウム、無水クエン酸モノソーダ等が挙げられる。
　これらの中では、微細な気泡を得る観点、及び経済性、安全面の観点から、アゾ化合物が好ましく、アゾジカルボンアミドがより好ましい。
　熱分解型発泡剤は１種を単独で用いてもよく、２種以上を併用してもよい。 〔Additive〕
The second layer used in the present invention is preferably obtained by foaming a foamable composition containing the above resin and a foaming agent. As the foaming agent, a thermal decomposition type foaming agent is preferable.
As the thermal decomposition type foaming agent, an organic foaming agent or an inorganic foaming agent can be used. Examples of the organic foaming agent include azodicarbonamide, metal salts of azodicarboxylic acid (barium azodicarboxylic acid), azo compounds such as azobisisobutyronitrile, nitroso compounds such as N,N'-dinitrosopentamethylenetetramine, and hydra. Examples thereof include hydrazine derivatives such as zodicarbonamide, 4,4′-oxybis(benzenesulfonylhydrazide) and toluenesulfonylhydrazide, and semicarbazide compounds such as toluenesulfonylsemicarbazide.
Examples of the inorganic foaming agent include ammonium carbonate, sodium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, anhydrous monosodium citrate and the like.
Among these, an azo compound is preferable, and an azodicarbonamide is more preferable, from the viewpoints of obtaining fine bubbles, economical efficiency, and safety.
The thermal decomposition type foaming agents may be used alone or in combination of two or more.
　発泡性樹脂組成物における発泡剤の配合量は、樹脂１００質量部に対して、１～２０質量部が好ましく、１．５～１５質量部がより好ましく、２～１０質量部が更に好ましい。発泡剤の配合量を１質量部以上にすることで、適度な柔軟性と衝撃吸収性を多層発泡体シートに付与することが可能になる。また、発泡剤の配合量を２０質量部以下にすることで、第２の層が必要以上に発泡することが防止され、第２の層の機械強度等を良好にすることができる。 The blending amount of the foaming agent in the foamable resin composition is preferably 1 to 20 parts by mass, more preferably 1.5 to 15 parts by mass, and even more preferably 2 to 10 parts by mass with respect to 100 parts by mass of the resin. By adjusting the amount of the foaming agent to be 1 part by mass or more, it becomes possible to impart appropriate flexibility and impact absorption to the multilayer foam sheet. Further, by setting the blending amount of the foaming agent to 20 parts by mass or less, it is possible to prevent the second layer from foaming more than necessary, and to improve the mechanical strength and the like of the second layer.
　発泡性樹脂組成物には、分解温度調整剤が配合されていてもよい。分解温度調整剤は、熱分解型発泡剤の分解温度を低くしたり、分解速度を速めたり調節するものとして配合されるものであり、具体的な化合物としては、酸化亜鉛、ステアリン酸亜鉛、尿素等が挙げられる。分解温度調整剤は、第２の層の表面状態等を調整するために、例えば樹脂１００質量部に対して０．０１～５質量部配合される。 A decomposition temperature adjusting agent may be added to the foamable resin composition. The decomposition temperature adjusting agent is added to lower the decomposition temperature of the thermal decomposition type foaming agent or to accelerate or control the decomposition rate, and specific compounds include zinc oxide, zinc stearate and urea. Etc. The decomposition temperature adjusting agent is mixed, for example, in an amount of 0.01 to 5 parts by mass with respect to 100 parts by mass of the resin in order to adjust the surface condition of the second layer and the like.
　発泡性樹脂組成物には、酸化防止剤が配合されていてもよい。酸化防止剤としては、２，６－ジ－ｔ－ブチル－ｐ－クレゾール等のフェノール系酸化防止剤、イオウ系酸化防止剤、リン系酸化防止剤、アミン系酸化防止剤等が挙げられる。酸化防止剤は、例えば樹脂１００質量部に対して０．０１～５質量部配合される。 An antioxidant may be added to the foamable resin composition. Examples of the antioxidant include phenolic antioxidants such as 2,6-di-t-butyl-p-cresol, sulfur antioxidants, phosphorus antioxidants, amine antioxidants and the like. The antioxidant is mixed, for example, in an amount of 0.01 to 5 parts by mass with respect to 100 parts by mass of the resin.
　第２の層において、樹脂は主成分となるものであり、樹脂の含有量は、第２の層全量基準で、例えば７０質量％以上、好ましくは８０質量％以上、より好ましくは９０質量％以上である。
　発泡性樹脂組成物は、必要に応じて、上記以外にも、熱安定剤、着色剤、難燃剤、帯電防止剤、充填材等の発泡体に一般的に使用する添加剤を含有していてもよい。 In the second layer, the resin is the main component, and the content of the resin is, for example, 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, based on the total amount of the second layer. Is.
The foamable resin composition, if necessary, contains additives generally used in foams such as heat stabilizers, colorants, flame retardants, antistatic agents, and fillers in addition to the above. Good.
〔第２の層の発泡倍率〕
　第２の層の発泡倍率は、特に制限されないが、１．１～２０ｃｍ３／ｇであることが好ましい。発泡倍率を１．１ｃｍ３／ｇ以上とすることで、多層発泡体シートの柔軟性が高まり、発泡倍率を２０ｃｍ３／ｇ以下とすることで。多層発泡体シートの強度が向上する。第２の層の発泡倍率は、２．５～１８ｃｍ３／ｇであることがより好ましく、７．５～１６ｃｍ３／ｇであることが更に好ましい。第２の層の発泡倍率は、第２の層の見かけ密度の逆数で表される。 [Expansion Ratio of Second Layer]
The expansion ratio of the second layer is not particularly limited, but is preferably 1.1 to 20 cm 3 /g. By setting the expansion ratio to 1.1 cm 3 /g or more, the flexibility of the multilayer foam sheet is increased, and the expansion ratio is set to 20 cm 3 /g or less. The strength of the multilayer foam sheet is improved. The expansion ratio of the second layer is more preferably 2.5 to 18 cm 3 /g, and further preferably 7.5 to 16 cm 3 /g. The expansion ratio of the second layer is represented by the reciprocal of the apparent density of the second layer.
〔第２の層の架橋度〕
　第２の層の架橋度は、特に限定されないが、例えば５～６５％、好ましくは１０～５５％、より好ましくは２０～５０％である。第２の層の架橋度をこれら下限値以上とすることにより、柔軟性が必要以上に高まることを抑制し、一定の機械強度を確保できる。また、上記上限値以下とすることで、柔軟性及び衝撃吸収性が良好となる。 [Crosslinking degree of second layer]
The degree of crosslinking of the second layer is not particularly limited, but is, for example, 5 to 65%, preferably 10 to 55%, more preferably 20 to 50%. By setting the degree of crosslinking of the second layer to the lower limit value or more, it is possible to prevent the flexibility from increasing more than necessary and to secure a certain mechanical strength. Moreover, when the content is not more than the above upper limit, the flexibility and the impact absorption are improved.
＜第１及び第３の層＞
　第１の層及び第３の層は、それぞれ上記したとおり樹脂フィルム、又は発泡体であり、好ましくは樹脂フィルムである。樹脂フィルムは、非発泡体の樹脂層である。以下、第１の層及び第３の層がいずれも樹脂フィルムである場合についてより詳細に説明する。 <First and third layers>
The first layer and the third layer are resin films or foams, respectively, as described above, and preferably resin films. The resin film is a non-foamed resin layer. Hereinafter, the case where both the first layer and the third layer are resin films will be described in more detail.
　第１の層及び第３の層それぞれにおいて、樹脂フィルムを構成する樹脂の種類は、上記式（１）、（２）の関係を満たすものであれば特に限定されないが、上記第２の層の樹脂と同様に、ポリオレフィン系樹脂、アクリル系樹脂、ポリウレタン系樹脂、及び熱可塑性エラストマー等が挙げられる。また、これら以外にも、塩ビ系樹脂、スチレン系樹脂、ポリエステル系樹脂、ポリアミド系樹脂、アイオノマー系樹脂などを使用してもよい。
　第１の層及び第３の層それぞれにおいて、樹脂は、１種単独で使用してもよいし、２種以上併用してもよい。また、第１の層に使用する樹脂と、第３の層に使用する樹脂は、互いに同種の樹脂であってもよいし、異なる樹脂であってもよいが、生産性の観点、及び両層の物性を同じ又は類似にしやすい観点から、互いに同種であることが好ましい。 In each of the first layer and the third layer, the kind of the resin constituting the resin film is not particularly limited as long as it satisfies the relations of the above formulas (1) and (2). Examples of the resin include polyolefin resin, acrylic resin, polyurethane resin, and thermoplastic elastomer. In addition to these, vinyl chloride resin, styrene resin, polyester resin, polyamide resin, ionomer resin, etc. may be used.
In each of the first layer and the third layer, the resin may be used alone or in combination of two or more. The resin used for the first layer and the resin used for the third layer may be the same kind of resin or different resins, but from the viewpoint of productivity and both layers. From the viewpoint of easily making the physical properties of the same or similar, it is preferable that they are the same kind.
　第１の層及び第３の層それぞれを構成する樹脂は、熱可塑性樹脂が好ましく、熱可塑性樹脂を使用することで、第１の層及び第３の層を、容易に第２の層に接着させることが可能になる。
　また、第１の層及び第３の層それぞれに使用する樹脂としては、上記したなかでは、ポリオレフィン系樹脂が好ましい。ポリオレフィン系樹脂を使用することで、曲げ応力を低くしつつ、多層発泡体シートの機械強度を高くしやすくなる。また、第２の層に、ポリオレフィン樹脂や、熱可塑性エラストマーを使用した場合に、第１及び第３の層の第２の層に対する接着性を特に良好にできる。 The resin constituting each of the first layer and the third layer is preferably a thermoplastic resin, and by using the thermoplastic resin, the first layer and the third layer are easily bonded to the second layer. It is possible to
In addition, as the resin used for each of the first layer and the third layer, a polyolefin resin is preferable among the above. By using the polyolefin-based resin, it becomes easy to increase the mechanical strength of the multilayer foam sheet while reducing the bending stress. Further, when a polyolefin resin or a thermoplastic elastomer is used for the second layer, the adhesion of the first and third layers to the second layer can be made particularly good.
　ポリオレフィン系樹脂としては、ポリエチレン樹脂、ポリプロピレン樹脂等が挙げられる。また、エチレン－酢酸ビニル共重合体、エチレン－エチルアクリレート共重合体等でもよい。
　ポリエチレン樹脂としては、チーグラー・ナッタ化合物、メタロセン触媒、酸化クロム化合物等の重合触媒で重合されたポリエチレン樹脂が挙げられ、好ましくは、メタロセン触媒で重合されたポリエチレン樹脂が用いられる。
　また、ポリエチレン樹脂としては、例えば、低密度ポリエチレン（密度：０．９３０ｇ／ｃｍ３未満）、中密度ポリエチレン（密度：０．９３０ｇ／ｃｍ３以上０．９４２ｇ／ｃｍ３未満）、高密度ポリエチレン（密度：０．９４２ｇ／ｃｍ３以上）が挙げられる。
　ここで、低密度ポリエチレンとしては、例えば直鎖状低密度ポリエチレンが挙げられる。直鎖状低密度ポリエチレンの詳細は、第２の層の説明において述べた通りであるので、その詳細は省略する。また、ポリプロピレン樹脂の詳細も、第２の層の説明において述べた通りであるので、その詳細は省略する。 Examples of the polyolefin resin include polyethylene resin and polypropylene resin. Further, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer and the like may be used.
Examples of the polyethylene resin include polyethylene resins polymerized with a polymerization catalyst such as a Ziegler-Natta compound, a metallocene catalyst and a chromium oxide compound, and preferably a polyethylene resin polymerized with a metallocene catalyst is used.
Examples of the polyethylene resin include low-density polyethylene (density: less than 0.930 g/cm 3 ), medium-density polyethylene (density: 0.930 g/cm 3 or more and less than 0.942 g/cm 3 ), high-density polyethylene ( Density: 0.942 g/cm 3 or more).
Here, examples of the low-density polyethylene include linear low-density polyethylene. Since the details of the linear low-density polyethylene are as described in the description of the second layer, the details are omitted. Further, since the details of the polypropylene resin are as described in the description of the second layer, the details thereof will be omitted.
　第１及び第３の層にて使用するエチレン－酢酸ビニル共重合体は、例えば、エチレン由来の構成単位を５０質量％以上含有するエチレン－酢酸ビニル共重合体が挙げられる。
　また、エチレン－エチルアクリレート共重合体は、エチレン由来の構成単位を５０質量％以上含有するエチレン－エチルアクリレート共重合体が挙げられる。
　上記したなかでは、第２の層との接着性、曲げ応力、及び引張強度の観点から、エチレン樹脂、特に、直鎖状低密度ポリエチレンが好ましい。また、同様の観点から、エチレン－酢酸ビニル共重合体も好ましい。 The ethylene-vinyl acetate copolymer used in the first and third layers includes, for example, an ethylene-vinyl acetate copolymer containing 50% by mass or more of a constitutional unit derived from ethylene.
Further, the ethylene-ethyl acrylate copolymer includes an ethylene-ethyl acrylate copolymer containing 50% by mass or more of constituent units derived from ethylene.
Among the above, from the viewpoint of adhesiveness with the second layer, bending stress, and tensile strength, ethylene resin, particularly linear low-density polyethylene is preferable. From the same viewpoint, ethylene-vinyl acetate copolymer is also preferable.
　第１及び第３の層において、樹脂は主成分となるものであり、樹脂の含有量は、各層全量基準で、例えば７０質量％以上、好ましくは８０質量％以上、より好ましくは９０質量％以上である。第１の層及び第３の層には、上記樹脂以外にも、酸化防止剤、熱安定剤、着色剤、難燃剤、帯電防止剤、充填材等の添加剤を含有してもよい。
　第１及び第３の層は、架橋されていてもよい。第１及び第３の層は、後述する製造方法１で述べるように、第２の層が架橋されるのに合わせて架橋されるとよく、したがって、電離性放射線により架橋されることが好ましい。 In the first and third layers, the resin is the main component, and the resin content is, for example, 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, based on the total amount of each layer. Is. The first layer and the third layer may contain additives such as an antioxidant, a heat stabilizer, a colorant, a flame retardant, an antistatic agent and a filler, in addition to the above resins.
The first and third layers may be crosslinked. The first and third layers may be cross-linked at the same time as the second layer is cross-linked, as described in the production method 1 described later, and thus are preferably cross-linked by ionizing radiation.
　第１の層及び第３の層それぞれは、上記したように発泡体であってもよい。第１の層、及び第３の層を発泡体とする場合には、例えば、上記した第１及び第３の層において使用できる樹脂に、第２の層で説明したように発泡剤などを配合して、第１及び第３の層を発泡させればよい。第１の層及び第３の層は、発泡体である場合には、一定の機械強度を確保する観点から、発泡倍率が低い方がよく、各層に含まれる気泡の割合を示す気泡率は低くなる。
　具体的には、第１の層及び第３の層はいずれも、気泡率が６６％以下であることが好ましく、より好ましくは３３％以下、さらに好ましくは０％である。なお第１及び第２の層が非発泡体（すなわち、樹脂フィルム）である場合には、気泡率は０％となる。
　なお、気泡率は、例えば、第１の層及び第３の層を断面観察して、各層の面積に対する気泡が占める面積の割合を算出することで求めることができる。具体的には、厚み方向に沿って断面を切り出し、光学顕微鏡で断面撮影を行う。その後、気泡、樹脂部分を二値化にて区分を行い、気泡部面積／総面積にて算出するとよい。 Each of the first and third layers may be foam, as described above. When the first layer and the third layer are foamed, for example, the resin that can be used in the first and third layers is mixed with a foaming agent or the like as described in the second layer. Then, the first and third layers may be foamed. When the first layer and the third layer are foams, it is preferable that the expansion ratio is low and the bubble ratio indicating the ratio of bubbles contained in each layer is low from the viewpoint of ensuring a certain mechanical strength. Become.
Specifically, the bubble ratio of each of the first layer and the third layer is preferably 66% or less, more preferably 33% or less, and further preferably 0%. When the first and second layers are a non-foamed body (that is, a resin film), the bubble ratio is 0%.
The bubble ratio can be obtained, for example, by observing the cross section of the first layer and the third layer and calculating the ratio of the area occupied by the bubbles to the area of each layer. Specifically, a cross section is cut out along the thickness direction, and the cross section is photographed with an optical microscope. After that, the air bubbles and the resin portion may be binarized to be divided, and the area of the air bubbles/total area may be calculated.
（接着層）
　本発明では、上記したように、第１の層と第２の層、又は第２の層と第３の層は、直接接着されてもよいが、他の層（すなわち、接着層）を介して接着されてもよい。接着層としては、公知の接着剤、粘着剤などが使用されるとよい。また、基材の両面に粘着剤層が設けられた両面粘着テープなどであってもよい。
　なお、接着層は、多層発泡体シートにおいて、機械強度、柔軟性などの物性に対して、大きく影響を与えない程度の厚さを有すればよい。したがって、第１の層と第２の層を接着する接着層の厚みは、第１の層よりも薄いことが好ましく、第１の層の１／２以下の厚みであることがより好ましい。同様に、第２の層と第３の層を接着する接着層の厚みは、第３の層よりも薄いことが好ましく、第３の層の１／２以下の厚みであることがより好ましい。 (Adhesive layer)
In the present invention, as described above, the first layer and the second layer, or the second layer and the third layer may be directly adhered, but another layer (that is, an adhesive layer) is used. May be bonded together. As the adhesive layer, a known adhesive or pressure-sensitive adhesive may be used. Further, it may be a double-sided pressure-sensitive adhesive tape in which a pressure-sensitive adhesive layer is provided on both sides of the base material.
The adhesive layer may have a thickness that does not significantly affect physical properties such as mechanical strength and flexibility in the multilayer foam sheet. Therefore, the thickness of the adhesive layer for bonding the first layer and the second layer is preferably thinner than that of the first layer, and more preferably 1/2 or less of the thickness of the first layer. Similarly, the thickness of the adhesive layer that bonds the second layer and the third layer is preferably thinner than that of the third layer, and more preferably 1/2 or less of the thickness of the third layer.
＜多層発泡体シートの製造方法＞
（製造方法１）
　本発明の多層発泡体シートは、特に限定されないが、例えば、樹脂組成物からなる層を複数積層して、多層積層体シートを得て、その後、多層積層体シートを発泡することにより得る方法（以下、「製造方法１」ともいう）により製造できる。なお、本明細書において「樹脂組成物」という用語は、１種の樹脂単独からなる場合も概念として含むものである。 <Method for producing multilayer foam sheet>
(Manufacturing method 1)
The multilayer foam sheet of the present invention is not particularly limited, but for example, a method of obtaining a multilayer laminate sheet by laminating a plurality of layers made of a resin composition, and then foaming the multilayer laminate sheet ( Hereinafter, it can be manufactured by "manufacturing method 1"). In addition, in this specification, the term "resin composition" also includes a case where it is composed of one type of resin alone.
　製造方法１は、より具体的には、以下の工程Ｉ～ＩＩを含む。
（Ｉ）発泡性樹脂組成物からなる層と、該層の一方の面に形成された第１の層と、該層の他方の面に形成された第３の層とを備えた多層積層体シートを得る工程
（ＩＩ）多層積層体シートの発泡性樹脂組成物からなる層を発泡させることにより、多層発泡体シートを得る工程 More specifically, the manufacturing method 1 includes the following steps I to II.
(I) Multilayer laminate comprising a layer made of a foamable resin composition, a first layer formed on one surface of the layer, and a third layer formed on the other surface of the layer Step of obtaining a sheet (II) Step of obtaining a multilayer foam sheet by foaming a layer of the expandable resin composition of the multilayer laminate sheet
　以下、各工程について説明する。
（工程（Ｉ））
　工程（Ｉ）において多層積層体シートを得る方法としては、特に限定されないが、共押出成形により行うことが好ましい。具体的には、第１の層、及び第３の層を形成するための樹脂、その他必要に応じて配合される添加剤を第１及び第３の押出機にそれぞれ供給して溶融混練して、第１及び第３の層を形成するための樹脂組成物を得る。また、第２の層を形成するための樹脂、熱分解型発泡剤などの発泡剤、及び必要に応じて配合される添加剤を第２の押出機に供給して溶融混練して、第２の層を形成するための発泡性樹脂組成物を得る。
　次いで、第１～第３の押出機から供給された樹脂組成物を、第２の押出機から供給された組成物が中層になるように合流させて、Ｔダイ等によりシート状に押出すことにより、３層構造の多層積層体シートを得ることができる。共押出成形においては、フィードブロック法、マルチマニホールド法のいずれでもよいが、フィードブロック法が好ましい。 Hereinafter, each step will be described.
(Process (I))
The method for obtaining the multilayer laminate sheet in step (I) is not particularly limited, but coextrusion molding is preferable. Specifically, a resin for forming the first layer and the third layer, and other additives to be blended as necessary are supplied to the first and third extruders respectively and melt-kneaded. , To obtain a resin composition for forming the first and third layers. Further, a resin for forming the second layer, a foaming agent such as a thermal decomposition type foaming agent, and an additive to be blended as necessary are supplied to the second extruder and melt-kneaded, A foamable resin composition for forming the layer is obtained.
Next, the resin compositions supplied from the first to third extruders are merged so that the composition supplied from the second extruder becomes an intermediate layer, and the mixture is extruded into a sheet by a T-die or the like. Thereby, a multilayer laminate sheet having a three-layer structure can be obtained. In the coextrusion molding, either the feed block method or the multi-manifold method may be used, but the feed block method is preferable.
　工程（Ｉ）では、上記で得られた多層積層体シートをさらに架橋することが好ましい。架橋方法としては、予め有機過酸化物を配合しておき、工程（Ｉ）で得られた多層積層体シートを加熱して架橋する方法もあるが、多層積層体シートに電離性放射線を照射して架橋させることが好ましい。なお、電離性放射線としては、電子線、β線等が挙げられるが、電子線であることが好ましい。
　電離性放射線の照射量は、１～１０Ｍｒａｄが好ましく、１．５～５Ｍｒａｄがより好ましい。 In the step (I), it is preferable to further crosslink the multilayer laminate sheet obtained above. As a cross-linking method, there is also a method of previously blending an organic peroxide and heating the multi-layer laminate sheet obtained in the step (I) to cross-link, but the multi-layer laminate sheet is irradiated with ionizing radiation. It is preferable to crosslink. Examples of the ionizing radiation include electron beams and β rays, but electron beams are preferable.
The dose of ionizing radiation is preferably 1 to 10 Mrad, more preferably 1.5 to 5 Mrad.
（工程（ＩＩ））
　工程（ＩＩ）では、工程（Ｉ）で得られた多層積層体シートを発泡処理して、発泡性樹脂組成物からなる層を発泡させる。発泡性樹脂組成物からなる層は、発泡剤が発泡するように処理すればよいが、発泡剤が熱分解型発泡剤である場合には、多層積層体シートを加熱することで発泡する。加熱温度は、熱分解型発泡剤が分解する温度以上であればよいが、例えば、１５０～３２０℃程度である。
　多層積層体シートを加熱する方法は、特に制限はなく、例えば、多層積層体シートを熱風により加熱する方法、赤外線により加熱する方法、塩浴により加熱する方法、オイルバスにより加熱する方法等が挙げられ、これらは併用してもよい。
　また、多層積層体シートは、発泡させながら、または発泡させた後に適宜延伸などしてもよい。
　なお、以上の説明は、第１及び第３の層が、樹脂フィルム（非発泡体）である場合の例を説明したが、第１及び第３の層が発泡体である場合には、第１及び第３の層を形成するための樹脂組成物にも添加剤として熱分解型発泡剤などの発泡剤を配合しておき、工程（ＩＩ）にて発泡させるとよい。 (Process (II))
In the step (II), the multilayer laminate sheet obtained in the step (I) is subjected to a foaming treatment to foam a layer made of the foamable resin composition. The layer made of the foamable resin composition may be treated so that the foaming agent foams. When the foaming agent is a pyrolytic foaming agent, the multilayer laminate sheet is heated to foam. The heating temperature may be equal to or higher than the temperature at which the pyrolytic foaming agent decomposes, and is, for example, about 150 to 320°C.
The method for heating the multilayer laminate sheet is not particularly limited, and examples thereof include a method of heating the multilayer laminate sheet with hot air, a method of heating with infrared rays, a method of heating with a salt bath, and a method of heating with an oil bath. However, these may be used in combination.
Further, the multilayer laminate sheet may be appropriately stretched while foaming or after foaming.
In the above description, an example in which the first and third layers are resin films (non-foamed bodies) has been described, but when the first and third layers are foamed, A foaming agent such as a pyrolyzable foaming agent may be added as an additive to the resin composition for forming the first and third layers, and foamed in step (II).
（第２の製造方法）
　本発明の多層発泡体シートの製造方法は、別の方法でも製造することができる。具体的には、第２の層を構成する発泡体を予め製造し、その発泡体（第２の層）の両面に、樹脂フィルム又は発泡体（第１及び第３の層）を重ね合わせて、接着させる方法（「第２の製造方法」ともいう）が挙げられる。 (Second manufacturing method)
The method for producing the multilayer foam sheet of the present invention can also be produced by another method. Specifically, a foam forming the second layer is manufactured in advance, and a resin film or a foam (first and third layers) is superposed on both surfaces of the foam (second layer). , And a method of bonding (also referred to as “second manufacturing method”).
　第２の製造方法において発泡体を得る方法としては、第２の層を形成するための樹脂、熱分解型発泡剤、及び必要に応じて配合される添加剤を溶融混練して、第２の層を形成するための発泡性樹脂組成物を得て、その発泡性樹脂組成物をシート状（発泡性樹脂組成物シート）に成形するとよい。発泡性樹脂組成物を溶融混錬して、シート状に成形する方法は特に限定されないが、押出機を用いて行うことが好ましい。 As a method for obtaining a foam in the second manufacturing method, a resin for forming the second layer, a pyrolytic foaming agent, and an additive to be blended as necessary are melt-kneaded to obtain a second layer. It is advisable to obtain a foamable resin composition for forming a layer and form the foamable resin composition into a sheet shape (foamable resin composition sheet). The method of melting and kneading the foamable resin composition to form a sheet is not particularly limited, but it is preferable to use an extruder.
　得られた発泡性樹脂組成物シートは、後述する発泡前にさらに架橋することが好ましい。架橋方法としては、予め有機過酸化物を配合しておき、発泡性樹脂組成物シートを加熱して架橋する方法もあるが、発泡性樹脂組成物シートに電離性放射線を照射して架橋させることが好ましい。なお、電離性放射線の種類、照射量は、上記した第１の製造方法で記載したとおりである。 The obtained foamable resin composition sheet is preferably further cross-linked before foaming described later. As a cross-linking method, there is also a method of pre-blending an organic peroxide and heating the foamable resin composition sheet to cross-link it, but the cross-linking is performed by irradiating the foamable resin composition sheet with ionizing radiation. Is preferred. The type of ionizing radiation and the irradiation amount are as described in the above-mentioned first manufacturing method.
　次に、発泡性樹脂組成物シートは発泡させるとよい。発泡性樹脂組成物からなる層は、発泡剤が発泡するように処理すればよいが、発泡剤が熱分解型発泡剤である場合には、多層積層体シートを加熱することで発泡する。加熱温度、加熱方法は、上記した第１の製造方法で記載したとおりである。また、発泡性樹脂組成物シートは、発泡させながら、または発泡させた後に適宜延伸などしてもよい。 Next, the foamable resin composition sheet may be foamed. The layer made of the foamable resin composition may be treated so that the foaming agent foams. When the foaming agent is a pyrolytic foaming agent, the multilayer laminate sheet is heated to foam. The heating temperature and the heating method are as described in the first manufacturing method described above. Further, the foamable resin composition sheet may be appropriately stretched while foaming or after foaming.
　その後、別途準備した第１の層及び第３の層を構成するための樹脂フィルム、又は発泡体を第２の層を構成するための発泡体に重ね合わせ、接着することで、多層発泡体シートを得ることができる。具体的にはプレス機等により加熱及び加圧して、熱圧着してもよい。あるいは、第２の層と第１の層の間の接着面、及び第２の層と第３の層の間の接着面に、粘着剤、接着剤等を塗布し、または両面粘着テープを貼着して、粘着剤、接着剤、両面粘着テープ等により貼り合わせてもよい。 After that, a resin film for forming the first layer and the third layer, or a foam, which is separately prepared, is placed on the foam for forming the second layer, and the foam is adhered to the multilayer foam sheet. Can be obtained. Specifically, it may be heated and pressed by a press machine or the like to perform thermocompression bonding. Alternatively, an adhesive, an adhesive, or the like is applied to the adhesive surface between the second layer and the first layer and the adhesive surface between the second layer and the third layer, or a double-sided adhesive tape is attached. You may put on and stick together with an adhesive, an adhesive, a double-sided adhesive tape, etc.
＜多層発泡体シートの用途＞
　本発明の多層発泡体シートは、特に限定されないが、例えば、電子機器内部で使用することが好ましく、例えば、２つの部材の間に配置して、衝撃吸収材、シール材などとして使用することができる。また、多層発泡体シートを額縁状にして、携帯電子機器内部に使用することもできる。
　携帯電子機器としては、携帯電話、カメラ、ゲーム機器、電子手帳、パーソナルコンピューター等が挙げられる。また、本発明の多層発泡体シートを後述する粘着テープにして、電子機器内部において使用してもよい。 <Use of multilayer foam sheet>
The multilayer foam sheet of the present invention is not particularly limited, but is preferably used, for example, inside an electronic device. For example, it is placed between two members and used as a shock absorber, a sealant, or the like. it can. Further, the multilayer foam sheet can be formed into a frame shape and used in a portable electronic device.
Examples of the mobile electronic device include a mobile phone, a camera, a game device, an electronic notebook, and a personal computer. Further, the multilayer foam sheet of the present invention may be used as an adhesive tape described later and used inside an electronic device.
　本発明の多層発泡体シートは、紙芯などの巻芯に巻き取られてロール状にされてもよい。多層発泡体シートは、ロール状にされることで保管、運搬などをしやすくなる。巻芯としては、上記の通り、半径が３～６インチ（７６．２～１５２．４ｍｍ）程度の巻芯を使用すればよい。巻芯に巻き取られる際、多層発泡体シートは、上記したように曲げ応力が所定値以下である層が巻芯側（内側）となるように巻き取られるとよい。したがって、第３の層が巻芯側となるように巻き取られればよいが、上記のように、第１及び第３の層のいずれの曲げ応力も所定値以下となる場合には、第１の層が巻芯側（内側）となるように巻き取られてもよい。 The multilayer foam sheet of the present invention may be wound into a roll such as a paper core. When the multilayer foam sheet is rolled, it can be easily stored and transported. As described above, a core having a radius of about 3 to 6 inches (76.2 to 152.4 mm) may be used as the core. When wound on the core, the multilayer foam sheet may be wound so that the layer having a bending stress of not more than a predetermined value is on the core side (inside) as described above. Therefore, it suffices if the third layer is wound so as to be on the winding core side. However, as described above, when the bending stress of both the first and third layers is less than or equal to a predetermined value, The layer may be wound so that the layer is on the winding core side (inside).
［粘着テープ］
　本発明の多層発泡体シートは、多層発泡体シートを基材とする粘着テープに使用してもよい。粘着テープは、例えば、多層発泡体シートと、多層発泡体シートの少なくとも一方の面に設けた粘着材とを備えるものである。粘着テープは、粘着材を介して他の部材に接着することが可能になる。粘着テープは、多層発泡体シートの両面に粘着材を設けたものでもよいし、片面に粘着材を設けたものでもよい。 [Adhesive tape]
The multilayer foam sheet of the present invention may be used for an adhesive tape having the multilayer foam sheet as a base material. The adhesive tape comprises, for example, a multilayer foam sheet and an adhesive material provided on at least one surface of the multilayer foam sheet. The adhesive tape can be adhered to another member via the adhesive material. The adhesive tape may be a multi-layer foam sheet provided with an adhesive material on both sides, or may be provided with an adhesive material on one side.
　また、粘着材は、少なくとも粘着剤層を備えるものであればよく、多層発泡体シートの表面（すなわち、第１又は第３の層１１、１３の表面１１Ａ，１３Ａ，図１、２参照）に積層された粘着剤層単体であってもよいし、多層発泡体シートの表面に貼付された両面粘着シートであってもよいが、粘着剤層単体であることが好ましい。なお、両面粘着シートは、基材と、基材の両面に設けられた粘着剤層とを備えるものである。両面粘着シートは、一方の粘着剤層を多層発泡体シートに接着させるとともに、他方の粘着剤層を他の部材に接着させるために使用する。
　粘着剤層を構成する粘着剤としては、特に制限はなく、例えば、アクリル系粘着剤、ウレタン系粘着剤、ゴム系粘着剤等を用いることができる。また、粘着材の上には、さらに離型紙等の剥離シートが貼り合わされてもよい。
　粘着材の厚さは、５～２００μｍであることが好ましく、より好ましくは７～１５０μｍであり、更に好ましくは１０～１００μｍである。 Further, the pressure-sensitive adhesive may be at least one having a pressure-sensitive adhesive layer, and may be provided on the surface of the multilayer foam sheet (that is, the surfaces 11A and 13A of the first or third layers 11 and 13; see FIGS. 1 and 2). It may be a laminated pressure-sensitive adhesive layer alone or a double-sided pressure-sensitive adhesive sheet attached to the surface of the multilayer foam sheet, but it is preferably a pressure-sensitive adhesive layer alone. The double-sided pressure-sensitive adhesive sheet includes a base material and a pressure-sensitive adhesive layer provided on both surfaces of the base material. The double-sided pressure-sensitive adhesive sheet is used to bond one pressure-sensitive adhesive layer to the multilayer foam sheet and the other pressure-sensitive adhesive layer to another member.
The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, and for example, an acrylic pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, a rubber pressure-sensitive adhesive, or the like can be used. Further, a release sheet such as release paper may be further attached on the adhesive material.
The thickness of the adhesive material is preferably 5 to 200 μm, more preferably 7 to 150 μm, and further preferably 10 to 100 μm.
　本発明の粘着テープは、巻芯に巻き取られてロール状とされてもよい。巻芯の半径は、上記のとおりである。このように多層発泡体シートは、粘着テープの状態にされて巻き取られる場合も、上記のように粘着材の厚みは薄いので、概ね巻芯の大きさに応じた曲率半径で曲げられるが、第３の層、又は第１及び第３の層の曲げ応力が上記した所定の範囲以下となることで、折りジワの発生を防止できる。 The pressure-sensitive adhesive tape of the present invention may be wound around a winding core to form a roll. The radius of the winding core is as described above. In this way, the multilayer foam sheet is bent in a radius of curvature generally according to the size of the winding core because the thickness of the adhesive material is thin as described above even when wound in a state of an adhesive tape. When the bending stress of the third layer or the first and third layers is within the above-mentioned predetermined range, it is possible to prevent the occurrence of folding wrinkles.
　本発明を実施例により更に詳細に説明するが、本発明はこれらの例によってなんら限定されるものではない。 The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
［測定方法］
　各物性の測定方法及び評価方法は、次の通りである。 [Measuring method]
The methods for measuring and evaluating each physical property are as follows.
＜第１の層及び第３の層の引張弾性率＞
　第１の層及び第３の層の引張弾性率を引張試験機（ヤマト科学（株）社製、テンシロンＲＴＦシリーズ）を用いて測定した。測定条件は、ＪＩＳ　Ｋ６７６７に準拠して行った。 <Tensile Elastic Modulus of First Layer and Third Layer>
The tensile elastic moduli of the first layer and the third layer were measured using a tensile tester (Yamato Scientific Co., Ltd., Tensilon RTF series). The measurement conditions were based on JIS K6767.
＜第１の層及び第３の層の引張強度＞
　第１の層及び第３の層をＪＩＳ　Ｋ６２５１　４．１に規定されるダンベル状１号形にカットした。これを試料として用い、引張試験機（製品名．テンシロンＲＴＦ２３５、エー・アンド・デイ社製）により、測定温度２３℃で、ＪＩＳＫ６７６７に準拠して、引張強度を測定した。
＜２５％圧縮強度＞
　多層発泡体シートの２５％圧縮強度はＪＩＳ　Ｋ６７６７に準拠して測定した。 <Tensile Strength of First Layer and Third Layer>
The first layer and the third layer were cut into dumbbell-shaped No. 1 type specified in JIS K6251 4.1. Using this as a sample, the tensile strength was measured by a tensile tester (product name: Tensilon RTF235, manufactured by A&D Company) at a measurement temperature of 23° C. according to JISK6767.
<25% compressive strength>
The 25% compressive strength of the multilayer foam sheet was measured according to JIS K6767.
＜見かけ密度及び発泡倍率＞
　発泡体についてＪＩＳ　Ｋ７２２２に準拠して見かけ密度を測定し、その逆数を発泡倍率とした。
＜架橋度＞
　発泡体から約１００ｍｇの試験片を採取し、試験片の重量Ａ（ｍｇ）を精秤する。次に、この試験片を１２０℃のキシレン３０ｃｍ３中に浸漬して２４時間放置した後、２００メッシュの金網で濾過して金網上の不溶解分を採取、真空乾燥し、不溶解分の重量Ｂ（ｍｇ）を精秤する。得られた値から、下記式により架橋度（質量％）を算出した。
　　　　　　架橋度（質量％）＝１００×（Ｂ／Ａ） <Apparent density and expansion ratio>
The apparent density of the foam was measured according to JIS K7222, and the reciprocal thereof was taken as the expansion ratio.
<Crosslinking degree>
A test piece of about 100 mg is taken from the foam, and the weight A (mg) of the test piece is precisely weighed. Next, this test piece was dipped in 30 cm 3 of xylene at 120° C. and left for 24 hours, then filtered through a 200-mesh wire net to collect the insoluble matter on the wire mesh, and vacuum dried to obtain the weight of the insoluble matter. Exactly weigh B (mg). The degree of crosslinking (mass %) was calculated from the obtained value by the following formula.
Crosslinking degree (mass %)=100×(B/A)
＜評価（折れジワ）＞
　Ａ４サイズに作製したサンプルを所定の紙芯に短辺を固定する。固定後、５Ｎの力で紙芯に巻き付けを実施する。実施後、３０秒静止し、その後、紙芯が取り外し、巻き付け内側のサンプル状況を観察し、折れジワの発生有無を判断する。判断基準は、折れの深さが、0.05mm以上を折れジワと判定する。折れジワがない場合を「Ａ」とし、折れジワがあった場合を「Ｂ」とした。 <Evaluation (breakage)>
The short side is fixed to a predetermined paper core of the sample prepared in A4 size. After fixing, the paper core is wrapped with a force of 5N. After the operation, the paper core is removed for 30 seconds, then the paper core is removed, and the sample state inside the winding is observed to determine whether or not a crease is formed. The judgment criteria is that a crease with a depth of 0.05 mm or more is a crease. The case where there were no creases was designated as "A", and the case where there were creases was designated as "B".
［実施例１］
　第２の層用のポリオレフィン樹脂としてメタロセン触媒によって得られた直鎖状低密度ポリエチレン樹脂（日本ポリエチレン株式会社製、商品名「カーネルＫＦ２８３」、密度：０．９２１ｇ／ｃｍ３）（メタロセンＬＬＤＰＥ）、熱分解型発泡剤としてアゾジカルボンアミドを用意した。また、分解温度調整剤として酸化亜鉛（堺化学工業株式会社製、商品名「ＯＷ－２１２Ｆ」）、酸化防止剤としてフェノール系酸化防止剤である２，６－ジ－ｔ－ブチル－ｐ－クレゾールを用意した。ポリエチレン樹脂１００質量部、熱分解型発泡剤８．０質量部、分解温度調整剤１質量部、及び酸化防止剤０．５質量部をそれぞれ第２の押出機に供給して１３０℃で溶融混練して、発泡性樹脂組成物を作製した。 [Example 1]
Linear low density polyethylene resin obtained by metallocene catalysis as the polyolefin resin for the second layer (Nippon Polyethylene Co., Ltd., trade name "Kernel KF283", density: 0.921g / cm 3) (metallocene LLDPE), Azodicarbonamide was prepared as a thermal decomposition type foaming agent. Further, zinc oxide (trade name “OW-212F” manufactured by Sakai Chemical Industry Co., Ltd.) is used as a decomposition temperature adjusting agent, and 2,6-di-t-butyl-p-cresol, which is a phenolic antioxidant as an antioxidant. Prepared. 100 parts by mass of a polyethylene resin, 8.0 parts by mass of a thermal decomposition type foaming agent, 1 part by mass of a decomposition temperature adjusting agent, and 0.5 parts by mass of an antioxidant are respectively supplied to a second extruder and melt-kneaded at 130°C. Then, a foamable resin composition was produced.
　次いで、第１の層用及び第３の層用のポリエチレン樹脂として直鎖状低密度ポリエチレン樹脂（タマポリ株式会社製、商品名「ＳＫ６１５Ｐ」）を用意した。このポリエチレン樹脂を第１の押出機、第３の押出機にそれぞれ供給して１３０℃で溶融混練した。 Next, a linear low-density polyethylene resin (Tama Poly Co., Ltd., trade name "SK615P") was prepared as the polyethylene resin for the first layer and the third layer. The polyethylene resin was supplied to the first extruder and the third extruder, respectively, and melt-kneaded at 130°C.
　発泡性樹脂組成物を第２の押出機から、第１の層用のポリエチレン樹脂を第１の押出機から、第３の層用のポリエチレン樹脂を第３の押出機から、それぞれ共押出しすることにより、発泡性樹脂組成物からなる層（第２の層）と、該層の両面に積層された樹脂フィルム（第１の層及び第３の層）とを備えた未発泡の多層積層体シートを得た。
　次に、多層積層体シートに対して加速電圧５００ｋＶの電子線を２．５Ｍｒａｄ照射して架橋した後、熱風及び赤外線ヒーターにより２５０℃に保持された発泡炉内に連続的に送り込んで加熱して発泡させることにより、第１の層（樹脂フィルム）、第２の層（発泡体）、及び第３の層（樹脂フィルム）をこの順に有する多層発泡体シートを得た。 Co-extruding the expandable resin composition from the second extruder, the polyethylene resin for the first layer from the first extruder, and the polyethylene resin for the third layer from the third extruder. According to, an unfoamed multilayer laminate sheet comprising a layer (second layer) made of a foamable resin composition and resin films (first layer and third layer) laminated on both surfaces of the layer Got
Next, the multilayer laminate sheet was irradiated with an electron beam having an accelerating voltage of 500 kV at 2.5 Mrad to crosslink, and then continuously fed into a foaming furnace kept at 250° C. by hot air and an infrared heater to be heated. By foaming, a multilayer foam sheet having a first layer (resin film), a second layer (foam body), and a third layer (resin film) in this order was obtained.
［実施例２～１４、比較例１～２］
　第１～第３の層に使用する樹脂の種類、第２の層の厚み、第１及び第３の層の厚みを表１に記載のとおりに変更した。また、発泡剤の配合量を変えることにより、第２層の発泡倍率を表１に記載のとおりに変更した。さらに、発泡剤を配合することにより第３層の気泡率を表１のとおり変更した。それ以外は、実施例１と同様に多層発泡体シートを製造した。
　なお、各樹脂の詳細は、以下の通りである。
　ＳＥＢＳ：ＳＥＢＳ、ＪＳＲ株式会社製、製品名「ＤＹＮＡＲＯＮ　８６００Ｐ」
　ＳＦ６２５Ｐ：直鎖状低密度ポリエチレン、タマポリ株式会社製、商品名「ＳＦ６２５Ｐ」
　ＳＢ－７：エチレン―酢酸ビニル共重合体、タマポリ株式会社製、商品名「ＳＢ－７」
　ＨＤ：高密度ポリエチレン、タマポリ株式会社製、商品名「ＨＤ」 [Examples 2-14, Comparative Examples 1-2]
The types of resin used for the first to third layers, the thickness of the second layer, and the thicknesses of the first and third layers were changed as shown in Table 1. Moreover, the expansion ratio of the second layer was changed as shown in Table 1 by changing the blending amount of the foaming agent. Further, the bubble ratio of the third layer was changed as shown in Table 1 by blending a foaming agent. A multilayer foam sheet was produced in the same manner as in Example 1 except for the above.
The details of each resin are as follows.
SEBS: SEBS, manufactured by JSR Corporation, product name "DYNARON 8600P"
SF625P: Linear low-density polyethylene, manufactured by TamaPoly Co., Ltd., trade name "SF625P"
SB-7: Ethylene-vinyl acetate copolymer, manufactured by TamaPoly Co., Ltd., trade name "SB-7"
HD: High-density polyethylene, Tama Poly Co., Ltd., trade name "HD"
　実施例及び比較例で得られた多層発泡体シートの特性、及び折れジワの評価結果について表１に示す。 Table 1 shows the characteristics of the multilayer foam sheets obtained in the examples and comparative examples, and the evaluation results of creases.
Figure JPOXMLDOC01-appb-T000001
※表１における曲げ応力は、第１及び第３の層の両方の曲げ応力を示す。
Figure JPOXMLDOC01-appb-T000001
*The bending stress in Table 1 indicates the bending stress of both the first and third layers.
　実施例及び比較例の結果より明らかなように、各曲率半径における第３の層の曲げ応力を１．６ＭＰａ以下とすることで、その曲率半径を有する紙芯に、第３の層を内側にして巻き付けた場合に折れジワの発生を抑制することができた。 As is clear from the results of Examples and Comparative Examples, by setting the bending stress of the third layer at each radius of curvature to 1.6 MPa or less, the paper core having the radius of curvature has the third layer inside. It was possible to suppress the generation of creases when it was wrapped around.
　１０　多層発泡体シート
　１１　第１の樹脂層
　１２　第２の樹脂層
　１３　第３の樹脂層
　１４、１５　接着層
　Ｃ，Ｃ２　中立点
　Ｓ，Ｓ２　距離 10 Multilayer Foam Sheet 11 First Resin Layer 12 Second Resin Layer 13 Third Resin Layer 14, 15 Adhesive Layer C, C2 Neutral Point S, S2 Distance

Claims (15)

  1. 　樹脂フィルム又は発泡体からなる第１の樹脂層、発泡体からなる第２の樹脂層、及び樹脂フィルム又は発泡体からなる第３の樹脂層をこの順に備え、曲率半径（Ｒ）が１５２．４ｍｍである場合に下記式（１）で規定される前記第３の樹脂層の曲げ応力が１．６ＭＰａ以下である多層発泡体シート。
    　第３の樹脂層の曲げ応力＝Ｄ×Ｓ／Ｒ　・・・（１）
    　Ｄ：第３の樹脂層のＭＤ方向の引張弾性率（ＭＰａ）
    　Ｓ：第１の樹脂層の中立点から、第３の樹脂層における第２の樹脂層とは反対側の面までの距離（ｍｍ）
    　Ｒ：曲率半径     A first resin layer made of a resin film or foam, a second resin layer made of foam, and a third resin layer made of resin film or foam are provided in this order, and the radius of curvature (R) is 152.4 mm. And the bending stress of the third resin layer defined by the following formula (1) is 1.6 MPa or less.
    Bending stress of third resin layer=D×S/R (1)
    D: MD tensile modulus of the third resin layer (MPa)
    S: Distance from the neutral point of the first resin layer to the surface of the third resin layer opposite to the second resin layer (mm)
    R: radius of curvature
  2. 　２５％圧縮強度が８００ｋＰａ以下である、請求項１に記載の多層発泡体シート。 The multilayer foam sheet according to claim 1, having a 25% compressive strength of 800 kPa or less.
  3. 　前記多層発泡体シートの総厚みが５０～２０００μｍである、請求項１又は２に記載の多層発泡体シート。 The multilayer foam sheet according to claim 1 or 2, wherein the total thickness of the multilayer foam sheet is 50 to 2000 µm.
  4. 　前記第３の樹脂層のＭＤ方向の引張強度が１．５Ｎ以上である、請求項１～３のいずれか１項に記載の多層発泡体シート。 The multilayer foam sheet according to any one of claims 1 to 3, wherein the tensile strength in the MD direction of the third resin layer is 1.5 N or more.
  5. 　前記第１の樹脂層と前記第３の樹脂層の合計厚みが、多層発泡体シートの総厚みの５０％以下である、請求項１～４のいずれか１項に記載の多層発泡体シート。 The multilayer foam sheet according to any one of claims 1 to 4, wherein the total thickness of the first resin layer and the third resin layer is 50% or less of the total thickness of the multilayer foam sheet.
  6. 　曲率半径（Ｒ）が１０１．６ｍｍである場合に上記式（１）で規定される前記第３の樹脂層の曲げ応力が１．６ＭＰａ以下である、請求項１～５のいずれか１項に記載の多層発泡体シート。 The bending stress of the third resin layer defined by the above formula (1) is 1.6 MPa or less when the radius of curvature (R) is 101.6 mm, according to any one of claims 1 to 5. The multilayer foam sheet described.
  7. 　曲率半径（Ｒ）が７６．２ｍｍである場合に上記（１）で規定される前記第３の樹脂層の曲げ応力が１．６ＭＰａ以下である、請求項１～６のいずれか１項に記載の多層発泡体シート。 7. The bending stress of the third resin layer defined by the above (1) is 1.6 MPa or less when the radius of curvature (R) is 76.2 mm, and the bending stress is 1.6 MPa or less. Multilayer foam sheet.
  8. 　曲率半径（Ｒ２）が１５２．４ｍｍである場合に下記式（２）で規定される前記第１の樹脂層の曲げ応力が１．６ＭＰａ以下である請求項１～７のいずれか１項に記載の多層発泡体シート。
    　第１の樹脂層の曲げ応力＝Ｄ２×Ｓ２／Ｒ２　・・・（２）
    　Ｄ２：第１の樹脂層のＭＤ方向の引張弾性率（ＭＰａ）
    　Ｓ２：第３の樹脂層の中立点から、第１の樹脂層における第２の樹脂層とは反対側の面までの距離（ｍｍ）
    　Ｒ２：曲率半径     8. The bending stress of the first resin layer defined by the following formula (2) is 1.6 MPa or less when the radius of curvature (R2) is 152.4 mm. Multilayer foam sheet.
    Bending stress of first resin layer=D2×S2/R2 (2)
    D2: MD elastic modulus of the first resin layer (MPa)
    S2: Distance from the neutral point of the third resin layer to the surface of the first resin layer opposite to the second resin layer (mm)
    R2: radius of curvature
  9. 　曲率半径（Ｒ２）が１０１．６ｍｍである場合に上記式（２）で規定される前記第１の樹脂層の曲げ応力が１．６ＭＰａ以下である、請求項８に記載の多層発泡体シート。 The multilayer foam sheet according to claim 8, wherein the bending stress of the first resin layer defined by the above formula (2) is 1.6 MPa or less when the radius of curvature (R2) is 101.6 mm.
  10. 　曲率半径（Ｒ２）が７６．２ｍｍである場合に上記式（２）で規定される前記第１の樹脂層の曲げ応力が１．６ＭＰａ以下である、請求項８又は９に記載の多層発泡体シート。 The multilayer foam according to claim 8 or 9, wherein the bending stress of the first resin layer defined by the formula (2) is 1.6 MPa or less when the radius of curvature (R2) is 76.2 mm. Sheet.
  11. 　前記第１の樹脂層の引張強度が１．５Ｎ以上である、請求項１～１０いずれか１項に記載の多層発泡体シート。 The multilayer foam sheet according to any one of claims 1 to 10, wherein the tensile strength of the first resin layer is 1.5 N or more.
  12. 　前記第２の樹脂層を構成する樹脂が、ポリオレフィン系樹脂、ポリウレタン系樹脂、アクリル系樹脂、及び熱可塑性エラストマーからなる群から選ばれる１種以上である、請求項１～１１のいずれか１項に記載の多層発泡体シート。 12. The resin constituting the second resin layer is one or more selected from the group consisting of a polyolefin resin, a polyurethane resin, an acrylic resin, and a thermoplastic elastomer, and any one of them. The multilayer foam sheet according to.
  13. 　前記第２の樹脂層を構成する樹脂が、ポリオレフィン樹脂、及び熱可塑性エラストマーからなる群から選ばれる１種以上である、請求項１～１２のいずれか１項に記載の多層発泡体シート。 The multilayer foam sheet according to any one of claims 1 to 12, wherein the resin forming the second resin layer is at least one selected from the group consisting of a polyolefin resin and a thermoplastic elastomer.
  14. 　前記第１の樹脂層及び前記第３の樹脂層の気泡率が６６％以下である、請求項１～１３のいずれか１項に記載の多層発泡体シート。 The multilayer foam sheet according to any one of claims 1 to 13, wherein the first resin layer and the third resin layer have a bubble ratio of 66% or less.
  15. 　請求項１～１４のいずれか１項に記載の多層発泡体シートと、前記多層発泡体シートの少なくとも一方の面に設けられる粘着材とを備える、粘着テープ。 An adhesive tape comprising the multilayer foam sheet according to any one of claims 1 to 14, and an adhesive material provided on at least one surface of the multilayer foam sheet.
PCT/JP2020/003509 2019-01-31 2020-01-30 Multilayer foam sheet WO2020158886A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
JP2020516941A JPWO2020158886A1 (en) 2019-01-31 2020-01-30 Multi-layer foam sheet
KR1020217023847A KR20210121049A (en) 2019-01-31 2020-01-30 Multilayer Foam Sheet
CN202080011075.3A CN113348072A (en) 2019-01-31 2020-01-30 Multilayer foam sheet

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2019-016361 2019-01-31
JP2019016361 2019-01-31

Publications (1)

Publication Number Publication Date
WO2020158886A1 true WO2020158886A1 (en) 2020-08-06

Family

ID=71841871

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2020/003509 WO2020158886A1 (en) 2019-01-31 2020-01-30 Multilayer foam sheet

Country Status (4)

Country Link
JP (1) JPWO2020158886A1 (en)
KR (1) KR20210121049A (en)
CN (1) CN113348072A (en)
WO (1) WO2020158886A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2022030649A1 (en) * 2020-08-07 2022-02-10 積水化学工業株式会社 Multilayer foam sheet

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000141528A (en) * 1998-11-16 2000-05-23 Kanegafuchi Chem Ind Co Ltd Foam laminated sheet for car interior material
JP2002331624A (en) * 2001-03-08 2002-11-19 Jsp Corp Multilayered polypropylene resin foamed sheet and assembling box therefor
JP2004230795A (en) * 2003-01-31 2004-08-19 Asahi Kasei Life & Living Corp Styrene-based resin laminated sheet and container
JP2011005797A (en) * 2009-06-29 2011-01-13 Dainippon Printing Co Ltd Heat insulating material for electronic part and method of manufacturing the same
WO2011024849A1 (en) * 2009-08-25 2011-03-03 旭化成イーマテリアルズ株式会社 Roll of microporous film and process for production thereof
WO2016047610A1 (en) * 2014-09-24 2016-03-31 日東電工株式会社 Laminate

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0867080A (en) * 1994-08-30 1996-03-12 Toray Ind Inc Thermosensitive stencil printing sheet
JP4666541B2 (en) * 2000-06-09 2011-04-06 日東電工株式会社 Cover sheet
JP4803721B2 (en) * 2005-12-22 2011-10-26 株式会社ジェイエスピー Polyethylene resin laminated foam
JP5808156B2 (en) * 2011-06-08 2015-11-10 株式会社石山製作所 Multilayer adsorption sheet
JP6207009B2 (en) 2012-07-03 2017-10-04 積水化学工業株式会社 Cross-linked polyolefin resin foam sheet
KR20170008063A (en) * 2015-07-13 2017-01-23 주식회사 서연이화 Multi-layered composites for car interior base material and method for manufacturing the same
EP3511158A4 (en) * 2016-09-12 2020-04-08 Sekisui Chemical Co., Ltd. Resin laminate
WO2018084318A1 (en) * 2016-11-07 2018-05-11 積水化学工業株式会社 Multilayer foam sheet, method for producing multilayer foam sheet, and adhesive tape
CN108973281B (en) * 2017-05-26 2020-01-03 住友化学株式会社 Resin laminate

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000141528A (en) * 1998-11-16 2000-05-23 Kanegafuchi Chem Ind Co Ltd Foam laminated sheet for car interior material
JP2002331624A (en) * 2001-03-08 2002-11-19 Jsp Corp Multilayered polypropylene resin foamed sheet and assembling box therefor
JP2004230795A (en) * 2003-01-31 2004-08-19 Asahi Kasei Life & Living Corp Styrene-based resin laminated sheet and container
JP2011005797A (en) * 2009-06-29 2011-01-13 Dainippon Printing Co Ltd Heat insulating material for electronic part and method of manufacturing the same
WO2011024849A1 (en) * 2009-08-25 2011-03-03 旭化成イーマテリアルズ株式会社 Roll of microporous film and process for production thereof
WO2016047610A1 (en) * 2014-09-24 2016-03-31 日東電工株式会社 Laminate

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2022030649A1 (en) * 2020-08-07 2022-02-10 積水化学工業株式会社 Multilayer foam sheet
JPWO2022030649A1 (en) * 2020-08-07 2022-02-10
JP7316371B2 (en) 2020-08-07 2023-07-27 積水化学工業株式会社 multilayer foam sheet

Also Published As

Publication number Publication date
JPWO2020158886A1 (en) 2021-12-09
KR20210121049A (en) 2021-10-07
CN113348072A (en) 2021-09-03

Similar Documents

Publication Publication Date Title
JP7145069B2 (en) Multilayer foam sheet, method for manufacturing multilayer foam sheet, and adhesive tape
WO2019235529A1 (en) Resin foam sheet
JP7295623B2 (en) Polyolefin resin foam sheet and adhesive tape using the same
WO2020158886A1 (en) Multilayer foam sheet
JP7188896B2 (en) Cushion material for electronic parts and adhesive tape for electronic parts
JP7453768B2 (en) Foam sheets and adhesive tapes
JP7265374B2 (en) Foam composite sheet and adhesive tape
WO2021201044A1 (en) Foam sheet
KR20160140570A (en) Adhesive tape and method for producing adhesive tape
JP7316371B2 (en) multilayer foam sheet
TWI822749B (en) Foam composite sheets, adhesive tapes, buffer materials for electronic parts and adhesive tapes for electronic parts
JP2020037602A (en) Resin foam sheet
WO2023176984A1 (en) Foam sheet and adhesive tape
KR102667549B1 (en) Foam composite sheets, adhesive tapes, cushioning materials for electronic components, and adhesive tapes for electronic components
JP2023051882A (en) Multilayer foam sheet and adhesive tape
US20230382082A1 (en) Multilayer foam sheet and adhesive tape
JP2022131586A (en) Multilayer foam sheet and adhesive tape
JP2022064669A (en) Multilayer foam sheet and adhesive tape
WO2023176985A1 (en) Foam sheet and adhesive tape
JP6898109B2 (en) Resin foam sheet and its manufacturing method
JP2023040961A (en) foam
JP2023040958A (en) foam sheet
JP2023040962A (en) foam

Legal Events

Date Code Title Description
ENP Entry into the national phase

Ref document number: 2020516941

Country of ref document: JP

Kind code of ref document: A

121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 20747846

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 20747846

Country of ref document: EP

Kind code of ref document: A1