Resin foam sheet and method for producing the same

Abstract

To provide a resin foam sheet which enables high foam molding, has good appearance and flexibility, has mechanical characteristics such as high elastic modulus, high elongation and high peeling strength, and produced at a lower cost.SOLUTION: A resin foam sheet is formed by foaming a resin composition containing a polyolefin resin, a copolymer, and a polymer (A) including the following structure (formula 1), wherein the resin foam sheet has a gel fraction of measured according to JIS K 6796:1998 of 10 to 45 mass%. (Formula 1) R1-Si-O-R2. R1 in the formula 1 is a group having a hydrocarbon skeleton including a repeated structure, R2 is an alkyl group, or a group having the following structure (Formula 2). (Formula 2) -Si-R3. R3 in the formula 2 is a group having a hydrocarbon skeleton including a repeated structure.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a resin foam sheet and a method for manufacturing the same.

[0002] As a shock absorber for precision equipment such as electronic devices and parts used in electronic devices, foam sheets are required to be thinner and have higher performance as electronic devices are miniaturized. Generally, resins such as urethane resins are used as the foam, but since urethane resins are thermosetting, their recyclability is not very high. On the other hand, thermoplastic olefin resins are useful materials because they have high recyclability, a high degree of freedom in the expansion ratio from low expansion to high expansion, are flexible, and can provide foam sheets excellent in cushioning properties and heat insulation properties. Foam sheets using olefin resins are crosslinked for use in order to improve mechanical properties and heat resistance.

[0003] In addition, resin foam molded products foamed with extremely fine bubbles are required for various applications such as vehicle fuel gauges, beverage water tank gauges, and float valves that open and close flow paths in other precision equipment that uses fluids. As a method for manufacturing a resin foam molded product with fine bubbles, a batch foaming method using carbon dioxide (CO2) as a supercritical fluid is used. In particular, since the foam sheet has a thickness of 5 mm or less, the size of the bubbles is easily limited. In order to adjust the density and mechanical properties of the foam, a foaming method using a supercritical fluid that can obtain fine bubbles is preferably used.

[0004] Patent Document 1 discloses a soft foam (including sheet-like ones) of a specific olefin copolymer having a density of about 10 to 150 kg / m 3 and a method for manufacturing the same.

[0005] Patent Document 2 discloses a branched rubbery olefin-based soft resin (C) composed of an organic peroxide-crosslinked olefin-based copolymer rubber (A) and an organic peroxide-decomposed crystalline olefin resin (B), which is obtained by a kneading reaction of these rubber (A) and resin (B). In its micro-aggregation structure, the organic peroxide-crosslinked olefin-based copolymer rubber (A) exists as a continuous phase, and the organic peroxide-decomposed crystalline olefin resin (B) exists as a discontinuous phase. By foaming the resin composition for foam molding characterized by this, a foam molding having a high foaming ratio, being flexible, and excellent in cushioning properties and heat insulation properties can be obtained.

[0006] Patent Document 3 discloses that an organic peroxide-crosslinked olefin-based copolymer rubber (A) and an organic peroxide-decomposed crystalline olefin resin (B) are kneaded and reacted using a compatibilizing means, and in its micro-aggregation structure, the organic peroxide-crosslinked olefin-based copolymer rubber (A) exists as a continuous phase, and the organic peroxide-decomposed crystalline olefin resin (B) exists as a discontinuous phase in this continuous phase, and a rubbery olefin-based soft resin (C) having a gel fraction (weight percentage of insoluble matter after extraction with boiling xylene at 138 °C for 3 hours) of 10 to 80% is used. By foaming the resin composition for foam molding composed of this, a molded body can be formed by injection molding with a foaming ratio of 3 times or less (including non-foamed ones) and an appropriate foaming ratio. Furthermore, the obtained foam is finally compressed between the damper opening / closing plate and the flange, between the housing and the lid, or between the separators, etc., and is locally pressed or assembled at a thin and narrow place. Even when these are used three-dimensionally, the compression rate can be obtained sufficiently flexibly (without bending), and the quality homogeneity and durability can be maintained in terms of the required functional aspects (air permeability resistance, moisture permeability resistance, heat resistance).

[0007] Patent Document 4 discloses that a foamed product obtained by foaming a rubbery olefin-based soft resin (C) obtained by kneading and reacting an organic peroxide-crosslinked olefin-based copolymer rubber (A) and an organic peroxide-decomposed crystalline olefin resin (B), and having a mixed state in its micro-aggregation structure in which the organic peroxide-crosslinked olefin-based copolymer rubber (A) and the organic peroxide-decomposed crystalline olefin resin (B) are intertwined with each other, can obtain an injection-molded foamed product with high foaming, flexibility, and excellent cushioning and heat insulation properties.

[0008] Patent Document 5 discloses that a foamed product obtained by foaming a resin composition for foaming containing a silane-modified product of a propylene-based copolymer containing ethylene units and / or α-olefin units and having a total blending amount of 0.1 to 20% by weight can obtain a foamed sheet with a high foaming ratio, a small cell diameter, and a good surface appearance.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0010] Although the foamed products proposed in Patent Documents 1 and 2 have excellent characteristics respectively, it has been difficult to require mechanical properties such as high elastic modulus, high elongation, and high peel strength.

[0011] In addition, the foams proposed in Patent Documents 3 and 4 are premised on crosslinking raw materials with crosslinkability, and in order to achieve a predetermined gel fraction, it is stated that known methods such as a method using peroxide, electron beam irradiation, sulfur vulcanization, and silane crosslinking can be used. The methods using peroxide (used in the examples) and sulfur vulcanization, when using a foaming method that utilizes a supercritical fluid for the purpose of obtaining fine bubbles, may be hindered by the peroxide during foaming, and sufficient foaming may not be achieved, risking the inability to perform high-foaming molding. Also, when using electron beam irradiation, the main skeleton such as polypropylene resin may be cut, and there was a risk that the foam could not obtain sufficient mechanical properties. Furthermore, equipment for electron beam irradiation is also required, making the manufacturing process complicated and potentially increasing the manufacturing cost. Also, when using silane crosslinking, a process of contacting with water, warm water, steam, etc. is required to crosslink the silane crosslinking agent, making the manufacturing process complicated and potentially increasing the manufacturing cost. Also, when contacting with moisture such as water, warm water, and steam, crosslinking may be completed inside the extruder before foam molding, making moisture management complicated.

[0012] In addition, according to the description of the examples, the foam proposed in Patent Document 5 requires the addition of an organic peroxide. When using a foaming method that utilizes a supercritical fluid for the purpose of obtaining fine bubbles, foaming may be hindered by the organic peroxide, and sufficient foaming may not be achieved, risking the inability to perform high-foaming molding. Furthermore, in order to promote crosslinking, a process of contacting with water, warm water, steam, etc. is required, moisture management is necessary, the manufacturing process becomes complicated, and there is a risk that the manufacturing cost will increase.

Means for Solving the Problems

[0013] The inventors conducted intensive research and found that a resin foam sheet containing a polyolefin resin, a copolymer, and a compound having a specific structure, and having a gel fraction of 10% or more, enables high-foam molding, and while having flexibility, a foam sheet having high mechanical properties such as elastic modulus, elongation, and peel strength can be obtained, and the manufacturing cost is also low. Further, it was found that the above problems can be solved, and the present invention was completed. That is, the present invention is as follows. The present invention (1) is a resin foam sheet containing a polyolefin resin, a copolymer, and a polymer (A) containing a plurality of structures of the following formula 1, wherein the resin foam sheet has a gel fraction of 10 to 45% by mass or more as measured in accordance with JIS K6796:1998. (Formula 1) R1-Si-O-R2 In formula 1, R1 is a group having a hydrocarbon skeleton containing a repeating structure, and R2 is an alkyl group or a group having a structure of the following formula 2. (Formula 2) -Si-R3 In formula 2, R3 is a group having a hydrocarbon skeleton containing a repeating structure. The present invention (2) is wherein the resin foam sheet has a density of 45 to 650 kg / m 3 as measured in accordance with JIS K7112:1999. The present invention (3) is wherein the resin composition contains 20 to 50 parts by mass of a silane crosslinking agent when the mass of the polyolefin resin is 100 parts by mass. The present invention (4) is wherein the repeating structure of R1 is any one of linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), ethylene vinyl acetate copolymer (EVA), or polypropylene. The present invention (5) is The resin foam sheet according to any one of the above inventions (1) to (4), wherein the repeating structure of R3 is any one of linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), high-density polyethylene (HDPE), ethylene vinyl acetate copolymer (EVA), or polypropylene. The present invention (6) is A method for manufacturing a resin foam sheet according to any one of the above inventions (1) to (5), The method for manufacturing the resin foam sheet is A mixing step of dry-blending a polyolefin resin, a copolymer, and a polymer (A) containing a plurality of structures of Formula 1 to form a resin composition, A foaming step of supercritically foaming the resin composition to obtain a resin foam sheet, The method for manufacturing a resin foam sheet is characterized by not including a step of bringing the resin composition or the resin foam sheet into contact with water, warm water, or steam. (Formula 1) R1-Si-O-R2 In Formula 1, R1 is a group having a hydrocarbon skeleton containing a repeating structure, and R2 is an alkyl group or a group having a structure of Formula 2. (Formula 2) -Si-R3 In Formula 2, R3 is a group having a hydrocarbon skeleton containing a repeating structure. [Advantages of the Invention]

[0014] According to the present invention, it is possible to provide a resin foam sheet that enables high foaming molding, has a good appearance, has flexibility, and has high mechanical properties such as elastic modulus, elongation, and peel strength, and also has a low manufacturing cost. [Brief Description of the Drawings]

[0015]

Figure 1

[0016] The resin foam sheet of the present invention will be described in detail below. <<<Resin foam sheet>>> A resin foam sheet characterized by being formed by foaming a resin composition containing a polyolefin resin, a copolymer, and a polymer (A) containing a plurality of structures of the following formula 1. (Formula 1) R1-Si-O-R2 In formula 1, R1 is a group having a hydrocarbon skeleton containing a repeating structure, and R2 is an alkyl group or a group having a structure of the following formula 2. (Formula 2) -Si-R3 In formula 2, R3 is a group having a hydrocarbon skeleton containing a repeating structure.

[0017] Further, the resin foam sheet of the present invention has a gel fraction measured in accordance with the gel content measurement method described in JIS K6796:1998 "Crosslinked polyethylene (PE-X) pipes and fittings - Estimation of crosslinking degree by measurement of gel content" of 10 to 45% by mass, preferably 13.0 to 40.0% by mass. When the gel fraction of the resin foam sheet is within such a range, the resin foam sheet can be highly foamed, has a good appearance, has flexibility, and can have high mechanical properties such as elastic modulus, elongation, and peel strength.

[0018] Further, the density of the resin foam sheet of the present invention measured in accordance with JIS K7112:1999 "Plastics - Methods for measuring the density and specific gravity of non-foamed plastics" is not particularly limited. For example, it can be 1 to 1000 kg / m 3 and preferably 10 to 900 kg / m 3 more preferably 20 to 800 kg / m 3 even more preferably 25 to 750 kg / m 3 even further preferably 45 to 650 kg / m 3 even further more preferably 57 to 650 kg / m 3 particularly preferably 60 to 100 kg / m 3is most preferred. When the density of the resin foam sheet is within such a range, a resin foam sheet having high mechanical properties such as modulus of elasticity, elongation, peel strength, etc. can be obtained.

[0019] Also, the peel strength measured in the 180-degree peel strength test of the resin foam sheet of the present invention is not particularly limited. For example, the lower limit value can be 0.1 N / cm or more, 0.5 N / cm or more, 1 N / cm or more, 1.5 N / cm or more, 2.0 N / cm or more, 2.5 N / cm or more, and the upper limit value can be 50 N / cm or less, 30 N / cm or less, 15 N / cm or less. When the peel strength measured in the 180-degree peel strength test of the resin foam sheet of the present invention is within such a range, a resin foam sheet having mechanical properties such as high modulus of high elasticity, high elongation, and high peel strength while having flexibility can be obtained.

[0020] A method for measuring the 180-degree peel strength of the resin foam sheet of the present invention will be described. The resin foam sheet is formed into a shape with a length of 150 mm, a width of 10 mm, and a thickness of about 0.1 to 2 mm (preferably 1 mm thick). A 25-μm-thick PET film formed into a shape with a length of 250 mm and a width of 20 mm is bonded to one surface of the resin foam sheet so that the resin foam sheet does not protrude, and an evaluation sample is obtained. When bonding, the ends in the longitudinal direction of the resin foam sheet and the ends in the longitudinal direction of the PET film are bonded so as to be separated by 10 mm or more. Further, the evaluation sample is attached to a SUS304BA finish plate with a length of 300 mm, a width of 50 mm, and a thickness of 5 mm so that the entire surface of the resin foam sheet of the evaluation sample is in contact with the SUS plate. The bonding operation is performed by reciprocating a 2-kg roller once in an environment of 23°C × 50% RH. Subsequently, the evaluation sample is allowed to stand in an environment of 23°C × 50% RH for 30 minutes for curing. For the measurement, with the evaluation sample as the upper surface, the PET film is fixed to the measuring device. Using a chucking jig equipped with a load cell, one end in the longitudinal direction of the PET film of the evaluation sample is chucked, and the chucking jig is moved substantially horizontally in the 180-degree peeling direction to perform a peeling test (see FIG. 1). The average value of the stress by the load cell at this time is measured as the peel strength. However, when calculating the peel strength, the initial peak value that appears immediately after the start of peeling of the resin foam sheet is removed as noise. More specifically, the peel strength is calculated based on the average value of the test force measured at 0.01-second intervals for 100 mm from a peeling distance of 20 mm to 120 mm, excluding the measurement data from the start of peeling of the resin foam sheet to the point where the peeling distance reaches 20 mm. The test is performed at a moving speed of the chucking jig of 1000 mm / min in an environment of 23°C × 50% RH.

[0021] The resin foam sheet of the present invention may be any of closed cells, open cells, and further semi-open cells. Here, the semi-open cells refer to those in which closed cells and open cells are mixed, and their distribution and composition ratio are not limited.

[0022] The average cell diameter of the cells (air bubbles) of the resin foam sheet of the present invention is not particularly limited, but can be, for example, 1 to 500 μm. The average cell diameter is the average value of the diameters calculated by calculating the area of the cells for 20 randomly selected cells in the cross-sectional image of the resin foam sheet taken using a scanning microscope, using commercially available software, and assuming the area of the cells as the area of a circle.

[0023] The resin foam sheet of the present invention may have an epidermal layer called a skin layer. The skin layer is a layer with a particularly high distribution density of air bubbles formed on the surface that comes into contact with the mold when using a mold during curing and molding of the resin composition, or with a film or coating tool when coating in film form. Also, when the skin layer is not required, it can be used after performing a splitting process to remove the skin layer.

[0024] <<<Raw material (resin composition) of the resin foam sheet>>> The raw material (resin composition) of the resin foam sheet according to the present invention will be described. The resin composition according to the present invention is characterized by including a polyolefin resin, a copolymer, and a polymer (A) containing a plurality of structures of Formula 1.

[0025] Note that the polyolefin resin, the copolymer, and the polymer (A) are different compounds. More specifically, the polymer (A) is a compound having the structure of Formula 1 described later; the polyolefin resin is a compound that does not have the structure of Formula 1 and does not correspond to a thermoplastic elastomer; the copolymer is a compound that does not have the structure of Formula 1 and does not correspond to a polyolefin resin other than a thermoplastic elastomer.

[0026] <<Polyolefin resin>> The polyolefin resin according to the present invention is not particularly limited, and known polyolefin resins can be used. Examples of the polyolefin resin include polyethylene, polypropylene, polybutene-1, ethylene-propylene copolymer, ethylene-α-olefin copolymer, and polymer blends thereof. These can be used alone or in combination of a plurality. The polyethylene may be any of high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, low-density polyethylene, etc., and the polypropylene may be any of atactic, isotactic, syndiotactic, random, etc. Among these, polypropylene is preferable from the viewpoint of high foam moldability. Furthermore, homopolypropylene is more preferable because a resin foam sheet having good appearance, flexibility, and higher mechanical properties such as elastic modulus, elongation, and peel strength can be obtained. Also, random polypropylene is even more preferable because a resin foam sheet having particularly excellent elongation and appearance can be obtained. Random polypropylene is a random copolymer of propylene and an α-olefin other than propylene (for example, ethylene). As the random polypropylene, those having a propylene content in the constituent monomers of 50% by mass or more, 75% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more can be used. As the random polypropylene, known random polypropylene used in the production of foams can be used.

[0027] In the present application, polyolefin resins classified as elastomers are included in the thermoplastic elastomer resins described later and are treated as copolymers.

[0028] The number average molecular weight of the polyolefin resin according to the present invention is not particularly limited as long as the effects of the present invention are not inhibited. The number average molecular weight of the polyolefin resin can be, for example, 10,000 or more and 3,000,000 or less. The number average molecular weight of the polyolefin resin can be measured by gel permeation chromatography.

[0029] The melt mass flow rate of the polyolefin resin according to the present invention (hereinafter sometimes abbreviated as MFR) is preferably 0.1 to 5 g / 10 min, more preferably 0.3 to 2 g / 10 min at 230 °C and 2.16 kgf, mainly in the case of polypropylene, because there is no gas leakage and foaming is easy. The melt flow rate can be measured according to JIS K7210:1999 "Plastics - Test Method for Melt Mass Flow Rate (MFR) and Melt Volume Flow Rate (MVR) of Thermoplastic Plastics".

[0030] <<Copolymer>> The copolymer according to the present invention is not particularly limited as long as it is a copolymer of a plurality of types of polymerizable monomers. As the copolymer, a thermoplastic elastomer is preferred. For example, ethylene-vinyl acetate copolymer (EVA) resin, ethylene-acrylic acid copolymer (EAA), ethylene-methyl acrylate copolymer (EMA), ethylene-methyl methacrylate copolymer (EMMA), ethylene-methacrylic acid copolymer (EMAA), etc. of ethylene-based thermoplastic elastomers; ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), etc. of ethylene-propylene-based thermoplastic elastomers; styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene block copolymer (SI), styrene-isoprene-styrene block copolymer (SIS), hydrogenated polystyrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene copolymer (SEPS), etc. of styrene-based thermoplastic elastomers; polyamide copolymer; thermoplastic polyurethane (TPU) copolymer; acrylic copolymer. These can be used alone or in combination of a plurality. Among these, from the viewpoint of compatibility with the polyolefin resin, EPM, EPDM, SEBS, etc. are preferred. By using a copolymer having high compatibility with the polyolefin, a resin foam sheet having good appearance, flexibility, and higher mechanical properties such as elastic modulus, elongation, and peel strength can be obtained.

[0031] The number average molecular weight of the copolymer is not particularly limited as long as the effects of the present invention are not inhibited. However, from the viewpoint of obtaining a foam with a high expansion ratio by extrusion molding, it is preferable that the viscosity of the resin composition is high. Therefore, it is preferably 250,000 or more, and more preferably 300,000 or more. On the other hand, the upper limit value of the weight average molecular weight is not particularly specified, but it can generally be set to 1,000,000 or less. The number average molecular weight here can be measured by gel permeation chromatography.

[0032] <<Polymer (A)>> The polymer (A) according to the present invention is not particularly limited as long as it has the structure of Formula 1 below. The polymer (A) can be used alone or in combination of two or more. (Formula 1) R1-Si-O-R2 In Formula 1, R1 is a group having a hydrocarbon skeleton containing a repeating structure, and R2 is an alkyl group or a group having the structure of Formula 2 below. (Formula 2) -Si-R3 In Formula 2, R3 is a group having a hydrocarbon skeleton containing a repeating structure.

[0033] R1 is a group having a hydrocarbon skeleton containing a repeating structure and is not particularly limited. As R1, for example, linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), ethylene vinyl acetate copolymer (EVA) or polypropylene can be used as a structure added to silicon. Further, R1 can contain one or more of these. Among these, linear low density polyethylene (LLDPE) and low density polyethylene (LDPE) are preferable because a resin foam sheet having good appearance, flexibility, and higher mechanical properties such as elastic modulus, elongation, and peel strength can be obtained.

[0034] R2 is an alkyl group or a group having the structure of Formula 2. The alkyl group is not particularly limited as long as it does not inhibit the effects of the present invention, and can be, for example, a methyl group, an ethyl group, a propyl group, a butyl group, etc.

[0035] R3 is a group having a hydrocarbon skeleton containing a repeating structure and is not particularly limited. Examples of R3 include linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), ethylene vinyl acetate copolymer (EVA), or polypropylene. R3 can contain one or more of these. Note that R1 and R3 may have the same structure or different structures. Among these, linear low density polyethylene (LLDPE) and low density polyethylene (LDPE) are preferred because a resin foam sheet having good appearance, flexibility, and higher mechanical properties such as elastic modulus, elongation, and peel strength can be obtained.

[0036] The polymer (A) may be prepared by reacting those in which R2 is an alkyl group with each other in a resin composition and subjecting them to silane crosslinking, or those having the structure of Formula 2 may be added. Therefore, it is presumed that the gel content of the foamed resin sheet of the present invention is that of the polymer (A) crosslinked by silane. The polyolefin resin and copolymer according to the present invention are presumed not to contribute to the crosslinking reaction. By having such a crosslinked structure, a resin foam sheet having good appearance, flexibility, and higher mechanical properties such as elastic modulus, elongation, and peel strength without inhibiting foaming can be obtained.

[0037] The melt mass flow rate of the polymer (A) is not particularly limited, but can be, for example, 0.1 to 3.0 g / 10 min. under the measurement conditions of 190 °C and 2.16 kgf, and preferably 0.3 to 1.5 g / 10 min. When the melt mass flow rate of the polymer (A) is within such a range, a resin foam sheet excellent in peel strength can be obtained.

[0038] The melt mass flow rate of the present molecule (A) can be measured in accordance with JIS K7210-1:2014 "Plastics - Methods for determining the melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics - Part 1: Standard test methods".

[0039] As the polymer (A), commercially available products can be used.

[0040] <<Other additives>> The resin composition according to the present invention can contain other additives as long as the effects of the present invention are not inhibited. As the other additives, known ones can be used, and examples of the other additives include other additives such as flame retardants, fillers, catalysts, crystal nucleating agents, pigments, antioxidants, lubricants, foaming nucleating agents, dispersants, antibacterial agents, conductive agents, and surfactants.

[0041] <Flame retardant> As the flame retardant according to the present invention, known ones can be used as long as the effects of the present invention are not inhibited. Examples of the flame retardant include halogenated diphenyl ethers such as degabromodiphenyl ether and octabromodiphenyl ether; halogen compounds such as halogenated polycarbonate; inorganic compounds such as antimony trioxide, antimony tetroxide, antimony pentoxide, sodium pyroantimonate, and aluminum hydroxide; triazine ring-containing compounds; metal hydroxides; phosphate ester-based flame retardants; condensed phosphate ester-based flame retardants; phosphate-based flame retardants; inorganic phosphorus-based flame retardants; dialkylphosphinates; silicone-based flame retardants; metal oxides; boric acid compounds; expanded graphite, etc. These flame retardants can be used alone or in combination of a plurality.

[0042] <Filler> As the filler according to the present invention, known fillers can be used as long as the effects of the present invention are not inhibited. Examples of the filler include graphite, alumina, melamine, and the like. These fillers can be used alone or in combination of two or more.

[0043] <Catalyst> As the catalyst according to the present invention, known catalysts can be used, and a silane crosslinking catalyst can be preferably used. The silane crosslinking catalyst can be used when reacting those in which R2 of the polymer (A) is an alkyl group with each other in the resin composition to effect silane crosslinking. As the catalyst for promoting silane crosslinking, an organometallic compound-based crosslinking catalyst can be used. Examples thereof include dioctyltin dilaurate, dibutyltin dilaurate, stannous acetate, dibutyltin diacetate, dibutyltin dioctoate, zinc caprylate, tetrabutyl titanate, zinc stearate, calcium stearate, and the like. These can be used alone or in combination of two or more.

[0044] Commercially available silane crosslinking catalysts may be used. Examples of commercially available silane crosslinking catalysts include "LZ033", "LZ013", "LZ015H", etc. of Mitsubishi Chemical Corporation. Among these, "LZ033" is preferable because high-foam molding is possible. Note that, as the commercially available silane crosslinking catalyst, those provided as pellets to be molded together with the resin component may also be used.

[0045] The blending amount of the silane crosslinking catalyst can be 0.01 part by mass or more, more preferably 0.1 part by mass, based on 100 parts by mass of the blending amount of the polymer (A) in which R1 is an alkyl group. On the other hand, the upper limit of the blending amount of the silane crosslinking catalyst can be similarly 20 parts by mass or less, preferably 10 parts by mass or less. When the blending amount of the silane crosslinking catalyst is within such a range, the crosslinking of the silane-crosslinkable polyolefin is sufficiently promoted and local crosslinking does not occur, so that a decrease in extrusion moldability, deterioration of appearance, etc. do not occur.

[0046] <Nucleating agent> The crystal nucleating agent according to the present invention is not particularly limited. For example, bis(p-methylbenzylidene)sorbitol, dibenzylidene sorbitol, bis(p-ethylbenzylidene)sorbitol, aluminum hydroxy(t-butylbenzoate), sodium bis(4-t-butylphenyl) phosphate, sodium methylenebis(2,4-di-t-butylphenyl) phosphate salt, potassium rosinate, magnesium rosinate, N,N'-dicyclohexyl-2,6-naphthalenedicarboxamide, N,N',N''-tris(2-methylcyclohexan-1-yl) propane-1,2,3-triylcarboxamide, etc. may be mentioned. These can be used alone or in combination of a plurality. Commercially available products of these crystal nucleating agents may be used, and examples of commercially available products include Gelol of Shin Nippon Rika Co., Ltd. and Adeka Stab NA11 of ADEKA Corporation, etc.

[0047] By using such a crystal nucleating agent, the crystallization temperature of the polyolefin matrix can be shifted to the high temperature side, and a foam with finer bubbles can be obtained.

[0048] The compounding amount of the crystal nucleating agent is not particularly limited. For example, it is preferably 0.01% by mass or more and 0.5% by mass or less, and more preferably 0.01% by mass or more and 0.2% by mass or less, based on the whole resin composition. When the compounding amount of the crystal nucleating agent is within such a range, a foam with finer bubbles can be obtained, so that high foamability can be achieved.

[0049] <Pigment> The pigment according to the present invention is not particularly limited as long as it does not reduce the expansion ratio of the resin composition. For example, carbon black, titanium oxide, isoindoline yellow, monoazo red, gamma quinacridone, copper phthalocyanine blue, etc. may be mentioned.

[0050] <Antioxidant> As the antioxidant according to the present invention, as long as it does not reduce the expansion ratio of the resin composition, it is not particularly limited, and known ones can be used. Examples of the antioxidant include phenolic antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, and the like. Moreover, commercially available antioxidants can be used. Examples of commercially available products include Adeka Stab AO-60 manufactured by ADEKA Corporation and Irganox 1010 manufactured by BASF Japan Ltd. as phenolic antioxidants. These can be used alone or in combination of a plurality.

[0051] The blending amount of the antioxidant is not particularly limited, but when the blending amount of the polyolefin resin is 100 parts by mass, the general blending amount of the antioxidant is 0.1 to 0.2 parts by mass.

[0052] <Blowing nucleating agent> As the blowing nucleating agent according to the present invention, it is not particularly limited, and known ones can be used. Examples of the blowing nucleating agent include oxides such as talc, silica, alumina, mica, titania, zinc oxide, zeolite, calcium carbonate, magnesium carbonate, barium sulfate, aluminum hydroxide, composite oxides, metal carbonates, metal sulfates, metal hydroxides, and the like. These can be used alone or in combination of a plurality.

[0053] The blending amount of the blowing nucleating agent according to the present invention is not particularly limited, but when the blending amount of the polyolefin resin is 100 parts by mass, the general blending amount of the blowing nucleating agent is 1 to 10 parts by mass.

[0054] <Dispersant> The dispersant according to the present invention is not particularly limited, and known ones can be used. Examples of the dispersant include a polymer compound having an acid anhydride group, a low molecular compound having an acid anhydride group, and a silane coupling agent. Examples of the acid anhydride group include maleic anhydride, itaconic anhydride, citraconic anhydride, citric anhydride, etc.; polymer compounds such as polyethylene and polypropylene; low molecular compounds such as dodecenyl succinic anhydride, hexadecenyl succinic anhydride, hexadecyl glutaric anhydride, and octadecyl glutaric anhydride; and silane coupling agents such as isocyanate silane, aminosilane, mercaptosilane, epoxy silane, vinyl silane, and methacryl silane. These can be used alone or in combination of a plurality.

[0055] <Antibacterial agent> The antibacterial material according to the present invention is not particularly limited, and inorganic compound-based antibacterial agents and organic compound-based antibacterial agents can be used. Examples of the inorganic compound-based antibacterial agents include those in which metals such as silver and copper are supported on inorganic compounds such as zeolite and zirconium phosphate, and metal oxides such as zinc oxide and titanium oxide. Examples of the organic compound-based antibacterial agents include imidazole-based antibacterial agents, thiazoline-based antibacterial agents, and salts of an anionic polymer and a quaternary ammonium salt. These can be used alone or in combination of a plurality.

[0056] <Surfactant> The surfactant according to the present invention is not particularly limited and can be selected according to its use. Nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants can be used. Among these, nonionic surfactants are preferably used because they are less likely to affect the action of other formulations. Examples of nonionic surfactants include polyoxyethylene alkylamines or their unsaturated derivatives; polyoxyethylene alkylalkylene diamines or their unsaturated derivatives, which can be used alone or in combination. Polyoxyethylene alkylamines or their unsaturated derivatives are surfactants having a polyoxyethylene (POE) chain consisting of 5 to 15 oxyethylene units and an alkyl group and / or a corresponding unsaturated hydrocarbon group in the molecule to obtain the required HLB. Examples include POE dodecylamine, POE myristylamine, POE palmitylamine, POE stearylamine, POE oleylamine, and mixed POE hydrocarbon amines having a hydrocarbon group derived from natural oils such as coconut oil and beef tallow. Examples of polyoxyethylene alkylalkylene diamines or their unsaturated derivatives include POE stearyl propylene diamine and POE beef tallow hydrocarbon propylene diamine.

[0057] The blending amount of the surfactant according to the present invention is not particularly limited, but when the blending amount of the polyolefin resin is 100 parts by mass, it can be 0.1 to 10 parts by mass.

[0058] The conductive agent according to the present invention is not particularly limited, and known ones can be used. Examples of the conductive agent include conductive carbon black, copper powder, nickel powder, tin oxide, graphene, carbon nanotubes, and the like.

[0059] <<<<Method for manufacturing a resin foam sheet>>>> A preferred example of the method for manufacturing a resin foam sheet of the present invention will be described below. That is, the following description does not limit the method for manufacturing a resin foam sheet in the present invention. The method includes a resin composition mixing step (also simply referred to as a mixing step) and a foaming step, and does not include a step of bringing the resin composition or the resin foam sheet into contact with water, warm water, or steam. When the resin composition or the resin foam sheet is included in the step of contacting with water, warm water, or steam, dedicated manufacturing equipment is required and the process becomes complicated. In addition, as the method for manufacturing the foam resin sheet of the present invention, other steps can be included.

[0060] Here, in the present invention, steam includes steam and superheated steam and does not include saturated steam, that is, steam contained in the air. Therefore, for example, even when the resin composition of the present invention is left standing in an environment of normal temperature and pressure, it is not considered to be in contact with water, warm water, or steam.

[0061] In addition, in the present invention, "contacted with water, warm water, steam, etc." means that the resin composition and the resin foam sheet according to the present invention are directly contacted with water, warm water, steam, etc. The contact method is not particularly limited. For example, when the resin composition and the resin foam sheet are immersed in water or warm water in a container, when water, warm water, or steam is sprayed onto the resin composition and the resin foam sheet, when the resin composition and the resin foam sheet are placed in a steam atmosphere and exposed to water, warm water, steam, etc. can be mentioned. On the other hand, when water, warm water, steam, etc. inevitably come into contact with the resin composition and the resin foam sheet (for example, when water adheres due to condensation or when water is generated as a reaction product), it is not regarded as "contacted with water, warm water, steam, etc.".

[0062] <<<Resin Composition Mixing Step>>> The resin composition mixing step is a step of obtaining a resin composition by dry-blending the polyolefin resin, which is each of the above-described raw materials, the copolymer, and the polymer (A) containing a plurality of structures of the following formula 1. (Formula 1) R1-Si-O-R2 In Formula 1, R1 is a group having a hydrocarbon skeleton containing a repeating structure, and R2 is an alkyl group or a group having the structure of Formula 2 below. (Formula 2) -Si-R3 In Formula 2, R3 is a group having a hydrocarbon skeleton containing a repeating structure. More specifically, each component of the resin composition is put into a resin mixing machine such as a single-screw extruder, a twin-screw extruder, a kneader, a Banbury mixer, etc., and the resin composition is obtained by melt mixing. It is preferable to use a pelletized resin composition. Other components can also be mixed in this step. Here, dry blending is a mixing method that substantially does not contain water.

[0063] <<Blending amount of the copolymer>> The blending amount of the copolymer according to the present invention is not particularly limited. For example, when the blending amount of the polyolefin resin is 100 parts by mass, it can be 1 to 50 parts by mass, preferably 10 to 40 parts by mass. When the blending amount of the copolymer is within such a range, a resin foam sheet having good appearance, flexibility, and higher mechanical properties such as elastic modulus, elongation, and peel strength can be obtained.

[0064] <<Blending amount of polymer (A)>> The blending amount of polymer (A) according to the present invention is not particularly limited. For example, when the blending amount of the polyolefin resin is 100 parts by mass, it can be 10 to 50 parts by mass, preferably 20 to 50 parts by mass, and more preferably 20 to 45 parts by mass. When the blending amount of polymer (A) is within such a range, a resin foam sheet having good appearance, flexibility, and higher mechanical properties such as elastic modulus, elongation, and peel strength can be obtained.

[0065] <<<Foaming process>>> The foaming process according to the present invention is a process of obtaining a resin foam sheet by melt-plasticizing the resin composition obtained in the resin composition mixing process described above using an extruder, impregnating an inert gas in a supercritical state as a foaming agent, and then extruding and molding the olefin resin composition impregnated with this inert gas while reducing the pressure.

[0066] <<Foaming method>> Generally, as a method for foaming a resin composition, there are a method using a chemical foaming agent, supercritical foaming, etc. However, in order to form finer cells (reduce the cell diameter), in this embodiment, it is preferable to perform foaming using supercritical foaming. Hereinafter, the foaming process will be described in more detail.

[0067] <<Foaming agent>> In this step, first, an inert gas in a supercritical state is impregnated as a foaming agent into the molten resin composition. More specifically, in this step, a substance that is a gas in the standard state (the standard state defined in JIS Z8703) is used as the foaming agent, and the molten resin composition is impregnated with the substance in a supercritical state under conditions where the supercritical state of this substance is maintained.

[0068] The substance that is a gas in the standard state is not particularly limited as long as it is a gas in the standard state, but preferably an inert gas is used. As the inert gas used here, gases such as carbon dioxide and nitrogen can be used, and among these, it is preferable to use carbon dioxide. The reason why carbon dioxide is more preferable as a foaming agent is that nitrogen can be impregnated into the resin composition in a relatively small amount, while carbon dioxide can be impregnated into the resin composition in a large amount. If the inert gas as a foaming agent can be impregnated into the resin composition in a large amount, the foaming ratio of the resin composition can be increased, so that a resin foam sheet with a high foaming ratio can be obtained. Also, carbon dioxide has a larger molecular size than nitrogen, so there is also a reason that it is difficult to escape from the resin composition.

[0069] <<Method of impregnating foaming agent>> As a method for impregnating a foaming agent, for example, after the resin composition is melt-plasticized, a foaming agent such as an inert gas that has been pressurized by a gas supply machine and has become supercritical is discharged into the extruder from an injection nozzle provided near the melting zone, and dissolved in the melted resin composition. In such a supercritical state, the solubility in the molten resin further increases, and it becomes possible to mix the foaming agent at a high concentration. As a result, when there is a rapid pressure drop, since the foaming agent is at a high concentration, the generation of gas nuclei increases. Furthermore, since the substance (foaming agent) dissolved at the molecular level vaporizes, the resulting bubbles become fine. As a result, the density of the bubbles formed by the growth of the gas nuclei is greater than in other states even when the porosity is the same. In this way, by introducing a foaming agent such as an inert gas in a supercritical state into the extruder and dissolving it in the melted resin composition, the foaming agent is brought into a state of being dissolved in the resin composition.

[0070] <<Supercritical conditions>> Here, by using an inert gas in a supercritical state as a foaming agent, the average cell diameter of the foam can be refined. The supercritical conditions for refining the average cell diameter are as follows. When the inert gas is carbon dioxide, the pressure must be 7.3 MPa or more and the temperature must be 31 °C or more. Regarding the pressure, it is more preferably 8 MPa or more, and even more preferably 9 MPa or more. The upper limit of the carbon dioxide pressure is not particularly limited, but for example, it is practical to set it to 20 MPa or less. The upper limit value of the carbon dioxide temperature is not particularly limited, but for example, a temperature at which the resin composition does not thermally decompose can be set, for example, 300 °C. Also, when the inert gas is nitrogen, a supercritical state is ensured by setting the pressure to 3.4 MPa or more and the temperature to -147 °C or more.

[0071] <<Pressure reduction and extrusion molding>> Next, the resin composition impregnated with the foaming agent is depressurized to obtain a resin foam sheet. In other words, the resin composition impregnated with a substance that is a gas under standard conditions is disposed under conditions where the supercritical state of the substance is not maintained, thereby foaming the resin composition. For example, an inert gas in a supercritical state is introduced into the resin composition melted in an extruder, and under predetermined supercritical conditions (for example, when the inert gas is carbon dioxide, at a temperature of 31°C or higher and a pressure of 7.3 MPa or higher), it is discharged from the die orifice and rapidly depressurized to atmospheric pressure and cooled, whereby a resin foam sheet having small and fine cells can be obtained. Note that, for example, when the inert gas is carbon dioxide, by setting the temperature to 31°C or higher and the pressure to 7.3 MPa or higher, carbon dioxide can maintain the supercritical state, so that the resin composition and supercritical carbon dioxide are uniformly mixed.

[0072] Further, in the mixing of the resin composition and the inert gas in the supercritical state, it is preferable to use two or more connected extruders (tandem extruders) so as not to be released to the atmosphere and fall below the above pressure, and to make the process line length of the mixing and extrusion treatment longer and adjust the temperature by lowering the temperature of the mixture. The resin composition immediately before foaming preferably has a temperature near the pour point of the composition. By keeping the temperature low, the pressure difference before and after foaming becomes large, a large number of bubble growth nuclei are generated, and a resin foam sheet having fine cells can be obtained. Further, after foaming, the resin composition can be cooled and solidified more rapidly. Therefore, the growth of the bubbles can be stopped at an early stage, and it becomes easier to obtain a resin foam sheet having a small average cell diameter.

[0073] The die structure in the extruder is not particularly limited, and examples include a T-die and a circular die. Among these, a circular die is preferable because a resin foam sheet having a uniform thickness can be obtained. When a circular die is used, a cylindrical foam can be obtained, but it can be formed into a sheet shape by cutting one side. In this way, during extrusion molding, a long sheet-like foam can be continuously molded directly by selecting a T-die or through a cylindrical foam by selecting a circular die.

[0074] As described above, by dissolving a substance that is a gas under standard conditions (e.g., an inert gas) in the resin composition under high pressure, the gas nuclei are uniformly dispersed at the molecular level. Then, when the pressure is released under normal pressure, foaming occurs from the inside and fine bubbles are formed. That is, fine bubbles are formed by utilizing the solubility difference of the resin composition under pressure. When foaming, it is only necessary to release the pressure. Just by simply extruding the resin composition from an extruder, the pressure applied to the resin composition decreases to about atmospheric pressure, so a decompression device is not required.

[0075] As described above, the formed resin foam sheet can be slit processed to remove the skin layer or adjust the thickness. The thickness of the resin foam sheet after slitting is not particularly limited, but it can be 0.5 mm or more.

[0076] Also, the formed resin foam sheet can be rolled using a hot roll. At this time, the temperature of the hot roll is not particularly limited, but for example, it can be heated to 110 to 160°C. The thickness of the resin foam sheet after hot rolling can be 0.05 mm or more.

[0077] <<<<Applications of the Resin Foam Sheet>>>> The applications of the resin foam sheet of the present invention are not particularly limited. For example, it can be used as an impact absorber for electronic devices such as liquid crystal panels and OLED panels, and electronic device components installed inside electronic devices. Also, it can be used as a sealing material (such as a gasket) for flow path opening and closing components such as float valves for vehicle fuel gauges, beverage water tanks, and other precision instruments that use fluids. Further, as a sheet that utilizes the heat insulation and cushioning properties of the foam, it can be particularly used for applications of resin foam sheets for cold insulation or as a heat insulating agent. Also, by laminating, it can be used as a base material (core material) for double-sided tapes that require high density and high peel strength.

Examples

[0078] <Production of Resin Foam Sheet> The resin compositions of each example and comparative example were prepared with the compounding amounts shown in the table. Each resin composition was melted and prepared using a twin-screw extruder manufactured by Japan Steel Works, and after impregnating with supercritical carbon dioxide under the conditions of a temperature of 31°C or higher and a pressure of 7.3 MPa or higher, the molten material was extruded to produce a resin foam sheet. The produced resin foam sheet had a thickness of 2 mm and had a skin layer. Thereafter, the skin layer was removed by slitting to obtain a resin foam sheet with a thickness of 1 mm, and those formed to 1 mm or less by rolling with a hot roll were used as the resin foam sheets of each example and comparative example. The resin foam sheet of Example 6 was produced by rolling the resin foam sheet of Example 3 with a hot roll at 130°C.

[0079] The following shows each raw material. (Raw Material) · Polyolefin resin Homopolypropylene (H-PP) MFR 0.5 g / 10 min. (230°C, 2.16 kg) Random polypropylene (R-PP) MFR 0.5 g / 10 min. (230°C, 2.16 kg) · Copolymer EPM resin: Composition ratio ethylene / diene = 64 / 5.4, oil extension amount 40 phr, Mooney viscosity (ML(1+4) 125°C) 51 SEBS resin 1: Composition ratio styrene / ethylene·butylene ratio = 18 / 82, MFR 4.5 g / 10 min. (230°C, 2.16 kg) SEBS resin 2: Composition ratio styrene / ethylene·butylene ratio = 42 / 58, MFR 0.8 g / 10 min. (230°C, 2.16 kg) · Polymer (A) Low-density PE-based polymer 1 MFR 1.7 g / 10 min. (190°C, 2.16 kg) Density 0.87 g / cm 3 Low-density PE-based polymer 2 MFR 0.9 g / 10 min. (190°C, 2.16 kg) Density 0.92 g / cm 3 Note that the low-density PE-based polymer 1 and the low-density PE-based polymer 2 are network polymers having a crosslinked structure of R1-Si-O-Si-R3. · Catalyst Metal catalyst: Linklon LZ033 manufactured by Mitsubishi Chemical Corporation

[0080] <Evaluation method> (Gel fraction) The gel fraction of the resin foam sheets of each example and comparative example was measured according to the method for measuring the gel content described in JIS K6796:1998 "Crosslinked polyethylene (PE-X) pipes and fittings - Estimation of crosslinking degree by measurement of gel content". The results are shown in a table.

[0081] (Measurement of density) The density of the resin foam sheets of each example and comparative example was measured according to the water displacement method of JIS K7112:1999 "Plastics - Methods for measuring the density and specific gravity of non-foamed plastics". The results are shown in a table.

[0082] (Tensile modulus of elasticity) The tensile modulus of elasticity of the resin foam sheets of each example and comparative example was measured according to JIS K6767:1999 "Foamed plastics - Test methods for polyethylene". The results are shown in a table.

[0083] (Tensile elongation) The tensile elongation of the resin foam sheets of each example and comparative example was measured according to JIS K6767:1999 "Foamed plastics - Test methods for polyethylene". In addition, the tensile elongation evaluation was performed according to the following criteria. The results are shown in a table. Criteria ◎: Tensile elongation is 150% or more 〇: Tensile elongation is 100% or more and less than 150% △: Tensile elongation is less than 100%

[0084] (Compression hardness, flexibility evaluation) The compression hardness of the resin foam sheets of each example and comparative example was measured in accordance with JIS K6767:1999 "Foamed Plastics - Test Methods for Polyethylene". The results are shown in a table. The flexibility evaluation can be performed, for example, according to the following criteria. Criteria 〇: Compression hardness is less than 0.1 MPa △: Compression hardness is 0.1 MPa or more

[0085] (Compression set) The tensile elongation of the resin foam sheets of each example and comparative example was measured in accordance with JIS K6767:1999 "Foamed Plastics - Test Methods for Polyethylene". The results are shown in a table. In the table, "-" indicates those that could not be measured due to poor foaming.

[0086] (Peel strength, peelability evaluation) The resin foam sheets of each example and comparative example were formed into a shape of 150 mm in length × 10 mm in width, and a 25 μm thick PET film formed into a shape of 250 mm in length × 20 mm in width was bonded to one surface thereof so that the resin foam sheet did not protrude, to obtain an evaluation sample. The thickness of each resin foam sheet was about 0.1 to 2 mm. When bonding, the longitudinal end of the resin foam sheet and the longitudinal end of the PET film were bonded so as to be separated by 10 mm or more. Further, the evaluation sample was bonded to a SUS304BA finished plate of 300 mm in length × 50 mm in width × 5 mm in thickness so that the entire surface of the resin foam sheet of the evaluation sample was in contact with the SUS plate. The bonding operation was performed in an environment of 23°C × 50% RH, and the bonding was performed with a 2 kg roller for one round trip. Subsequently, the evaluation sample was left standing in an environment of 23°C × 50% RH for 30 minutes for curing. For the measurement, with the evaluation sample as the upper surface, the PET film was fixed to the measuring device. Using a chucking jig equipped with a load cell, one longitudinal end of the PET film of the evaluation sample was chucked, and the chucking jig was moved substantially horizontally in the 180-degree peeling direction to perform a peeling test. At this time, the average value of the stress by the load cell was measured as the peel strength. The test was performed in an environment of 23°C × 50% RH with the moving speed of the chucking jig set to 1000 mm / min. In the present application, when the evaluation sample does not peel off at the interface with the adherend (PET film or SUS304BA finish plate) and the evaluation sample splits in the thickness direction (in the case of cohesive failure), the average value of the stress obtained is defined as the peel strength. Further, the peelability evaluation was performed according to the following criteria. The results are shown in a table. Criteria for Judgment ◎: Peel strength is 5 N / cm or more 〇: Peel strength is 3 N / cm or more and less than 5 N / cm △: Peel strength is 1.5 N / cm or more and less than 3 N / cm ×: Peel strength is less than 1.5 N / cm

[0087] (Formability Evaluation) The formability of the resin foam sheets of each example and comparative example was evaluated by visual observation according to the following criteria. The results are shown in a table. Criteria for Judgment 〇: No problem with foam forming △: Foam breakage, slightly shrinking but still formable ×: Foam breakage and shrinkage cause problems with foam forming

[0088] (Appearance Evaluation) The appearance of the resin foam sheets of each example and comparative example was evaluated by visual observation according to the following criteria. The results are shown in a table. Criteria for Judgment 〇: No corrugated pattern △: Slight corrugated pattern (negligible during use) ×: Many corrugated patterns (hindering use)

[0089] (Comprehensive Evaluation) The comprehensive evaluation of each example and comparative example was evaluated based on the following evaluation criteria. The results are shown in a table. Criteria for Judgment ○: Very excellent in elongation, appearance, peel strength, etc. △: Excellent in peel strength, etc., but relatively inferior in appearance ×: Inferior in peel strength, elongation, appearance, etc.

[0090]

Table 1

[0091]

Table 2

[0092]

Table 3

[0093] (Evaluation Results) From the above results, the effects of the present invention can be understood.

Explanation of Reference Signs

[0094] 1 Peel strength measuring device 10 Evaluation sample (foam sheet) 11 SUS304BA finished plate 12 PET film (thickness 25 μm)

Claims

【Claim 1】 A resin foam sheet comprising a polyolefin resin, a thermoplastic elastomer, and a polymer containing the structure of the following formula 1, having a gel fraction of 10 to 45% by mass measured in accordance with JIS K6796:1998, The density measured in accordance with JIS K7112:1999 is 10 to 900 kg / m ３ and having a tensile modulus of elasticity of 0.75 MPa or more measured in accordance with JIS K6767:1999 for the resin foam sheet, having a tensile elongation of 36% or more measured in accordance with JIS K6767:1999 for the resin foam sheet, having a 25% compression hardness of 0.15 MPa or less measured in accordance with JIS K6767:1999 for the resin foam sheet, and having a compression set after 24 hours of 11.5% or less measured in accordance with JIS K6767:1999 for the resin foam sheet. (Formula 1) R 1 -Si-O-Si-R 3 In formula 1, R 1 is a group having a hydrocarbon skeleton containing a repeating structure, and R 3 is a group having a hydrocarbon skeleton containing a repeating structure.

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