JP7478045B2 - Resin foam sheet and method for producing same - Google Patents

Description

The present invention relates to a resin foam sheet and a method for producing the same.

Foam sheets used as shock absorbers for precision equipment such as electronic devices and parts used in electronic devices are required to be thinner and have higher performance as electronic devices become smaller. Generally, resins such as urethane resin are used as foams, but urethane resin is thermosetting and therefore not very recyclable. On the other hand, thermoplastic olefin resin is a useful material because it is highly recyclable, has a high degree of freedom in the expansion ratio from low to high expansion, and can provide foam sheets that are flexible and have excellent cushioning and insulation properties. Foam sheets using olefin resin are used after crosslinking to improve mechanical properties and heat resistance.

In addition, resin foam molded products foamed with extremely fine bubbles are required for various applications such as fuel gauges for vehicles, gauges for drinking water tanks, and float valves for opening and closing flow paths in precision instruments that use fluids. A batch type foaming method using carbon dioxide (CO ₂ ) in a supercritical fluid is used as a method for producing resin foam molded products with fine bubbles. In particular, since a foam sheet has a thickness of 5 mm or less, the size of the bubbles is easily limited, and therefore, 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.

Patent Document 1 discloses a flexible foam (including a sheet-shaped one) made of a specific olefin copolymer having a density of about 10 to 150 kg/m ³ and a method for producing the same.

Patent Document 2 discloses that a branched rubbery olefin-based soft resin (C) is obtained by kneading and reacting the rubber (A) and the resin (B) with each other, and that the resin composition for foam molding is characterized in that the organic peroxide crosslinked olefin-based copolymer rubber (A) exists as a continuous phase and the organic peroxide decomposition type crystalline olefin resin (B) exists as a discontinuous phase in the micro-aggregated structure. By foaming this resin composition for foam molding, a foam molded article that has a high foaming ratio, is flexible, and has excellent cushioning and heat insulation properties can be obtained.

Patent Document 3 discloses that a resin composition for foam molding is obtained by kneading and reacting an organic peroxide-crosslinked olefin copolymer rubber (A) and an organic peroxide-decomposable crystalline olefin resin (B) using a compatibilizing means, and in the micro-aggregated structure, the organic peroxide-crosslinked olefin copolymer rubber (A) exists as a continuous phase, and in this continuous phase, the organic peroxide-decomposable crystalline olefin resin (B) exists as a discontinuous phase, and by foaming a resin composition for foam molding composed of a rubber-like olefin soft resin (C) having a gel fraction (weight percentage of insoluble matter extracted with boiling xylene at 138°C for 3 hours) of 10 to 80%, a molded article can be formed by injection molding at an appropriate foaming ratio with a foaming ratio of 3 times or less (including non-foamed articles). Furthermore, it is disclosed that the resulting foam is ultimately compressed between the damper opening and closing plate and flange, between the housing and the lid, between separators, etc., and is locally pressed or assembled in thin and narrow areas, and even when used in three dimensions, it has a sufficiently flexible compression ratio (no bending), and can maintain the homogeneity and durability of its quality even in the required functional aspects (air resistance, moisture resistance, and heat resistance).

Patent Document 4 discloses that a rubber-like olefin-based soft resin (C) is obtained by a kneading reaction between an organic peroxide crosslinked olefin-based copolymer rubber (A) and an organic peroxide decomposition type crystalline olefin resin (B), and that the rubber-like olefin-based soft resin (C) has a micro-aggregated structure in which the organic peroxide crosslinked olefin-based copolymer rubber (A) and the organic peroxide decomposition type crystalline olefin resin (B) are in a complicated mixed state, and that a foam obtained by foaming the rubber-like olefin-based soft resin (C) can be obtained that is highly foamed, flexible, and has excellent cushioning and heat insulating properties.

Patent Document 5 discloses that a foam obtained by foaming a foaming resin composition containing a silane-modified propylene copolymer containing ethylene units and/or α-olefin units in a total content of 0.1 to 20% by weight can give a foamed sheet with a high expansion ratio, small cell diameter, and good surface appearance.

JP 2008-538377 A JP 2005-133045 A JP 2006-307069 A JP 2006-307070 A JP 2017-179251 A

Although the foams proposed in Patent Documents 1 and 2 each have excellent characteristics, it was difficult to obtain mechanical properties such as high elastic modulus, high elongation, and high peel strength.

In addition, the foams proposed in Patent Documents 3 and 4 are based on the premise that crosslinkable raw materials are crosslinked, and in order to achieve a predetermined gel fraction, known methods such as a method using peroxide, electron beam irradiation, sulfur vulcanization, and silane crosslinking can be used. In the method using peroxide (used in the examples) and sulfur vulcanization, when a foaming method using a supercritical fluid is used to obtain fine bubbles, there is a risk that foaming is hindered by the peroxide, sufficient foaming cannot be achieved, and high foaming molding cannot be performed. In addition, when electron beam irradiation is used, the main skeleton of polypropylene resin, etc. may be cut, and the foam may not be able to obtain sufficient mechanical properties. Furthermore, equipment for electron beam irradiation is also required, which may complicate the manufacturing process and increase the manufacturing cost. In addition, when silane crosslinking is used, a process of contacting with water, hot water, steam, etc. is required to crosslink the silane crosslinking agent, which may complicate the manufacturing process and increase the manufacturing cost. Furthermore, when the material comes into contact with moisture such as water, hot water, or water vapor, crosslinking may be completed inside the extruder before foam molding, making moisture management complicated.

In addition, according to the description of the examples, the foam proposed in Patent Document 5 requires the addition of an organic peroxide, and if a foaming method using a supercritical fluid is used to obtain fine bubbles, there is a risk that foaming will be hindered by the organic peroxide, sufficient foaming will not be achieved, and high-expansion molding will not be possible. Furthermore, in order to promote crosslinking, a process of contacting the material with water, hot water, water vapor, etc. is required, and moisture management is required, which may complicate the manufacturing process and increase manufacturing costs.

The inventors have conducted intensive research and have found that a resin foam sheet containing a polyolefin resin, a copolymer, and a compound having a specific structure, the resin foam sheet having a gel fraction of 10% or more, is capable of being highly foamed and capable of producing a foam sheet having flexibility and high mechanical properties such as elastic modulus, extensibility, and peel strength, and is inexpensive to produce, and further that the above-mentioned problems can be solved, thereby completing the present invention. That is, the present invention is as follows.
The present invention (1) is
A resin foam sheet comprising a polyolefin resin, a copolymer, and a polymer (A) having a plurality of structures represented by the following formula 1:
The resin foam sheet is characterized in that the gel fraction measured in accordance with JIS K6796:1998 is 10 to 45% by mass or more.
(Equation 1)
R ₁ —Si—O—R ₂
In formula 1, R ₁ is a group having a hydrocarbon skeleton containing a repeating structure, and R ₂ is an alkyl group or a group having the structure of formula 2 below.
(Equation 2)
-Si- _R3
R3 in formula 2 is a group having a hydrocarbon skeleton containing a repeating structure.
The present invention (2) is
The resin foam sheet according to the invention (1) is characterized in that the density measured in accordance with JIS K7112:1999 is 45 to 650 kg/ ^m3 .
The present invention (3) is
The resin composition is the resin foam sheet of the invention (1) or (2), characterized in that it contains 20 to 50 parts by mass of a silane crosslinking agent relative to 100 parts by mass of a polyolefin resin.
The present invention (4) is
The resin foam sheet according to any one of the above inventions (1) to (3), 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), and 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), and polypropylene.
The present invention (6) is
The method for producing a resin foam sheet according to any one of the inventions (1) to (5),
The method for producing the resin foam sheet includes:
A mixing step of dry-blending a polyolefin resin, a copolymer, and a polymer (A) containing a plurality of structures represented by the following formula 1 to form a resin composition;
and a foaming step of subjecting the resin composition to supercritical foaming to obtain a resin foam sheet,
The method for producing a resin foam sheet does not include a step of contacting the resin composition or the resin foam sheet with water, hot water, or water vapor.
(Equation 1)
R ₁ —Si—O—R ₂
In formula 1, R ₁ is a group having a hydrocarbon skeleton containing a repeating structure, and R ₂ is an alkyl group or a group having the structure of formula 2 below.
(Equation 2)
-Si- _R3
R3 in formula 2 is a group having a hydrocarbon skeleton containing a repeating structure.

The present invention makes it possible to provide a resin foam sheet that can be molded with high expansion, has a good appearance, is flexible, and has high mechanical properties such as elastic modulus, extensibility, and peel strength, and is inexpensive to manufacture.

FIG. 1 is an explanatory diagram showing a method for measuring the 180-degree peel strength.

The resin foam sheet of the present invention will be described in detail below.
<<<Resin foam sheet>>>
The resin foam sheet is produced by foaming a resin composition containing a polyolefin resin, a copolymer, and a polymer (A) containing a plurality of structures represented by the following formula 1:
(Equation 1)
R ₁ —Si—O—R ₂
In formula 1, R ₁ is a group having a hydrocarbon skeleton containing a repeating structure, and R ₂ is an alkyl group or a group having the structure of formula 2 below.
(Equation 2)
-Si- _R3
R3 in formula 2 is a group having a hydrocarbon skeleton containing a repeating structure.

The resin foam sheet of the present invention has a gel fraction of 10 to 45% by mass, preferably 13.0 to 40.0% by mass, measured according to the method for measuring the gel content described in JIS K6796:1998 "Cross-linked polyethylene (PE-X) pipes and fittings - Estimation of the degree of cross-linking by measuring the gel content". When the gel fraction of the resin foam sheet is within this range, the resin foam sheet can be highly foamed, has a good appearance, and has flexibility while having high mechanical properties such as elastic modulus, extensibility, and peel strength.

The density of the resin foam sheet of the present invention measured in accordance with JIS K7112:1999 "Method of measuring density and specific gravity of plastics-non-foamed plastics" is not particularly limited, but can be, for example, 1 to 1000 kg/m ³ , 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 more preferably 45 to 650 kg/m ³ , particularly preferably 57 to 650 kg/m ³ , and most preferably 60 to 100 kg/m ^3. When the density of the resin foam sheet is within such a range, a resin foam sheet having high mechanical properties such as elastic modulus, extensibility, and peel strength can be obtained.

The peel strength of the resin foam sheet of the present invention measured in a 180-degree peel strength test is not particularly limited, but for example, the lower limit 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, or 2.5 N/cm or more, and the upper limit can be 50 N/cm or less, 30 N/cm or less, or 15 N/cm or less. When the peel strength of the resin foam sheet of the present invention measured in a 180-degree peel strength test is within such a range, a resin foam sheet can be obtained that has mechanical properties such as high elastic modulus, high elongation, and high peel strength while maintaining flexibility.

The 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 molded to a size of 150 mm long x 10 mm wide and a thickness of about 0.1 to 2 mm (preferably 1 mm thick), and a 25 μm thick PET film molded to a size of 250 mm long x 20 mm wide is attached to one surface of the sheet so that the resin foam sheet does not protrude, to obtain an evaluation sample. When attaching, the longitudinal end of the resin foam sheet and the longitudinal end of the PET film are attached so that they are separated by 10 mm or more. Furthermore, the resin foam sheet of the evaluation sample is attached to a SUS304BA finishing plate of 300 mm long x 50 mm wide x 5 mm thick so that the entire surface of the resin foam sheet of the evaluation sample is in contact with the SUS plate. The attachment work is performed by moving a 2 kg roller back and forth once in an environment of 23 ° C x 50% RH. Next, the evaluation sample is left to stand in an environment of 23 ° C x 50% RH for 30 minutes and cured. The measurement is performed by fixing the PET film to the measuring device with the evaluation sample on the top. A chucking jig equipped with a load cell is used to chuck one end of the PET film in the longitudinal direction of the evaluation sample, and the chucking jig is moved horizontally at 180 degrees in the peeling direction to perform the peel test (see Figure 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 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 sec intervals over a 100 mm peel distance from 20 mm to 120 mm, after removing the measurement data from the start of peeling the resin foam sheet to the point where the peel distance becomes 20 mm. The test is performed in an environment of 23°C x 50% RH, with the chucking jig moving at a speed of 1000 mm/min.

The resin foam sheet of the present invention may have closed cells, open cells, or even semi-open cells. Here, semi-open cells refer to a mixture of closed cells and open cells, and there are no limitations on the distribution or composition ratio.

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 was determined by calculating the area of 20 randomly selected cells in a cross-sectional image of the resin foam sheet taken with a scanning microscope, using commercially available software, and calculating the diameter by converting it to the area of a circle.

The resin foam sheet of the present invention may have a surface layer called a skin layer. The skin layer is a layer with a particularly high distribution density of air bubbles that is formed on the surface that comes into contact with a mold when a mold is used for curing and molding the resin composition, or with a film or coating tool when applying the resin composition to a film. In addition, when the skin layer is not necessary, it can be used after removing the skin layer by performing a splitting process.

<<<<Raw materials for resin foam sheet (resin composition)>>>
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 comprising a polyolefin resin, a copolymer, and a polymer (A) containing a plurality of structures represented by formula 1.

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 below; the polyolefin resin is a compound that does not have the structure of formula 1 and does not fall under the category of thermoplastic elastomers; and the copolymer is a compound that does not have the structure of formula 1 and does not fall under the category of polyolefin resins other than thermoplastic elastomers.

<<Polyolefin resin>>
The polyolefin resin according to the present invention is not particularly limited, and known polyolefin resins can be used. Examples of polyolefin resins include polyethylene, polypropylene, polybutene-1, ethylene-propylene copolymer, ethylene-α-olefin copolymer, and polymer blends of these. These can be used alone or in combination. 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 preferred from the viewpoint of high foam moldability. Furthermore, homopolypropylene is more preferred because it is possible to obtain a resin foam sheet that has good appearance and flexibility while having higher mechanical properties such as elastic modulus, elongation, and peel strength. Furthermore, random polypropylene is even more preferred because it is possible to obtain a resin foam sheet that is particularly excellent in elongation and appearance. Random polypropylene is a random copolymer of propylene and an α-olefin other than propylene (e.g., ethylene) or the like. The random polypropylene may have 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, 99% by mass or more, etc. The random polypropylene may be a known random polypropylene used in the production of foams.

In this application, polyolefin resins classified as elastomers are included in the thermoplastic elastomer resins described below and are treated as copolymers.

The number average molecular weight of the polyolefin resin of the present invention is not particularly limited as long as it does not impair the effects of the present invention. 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 emission chromatography.

The melt mass flow rate (hereinafter sometimes abbreviated as MFR) of the polyolefin resin according to the present invention is preferably 0.1 to 5 g/10 min at 230°C and 2.16 kgf, and more preferably 0.3 to 2 g/10 min, mainly in the case of polypropylene, since there is no gas escape and foaming is easy. The melt flow rate can be measured according to JIS K7210:1999 "Test method for melt mass flow rate (MFR) and melt volume flow rate (MVR) of plastics-thermoplastics".

<<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. The copolymer is preferably a thermoplastic elastomer, and examples thereof include ethylene-based thermoplastic elastomers such as ethylene-vinyl acetate copolymer (EVA) resin, ethylene-acrylic acid copolymer (EAA), ethylene-methyl acrylate copolymer (EMA), ethylene-methyl methacrylate copolymer (EMMA), and copolymer of ethylene and methacrylic acid (EMAA); ethylene-propylene-based thermoplastic elastomers such as ethylene-propylene-rubber (EPM) and ethylene-propylene-diene rubber (EPDM); styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene block copolymer (SI), styrene-isoprene-styrene block copolymer (SIS), and styrene-ethylene-butylene-styrene block copolymer (SEBS) and styrene-ethylene-propylene-styrene copolymer (SEPS) which are hydrogenated from these; polyamide copolymers; thermoplastic polyurethane (TPU) copolymers; and acrylic copolymers. These can be used alone or in combination. Among these, from the viewpoint of compatibility with polyolefin resins, preferred are EPM, EPDM, SEBS, etc. By using a copolymer having high compatibility with polyolefin, it is possible to obtain a resin foam sheet having good appearance and flexibility while having higher mechanical properties such as elastic modulus, extensibility, and peel strength.

The number average molecular weight of the copolymer is not particularly limited as long as it does not impair the effects of the present invention. 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, so that it is preferably 250,000 or more, and more preferably 300,000 or more. On the other hand, the upper limit of the weight average molecular weight is not particularly specified, but it can be generally 1,000,000 or less. The number average molecular weight here can be measured by gel permeation emission chromatography.

<<Polymer (A)>>
The polymer (A) according to the present invention is not particularly limited as long as it has the structure of the following formula 1. The polymer (A) may be used alone or in combination of two or more kinds.
(Equation 1)
R ₁ —Si—O—R ₂
In formula 1, R ₁ is a group having a hydrocarbon skeleton containing a repeating structure, and R ₂ is an alkyl group or a group having the structure of formula 2 below.
(Equation 2)
-Si- _R3
R3 in formula 2 is a group having a hydrocarbon skeleton containing a repeating structure.

R ₁ is a group having a hydrocarbon skeleton containing a repeating structure, and is not particularly limited. For example, R ₁ may be a structure in which linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), ethylene vinyl acetate copolymer (EVA) or polypropylene is added to silicon. R ₁ may contain one or more of these. Among these, linear low density polyethylene (LLDPE) and low density polyethylene (LDPE) are preferred because they can provide a resin foam sheet that has good appearance, flexibility, and mechanical properties such as higher elastic modulus, elongation, and peel strength.

_R2 is an alkyl group or a group having a structure of formula 2. The alkyl group is not particularly limited as long as it does not impair the effects of the present invention, and may be a methyl group, an ethyl group, a propyl group, a butyl group, or the like.

_R3 is a group having a hydrocarbon skeleton containing a repeating structure, and is not particularly limited. For example, _R3 can be 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. _R1 and _R3 may have the same structure or different structures. Among these, linear low density polyethylene (LLDPE) and low density polyethylene (LDPE) are preferable because they can provide a resin foam sheet that has good appearance, flexibility, and mechanical properties such as higher elastic modulus, elongation, and peel strength.

The polymer (A) may be prepared by reacting those in which R ₂ is an alkyl group in the resin composition with each other and silane crosslinking, or a polymer in which R ₂ has 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 the polymer (A) crosslinked by silane. It is presumed that the polyolefin resin and copolymer according to the present invention do not contribute to the crosslinking reaction. By making such a crosslinked structure, it is possible to obtain a resin foam sheet that is not inhibited from foaming, has a good appearance, and has flexibility while having higher mechanical properties such as elastic modulus, elongation, and peel strength.

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 measurement conditions of 190°C and 2.16 kgf, and is preferably 0.3 to 1.5 g/10 min. When the melt mass flow rate of the polymer (A) is within this range, a resin foam sheet with excellent peel strength can be obtained.

The melt mass flow rate of this molecule (A) can be measured in accordance with JIS K7210-1:2014 "Plastics - Determination of melt mass flow rate (MFR) and melt volume flow rate (MVR) of thermoplastics - Part 1: Standard test method."

Polymer (A) can be a commercially available product.

<<Other additives>>
The resin composition according to the present invention may contain other additives as long as they do not impair the effects of the present invention. As the other additives, known additives may be used, and examples of the other additives include flame retardants, fillers, catalysts, crystal nucleating agents, pigments, antioxidants, lubricants, foam nucleating agents, dispersants, antibacterial agents, conductive agents, surfactants, and other additives.

<Flame retardants>
As the flame retardant according to the present invention, any known flame retardant can be used as long as it does not impair the effects of the present invention. Examples of the flame retardant include halogenated diphenyl ethers such as degabromdiphenyl ether and octabromdiphenyl ether;
Halogenated compounds such as halogenated polycarbonates;
Inorganic compounds such as antimony trioxide, antimony tetroxide, antimony pentoxide, sodium pyroantimonate, and aluminum hydroxide;
Examples of the flame retardants include triazine ring-containing compounds, metal hydroxides, phosphate ester flame retardants, condensed phosphate ester flame retardants, phosphate flame retardants, inorganic phosphorus flame retardants, dialkyl phosphinates, silicone flame retardants, metal oxides, boric acid compounds, expandable graphite, etc. These flame retardants can be used alone or in combination.

<Filler>
As the filler according to the present invention, any known filler can be used as long as it does not impair the effects of the present invention. Examples of the filler include graphite, alumina, melamine, etc. These fillers can be used alone or in combination.

<Catalyst>
As the catalyst according to the present invention, a known catalyst can be used, but a silane crosslinking catalyst can be preferably used. The silane crosslinking catalyst can be used when polymers (A) in which _R2 is an alkyl group are reacted with each other in a resin composition to perform silane crosslinking. As a catalyst for promoting silane crosslinking, an organometallic compound-based crosslinking catalyst can be used, and examples thereof include dioctyltin dilaurate, dibutyltin dilaurate, stannous acetate, dibutyltin diacetate, dibutyltin dioctoate, zinc caprylate, titanic acid tetrabutyl ester, zinc stearate, calcium stearate, etc. These can be used alone or in combination.

Commercially available silane crosslinking catalysts may be used. Examples of commercially available silane crosslinking catalysts include Mitsubishi Chemical's "LZ033", "LZ013", and "LZ015H". Among these, "LZ033" is preferred because it allows for high expansion molding. Note that commercially available silane crosslinking catalysts provided as pellets to be molded together with the resin component may also be used.

The amount of the silane crosslinking catalyst can be 0.01 parts by mass or more, more preferably 0.1 parts by mass, per 100 parts by mass of the polymer (A) in which R ₁ is an alkyl group. On the other hand, the upper limit of the amount of the silane crosslinking catalyst can be 20 parts by mass or less, preferably 10 parts by mass or less. When the amount of the silane crosslinking catalyst is within this range, the crosslinking of the silane crosslinkable polyolefin is sufficiently promoted and no local crosslinking occurs, so that the extrusion moldability is not deteriorated, the appearance is not deteriorated, and the like is not caused.

<Nucleating Agent>
The crystal nucleating agent according to the present invention is not particularly limited, and examples thereof include bis(p-methylbenzylidene)sorbitol, dibenzylidenesorbitol, bis(p-ethylbenzylidene)sorbitol, aluminum hydroxy(t-butylbenzoate), sodium bis(4-t-butyl-phenyl)phosphate, methylene bis(2,4-di-t-butyl-phenyl)phosphate sodium salt, potassium rosinate, magnesium rosinate, N,N'-dicyclohexyl-2,6-naphthalenedicarboxamide, N,N',N"-tris(2-methylcyclohexan-1-yl)propane-1,2,3-triylcarboxamide, and the like. These can be used alone or in combination of two or more. As these crystal nucleating agents, commercially available ones may be used, and examples of commercially available products include Gelall from New Japan Chemical Co., Ltd. and Adeka STAB NA11 from ADEKA Corporation.

By using such a crystal nucleating agent, the crystallization temperature of the polyolefin matrix can be shifted to a higher temperature, resulting in a foam with finer cells.

The amount of the crystal nucleating agent is not particularly limited, but 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, relative to the entire resin composition. When the amount of the crystal nucleating agent is within this range, a foam with finer bubbles can be obtained, thereby achieving high foamability.

<Pigments>
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, and examples thereof include carbon black, titanium oxide, isoindoline yellow, monoazo red, gamma quinacridone, copper phthalocyanine blue, and the like.

<Antioxidants>
The antioxidant according to the present invention is not particularly limited, and any known antioxidant can be used as long as it does not reduce the expansion ratio of the resin composition. Examples of the antioxidant include phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants.
Commercially available antioxidants can be used, and examples of commercially available antioxidants include phenolic antioxidants such as Adeka STAB AO-60 manufactured by ADEKA CORPORATION and Irganox 1010 manufactured by BASF Japan Ltd. These can be used alone or in combination.

The amount of antioxidant to be used is not particularly limited, but the typical amount is 0.1 to 0.2 parts by mass when the amount of polyolefin resin is 100 parts by mass.

<Foaming nucleating agent>
The foam nucleating agent according to the present invention is not particularly limited, and known ones can be used. Examples of the foam nucleating agent include oxides such as talc, silica, alumina, mica, titania, zinc oxide, zeolite, calcium carbonate, magnesium carbonate, barium sulfate, and aluminum hydroxide, composite oxides, metal carbonates, metal sulfates, and metal hydroxides, and these can be used alone or in combination.

The amount of foam nucleating agent used in the present invention is not particularly limited, but the amount of foam nucleating agent is generally 1 to 10 parts by mass when the amount of polyolefin resin is 100 parts by mass.

<Dispersant>
The dispersant according to the present invention is not particularly limited, and known dispersants can be used. Examples of dispersants include polymer compounds having an acid anhydride group, low molecular compounds having an acid anhydride group, and silane coupling agents. Examples of acid anhydride groups include maleic anhydride, itaconic anhydride, citraconic anhydride, citric anhydride, etc.; polymer compounds and polyethylene, polypropylene, etc.; examples of low molecular compounds include dodecenyl succinic anhydride, hexadecenyl succinic anhydride, hexadecyl glutaric anhydride, octadecyl glutaric anhydride, etc.; examples of silane coupling agents include isocyanate silane, amino silane, mercapto silane, epoxy silane, vinyl silane, and methacryl silane, etc.; these can be used alone or in combination.

<Antibacterial Agent>
The antibacterial material according to the present invention is not particularly limited, but inorganic compound-based antibacterial agents and organic compound-based antibacterial agents can be used. Examples of 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 organic compound-based antibacterial agents include imidazole-based antibacterial agents, thiazoline-based antibacterial agents, and salts of anionic polymers and quaternary ammonium salts. These can be used alone or in combination.

<Surfactant>
The surfactant according to the present invention is not particularly limited and can be selected according to the application, and nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants can be used. Of these, nonionic surfactants are preferably used because they are less likely to affect the action of other compounds. Examples of nonionic surfactants include polyoxyethylene alkylamines or unsaturated derivatives thereof; polyoxyethylene alkyl alkylenediamines or unsaturated derivatives thereof, and can be used alone or in combination. Polyoxyethylene alkylamines or unsaturated derivatives thereof 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 in order to obtain the required HLB, and examples thereof include POE dodecylamine, POE myristylamine, POE palmitylamine, POE stearylamine, POE oleylamine, mixed POE hydrocarbon amines having a hydrocarbon group derived from natural fats and oils such as coconut oil and beef tallow. Examples of polyoxyethylene alkyl alkyl diamines or unsaturated derivatives thereof include POE stearyl propylene diamine, POE tallow hydrocarbon propylene diamine, and the like.

The amount of the surfactant used in the present invention is not particularly limited, but can be 0.1 to 10 parts by mass when the amount of the polyolefin resin is 100 parts by mass.

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

<<<<<Method of manufacturing resin foam sheet>>>>
A preferred example of the method for producing a resin foamed resin sheet of the present invention will be described below. That is, the following description does not limit the method for producing a resin foamed resin sheet in the present invention. The method includes a resin composition mixing step (also simply expressed as a mixing step) and a foaming step, but does not include a step of contacting the resin composition or the resin foamed sheet with water, hot water, or water vapor. If the method includes a step of contacting the resin composition or the resin foamed sheet with water, hot water, or water vapor, a dedicated production facility is required, making the process complicated.
The method for producing a foamed resin sheet of the present invention may also include other steps.

In the present invention, water vapor includes water vapor and superheated water vapor, but does not include saturated water vapor, i.e., water vapor contained in air. Therefore, even if the resin composition of the present invention is left to stand in an environment of normal temperature and normal pressure, it is not considered to have come into contact with water, hot water, or water vapor.

In the present invention, "contact with water, hot water, water vapor, etc." means that the resin composition and the resin foam sheet according to the present invention are directly contacted with water, hot water, water vapor, etc., and the contact method is not particularly limited. For example, the resin composition and the resin foam sheet are immersed in water or hot water in a container, water, hot water, water vapor is sprayed onto the resin composition and the resin foam sheet, and the resin composition and the resin foam sheet are placed in a water vapor atmosphere and exposed to water, hot water, water vapor, etc. On the other hand, when water, hot water, water vapor, etc. inevitably come into contact with the resin composition and the resin foam sheet (for example, when water is attached due to condensation or when water is generated as a reaction product), it is not considered to be "contact with water, hot water, water vapor, etc.".

<<<Resin composition mixing process>>>
The resin composition mixing step is a step of dry-blending the above-mentioned raw materials, ie, the polyolefin resin, the copolymer, and the polymer (A) containing a plurality of structures represented by the following formula 1, to obtain a resin composition.
(Equation 1)
R ₁ —Si—O—R ₂
In formula 1, R ₁ is a group having a hydrocarbon skeleton containing a repeating structure, and R ₂ is an alkyl group or a group having the structure of formula 2 below.
(Equation 2)
-Si- _R3
R3 in formula 2 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 process. Here, dry blending is a mixing method that does not substantially contain water.

<<Amount of copolymer blended>>
The blending amount of the copolymer according to the present invention is not particularly limited, but for example, when the blending amount of the polyolefin resin is taken as 100 parts by mass, it can be 1 to 50 parts by mass, and preferably 10 to 40 parts by mass. When the blending amount of the copolymer is within this range, it is possible to obtain a resin foam sheet that has good appearance and flexibility while having higher mechanical properties such as elastic modulus, extensibility, and peel strength.

<<Amount of Polymer (A)>>
The blending amount of the polymer (A) according to the present invention is not particularly limited, but 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 the polymer (A) is within this range, it is possible to obtain a resin foam sheet that has good appearance and flexibility while having higher mechanical properties such as elastic modulus, extensibility, and peel strength.

<<<<Foaming process>>>
The foam molding process according to the present invention is a process in which the resin composition obtained in the above-mentioned resin composition mixing process is melt-plasticized using an extruder, impregnated with an inert gas in a supercritical state as a foaming agent, and then extrusion-molded the olefin-based resin composition impregnated with the inert gas under reduced pressure to obtain a resin foam sheet.

<<Foaming method>>
Generally, the foaming method of the resin composition includes a method using a chemical foaming agent, supercritical foaming, etc., but in this embodiment, in order to form finer cells (reducing the cell diameter), it is preferable to foam using supercritical foaming. The foaming step will be described in more detail below.

<<Foaming agent>>
In this process, first, the molten resin composition is impregnated with an inert gas in a supercritical state as a foaming agent. More specifically, in this process, a substance that is gaseous under standard conditions (standard conditions 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 that maintain the supercritical state of the substance.

The substance that is a gas under standard conditions is not particularly limited as long as it is a gas under standard conditions, but preferably an inert gas is used. Gases such as carbon dioxide and nitrogen can be used as the inert gas used here, but it is preferable to use carbon dioxide among them. Carbon dioxide is preferable as a foaming agent because a resin composition can be impregnated with a large amount of carbon dioxide, whereas only a relatively small amount of nitrogen can be impregnated with the resin composition. If a large amount of the inert gas as a foaming agent can be impregnated with the resin composition, the expansion ratio of the resin composition can be increased, and a resin foam sheet with a high expansion ratio can be obtained. Another reason is that carbon dioxide is more difficult to escape from the resin composition because the molecular size is larger than that of nitrogen.

<<Method of impregnating foaming agent>>
As a method of impregnating the foaming agent, for example, after the resin composition is melted and plasticized, a foaming agent such as an inert gas that has been pressurized by a gas supply machine and brought to a supercritical state is discharged into the extruder from an injection nozzle provided near the melting zone, and dissolved in the molten resin composition. In such a supercritical state, the solubility in the molten resin is further increased, making it possible to mix the foaming agent at a high concentration. As a result, when the pressure drops suddenly, the foaming agent is highly concentrated, so that more bubble nuclei are generated. Furthermore, the substance (foaming agent) dissolved at the molecular level is vaporized, so that the bubbles that are formed become fine. As a result, the density of the bubbles that are formed by the growth of the bubble nuclei is greater than in other states, even if the porosity is the same. In this way, a foaming agent such as an inert gas in a supercritical state is introduced into the extruder and dissolved in the molten resin composition, thereby making the foaming agent dissolved in the resin composition.

<<Supercritical conditions>>
Here, by using a supercritical inert gas as a foaming agent, the average cell diameter of the foam can be made fine, and the supercritical conditions for making the average cell diameter fine 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. The pressure 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 it is practical to set it to, for example, 20 MPa or less. The upper limit 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. In addition, when the inert gas is nitrogen, the supercritical state is ensured by setting the pressure to 3.4 MPa or more and the temperature to -147 ° C. or more.

<<Decompression and Extrusion Molding>>
Next, the resin composition impregnated with the foaming agent is decompressed to obtain a resin foam sheet. In other words, the resin composition impregnated with a substance that is gaseous under standard conditions is placed under conditions in which the supercritical state of the substance is not maintained, thereby foaming the resin composition. For example, a supercritical inert gas is introduced into the resin composition molten in an extruder, and the resin composition is discharged from a die opening under a predetermined supercritical condition (for example, when the inert gas is carbon dioxide, the temperature is 31° C. or higher and the pressure is 7.3 MPa or higher), and the resin foam sheet having small and fine cells is obtained by rapidly decompressing the pressure to atmospheric pressure and cooling. For example, when the inert gas is carbon dioxide, the temperature is 31° C. or higher and the pressure is 7.3 MPa or higher, so that the carbon dioxide can be maintained in a supercritical state, and the resin composition and the supercritical carbon dioxide are mixed uniformly.

In addition, when mixing the resin composition with the inert gas in a supercritical state, it is preferable to use two or more connected extruders (tandem extruders) so that the pressure is not released to the atmosphere and does not fall below the above pressure, and to adjust the temperature by increasing the length of the process line for mixing and extruding, thereby lowering the temperature of the mixture, etc. It is preferable that the resin composition immediately before foaming has a temperature near the pour point of the composition. By keeping the temperature low, the pressure difference before and after foaming becomes large, and many bubble growth nuclei are generated, making it possible to obtain a resin foam sheet with fine cells. In addition, after foaming, the resin composition can be cooled and solidified more quickly. Therefore, the growth of bubbles can be stopped early, making it easier to obtain a resin foam sheet with a small average cell diameter.

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 preferred because it produces a resin foam sheet with a uniform thickness. When a circular die is used, a cylindrical foam is obtained, but it can be molded into a sheet by cutting open one side. In this way, during extrusion molding, a long sheet-like foam can be continuously molded directly by selecting a T-die, or via a cylindrical foam by selecting a circular die.

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, bubble nuclei are uniformly dispersed at the molecular level, and when the pressure is released under normal pressure, foaming occurs from the inside and fine bubbles are formed. In other words, fine bubbles are formed by utilizing the difference in solubility of the resin composition under pressure. Note that when foaming, all that is required is to release the pressure; simply extruding the resin composition from the extruder reduces the pressure applied to the resin composition to approximately atmospheric pressure, eliminating the need for a pressure reducing device.

As described above, the molded resin foam sheet can be split to remove the skin layer or adjust the thickness. The thickness of the resin foam sheet after splitting is not particularly limited, but can be 0.5 mm or more.

The molded resin foam sheet can also be rolled using a heated roll. The temperature of the heated roll is not particularly limited, but it can be heated to, for example, 110 to 160°C. The thickness of the resin foam sheet after the heated roll can be 0.05 mm or more.

<<<<<Applications of resin foam sheets>>>>
The use of the resin foam sheet of the present invention is not particularly limited, but it can be used, for example, as a shock absorbing material for electronic devices such as liquid crystal panels and OLED panels, or electronic device parts installed in electronic devices, and as a seal material (gasket, etc.) for float valves that open and close flow paths in vehicle fuel gauges, drinking water tank gauges, and other precision devices that use fluids. It can also be used as a sheet that takes advantage of the heat insulating and cushioning properties of a foam, particularly for use as a resin foam sheet for cold storage or as a heat retaining agent. It can also be used as a base material (core material) for double-sided tape that is densely packed by lamination and requires high peel strength.

<Preparation of resin foam sheet>
The resin compositions of each Example and Comparative Example were prepared in the amounts shown in the table. Each resin composition was melted and prepared using a twin-screw extruder manufactured by Japan Steel Works, Ltd., and impregnated with supercritical carbon dioxide at a temperature of 31°C or higher and a pressure of 7.3 MPa or higher. The molten material was then extruded to prepare a resin foam sheet. The prepared resin foam sheet had a thickness of 2 mm and had a skin layer. The skin layer was then removed by splitting to obtain a resin foam sheet with a thickness of 1 mm, which was then rolled with a hot roll to form a resin foam sheet with a thickness of 1 mm or less, which was used as the resin foam sheet of each Example and Comparative Example. The resin foam sheet of Example 6 was prepared by rolling the resin foam sheet of Example 3 with a hot roll at 130°C.

The ingredients are listed below.
(material)
・Polyolefin resin Homopolypropylene (H-PP) MFR 0.5g/10min. (230℃, 2.16kg)
Random polypropylene (R-PP) MFR 0.5g/10min. (230°C, 2.16kg)
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 4.5g/10min. (230°C, 2.16kg)
SEBS resin 2: composition ratio styrene/ethylene-butylene ratio = 42/58, MFR 0.8g/10min. (230°C, 2.16kg)
Polymer (A)
Low density PE polymer 1
MFR 1.7g/10min. (190°C, 2.16kg)
Density 0.87g/ ^cm3
Low density PE polymer 2
MFR 0.9g/10min. (190°C, 2.16kg)
Density 0.92g/ ^cm3
The low-density PE polymer 1 and the low-density PE polymer 2 are network polymers having a crosslinked structure of R ₁ --Si--O--Si--R ₃ .
・Catalyst Metal catalyst: Mitsubishi Chemical Corporation Linkron LZ033

<Evaluation method>
(Gel Fraction)
The gel fraction of the resin foam sheets of each of the Examples and Comparative Examples was measured in accordance with the method for measuring gel content described in JIS K6796:1998 "Cross-linked polyethylene (PE-X) pipes and fittings - Estimation of degree of cross-linking by measuring gel content". The results are shown in the table.

(Measurement of density)
The density of the resin foam sheets of each of the Examples and Comparative Examples was measured in accordance with the underwater displacement method of JIS K7112:1999 "Method of measuring density and specific gravity of plastics-non-foamed plastics." The results are shown in the table.

(Tensile Modulus)
The tensile modulus of elasticity of the resin foam sheets of each of the Examples and Comparative Examples was measured in accordance with JIS K6767:1999 "Foamed plastics - Polyethylene test method." The results are shown in the table.

(Tensile elongation)
The tensile elongation of the resin foam sheets of each of the Examples and Comparative Examples was measured in accordance with JIS K6767:1999 "Foamed plastics - Polyethylene test method". The tensile elongation was evaluated according to the following criteria. The results are shown in the table.
Evaluation criteria: ◎: Tensile elongation is 150% or more; ○: Tensile elongation is 100% or more and less than 150%; △: Tensile elongation is less than 100%

(Compression hardness, flexibility evaluation)
The compression hardness of the resin foam sheets of each of the Examples and Comparative Examples was measured in accordance with JIS K6767:1999 "Foamed plastics - Polyethylene test method". The results are shown in Table 1. The flexibility evaluation can be performed, for example, according to the following criteria.
Judgment criteria: ◯: Compressive hardness is less than 0.1 MPa △: Compressive hardness is 0.1 MPa or more

(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 - Polyethylene test method". The results are shown in the table. In the table, "-" indicates that the measurement was not possible due to poor foaming.

(Evaluation of peel strength and peelability)
The resin foam sheets of each Example and Comparative Example were molded to 150 mm long x 10 mm wide, and a 25 μm thick PET film molded to 250 mm long x 20 mm wide was attached to one surface of the sheet so that the resin foam sheet did not protrude, to prepare an evaluation sample. The thickness of each resin foam sheet was about 0.1 to 2 mm. When the sheets were attached, the longitudinal end of the resin foam sheet and the longitudinal end of the PET film were attached to each other so that they were separated by 10 mm or more. Furthermore, the resin foam sheet of the evaluation sample was attached to a SUS304BA finishing plate of 300 mm long x 50 mm wide x 5 mm thick so that the entire surface of the resin foam sheet of the evaluation sample was in contact with the SUS plate. The attachment work was performed in an environment of 23°C x 50% RH, and the attachment was performed by moving a 2 kg roller back and forth once. Next, the evaluation sample was left to stand in an environment of 23°C x 50% RH for 30 minutes and aged.
The measurement was performed by fixing the PET film to the measuring device with the evaluation sample facing up. A chucking jig equipped with a load cell was used to chuck one end of the PET film in the longitudinal direction of the evaluation sample, and the chucking jig was moved approximately horizontally in the peeling direction by 180 degrees to perform a peel 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 x 50% RH, with the chucking jig moving at a speed of 1000 mm/min.
In this application, the peel strength is defined as the average stress obtained when the evaluation sample does not peel off at the interface between the evaluation sample and the adherend (PET film or SUS304BA finish plate) and the evaluation sample splits in the thickness direction (cohesive failure). The peelability evaluation was performed according to the following criteria. The results are shown in the table.
Criteria for evaluation: ⊚: peel strength is 5 N/cm or more; ◯: peel strength is 3 N/cm or more and less than 5 N/cm; Δ: peel strength is 1.5 N/cm or more and less than 3 N/cm; ×: peel strength is less than 1.5 N/cm

(Formability evaluation)
The moldability of the resin foam sheets of the Examples and Comparative Examples was evaluated by visual observation according to the following criteria. The results are shown in the table.
Judgment criteria: 〇: No problem with foam molding △: Broken bubbles, slight shrinkage, but moldable ×: Broken bubbles, shrinkage that interfere with foam molding

(Appearance Evaluation)
The appearance of the resin foam sheets of the Examples and Comparative Examples was evaluated by visual observation according to the following criteria. The results are shown in the table.
Judgment criteria: ◯: No corrugated pattern is present △: A small amount of corrugated pattern is present (to the extent that it can be ignored during use) ×: A large amount of corrugated pattern is present (to the extent that it interferes with use)

(comprehensive evaluation)
The overall evaluation of each Example and Comparative Example was performed based on the following evaluation criteria. The results are shown in the table.
Evaluation criteria: ◯: Very excellent in elongation, appearance, peel strength, etc. △: Excellent in peel strength, etc., but relatively poor in appearance ×: Poor in peel strength, elongation, appearance, etc.

(Evaluation results)
The effects of the present invention can be understood from the above results.

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

Claims (7)

A resin foam sheet obtained by foaming a resin composition including a polyolefin resin, a copolymer, and a polymer (A) having a structure represented by the following formula 1,
The resin foam sheet has a gel fraction of 10 to 45 mass % as measured in accordance with JIS K6796:1998.
(Equation 1)
R ₁ —Si—O—R ₂
In formula 1, R ₁ is a group having a hydrocarbon skeleton containing a repeating structure, and R ₂ is an alkyl group or a group having the structure of formula 2 below.
(Equation 2)
-Si- _R3
R3 in formula 2 is either linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), ethylene vinyl acetate copolymer (EVA) or polypropylene. A resin foam sheet obtained by foaming a resin composition including a polyolefin resin, a copolymer, and a polymer (A) having a structure represented by the following formula 1,
The resin foam sheet has a gel fraction of 10 to 45% by mass as measured in accordance with JIS K6796:1998,
The resin foam sheet has a density measured in accordance with JIS K7112:1999 of 130 to 900 kg/m ³ and
The resin composition is characterized in that the blending amount of the polymer (A) is 20 to 50 parts by mass when the blending amount of the polyolefin resin is 100 parts by mass.
(Equation 1)
R ₁ -Si-O-R ₂
R in Formula 1 ₁ is a group having a hydrocarbon skeleton containing a repeating structure, R ₂ is an alkyl group or a group having the structure of formula 2 below.
(Equation 2)
-Si-R ₃
R in Formula 2 ₃ is a group having a hydrocarbon skeleton containing a repeating structure. A resin foam sheet obtained by foaming a resin composition including a polyolefin resin, a copolymer, and a polymer (A) having a structure represented by the following formula 1,
The resin foam sheet has a gel fraction of 10 to 45% by mass as measured in accordance with JIS K6796:1998,
The resin foam sheet has a density of 650 to 900 kg/m as measured in accordance with JIS K7112:1999. ³ A resin foam sheet, comprising:
(Equation 1)
R ₁ -Si-O-R ₂
R in Formula 1 ₁ is a group having a hydrocarbon skeleton containing a repeating structure, R ₂ is an alkyl group or a group having the structure of formula 2 below.
(Equation 2)
-Si-R ₃
R in Formula 2 ₃ is a group having a hydrocarbon skeleton containing a repeating structure. A resin foam sheet obtained by supercritical foaming a resin composition including a polyolefin resin, a copolymer, and a polymer (A) having a structure represented by the following formula 1,
The resin foam sheet has a gel fraction of 10 to 45 mass % as measured in accordance with JIS K6796:1998.
(Equation 1)
R ₁ -Si-O-R ₂
R in Formula 1 ₁ is a group having a hydrocarbon skeleton containing a repeating structure, R ₂ is an alkyl group or a group having the structure of formula 2 below.
(Equation 2)
-Si-R ₃
R in Formula 2 ₃ is a group having a hydrocarbon skeleton containing a repeating structure. A resin foam sheet obtained by foaming a resin composition including a polyolefin resin, a copolymer, and a polymer (A) having a structure represented by the following formula 1,
The resin foam sheet has a gel fraction of 10 to 45% by mass as measured in accordance with JIS K6796:1998,
The polymer (A) has a melt mass flow rate of 0.1 to 1.7 g/10 min. (190° C., 2.16 kgf).
(Equation 1)
R ₁ -Si-O-R ₂
R in Formula 1 ₁ is a group having a hydrocarbon skeleton containing a repeating structure, R ₂ is an alkyl group or a group having the structure of formula 2 below.
(Equation 2)
-Si-R ₃
R in Formula 2 ₃ is a group having a hydrocarbon skeleton containing a repeating structure. A resin foam sheet obtained by foaming a resin composition including a polyolefin resin, a copolymer, and a polymer (A) having a structure represented by the following formula 1,
The resin foam sheet has a gel fraction of 10 to 45% by mass as measured in accordance with JIS K6796:1998,
The resin foam sheet is characterized in that the copolymer is at least one selected from ethylene-acrylic acid copolymer (EAA), ethylene-methyl acrylate copolymer (EMA), ethylene-methyl methacrylate copolymer (EMMA), copolymer of ethylene and methacrylic acid (EMAA), ethylene-propylene-diene rubber (EPDM), 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), polyamide copolymer, thermoplastic polyurethane (TPU) copolymer, and acrylic copolymer.
(Equation 1)
R ₁ -Si-O-R ₂
R in Formula 1 ₁ is a group having a hydrocarbon skeleton containing a repeating structure, R ₂ is an alkyl group or a group having the structure of formula 2 below.
(Equation 2)
-Si-R ₃
R in Formula 2 ₃ is a group having a hydrocarbon skeleton containing a repeating structure. A method for producing a resin foam sheet, comprising:
The method for producing the resin foam sheet includes:
A mixing step of dry-blending a polyolefin resin, a copolymer, and a polymer (A) containing a plurality of structures represented by the following formula 1 to form a resin composition;
and a foaming step of subjecting the resin composition to supercritical foaming to obtain a resin foam sheet,
A method for producing a resin foam sheet, the method not including a step of contacting the resin composition or the resin foam sheet with water, hot water, or water vapor.
(Equation 1)
R ₁ —Si—O—R ₂
In formula 1, R ₁ is a group having a hydrocarbon skeleton containing a repeating structure, and R ₂ is an alkyl group or a group having the structure of formula 2 below.
(Equation 2)
-Si- _R3
R3 in formula 2 is a group having a hydrocarbon skeleton containing a repeating structure.

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