Crosslinking and foaming resin composition

Abstract

To provide a resin composition for crosslinking foaming which enables production of a crosslinked foam excellent in resilience, in a state where strength equivalent to a conventional crosslinked foam is maintained.SOLUTION: A resin composition for crosslinking foaming contains a thermoplastic resin, a crosslinking agent, and a foaming agent, further contains an ethylene-propylene-diene rubber having an ethylene content of less than 70 mass%, and has a content of the ethylene-propylene-diene rubber with respect to the total of the thermoplastic resin and the ethylene-propylene-diene rubber of 5 mass% or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a crosslinkable and foamable resin composition for forming a crosslinked foam used in shoe soles. [Background technology]

[0002] In shoes such as sports shoes, foam is attached to the middle part (midsole or insole) of the shoe to improve walking comfort and wearing comfort, reduce fatigue, and prevent injuries.

[0003] As such a foam, for example, a crosslinked foam formed from a polymer such as a styrene-based thermoplastic elastomer has been proposed, which has a spin-spin relaxation time in pulse NMR (23°C) that satisfies a predetermined condition, and a complex modulus measured in dynamic viscoelasticity measurement under conditions of a frequency of 1 Hz, a strain of 0.025%, and a heating rate of 2°C / min that satisfies a predetermined condition. It is also described that such a configuration can provide a crosslinked foam with low specific gravity and excellent heat resistance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5719980 Summary of the Invention [Problem to be solved by the invention]

[0005] Here, sports shoes and the like are expected to be used not only at room temperature but also at high temperatures and to undergo heating steps in the bonding process, and therefore heat resistance is required. However, the above-mentioned conventional crosslinked foams have had the problem that when the composition or blending amount of the polymer is adjusted in order to improve the heat resistance, desired physical properties such as strength and rebound resilience cannot be obtained.

[0006] Therefore, the present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a cross-linking and foaming resin composition that can give a cross-linked foam that has excellent resilience while maintaining strength equivalent to that of conventional cross-linked foams. [Means for solving the problem]

[0007] In order to achieve the above object, the cross-linking and foaming resin composition of the present invention is a cross-linking and foaming resin composition containing a thermoplastic resin, a cross-linking agent, and a foaming agent, characterized in that it further contains ethylene-propylene-diene rubber having an ethylene content of less than 70 mass%, and the content of the ethylene-propylene-diene rubber relative to the total of the thermoplastic resin and the ethylene-propylene-diene rubber is 5 mass% or more. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a crosslinking and foaming resin composition that can give a crosslinked foam that has excellent resilience while maintaining strength equivalent to that of conventional crosslinked foams. DETAILED DESCRIPTION OF THE INVENTION

[0009] Preferred embodiments of the present invention will be described below.

[0010] The cross-linking and foaming resin composition of the present invention contains a thermoplastic resin, ethylene-propylene-diene rubber (hereinafter sometimes referred to as "EPDM"), a cross-linking agent, and a foaming agent, and is used to form a cross-linked foam, which is a foam for shoe soles, by cross-linking and foaming the cross-linking and foaming resin composition of the present invention.

[0011] <Thermoplastic resin> Examples of the thermoplastic resin of the present invention include α-olefin copolymers, α-olefin block copolymers, ethylene-vinyl acetate copolymers, polyamides, polyether block amides, etc. These may be used alone or in combination of two or more.

[0012] Among these, it is preferable to use at least one selected from the group consisting of α-olefin copolymers, α-olefin block copolymers, and ethylene-vinyl acetate copolymers, from the viewpoint that the strength and impact resilience of the crosslinked foam can be easily adjusted within appropriate ranges.

[0013] The content of the thermoplastic resin in the entire crosslinking and foaming resin composition is preferably 50% by mass to 95% by mass, and more preferably 60% by mass to 90% by mass, because if the content is less than 50% by mass, the amount of components other than the thermoplastic resin will be large, which may result in an increased viscosity and insufficient foaming, whereas if the content is more than 95% by mass, there may be an increased amount of foaming agent, which may result in insufficient foaming.

[0014] In addition, in a base composition comprising a thermoplastic resin and an ethylene-propylene-diene rubber, it is preferable that the hardness of only the thermoplastic resin calculated by the following formula (1) is 86 or less.

[0015] [Number 1] Hardness when the thermoplastic resin alone in the base composition is taken as 100% = {(Hardness of the first thermoplastic resin × Content of the first thermoplastic resin in the base composition) + (Hardness of the second thermoplastic resin × Content of the second thermoplastic resin in the base composition) + + (Hardness of the nth thermoplastic resin × Content of the nth thermoplastic resin in the base composition)} / {1 - (Content of ethylene-propylene-diene rubber in the base composition)} (1)

[0016] By setting the hardness of the thermoplastic resin alone to 86 or less, the rubber elasticity of the crosslinked foam can be improved, making it possible to obtain a crosslinked foam with excellent resilience.

[0017] The "hardness" referred to here refers to the hardness measured using a type A durometer in accordance with JIS K 6253.

[0018] <Ethylene-propylene-diene rubber> The ethylene-propylene-diene rubber used in the present invention has an ethylene content of less than 70% by mass, because when the ethylene content is less than 70% by mass, the amount of ethylene as a resin component decreases, causing the ethylene-propylene-diene rubber to have a lower crystallinity and become amorphous, thereby enabling the resilience of the crosslinked foam to be improved.

[0019] The diene monomer for crosslinking used in the ethylene-propylene-diene rubber is not particularly limited, and examples thereof include ethylidene norbornene (ENB), dicyclopentadiene (DCPD), 1,4-hexadiene (1,4-HD), and the like.

[0020] From the viewpoint of improving crosslinkability, the content of the diene monomer for crosslinking relative to the entire ethylene-propylene-diene rubber is preferably 0.5% by mass to 14% by mass.

[0021] The ethylene-propylene-diene rubber preferably has a Mooney viscosity (ML1+4, 125°C) of 20 to 85. When the Mooney viscosity is 20 or more, the strength of the crosslinked foam is improved, and when the Mooney viscosity is 85 or less, the crosslinked foam can be prevented from becoming too hard.

[0022] The term "Mooney viscosity" used herein refers to the viscosity measured in accordance with JIS K 6300-1 (2001).

[0023] The cross-linking and foaming resin composition of the present invention is characterized in that the content of the ethylene-propylene-diene rubber relative to the total of the thermoplastic resin and the ethylene-propylene-diene rubber is 5% by mass or more.

[0024] More specifically, for example, when the total mass of the thermoplastic resin and the ethylene-propylene-diene rubber is 100 parts by mass (for example, when the thermoplastic resin is 90 parts by mass and the ethylene-propylene-diene rubber is 10 parts by mass), the cross-linking and foaming resin composition of the present invention contains 5% by mass or more (i.e., 10% by mass) of the ethylene-propylene-diene rubber relative to the total mass of the thermoplastic resin and the ethylene-propylene-diene rubber.

[0025] Such a configuration makes it possible to improve the strength of the crosslinked foam, and therefore makes it possible to provide a crosslinking and foaming resin composition that can give a crosslinked foam that has excellent resilience while maintaining strength equivalent to that of conventional crosslinked foams.

[0026] From the viewpoint of maintaining the improved strength of the crosslinked foam, the content of the ethylene-propylene-diene rubber relative to the total of the thermoplastic resin and the ethylene-propylene-diene rubber is preferably 30% by mass or less.

[0027] <Crosslinking agent> The crosslinking agent is not particularly limited, and can be an organic peroxide that promotes sulfur or peroxide crosslinking, which is a common crosslinking agent for foamable resin compositions. Examples of organic peroxides include dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexyne-3, 1,3-bis(t-butylperoxyisopropyl)benzene, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(t-butylperoxy)valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, t-butyl peroxybenzoate, t-butyl perbenzoate, t-butylperoxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, and t-butylcumyl peroxide. These may be used alone or in combination of two or more.

[0028] The content of the crosslinking agent in the crosslinking and foaming resin composition is preferably 0.05% by mass to 3.0% by mass, and more preferably 0.1% by mass to 1.0% by mass, based on the total mass of the crosslinking and foaming resin composition. This is because if the content is less than 0.05% by mass, the crosslinking reaction may be insufficient, resulting in poor foaming and reduced impact resilience, while if the content is more than 3.0% by mass, excessive crosslinking may occur, resulting in insufficient foaming.

[0029] <Foaming agent> The foaming agent is not particularly limited as long as it generates a gas necessary for foaming the crosslinking and foaming resin composition upon heating. More specific examples include N,N'-dinitrosopentamethylenetetramine (DNPT), 4,4'-oxybis(benzenesulfonylhydrazide) (OBSH), azodicarbonamide (ADCA), sodium hydrogencarbonate, sodium bicarbonate, ammonium bicarbonate, sodium carbonate, ammonium carbonate, azobisisobutyronitrile, and barium azodicarboxylate. These may be used alone or in combination of two or more.

[0030] The content of the foaming agent in the crosslinking and foaming resin composition is preferably 1.0 to 15% by mass, and more preferably 1.5 to 10% by mass, based on the total mass of the crosslinking and foaming resin composition. This is because if the content is less than 1.0% by mass, stable foaming may not be possible, and if the content is more than 15% by mass, excessive foaming may occur, resulting in variations in the foam cell diameters on the surface and inside.

[0031] Furthermore, a crosslinked foam can be obtained by adding a crosslinking aid, a foaming aid, etc. to the crosslinking and foaming resin composition of the present invention and crosslinking and foaming it under predetermined conditions.

[0032] <Crosslinking aid> The crosslinking aid does not need to be particularly limited, and examples thereof include divinylbenzene, trimethylolpropane trimethacrylate, 1,6-hexanediol methacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol methacrylate, trimellitic acid triallyl ester, triallyl isocyanurate, neopentyl glycol dimethacrylate, 1,2,4-benzenetricarboxylic acid triallyl ester, tricyclodecane dimethacrylate, polyethylene glycol diacrylate, etc. These may be used alone or in combination of two or more.

[0033] The content of the cross-linking aid in the cross-linking foamable resin composition is preferably 0.01% by mass to 5% by mass, and more preferably 0.05% by mass to 1% by mass, based on the total amount of the cross-linking foamable resin composition. This is because if it is less than 0.01% by mass, cross-linking may not proceed sufficiently, resulting in a disadvantage of reduced impact resilience, and if it is more than 5% by mass, the specific gravity of the cross-linking foamable resin composition increases, making it difficult to reduce the weight of the product.

[0034] <Foaming aid> The foaming aid is not particularly limited, and examples thereof include urea compounds, zinc compounds such as zinc oxide, etc. These may be used alone or in combination of two or more.

[0035] The content of the foaming aid in the crosslinking and foaming resin composition is preferably 0.1% by mass to 10% by mass, and more preferably 0.5% by mass to 8.5% by mass, based on the total mass of the crosslinking and foaming resin composition. The foaming aid is typically added in an amount equal to that of the foaming agent. If the amount of foaming aid added is less than that of the foaming agent, some foaming agents may generate formaldehyde, etc., and therefore, the amount must be adjusted appropriately depending on the amount of foaming agent added.

[0036] The crosslinking and foaming resin composition of the present invention may further contain various additives, such as fatty acids and fatty acid esters, if necessary.

[0037] <Fatty acid> As the fatty acid, stearic acid, lauric acid, and myristic acid are used, and these may be used alone or in combination of two or more.

[0038] The use of these fatty acids can cause ionic decomposition of the crosslinking agent, thereby suppressing excessive crosslinking reaction, thereby improving the heat resistance of the crosslinked foam formed from the crosslinkable foaming resin composition of the present invention.

[0039] <Fatty acid ester> The fatty acid esters used in the present invention include polyhydric alcohol fatty acid esters (i.e., esters obtained by esterifying a polyhydric alcohol with a fatty acid, and having a structure in which at least one hydroxyl group of the polyhydric alcohol is esterified) and higher fatty acid esters (esters of saturated fatty acids having 10 to 30 carbon atoms), and these can be used alone or in combination of two or more.

[0040] Examples of polyhydric alcohol fatty acid esters include pentaerythrityl tetrastearate, which is a tetraester of stearic acid and pentaerythritol, and pentaerythrityl tetrapalmitate, which is a tetraester of palmitic acid and pentaerythritol.

[0041] Examples of higher fatty acid esters include the above-mentioned esters of stearic acid, lauric acid, myristic acid, and the like.

[0042] Examples of polyhydric alcohol fatty acid esters include commercially available products such as Struktol WB222 manufactured by S&S Japan Co., Ltd. Examples of higher fatty acid esters include commercially available products such as Struktol WB212 manufactured by S&S Japan Co., Ltd.

[0043] Furthermore, by using these fatty acid esters, the fatty acid esters are chemically adsorbed to the peroxides, and excessive crosslinking reaction can be suppressed, thereby improving the heat resistance of the crosslinked foam formed from the crosslinkable foaming resin composition of the present invention.

[0044] Furthermore, from the viewpoint of reliably obtaining a crosslinked foam having excellent heat resistance, the total content of the fatty acid and the fatty acid ester is preferably 0.5 to 4.0% by mass relative to 100 parts by mass of the thermoplastic resin.

[0045] Furthermore, when a fatty acid and a fatty acid ester are used in combination, the content of the fatty acid is preferably 0.25 to 1.0 mass% relative to 100 parts by mass of the thermoplastic resin, and the content of the fatty acid ester is preferably 0.25 to 3.0 mass% relative to 100 parts by mass of the thermoplastic resin.

[0046] Next, a method for producing a crosslinked foam using the crosslinkable foaming resin composition of the present invention will be described. The method for producing a crosslinked foam of the present invention includes a kneading step for preparing a crosslinkable foaming resin composition, and a foam-molding step for foaming the crosslinkable foaming resin composition and molding it into a desired shape.

[0047] (Kneading process) First, raw materials such as a thermoplastic resin base material, an ethylene-propylene-diene rubber, a fatty acid, a fatty acid ester, a crosslinking agent, and a foaming agent are charged into a kneader and kneaded to prepare a crosslinkable and foamable resin composition.

[0048] As the kneading machine, a mixing roll, a calendar roll, a Banbury mixer, a kneader, etc. can be used.

[0049] Then, for example, a thermoplastic resin, ethylene-propylene-diene rubber, fatty acid, fatty acid ester, crosslinking aid, crosslinking agent, foaming aid, and foaming agent are added in this order to a roll set to a predetermined temperature (for example, a surface temperature of 100 to 120°C) and kneaded, and then preforming such as sheeting or pelletizing is performed.

[0050] Alternatively, the process may be carried out in stages using a plurality of kneaders. For example, a thermoplastic resin, an ethylene-propylene-diene rubber, a fatty acid, a fatty acid ester, and a foaming aid are charged into a kneader and kneaded, and the kneaded composition is then transferred to a roll, and a crosslinking agent and a foaming agent are charged into the roll and kneaded, followed by preforming such as sheeting or pelletizing.

[0051] (Foam molding process) Next, the cross-linking and foaming resin composition obtained in the kneading step is filled into a mold and subjected to a heat treatment to allow foaming by the foaming agent to proceed, followed by a molding treatment and a demolding treatment to produce a cross-linking and foaming resin composition having a desired shape.

[0052] The heating temperature in the heat treatment varies depending on the types of foaming agent and foaming assistant, but is usually at a temperature equal to or higher than the decomposition temperature of the foaming agent used (for example, 120 to 180° C.) Alternatively, the cross-linking and foaming resin composition may be filled into a mold and heat-treated under pressure, or may be heated under normal pressure to promote decomposition of the foaming agent.

[0053] In this manner, the crosslinked foam of the present invention can be produced.

[0054] From the viewpoint of use in shoes, the specific gravity of the crosslinked foam of the present invention is 0.6 g / cm 3 The following is preferable, especially when used in the midsole of shoes: 0.4 g / cm 3 The following is preferred: [Example]

[0055] The present invention will be described below based on examples. However, the present invention is not limited to these examples, and these examples can be modified or changed based on the spirit of the present invention, and such modifications are not excluded from the scope of the invention.

[0056] (Examples 1 to 15 and Comparative Examples 1 to 6) <Production of crosslinked foam> Crosslinked foams of Examples 1 to 15 and Comparative Examples 1 to 6 having the compositions shown in Tables 1 and 2 (numbers indicate parts by mass of each component) were produced by the following production method.

[0057] (Kneading process) First, the thermoplastic resin, ethylene-propylene-diene rubber, foaming aid 2 (zinc oxide), fatty acid, fatty acid ester, and crosslinking aid shown in Tables 1 and 2 were charged into a kneader set at 160°C, and the raw materials were kneaded for 8 to 12 minutes. Next, the kneaded composition was charged into a 10-inch open roll (temperature: 100 to 120°C), and then the crosslinking agent, foaming aid 1, and foaming agent shown in Tables 1 and 2 were added, and the raw materials were kneaded for 10 minutes to produce a crosslinkable and foamable resin composition.

[0058] (Foam molding process) First, 182 g of the prepared crosslinkable foamable resin composition was filled into a mold (length: 155 mm, width: 125 mm, height: 10 mm) and press-molded under conditions of 165°C and 20 MPa until foaming was uniformly achieved to the interior, yielding a primary foam. Next, the primary foam was cut into a size of 200 mm length x 124 mm width x 16 mm height, and compression was initiated at 165°C so that the cut primary foam had a height of 10 mm. Cooling was then initiated immediately. While maintaining the compressed state, the secondary foam was cooled and pressed to room temperature (23°C) to yield a secondary foam. These secondary foams were used as the crosslinkable foams of Examples 1 to 15 and Comparative Examples 1 to 6.

[0059] <Calculating the hardness of thermoplastic resin> The hardness was calculated using the above formula (1) when the thermoplastic resin alone in the base composition was taken as 100%. The results are shown in Table 1.

[0060] In Example 1, from the above formula (1), (Hardness of Thermoplastic Resin 1 × Content Ratio of Thermoplastic Resin 1 in the Base Composition) + (Hardness of Thermoplastic Resin 2 × Content Ratio of Thermoplastic Resin 2 in the Base Composition) + (Hardness of Thermoplastic Resin 3 × Content Ratio of Thermoplastic Resin 3 in the Base Composition) / {1 - (Content Ratio of EPDM in the Base Composition)} = {(87 × 0.6) + (83 × 0.1) + (84 × 0.25)} / (1 - 0.05) = 85.8.

[0061] <Measurement of Specific Gravity> The specific gravity of the produced crosslinked foam was measured in accordance with "Method A (Water Substitution Method)" in JIS K 7112:1999 "Plastics - Methods for Measuring the Density and Specific Gravity of Non - Foamed Plastics". More specifically, a foam sample (length: 20 ± 1 mm, width: 15 ± 1 mm, thickness: 10 ± 1 mm) was prepared, and using an electronic specific gravity meter (manufactured by ALFA MIRAGE CO,LTD, product name: MDS - 300), under the condition that the measurement temperature was 23°C, the specific gravity [g / cm 3 of each foam sample was calculated by the following formula (2). The above results are shown in Tables 1 - 2.

[0062] [Equation 2] D [g / cm 3 = W1 / (W1 - W2) (2)

[0063] In the formula, D represents the specific gravity, W1 represents the weight in air, and W2 represents the weight in water.

[0064] <Measurement of C Hardness> The hardness of the produced crosslinked foam was measured in accordance with JIS K 7312. More specifically, a foam sample (length: 199 mm, width: 124 mm, thickness: 10 mm) was prepared as a test piece, and using an Asker C type hardness meter manufactured by Polymer Instrument Co., Ltd., after pressing it with a load of about 10 N (9.8 N) under the condition of 23°C, the scale of the instantaneous maximum value was read to obtain the C hardness. The above results are shown in Tables 1 - 2.

[0065] <Measurement of Split Tear> A foam sample (length: 10 mm, width: 100 mm, thickness: 10 mm) was prepared as a test piece from the produced crosslinked foam, a 20 mm slit was made in the center of the test piece, it was clamped with a chuck, and measurement was carried out at 100 mm / min using a universal testing machine (manufactured by Instron Japan Company Limited, trade name: INSTRON3365). Values ​​were recorded at 10 mm intervals on the test piece, and the average value of five points was taken as the split tear [N / cm].

[0066] When the split tear was 17 N / cm or more, the strength of the crosslinked foam was judged to be improved, and when the split tear was less than 17 N / cm, the strength of the crosslinked foam was judged to be poor. The results are shown in Tables 1 and 2.

[0067] <Measurement of rebound resilience> The rebound resilience of the crosslinked foam was measured according to ASTM-D 2632. More specifically, a foam sample (thickness: 10±1 mm) was prepared, and a GOTECH VERTICAL REBOUND RESILIENCE TESTER_GT-7042-V was used to drop a metal plunger seven times at 5-second intervals at 23°C. The pointer [%] was read at the point where the metal plunger came to rest after rebounding (rebound height) for the last five times, and the average of the read values ​​was taken as the rebound resilience [%].

[0068] When the resilience modulus was 65% or more, the crosslinked foam was judged to have improved resilience, and when the resilience modulus was less than 65%, the crosslinked foam was judged to have poor resilience. The results are shown in Tables 1 and 2.

[0069] <Measurement of compression set> The compression set of the crosslinked foams was measured by the compression set B method in accordance with ASTM-D395. More specifically, a foam sample (length: 50 mm, width: 50 mm, thickness: 10 mm) was prepared as a test piece. Using a constant-load compression tester (GOTECH, product name: Compression and Deformation Tester_GT-7049) specified in ASTM-D395, the sample was compressed to 50% of its thickness (5 mm) at ambient temperature (50±3°C). After 6 hours, the pressure was released and the specimen was allowed to stand at 23°C for 1 hour. The thickness (h1) of the specimen was measured, and the compression set (C) of the foam sample was calculated using the thickness (h0) of the specimen before compression and the thickness (h2) of the spacer using the following formula (3). The results are shown in Tables 1 and 2.

[0070] [Number 3] C[%]=[(h0-h1) / (h0-h2)]×100 (3)

[0071] <Measurement of heat shrinkage resistance> First, a test piece measuring 200 mm x 124 mm x 10 mm was prepared. A line parallel to the long side of the test piece was drawn 10 mm inward from the long side, and dots were marked on this line at 150 mm intervals. Next, the test piece was placed in a thermostatic chamber at 70°C for 2 hours, and then placed in a thermostatic chamber at 23°C for 1 hour. Next, the distance between the dots on the test piece that had shrunk from 150 mm (i.e., the amount of shrinkage) was measured, and the percentage of the shrinkage relative to the initial spacing was taken as the thermal shrinkage rate [%]. The results are shown in Tables 1 and 2.

[0072] [Table 1]

[0073] [Table 2]

[0074] The materials used to prepare the crosslinked foam are listed below.

[0075] (1) Thermoplastic resin 1: TAFMER DF-810 (α-olefin copolymer, hardness: 87, MFR (190°C): 1.2 g / 10 min, density: 0.885 g / cm 3 , melting point: 66°C, manufactured by Mitsui Chemicals, Inc.) (2) Thermoplastic resin 2: INFUSE 9530 (α-olefin block copolymer, hardness: 83, MFR (190°C): 5.0 g / 10 min, density: 0.887 g / cm 3 , melting point: 119°C, manufactured by Dow Chemical Co.) (3) Thermoplastic resin 3: UE659 (ethylene vinyl acetate copolymer, hardness: 84, MRF (190°C): 2.0 g / 10 min, density: 0.947 g / cm 3 , melting point: 77℃, VA content: 25%, EVATHENE (4) Thermoplastic resin 4: TUFTEC P1083 (partially hydrogenated block copolymer of styrene, butadiene, butylene, and styrene, hardness: 56, MFR (190°C): 3.0 g / 10 min, density: 0.89 g / cm 3 , manufactured by Asahi Kasei Corporation) (5) EPDM1: NORDEL 4770P (ethylene-propylene-diene rubber, Mooney viscosity (125°C): 70, ethylene content: 70%, ENB content: 4.9%, manufactured by Dow Chemical Co.) (6) EPDM2: NORDEL 5565 (ethylene-propylene-diene rubber, Mooney viscosity (125°C): 65, ethylene content: 50%, ENB content: 7.5%, manufactured by Dow Chemical Co.) (7) EPDM3: NORDEL 4520 (ethylene-propylene-diene rubber, Mooney viscosity (125°C): 20, ethylene content: 50%, ENB content: 4.9%, manufactured by Dow Chemical Co.) (8) EPDM4: NORDEL 4570 (ethylene-propylene-diene rubber, Mooney viscosity (125°C): 70, ethylene content: 50%, ENB content: 4.9%, manufactured by Dow Chemical Co.) (9) EPDM5: NORDEL 6565XFC (ethylene-propylene-diene rubber, Mooney viscosity (125°C): 65, ethylene content: 55%, ENB content: 8.5%, manufactured by Dow Chemical Co.) (10) EPDM6: NORDEL 4785M (ethylene-propylene-diene rubber, Mooney viscosity (125°C): 85, ethylene content: 68%, ENB content: 4.9%, manufactured by Dow Chemical Co.) (11) EPDM7: ESPRENE E522 (ethylene-propylene-diene rubber, Mooney viscosity (125°C): 85, ethylene content: 55%, ENB content: 4.0%, manufactured by Sumitomo Chemical Co., Ltd.) (12) EPDM8: Keltan 6950C (ethylene-propylene-diene rubber, Mooney viscosity (125°C): 65, ethylene content: 44%, ENB content: 9.0%, manufactured by ARLANXEO Co., Ltd.) (13) Fatty acid: Camellia stearate beads (stearic acid, manufactured by NOF Corporation) (14) Fatty acid ester: Struktol WB222 (polyhydric alcohol fatty acid ester, manufactured by S&S Japan Co., Ltd.) (15) Crosslinking coagent: TAC / GR70 (triallyl cyanurate, manufactured by KETTLITZ) (16) Crosslinking agent: Percumyl D (dicumyl peroxide, manufactured by NOF Corporation) (17) Foaming agent: Cellular D (N,N'-dinitrosopentamethylenetetramine, manufactured by Eiwa Chemical Industry Co., Ltd.) (18) Foaming aid 1: Cell Paste 101 (urea, manufactured by Eiwa Chemical Industry Co., Ltd.) (19) Foaming aid 2: Activated zinc oxide AZO (zinc oxide, manufactured by Seido Chemical Industry Co., Ltd.)

[0076] As shown in Table 1, the crosslinking foaming resin compositions of Examples 1 to 15 contain ethylene-propylene-diene rubber with an ethylene content of less than 70% by mass, and the content of ethylene-propylene-diene rubber relative to the total of the thermoplastic resin and ethylene-propylene-diene rubber is 5% by mass or more. Therefore, it is clear that the resilience of the crosslinking foams can be improved while maintaining strength equal to or greater than that of the crosslinking foams formed from the crosslinking foaming resin compositions of Comparative Examples 1 to 3, which do not contain ethylene-propylene-diene rubber.

[0077] On the other hand, in Comparative Examples 1 to 3, since the ethylene-propylene-diene rubber having an ethylene content of less than 70% by mass is not contained, it is clear that the resilience of the crosslinked foam is poor.

[0078] Furthermore, in Comparative Examples 4 to 6, the ethylene content of the ethylene-propylene-diene rubber was 70% by mass, and therefore the crosslinked foams had poor resilience. [Industrial Applicability]

[0079] As described above, the present invention is particularly useful for a crosslinkable and foamable resin composition for forming a crosslinked foam used in shoe soles.

Claims

1. A crosslinking and foaming resin composition containing a thermoplastic resin, a crosslinking agent, and a foaming agent, Further containing an ethylene-propylene-diene rubber having an ethylene content of less than 70% by mass, the content of the ethylene-propylene-diene rubber relative to the total of the thermoplastic resin and the ethylene-propylene-diene rubber is 5% by mass or more, the thermoplastic resin is at least one selected from the group consisting of an α-olefin copolymer, an α-olefin block copolymer, and an ethylene-vinyl acetate copolymer; Further containing a fatty acid and a fatty acid ester, A cross-linking and foaming resin composition, characterized in that the total content of the fatty acid and the fatty acid ester is 0.5% by mass to 4.0% by mass relative to 100 parts by mass of the thermoplastic resin.

2. 2. The cross-linking foamable resin composition according to claim 1, wherein in a base composition comprising the thermoplastic resin and the ethylene-propylene-diene rubber, the hardness of the thermoplastic resin alone calculated by the following formula (1) is 86 or less: [Equation 1] Hardness in the base composition when the thermoplastic resin alone is taken as 100% = {(Hardness of the first thermoplastic resin × Content of the first thermoplastic resin in the base composition) + (Hardness of the second thermoplastic resin × Content of the second thermoplastic resin in the base composition) + ... + (Hardness of the nth thermoplastic resin × Content of the nth thermoplastic resin in the base composition)} / {1 - (Content of ethylene-propylene-diene rubber in the base composition)} (1)

3. 3. The cross-linking and foaming resin composition according to claim 1, wherein the content of the ethylene-propylene-diene rubber relative to the total of the thermoplastic resin and the ethylene-propylene-diene rubber is 30 mass% or less.

4. A crosslinked foam formed from the crosslinkable foaming resin composition according to any one of claims 1 to 3.

5. Specific gravity is 0.6 g / cm ３ The crosslinked foam according to claim 4, characterized in that:

6. 6. The crosslinked foam according to claim 4, which is used for a midsole of a shoe.

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