Foam, shoe sole, and method for producing foam

Abstract

To provide a foam which exhibits excellent rebound resilience, durability, and long-term durability even with reduced weight.SOLUTION: A foam of a resin composition containing a foamable polymer, wherein the foamable polymer contains (A) a conjugated diene-based polymer including conjugated diene monomer units and vinyl aromatic monomer units, a content of the vinyl aromatic monomer units in the (A) component being 5 to 80 mass%, and the conjugated diene monomer units in the (A) component being hydrogenated.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a foam, a shoe sole, and a method for making the foam. [Background technology]

[0002] In recent years, foams have attracted attention from the viewpoint of reducing the weight of resin compositions. In particular, crosslinked foams, as lightweight and high mechanical strength materials, are widely used in automobile parts, construction parts, various packaging materials, daily necessities, etc. In addition, foams have traditionally been used as materials for shoe soles, and are applied to midsoles, outsoles, insoles, etc. In particular, with the recent increase in demand for running, there is a demand for midsoles that are lighter, have high resilience, and have high mechanical strength.

[0003] Ethylene-vinyl acetate copolymer (EVA) is a well-known foam material typically used in shoe soles, but it has issues such as low resilience, high specific gravity, large compression set, and a deterioration in mechanical strength over time due to its light weight.

[0004] To address the above-mentioned issues, various materials have been investigated. For example, Patent Document 1 discloses a crosslinked foam obtained by crosslinking and foaming a resin composition containing an ethylene-α-olefin copolymer and a styrene block copolymer to which EVA has been added. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2005 / 000958 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the crosslinked foam disclosed in Patent Document 1 has a problem in that there is still room for improvement in terms of the balance of various physical properties, particularly in terms of resilience and durability for providing the same feeling of use as immediately after use even after prolonged use.

[0007] In view of the above-mentioned problems of the prior art, an object of the present invention is to provide a foam that is lightweight yet has excellent resilience and durability. [Means for solving the problem]

[0008] As a result of extensive research into solving the problems of the conventional techniques described above, the present inventors have found that the problems can be solved by a foam of a resin composition containing a conjugated diene-based polymer having a specific structure, and have thus completed the present invention. That is, the present invention is as follows.

[0009] [1] A foam of a resin composition containing a foamable polymer, The foamable polymer (A) contains a conjugated diene polymer containing a conjugated diene monomer unit and a vinyl aromatic monomer unit, the content of vinyl aromatic monomer units in the component (A) is 5 to 80 mass %, The conjugated diene monomer units in the component (A) are hydrogenated. Foam. [2] the foam is a foam of a blowing agent mixture containing at least the component (A) and a blowing agent, The foaming agent is a physical foaming agent. The foam described in [1] above. [3] the hydrogenation rate of 1,2-vinyl bonds and 3,4-vinyl bonds in the conjugated diene monomer units in the component (A) is 80% or more; The foam according to [1] or [2] above. [4] The hydrogenation rate of the conjugated diene monomer units in the component (A) is 60 to 90 mass%. The foam according to any one of [1] to [3] above. [5] Specific gravity is 0.15 or less, The foam according to any one of [1] to [4] above. [6] The foam cell size is 50 μm or more. The foam according to any one of [1] to [5] above. [7] The resin composition further comprising at least one selected from the group consisting of ethylene-based polymers, ethylene-polar monomer copolymers, polyamide-based polymers, polyester-based polymers, and polyurethane-based polymers; The foam according to any one of [1] to [6] above. [8] It is a crosslinked body, The foam according to any one of [1] to [7] above. [9] The peak top molecular weight of the component (A) is 50,000 to 500,000. The foam according to any one of [1] to [8].

[10] The gas phase of the foam is nitrogen and / or carbon dioxide; The foam according to any one of [1] to [9] above.

[11] the total amount of 1,2-vinyl bonds and 3,4-vinyl bonds in the conjugated diene monomer units in the component (A) is 10 to 60 mass%; The foam according to any one of [1] to

[10] above.

[12] The content of the component (A) is 5 to 70 parts by mass relative to 100 parts by mass of the expandable polymer. The foam according to any one of [1] to

[11] .

[13] A shoe sole comprising the foam described in any one of [1] to

[12] .

[14] Any one selected from the group consisting of a midsole, an insole, and a unisole. The sole described in

[13] above.

[15] (A) a step (a) of kneading a resin composition containing a conjugated diene polymer containing a conjugated diene monomer unit and a vinyl aromatic monomer unit to obtain a kneaded product; a step (b) of molding the kneaded mixture to obtain a molded body; a step (c) of mixing the kneaded product or the molded product with a foaming agent and / or impregnating the kneaded product or the molded product with a foaming agent to obtain a foaming agent mixture; (d) foaming the foaming agent mixture by reducing pressure and / or increasing temperature; have, A method for producing a foam.

[16] The step (a) and the step (c) are carried out simultaneously. The method for producing the foam described in

[15] above.

[17] After the step (c), the step (b) and the step (d) are carried out simultaneously. The method for producing the foam according to

[15] or

[16] above.

[18] The method further includes a step (e) of crosslinking any one selected from the group consisting of the kneaded product, the molded product, and the foaming agent mixture. The method for producing the foam according to

[15] or

[16] above.

[19] The method further includes a step (e) of crosslinking any one selected from the group consisting of the kneaded product, the molded product, and the foaming agent mixture. The method for producing the foam described in

[17] .

[20] After mixing the foaming agent into the kneaded mixture, The step (e) of crosslinking, the step (d) of foaming, and the step (b) of obtaining a molded body are carried out simultaneously. The method for producing the foam described in

[15] above. 〔twenty one〕 The blowing agent is nitrogen or carbon dioxide. The method for producing the foam according to

[15] or

[16] above. 〔twenty two〕 The blowing agent is nitrogen or carbon dioxide. The method for producing the foam described in

[17] . 〔twenty three〕 The blowing agent is nitrogen or carbon dioxide. The method for producing the foam described in

[18] . 〔twenty four〕 The blowing agent is nitrogen or carbon dioxide. The method for producing the foam described in

[19] above. 〔twenty five〕 The blowing agent is nitrogen or carbon dioxide. The method for producing the foam described in

[20] above. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a foam that is lightweight yet has excellent resilience and durability. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. The following present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out by appropriately modifying it within the scope of its gist.

[0012] In this specification, the term "mainly" means that the block contains 70% by mass or more of the monomer unit. For example, in the case of a "polymer block mainly composed of A units," this means that the block contains 70% by mass or more of A (monomer) units.

[0013] [Foam] The foam of this embodiment is a foam of a resin composition containing a foamable polymer. The foamable polymer contains (A) a conjugated diene polymer containing a conjugated diene monomer unit and a vinyl aromatic monomer unit (hereinafter, may be referred to as component (A)). The content of vinyl aromatic monomer units in the component (A) is 5 to 80 mass %, and the conjugated diene monomer units in the component (A) are hydrogenated. According to the above-mentioned configuration, a foam can be obtained which exhibits excellent resilience even when lightened, and which also has excellent durability, particularly long-term durability, and continuous resilience.

[0014] The resin composition constituting the foam of the present embodiment may further contain, in addition to the component (A), a foamable polymer other than the component (A), namely, component (B): at least one selected from the group consisting of an ethylene-based polymer, an ethylene-polar monomer copolymer, a polyamide-based polymer, a polyester-based polymer, and a polyurethane-based polymer. According to the above-mentioned configuration, a foam having an excellent balance between impact resilience and hardness can be obtained even when it is lightweight.

[0015] The foam of this embodiment preferably has a specific gravity of 0.08 to 0.25 inclusive, from the viewpoint of achieving a good balance of physical properties, particularly when used as a shoe midsole. Generally, lowering the specific gravity tends to result in a decrease in physical properties, such as a decrease in tear strength and an increase in compression set. However, the foam of this embodiment has an excellent balance of physical properties even at a low specific gravity. The specific gravity of the foam of this embodiment can be controlled within a desired range by adjusting the amount of foaming agent (E) described below. The specific gravity after foaming can be reduced by increasing the amount of foaming agent (E). The specific gravity of the foam of this embodiment is more preferably 0.15 or less, even more preferably 0.10 to 0.15 inclusive, and even more preferably 0.10 to 0.14 inclusive. Within these numerical ranges, the resilience tends to be improved, particularly when physically foamed. The specific gravity of the foam of this embodiment can be measured by the method described in the Examples section below.

[0016] The foam of the present embodiment may be obtained by chemical foaming or by physical foaming. When the foam is obtained by physical foaming, the foam of the present embodiment may be a foam of a foaming agent mixture, in which the foaming agent is a physical foaming agent. The physical foaming agent may be a supercritical fluid, and the foaming agent of the present embodiment may be one obtained by supercritical foaming.

[0017] The gas phase of the foam in this embodiment may be nitrogen and / or carbon dioxide. In particular, when the foam of this embodiment is obtained by supercritical foaming, as described below, a physical foaming agent in a supercritical state, such as nitrogen gas or carbon dioxide gas, is used as the foaming agent, and the foam is dispersed, melted, and mixed with a molten resin composition to perform foam molding, so that the gas phase of the foam becomes nitrogen or carbon dioxide. When the foam of the present embodiment is placed in an air environment, the gas phase of the foam may be replaced by air. For example, when the foam of the present embodiment is used as a midsole material for shoes, the gas phase may be replaced by air.

[0018] The cell size of the foam of this embodiment is not particularly limited, but is preferably 50 μm or more from the viewpoint of recovery after deformation, more preferably 50 μm or more and 300 μm or less from the viewpoint of durability, and even more preferably 100 μm or more and 200 μm or less from the viewpoint of resilience. The cell size can be measured by cutting out a cross section of a foam, observing the surface with a scanning electron microscope or a microscope, binarizing the cross-sectional image obtained, calculating the area of ​​each cell based on the binarized data, determining the diameter of the cell assuming it to be a circle, and determining the average value of the diameters of the cells included in the image as the cell size. In the case of a crosslinked foam, the cell size can be controlled to fall within the above-mentioned numerical range by adjusting the amount of crosslinking agent, the amount of blowing agent, and the foaming temperature. In the case of a non-crosslinked foam, the cell size can be controlled to fall within the above-mentioned numerical range by adjusting the viscosity of the foamable polymer, the amount of blowing agent, the foaming temperature, and the foaming pressure.

[0019] The foam of the present embodiment can be molded into various shapes and sizes, such as a sheet shape, a block shape, etc. The shape and size of the foam of the present embodiment are not particularly limited, and the foam can be molded into various shapes other than a sheet shape or a block shape.

[0020] (Resin composition) The foam of this embodiment is a foam of a resin composition containing a foamable polymer. The foamable polymer contains component (A): a conjugated diene-based polymer. The resin composition may contain, as appropriate, the following components: component (B): an expandable polymer other than component (A); component (D): a crosslinking agent; component (E): a foaming agent; and component (F): an additive.

[0021] <(A) Conjugated Diene Polymer> The foam of the present embodiment contains a conjugated diene polymer (A) (component (A)) containing a conjugated diene monomer unit and a vinyl aromatic monomer unit. The (A) conjugated diene polymer may be a block copolymer having blocks composed of each monomer unit, or a random copolymer. However, block copolymers are generally molded into crumbs or pellets, while random copolymers are generally molded into bale-like shapes. Therefore, block copolymers tend to be preferred from the viewpoint of workability when processing into foams. Furthermore, by having two or more blocks with a glass transition temperature above room temperature, these blocks act as physical crosslinking points, which tends to improve the durability of shoes. Examples of blocks with a glass transition temperature above room temperature include blocks mainly composed of vinyl aromatic monomer units, random copolymer blocks composed of vinyl aromatic monomer units and conjugated diene monomer units, and hydrogenated blocks thereof. In particular, when the (A) conjugated diene-based polymer further comprises a block mainly composed of a conjugated diene polymer or a hydrogenated block thereof, or a random copolymer block composed of a vinyl aromatic monomer unit and a conjugated diene monomer unit or a hydrogenated block thereof, it is preferable that the (A) conjugated diene-based polymer further comprises a block mainly composed of a vinyl aromatic monomer unit, from the viewpoint of ease of formation of physical crosslinking points by phase separation. Here, "mainly composed of" means that a single monomer unit accounts for 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass, of the total mass of the polymer block.

[0022] [Content of polymer block mainly composed of vinyl aromatic monomer units in component (A)] The content of the polymer block mainly composed of vinyl aromatic monomer units in component (A) is not particularly limited, but is preferably 5% by mass or more relative to the total amount of the conjugated diene polymer (A) from the viewpoints of flexibility and tear strength of the foam of this embodiment, and is preferably 80% by mass or less from the viewpoint of resilience. Within the above numerical range, the specific gravity of the foam of this embodiment can be reduced, thereby making it lighter. From the viewpoint of the hardness and resilience of the foam of this embodiment, the content of the polymer block mainly composed of vinyl aromatic monomer units in component (A) is more preferably 10 to 50 mass %, even more preferably 20 to 45 mass %, and even more preferably 25 to 35 mass %. The content of the polymer block mainly composed of vinyl aromatic monomer units in component (A) can be controlled within the above-mentioned range by adjusting the polymerization conditions, such as the amount of monomer added and polymerization time, in the polymerization step of component (A).

[0023] The vinyl aromatic compound forming the vinyl aromatic monomer units contained in component (A) is not limited to the following, and known compounds can be used, such as styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, divinylbenzene, 1,1-diphenylethylene, N,N-dimethyl-p-aminoethylstyrene, and N,N-diethyl-p-aminoethylstyrene. These may be used alone or in combination of two or more. Of these, styrene is preferred.

[0024] [Vinyl aromatic monomer unit content in component (A)] The content of vinyl aromatic monomer units in component (A) is 5% by mass or more from the viewpoint of tear strength of the foam of this embodiment, and 80% by mass or less from the viewpoint of resilience. When the content is within the above range, the specific gravity of the foam of this embodiment can be reduced, thereby making it lighter. The content of vinyl aromatic monomer units in component (A) is preferably 10 to 50 mass %, more preferably 20 to 45 mass %, and even more preferably 25 to 35 mass %, from the viewpoint of the hardness and resilience of the foam of this embodiment. The content of vinyl aromatic monomer units in component (A) can be controlled within the above range by adjusting the polymerization conditions, such as the amount of monomer added and polymerization time, in the polymerization step of component (A). The content of vinyl aromatic monomer units in component (A) can be measured using an ultraviolet spectrophotometer, as described in the Examples below.

[0025] The content of polymer blocks mainly composed of vinyl aromatic monomer units in component (A) can be calculated using the mass of polymer blocks mainly composed of vinyl aromatic monomer units in the conjugated diene polymer before hydrogenation, which is determined by a method in which a conjugated diene polymer before hydrogenation is oxidatively decomposed with t-butyl hydroperoxide in the presence of an osmium tetroxide catalyst (the method described in I. M. Kolthoff, et al., Polym. Sci., 1,429 (1946)) (hereinafter referred to as the "osmium tetroxide decomposition method"). The osmium tetroxide decomposition method can detect polymer blocks mainly composed of vinyl aromatic monomer units with an average degree of polymerization of about 30 or more.

[0026] The content of polymer blocks mainly composed of vinyl aromatic monomer units in component (A) can be measured by nuclear magnetic resonance (NMR) spectroscopy using a hydrogenated conjugated diene polymer according to the method described in Y. Tanaka, et al., RUBBER CHEMISTRY and TECHNOLOGY, 54, 685 (1981). This method is hereinafter referred to as the NMR method. The NMR method will be specifically explained using as an example a conjugated diene polymer in which the vinyl aromatic monomer unit is styrene and the conjugated diene monomer unit is 1,3-butadiene. After hydrogenation, 30 mg of the conjugated diene polymer was dissolved in 1 g of deuterated chloroform, and the resulting sample was analyzed by proton nuclear magnetic resonance ( 1 H-NMR) is measured. From the measurement results obtained, the content of polymer blocks (polystyrene blocks in this case) mainly composed of vinyl aromatic monomer units (hereinafter referred to as "Ns value") can be determined by calculating the ratio of the integrated value in the chemical shift range of 6.9 ppm to 6.3 ppm to the total integrated value. More specifically, it can be determined by the following formulas (1) to (4). Block styrene strength (b-St strength) =(integrated value of 6.9 ppm to 6.3 ppm) / 2 (1) Random styrene strength (r-St strength) = (integrated value of 7.5 ppm to 6.9 ppm) - 3 × (b-St) (2) Ethylene-butylene strength (EB strength) = Total integrated value - 3 × {(b-St intensity) + (r-St intensity)} / 8 (3) Polystyrene block content (Ns value) measured by NMR method =104×(b-St strength) / [104×{(b-St strength)+(r-St strength)}+56×(EB strength)](4) Here, it is known that the following formula (5) holds true between the content (Os value) of polymer blocks mainly composed of vinyl aromatic monomer units in a conjugated diene polymer before hydrogenation, measured by the osmium tetroxide decomposition method, and the content (Ns value) of polymer blocks mainly composed of vinyl aromatic monomer units in a conjugated diene copolymer after hydrogenation, measured by the NMR method. Os value = -0.012 × (Ns value) 2 +1.8×(Ns value)-13.0 (5)

[0027] The conjugated diene forming the conjugated diene monomer unit contained in component (A) is a diolefin having a conjugated double bond. The diolefin is not limited to the following, and known diolefins can be used. For example, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-cyclopentadiene, 2-methyl-1,3-pentadiene, myrcene, 2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 2-phenyl-1,3-butadiene, 2-phenyl-1,3-pentadiene, and the like. Examples of the alkylene include dienes, 3-phenyl-1,3-pentadiene, 2,3-dimethyl-1,3-pentadiene, 4-methyl-1,3-pentadiene, 2-hexyl-1,3-butadiene, 1,3-hexadiene, 1,3-cyclohexadiene, 3-methyl-1,3-hexadiene, 2-benzyl-1,3-butadiene, 2-p-tolyl-1,3-butadiene, and farnesene. These may be used alone or in combination of two or more. Among these, 1,3-butadiene is preferred.

[0028] When a polymer chain made of 1,3-butadiene (e.g., polybutadiene) is subjected to heat, light, or radicals, the hydrogen atom from the C—H bond in the polymer chain is abstracted to generate a carbon radical. The resulting carbon radical tends to undergo an addition reaction with the double bond of the polybutadiene, resulting in crosslinking. Therefore, when 1,3-butadiene is used as a conjugated diene to form a foam, the melt tension increases, and the foam tends to generate stable cells. On the other hand, when a polymer chain made of isoprene (e.g., polyisoprene) is subjected to heat, light, or radicals to form a carbon radical, the resulting carbon radical tends to undergo primary scission upon reaction with oxygen. Therefore, when isoprene is used as a conjugated diene to form a foam, the melt tension decreases, and the foam tends to fail to generate stable cells. Furthermore, hydrogenated polybutadiene is relatively prone to crystallization, and crystallization during stretching improves tensile strength and tear strength, tending to improve the durability of the foam. On the other hand, hydrogenated polyisoprene is relatively difficult to crystallize, so it is difficult to improve the tensile strength and tear strength even when stretched, and the durability of the foam tends to be less improved than that of polybutadiene. The content of conjugated diene monomer units in component (A) is preferably 50 to 90 mass%, more preferably 55 to 80 mass%, and even more preferably 65 to 75 mass%. Within this range, a foam with a good balance between hardness and resilience tends to be obtained.

[0029] [Hydrogenation rate of conjugated diene monomer units in component (A)] The component (A) used in the foam of this embodiment is hydrogenated, and the hydrogenation rate of the double bonds of the conjugated diene monomer units in the component (A) is the total amount of hydrogenated conjugated diene monomer units in all conjugated diene monomer units, and is preferably 30 to 100 mass%. The hydrogenation rate is more preferably 50 to 100% by mass, even more preferably 60 to 90% by mass, and even more preferably 75 to 85% by mass. When the hydrogenation rate of the double bonds of the conjugated diene monomer units in component (A) is within the above range, the crosslinking rate during molding is slowed down, resulting in less uneven crosslinking and fine, uniform foaming. Furthermore, the degree of closed cells is increased, making it possible to produce a foam that has excellent resilience and low compression set even when lightened. In particular, when the component (B) (described below) further contains an ethylene polymer as an expandable polymer other than the component (A), a hydrogenation rate of the component (A) of 50 to 100% by mass tends to make the crosslinking reaction rates of the components (A) and (B) comparable, and tends to facilitate the formation of uniform crosslinks. Furthermore, a hydrogenation rate of the conjugated diene monomer units in the component (A) of 60 to 90% by mass tends to facilitate the formation of more uniform crosslinks, improving compression set, and a hydrogenation rate of 75 to 85% by mass tends to further improve compression set. The hydrogenation rate of the double bonds of the conjugated diene monomer units in component (A) can be controlled within the above-mentioned range by adjusting the type and amount of hydrogenation catalyst, the amount of hydrogen added, the temperature, pressure, hydrogenation time, etc. in the hydrogenation reaction of component (A). The hydrogenation rate of the conjugated diene monomer units in component (A) can be measured by the method shown in the Examples below.

[0030] [Hydrogenation rate of 1,2-vinyl bond and 3,4-vinyl bond in conjugated diene monomer unit] Furthermore, with regard to the hydrogenation rate (vinyl hydrogenation rate) of the 1,2-vinyl bonds and 3,4-vinyl bonds in the conjugated diene monomer units in component (A), a low hydrogenation rate tends to cause excessive crosslinking, making it difficult to form a uniform foam. Therefore, the rate is preferably 80% or more, and from the viewpoint of durability when repeated deformation occurs, the rate is more preferably 90% or more, and even more preferably 95% or more. The hydrogenation rates of the 1,2-vinyl bonds and 3,4-vinyl bonds in the conjugated diene monomer units in the component (A) can be measured by NMR, and can be controlled within the above-mentioned range by mixing conjugated diene polymers that differ in hydrogenation catalyst, amount of hydrogen, amount of hydrogenation catalyst, pressure, temperature, and hydrogenation rate during hydrogenation. The NMR method will be specifically explained using as an example a conjugated diene polymer in which the vinyl aromatic monomer unit is styrene and the conjugated diene monomer unit is 1,3-butadiene. After hydrogenation, 30 mg of the conjugated diene polymer was dissolved in 1 g of deuterated chloroform, and the resulting sample was analyzed by proton nuclear magnetic resonance ( 1 In the measurement results obtained, symbols X1, X2, X3, X4, X5, X6, and X7 are defined as follows: X1: The area value of the range surrounded by the line connecting the positions of the smallest signal intensity in the 7.26 ppm to 7.25 ppm section and the 7.27 ppm to 7.26 ppm section, with 7.26 ppm as the center, and the NMR spectrum. X2: Area value of the range enclosed by the line connecting the signal positions of 8.0 ppm and 6.0 ppm and the NMR spectrum X3: The area value between the chemical shift of the position with the smallest signal intensity between 5.2 ppm and 4.9 ppm and 4.0 ppm, among the area values ​​enclosed by the line connecting the signal positions of 6.0 ppm and 4.0 ppm and the NMR spectrum. X4: The area value between the chemical shift of the position with the smallest signal intensity between 5.2 ppm and 4.9 ppm and 6.0 ppm, among the area values ​​enclosed by the line connecting the signal positions of 6.0 ppm and 4.0 ppm and the NMR spectrum. X5: The area enclosed by the line connecting the signal positions of 4.0 ppm and 0.3 ppm and the NMR spectrum, the area within a range of 0.3 ppm from the chemical shift of the position with the smallest signal intensity among the valleys of the NMR spectrum between 1.05 ppm and 0.85 ppm (however, if there is no valley between 1.05 ppm and 0.85 ppm, the area within a range of 0.3 ppm from the chemical shift of the position with the smallest signal intensity among the valleys of the NMR spectrum between 1.05 ppm and 0.85 ppm is used). X6: The area enclosed by the line connecting the signal positions at 4.0 ppm and 0.3 ppm and the NMR spectrum X7: The area value of the range surrounded by the line connecting the positions of the smallest signal intensity in each of the sections from 1.49 ppm to 1.50 ppm and from 1.50 ppm to 1.51 ppm, with 1.50 ppm as the center, and the NMR spectrum (however, if the line connecting the positions of the smallest signal intensity is above the NMR spectrum, it is set to 0). The hydrogenation rate of 1,2-vinyl bonds and 3,4-vinyl bonds is the proportion of polymer units of hydrogenated 1,2-vinyl bonds and 3,4-vinyl bonds to the total of hydrogenated 1,2-vinyl bonds and 3,4-vinyl bonds and non-hydrogenated 1,2-vinyl bonds and 3,4-vinyl bonds. More specifically, it can be calculated using the following formulas (6) to (8). Area value per proton of hydrogenated 1,2-vinyl bond and 3,4-vinyl bond monomer units (hydrogenated vinyl) =X5 / 3 (6) Area value per proton of unhydrogenated 1,2-vinyl bond and 3,4-vinyl bond monomer units (unhydrogenated vinyl) =X3 / 2 (7) Hydrogenation rate of 1,2-vinyl bond and 3,4-vinyl bond = (hydrogenated vinyl) / {(hydrogenated vinyl) + (unhydrogenated vinyl)} × 100 (8)

[0031] [Structure of component (A)] The component (A) contains a conjugated diene monomer unit and a vinyl aromatic monomer unit, but may contain a monomer unit formed from another polymerizable monomer as a constituent unit other than the conjugated diene monomer unit and the vinyl aromatic monomer unit, as long as the object of this embodiment is not impaired. The structure of component (A) is not particularly limited, but is preferably a copolymer containing conjugated diene monomer units using 1,3-butadiene and vinyl aromatic monomer units using styrene, and / or a hydrogenated product thereof. That is, the conjugated diene polymer constituting component (A) may be either a non-hydrogenated polymer or a hydrogenated polymer, or may be a mixture of these. Specifically, a block copolymer consisting of a polymer block mainly composed of styrene and a polymer block mainly composed of 1,3-butadiene and / or a hydrogenated product thereof is more preferred. More specifically, a block copolymer having a block structure of styrene block-1,3-butadiene block-styrene block and / or a hydrogenated product thereof can be mentioned. This allows the styrene block to act as a physical crosslinking point, which tends to exhibit elasticity.

[0032] [Total amount of 1,2-vinyl bonds and 3,4-vinyl bonds in the conjugated diene monomer units in component (A)] The amount of 1,2-vinyl bonds and 3,4-vinyl bonds (hereinafter sometimes abbreviated as "vinyl bond amount") in the conjugated diene monomer units of component (A) is not particularly limited, but is preferably 10 to 60 mass %. Here, the vinyl bond content is the sum of the 1,2-vinyl bond content and the 3,4-vinyl bond content. The vinyl bond content is the vinyl bond content before hydrogenation and refers to the ratio of the amount of vinyl bond moieties to the total amount of conjugated diene monomer moieties (hereinafter referred to as "1,4-bond moieties") incorporated into the polymer via 1,4-bonds (including cis and trans) and conjugated diene monomer moieties (hereinafter referred to as "vinyl bond moieties") incorporated into the polymer via 1,2-vinyl bonds and 3,4-vinyl bonds in the conjugated diene copolymer before hydrogenation. The lower limit of the vinyl bond amount is more preferably 15% by mass or more, and even more preferably 25% by mass or more, and the upper limit is more preferably 50% by mass or less, and even more preferably 45% by mass or less. When the combined amount of 1,2-vinyl bonds and 3,4-vinyl bonds in the conjugated diene monomer units in the component (A) is 10 to 60 mass %, the productivity of foams using the conjugated diene copolymer (A) tends to be excellent. If the vinyl bond content is low, the viscosity of component (A) increases, making it necessary to increase the reaction temperature and / or the power performance of the reactor or conveyor. Furthermore, if the vinyl bond content is high, the viscosity of component (A) decreases, but the component tends to become sticky and prone to polymer blocking. Furthermore, if the vinyl bond content is too low, component (A) tends to crystallize easily, especially after hydrogenation, making the foam hard and reducing its resilience. On the other hand, if the vinyl bond content is too high, the Tg of component (A) increases after hydrogenation, and the foam of this embodiment tends to have reduced resilience.

[0033] The 1,2-vinyl bond content and 3,4-vinyl bond content in the conjugated diene monomer units of component (A) can be controlled within the above numerical ranges by adjusting the amount of vinylating agent (described below) and the polymerization temperature. Increasing the amount of vinylating agent or lowering the polymerization temperature tends to increase the 1,2-vinyl bond content and 3,4-vinyl bond content. For example, when using 1,3-butadiene as the conjugated diene monomer, normal butyl lithium (NBL) as the polymerization initiator, and N,N,N',N'-tetramethylethylenediamine (TMEDA) as the vinylating agent, in order to control the combined amount of 1,2-vinyl bonds and 3,4-vinyl bonds to 10% by mass or more, it is preferable to control the amount of TMEDA to 0 to 0.05 moles per mole of NBL and the polymerization temperature to 60 to 70°C. On the other hand, in order to control the combined amount of 1,2-vinyl bonds and 3,4-vinyl bonds to 60% by mass or less, it is preferable to control the amount of TMEDA to 0.5 to 1 mole per mole of NBL and the polymerization temperature to 50 to 70°C. The vinyl bond content can be measured by the method shown in the examples below.

[0034] [Peak top molecular weight of component (A)] The peak top molecular weight of component (A) is not particularly limited, but is usually 10,000 or more, preferably 50,000 to 500,000, more preferably 60,000 to 400,000, and even more preferably 70,000 to 300,000. When the peak top molecular weight of the component (A) is within the above numerical range, the productivity of the conjugated diene polymer (A) and the processability of the foam of this embodiment tend to be excellent. The peak top molecular weight of component (A) can be controlled within the above range by adjusting the polymerization conditions, such as the amount of monomer added, amount of polymerization initiator, polymerization time, and polymerization temperature, in the polymerization step of component (A).

[0035] The structure of the conjugated diene polymer (A) is not particularly limited, but examples thereof include structures represented by the following formulas.

[0036] (bc) n , c-(bc) n , b-(cb) n , (bc) m -X, (cb) m -X, [(bc) n ] m -X, [(cb) n ] m -X, [c-(bc) n ] m -X, [b-(cb) n ] m -X, [(bc) n -b] m -X, [(cb) n -c] m -X, (ab) n , b-(ab) n , a-(ba) n , (ab) m -X, (ba) m -X, [(ab) n ] m -X, [(ba) n ] m -X, [b-(ab) n ] m -X, [a-(ba) n ] m -X, [(ab) n -a] m -X, [(ba) n -b] m -X, c-(ba)n 、c-(a-b) n 、 c-(a-b-a) n 、c-(b-a-b) n 、 a-c-(b-a) n 、a-c-(a-b) n 、 a-c-(b-a) n -b、[(a-b-c) n ] m -X、 [a-(b-c) n ] m -X、[(a-b) n -c] m -X、 [(a-b-a) n -c] m -X、 [(b-a-b) n -c] m -X、[(c-b-a) n ] m -X、 [c-(b-a) n ] m -X、[c-(a-b-a) n ] m -X、[c-(b-a-b) n ] m -X a-(b-c) n 、a-(c-b) n 、 a-(c-b-c) n 、a-(b-c-b) n 、 c-a-(b-c) n 、c-a-(c-b) n 、 c-a-(b-c) n -b、[(c-b-a) n ] m -X、 [c-(b-a) n ] m -X、[(c-b) n -a] m -X、 [(c-b-c) n -a] m -X、 [(bcb) n -a] m -X, [(abc) n ] m -X, [a-(bc) n ] m -X, [a-(cbc) n ] m -X, [a-(bcb) n ] m -X b-(ac) n , b-(ca) n , b-(cac) n , b-(aca) n , cb-(ac) n , cb-(ca) n , cb-(ac) n -a, [(cab) n ] m -X, [c-(ab) n ] m -X, [(ca) n -b] m -X, [(cac) n -b] m -X, [(bcb) n -b] m -X, [(bac) n ] m -X, [b-(ac) n ] m -X, [b-(cac) n ] m -X, [b-(aca) n ] m -X

[0037] In the above general formulas, a represents a polymer block mainly composed of vinyl aromatic monomer units, b represents a polymer block mainly composed of conjugated diene monomer units, and c represents a polymer block having vinyl aromatic monomer units and conjugated diene monomer units. The conjugated diene monomer units may be hydrogenated. n is an integer of 1 or more, and preferably an integer of 1 to 5. m is an integer of 2 or more, and preferably an integer of 2 to 11. X represents a residue of a coupling agent or a residue of a multifunctional initiator.

[0038] [Fluidity of component (A)] There are no particular limitations on the fluidity of component (A), but the melt flow rate (MFR, 230°C, 2.16 kg) of component (A) is preferably 1.0 g / 10 min or more, more preferably 1.5 g / 10 min or more, and even more preferably 2.0 g / 10 min or more. The upper limit is preferably 50 g / 10 min or less, more preferably 30 g / 10 min or less, and even more preferably 10 g / 10 min or less. When the MFR of component (A) is 50 g / 10 min or less, when the resin composition is injection- or press-molded in the process for producing the foam of this embodiment, there tends to be less flash protruding from the mold, and raw material loss can be suppressed. Generally, in resin compositions for foam production, the crosslinking agent (D) is mixed at a low temperature where the foaming properties of the blowing agent are not expressed. Therefore, when a resin composition for foam production is composed of component (A) and component (B): a foamable polymer other than component (A), these components are not completely compatible. Furthermore, differences in the structures of components (A) and (B) also affect the compatibility of the components. Therefore, the properties of each component alone tend to be exhibited in the resin composition for foam production, and it is thought that high fluidity of component (A) can result in increased flash. When the MFR of component (A) is 1.0 g / 10 min or higher, component (A) mixes easily with component (B), and the amount of undissolved component tends to be small. This contributes to the formation of a uniform foam, suppresses undissolved component, and ensures that component (A) is mixed in the desired ratio, which tends to facilitate the desired resilience and dimensional stability. The MFR of component (A) depends mainly on the molecular weight, hydrogenation rate, vinyl aromatic monomer unit content, and vinyl bond content of the conjugated diene monomer unit of component (A). The higher the molecular weight, hydrogenation rate, and vinyl aromatic monomer unit content, the lower the MFR of component (A). Conversely, the lower the vinyl bond content of the conjugated diene monomer unit, the lower the MFR of component (A). The MFR of component (A) can be controlled within the above range by adjusting the polymerization conditions, such as the amount of monomer added, the amount of polymerization initiator, the polymerization time, and the polymerization temperature, during the polymerization step of component (A). The MFR of component (A) can be measured by the method described in the Examples below.

[0039] [Tan δ peak temperature of component (A)] From the viewpoint of the resilience of the foam of this embodiment under low temperature conditions, the tan δ peak temperature of component (A) is preferably −25° C. or lower, more preferably −30° C. or lower, and even more preferably −35° C. or lower. The tan δ peak temperature of component (A) can be measured using a dynamic viscoelasticity measuring device. For example, it can be measured using an ARES-G2 (manufactured by TA Instruments). A 2 mm thick sheet of component (A) is compression molded at a temperature of about 200°C, at which component (A) melts, and the sheet is cut into a 12.6 x 40 mm strip. This sample is heated from the measurement temperature of -100°C at a rate of 3°C / min while applying a 0.5% strain, and the peak temperature can be obtained by plotting tan δ at each temperature. The tan δ peak temperature of component (A) can be controlled within the above-mentioned range by adjusting the vinyl bond content of the conjugated diene monomer unit, the hydrogenation rate, and the composition ratio of the conjugated diene monomer unit and the vinyl aromatic monomer unit in the copolymer block composed of the conjugated diene monomer unit and the vinyl aromatic monomer unit.

[0040] [Content of component (A)] In the foam of this embodiment, the content of the above-mentioned component (A) is preferably 5 to 70 parts by mass per 100 parts by mass of the expandable polymer constituting the resin composition for foam of this embodiment. By making the content of component (A) 5 parts by mass or more, the effect of improving the resilience of the foam can be obtained. By setting the content of component (A) to 70 parts by mass or less, the effect of improving the tear strength of the foam can be obtained. The content of component (A) is more preferably 5 to 50 parts by mass, and even more preferably 5 to 30 parts by mass, per 100 parts by mass of the expandable polymer constituting the resin composition for foams of the present embodiment.

[0041] [Method of producing component (A)] The method for producing component (A) is not particularly limited, and any known method can be used. For example, the method may include a polymerization step and a hydrogenation step as described below. The polymerization step is not particularly limited, but may be, for example, a step of obtaining a homopolymer, a random copolymer, and / or a block copolymer by living anionic polymerization in which a conjugated diene and a vinyl aromatic compound are polymerized in a hydrocarbon solvent using an organic alkali metal compound as a polymerization initiator.

[0042] The hydrocarbon solvent is not particularly limited, and known solvents can be used. Examples include aliphatic hydrocarbons such as n-butane, isobutane, n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclohexane, cycloheptane, and methylcycloheptane; and aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene. These hydrocarbon solvents may be used alone or in combination of two or more.

[0043] As the polymerization initiator, an organic alkali metal compound can be used, and examples thereof include, but are not limited to, aliphatic hydrocarbon alkali metal compounds, aromatic hydrocarbon alkali metal compounds, and organic amino alkali metal compounds, which are generally known to have anionic polymerization activity toward conjugated diene compounds and vinyl aromatic compounds. Examples of the alkali metal include lithium, sodium, and potassium. Suitable organic alkali metal compounds include aliphatic and aromatic hydrocarbon lithium compounds having 1 to 20 carbon atoms, specifically compounds containing one lithium atom per molecule, dilithium compounds containing multiple lithium atoms per molecule, trilithium compounds, tetralithium compounds, etc. More specific examples include n-propyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, n-pentyllithium, n-hexyllithium, benzyllithium, phenyllithium, tolyllithium, a reaction product of diisopropenylbenzene and sec-butyllithium, and a reaction product of divinylbenzene, sec-butyllithium, and 1,3-butadiene.

[0044] The total amount of 1,2-vinyl bonds and 3,4-vinyl bonds in the conjugated diene monomer units in component (A) can be controlled by using a Lewis base (e.g., ether, amine, etc.) as a vinylating agent. The amount of vinylating agent used is adjusted depending on the desired amount of vinyl bonds. The vinylating agent is not limited to the following, but examples thereof include ether compounds and tertiary amine compounds.

[0045] Examples of the ether compound that is the vinylating agent include linear ether compounds and cyclic ether compounds. Examples of linear ether compounds include, but are not limited to, dialkyl ether compounds of ethylene glycol such as dimethyl ether, diethyl ether, diphenyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and ethylene glycol dibutyl ether, and dialkyl ether compounds of diethylene glycol such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and diethylene glycol dibutyl ether. Furthermore, examples of cyclic ether compounds include, but are not limited to, alkyl ethers such as tetrahydrofuran, dioxane, 2,5-dimethyloxolane, 2,2,5,5-tetramethyloxolane, 2,2-bis(2-oxolanyl)propane, and furfuryl alcohol.

[0046] Examples of the tertiary amine compound that is the vinylating agent include, but are not limited to, pyridine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine, 1,2-dipiperidinoethane, trimethylaminoethylpiperazine, N,N,N',N",N"-pentamethylethylenetriamine, N,N'-dioctyl-p-phenylenediamine, trimethylamine, triethylamine, tributylamine, N,N-dimethylaniline, N-ethylpiperidine, N-methylpyrrolidinetetramethylpropanediamine, 1,2-dipiperidinoethane, and bis[2-(N,N-dimethylamino)ethyl]ether. The tertiary amine compound is preferably a compound having two amines, and among them, a compound having an intramolecularly symmetric structure is more preferred, and N,N,N',N'-tetramethylethylenediamine, bis[2-(N,N-dimethylamino)ethyl]ether, and 1,2-dipiperidinoethane are even more preferred. The vinylating agents described above may be used alone or in combination of two or more.

[0047] After the polymerization step, the conjugated diene polymer can be hydrogenated by a conventionally known method. The hydrogenation method in the hydrogenation step is not particularly limited, and examples thereof include a method in which hydrogen gas is supplied to the conjugated diene polymer obtained in the polymerization step in the presence of a hydrogenation catalyst to hydrogenate the polymer. By including the hydrogenation step, residual double bonds in the conjugated diene monomer units are hydrogenated, and a more thermally stable hydrogenated conjugated diene polymer can be obtained. The hydrogenation rate can be controlled, for example, by the amount of catalyst used during hydrogenation and the amount of hydrogen gas supplied (hereinafter also referred to as "feed"). The hydrogenation rate can be controlled, for example, by the amount of catalyst used during hydrogenation, the amount of hydrogen gas supplied, the hydrogen gas pressure, the reaction temperature, etc. The hydrogenation step is preferably carried out at a timing after the production reaction of the conjugated diene copolymer in the polymerization step has stopped. After the hydrogenation reaction is completed, a stabilizer may be added. The stabilizer is not particularly limited, but examples thereof include octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate.

[0048] The hydrogenation catalyst is not particularly limited, and conventionally known hydrogenation catalysts can be used. Specific examples include supported heterogeneous hydrogenation catalysts in which metals such as Ni, Pt, Pd, and Ru are supported on carbon, silica, alumina, diatomaceous earth, and the like; so-called Ziegler-type hydrogenation catalysts that use transition metal salts such as organic acid salts or acetylacetone salts of Ni, Co, Fe, and Cr, and a reducing agent such as organoaluminum; and homogeneous hydrogenation catalysts such as so-called organometallic complexes of organometallic compounds such as Ti, Ru, Rh, and Zr. Among these, preferred hydrogenation catalysts include titanocene compounds and reducing organometallic compounds.

[0049] The reaction conditions for the hydrogenation reaction are not particularly limited, but are usually carried out at a temperature in the range of 0 to 200°C, more preferably 30 to 150°C. The hydrogen pressure in the hydrogenation reaction is not particularly limited, but is usually 0.1 to 15 MPa, preferably 0.2 to 10 MPa, and more preferably 0.3 to 5 MPa. The hydrogenation reaction time is usually 3 minutes to 10 hours, preferably 10 minutes to 5 hours. The hydrogenation reaction can be carried out as a batch process, a continuous process, or a combination thereof.

[0050] If necessary, the solution of the conjugated diene polymer obtained through the above-mentioned polymerization step and hydrogenation step can be subjected to removal of catalyst residues and separation of the conjugated diene polymer from the solvent. The method for separating the conjugated diene polymer is not particularly limited, and examples thereof include a method in which a polar solvent that is a poor solvent for the conjugated diene polymer after hydrogenation, such as acetone or alcohol, is added to the reaction solution after hydrogenation to precipitate and recover the conjugated diene polymer; a method in which a solution of the conjugated diene polymer is poured into hot water with stirring and the solvent is removed by steam stripping to recover the conjugated diene polymer; and a method in which a solution of the conjugated diene polymer is directly heated to distill off the solvent.

[0051] (A) Conjugated diene polymer may contain various stabilizers such as phenol-based stabilizers, phosphorus-based stabilizers, sulfur-based stabilizers, and amine-based stabilizers.

[0052] Component (A) may have a functional group. The method for providing component (A) with a functional group is not particularly limited, but examples include a method using a polymerization initiator having a functional group in the polymerization reaction in the polymerization step; and a method using an unsaturated monomer having a functional group in the polymerization reaction in the polymerization step. Alternatively, the functional group may be added by a modification reaction. An example of such a modification reaction method is a method in which a modifier having a functional group is added to the living end of the conjugated diene polymer obtained by the polymerization reaction in the polymerization step. Specifically, the conjugated diene polymer can be functionalized by reacting a functional group-containing compound with the polymerized conjugated diene polymer. The site where the functional group is introduced, the number of functional groups, etc. are not particularly limited, but from the viewpoint of the physical properties of the foam of this embodiment, it is preferable to modify the polymer chain end to form a functional group. Examples of functional groups include hydroxyl groups, carbonyl groups, thiocarbonyl groups, acid halide groups, acid anhydride groups, carboxyl groups, thiocarboxylate groups, aldehyde groups, thioaldehyde groups, carboxylic acid ester groups, amide groups, sulfonic acid groups, sulfonate ester groups, phosphoric acid groups, phosphoric acid ester groups, amino groups, imino groups, cyano groups, pyridyl groups, quinoline groups, epoxy groups, thioepoxy groups, sulfide groups, isocyanate groups, isothiocyanate groups, silicon halide groups, silanol groups, alkoxysilane groups, tin halide groups, alkoxytin groups, phenyltin groups, etc. Among these, from the viewpoint of the balance of physical properties of the foam, at least one selected from the group consisting of hydroxyl groups, carbonyl groups, acid anhydride groups, carboxyl groups, epoxy groups, amino groups, and silanol groups is preferred.

[0053] Examples of the "polymerization initiator having a functional group" include, but are not limited to, 3-lithio-1-[N,N-bis(trimethylsilyl)]aminopropane, 2-lithio-1-[N,N-bis(trimethylsilyl)]aminoethane, 3-lithio-2,2-dimethyl-1-[N,N-bis(trimethylsilyl)]aminopropane, 2,2,5,5-tetramethyl-1-(3-lithiopropyl)-1-aza-2,5-disilacyclopent ... 2,2-dimethyl-propyl)-1-aza-2,5-disilacyclopentane, 2,2,5,5-tetramethyl-1-(2-lithioethyl)-1-aza-2,5-disilacyclopentane, 3-lithio-1-[N-(tert-butyl-dimethylsilyl)-N-trimethylsilyl]aminopropane, 3-lithio-1-(N-methyl-N-trimethylsilyl)aminopropane, 3-lithio-1-(N-ethyl-N-trimethylsilyl)aminopropane, and lithium piperidide.

[0054] Examples of the "unsaturated monomer having a functional group" include, but are not limited to, p-[N,N-bis(trimethylsilyl)amino]styrene, p-[N,N-bis(trimethylsilyl)aminomethyl]styrene, p-{2-[N,N-bis(trimethylsilyl)amino]ethyl}styrene, m-[N,N-bis(trimethylsilyl)amino]styrene, p-(N-methyl-N-trimethylsilylamino)styrene, and p-(N-methyl-N-trimethylsilylaminomethyl)styrene.

[0055] Examples of the "modifier having a functional group" include, but are not limited to, tetraglycidyl metaxylenediamine, tetraglycidyl-1,3-bisaminomethylcyclohexane, ε-caprolactone, 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, N,N'-dimethylpropyleneurea, and N-methylpyrrolidone.

[0056] The method for producing the conjugated diene polymer (A) having a functional group is not particularly limited, and known methods can be used, such as a method of heating and melting an unfunctionalized conjugated diene polymer (100 to 300°C) and reacting it with a functional group-containing compound, a solution polymerization method using an organic solvent, and a method of reacting an unfunctionalized conjugated diene polymer in a slurry state with a functional group-containing compound at 0 to 150°C.

[0057] The method for epoxidizing a conjugated diene polymer is not particularly limited, and examples thereof include the method described in JP-A-6-220124, in which the conjugated diene polymer can be epoxidized by reacting it with an epoxidizing agent such as a peracid or a hydroperoxide. The peracids are not particularly limited, and examples thereof include performic acid, peracetic acid, perbenzoic acid, trifluoroperacetic acid, etc. Among these, peracetic acid is preferred because it is industrially produced in large quantities, is available at low cost, and is highly stable. The hydroperoxides are not particularly limited, and examples thereof include hydrogen peroxide, tert-butyl hydroperoxide, and cumene peroxide. When carrying out an epoxidation reaction, a catalyst can be used as needed. For example, when carrying out an epoxidation reaction using peracids, an alkali such as sodium carbonate or an acid such as sulfuric acid can be used as a catalyst. When using hydroperoxides as the epoxidizing agent, a catalytic effect can be obtained by using a mixture of tungstic acid and caustic soda in combination with hydrogen peroxide, an organic acid in combination with hydrogen peroxide, or molybdenum hexacarbonyl in combination with tert-butyl hydroperoxide. The epoxidation reaction of a conjugated diene polymer can be carried out by adjusting reaction conditions such as whether or not a solvent is used and the reaction temperature depending on the reaction apparatus used and the physical properties of the raw materials. For example, the reaction temperature can be selected depending on the reactivity of the epoxidizing agent used. When peracetic acid, which is a preferred epoxidizing agent, is used, the reaction temperature is preferably 0 to 70°C. By setting the reaction temperature within this range, a high reaction rate can be achieved while suppressing the decomposition reaction of peracetic acid.

[0058] The method for converting a conjugated diene polymer into an acid anhydride group is not particularly limited, and examples thereof include the method described in JP-A-62-79211, etc., and specifically includes a method of graft-modifying a conjugated diene polymer with an α,β-unsaturated carboxylic acid or a derivative thereof, such as an anhydride, ester, amidation product, or imidation product thereof. Examples of α,β-unsaturated carboxylic acids or derivatives thereof include maleic anhydride, maleic anhydride imide, acrylic acid or its ester, methacrylic acid or its ester, endo-cis-bicyclo[2.2.1]-5-heptene-2,3-dicarboxylic acid or its anhydride, and the like. The amount of α,β-unsaturated carboxylic acid or its derivative added is not particularly limited, but is usually 0.01 to 20 parts by mass, and preferably 0.1 to 10 parts by mass, per 100 parts by mass of the conjugated diene polymer after hydrogenation. The reaction temperature for graft modification is not particularly limited, but is preferably 100 to 300°C, and more preferably 120 to 280°C.

[0059] <(B): Foamable polymer other than the component (A)> The foam of this embodiment may contain a foamable polymer (B) other than the above-described component (A). The component (B) preferably contains at least one selected from the group consisting of ethylene polymers, ethylene-polar monomer copolymers, polyamide polymers, polyester polymers, and polyurethane polymers. It is more preferable that the component (B) contains an ethylene-polar monomer copolymer.

[0060] An ethylene-based polymer is a polymer containing ethylene as a structural unit. The ethylene-based polymer is not particularly limited, and known polymers can be used. Examples of the ethylene-based polymer include polyethylene (PE), which is a polymer of ethylene; ethylene-α-olefin copolymers, which are low-crystalline random copolymers composed of ethylene and an α-olefin having 3 to 10 carbon atoms; and block copolymers containing ethylene and an α-olefin (for example, a multiblock copolymer in which the hard segment is crystalline polyethylene and the soft segment is composed of a random block of ethylene-octene).

[0061] When polyethylene is used as component (B) in the foam of this embodiment, the type is not limited, and known polyethylenes can be used, such as high-density polyethylene, ultra-high-molecular-weight high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and ultra-low-density polyethylene.

[0062] The ethylene-based polymer may be a copolymer of three or more types of ethylene and two or more types of compounds other than ethylene. For example, a copolymer (terpolymer) of ethylene and two types of α-olefins, or a copolymer of ethylene, α-olefin, and unsaturated carboxylic acid (acrylic acid, methacrylic acid, maleic acid, etc.) may be used. + , K. + , Ag + , Cu 2+ , Ba 2+ , Zn2+ , Fe 2+ Also usable are those crosslinked with metal ions (ionomers) such as those mentioned above.

[0063] The ethylene polymers may be used alone or in combination of two or more. Among the above-mentioned ethylene polymers, from the viewpoints of the balance of physical properties, reactivity with a crosslinking agent, and moldability, it is preferable to use an ethylene-α-olefin copolymer containing ethylene and an α-olefin as the ethylene polymer, more preferably an ethylene-α-olefin copolymer consisting of ethylene and an α-olefin having 3 to 10 carbon atoms, even more preferably an ethylene-α-olefin copolymer consisting of ethylene and an α-olefin having 3 to 6 carbon atoms, and even more preferably an ethylene-α-olefin copolymer consisting of ethylene and propylene or 1-butene having 3 to 4 carbon atoms. Ethylene-α-olefin copolymers can be obtained by known polymerization methods, such as polymerizing selected monomers in an inert solvent such as hexane, heptane, toluene, or xylene using a polymerization catalyst such as a Ziegler-Natta catalyst or a metallocene catalyst.

[0064] Ethylene-polar monomer copolymers are copolymers containing ethylene and polar monomers as structural units. The polar monomer is not particularly limited, and known ones can be used. Examples include unsaturated carboxylic acids, their salts, esters, amides, vinyl esters, and carbon monoxide. More specifically, examples include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, fumaric acid, itaconic acid, monomethyl maleate, monoethyl maleate, maleic anhydride, and itaconic anhydride; salts of these unsaturated carboxylic acids with monovalent metals such as lithium, sodium, and potassium, and salts of polyvalent metals such as magnesium, calcium, and zinc; unsaturated carboxylic acid esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, n-butyl acrylate, isooctyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, and dimethyl maleate; vinyl esters such as vinyl acetate and vinyl propionate; carbon monoxide; and sulfur dioxide.

[0065] The ethylene-polar monomer copolymer is not particularly limited, and known copolymers can be used. Examples include ethylene-unsaturated carboxylic acid copolymers such as ethylene-acrylic acid copolymer and ethylene-methacrylic acid copolymer; ionomers in which the carboxyl groups of the ethylene-unsaturated carboxylic acid copolymer have been partially or completely neutralized with the above-mentioned metals; ethylene-unsaturated carboxylic acid ester copolymers such as ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-isobutyl acrylate copolymer, and ethylene-n-butyl acrylate copolymer; ethylene-unsaturated carboxylic acid ester-unsaturated carboxylic acid copolymers such as ethylene-isobutyl acrylate-methacrylic acid copolymer and ethylene-n-butyl acrylate-methacrylic acid copolymer, and ionomers in which the carboxyl groups of the copolymers have been partially or completely neutralized with the above-mentioned metals; and ethylene-vinyl ester copolymers such as ethylene-vinyl acetate copolymer. Among these, copolymers of ethylene with polar monomers selected from unsaturated carboxylic acids, salts thereof, esters thereof, and vinyl acetate are particularly preferred, and ethylene-(meth)acrylic acid copolymers or ionomers thereof, ethylene-(meth)acrylic acid-(meth)acrylic acid ester copolymers or ionomers thereof, and ethylene-vinyl acetate copolymers are particularly preferred, with ethylene-vinyl acetate copolymers being more preferred.

[0066] The ethylene-polar monomer copolymer preferably has a polar monomer content of 1 to 50 mass %, more preferably 5 to 45 mass %, although this varies depending on the type of polar monomer.

[0067] When the ethylene-polar monomer copolymer used as component (B) in the foam of this embodiment is an ethylene-vinyl acetate copolymer, the vinyl acetate (VA) content in the ethylene-vinyl acetate copolymer is typically 10 to 45% by mass, preferably 15 to 35% by mass, and more preferably 15 to 30% by mass. The higher the VA content, the lower the hardness and the higher the resilience of the foam of this embodiment. On the other hand, the tear strength, compression set, and thermal dimensional stability tend to deteriorate. From the viewpoint of the balance of these properties, the vinyl acetate content in the ethylene-vinyl acetate copolymer is preferably within the above-mentioned range.

[0068] In the foam of the present embodiment, as the component (B), one type of ethylene-polar monomer copolymer may be used alone, or two or more types may be used in combination.

[0069] Examples of polyamide polymers include, but are not limited to, polyamide resins such as polyamide 6, polyamide 11, polyamide 12, polyamide 66, and polyamide 610, and polyamide elastomers. Examples of polyester polymers include, but are not limited to, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, and polyester elastomers. Examples of polyurethane polymers include, but are not limited to, polyurethane polymers such as polyester polyurethane resins and polyether polyurethane resins, polyurethane elastomers, and the like.

[0070] The content of component (B) in the resin composition for foam of this embodiment is preferably 10 to 95 parts by mass per 100 parts by mass of the expandable polymer in the resin composition for foam. It is more preferably 30 to 90 parts by mass, and even more preferably 50 to 85 parts by mass. By using component (B) in this amount, the foam of this embodiment tends to have an excellent balance between resilience and tear strength, and excellent dimensional stability against heat.

[0071] The content of the foamable polymer in the resin composition for foam of the present embodiment is preferably 50% by mass or more from the viewpoint of resilience, and is preferably 80% by mass or less from the viewpoint of weight reduction. The content is more preferably 85 to 100% by mass, and even more preferably 90 to 100% by mass.

[0072] <Other resins> The foam of the present embodiment may contain other resins in addition to the ethylene polymer, ethylene-polar monomer copolymer, polyamide polymer, polyester polymer, and polyurethane polymer described as the above-mentioned component (A) and component (B). Examples of other resins include, but are not limited to, fluorine-based polymers such as fluorine resins and fluorine rubber; polyvinyl chloride resin; acrylic resins such as polymethyl methacrylate; silicone elastomers; butadiene rubber (BR); isoprene rubber (IR); chloroprene (CR); natural rubber (NR); acrylonitrile butadiene rubber (NBR); butyl rubber (IIR); polypropylene resins such as propylene homopolymer (homo PP), random polypropylene resin (random PP), and block polypropylene resin (block PP); cyclic olefin polymer (COP); cyclic olefin copolymer (COC); polystyrene resin, acrylonitrile styrene resin (AS resin), and acrylonitrile butadiene styrene resin (ABS resin).

[0073] <(D) Crosslinking Agent> The foam of the present embodiment is preferably a crosslinked product. The crosslinking method is not particularly limited, but examples thereof include crosslinking using a crosslinking agent. That is, the resin composition used for the foam of the present embodiment preferably contains a crosslinking agent (D) (hereinafter, sometimes referred to as component (D)). The crosslinking agent is not particularly limited, and known crosslinking agents can be used, and organic peroxides are preferred. For example, 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, t-butylcumyl peroxide, etc. These may be used alone or in combination of two or more. Among these, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di-(t-butylperoxy)hexane, and 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane are preferred from the viewpoint of reactivity.

[0074] The content of the (D) crosslinking agent is not particularly limited, but is preferably 0.01 to 20 parts by mass, more preferably 0.05 to 15 parts by mass, and even more preferably 0.1 to 10 parts by mass, relative to 100 parts by mass of the expandable polymer in the foam of this embodiment. By adjusting the content to such an extent, a foam having an excellent balance of various physical properties can be obtained.

[0075] <(E) Foaming Agent> The foam of this embodiment is foamed using a foaming agent. The component (E) is not particularly limited, and known ones can be used. When the foam of the present embodiment is obtained by chemical foaming, examples of the chemical foaming agent include, but are not limited to, azo compounds such as azodicarbonamide (ADCA), 1,1'-azobis(1-acetoxy-1-phenylethane), dimethyl-2,2'-azobisbutyrate, dimethyl-2,2'-azobisisobutyrate, 2,2'-azobis(2,4,4-trimethylpentane), 1,1'-azobis(cyclohexane-1-carbonitrile), and 2,2'-azobis[N-(2-carboxyethyl)-2-methyl-propionamidine]; Examples of suitable blowing agents include nitroso compounds such as N,N'-dinitrosopentamethylenetetramine (DPT); hydrazine derivatives such as 4,4'-oxybis(benzenesulfonylhydrazide) and diphenylsulfone-3,3'-disulfonylhydrazide; semicarbazide compounds such as p-toluenesulfonylsemicarbazide; organic thermal decomposition type blowing agents such as trihydrazinotriazine; bicarbonates such as sodium hydrogencarbonate and ammonium hydrogencarbonate, carbonates such as sodium carbonate and ammonium carbonate; nitrites such as ammonium nitrite, and inorganic thermal decomposition type blowing agents such as hydrogen compounds. Furthermore, when the foam of the present embodiment is obtained by physical foaming, examples of the physical foaming agent include, but are not limited to, organic physical foaming agents such as various aliphatic hydrocarbons, such as methanol, ethanol, propane, butane, pentane, and hexane, and inorganic physical foaming agents, such as air, carbon dioxide, nitrogen, argon, and water. The physical foaming agent is a liquefied gas or a supercritical fluid, which foams upon pressure reduction or heating. Among these, azodicarbonamide (ADCA) and sodium bicarbonate are preferred from the viewpoints of cost and reactivity. In view of improving the resilience of the foam of this embodiment, a physical foaming agent is preferred, and in view of reducing the odor of the foam, an inorganic physical foaming agent is preferred, and among them, nitrogen and carbon dioxide are preferred from the viewpoints of availability and ease of handling. Nitrogen is preferred from the viewpoint of obtaining a uniform foam.

[0076] The content of component (E) in the resin composition for foam of this embodiment is not particularly limited and may be adjusted depending on the expansion ratio and foaming conditions, but when a chemical foaming agent is used, the content is preferably 0.1 to 30 parts by mass, more preferably 0.2 to 25 parts by mass, and even more preferably 0.3 to 20 parts by mass, per 100 parts by mass of the expandable polymer in the resin composition for foam of this embodiment. By adjusting the content to such an extent, a foam having a low specific gravity and an excellent balance of various physical properties can be obtained. When a physical foaming agent is used, the content can be adjusted by adjusting the temperature and pressure when the expandable polymer is mixed with or impregnated into the physical foaming agent.

[0077] <(F) Additives> The resin composition for foam of this embodiment may contain, in addition to the above-mentioned components (A) to (E), an additive (F) (hereinafter sometimes referred to as component (F)) as necessary. Examples of additives include, but are not limited to, various additives such as crosslinking aids, processing aids, fillers, heat stabilizers, weather stabilizers, flame retardants, hydrochloric acid absorbents, pigments, etc. These additives may be used alone or in combination of two or more.

[0078] Examples of the crosslinking aid include, but are not limited to, metal oxides other than zinc, such as zinc oxide, magnesium oxide, and lead monoxide; metal hydroxides, such as calcium hydroxide; fatty acids, such as stearic acid and oleic acid; sulfur; peroxy crosslinking aids, such as p-quinone dioxime, p,p'-dibenzoylquinone dioxime, N-methyl-N-4-dinitrosoaniline, nitrosobenzene, diphenyl guanidine, and trimethylolpropane-N,N'-m-phenylenedimaleimide; or polyfunctional methacrylate monomers, such as divinylbenzene, triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and allyl methacrylate; and polyfunctional vinyl monomers, such as vinyl butyrate and vinyl stearate. In particular, zinc oxide, triallyl cyanurate (TAC), and triallyl isocyanurate (TAIC) are preferred because of their excellent crosslinking promoting effect. It is preferable to use at least zinc oxide as the crosslinking aid.

[0079] As the processing aid, a wide variety of processing aids that are generally compounded in rubber can be used. Examples of processing aids include, but are not limited to, ricinoleic acid, stearic acid, palmitic acid, lauric acid, barium stearate, zinc stearate, calcium stearate, zinc laurate, and esters thereof. Among these, stearic acid is preferred.

[0080] Examples of fillers include, but are not limited to, clay, titanium oxide, silicon oxide, zinc oxide, talc, calcium carbonate, and the like.

[0081] Examples of heat stabilizers include, but are not limited to, phosphorus-based heat stabilizers such as Irgafos 168, lactone-based heat stabilizers such as HP-136, and sulfur-based heat stabilizers.

[0082] Examples of the weathering stabilizer include, but are not limited to, hindered phenol-based weathering stabilizers, phosphite-based weathering stabilizers, and thioether-based weathering stabilizers.

[0083] Examples of the flame retardant include, but are not limited to, red phosphorus flame retardants, halogen flame retardants, organic phosphate ester flame retardants, inorganic flame retardants, and the like.

[0084] Examples of hydrochloric acid absorbents include, but are not limited to, calcium stearate.

[0085] Examples of pigments include, but are not limited to, azo pigments, phthalocyanine pigments, oxide pigments such as titanium oxide, molybdic chromoate pigments, selenium sulfide compounds, ferrocyanide compounds, and inorganic pigments such as carbon black.

[0086] (Method of manufacturing a resin composition for foam) The resin composition for foam of this embodiment can be produced by melt-mixing in a kneader component (A): a conjugated diene polymer; if necessary, component (B): a foamable polymer other than component (A), such as at least one selected from the group consisting of an ethylene polymer, an ethylene-polar monomer copolymer, a polyamide polymer, a polyester polymer, and a polyurethane polymer, or other resin; component (D): a crosslinking agent; component (E): a foaming agent; and component (F): an additive, in a predetermined ratio.

[0087] The melt-mixing method is not particularly limited, and known methods can be used. For example, a melt-mixing method using an extruder such as a single-screw extruder, a twin-screw extruder, or a multi-screw extruder, a Henschel mixer, a Banbury mixer, a roll, a kneader, or the like can be used. These methods may be used in combination, and an example is a method in which the components are mixed in a Banbury mixer, and then the foam mixture is stretched with a roll to form a sheet. Alternatively, a method in which the components are dissolved or dispersed and mixed, and then the solvent is removed can be used. From the viewpoint of productivity, a melt-mixing method using an extruder is preferred.

[0088] The order of mixing the components used in the resin composition for foam of this embodiment is not particularly limited, and for example, the foamable polymer component consisting of component (A), component (B), and other resins that constitute the resin composition for foam may be mixed in advance, and then component (D), component (E), component (F), etc. may be added and mixed as needed. These may be added and mixed stepwise using the same equipment, for example, by adding and mixing stepwise in a mixing process using a Banbury mixer, or by adding and mixing stepwise by shifting the feed positions of each component in a twin-screw extruder.

[0089] The shape of the resin composition for foam of the present embodiment is not particularly limited, and it can be molded into any desired shape as appropriate. For example, it can be in the form of pellets, sheets (sometimes called films), strands, chips, etc. For example, if necessary, the components can be mixed in a granulator or the like to form pellets. When the resin composition for foam of this embodiment is molded into a sheet, the method is not particularly limited, and known methods can be used. Examples include a method of molding pellets of the resin composition for foam of this embodiment into a sheet using an extruder or a calendar molding machine; a method of kneading the components of the resin composition using a Brabender or the like and then molding them into a sheet using a calendar roll; a method of forming into a sheet using a press molding machine; and a method of kneading using an extruder and then passing through a T-die or annular die to form into a sheet. This method allows the preparation of an uncrosslinked, unfoamed foamable sheet.

[0090] (Foam applications) The foam of this embodiment can be used as a sheet (sometimes called a film), injection-molded products of various shapes, blow-molded products, pressure-molded products, vacuum-molded products, extrusion-molded products, and the like. In particular, the foam of this embodiment has excellent, continuous resilience and durability even when lightweight, and therefore can be widely used in automobiles, construction, various packaging materials, daily necessities, and the like. In particular, it can be suitably used as a material for shoe soles, shoe midsoles, insoles, and unisoles for the purpose of imparting various functions to shoes. In particular, it can be suitably used as a midsole that requires light weight and resilience.

[0091] [Method for producing foam] The foam of this embodiment can be produced by the following production method. That is, the method for producing a foam of this embodiment includes: (A) a step of kneading a resin composition containing a conjugated diene-based polymer containing conjugated diene monomer units and vinyl aromatic monomer units to obtain a kneaded mixture; (B) a step of molding the kneaded mixture to obtain a molded product; (C) a step of mixing the kneaded mixture or the molded product with a foaming agent and / or impregnating the kneaded mixture and / or the molded product with a foaming agent to obtain a foaming agent mixture; and (D) a step of foaming the foaming agent mixture by reducing pressure and / or increasing temperature. In the method for producing a foam, steps (a) to (d) may be consecutive, or the order of the steps may be changed as appropriate, and steps other than steps (a) to (d) may be inserted before, after, or simultaneously with each step. The steps other than steps (a) to (d) include, for example, a step of storing the molded body after step (b).

[0092] In the method for producing a foam of this embodiment, at least two of the steps (a) to (d) may be carried out simultaneously. An example of the case where step (a) and step (c) are carried out simultaneously is where a chemical foaming agent is mixed into the resin composition in step (a). An example of the case where the steps (b) and (d) are carried out simultaneously after the step (c) is a case where a kneaded material containing a foaming agent is molded while being foamed to obtain a foam.

[0093] The method for producing a foam of the present embodiment may further include a step (e) of crosslinking any one selected from the group consisting of the kneaded product, the molded product, and the foam mixture. For example, steps (e) and (b) may be performed simultaneously to obtain a crosslinked molded product, and then in step (c) the crosslinked molded product may be impregnated with a physical foaming agent under high pressure to obtain a foamed product in step (d). The crosslinking step (e) can be appropriately combined when the above-mentioned steps (a) and (c) are carried out simultaneously, or when the steps (b) and (d) are carried out simultaneously. For example, after mixing a foaming agent into the kneaded product (step (a) and step (c)), the step (e) of crosslinking, the step (d) of foaming, and the step (b) of obtaining a molded body can be carried out simultaneously. In particular, the method of foaming a crosslinked molded article with a physical foaming agent after obtaining the crosslinked molded article can improve the resilience of the foam. Compared to the method using a chemical foaming agent, the foaming temperature can be lowered, domains consisting of polymer chains of vinyl aromatic monomer units are easily formed, and stronger physical crosslinks are formed, which tends to improve the resilience of the foam.

[0094] In the foam manufacturing method of the present embodiment, the crosslinking method when carrying out the crosslinking step (e) is not particularly limited, and known methods can be used. For example, there is a method in which a crosslinking agent (D) is blended into the resin composition and heated to crosslink, and a method in which this method is used in combination with a method in which energy rays such as electron beams or radiation are irradiated.

[0095] In the method for producing a foam according to the present embodiment, foaming can be performed using a blowing agent that is a supercritical fluid. Examples of such foaming methods include (1) a method in which an uncrosslinked or crosslinked sheet, pellets, or the like is prepared, placed in a pressure-resistant container, and subjected to pressure and temperature to impregnate the sheet or pellets with a supercritical gas as a blowing agent, followed by foaming by reducing the pressure and / or increasing the temperature; (2) a method in which pellets mixed with a crosslinking agent are placed in an injection molding machine, and the pellets are impregnated with a supercritical gas as a blowing agent in the cylinder, thereby foaming simultaneously with extrusion molding or injection molding; and (3) a method in which pellets not containing a crosslinking agent are placed in an injection molding machine, and the pellets are impregnated with a supercritical gas as a blowing agent in the cylinder, thereby foaming simultaneously with extrusion molding or injection molding. In the foaming method (1), the foam is impregnated with a foaming agent after molding without going through a resin composition containing both a crosslinking agent and a foaming agent. Therefore, in this method, the resin composition obtained immediately after the foaming agent impregnation, i.e., the resin composition immediately before the foaming step, corresponds to the resin composition for foam of this embodiment. This method can also produce the foam of this embodiment. The crosslinking may be performed simultaneously with molding or after molding. For example, an uncrosslinked resin composition for foam containing a crosslinking agent may be placed in a mold heated to a temperature at which the crosslinking agent reacts, and molding and crosslinking may be performed simultaneously. Alternatively, an uncrosslinked sheet may be molded at a temperature at which the crosslinking agent does not react, and then crosslinked by irradiating it with energy rays. In other words, the molding step, crosslinking step, and foaming step do not need to be independent steps. Crosslinking may be performed simultaneously with molding, followed by foaming, or both crosslinking and foaming may be performed after molding.

[0096] The foaming step in the method for producing a foam of the present embodiment is not particularly limited, and can be carried out using a known method such as press molding, injection molding, or reducing the pressure and / or increasing the temperature of a foaming agent mixture mixed with or impregnated with a physical foaming agent. For example, injection foam molding may be performed using a pelletized resin composition for foam and a predetermined mold. When a physical foaming agent is used, for example, a supercritical physical foaming agent, such as nitrogen gas or carbon dioxide, may be injected into a cylinder of an injection molding machine, and the supercritical physical foaming agent may be dispersed, melted, and mixed with a molten resin composition for foam containing components other than the foaming agent in the cylinder, followed by injection molding.

[0097] Here, an example of foaming a cross-linkable foamable sheet obtained by forming the resin composition for foam of the present embodiment into a sheet will be described. In this case, the cross-linked foamable sheet corresponds to the foaming agent mixture. The cross-linked foamable sheet is cut into a size in the range of 1.0 to 1.2 times the volume of the mold, and inserted into the mold maintained at 120 to 200°C. The mold clamping pressure is 30 to 300 kgf / cm. 2 The crosslinked foamable sheet is pressurized and melted under conditions of 5 to 90 minutes, and the holding time is set to 5 to 90 minutes to allow the crosslinking reaction and decomposition of the foaming agent. The mold is then opened and foamed to produce a primary crosslinked foam. The shape of the mold is not particularly limited, but can be any shape that will yield a sheet. This mold preferably has a completely sealed structure to prevent gases generated during melting of the resin or decomposition of the foaming agent from escaping to the outside. From the viewpoint of mold releasability, a mold with a tapered inner surface is preferred.

[0098] In the method for producing a foam according to the present embodiment, a foam resin composition containing no blowing agent can be used. In this case, the resin composition in the form of a sheet is crosslinked and molded in the above-described steps to obtain an expandable crosslinked molded article. Thereafter, the expandable cross-linked molded body is impregnated in an autoclave with a blowing agent that has been brought to a supercritical state at a temperature equal to or higher than the Tg of the resin that constitutes the expandable cross-linked molded body and at a pressure equal to or higher than the pressure at which the blowing agent becomes a supercritical fluid. If foaming is performed by reducing the pressure, the pressure is rapidly reduced in an autoclave at a temperature equal to or higher than the Tg of the resin that constitutes the molded body to produce a primary crosslinked foam.If foaming is performed by increasing the temperature, the molded body is cooled in the autoclave to a temperature equal to or lower than the Tg of the resin that constitutes the molded body, and the gas-impregnated molded body is removed and heated to produce a primary crosslinked foam.

[0099] In the foam manufacturing method of this embodiment, the primary crosslinked foam may be compression molded to give a predetermined shape, if necessary. The compression molding conditions are not particularly limited, but from the viewpoint of the reaction rate of the crosslinking agent and the foaming agent, a mold temperature of 120 to 200°C and a mold clamping pressure of 30 to 300 kgf / cm are preferred. 2 It is preferable that the compression time is 5 to 60 minutes and the compression ratio is in the range of 1.1 to 3.0. [Example]

[0100] EXAMPLES Hereinafter, the present embodiment will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples and comparative examples. In the examples and comparative examples, foams were prepared by the methods described below, and the physical properties and characteristics were compared. The physical properties of the conjugated diene polymer and the physical properties and characteristics of the foam were measured as follows.

[0101] [Physical Properties of Conjugated Diene Polymers] (MFR) The fluidity of the conjugated diene polymer was measured in accordance with ISO 1133. Specifically, the melt flow rate (MFR) was measured at 230°C under a load of 2.16 kg.

[0102] (Styrene content in component (A)) The styrene content of component (A) was measured by proton nuclear magnetic resonance ( 1 H-NMR was used for the measurement. The measurement equipment was a JNM-LA400 (manufactured by JEOL), the solvent was deuterated chloroform, the sample concentration was 50 mg / mL, the observation frequency was 400 MHz, tetramethylsilane was used as the chemical shift standard, the pulse delay was 2.904 seconds, the number of scans was 64, the pulse width was 45°, and the measurement temperature was 26°C. The styrene content was calculated using the integrated value of the total styrene aromatic signal from 6.2 to 7.5 ppm in the spectrum.

[0103] (Total amount of 1,2-vinyl bonds and 3,4-vinyl bonds in the conjugated diene monomer units in component (A)) The total amount of 1,2-vinyl bonds and 3,4-vinyl bonds in the conjugated diene monomer units in component (A) was determined by proton nuclear magnetic resonance ( 1 H-NMR was used for the measurement. The measurement conditions and the method of processing the measurement data were the same as those for the above-mentioned method of measuring the styrene content. The total amount of 1,2-vinyl bonds and 3,4-vinyl bonds was calculated from the integral values ​​of the signals assigned to 1,4-vinyl bonds, 1,2-vinyl bonds, and 3,4-vinyl bonds. 1 After calculating the integral value per H, calculation was performed using (1,2-vinyl bond + 3,4-vinyl bond) / (1,2-vinyl bond + 3,4-vinyl bond + 1,4-vinyl bond).

[0104] (Hydrogenation rate of component (A)) The hydrogenation rate of component (A) was measured by proton nuclear magnetic resonance ( 1 H-NMR). The measurement conditions and the method of processing the measurement data were the same as those for the above-mentioned method of measuring the styrene content. The hydrogenation rate was calculated by calculating the integral values ​​of the signals derived from the remaining double bonds at 4.5 to 5.5 ppm and the signals derived from the hydrogenated conjugated dienes, and then calculating the ratio thereof.

[0105] (peak top molecular weight) The highest peak top molecular weight of the conjugated diene polymer was measured by gel permeation chromatography (GPC) (apparatus: manufactured by Waters) under the following conditions. From the obtained chromatogram, the molecular weight of the peak top of the conjugated diene polymer was determined using a calibration curve (prepared using the peak molecular weight of the standard polystyrene) obtained from the measurement of commercially available standard polystyrene. <Measurement conditions> GPC: ACQUITY APC system (manufactured by Nihon Waters Co., Ltd.) System (measurement and analysis) software: Empower3 Detector: Refractive index (RI) detector Refractive index unit full scale: 500μRIU Output full scale: 2000mV Sampling rate: 10 points / sec Column: ACQUITY APC XT125 (4.6 mm x 150 mm); 1 ACQUITY APC XT200(4.6mm×150mm);1 piece ACQUITY APC XT900(4.6mm×150mm);1 piece ACQUITY APC XT450(4.6mm×150mm);1 piece Solvent: tetrahydrofuran (THF) Flow rate: 1.0mL / min Concentration: 0.1mg / mL Column temperature: 40°C Injection volume: 20μL

[0106] (vinyl hydrogenation rate) The hydrogenation rates (%) of the 1,2-vinyl bonds and 3,4-vinyl bonds in the conjugated diene monomer units in component (A) were measured by NMR. The NMR method is described below. After hydrogenation, 30 mg of the conjugated diene polymer was dissolved in 1 g of deuterated chloroform, and the resulting sample was analyzed by proton nuclear magnetic resonance ( 1 H-NMR) was measured. In the measurement results obtained, symbols X1, X2, X3, X4, X5, X6, and X7 are defined as follows. X1: The area value of the range surrounded by the line connecting the positions of the smallest signal intensity in the 7.26 ppm to 7.25 ppm section and the 7.27 ppm to 7.26 ppm section, with 7.26 ppm as the center, and the NMR spectrum. X2: Area value of the range enclosed by the line connecting the signal positions of 8.0 ppm and 6.0 ppm and the NMR spectrum X3: The area value between the chemical shift of the position with the smallest signal intensity between 5.2 ppm and 4.9 ppm and 4.0 ppm, among the area values ​​enclosed by the line connecting the signal positions of 6.0 ppm and 4.0 ppm and the NMR spectrum. X4: The area value between the chemical shift of the position with the smallest signal intensity between 5.2 ppm and 4.9 ppm and 6.0 ppm, among the area values ​​enclosed by the line connecting the signal positions of 6.0 ppm and 4.0 ppm and the NMR spectrum. X5: The area enclosed by the line connecting the signal positions of 4.0 ppm and 0.3 ppm and the NMR spectrum, the area within a range of 0.3 ppm from the chemical shift of the position with the smallest signal intensity among the valleys of the NMR spectrum between 1.05 ppm and 0.85 ppm (however, if there is no valley between 1.05 ppm and 0.85 ppm, the area within a range of 0.3 ppm from the chemical shift of the position with the smallest signal intensity among the valleys of the NMR spectrum between 1.05 ppm and 0.85 ppm is used). X6: The area enclosed by the line connecting the signal positions at 4.0 ppm and 0.3 ppm and the NMR spectrum X7: The area value of the range surrounded by the line connecting the positions of the smallest signal intensity in each of the sections from 1.49 ppm to 1.50 ppm and from 1.50 ppm to 1.51 ppm, with 1.50 ppm as the center, and the NMR spectrum (however, if the line connecting the positions of the smallest signal intensity is above the NMR spectrum, it is set to 0). The hydrogenation rate of 1,2-vinyl bonds and 3,4-vinyl bonds in the conjugated diene monomer units in component (A) is the proportion of polymer units of hydrogenated 1,2-vinyl bonds and 3,4-vinyl bonds to the total of hydrogenated 1,2-vinyl bonds and 3,4-vinyl bonds and non-hydrogenated 1,2-vinyl bonds and 3,4-vinyl bonds, and was calculated using the following formulas (6) to (8). Area value per proton of hydrogenated 1,2-vinyl bond and 3,4-vinyl bond monomer units (hydrogenated vinyl) =X5 / 3 (6) Area value per proton of unhydrogenated 1,2-vinyl bond and 3,4-vinyl bond monomer units (unhydrogenated vinyl) =X3 / 2 (7) Hydrogenation rate (%) of 1,2-vinyl bonds and 3,4-vinyl bonds in the conjugated diene monomer units of component (A) = (hydrogenated vinyl) / {(hydrogenated vinyl) + (unhydrogenated vinyl)} × 100 (8)

[0107] [Physical properties and characteristics of foam] ((1) Foam specific gravity) A secondary crosslinked foam was used as the foam, and a circle with a diameter of 1.4 cm and a thickness of 1 cm was punched out to prepare a test piece. The specific gravity of the foam was measured using an electronic hydrometer (MD-200S, manufactured by Aluminum Farm Mirage Co., Ltd.).

[0108] ((2) Rebound Resilience) A secondary cross-linked foam was used as the foam, and the rebound resilience was calculated in accordance with JIS K6255 by measuring the rebound height (= L) of a 15g iron ball dropped from a height of 40cm (= L0) at 23°C and using the following formula. Rebound resilience (%) = (L / L0) x 100

[0109] ((3) split tear strength) A secondary cross-linked foam was used as the foam, and a test piece measuring 2 cm wide x 10 cm long x 1 cm thick was cut into the middle of the test piece in the vertical direction, and the test piece was clamped with a chuck distance of approximately 4 cm. The tear strength was measured in the thickness direction at 100 mm / min using a universal tensile / compression testing machine (TG-5kN, manufactured by NMB Minebea Co., Ltd.).

[0110] ((4) Compression set) A secondary crosslinked foam was used as the foam, and a circle with a diameter of 2.6 cm was punched out to prepare a test piece. The test piece was compressed to 50% of its thickness, held at 50°C for 6 hours, and then the pressure was released. After leaving the test piece to stand for 1 hour, the thickness was measured, the magnitude of residual strain was measured, and the compression set (%) was evaluated.

[0111] ((5) Repeated compression set) A secondary cross-linked foam was used as the foam, and in accordance with JIS K6400-4, a 20mm thick foam was punched out into a 50mm square to serve as a test piece. This was compressed 80,000 times continuously at 23°C to 50% of its thickness, and then left to stand for 1 hour. The residual strain after this was assessed from the appearance and classified according to the following criteria to evaluate durability when repeated deformation occurs. <Evaluation criteria> ⊚: Almost no residual distortion. ◯: Residual distortion is small. △: Residual distortion is moderate. ×: Residual strain is large.

[0112] (6) Uniformity of foam The appearance of the secondary crosslinked foam was classified according to the following criteria, and the uniformity of the foam was evaluated. <Evaluation criteria> ○: No visible unevenness in foaming. ×: There is uneven foaming that can be seen with the naked eye.

[0113] ((7)C hardness) The C hardness (Asker C) of the secondary crosslinked foam was measured using an ASKER C hardness tester (CL-150, Asker C, manufactured by Kobunshi Keiki Co., Ltd.) and the value was read after 3 seconds. The average value (arithmetic mean) of the five points was then calculated as the C hardness.

[0114] (8) Cell size of foam A cross section of the secondary cross-linked foam was cut out, and the surface was observed using a scanning electron microscope. The cross-sectional image obtained was then binarized. Based on the binarized data, the area of ​​each cell was calculated, and the diameter was determined assuming that the cell was circular. The average diameter of the cells included in the image was then used to measure the cell size.

[0115] Materials used in Examples and Comparative Examples The (A) conjugated diene copolymer, (B) ethylene polymer and / or ethylene-polar monomer copolymer, (D) crosslinking agent, (E) blowing agent, and (F) additive used in the examples and comparative examples are shown below.

[0116] (Preparation of hydrogenation catalyst) In the examples and comparative examples described later, the hydrogenation catalyst used in producing the conjugated diene polymer was prepared by the following method. A reaction vessel equipped with a stirrer was purged with nitrogen and charged with 1 L of dried and purified cyclohexane. Next, 100 mmol of bis(η5-cyclopentadienyl)titanium dichloride was added. While thoroughly stirring, an n-hexane solution containing 200 mmol of trimethylaluminum was added, and the mixture was allowed to react at room temperature for approximately 3 days. This produced a hydrogenation catalyst.

[0117] ((A) Conjugated Diene Polymer) <(A1) Hydrogenated Styrene-Butadiene-Styrene Triblock Copolymer> Styrene content 10% by mass, 1,2-vinyl bond content in 1,3-butadiene units: 35% by mass; Hydrogenation rate of double bonds of 1,3-butadiene units: 98% Peak top molecular weight: 120,000 [Method of producing conjugated diene polymer A1] Batch polymerization was carried out in the following manner using a 100 L tank reactor equipped with a stirrer and a jacket. First, 36 L of cyclohexane was charged into a reactor, and the temperature was adjusted to 50°C. After that, 0.095 parts by mass of n-butyllithium (hereinafter also referred to as "Bu-Li") and 0.35 moles of N,N,N',N'-tetramethylethylenediamine (hereinafter also referred to as "TMEDA") per mole of Bu-Li were added relative to 100 parts by mass of the total amount of butadiene monomer and styrene monomer (hereinafter referred to as "total monomers") charged into the reactor. Next, 5.0 parts by mass of styrene was added over 5 minutes, and then the reaction was continued for another 15 minutes (the temperature reached 65°C due to the polymerization reaction). At this point, the polymer solution was sampled and the polymerization conversion of styrene was measured, which was found to be 100%. Next, a cyclohexane solution (concentration: 40 parts by mass) containing 90.0 parts by mass of butadiene was continuously added to the reactor at a constant rate over 10 minutes, and the reaction was continued for 10 minutes. After the reaction temperature reached a maximum of 86° C., the reaction was continued for another 3 minutes. At this point, the polymer solution was sampled and the polymerization conversion of butadiene was measured, which was found to be 100%. Next, 5.0 parts by mass of styrene was added over 5 minutes, and the mixture was then allowed to react for another 5 minutes. Thereafter, 0.95 moles of methanol was added per mole of Bu-Li to terminate the polymerization reaction, thereby obtaining a copolymer. To the resulting copolymer, the hydrogenation catalyst was added in an amount of 50 ppm in terms of titanium per 100 parts by mass of copolymer, and a hydrogenation reaction was carried out at a hydrogen pressure of 0.9 MPa and a temperature of 90° C. for 45 minutes. Thereafter, 0.3 parts by mass of octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate was added as a stabilizer relative to 100 parts by mass of the copolymer to obtain a conjugated diene polymer A1. The tan δ peak temperature measured by dynamic viscoelasticity measurement was −25° C. or lower. The tan δ peak temperature was measured using an ARES-G2 (manufactured by TA Instruments). A 2 mm thick sheet of component (A) was compression molded at approximately 200°C, the temperature at which component (A) melts, and the sheet was cut into a 12.6 x 40 mm strip. The sample was heated from the measurement temperature of -100°C at a rate of 3°C / min while applying a 0.5% strain, and the tan δ at each temperature was plotted to obtain the peak temperature.

[0118] <(A2 to A23) Hydrogenated Block Copolymers> [Method of producing conjugated diene polymers A2 to A23] The block copolymers before hydrogenation were obtained by producing the conjugated diene polymer A1 under the same conditions as those for the conjugated diene polymer A1, except for the block structure, styrene content, Bu-Li content, and TMEDA content shown in Tables 1 and 2. The hydrogenation rate was then adjusted by adjusting the amount of hydrogenation catalyst, the amount of hydrogen, and the hydrogenation reaction time. A7, A8, and A9 were obtained by blending an unhydrogenated block copolymer with a 100% hydrogenation rate. The tan δ peak temperatures measured under the same dynamic viscoelasticity measurement conditions as those for the conjugated diene polymer A1 were all −25° C. or lower.

[0119] The component (A) used in the examples and comparative examples is shown in Table 1 below. In the "block structures" of the component (A) shown in Tables 1 and 2 below, "a" refers to a polymer block mainly composed of styrene, and "b" refers to a polymer block mainly composed of butadiene.

[0120] [Table 1]

[0121] [Table 2]

[0122] ((B) Ethylene-based polymer and / or ethylene-polar monomer copolymer) (B1) Ethylene-vinyl acetate copolymer (HANWHA, product name "EVA1317", VA content 22%) (B2) Ethylene-vinyl acetate copolymer (manufactured by Formosa Plastic, product name "EVA7470", VA content 28%) (B3) TAFMER DF810 (Mitsui Chemicals, ethylene-1-butene copolymer)

[0123] ((D) Crosslinking Agent) Dicumyl peroxide (manufactured by NOF Corporation)

[0124] ((E) Foaming Agent) CELLCOM-JTR (manufactured by KUMYANG), an organic thermal decomposition type foaming agent based on ADCA

[0125] ((F) Additives) (F1) Titanium dioxide (F2) Stearic acid (F3) Zinc oxide (F4) Zinc stearate

[0126] Example 1 40 parts by mass of conjugated diene polymer (A1), 60 parts by mass of ethylene-polar monomer copolymer (B1), 0.8 parts by mass of crosslinking agent (D), 5.0 parts by mass of foaming agent (E), 4 parts by mass of additive (F1), 1 part by mass of additive (F2), and 5 parts by mass of additive (F3) were melt-kneaded using a roll set at 120°C, and then pressurized at 160°C and 100 kgf / cm using a press mold. 2 This primary crosslinked foam was compression molded to a specific gravity of 0.15 to obtain a secondary crosslinked foam. Subsequently, the physical properties and characteristics of this secondary crosslinked foam were measured and evaluated by the above-mentioned methods.

[0127] [Examples 2 to 22, Comparative Example 1] The compositions of Examples 2 to 22 and Comparative Example 1 are shown in Tables 3 and 4. A primary crosslinked foam and a secondarily crosslinked foam were prepared in the same manner as in Example 1 except for the changes shown in Tables 3 and 4, and their physical properties and characteristics were measured and evaluated.

[0128] [Table 3]

[0129] [Table 4]

[0130] Example 23 40 parts by mass of conjugated diene polymer (A1) and 60 parts by mass of ethylene-polar monomer copolymer (B2) were mixed for 9 minutes in a kneader set at 80°C, and then the temperature was raised to 100°C, and 0.6 parts by mass of crosslinking agent (D), 5.0 parts by mass of foaming agent (E), 0.5 parts by mass of additive (F2), 1 part by mass of additive (F3), and 0.5 parts by mass of additive (F4) were added and mixed for 2 minutes. Subsequently, the mixture was kneaded for 10 minutes with a roll set at 65°C, and then the mixture was kneaded using a press mold at 170°C and 150 kgf / cm. 2 This primary crosslinked foam was compression molded using a press mold at 170°C for 10 minutes so that the specific gravity was 0.135, thereby obtaining a secondary crosslinked foam.

[0131] [Examples 24 to 47, Comparative Example 2] The compositions of Examples 24 to 47 and Comparative Example 2 are shown in Tables 5 and 6. A primary crosslinked foam and a secondarily crosslinked foam were prepared in the same manner as in Example 23, except for the changes shown in Tables 5 and 6, and their physical properties and characteristics were measured and evaluated.

[0132] [Table 5]

[0133] [Table 6]

[0134] Example 48 40 parts by mass of conjugated diene polymer (A1) and 60 parts by mass of ethylene-polar monomer copolymer (B2) were mixed for 9 minutes in a kneader set at 80°C, and then the temperature was raised to 100°C, and 0.6 parts by mass of crosslinking agent (D), 0.5 parts by mass of additive (F2), 1 part by mass of additive (F3), and 0.5 parts by mass of additive (F4) were added, and the mixture was mixed for 2 minutes. Thereafter, the mixture was kneaded for 10 minutes with a roll set at 65°C to obtain a kneaded mixture. Then, using a press mold, the temperature is 170℃ and 150kgf / cm 2 Crosslinking was carried out for 10 minutes at 4°C to obtain a crosslinked molded product for foaming. This cross-linked foam was placed in an autoclave, and the autoclave was heated to 135°C and a nitrogen atmosphere of 20 MPa for 2 hours to impregnate the foam with nitrogen. After that, the autoclave was returned to atmospheric pressure to obtain a primary cross-linked foam. A secondary cross-linked foam was obtained by compression molding at 170°C for 10 minutes using a press mold to a specific gravity of 0.135.

[0135] [Examples 49 to 71, Comparative Example 3] The compositions of Examples 49 to 71 and Comparative Example 3 are shown in Tables 7 and 8. A primary crosslinked foam and a secondarily crosslinked foam were prepared in the same manner as in Example 48, except for the changes shown in Tables 7 and 8, and their physical properties and characteristics were measured and evaluated.

[0136] Examples 72 to 75 The compositions of Examples 72 to 75 are shown in Table 9. The resin composition was charged into a supercritical foam injection molding machine (KS306-US1), mixed with nitrogen under high pressure, and injection molded to obtain a foam. The temperatures of the screw and nozzle were 225°C to 245°C, the injection speed was 50 to 90 mm / s, the mold temperature was room temperature, and the mold pressure was 25 bar. The physical properties and characteristics of the obtained foam were measured and evaluated.

[0137] [Table 7]

[0138] [Table 8]

[0139] [Table 9]

[0140] Examples 1 to 75 exhibited an excellent balance of resilience and compression set, which, for example, in running shoes, reduced energy loss and maintained performance even when the shoes were worn for long periods of time. In addition, by keeping the vinyl hydrogenation rate within a specific range, durability against repeated deformation is improved, which in running shoes allows for running with reduced energy loss even after traveling long distances, and maintains the initial comfort for a long period of time. According to the examples, foams can be obtained that exhibit excellent resilience even when lightened, and that also have excellent durability, long-term durability, and continuous resilience. [Industrial Applicability]

[0141] The foam of the present invention has industrial applicability in a wide range of fields, including various molded articles such as automobile parts, civil engineering and construction applications, home appliance parts, shoe midsoles, sporting goods, miscellaneous goods, and stationery.

Claims

1. A foam of a resin composition containing a foamable polymer, The foamable polymer (A) a conjugated diene polymer containing a conjugated diene monomer unit and a vinyl aromatic monomer unit, the content of vinyl aromatic monomer units in the component (A) is 5 to 80 mass %, The conjugated diene monomer units in the component (A) are hydrogenated. Foam.

2. the foam is a foam of a blowing agent mixture containing at least the component (A) and a blowing agent, The foaming agent is a physical foaming agent. The foam of claim 1.

3. the hydrogenation rate of 1,2-vinyl bonds and 3,4-vinyl bonds in the conjugated diene monomer units in the component (A) is 80% or more; 3. The foam according to claim 1 or 2.

4. the hydrogenation rate of the conjugated diene monomer units in the component (A) is 60 to 90 mass%; 3. The foam according to claim 1 or 2.

5. The specific gravity is 0.15 or less.

3. The foam according to claim 1 or 2.

6. The foam cell size is 50 μm or more.

3. The foam according to claim 1 or 2.

7. The resin composition Further containing at least one selected from the group consisting of an ethylene-based polymer, an ethylene-polar monomer copolymer, a polyamide-based polymer, a polyester-based polymer, and a polyurethane-based polymer, 3. The foam according to claim 1 or 2.

8. It is a crosslinked body, 3. The foam according to claim 1 or 2.

9. The peak top molecular weight of the component (A) is 50,000 to 500,000.

3. The foam according to claim 1 or 2.

10. The gas phase of the foam is nitrogen and / or carbon dioxide; 3. The foam according to claim 1 or 2.

11. the total amount of 1,2-vinyl bonds and 3,4-vinyl bonds in the conjugated diene monomer units in the component (A) is 10 to 60 mass%; 3. The foam according to claim 1 or 2.

12. The content of the component (A) is 5 to 70 parts by mass relative to 100 parts by mass of the foamable polymer.

3. The foam according to claim 1 or 2.

13. A shoe sole comprising the foam of claim 1 or 2.

14. Any one selected from the group consisting of a midsole, an insole, and a unisole. The sole of claim 13.

15. (A) a step (a) of kneading a resin composition containing a conjugated diene polymer containing a conjugated diene monomer unit and a vinyl aromatic monomer unit to obtain a kneaded product; a step (b) of molding the kneaded mixture to obtain a molded body; a step (c) of mixing the kneaded product or the molded product with a foaming agent and / or impregnating the kneaded product or the molded product with a foaming agent to obtain a foaming agent mixture; (d) foaming the blowing agent mixture by reducing pressure and / or increasing temperature; have, A method for producing a foam.

16. The step (a) and the step (c) are carried out simultaneously. A method for producing the foam of claim 15.

17. After the step (c), the step (b) and the step (d) are carried out simultaneously. A method for producing the foam according to claim 15 or 16.

18. The method further includes a step (e) of crosslinking any one selected from the group consisting of the kneaded product, the molded product, and the blowing agent mixture. A method for producing the foam according to claim 15 or 16.

19. The method further includes a step (e) of crosslinking any one selected from the group consisting of the kneaded product, the molded product, and the blowing agent mixture. A method for producing the foam of claim 17.

20. After mixing the foaming agent into the kneaded mixture, The step (e) of crosslinking, the step (d) of foaming, and the step (b) of obtaining a molded body are carried out simultaneously. A method for producing the foam of claim 15.

21. The blowing agent is nitrogen or carbon dioxide. A method for producing the foam according to claim 15 or 16.

22. The blowing agent is nitrogen or carbon dioxide. A method for producing the foam of claim 17.

23. The blowing agent is nitrogen or carbon dioxide. A method for producing the foam of claim 18.

24. The blowing agent is nitrogen or carbon dioxide. A method for producing the foam of claim 19.

25. The blowing agent is nitrogen or carbon dioxide. A method for producing the foam of claim 20.

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