Foam, sole body for footwear, and method for producing foam

Abstract

This foam includes a block copolymer (I) comprising a polymer block (a) including a structural unit derived from an aromatic vinyl compound and a polymer block (b) including a structural unit derived from a conjugated diene compound. The foam has a storage elastic modulus G' at 150°C, G'(150), of 3.60×104 Pa or greater and a storage elastic modulus G' at 250°C, G'(250), of 3.00×104 Pa or less.

Description

Foam, sole for footwear, and method for producing foam

[0001] The present invention relates to a foam, a sole for footwear, and a method for producing a foam.

[0002] Foams are used, for example, in soles for footwear (e.g., midsoles) (see, for example, Patent Document 1).

[0003] Japanese Unexamined Patent Application Publication No. 2020-128523

[0004] Here, soles for footwear are required to have light weight. However, as described in Patent Document 1, it is not easy to reduce the specific gravity of a foam. Such a circumstance is not limited to soles for footwear, and can similarly occur in foams in general.

[0005] In addition, foams are required to be free of oil bleed-out (bleed-out resistance). When a foam has excellent bleed-out resistance, it is expected that the adhesive strength when the foam is bonded to a different material using an adhesive will be improved. However, although foams have been conventionally required to be excellent in both light weight and bleed-out resistance, such requirements tend to become more stringent in the future.

[0006] From the above, there is a need for foams that are excellent in both light weight and bleed-out resistance. In particular, foams excellent in both light weight and bleed-out resistance are suitable for soles for footwear, for example. Similarly, there is also a need for a method for producing a foam that is excellent in both light weight and bleed-out resistance.

[0007] Accordingly, an object of the present invention is to provide a foam and a sole for footwear that are excellent in light weight and bleed-out resistance, and a method for producing the foam.

[0008] As a result of intensive studies to solve the above problems, the inventors of the present invention arrived at the following present invention and found that the problems can be solved. That is, the present invention is as follows.

[0009] [1] A foam containing a block copolymer (I) which contains a polymer block (a) containing structural units derived from an aromatic vinyl compound and a polymer block (b) containing structural units derived from a conjugated diene compound, wherein the storage modulus G'(150) at 150°C is 3.60 × 10 ４ The pressure is Pa or higher, and the storage modulus G'(250) at 250°C is 3.00 × 10⁻⁶. ４[2] A foam having a pressure of Pa or less. [1] The foam according to [1], wherein the block copolymer (I) contains a triblock copolymer (I-1), and the triblock copolymer (I-1) is a triblock copolymer containing two polymer blocks (a) and one polymer block (b) interposed between the two polymer blocks (a). [3] The foam according to [2], wherein the weight-average molecular weight (Mw) of the triblock copolymer (I-1) is 30,000 to 200,000. [4] The foam according to [2] or [3], wherein the block copolymer (I) further contains a diblock copolymer (I-2). [5] The foam according to [4], wherein the weight-average molecular weight (Mw) of the diblock copolymer (I-2) is 20,000 to 100,000. [6] The foam according to any one of [2] to [5], wherein the content of the triblock copolymer (I-1) in 100% by mass of the total amount of the block copolymer (I) is 30 to 99% by mass. [7] The foam according to any one of [1] to [6], wherein the aromatic vinyl compound in the polymer block (a) is α-methylstyrene. [8] The foam according to any one of [1] to [7], wherein the weight-average molecular weight (Mw) of the polymer block (a) in the block copolymer (I) is 1,000 to 25,000. [9] The foam according to any one of [1] to [8], wherein the content of the polymer block (a) in 100% by mass of the total amount of the block copolymer (I) is 5 to 65% by mass.

[10] The foam according to any one of [1] to [9], wherein the amount of vinyl bond in the block copolymer (I), which indicates the content of vinyl bond units in 100 mol% of the total amount of structural units derived from the conjugated diene compound, is 3.0 to 90.0 mol%.

[11] The foam according to any one of [1] to

[10] , further comprising an olefin resin (II), wherein the content of the olefin resin (II) in the foam is 60.0% by mass or less.

[12] The foam according to any one of [1] to

[11] , further comprising a plasticizer (III), wherein the content of the plasticizer (III) in the foam is less than 5% by mass.

[13] The storage modulus G' at 170°C, represented by G'(170), is 3.20 × 10 ４A foam according to any of [1] to

[12] , having a pressure of Pa or higher.

[14] Specific gravity of 0.36 g / cm³ ３ [1] to

[13] any foam, less than [1].

[15] A foam, less than 97% compression set at 40°C for 6 hours, according to any foam, less than [1] to

[14] .

[16] A foam, less than 300 μm, obtained by summing the maximum longitudinal dimensions of all foam cells observed in a 770 μm × 1450 μm observation area of ​​the cross-section of the foam, and dividing the resulting sum by the number of foam cells, according to any foam, according to any foam, less than [1] to

[15] .

[17] A foam, less than 1.8, obtained by summing the average aspect ratio of all foam cells observed in a 770 μm × 1450 μm observation area of ​​the cross-section of the foam, according to any foam, less than [1] to

[16] .

[18] The foam according to any one of [1] to

[17] , wherein the standard deviation of the maximum value of the longitudinal dimension of all foam cells observed in an observation area of ​​770 μm × 1450 μm on the cross-section of the foam is 200 or less, and the standard deviation of the maximum value of the short-side dimension is 200 or less.

[19] The foam according to any one of [1] to

[18] , wherein the MFR of the foam at 230°C and 2.16 kg is 0.1 to 100 g / 10 min.

[20] A sole for footwear comprising the foam according to any one of [1] to

[19] .

[21] A method for manufacturing the foam according to [1] to

[19] , comprising a foaming step of foaming the material of the foam using a supercritical fluid.

[22] The method for manufacturing the foam according to

[21] , wherein the supercritical fluid is nitrogen.

[23] The method for producing a foam according to

[21] or

[22] , wherein the foaming step includes a step of mixing the foam material and the supercritical fluid in the cylinder of an injection molding machine.

[0010] According to the present invention, it is possible to provide a foam and a sole for footwear that are excellent in terms of lightness and bleed-out resistance, as well as a method for manufacturing the foam.

[0011] The following description is based on an example of an embodiment of the present invention. However, the embodiments shown below are illustrative examples for realizing the technical concept of the present invention, and the present invention is not limited to the following description. Embodiments in which any of the descriptions in this specification are arbitrarily selected or arbitrarily combined are also included in the present invention. In this specification, preferred provisions can be arbitrarily selected, and combinations of preferred provisions can be said to be more preferred. In this specification, the description "XX to YY" means "XX or more and YY or less". In this specification, the lower limit and upper limit values ​​described in steps for a preferred numerical range (for example, a range of content, etc.) can be combined independently. For example, from the description "preferably 10 or more and 90 or less, more preferably 30 or more and 60 or less", the "preferred lower limit (10)" and the "more preferred upper limit (60)" can be combined to get "10 or more and 60 or less". The same applies when the preferred numerical range is described as "XX to YY". In this specification, the weight-average molecular weight (Mw), number-average molecular weight (Mn), and molecular weight distribution (Mw / Mn) are average molecular weights on a polystyrene basis, determined from gel permeation chromatography (GPC) measurements, and are values ​​measured by the method described in the examples below.

[0012] [Foam] The foam according to an embodiment of the present invention is a foam containing a block copolymer (I) which contains a polymer block (a) containing structural units derived from an aromatic vinyl compound and a polymer block (b) containing structural units derived from a conjugated diene compound, wherein the storage modulus G'(150) at 150°C is 3.60 × 10 ４ The pressure is Pa or higher, and the storage modulus G'(250) at 250°C is 3.00 × 10⁻⁶. ４ It is a foam with a pressure of Pa or less. Polymer block (a) and polymer block (b) are usually different polymer blocks from each other.

[0013] The foam of this embodiment exhibits excellent lightness and bleed-out resistance. The reason for its excellent lightness is not entirely clear, but one contributing factor is that the block copolymer (I) in the foam contains polymer blocks (a) containing structural units derived from aromatic vinyl compounds and polymer blocks (b) containing structural units derived from conjugated diene compounds. Another contributing factor to its excellent lightness is that the block copolymer (I) in the foam exhibits high elasticity at low temperatures (e.g., 150°C). It is presumed that the high elasticity of the foam at low temperatures (e.g., 150°C) is related to the fact that the foam cells in the foam are held in some ideal manner. It is then presumed that the foam's excellent lightness is due to the retention of the foam cells. The reason for its excellent bleed-out resistance is thought to be that the block copolymer (I) in the foam exhibits low elasticity at high temperatures (e.g., 250°C), making molding easier and eliminating the need for plasticizers or reducing their usage. Furthermore, the foam of this embodiment tends to exhibit excellent moldability. The reason for its excellent moldability is not entirely clear, but one contributing factor is that the foam exhibits low elasticity at high temperatures (e.g., 250°C). It is presumed that the foam's low elasticity at high temperatures (e.g., 250°C) contributes to its excellent moldability. Note that "moldability" here refers to the processability of the foam to achieve the target dimensions, and does not refer to the remoldingability after the foam has been remelted.

[0014] The material of the foam in this embodiment is not limited as long as it contains block copolymer (I). Block copolymer (I) may be one type or two or more types. Furthermore, the foam in this embodiment may or may not contain components other than block copolymer (I).

[0015] <Block Copolymer (I)> The foam of this embodiment contains block copolymer (I). By containing block copolymer (I), the foam of this embodiment has excellent lightness and bleed-out resistance. Furthermore, the foam of this embodiment also has excellent recyclability and weather resistance. Block copolymer (I) may be an unhydrogenated block copolymer or a hydrogenated block copolymer obtained by hydrogenation. In the case of a non-crosslinked foam, it is preferable that block copolymer (I) is a hydrogenated block copolymer from the viewpoint of improving heat resistance and weather resistance.

[0016] (Polymer block (a)) Polymer block (a) is a polymer block containing structural units derived from an aromatic vinyl compound. The content of structural units derived from an aromatic vinyl compound in 100% by mass of the total amount of polymer block (a) is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, even more preferably 90 to 100% by mass, even more preferably 95 to 100% by mass, and even more preferably 100% by mass, from the viewpoint of improving the compression set of the foam and maintaining its hardness. Examples of aromatic vinyl compounds include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene (p-methylstyrene), 4-propylstyrene, 4-t-butylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 2,4,6-trimethylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, vinylanthracene, N,N-diethyl-4-aminoethylstyrene, vinylpyridine, 4-methoxystyrene, monochlorostyrene, dichlorostyrene, and divinylbenzene. These aromatic vinyl compounds may be used individually or in combination of two or more. Among these, the structural units derived from aromatic vinyl compounds preferably include at least one structural unit selected from the group consisting of styrene, α-methylstyrene, and 4-methylstyrene, more preferably including at least one structural unit selected from the group consisting of styrene and α-methylstyrene, and even more preferably including structural units derived from α-methylstyrene, from the viewpoint of improving the compression set of the foam, obtaining fine foam cells, availability, and economy.

[0017] Polymer block (a) may contain structural units derived from monomers other than aromatic vinyl compounds. Examples of structural units derived from monomers other than aromatic vinyl compounds include structural units derived from conjugated diene compounds. Examples of conjugated diene compounds are the same as the examples of conjugated diene compounds that can form polymer block (b) described later. Polymer block (a) may consist only of structural units derived from aromatic vinyl compounds.

[0018] [Weight-average molecular weight of polymer block (a) in block copolymer (I)] The weight-average molecular weight (Mw) of polymer block (a) is preferably 1,000 to 25,000, more preferably 4,000 to 20,000, even more preferably 4,000 to 15,000, even more preferably 4,000 to 10,000, even more preferably 4,200 to 9,000, even more preferably 4,500 to 8,500, and even more preferably 4,600 to 8,000. If the weight-average molecular weight (Mw) of polymer block (a) is above the lower limit, better elasticity is more likely to be exhibited. Also, if it is below the upper limit, better lightweight properties are more likely to be exhibited. In another embodiment, the weight-average molecular weight (Mw) of polymer block (a) is preferably 3,000 to 10,000, more preferably 3,000 to 9,000, even more preferably 3,500 to 8,500, and even more preferably 5,000 to 7,000, from the viewpoint of improving the lightness and elasticity of the foam. The weight-average molecular weight (Mw) of polymer block (a) can also be measured from the foam.

[0019] (Content of polymer block (a) in block copolymer (I)) The content of polymer block (a) in 100% by mass of the total amount of block copolymer (I) is preferably 5 to 65% by mass, more preferably 10 to 55% by mass, even more preferably 11 to 45% by mass, and even more preferably 11 to 35% by mass. When the content of polymer block (a) is above the lower limit, the foam cells tend to become fine and uniform. This is thought to be because the foam cells were easier to maintain. Also, when the content of polymer block (a) is below the upper limit, flexibility and lightness are excellent.

[0020] (Polymer block (b)) Polymer block (b) is a polymer block containing structural units derived from a conjugated diene compound. From the viewpoint of improving the lightness and flexibility of the foam, the content of structural units derived from a conjugated diene compound in 100% by mass of the total amount of polymer block (b) is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, even more preferably 90 to 100% by mass, even more preferably 95 to 100% by mass, and even more preferably 100% by mass.

[0021] Examples of conjugated diene compounds include isoprene, butadiene, farnesene, 2,3-dimethylbutadiene, 2-phenylbutadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 1,3-octadiene, 1,3-cyclohexadiene, 2-methyl-1,3-octadiene, 1,3,7-octatriene, myrcene, and chloroprene. These conjugated diene compounds may be used individually or in combination of two or more. Among these, the structural units derived from conjugated diene compounds preferably contain at least one selected from the group consisting of farnesene-derived structural units, myrcene-derived structural units, isoprene-derived structural units, and butadiene-derived structural units, from the viewpoint of improving the lightness and flexibility of the foam, availability, and economy. It is more preferable that the structural units contain at least one selected from the group consisting of isoprene-derived structural units and butadiene-derived structural units, and even more preferable that the structural units contain butadiene-derived structural units.

[0022] Polymer block (b) may contain structural units derived from monomers other than conjugated diene compounds. For example, it may contain structural units derived from aromatic vinyl compounds, etc. Polymer block (b) does not have to contain structural units derived from monomers other than conjugated diene compounds; in other words, it may consist only of structural units derived from conjugated diene compounds.

[0023] If polymer block (b) contains structural units derived from butadiene, the bonding configuration can be 1,2-bonds or 1,4-bonds. Furthermore, if polymer block (b) contains structural units derived from isoprene, the bonding configuration can be 1,2-bonds, 3,4-bonds, or 1,4-bonds. In this specification, 1,2-bond units and 3,4-bond units are referred to as vinyl bonding units.

[0024] The content of vinyl bonding units in 100 mol% of the total amount of structural units derived from conjugated diene compounds contained in block copolymer (I) (hereinafter also referred to as "vinyl bonding amount") is preferably 3.0 to 90.0 mol%, more preferably 3.0 to 60.0 mol%, even more preferably 3.0 to 50.0 mol%, and even more preferably 5.0 to 45.0 mol%, from the viewpoint of improving moldability. The vinyl bonding amount is determined according to the method described in the examples. １ This value was calculated by 1H-NMR measurement. The amount of vinyl binding can also be measured from foam.

[0025] (Triblock Copolymer (I-1)) The block copolymer (I) in the foam of this embodiment preferably contains triblock copolymer (I-1). In one embodiment, the block copolymer (I) contains triblock copolymer (I-1) and further contains diblock copolymer (I-2). The foam of this embodiment may or may not contain block copolymer (I-3) other than triblock copolymer (I-1) and diblock copolymer (I-2). In one embodiment, the foam does not contain block copolymer (I-3). Here, "does not contain block copolymer (I-3)" means that the amount of block copolymer (I-3) is below the detection limit.

[0026] The triblock copolymer (I-1) is a triblock copolymer comprising two polymer blocks (a) and one polymer block (b) interposed between the two polymer blocks (a). The triblock copolymer (I-1) is, for example, a triblock copolymer having a bonding configuration of a first polymer block (a1-1) - polymer block (b) - second polymer block (a1-2). The first polymer block (a1-1) and the second polymer block (a1-2) are sometimes collectively referred to as polymer block (a). In the block copolymer (I-1), the first polymer block (a1-1) and the second polymer block (a1-2) may be the same block or may be different blocks. From the viewpoint of ease of manufacturing the block body, it is preferable that the first polymer block (a1-1) and the second polymer block (a1-2) are the same block.

[0027] The diblock copolymer (I-2) is a diblock copolymer having a polymer block (a)-polymer block (b) bonding configuration. The polymer block (a) of the diblock copolymer (I-2) and the first polymer block (a1-1) of the triblock copolymer (I-1) may be the same block or different blocks. The polymer block (a) of the diblock copolymer (I-2) and the second polymer block (a1-2) of the triblock copolymer (I-1) may be the same block or different blocks. The polymer block (b) of the diblock copolymer (I-2) and the polymer block (b) of the triblock copolymer (I-1) may be the same block or different blocks. From the viewpoint of ease of manufacturing the block body, it is preferable that the polymer block (a) of the diblock copolymer (I-2) and the first polymer block (a1-1) of the triblock copolymer (I-1) are the same block. Furthermore, from a similar viewpoint, it is preferable that the polymer block (a) of the diblock copolymer (I-2) and the second polymer block (a1-2) of the triblock copolymer (I-1) are identical.

[0028] The triblock copolymer (I-1) may be used alone or in combination of two or more types.

[0029] In this specification, when identical polymer blocks are linearly bonded via a divalent coupling agent or the like, the entire bonded set of identical polymer blocks is treated as a single polymer block. For example, the first polymer block (a1-1) - first polymer block (b1) - X - second polymer block (b2) - second polymer block (a1-2) (where X represents a coupling agent residue) is treated as a triblock copolymer having the bonding configuration of first polymer block (a1-1) - polymer block (b) - second polymer block (a1-2).

[0030] [Weight-average molecular weight of the first polymer block (a1-1) and the second polymer block (a1-2) in the triblock copolymer (I-1)] The weight-average molecular weight (Mw) of the first polymer block (a1-1) and the second polymer block (a1-2) in the triblock copolymer (I-1) is preferably 1,000 to 100,000, more preferably 1,500 to 50,000, even more preferably 3,000 to 30,000, even more preferably 4,000 to 15,000, even more preferably 4,500 to 10,000, and even more preferably 5,000 to 8,500, respectively. The weight-average molecular weight (Mw) of the first polymer block (a1-1) and the weight-average molecular weight (Mw) of the second polymer block (a1-2) may be the same or different.

[0031] If the weight-average molecular weight (Mw) of the first polymer block (a1-1) and the second polymer block (a1-2) is above the lower limit, better elasticity is more likely to be exhibited. Also, if the weight-average molecular weight (Mw) of the first polymer block (a1-1) and the second polymer block (a1-2) is below the upper limit, better lightweight properties are more likely to be exhibited. In another embodiment, the weight-average molecular weight (Mw) of the first polymer block (a1-1) and the second polymer block (a1-2) of the triblock copolymer (I-1) is preferably 3,000 to 10,000, more preferably 3,000 to 9,000, even more preferably 3,500 to 8,500, and even more preferably 5,000 to 7,000, from the viewpoint of improving the lightweight properties and elasticity of the foam. The weight-average molecular weight (Mw) of the first polymer block (a1-1) and the second polymer block (a1-2) can also be measured from the foam.

[0032] [Content of the first polymer block (a1-1) and the second polymer block (a1-2) in the triblock copolymer (I-1)] The content of the first polymer block (a1-1) in 100% by mass of the total amount of the triblock copolymer (I-1) is preferably 0.5 to 25% by mass, more preferably 1 to 20% by mass, even more preferably 3 to 15% by mass, and even more preferably 5 to 10% by mass. If the content of the first polymer block (a1-1) is above the lower limit, the foam cells tend to become finer and more uniform. Also, if the content of the first polymer block (a1-1) is below the upper limit, the cells become more flexible and lighter. In another embodiment, the content of the first polymer block (a1-1) in 100% by mass of the total amount of the triblock copolymer (I-1) is preferably 3 to 18% by mass, more preferably 5 to 16% by mass, and even more preferably 12 to 16% by mass, from the viewpoint of making the foam cells finer and more uniform and improving the lightness and flexibility of the foam.

[0033] The content of the second polymer block (a1-2) in 100% by mass of the total amount of the triblock copolymer (I-1) is preferably 0.5 to 25% by mass, more preferably 1 to 20% by mass, even more preferably 3 to 15% by mass, and even more preferably 5 to 10% by mass. If the content of the second polymer block (a1-2) is above the lower limit, the foam cells tend to become finer and more uniform. Also, if the content of the second polymer block (a1-2) is below the upper limit, the foam becomes more flexible and lighter. In another embodiment, the content of the second polymer block (a1-2) in 100% by mass of the total amount of the triblock copolymer (I-1) is preferably 3 to 18% by mass, more preferably 5 to 16% by mass, and even more preferably 12 to 16% by mass, from the viewpoint of making the foam cells finer and more uniform and improving the lightness and flexibility of the foam.

[0034] The total content of the first polymer block (a1-1) and the second polymer block (a1-2) in 100% by mass of the total amount of the triblock copolymer (I-1) is preferably 1 to 50% by mass, more preferably 3 to 40% by mass, even more preferably 7 to 30% by mass, and even more preferably 10 to 20% by mass. If the total content of the first polymer block (a1-1) and the second polymer block (a1-2) is above the lower limit, the foamed cells tend to become finer and more uniform. Also, if the total content of the first polymer block (a1-1) and the second polymer block (a1-2) is below the upper limit, the cells become more flexible and lighter. In another embodiment, the total content of the first polymer block (a1-1) and the second polymer block (a1-2) in 100% by mass of the total amount of the triblock copolymer (I-1) is preferably 6 to 36% by mass, more preferably 10 to 32% by mass, even more preferably 15 to 32% by mass, and even more preferably 24 to 32% by mass, from the viewpoint of making the foam cells finer and more uniform and improving the lightness and flexibility of the foam.

[0035] [Content of polymer block (b) in triblock copolymer (I-1)] The content of polymer block (b) in 100% by mass of the total amount of triblock copolymer (I-1) is preferably 50 to 99% by mass, more preferably 60 to 97% by mass, even more preferably 70 to 93% by mass, and even more preferably 80 to 90% by mass. If the content of polymer block (b) is above the lower limit, better lightness is more likely to occur and flexibility is further improved. Also, if the content of polymer block (b) is below the upper limit, it becomes more flexible and lighter. In another embodiment, the content of polymer block (b) in 100% by mass of the total amount of triblock copolymer (I-1) is preferably 64 to 94% by mass, more preferably 68 to 90% by mass, even more preferably 68 to 85% by mass, and even more preferably 68 to 76% by mass, from the viewpoint of improving the lightness and flexibility of the foam.

[0036] [Mass ratio of the first polymer block (a1-1) and the second polymer block (a1-2) to polymer block (b) in the triblock copolymer (I-1)] The mass ratio of the first polymer block (a1-1) and the second polymer block (a1-2) to polymer block (b) in the triblock copolymer (I-1) [[(a1-1) + (a1-2)] / (b)] is preferably 1 / 99 to 95 / 5, more preferably 5 / 95 to 80 / 20, even more preferably 7 / 93 to 50 / 50, even more preferably 10 / 90 to 40 / 60, and even more preferably 11 / 89 to 35 / 65, from the viewpoint of achieving a good balance between lightness and flexibility. In another embodiment, the mass ratio [[(a1-1) + (a1-2)] / (b)] of the first polymer block (a1-1) and the second polymer block (a1-2) in the triblock copolymer (I-1) is preferably 6 / 94 to 36 / 64, more preferably 10 / 90 to 32 / 68, even more preferably 15 / 85 to 32 / 68, and even more preferably 24 / 76 to 32 / 68, from the viewpoint of achieving a good balance between lightness and flexibility.

[0037] [Weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of triblock copolymer (I-1)] The weight-average molecular weight (Mw) of triblock copolymer (I-1) is preferably 30,000 to 600,000, more preferably 40,000 to 500,000, even more preferably 50,000 to 300,000, and even more preferably 60,000 to 200,000. When the weight-average molecular weight (Mw) of triblock copolymer (I-1) is above the lower limit, the foam cells tend to become finer and more uniform. Also, when the weight-average molecular weight (Mw) of triblock copolymer (I-1) is below the upper limit, excellent moldability tends to be achieved. In another embodiment, the weight-average molecular weight (Mw) of the triblock copolymer (I-1) is preferably 40,000 to 250,000, more preferably 70,000 to 110,000, from the viewpoint of making the foamed cells finer and more uniform and improving moldability.

[0038] The molecular weight distribution (Mw / Mn) of the triblock copolymer (I-1) is preferably 1.0 to 6.0, more preferably 1.0 to 4.0, even more preferably 1.0 to 3.0, even more preferably 1.0 to 2.0, even more preferably 1.0 to 1.5, even more preferably 1.0 to 1.3, and even more preferably 1.0 to 1.1. When the molecular weight distribution is within the above range, the foam cells tend to be fine and uniform. The molecular weight distribution (Mw / Mn) in this specification is the value measured by the method described in the examples below. The number average molecular weight (Mn) and molecular weight distribution (Mw / Mn) can also be measured from the foam.

[0039] [Content of Triblock Copolymer (I-1)] The content of triblock copolymer (I-1) in 100% by mass of the total amount of block copolymer (I) is 100% by mass or less, and from the viewpoint of achieving a good balance between lightness and mechanical strength, it is preferably 30 to 99% by mass, more preferably 35 to 95% by mass, and even more preferably 39 to 91% by mass. Furthermore, from the viewpoint of improving the lightness and flexibility of the foam and making the foam cells fine and uniform, the content of triblock copolymer (I-1) in 100% by mass of the total amount of block copolymer (I) is preferably 30 to 100% by mass, more preferably 35 to 100% by mass, even more preferably 65 to 100% by mass, even more preferably 85 to 100% by mass, and even more preferably 85 to 95% by mass.

[0040] (Diblock copolymer (I-2)) Diblock copolymer (I-2) is a diblock copolymer having a polymer block (a) - polymer block (b) bonding configuration. Diblock copolymer (I-2) may be used alone or in combination of two or more types.

[0041] [Molecular weight of polymer block (a) in diblock copolymer (I-2)] The weight-average molecular weight (Mw) of polymer block (a) in diblock copolymer (I-2) is preferably 800 to 50,000, more preferably 1,000 to 30,000, even more preferably 1,200 to 10,000, even more preferably 1,500 to 8,000, even more preferably 1,700 to 7,000, even more preferably 4,000 to 7,000, and even more preferably 6,000 to 7,000. If the weight-average molecular weight (Mw) of polymer block (a) is above the lower limit, it results in fine and uniform foam cells, improving mechanical strength. Also, if the weight-average molecular weight (Mw) of polymer block (a) is below the upper limit, it improves lightness.

[0042] [Content of polymer block (a) in diblock copolymer (I-2)] The content of polymer block (a) in 100% by mass of the total amount of diblock copolymer (I-2) is preferably 1 to 50% by mass, more preferably 3 to 40% by mass, even more preferably 7 to 35% by mass, and even more preferably 10 to 30% by mass. When the content of polymer block (a) is above the lower limit, fine and uniform foam cells are formed, and the mechanical strength is improved. Also, when the content of polymer block (a) is below the upper limit, better lightness is more likely to be achieved. In another embodiment, the content of polymer block (a) in 100% by mass of the total amount of diblock copolymer (I-2) is preferably 7 to 40% by mass, more preferably 10 to 35% by mass, and even more preferably 20 to 35% by mass, from the viewpoint of forming fine and uniform foam cells, improving mechanical strength, and improving the lightness of the foam.

[0043] [Content of polymer block (b) in diblock copolymer (I-2)] The content of polymer block (b) in 100% by mass of the total amount of diblock copolymer (I-2) is preferably 50 to 99% by mass, more preferably 60 to 97% by mass, even more preferably 70 to 93% by mass, and even more preferably 80 to 90% by mass. When the content of polymer block (b) is above the lower limit, fine and uniform foam cells are formed, and the mechanical strength is improved. Also, when the content of polymer block (b) is below the upper limit, excellent lightness and flexibility are achieved. In another embodiment, the content of polymer block (b) in 100% by mass of the total amount of diblock copolymer (I-2) is preferably 60 to 93% by mass, more preferably 65 to 90% by mass, and even more preferably 65 to 80% by mass, from the viewpoint of forming fine and uniform foam cells and improving mechanical strength, and from the viewpoint of improving the lightness and flexibility of the foam.

[0044] [Mass ratio of polymer block (a) and polymer block (b) in diblock copolymer (I-2)] The mass ratio [(a) / (b)] of polymer block (a) to polymer block (b) in diblock copolymer (I-2) is preferably 1 / 99 to 95 / 5, more preferably 5 / 95 to 80 / 20, even more preferably 10 / 90 to 50 / 50, and even more preferably 11 / 89 to 35 / 65, from the viewpoint of improving lightness. In another embodiment, the mass ratio [(a) / (b)] of polymer block (a) to polymer block (b) in diblock copolymer (I-2) is preferably 7 / 93 to 40 / 60, more preferably 10 / 90 to 35 / 65, and even more preferably 20 / 80 to 35 / 65, from the viewpoint of improving lightness.

[0045] [Weight-average molecular weight (Mw) and molecular weight distribution of diblock copolymer (I-2)] The weight-average molecular weight (Mw) of diblock copolymer (I-2) is preferably 10,000 to 150,000, more preferably 20,000 to 100,000, even more preferably 30,000 to 90,000, even more preferably 35,000 to 80,000, and even more preferably 40,000 to 70,000, from the viewpoint of improving lightness. When the weight-average molecular weight (Mw) of diblock copolymer (I-2) is above the lower limit, it results in fine and uniform foam cells and exhibits good mechanical strength. Also, when the weight-average molecular weight (Mw) of diblock copolymer (I-2) is below the upper limit, moldability is improved. In another embodiment, the weight-average molecular weight (Mw) of the diblock copolymer (I-2) is preferably 30,000 to 70,000, more preferably 32,000 to 40,000, from the viewpoint of forming fine and uniform foam cells, exhibiting good mechanical strength, and improving the moldability of the foam.

[0046] The molecular weight distribution (Mw / Mn) of the diblock copolymer (I-2) is preferably 1.0 to 6.0, more preferably 1.0 to 4.0, even more preferably 1.0 to 3.0, even more preferably 1.0 to 2.0, even more preferably 1.0 to 1.5, even more preferably 1.0 to 1.3, and even more preferably 1.0 to 1.1. When the molecular weight distribution is within the above range, a fine and uniform foam cell is formed, exhibiting good mechanical strength.

[0047] [Content of Diblock Copolymer (I-2)] The content of diblock copolymer (I-2) in 100% by mass of the total amount of block copolymer (I) is 0% by mass or more, and from the viewpoint of improving flexibility, it is preferably 1 to 70% by mass, more preferably 5 to 65% by mass, and even more preferably 9 to 61% by mass. The content of diblock copolymer (I-2) in 100% by mass of the total amount of triblock copolymer (I-1) and diblock copolymer (I-2) is 0% by mass or more, and from the viewpoint of improving flexibility, it is preferably 1 to 70% by mass, more preferably 5 to 65% by mass, and even more preferably 9 to 61% by mass. In another embodiment, from the viewpoint of improving the lightness and flexibility of the foam and making the foam cells fine and uniform, the content of diblock copolymer (I-2) in 100% by mass of the total amount of block copolymer (I) is preferably 0 to 70% by mass, more preferably 0 to 65% by mass, even more preferably 0 to 35% by mass, and even more preferably 0 to 15% by mass.

[0048] From the viewpoint of improving the fluidity of the block copolymer (I), thereby making the foam cells fine and uniform, and improving the lightness and flexibility of the foam, it is preferable that the block copolymer (I) contains a triblock copolymer (I-1) and a diblock copolymer (I-2).

[0049] [Mass ratio of triblock copolymer (I-1) to diblock copolymer (I-2)] When the block copolymer (I) contains triblock copolymer (I-1) and diblock copolymer (I-2), the mass ratio of triblock copolymer (I-1) to diblock copolymer (I-2) in the block copolymer (I) [(I-1) / (I-2)] is preferably 1 / 99 to 99 / 1, more preferably 5 / 95 to 95 / 5, even more preferably 7 / 93 to 93 / 7, and even more preferably 10 / 90 to 90 / 10, from the viewpoint of achieving both improved lightness and good mechanical strength. In another embodiment, the mass ratio [(I-1) / (I-2)] of the triblock copolymer (I-1) to the diblock copolymer (I-2) in the block copolymer (I) is preferably 30 / 70 to 100 / 0, more preferably 30 / 70 to 99 / 1, even more preferably 35 / 65 to 95 / 5, and even more preferably 39 / 61 to 91 / 9, from the viewpoint of achieving both improved lightness and good mechanical strength. In yet another embodiment, from the viewpoint of improving the lightness and flexibility of the foam and making the foam cells fine and uniform, the mass ratio [(I-1) / (I-2)] of the triblock copolymer (I-1) to the diblock copolymer (I-2) is preferably 30 / 70 to 100 / 0, more preferably 35 / 65 to 100 / 0, even more preferably 65 / 35 to 100 / 0, and even more preferably 85 / 15 to 100 / 0.

[0050] The total content of triblock copolymer (I-1) and diblock copolymer (I-2) in 100% by mass of the total amount of block copolymer (I) is preferably 30 to 100% by mass, more preferably 40 to 100% by mass, even more preferably 70 to 100% by mass, even more preferably 80 to 100% by mass, and even more preferably 90 to 100% by mass, from the viewpoint of improving lightness. In another embodiment, from the viewpoint of improving the lightness and flexibility of the foam and making the foam cells fine and uniform, it is even more preferable that the content be 100% by mass.

[0051] From the viewpoint of improving the lightness and flexibility of the foam and making the foam cells fine and uniform, a block copolymer (I) comprising a polymer block (a) comprising at least one structural unit selected from the group consisting of styrene, α-methylstyrene and 4-methylstyrene and a polymer block (b) comprising at least one structural unit selected from isoprene and butadiene is preferred. A block copolymer (I) comprising a polymer block (a) comprising a structural unit derived from α-methylstyrene and a polymer block (b) comprising a structural unit derived from butadiene is more preferred, or a block copolymer (I) comprising a polymer block (a) comprising a structural unit derived from styrene and a polymer block (b) comprising a structural unit derived from isoprene is even more preferred, and a block copolymer (I) comprising a polymer block (a) comprising a structural unit derived from α-methylstyrene and a polymer block (b) comprising a structural unit derived from butadiene is even more preferred.

[0052] (Method for producing block copolymer (I)) Block copolymer (I) can be produced by solution polymerization or by methods described in Japanese Patent Publication No. 2012-502135, Japanese Patent Publication No. 2012-502136, etc. Among these, solution polymerization is preferred. As for solution polymerization, known methods such as ionic polymerization methods such as anionic polymerization and cationic polymerization; radical polymerization; etc. can be applied. Among these, anionic polymerization is preferred.

[0053] An anionic polymerization method involves sequentially adding aromatic vinyl compounds and conjugated diene compounds in the presence of a solvent, an anionic polymerization initiator, and optionally a Lewis base to obtain a block copolymer. Examples of anionic polymerization initiators include alkali metals such as lithium, sodium, and potassium; alkaline earth metals such as beryllium, magnesium, calcium, strontium, and barium; lanthanide rare earth metals such as lanthanum and neodymium; compounds containing the alkali metals, compounds containing the alkaline earth metals, and compounds containing lanthanide rare earth metals. Among these, compounds containing alkali metals and compounds containing alkaline earth metals are preferred from the viewpoint of productivity, availability, and economics, and compounds containing alkali metals are more preferred. Among the alkali metal-containing compounds, organoalkali metal compounds are preferred.

[0054] Examples of organoalkali metal compounds include organolithium compounds such as methyllithium, ethyllithium, n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, stilbenithium, dilithithiomethane, dilithionaphthalene, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, and 1,3,5-trilithiobenzene; sodium naphthalene, potassium naphthalene; and others. Among these, organolithium compounds are preferred from the viewpoint of productivity, availability, and economic efficiency, with n-butyllithium and sec-butyllithium being more preferred, and sec-butyllithium being even more preferred. Organoalkali metal compounds may also be used as organoalkali metal amides by reacting them with secondary amines such as diisopropylamine, dibutylamine, dihexylamine, and dibenzylamine. The amount of organoalkali metal compound used varies depending on the molecular weight of the target block copolymer (I), but is usually 0.01 to 3 parts by mass per 100 parts by mass of the total amount of aromatic vinyl compound and conjugated diene compound.

[0055] There are no particular restrictions on the solvent as long as it does not adversely affect the anionic polymerization reaction. Examples include saturated aliphatic hydrocarbons such as n-pentane, isopentane, n-hexane, n-heptane, and isooctane; saturated alicyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclopentane; and aromatic hydrocarbons such as benzene, toluene, and xylene. These may be used individually or in combination of two or more. There are no particular restrictions on the amount of solvent used.

[0056] Lewis bases play a role in controlling the microstructure of structural units derived from conjugated diene compounds. Examples of Lewis bases include ether compounds such as dibutyl ether, diethyl ether, tetrahydrofuran, dioxane, and ethylene glycol diethyl ether; pyridine; tertiary amines such as N,N,N',N'-tetramethylethylenediamine and trimethylamine; alkali metal alkoxides such as potassium t-butoxide; and phosphine compounds. When using Lewis bases, the amount is usually preferably 0.01 to 1000 molar equivalents per mole of anionic polymerization initiator.

[0057] The polymerization reaction temperature is typically -80 to +150°C, preferably 0 to 100°C, and more preferably 10 to 90°C. The polymerization reaction may be batch-based or continuous-based.

[0058] Block copolymer (I) can be produced by continuously or intermittently supplying each monomer to the polymerization reaction solution so that the amounts of aromatic vinyl compounds and conjugated diene compounds in the polymerization reaction system are within a specific range, or by sequentially polymerizing each monomer in the polymerization reaction solution so that they are in a specific ratio. The polymerization reaction can be stopped by adding an alcohol such as methanol or isopropanol as a polymerization stopper. The block copolymer (I) can be isolated by pouring the obtained polymerization reaction solution into a poor solvent such as methanol to precipitate the block copolymer, or by washing the polymerization reaction solution with water, separating it, and then drying it.

[0059] The triblock copolymer (I-1) is preferably produced by the method described in [i] or [ii] below. [i] A method of polymerizing a first polymer block (a1-1), a polymer block (b), and a second polymer block (a1-2) in this order. [ii] A method of producing the triblock copolymer by synthesizing a diblock copolymer of the first polymer block (a1-1) and polymer block (b), and then coupling the ends of the polymer blocks (b) of the diblock copolymer using a coupling agent.

[0060] Diblock copolymer (I-2) is preferably produced by polymerizing polymer block (a) and polymer block (b) in this order.

[0061] Examples of coupling agents include: divinylbenzene; polyvalent epoxy compounds such as epoxidized 1,2-polybutadiene, epoxidized soybean oil, and tetraglycidyl-1,3-bisaminomethylcyclohexane; halides such as tin tetrachloride, tetrachlorosilane, trichlorosilane, trichloromethylsilane, dichlorodimethylsilane, and dibromodimethylsilane; methyl benzoate, ethyl benzoate, phenyl benzoate, diethyl oxalate, diethyl malonate, diethyl adipate, dimethyl phthalate, and tetraglycidyl hydroxypropyl Examples include ester compounds such as dimethyl lephthalate; carbonate ester compounds such as dimethyl carbonate, diethyl carbonate, and diphenyl carbonate; alkoxysilane compounds such as diethoxydimethylsilane, trimethoxyethylsilane, triethoxymethylsilane, tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, tetrakis(2-ethylhexyloxy)silane, bis(triethoxysilyl)ethane, and 3-aminopropyltriethoxysilane; and 2,4-tolylene diisocyanate. These coupling agents may be used individually or in combination of two or more.

[0062] The triblock copolymer (I-1) and the diblock copolymer (I-2) may be prepared separately. Specifically, a polymerization reaction solution containing the triblock copolymer (I-1) and a polymerization reaction solution containing the diblock copolymer (I-2) may be prepared separately, and then the triblock copolymer (I-1) and the diblock copolymer (I-2) may be mixed. The mixing may be done by mixing the polymerization reaction solutions together, or by isolating the triblock copolymer (I-1) and the diblock copolymer (I-2) using the method described above before mixing them. When the polymerization reaction solutions are mixed together, a mixture of the triblock copolymer (I-1) and the diblock copolymer (I-2) can be obtained by subsequently isolating the block copolymer using the method described above.

[0063] The triblock copolymer (I-1) and the diblock copolymer (I-2) may be produced in the same polymerization reaction solution. A polymerization reaction solution containing the diblock copolymer (I-2) can be produced first, and a portion of the total amount of diblock copolymer (I-2) contained in the polymerization reaction solution can be coupled using a coupling agent to obtain a polymerization reaction solution containing both the triblock copolymer (I-1) and the diblock copolymer (I-2). Subsequently, a mixture of the triblock copolymer (I-1) and the diblock copolymer (I-2) can be obtained by isolating the block copolymer using the method described above. In this case, the first polymer block (a1-1) of the triblock copolymer (I-1), the second polymer block (a1-2) of the triblock copolymer (I-1), and the polymer block (a) of the diblock copolymer (I-2) are the same, and the polymer block (b) of the triblock copolymer (I-1) and the polymer block (b) of the diblock copolymer (I-2) are the same.

[0064] In this embodiment, the block copolymer (I) is preferably a hydrogenated block copolymer (I). A known method can be used for hydrogenation. For example, a hydrogenation reaction is carried out by adding a Ziegler catalyst; a Ziegler catalyst; a nickel, platinum, palladium, ruthenium, or rhodium metal catalyst supported on carbon, silica, diatomaceous earth, etc.; an organometallic complex having cobalt, nickel, palladium, rhodium, or ruthenium metal; to a solution obtained by dissolving the block copolymer (I) in a solvent that does not affect the hydrogenation reaction; as a hydrogenation catalyst. Examples of the hydrogenation catalyst include Raney nickel; heterogeneous catalysts in which metals such as Pt, Pd, Ru, Rh, and Ni are supported on elements such as carbon, alumina, and diatomaceous earth; Ziegler catalysts consisting of a combination of a transition metal compound and an alkylaluminum compound, alkyllithium compound, etc.; and metallocene catalysts. From the viewpoint of easily suppressing nuclear hydrogenation of aromatic rings, Ziegler catalysts are preferred. Among the Ziegler catalysts, a combination of a transition metal compound and an alkylaluminum compound is preferred. Nickel compounds are preferred as the transition metal compound. In the hydrogenation reaction, the hydrogen pressure is preferably 0.1 to 20 MPa, the reaction temperature is preferably 100 to 200°C, and the reaction time is preferably 1 to 20 hours.

[0065] The hydrogenation rate of the carbon-carbon double bonds in the structural units derived from the conjugated diene compound in the block copolymer (I) is preferably 90 to 100 mol%, more preferably 94 to 100 mol%, even more preferably 95 to 100 mol%, even more preferably 96 to 100 mol%, even more preferably 97 to 100 mol%, and even more preferably 98 to 99.5 mol%, from the viewpoint of obtaining better weather resistance. The hydrogenation rate is measured by the method described in the examples. The hydrogenation rate can also be measured from the foam.

[0066] In this embodiment, an unmodified block copolymer may be used, but a modified block copolymer may also be used as described below.

[0067] In the case of a modified block copolymer, the block copolymer may be modified after the hydrogenation step. Examples of functional groups that can be introduced by modification include amino groups, alkoxysilyl groups, hydroxyl groups, epoxy groups, carboxyl groups, carbonyl groups, mercapto groups, isocyanate groups, and acid anhydride groups. As a method for modifying a block copolymer, for example, a method of grafting a modified agent such as maleic anhydride onto a hydrogenated block copolymer after isolation can be used.

[0068] Furthermore, block copolymers can also be modified before the hydrogenation step. Specific methods include adding coupling agents such as tin tetrachloride, tetrachlorosilane, dichlorodimethylsilane, dimethyldiethoxysilane, tetramethoxysilane, tetraethoxysilane, 3-aminopropyltriethoxysilane, tetraglycidyl-1,3-bisaminomethylcyclohexane, 2,4-tolidylenediisocyanate, polymerization end modifiers such as 4,4'-bis(diethylamino)benzophenone, N-vinylpyrrolidone, or other modifiers described in Japanese Patent Application Publication No. 2011-132298, before adding a polymerization inhibitor.

[0069] The functional group may be introduced at either the polymerization end of the block copolymer or at a side chain. Furthermore, one or more functional groups may be used. The modifier is preferably in the range of 0.01 to 10 molar equivalents per mole of the anionic polymerization initiator.

[0070] The block copolymer (I) may be manufactured as described above, or it may be a commercially available product. As a commercially available product, for example, maleic anhydride-modified SEBS (MAh-modified SEBS), product name "TAIPOL® 7126" manufactured by TSRC Corporation can be used.

[0071] (Content of block copolymer (I)) The content of block copolymer (I) in 100% by mass of the total amount of foam in this embodiment is preferably 0.5 to 100% by mass, more preferably 1 to 90% by mass, even more preferably 2 to 80% by mass, even more preferably 3 to 70% by mass, and even more preferably 5 to 30% by mass, from the viewpoint of improving lightness. In another embodiment, the content of block copolymer (I) in 100% by mass of the total amount of foam in this embodiment is preferably 25 to 100%, more preferably 40 to 100% by mass, even more preferably 50 to 100% by mass, and even more preferably 70 to 100% by mass, from the viewpoint of improving the lightness and flexibility of the foam and making the foam cells fine and uniform. Furthermore, when an olefin resin, as described later, is included, the content of block copolymer (I) in 100% by mass of the total amount of foam in this embodiment is preferably 25 to 90% by mass, more preferably 30 to 90% by mass, even more preferably 40 to 85% by mass, even more preferably 50 to 80% by mass, and even more preferably 70 to 80% by mass, from the viewpoint of improving the lightness and flexibility of the foam and making the foam cells fine and uniform.

[0072] <Olefin resin (II)> The foam of this embodiment may or may not contain olefin resin (II). Block copolymer (I) is excluded from olefin resin (II). In other words, in this specification, olefin resin (II) is an example of a resin other than block copolymer (I).

[0073] The olefin resin (II) is preferably a polyolefin resin. As the polyolefin resin, at least one selected from the group consisting of olefin homopolymers, ethylene-α-olefin copolymers, crosslinkable ethylene copolymers, and ethylene copolymers is preferred. The olefin homopolymer is preferably at least one selected from the group consisting of high-density polyethylene (HDPE), medium-density polyethylene, low-density polyethylene (LDPE), and polypropylene. Furthermore, it is preferable to use polyethylene and polypropylene in combination as the olefin homopolymer. The ethylene-α-olefin copolymer is preferably at least one selected from the group consisting of ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-heptene copolymer, ethylene-1-octene copolymer, ethylene-4-methyl-1-pentene copolymer, ethylene-1-nonene copolymer, and ethylene-1-decene copolymer. As the crosslinkable ethylene copolymer, ethylene-1,7-octadiene copolymer is preferred. The ethylene-based copolymer is preferably at least one selected from the group consisting of ethylene-vinyl acetate copolymer (hereinafter also referred to as EVA), ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, and resins modified with maleic anhydride or the like. Among these, from the viewpoint of maintaining the hardness of the foam and improving its lightweight properties, the olefin resin (II) is preferably at least one selected from the group consisting of high-density polyethylene, medium-density polyethylene, low-density polyethylene, polypropylene, ethylene-polypropylene copolymer, ethylene-α-olefin copolymer, and EVA.

[0074] The olefin resin (II) may be a synthetic product or a commercially available product. Examples of commercially available products other than EVA include "J226T," a random polypropylene manufactured by Prime Polymer, and "C4300," a low-density polyethylene (LDPE) manufactured by Asia Polymer Corporation.

[0075] The melt flow rate (MFR) of olefin resin (II) at a temperature of 190°C and a load of 2.16 kg is preferably 0.3 to 800 g / 10 min, more preferably 0.5 to 100.0 g / 10 min, and even more preferably 1.0 to 20.0 g / 10 min. Furthermore, the melt flow rate (MFR) at a temperature of 230°C and a load of 2.16 kg is preferably 0.3 to 800 g / 10 min, more preferably 0.5 to 100.0 g / 10 min, and even more preferably 1.0 to 20.0 g / 10 min. When the MFR is within the above range, moldability is good. The MFR can be measured in accordance with JIS K7210:1999.

[0076] In this embodiment, when the foam contains olefin resin (II), the content of olefin resin (II) in the foam is preferably 5 to 80% by mass, more preferably 10 to 70% by mass, and even more preferably 15 to 60% by mass. When the content of olefin resin (II) is within the above range, it is easier to obtain a foam with excellent mechanical strength while ensuring moldability. In another embodiment, the content of olefin resin (II) in the foam is preferably 10 to 75% by mass, more preferably 10 to 70% by mass, even more preferably 15 to 60% by mass, even more preferably 20 to 50% by mass, and even more preferably 20 to 30% by mass, from the viewpoint of improving the lightness and flexibility of the foam and making the foam cells fine and uniform.

[0077] When the foam of this embodiment contains olefin resin (II), the mass ratio of block copolymer (I) to olefin resin (II) [(I) / (II)] is preferably 10 / 90 to 99 / 1, more preferably 20 / 80 to 95 / 5, even more preferably 30 / 70 to 90 / 10, particularly preferably 50 / 50 to 85 / 15, and most preferably 55 / 45 to 85 / 15. Good mechanical strength is achieved within the above range. In another embodiment, when the foam of this embodiment contains olefin resin (II), the mass ratio of block copolymer (I) to olefin resin (II) [(I) / (II)] is preferably 25 / 75 to 90 / 10, more preferably 30 / 70 to 90 / 10, even more preferably 60 / 40 to 85 / 15, even more preferably 50 / 50 to 80 / 20, and even more preferably 70 / 30 to 80 / 20, from the viewpoint of improving the lightness and flexibility of the foam and making the foam cells fine and uniform.

[0078] (EVA) When the foam of this embodiment contains EVA as the olefin resin (II), the content of vinyl acetate-derived structural units in the EVA (VA content) is preferably 3 to 60% by mass, more preferably 5 to 50% by mass, and even more preferably 10 to 40% by mass. In another embodiment, the content of vinyl acetate-derived structural units in the EVA (VA content) is preferably 5 to 35% by mass. When the VA content is within the above range, it is easier to obtain a foam with excellent adhesion (adhesive properties) to dissimilar materials. When the foam contains EVA as the olefin resin (II), the MFR (melt flow rate) of the EVA at a temperature of 190°C and a load of 2.16 kg is preferably 0.3 to 800 g / 10 min, more preferably 0.5 to 100.0 g / 10 min, and even more preferably 1.0 to 20.0 g / 10 min, from the viewpoint of obtaining a foam with excellent adhesion (adhesive properties) to dissimilar materials. MFR can be measured in accordance with JIS K7210:1999.

[0079] Furthermore, EVA includes copolymers containing vinyl alcohol produced by hydrolyzing a portion of vinyl acetate, in addition to ethylene and vinyl acetate. In this case, the VA content is defined as the total amount of vinyl acetate and vinyl alcohol in the copolymer, and the vinyl acetate content is specified accordingly.

[0080] Examples of commercially available EVA products include "Evaflex" (trade name, registered trademark) from Mitsui Dow Polychemicals Ltd., "Ultrasen" (trade name, registered trademark) from Tosoh Corporation, "UBE Polyethylene (EVA)" (trade name, registered trademark is "UBE Polyethylene") from Ube Maruzen Polyethylene Co., Ltd., "Suntech-EVA" (trade name, registered trademark) from Asahi Kasei Chemicals Corporation, "Ethylene Vinyl Acetate Copolymer NUC" (brand name) from NUC Corporation, and EVA products from Asia Polymer Corporation such as "EV302," "V18161," and "V26061."

[0081] When the foam of this embodiment contains olefin resin (II), the total content of block copolymer (I) and olefin resin (II) in the foam may be 100% by mass, preferably 5.5 to 100% by mass, more preferably 11 to 95% by mass, and even more preferably 12 to 90% by mass.

[0082] <Polystyrene Resin> The foam of this embodiment may or may not contain polystyrene resin. Block copolymer (I) is excluded from the polystyrene resin. In other words, in this specification, polystyrene resin is an example of a resin other than block copolymer (I). The polystyrene resin is not limited, and commercially available products or synthetic products may be used.

[0083] When the foam of the present embodiment contains a polystyrene resin, the content of the polystyrene resin based on 100% by mass of the total amount of the foam is preferably 0.1 to 60.0% by mass, more preferably 5.0 to 60.0% by mass, still more preferably 10 to 55% by mass, and even more preferably 15 to 50% by mass. When the content of the polystyrene resin falls within the above range, properties depending on the polystyrene resin are imparted to the foam while maintaining the lightweight property and favorable mechanical properties of the foam. When the foam of the present embodiment contains a polystyrene resin, the total content of the block copolymer (I) and the polystyrene resin in the foam is preferably 5.5 to 100% by mass, more preferably 11 to 95% by mass, and still more preferably 12 to 90% by mass. When the foam of the present embodiment contains the olefin resin (II) and a polystyrene resin, the total content of the block copolymer (I), the olefin resin (II), and the polystyrene resin in the foam is preferably 6 to 100% by mass, more preferably 12 to 95% by mass, and still more preferably 14 to 90% by mass.

[0084] <Plasticizer (III)> The foam of the present embodiment may contain a plasticizer (III) from the viewpoint of flexibility, and does not have to contain the plasticizer (III) from the viewpoint of favorable lightweight property and bleed-out resistance. Examples of the plasticizer (III) include biomass-derived plasticizers having no carboxy group, vegetable oils, synthetic plasticizers, and recycled oils.

[0085] Examples of the biomass-derived plasticizer (III) having no carboxy group include compounds represented by the following general formula (1) and compounds represented by the following general formula (2).

[0086] However, in general formula (1), n １ to n ３ are each independently 1 or 3, and R １ to R ６ are each independently a hydrogen atom or an unsubstituted hydrocarbon group, the total number of carbon atoms of R １ and R ２ is 14, the total number of carbon atoms of R ３ and R ４ is 14, and R ５ and R ６The total number of carbon atoms is 14, R １ ~R ６ It may have a branched structure.

[0087] However, in general formula (2), n ４ and n ５ Each of these is independently either 1 or 3, and R ７ ~R １０ Each is independently a hydrogen atom or an unsubstituted hydrocarbon group, and R ７ and R ８ The total number of carbon atoms is 14, R ９ and R １０ The total number of carbon atoms is 14, R ７ ~R １０ It may have a branched structure.

[0088] Examples of vegetable oils include castor oil, cottonseed oil, linseed oil, safflower oil, rapeseed oil, soybean oil, Nagi oil, wood wax, pine oil, corn oil, peanut oil, olive oil, palm oil, palm olein, palm stearin, and other plant-derived oils, as well as transesterified oils, hydrogenated oils, or fractionated oils of these. Examples of synthetic plasticizers include oil-based softeners such as paraffinic, naphthenic, and aromatic process oils, mineral oil, and white oil; phthalic acid derivatives such as dioctyl phthalate and dibutyl phthalate; liquid co-oligomers of ethylene and α-olefins; liquid paraffin; polybutene; low molecular weight polyisobutylene; liquid polydienes such as liquid polybutadiene, liquid polyisoprene, liquid polyisoprene / butadiene copolymer, liquid styrene / butadiene copolymer, and liquid styrene / isoprene copolymer; and hydrogenated or modified versions thereof. Recycled oil refers to oil made from used oil. While recycled oil is not particularly limited as long as it is made from used oil, examples of recycled oil include the product names "RECOR-T 4867," "RECOR-M 1259," and "RECOR-M 1260" (all manufactured by H&R).

[0089] These can be used individually or in combination of two or more types.

[0090] Among the plasticizers (III) mentioned above, synthetic plasticizers and recycled oils are preferred from the viewpoint of compatibility with block copolymers (I). More specifically, paraffinic and naphthenic process oils; liquid co-oligomers of ethylene and α-olefins; liquid paraffin; and low molecular weight polyisobutylene are preferred, with paraffinic and naphthenic process oils being more preferred, and paraffinic process oil being even more preferred.

[0091] When the foam of this embodiment contains the plasticizer (III), from the viewpoint of good lightness and bleed-out resistance, the content of plasticizer (III) in 100% by mass of the total amount of foam is preferably less than 10% by mass, more preferably less than 5% by mass, even more preferably 3% by mass or less, and even more preferably 1% by mass or less. In a particular embodiment, from the viewpoint of flexibility, the content of plasticizer (III) in 100% by mass of the total amount of foam is preferably 0% by mass or more.

[0092] <Filler> The foam of this embodiment may or may not contain a filler. One type of filler may be used alone, or two or more types may be used in combination. The filler may or may not be surface-treated with a silane coupling agent. Examples of fillers include wet silica (hydrated silica); dry silica (anhydrous silica); calcium silicate, aluminum silicate, kaolin, talc, clay, pyrophyllite, mica, montmorillonite, bentonite, wollastonite, sepiolite, xonotlite, zeolite, diatomaceous earth, halloysite, and other silicate compounds. Among these, silica is preferred, and wet silica is more preferred, from the viewpoint of further improving moldability, mechanical strength, and wear resistance of the resulting molded article. One type of filler may be used alone, or two or more types may be used in combination.

[0093] The filler content in 100% by mass of the total amount of foam in this embodiment is preferably 1 to 55% by mass, more preferably 5 to 50% by mass, even more preferably 10 to 45% by mass, even more preferably 15 to 40% by mass, and even more preferably 20 to 35% by mass.

[0094] <Other Additives> The foam of this embodiment may contain other additives other than those described above, as long as they do not impair the effects of the present invention. Examples of other additives include any resin (excluding block copolymer (I), olefin resin (II), and polystyrene resin), heat aging inhibitors, antioxidants, light stabilizers, antistatic agents, mold release agents, flame retardants, foaming agents (excluding supercritical fluids described later), pigments, dyes, whitening agents, crosslinking agents, etc. These additives may be used individually or in combination of two or more. The amount of other additives in 100% by mass of the total amount of the foam of this embodiment is such that it does not impair the effects of the present invention.

[0095] The foam or foam material of this embodiment may or may not contain a crosslinking agent. If the foam or foam material of this embodiment contains a crosslinking agent, the content of the crosslinking agent in 100% by mass of the total amount of the foam or foam material is preferably 15% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and even more preferably 3% by mass or less. From the viewpoint of suppressing crosslinking, the content of the crosslinking agent in 100% by mass of the total amount of the foam or foam material is preferably 0% by mass.

[0096] <Physical Properties> (Elasticity) The foam of this embodiment has a storage modulus of elasticity G'(150) of 3.60 × 10⁻¹⁰ at 150°C. ４ The pressure is Pa or higher, and the storage modulus G'(250) at 250°C is 3.00 × 10⁻⁶. ４ It is less than or equal to Pa. The storage modulus G' can be measured by the method described in the examples. The storage modulus G' can also be measured from foam.

[0097] From the viewpoint of obtaining a foam with the target dimensions and fine, uniform cells, G'(250) is preferably 2.80 × 10 ４ Pa or less, more preferably 2.50 × 10 ４ Pa or less, more preferably 2.00 × 10 ４ Pa or less, more preferably 1.50 × 10 ４ Pa or less, more preferably 1.25 × 10 ４It is Pa or less. From the viewpoint of lightweight properties, G'(150) is preferably 3.65 × 10 ４ Pa or higher, more preferably 4.00 × 10 ４ Pa or higher, more preferably 9.00 × 10 ４ Pa or higher, more preferably 18.00 × 10 ４ Pa or higher, more preferably 50.00 × 10 ４ It is Pa or higher. From the viewpoint of moldability and lightweight, preferably G'(250) is 2.80 × 10 ４ Pa is less than or equal to 3.65 × 10 ４ Pa or higher, more preferably G'(250) is 2.50 × 10 ４ Pa is less than or equal to 4.00 × 10 ４ Pa or higher, more preferably G'(250) is 2.00 × 10 ４ Pa is less than or equal to 9.00 × 10 ４ Pa or higher, and more preferably G'(250) is 1.50 × 10 ４ Pa is less than or equal to 18.00 × 10 ４ Pa or higher, and more preferably G'(250) is 1.25 × 10 ４ Pa is less than or equal to 50.00 × 10 ４ It is Pa or higher.

[0098] From the viewpoint of lightweight properties, the foam of this embodiment preferably has a storage modulus of elasticity G'(170) at 170°C, which is 2.00 × 10⁻⁶. ４ Pa or higher, more preferably 2.50 × 10 ４ Pa or higher, more preferably 3.20 × 10 ４ Pa or higher, more preferably 7.00 × 10 ４ Pa or higher, more preferably 20.00 × 10 ４ It is Pa or higher.

[0099] The upper limits for G'(150), G'(170), and G'(250) are naturally determined depending on the foam material. The upper limit for G'(150) is preferably 100.00 × 10 from the viewpoint of foam cell formation and lightweight properties. ４Pa or less, more preferably 90.00 × 10 ４ Pa or less, more preferably 80.00 × 10 ４ It is Pa or less. The upper limit of G'(170) is preferably 50.00 × 10 from the viewpoint of foam cell formation and lightweight properties. ４ Pa or less, more preferably 40.00 × 10 ４ Pa or less, more preferably 30.00 × 10 ４ It is less than or equal to Pa. From the viewpoint of obtaining the target dimension, the lower G'(250) is preferable. The lower limit of G'(250) may be 10 Pa, 100 Pa, or 1,000 Pa.

[0100] (Specific gravity) The foam of this embodiment preferably has a specific gravity of 0.36 g / cm³. ３ Less than, more preferably 0.35 g / cm³ ３ The following is the case: From the standpoint of superior lightness, the specific gravity of the foam is 0.34 g / cm³. ３ Below, 0.32g / cm ３ Below, 0.30g / cm ３ Below, 0.29g / cm ３ Below, 0.28g / cm ３ Below, 0.27g / cm ３ Below, 0.26g / cm ３ Below, 0.25g / cm ３ The following may also be used. The specific gravity can be measured in accordance with ISO 1183:1987, and specifically, it can be measured by the method described in the examples. The lower limit of the specific gravity is determined according to the degree of foaming.

[0101] (Hardness) From the viewpoint of ensuring wear resistance, the foam of this embodiment has a Type C hardness of preferably 10 to 100, more preferably 40 to 100, even more preferably 45 to 100, and even more preferably 47 to 95. From the viewpoint of ensuring elasticity, the Type C hardness of the foam is preferably 5 to 60. From the viewpoint of ensuring flexibility, the Type C hardness of the foam is preferably 5 or higher, more preferably 10 or higher, and even more preferably 15 or higher. The Type C hardness can be measured in accordance with ISO 2349:2015, and specifically can be measured by the method described in the example.

[0102] (Compression Set) From the viewpoint of excellent durability, the foam of this embodiment preferably has a compression set of less than 97% at 40°C for 6 hours, more preferably 95% or less, even more preferably 90% or less, and even more preferably 80% or less. The lower the compression set at 6 hours, the better, and there is no lower limit, but it may be 5% or more, or 10% or more. The compression set can be measured according to Method B of ASTM D395-16, and specifically, it can be measured by the method described in the embodiment.

[0103] (Oil Bleeding) As mentioned above, the foam of this embodiment has excellent bleed-out resistance. Excellent bleed-out resistance improves the adhesive strength when the foam is bonded to a different material using an adhesive.

[0104] (Melt Flow Rate (MFR)) From the viewpoint of superior moldability, the foam of this embodiment has an MFR at a temperature of 230°C and a load of 2.16 kg, preferably 0.1 to 100 g / 10 min, more preferably 0.3 to 80 g / 10 min, even more preferably 0.5 to 80 g / 10 min, even more preferably 1.0 to 60 g / 10 min, and even more preferably 3.0 to 40 g / 10 min. The MFR can be measured in accordance with JIS K7210:1999, and more specifically, it can be measured by the method described in the examples. The MFR can also be measured from the foam.

[0105] (Foam Cells) The voids contained in the foam of this embodiment are called foam cells. These foam cells preferably contain 3 or more, more preferably 10 or more, even more preferably 20 or more, and even more preferably 30 or more, within a cross-sectional area (hereinafter simply referred to as the "observation area") with a width of 770 μm and a thickness of 1450 μm. The longer side of the foam cells is the longitudinal direction (vertical), and the shorter side is the transverse direction (horizontal). The longitudinal direction is the flow direction when molded. The transverse direction is the direction perpendicular to the longitudinal direction. From the viewpoint of superior lightness, the foam of this embodiment has an average size of foam cells observed in the observation area of ​​its cross-section that is preferably 350 μm or less, more preferably 300 μm or less, even more preferably 290 μm or less, and even more preferably 150 μm or less. Also preferably 80 μm or more, more preferably 85 μm or more, even more preferably 90 μm or more, and even more preferably 100 μm or more. From the above, the average size of the foam cells observed in the observation area of ​​the cross-section is preferably 80 μm or more and 350 μm or less, more preferably 85 μm or more and 300 μm or less, even more preferably 90 μm or more and 290 μm or less, and even more preferably 100 μm or more and 150 μm or less. The above average size is the average size of the maximum value in the longitudinal direction of the foam cells. The average size of the maximum value in the longitudinal direction of the foam cells is larger than the average size of the maximum value in the short direction of the foam cells. The average size of the foam cells can be measured by the method described in the examples. In other words, the average size of the maximum value in the longitudinal direction of the foam cells and the average size of the maximum value in the short direction of the foam cells can be measured by the method described in the examples. From the viewpoint of superior lightness, the average size of the maximum value in the short direction of the foam cells is preferably 230 μm or less, more preferably 200 μm or less, even more preferably 195 μm, and even more preferably 190 μm or less. Furthermore, the particle size is preferably 60 μm or more, more preferably 70 μm or more, even more preferably 75 μm or more, and even more preferably 80 μm or more. That is, preferably 60 to 230 μm, more preferably 70 to 200 μm, even more preferably 75 to 195 μm, and even more preferably 80 to 190 μm. The aspect ratio is defined as the ratio of the maximum value of the longitudinal dimension of each foam cell to the maximum value of the short-side dimension of the same foam cell.From the viewpoint of homogeneity, the foam of this embodiment preferably has an average aspect ratio of all foam cells observed in the observation area of ​​its cross-section that is 2.5 or less, more preferably 2.2 or less, even more preferably 1.9 or less, and even more preferably 1.7 or less. The aspect ratio can be measured by the method described in the examples. From the viewpoint of homogeneity, the foam of this embodiment preferably has a standard deviation of 200 or less, more preferably 190 or less, for the maximum value of the longitudinal dimension of the foam cells observed in the observation area of ​​its cross-section, and preferably a standard deviation of 200 or less, more preferably 190 or less, for the maximum value of the short-side dimension. The longitudinal dimension is the dimension in the longitudinal direction at the cross-section of the foam. The longitudinal direction is the flow direction at the time of molding. The short-side dimension is the dimension in the short direction at the cross-section of the foam. These ranges of standard deviation can be achieved, for example, by controlling the viscoelasticity of the foam. The standard deviation can be measured by the method described in the examples.

[0106] [Method for Manufacturing Foam] The method for manufacturing foam according to the embodiment of the present invention is the method for manufacturing foam according to the embodiment described above. From the viewpoint of obtaining a foam that is lightweight and has excellent bleed-out resistance, and a foam that has little impact on the environment and the human body, the method for manufacturing foam according to the embodiment of the present invention preferably includes a foaming step in which the foam material is foamed using a supercritical fluid.

[0107] A supercritical fluid is a substance in a state where it is subjected to temperatures and pressures above its critical point. Any substance can be used as a supercritical fluid, but examples include carbon dioxide and nitrogen. From the viewpoint of obtaining fine and uniform foam cells, nitrogen is preferred as the supercritical fluid.

[0108] Examples of foaming methods in the foaming process include known foaming processes. Specifically, batch-type supercritical foaming and supercritical injection foaming can be mentioned. Supercritical injection foaming is preferable from the standpoint of high yield.

[0109] When supercritical injection foaming is employed, the foaming process typically includes a step of mixing the foam material and the supercritical fluid in the cylinder of an injection molding machine. Furthermore, when supercritical injection foaming is employed, the foaming process typically includes a step of releasing the pressure on the mixture of the foam material and the supercritical fluid, which is under pressure in a mold within the injection molding machine, thereby causing the foam material to foam.

[0110] The molding temperature in the foaming process is usually set according to the foam material, but is typically within the range of 100 to 330°C, 150 to 300°C, or 200 to 290°C.

[0111] <Applications of the foam> The foam of this embodiment is excellent in terms of lightness and bleed-out resistance, and is therefore suitable for molded bodies that require lightness and bleed-out resistance. The footwear sole containing the foam of this embodiment is one embodiment of the present invention. The footwear sole may be the midsole of the footwear or the outsole of the footwear. It may also be a footwear sole in which the midsole and outsole are integrated.

[0112] [Molded Body] The molded body of this embodiment is a molded body of the foam of this embodiment. Specific examples of molded bodies include: soles for footwear such as hiking boots, sandals, safety shoes, mountaineering boots, marathon shoes, sneakers, men's shoes, women's safety shoes and work shoes, tabi boots, and rubber boots; sports equipment such as swimming goggles, snorkels, ski boots, and skis / snowboards; writing instruments such as pens and scissors; tools and power tools such as screwdrivers, pliers, and wrenches; plumbing supplies such as toothbrushes and kitchen utensils (knives, spatulas, etc.); equipment used for sports and fitness such as golf clubs, ski poles, bicycles, and motorcycles; various grips for knives, etc.; parts for home appliances such as refrigerators, vacuum cleaners, and waterproof bodies (mobile phones, etc.); side moldings, racks, and pins. It can be suitably used in automotive parts such as on-boots, suspension boots, constant velocity joint boots, weatherstrips, mudguards, floor mats, armrests, beltline moldings, flush mounts, and automotive interior and exterior parts (gears, knobs, etc.); tread components for tires, especially winter tires, studless tires, all-season tires, fuel-efficient tires, and heavy-duty tires; office equipment such as copier feed rollers and winding rollers; parts used in furniture such as sofas and chair seats; rubber parts such as switch covers, stoppers, casters, and foot rubbers; building materials such as covered plywood and covered steel plates; and industrial components such as industrial belts and industrial rubber hoses. Among these, it is particularly suitable for footwear soles. Examples include furniture corner guards, cushioned carpets, and collision prevention cushions. In the robotics field, examples of cushioning materials include cushioning materials for factory robots, building management robots, person-guiding robots, communication robots, and caregiving robots. In the field of sports, cushioning materials have applications such as protective gear for ball games and protective gear for martial arts. Because cushioning materials have excellent tactile properties, they are particularly preferably used in the field of automated motion devices (robots). In other words, cushioning materials are particularly preferably used as cushioning materials for robots.

[0113] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these.

[0114] The components used in the examples and comparative examples are as follows:

[0115] [Block Copolymer (I)] ・Block copolymer mixture (Ia): Produced in Production Example 1 described below ・Block copolymer mixture (Ib): Produced in Production Example 2 described below ・Block copolymer mixture (Ic): Produced in Production Example 3 described below ・Block copolymer (Id): Produced in Production Example 4 described below ・Block copolymer (Ie): Produced in Production Example 5 described below ・Block copolymer (If): Produced in Production Example 6 described below ・Block copolymer (Ig): Produced in Production Example 7 described below ・Block copolymer (Ih): Produced in Production Example 8 described below ・Block copolymer (Ii): Maleic anhydride-modified SEBS (MAh-modified SEBS) manufactured by TSRC, product name "TAIPOL® 7126" ・Block copolymer (Ij): Produced in Production Example 9 described below ・Block copolymer (Ik): Produced in Production Example 10 described below ・Block copolymer (Il): SEBS manufactured by TSRC, product name "TAIPOL® 6151" In the following explanation, block copolymer mixtures (Ia) to (Ic) and block copolymers (Id) to (Il) may be referred to as "block copolymer (I)".

[0116] [Olefin Resin (II)] ・Olefin Resin (IIa): Random polypropylene manufactured by Prime Polymer Co., Ltd., product name "J226T", MFR (temperature 230℃, load 2.16kg): 18g / 10min. ・Olefin Resin (IIb): Low-density polyethylene (LDPE) manufactured by Asia Polymer Corporation, product name "C4300", MFR (temperature 190℃, load 2.16kg): 3.8g / 10min.

[0117] • Olefin resin (IIc): EVA manufactured by Asia Polymer Corporation, product name "EV302", VA content: 8%, MFR (temperature 190°C, load 2.16 kg): 3.0 g / 10 min. • Olefin resin (IId): EVA manufactured by Asia Polymer Corporation, product name "V18161", VA content: 18%, MFR (temperature 190°C, load 2.16 kg): 16 g / 10 min. • Olefin resin (IIe): EVA manufactured by Asia Polymer Corporation, product name "V26061", VA content: 26%, MFR (temperature 190°C, load 2.16 kg): 6.0 g / 10 min. - Olefin resin (IIf): LLDPE manufactured by FORMOSA PLASTICS, product name "3220", MFR (temperature 190°C, load 2.16 kg): 1.9 g / 10 min. - Olefin resin (IIg): POE manufactured by The Chemical Company, product name "Engage 8411", MFR (temperature 190°C, load 2.16 kg): 18 g / 10 min. [Plasticizer (III)] - Plasticizer (IIIa): Paraffin-based process oil manufactured by Idemitsu Kosan Co., Ltd., product name "Diana Process PW-90"

[0118] [Polyurethane Elastomer (IV)] • Polyurethane Elastomer (IVa): Polyurethane elastomer manufactured by BASF, product name "Elastran SP9552"

[0119] <Production Examples 1-10> The details of the measurement method for the block copolymer (I) obtained in each production example are as follows.

[0120] (1) Measurement of weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) The weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the triblock copolymer (I-1) and diblock copolymer (I-2) were determined by GPC (gel permeation chromatography) using standard polystyrene equivalent molecular weight. Block copolymer (I) was used as the measurement target, and the following measurement apparatus and conditions were used. Note that the units of Mw and Mn measured by GPC are g / mol. - Equipment: GPC instrument "HLC-8320GPC" manufactured by Tosoh Corporation - Separation column: Column "TSKgelSuperHZ4000" manufactured by Tosoh Corporation - Eluent: Tetrahydrofuran - Eluent flow rate: 0.7 mL / min - Sample concentration: 5 mg / 10 mL - Column temperature: 40°C It was confirmed that the Mw and Mw / Mn measured as described above were equivalent to the Mw and Mw / Mn measured using the foam material described later.

[0121] (2) Method for measuring the hydrogenation rate The unhydrogenated block copolymer (I) before hydrogenation and the hydrogenated block copolymer (I) after hydrogenation are measured in CDClone. ３ Dissolve in it, １ ¹H-NMR measurements were performed [instrument: "AVANCE 400 Nano bay" (Bruker), measurement temperature: 30°C]. The hydrogenation rate of carbon-carbon double bonds in structural units derived from conjugated diene compounds in block copolymer (I) was calculated from the proton peaks of carbon-carbon double bonds appearing at 4.5–6.0 ppm in the obtained spectrum using the following formula: Hydrogenation rate (mol%) = {1 - (number of moles of carbon-carbon double bonds per mole of hydrogenated block copolymer (I)) / (number of moles of carbon-carbon double bonds per mole of unhydrogenated block copolymer (I))} × 100. It was confirmed that the hydrogenation rate measured as described above was equivalent to the hydrogenation rate measured on the foam described later.

[0122] (3) Method for measuring the amount of vinyl bonds in block copolymer (I) The term "amount of vinyl bonds" refers to the content (mol%) of vinyl bond units in the block copolymer (I) in 100 mol% of the total amount of structural units derived from the conjugated diene compound. The unhydrogenated block copolymer (I) before hydrogenation is prepared by CDCl ３ Dissolve in it, １ H-NMR measurements were performed [equipment: "AVANCE 400 Nano bay" (manufactured by Bruker), measurement temperature: 30°C].

[0123] When polymer block (b) contains structural units derived from isoprene but does not contain structural units derived from butadiene, the amount of vinyl bonding was calculated from the ratio of the peak areas of 3,4-bonding units and 1,2-bonding units in the isoprene-derived structural units to the total peak area of ​​the isoprene-derived structural units. When polymer block (b) contains structural units derived from butadiene but does not contain structural units derived from isoprene, the amount of vinyl bonding was calculated from the ratio of the peak area of ​​1,2-bonding units in the butadiene-derived structural units to the total peak area of ​​the butadiene-derived structural units. When polymer block (b) contains both structural units derived from butadiene and structural units derived from isoprene, the amount of vinyl bonding was calculated from the ratio of the peak areas of 1,2-bonding units in the butadiene-derived structural units and 1,2-bonding units and 3,4-bonding units in the isoprene-derived structural units to the total peak areas of the butadiene-derived structural units and isoprene-derived structural units. Furthermore, it was confirmed that the amount of vinyl binding measured as described above was equivalent to the amount of vinyl binding measured using the foam material described later.

[0124] <Preparation of Block Copolymer (I)> [Preparation Example 1] (Block Copolymer (Ia)) 4.58 kg of α-methylstyrene, 7.42 kg of cyclohexane, and 0.091 kg of tetrahydrofuran were charged into a nitrogen-purged pressure vessel with a stirring device. 0.4232 kg of sec-butyllithium (10.5% by mass cyclohexane solution) was added to this mixture, and polymerization was carried out at -10°C for 3 hours to form poly-α-methylstyrene. The weight-average molecular weight (Mw) of the obtained poly-α-methylstyrene was 6,600, and the polymerization conversion rate was 89%. Next, 1.82 kg of 1,3-butadiene was added to this reaction mixture, and polymerization was carried out by stirring at -10°C for 30 minutes, after which 42.58 kg of cyclohexane was added. At this point, the polymerization conversion rate of α-methylstyrene was 89%, and the weight-average molecular weight (GPC measurement, equivalent to standard polystyrene) of the polybutadiene block of the formed poly-α-methylstyrene-polybutadiene diblock copolymer was 3,700. １ The amount of vinyl bond determined by 1H-NMR measurement was 81 mol%. Next, 9.38 kg of 1,3-butadiene was added to this reaction solution, and the polymerization reaction was carried out at 50°C for 2 hours. The weight-average molecular weight (Mw) of the resulting polybutadiene block copolymer was 29,300. １ The amount of vinyl bond determined by 1H-NMR measurement was 43 mol%. Next, 0.0328 kg of phenyl benzoate was added to this polymerization reaction solution and stirred at 50°C for 1 hour to obtain a mixture containing poly-α-methylstyrene-polybutadiene-poly-α-methylstyrene triblock copolymer (in Table 1, "α-St-Bd-α-St") and poly-α-methylstyrene-polybutadiene diblock copolymer (in Table 1, "α-St-Bd"). It was confirmed that no other block copolymers were present in this mixture (they were below the detection limit). At this time, the weight ratio of poly-α-methylstyrene-polybutadiene-poly-α-methylstyrene triblock copolymer (weight-average molecular weight (Mw) = 78,000) to poly-α-methylstyrene-polybutadiene diblock copolymer (weight-average molecular weight (Mw) = 35,900), calculated from the area ratio of UV absorption in GPC, was 90% by mass for the triblock copolymer and 10% by mass for the diblock copolymer.１ ¹H-NMR analysis revealed that the total content of poly-α-methylstyrene blocks (the two polymer blocks (a)) in the poly-α-methylstyrene-polybutadiene-poly-α-methylstyrene triblock copolymer and poly-α-methylstyrene-polybutadiene diblock copolymer was 29% by mass, and the amount of vinyl bonding in the polybutadiene block (polymer block (b)) was 43 mol%. A Ziegler-type hydrogenation catalyst formed from nickel octyolate and triisobutylaluminum was added to the polymerization reaction solution obtained above under a hydrogen atmosphere, and a hydrogenation reaction was carried out at a hydrogen pressure of 0.8 MPa and 80°C for 5 hours to obtain a block copolymer mixture containing hydrogenated poly-α-methylstyrene-polybutadiene-poly-α-methylstyrene triblock copolymer and hydrogenated poly-α-methylstyrene-polybutadiene diblock copolymer (hereinafter, this mixture will be abbreviated as block copolymer (Ia)). The obtained block copolymer (Ia) was melt-kneaded using a Coperion twin-screw extruder "ZSK26 MagaCopounder" (L / D = 56) at a screw speed of 300 rpm and a kneading temperature of 200°C to obtain granules. The above physical properties were measured for the block copolymer (Ia). The results are shown in Table 1.

[0125] [Production Example 2] (Block Copolymer (Ib)) In a nitrogen-purged and dried pressure vessel, 50.0 kg of cyclohexane was charged as the solvent, 0.2362 kg of sec-butyllithium (10.5% by mass cyclohexane solution) as an anionic polymerization initiator, and 0.090 kg of tetrahydrofuran as a Lewis base. After raising the temperature to 50°C, 2.05 kg of styrene was added and polymerization was carried out for 1 hour, followed by the addition of 13.8 kg of butadiene and polymerization was carried out for 2 hours to obtain a reaction solution containing a polystyrene-polybutadiene diblock copolymer (in Table 1, "St-Bd"). Subsequently, 0.0128 kg of phenyl benzoate (in 0.5 M toluene solution) was added to this reaction solution and stirred at 50°C for 1 hour to obtain a polystyrene-polybutadiene-polystyrene triblock copolymer (in Table 1, "St-Bd-St") in which a portion of the polystyrene-polybutadiene diblock copolymer was linked via a coupling agent. To the above reaction solution, palladium carbon (palladium loading: 5% by mass) was added at a concentration of 5% by mass relative to the block copolymer as a hydrogenation catalyst, and the reaction was carried out for 10 hours under conditions of hydrogen pressure of 2 MPa and 150°C. After cooling and release of pressure, the hydrogenation catalyst was removed by filtration, the filtrate was concentrated, and further vacuum-dried to obtain a block copolymer mixture (block copolymer (Ib)) containing hydrogenated polystyrene-polybutadiene diblock copolymer (SEB) and hydrogenated polystyrene-polybutadiene-polystyrene triblock copolymer (SEBS). The obtained block copolymer (Ib) was granulated using the same method as in Production Example 1. The above physical properties of block copolymer (Ib) were measured. The results are shown in Table 1.

[0126] [Production Example 3] (Block Copolymer (Ic)) (1. Production of Hydrogenated Triblock Copolymer (SEPS)) In a nitrogen-purged and dried pressure vessel, 50.0 kg of cyclohexane was charged as the solvent and 0.0611 kg of sec-butyllithium (10.5% by mass cyclohexane solution) was charged as an anionic polymerization initiator. After raising the temperature to 50°C, 0.81 kg of styrene (first time) was added and polymerization was carried out for 1 hour, followed by the addition of 10.87 kg of isoprene and polymerization was carried out for 2 hours, and then 0.81 kg of styrene (second time) was added and polymerization was carried out for 1 hour to obtain a reaction solution containing a polystyrene-polyisoprene-polystyrene triblock copolymer (in Table 1, "St-Ip-St"). It was confirmed that no other block copolymers were present in this reaction solution (they were below the detection limit). To this reaction solution, 5% by mass of palladium carbon (palladium loading: 5% by mass) was added to the block copolymer as a hydrogenation catalyst, and the reaction was carried out for 10 hours under conditions of hydrogen pressure of 2 MPa and 150°C. After cooling and release of pressure, the palladium carbon was removed by filtration, the filtrate was concentrated, and further vacuum-dried to obtain hydrogenated polystyrene-polyisoprene-polystyrene triblock copolymer (SEPS). (2. Production of Hydrogenated Diblock Copolymer (SEP)) In the same manner as for SEPS, 50.0 kg of cyclohexane was charged as a solvent and 0.4200 kg of sec-butyllithium (10.5% by mass cyclohexane solution) (44.1 g of sec-butyllithium) as an anionic polymerization initiator into a nitrogen-purged and dried pressure vessel. After raising the temperature to 50°C, 2.83 kg of styrene was added and polymerization was carried out for 1 hour, followed by the addition of 19.81 kg of isoprene and polymerization was carried out for 2 hours to obtain a reaction solution containing a polystyrene-polyisoprene diblock copolymer (in Table 1, "St-Ip"). It was confirmed that no other block copolymers were present in this reaction solution (they were below the detection limit). Hydrogenation was carried out in the same manner as for SEPS to obtain a hydrogenated polystyrene-polyisoprene diblock copolymer (SEP).(3. Production of Block Copolymer (Ic)) The SEPS and SEP obtained above were melt-kneaded using a Coperion twin-screw extruder "ZSK26 MagaCopounder" (L / D = 56) at a screw speed of 300 rpm and a kneading temperature of 200°C to obtain a block copolymer (Ic), which is a mixture of SEPS and SEP. The physical properties of the block copolymer (Ic) were measured as described above. The results are shown in Table 1.

[0127] [Production Example 4] (Block Copolymer (Id)) In a nitrogen-purged and dried pressure vessel, 50 kg of cyclohexane was charged as the solvent, and 87 g of a cyclohexane solution of sec-butyllithium at a concentration of 10.5% by mass as an anionic polymerization initiator (substantial amount of sec-butyllithium added: 9.1 g). After raising the temperature inside the pressure vessel to 50°C, 1.00 kg of styrene (first time) was added and polymerization was carried out for 1 hour. At a vessel temperature of 50°C, 0.32 kg of 2,2-di(2-tetrahydrofuryl)propane (DTHFP) was added as a Lewis base, followed by the addition of 16.64 kg of isoprene, and polymerization was carried out for 2 hours. This formed a polystyrene-polyisoprene diblock copolymer. Subsequently, 1.00 kg of styrene (second time) was added and polymerization was carried out for 1 hour to obtain a reaction solution containing a polystyrene-polyisoprene-polystyrene triblock copolymer (in Table 1, "St-Ip-St"). It was confirmed that no diblock copolymer was present in the reaction solution (it was below the detection limit). A Ziegler-type hydrogenation catalyst formed from nickel octylate and triisobutylaluminum was added to the reaction solution under a hydrogen atmosphere, and the reaction was carried out for 5 hours under conditions of a hydrogen pressure of 1 MPa and 80°C. After the reaction solution was allowed to cool and the pressure was released, the catalyst was removed by washing with water, and the mixture was vacuum-dried to obtain a hydrogenated product of the polystyrene-polyisoprene-polystyrene triblock copolymer (block copolymer (Id)). The obtained block copolymer (Id) was granulated using the same method as in Production Example 1. The above physical properties of block copolymer (Id) were measured. The results are shown in Table 1.

[0128] [Production Example 5] (Block Copolymer (Ie)) In a nitrogen-purged and dried pressure vessel, 50.0 kg of cyclohexane was charged as the solvent, 0.184 kg of sec-butyllithium (10.5% by mass cyclohexane solution) as an anionic polymerization initiator, and 0.118 kg of tetrahydrofuran as a Lewis base. After raising the temperature to 50°C, 2.37 kg of p-methylstyrene (first time) was added and polymerization was carried out for a time, then 11.1 kg of butadiene was added and polymerization was carried out for 2 hours, and then 2.37 kg of p-methylstyrene (second time) was added and polymerization was carried out for 1 hour. This yielded a reaction solution containing a triblock copolymer of poly-p-methylpolystyrene-poly(butadiene)-poly-p-methylstyrene (in Table 1, "p-St-Bd-p-St"). It was confirmed that no diblock copolymer was present in this reaction solution (it was below the detection limit). A Ziegler-type hydrogenation catalyst formed from nickel octoate and triisobutylaluminum was added to the reaction solution under a hydrogen atmosphere, and the reaction was carried out for 5 hours under conditions of a hydrogen pressure of 1 MPa and 80°C. After cooling and release of pressure, the hydrogenation catalyst was removed by filtration, the filtrate was concentrated, and further vacuum-dried to obtain a hydrogenated product of a triblock copolymer of poly-p-styrene-poly(butadiene)-poly-p-styrene (block copolymer (Ie)). The obtained block copolymer (Ie) was granulated using the same method as in Production Example 1. The above physical properties of the block copolymer (Ie) were measured. The results are shown in Table 1.

[0129] [Production Example 6] (Block Copolymer (If)) In a nitrogen-purged and dried pressure vessel, 50.0 kg of cyclohexane was charged as the solvent and 0.1647 kg of sec-butyllithium (10.5% by mass cyclohexane solution) as an anionic polymerization initiator. After raising the temperature to 50°C, 1.32 kg of styrene (first time) was added and polymerization was carried out for 1 hour, and then 6.18 kg of isoprene was added and polymerization was carried out for 2 hours. This formed a polystyrene-polyisoprene diblock copolymer. Subsequently, 1.32 kg of styrene (second time) was added and polymerization was carried out for 1 hour to obtain a reaction solution containing a polystyrene-polyisoprene-polystyrene triblock copolymer (in Table 1, "St-Ip-St"). It was confirmed that no diblock copolymer was present in this reaction solution (it was below the detection limit). To the above reaction solution, 5% by mass of palladium carbon (palladium loading: 5% by mass) was added to the block copolymer as a hydrogenation catalyst, and the reaction was carried out for 10 hours under conditions of hydrogen pressure of 2 MPa and 150°C. After cooling and pressure release, the hydrogenation catalyst was removed by filtration, the filtrate was concentrated, and then vacuum-dried to obtain a hydrogenated polystyrene-polyisoprene-polystyrene triblock copolymer (block copolymer (If)). The obtained block copolymer (If) was granulated using the same method as in Production Example 1. The above physical properties of block copolymer (If) were measured. The results are shown in Table 1.

[0130] [Production Example 7] (Block Copolymer (Ig)) In a nitrogen-purged and dried pressure vessel, 50.0 kg of cyclohexane was added as the solvent, 0.1028 kg of sec-butyllithium (10.5% by mass cyclohexane solution) as an anionic polymerization initiator, and 0.073 kg of tetrahydrofuran as a Lewis base. After raising the temperature to 50°C, 1.32 kg of styrene (first time) was added and polymerization was carried out for a time, then 6.18 kg of butadiene was added and polymerization was carried out for 2 hours, and then 1.32 kg of styrene (second time) was added and polymerization was carried out for 1 hour. This yielded a reaction solution containing a triblock copolymer of polypolystyrene-poly(butadiene)-polystyrene (in Table 1, "St-Bd-St"), and it was confirmed that no diblock copolymer was present in this reaction solution (it was below the detection limit). To the above reaction solution, 5% by mass of palladium carbon (palladium loading: 5% by mass) was added to the block copolymer as a hydrogenation catalyst, and the reaction was carried out for 10 hours under conditions of hydrogen pressure of 2 MPa and 150°C. After cooling and depressurization, the hydrogenation catalyst was removed by filtration, the filtrate was concentrated, and then vacuum-dried to obtain a hydrogenated polystyrene-poly(butadiene)-polystyrene triblock copolymer (block copolymer (Ig)). The obtained block copolymer (Ig) was granulated using the same method as in Production Example 1. The above physical properties were measured for block copolymer (Ig). The results are shown in Table 1.

[0131] [Production Example 8] (Block Copolymer (Ih)) In a nitrogen-purged and dried pressure vessel, 50.0 kg of cyclohexane was charged as the solvent and 0.1541 kg of sec-butyllithium (10.5% by mass cyclohexane solution) as an anionic polymerization initiator. After raising the temperature to 50°C, 1.21 kg of styrene (first time) was added and polymerization was carried out for 1 hour. Then, a mixture of 3.57 kg of isoprene and 2.83 kg of butadiene was added and polymerization was carried out for 2 hours. This formed a polystyrene-poly(butadiene / isoprene) copolymer. Subsequently, 1.21 kg of styrene (second time) was added and polymerization was carried out for 1 hour, and then 12 g of ethylene oxide was added to obtain a reaction solution containing a polystyrene-poly(butadiene / isoprene)-polystyrene triblock copolymer (in Table 1, "St-(Ip / Bd)-St-OH") containing hydroxyl groups at the ends. The above reaction solution was hydrogenated in the same manner as in Production Example 7 to obtain a hydrogenated product of polystyrene-poly(butadiene / isoprene)-polystyrene triblock copolymer (block copolymer (Ih)). The obtained block copolymer (Ih) was granulated in the same manner as in Production Example 1. The above physical properties of the block copolymer (Ih) were measured. The results are shown in Table 1.

[0132] [Production Example 9] (Block Copolymer (Ij)) A hydrogenated product of a polystyrene-polyisoprene-polystyrene triblock copolymer ("St-Ip-St" in Table 1) (block copolymer (Ij)) was obtained in the same manner as in Production Example 6, except that the amounts of sec-butyllithium, styrene (first time), styrene (second time), and isoprene were changed to the amounts shown in Table 1. The obtained block copolymer (Ij) was granulated using the same method as in Production Example 1. The above physical properties of the block copolymer (Ij) were measured. The results are shown in Table 1.

[0133] [Production Example 10] (Block Copolymer (Ik)) A hydrogenated product of a triblock copolymer of polystyrene-polybutadiene-polystyrene ("St-Bd-St" in Table 1) (block copolymer (Ik)) was obtained in the same manner as in Production Example 7, except that the amounts of sec-butyllithium, styrene (first time), styrene (second time), butadiene, and tetrahydrofuran used were changed to the amounts shown in Table 1. The obtained block copolymer (Ik) was granulated using the same method as in Production Example 1. The above physical properties of the block copolymer (Ik) were measured. The results are shown in Table 1.

[0134]

[0135] [Examples 1-15 and Comparative Examples 1 and 2] By performing a foaming process using a supercritical fluid with the foam material having the composition (parts by mass) described in Tables 2 and 3, a sheet-like foam with a width of 150-200 mm, a length of 150-200 mm, and a thickness of 20 mm was produced.

[0136] For the production of the foam, a TIENKANG SCF injection molding machine, model "Gentrex TK-927-12S," was used. This injection molding machine consisted of an injection system including a cylinder, a runner control unit including a sprue connected to the injection system, and a mold connected to the sprue. The injection system included a supply port for supplying the foam material, a supply port for supplying the supercritical fluid, a heating device for melting the supplied foam material, and an injection port for supplying the molten foam material and supercritical fluid to the runner. The sprue branched into three branches towards the mold and was connected to the mold cavity. The maximum length of the sprue was 200 mm.

[0137] Nitrogen was used as the supercritical fluid (SCF). The supercritical fluid was mixed with the foam material in the cylinder of the injection molding machine. The injection pressure was 20–80 kg / cm². ２The process was controlled within the specified range. The molding temperatures used were those listed in Tables 2 and 3. The molding temperature was set to the cylinder temperature of the injection molding machine. The foaming process described above included supplying a mixture of the foam material and the supercritical fluid to a mold in the injection molding machine, thereby releasing the pressure on the mixture of the foam material and the supercritical fluid under pressure, and causing the foam material to foam. The pressure inside the mold was adjusted so that the nitrogen used remained in a supercritical state until the pressure was released as described below. As a result of the pressure release, the nitrogen used was released from its supercritical state and released outside the injection molding machine. The cooling time for the foam inside the mold was set to 300 to 600 seconds. The cooling time was defined as the time from immediately after injection, through the time spent in the cooling station (10 stations), to the time the mold was opened.

[0138] Various evaluations were performed on the obtained foam. The results are shown in Tables 2 and 3. Note that various evaluations could not be performed on the material composition of the foam in Comparative Example 2 because it was not possible to obtain the foam using a supercritical fluid. However, even if the foam had been obtained, the use of a plasticizer would have resulted in poor bleed-out resistance.

[0139]

[0140]

[0141] <Evaluation of Foams> [1. Measurement of Specific Gravity and Evaluation of Lightweight Properties] The specific gravity of the foams obtained in the examples and comparative examples was measured using a hydrometer in accordance with ISO 1183:1987. The unit of specific gravity is dimensionless, but it is the unit of density, g / cm³. ３ This can be considered the same. The hydrometer used was the "MDS-300" manufactured by Alpha Mirage Co., Ltd. If the specific gravity value was less than 0.36, it was evaluated as having excellent lightweight properties (indicated as "G" in Tables 2 and 3), and if it was 0.36 or higher, it was evaluated as not having excellent lightweight properties (indicated as "NG" in Tables 2 and 3).

[0142] [2. Measurement of Storage Modulus] (1) Non-foamed sheet manufacturing The foam material of the examples and comparative examples was used to produce 1 mm thick non-foamed sheets at a temperature of 200 to 230°C using a press molding machine manufactured by Toyo Seiki Seisakusho Co., Ltd. (2) Measurement of Storage Modulus G' A disc-shaped test piece with a diameter of 8 mm and a thickness of 1 mm was cut from the above non-foamed sheet. Dynamic viscoelasticity measurements were performed on this test piece using the following dynamic viscoelasticity measuring device under the following measurement conditions, and the storage moduli at 150°C, 170°C, and 250°C (denoted as G'(150), G'(170), and G'(250), respectively) were measured. (Dynamic viscoelasticity measuring device and measurement conditions) ・Dynamic viscoelasticity measuring device: "ARES-G2 rheometer" manufactured by TA Instruments ・Parallel plate: 8 mm in diameter ・Vibration mode: Torsional vibration ・Strain amount: 0.1% ・Frequency: 1 Hz ・Measurement temperature: 260°C to -50°C ・Heating rate: 10°C / min

[0143] [3. Measurement of Hardness] The Type C hardness of the foams obtained in the examples and comparative examples was measured in accordance with ISO 2349:2015. A "Type C hardness tester" manufactured by Asuka Corporation was used as the hardness measuring device. The measurement condition was "Skin on".

[0144] [4. Measurement of Compression Set] The compression set of the foams obtained in the examples and comparative examples was measured according to Method B of ASTM D395-16. The measurement conditions were 40°C, 50% compression, and 6 hours. The ASTM-D395 compression set apparatus manufactured by Amade Tech was used as the apparatus.

[0145] [5. Evaluation of Bleed-Out Resistance] A 40 mm x 40 mm x 1 mm sheet was cut out as a test specimen from the foam obtained in the examples and comparative examples. The test specimen was left in a 60°C oven for 3 days. After that, the test specimen was removed from the oven. The presence or absence of oil on the hand when touching the surface of the test specimen was checked. If oil was present, it was evaluated as "Oil bleed present at high temperature" (NG in Tables 2 and 3), and if no oil was present, it was evaluated as "No oil bleed present at high temperature" (G in Tables 2 and 3). The presence or absence of oil was judged by touch.

[0146] [6. Measurement of Melt Flow Rate (MFR)] Using the foam obtained in the examples and comparative examples, press sheets with a thickness of 1 mm were produced at a temperature of 200 to 230°C using a press molding machine manufactured by Toyo Seiki Seisakusho Co., Ltd. The press sheets were cut to a size that could be fed into the barrel, and the melt flow rate (MFR) was measured in accordance with JIS K7210:1999 using an MFR measuring device under the following measurement conditions. The results are shown in Tables 2 and 3. (Measurement conditions) ・MFR measuring device: Melt indexer L244 (manufactured by Techno Seven Co., Ltd.) ・Temperature: 230°C ・Load: 2.16 kg ・Die: Standard die (diameter: 2.095 mm, length: 8.000 mm)

[0147] [7. Cross-sectional observation] A circular region with a radius of 50 mm was cut out from the center of one main surface of the foam obtained in the examples and comparative examples. Subsequently, a surface parallel to the main surface was cut out from the aforementioned main surface of the cut-out region, 10 mm away in the thickness direction, thereby exposing the surface. The exposed surface was then observed at a magnification of 5x using a stereomicroscope (Nikon's "ECLIPSE E600 POL"). Foam cells (voids) were observed on the exposed surface. Foam cells located within a cross-sectional region of the exposed surface with a width of 770 μm and a thickness of 1450 μm (hereinafter simply referred to as the "observation region") were selected for observation. One end of the observation region in the thickness direction was near the sprue connection position. Specifically, all foam cells within the above observation region were selected for observation. To identify the foam cells, first, the observation region of the stereomicroscope was projected onto a monitor, and then voids that could be visually confirmed were identified as foam cells. In this process, the longer side of the foam cell was designated as the longitudinal direction (vertical), and the shorter side as the transverse direction (horizontal). However, the transverse direction was defined as being perpendicular to the longitudinal direction.

[0148] (1) Average size of the maximum value of the longitudinal dimension The maximum value of the longitudinal dimension of each foam cell observed in the observation area of ​​the cross-section of the foam was summed up for all foam cells. The obtained sum was divided by the number of foam cells and measured as the average size of the maximum value of the longitudinal dimension.

[0149] (2) Standard deviation of the maximum value of the longitudinal dimension Based on the maximum value of the longitudinal dimension of each foam cell obtained in (1) above and the number of foam cells, the standard deviation of the maximum value of the longitudinal dimension of the foam cell was calculated based on the following formula 1. ... (Equation 1) In Equation 1 above, σ ２ = variance, μ = mean value, x ｉ = The maximum value of the longitudinal dimension of each foam cell, and n = the number of data points (number of foam cells).

[0150] (3) Average size of the maximum value of the short-side dimension The maximum values ​​of the short-side dimension of all foam cells observed in the observation area of ​​the cross-section of the foam were summed up. The value obtained by dividing the sum by the number of foam cells was taken as the average size of the maximum value of the short-side dimension.

[0151] (4) Standard deviation of the maximum value of the short-side dimension Based on the maximum value of the short-side dimension of each foam cell obtained in (3) above and the number of foam cells, the standard deviation of the maximum value of the short-side dimension of the foam cell was calculated based on Equation 1 described above.

[0152] (5) Average Aspect Ratio The average aspect ratio of all foam cells in the observation area was calculated. The average aspect ratio was obtained by dividing the sum of the aspect ratios of all foam cells in the observation area by the number of foam cells.

[0153] The results in Tables 2 and 3 show that the foams containing block copolymers from Examples 1 to 15 exhibited excellent lightness and bleed-out resistance. Furthermore, Examples 1 to 15 demonstrate that a method for producing foams with excellent lightness and bleed-out resistance can be provided.

[0154] <Evaluation of recyclability> [Example 16] The foam from Example 1 was crushed in a pulverizer and pelletized, and then supercritical injection foaming was performed again in the same manner as in Example 1 to produce the foam from Example 16.

[0155] [Method for Evaluating Recyclability] The foam of Example 16 was evaluated, and its recyclability was assessed by comparing it with the foam of Example 1. In the evaluation of recyclability, specific gravity, type C hardness, and compression set were evaluated in the same way as the foams of Examples 1 to 15 and Comparative Examples 1 and 2. Breaking strength, tear strength, and elongation at break were measured according to ASTM D412. The rebound modulus was measured according to ASTM D2632. The index for each evaluation item was calculated using the following formula: Index = [Value after recycling (Example 16) / Value before recycling (Example 1)] × 100 The results are shown in Table 4.

[0156]

[0157] As is clear from Table 4, in each evaluation, Example 16, which is the foam after recycling, received almost the same evaluation results as Example 1, which is the foam before recycling, indicating excellent recyclability.

[0158] <Weather Resistance Evaluation> [Comparative Example 3] Using polyurethane elastomer (IVa), supercritical injection foaming was performed in the same manner as in Example 1 to produce the foam of Comparative Example 3.

[0159] [Method for evaluating weather resistance] Using the foams of Example 1 and Comparative Example 3, a weather resistance test was conducted in accordance with ISO 4892-3 cycle No. 1, and the change in hue was evaluated. (Test conditions) ・Lamp: UV-340 ・Emission time: 0.76 W (m) at 340 nm ２ • nm) • Test cycle: 8 hours irradiation → 4 hours dewcretion • Temperature conditions: Black panel temperature 60°C during irradiation, 50°C during dewcretion (Test specimen) • 4 mm thick dumbbell piece No. 1 (n=3) (Test time) • 10 days (Judgment criteria) No coloring: G Coloring present: NG

[0160]

[0161] As is clear from Table 5, the foam of Example 1 has superior weather resistance compared to Comparative Example 3, which is a polyurethane elastomer foam.

Claims

1. A foam containing a block copolymer (I) comprising a polymer block (a) containing structural units derived from an aromatic vinyl compound and a polymer block (b) containing structural units derived from a conjugated diene compound, wherein the storage modulus G'(150) at 150°C is 3.60 × 10⁻⁶. ４ The pressure is Pa or higher, and the storage modulus G'(250) at 250°C is 3.00 × 10⁻⁶. ４ A foam with a pressure of Pa or less.

2. The foam according to claim 1, wherein the block copolymer (I) contains a triblock copolymer (I-1), and the triblock copolymer (I-1) is a triblock copolymer containing two polymer blocks (a) and one polymer block (b) interposed between the two polymer blocks (a).

3. The foam according to claim 2, wherein the weight-average molecular weight (Mw) of the triblock copolymer (I-1) is 30,000 to 200,000.

4. The foam according to claim 2 or 3, wherein the block copolymer (I) further contains a diblock copolymer (I-2).

5. The foam according to claim 4, wherein the weight-average molecular weight (Mw) of the diblock copolymer (I-2) is 20,000 to 100,000.

6. The foam according to any one of claims 2 to 5, wherein the content of the triblock copolymer (I-1) in 100% by mass of the total amount of the block copolymer (I) is 30 to 99% by mass.

7. The foam according to any one of claims 1 to 6, wherein the aromatic vinyl compound in the polymer block (a) contains α-methylstyrene.

8. The foam according to any one of claims 1 to 7, wherein the weight-average molecular weight (Mw) of the polymer block (a) in the block copolymer (I) is 1,000 to 25,000.

9. The foam according to any one of claims 1 to 8, wherein the content of the polymer block (a) in 100% by mass of the total amount of the block copolymer (I) is 5 to 65% by mass.

10. The foam according to any one of claims 1 to 9, wherein the amount of vinyl bond in the block copolymer (I), which represents the content of vinyl bond units in 100 mol% of the total amount of structural units derived from the conjugated diene compound, is 3.0 to 90.0 mol%.

11. The foam according to any one of claims 1 to 10, further comprising an olefin resin (II), wherein the content of the olefin resin (II) in the foam is 60.0% by mass or less.

12. The foam according to any one of claims 1 to 11, further comprising a plasticizer (III), wherein the content of the plasticizer (III) in the foam is less than 5% by mass.

13. The storage modulus G' at 170°C is represented by G'(170) = 3.20 × 10⁻⁶ ４ A foam according to any one of claims 1 to 12, wherein the pressure is Pa or higher.

14. Specific gravity is 0.36 g / cm³. ３ A foam according to any one of claims 1 to 13, which is less than [amount missing].

15. The foam according to any one of claims 1 to 14, wherein the compression set at 40°C for 6 hours is less than 97%.

16. The foam according to any one of claims 1 to 15, wherein the average size, which is the value obtained by summing the maximum longitudinal dimensions of all foam cells observed in an observation area of ​​770 μm × 1450 μm on the cross-section of the foam and dividing the resulting sum by the number of foam cells, is 300 μm or less.

17. The foam according to any one of claims 1 to 16, wherein the average value of the aspect ratio of all foam cells observed in an observation area of ​​770 μm × 1450 μm on the cross-section of the foam is 1.8 or less.

18. The foam according to any one of claims 1 to 17, wherein the standard deviation of the maximum value of the longitudinal dimension of all foam cells observed in an observation area of ​​770 μm × 1450 μm on the cross-section of the foam is 200 or less, and the standard deviation of the maximum value of the short-side dimension is 200 or less.

19. The foam according to any one of claims to 18, wherein the MFR of the foam at 230°C and 2.16 kg is 0.1 to 100 g / 10 min.

20. A footwear sole comprising the foam material described in any one of claims 1 to 19.

21. A method for producing a foam according to claims 1 to 19, comprising a foaming step of foaming the foam material using a supercritical fluid.

22. The method for producing a foam according to claim 21, wherein the supercritical fluid is nitrogen.

23. The method for producing a foam according to claim 21 or 22, wherein the foaming step includes a step of mixing the foam material and the supercritical fluid in the cylinder of an injection molding machine.

Images