Block copolymer composition, heat-shrinkable film, and container

Abstract

The present invention provides a block copolymer composition that can produce a heat-shrinkable film having excellent rigidity and impact resistance, the block copolymer composition comprising a block copolymer that contains a vinyl aromatic monomeric unit and a conjugated diene monomeric unit. The block copolymer composition contains, when the combined mass of the vinyl aromatic monomeric unit and the conjugated diene monomeric unit in the block copolymer composition is 100 mass%, the conjugated diene monomeric unit at 10-30 mass%, and contains, when the combined content of the block copolymer containing a vinyl aromatic monomeric unit and a conjugated diene monomeric unit in the block copolymer composition is 100 mass%, a block copolymer A at 9-39 mass%, a block copolymer B at 6-26 mass%, and a block copolymer C at 35-85 mass%. The block copolymer A has a block structure represented by (S1)−(S / B1), the block copolymer B has a block structure represented by (S2)−(S / B2), and the block copolymer C has a block structure represented by (S3)−(S / B3)−(S / B4).

Description

Block copolymer composition, heat-shrinkable film, and container

[0001] The present invention relates to a block copolymer composition, a heat-shrinkable film, and a container.

[0002] Heat-shrinkable films using block copolymers obtained by polymerizing a vinyl aromatic compound and a conjugated diene compound are widely used for shrink packaging of labels for PET bottled beverages and the like because they have excellent heat-shrinkability and finish after shrinkage and can be adapted to various shapes and attachment methods of packaged objects (Patent Document 1).

[0003] JP 11-158241

[0004] In recent years, as the shapes of packaged items have become more complex, there has been a demand for heat-shrinkable films with high rigidity to prevent them from buckling when attached, as well as high impact resistance to prevent the label from breaking if the packaged item is dropped after the label has been attached.

[0005] However, it has been difficult to achieve both rigidity and impact resistance in a film using a block copolymer obtained by polymerizing a vinyl aromatic compound and a conjugated diene compound.

[0006] The present invention has been made in view of the above circumstances, and provides a block copolymer composition from which a heat-shrinkable film having excellent rigidity and impact resistance can be produced.

[0007] As a result of intensive research into solving the above problems, the present inventors have found that the above problems can be solved by containing several types of block copolymers containing vinyl aromatic monomer units and conjugated diene monomer units in a specific blend, and have thus completed the present invention.

[0008] According to the present invention, the following inventions are provided: [1] A block copolymer composition containing a block copolymer containing vinyl aromatic monomer units and conjugated diene monomer units, wherein the block copolymer composition contains 10 to 30% by mass of conjugated diene monomer units when the total mass of the vinyl aromatic monomer units and conjugated diene monomer units in the block copolymer composition is taken as 100% by mass, and the block copolymer composition contains 9 to 39% by mass of block copolymer A, 6 to 26% by mass of block copolymer B, and 35 to 85% by mass of block copolymer C when the total content of the block copolymers containing vinyl aromatic monomer units and conjugated diene monomer units in the block copolymer composition is taken as 100% by mass, wherein the block copolymer A has a block structure represented by (S1)-(S / B1), (S1) is a block containing 85 to 100% by mass of vinyl aromatic monomer units, (S / B1) is a tapered block containing vinyl aromatic monomer units and conjugated diene monomer units, and containing 20 to 60% by mass of conjugated diene monomer units; the block copolymer A contains 5 to 15% by mass of conjugated diene monomer units; the block copolymer B has a block structure represented by (S2)-(S / B2); (S2) is a block containing 85 to 100% by mass of vinyl aromatic monomer units; (S / B2) is a tapered block containing vinyl aromatic monomer units and conjugated diene monomer units, and containing 20 to 60% by mass of conjugated diene monomer units; the block copolymer B contains more than 15% by mass and 50% by mass or less of conjugated diene monomer units; and the block copolymer C has a block structure represented by (S3)-(S / B3)-(S / B4). a block copolymer composition comprising: (S3) a block containing 85 to 100% by mass of vinyl aromatic monomer units; (S / B3) and (S / B4) each a tapered block containing vinyl aromatic monomer units and conjugated diene monomer units, and containing 8 to 36% by mass of conjugated diene monomer units; and (S / B4) a block copolymer composition comprising: (S / B4) / (S / B3)=0.6 to 5.5;[2] The block copolymer resin composition according to [1], wherein the block copolymer resin composition has, in a molecular weight distribution measured by GPC, at least one molecular weight peak in a weight average molecular weight range of 140,000 to 220,000, and at least one molecular weight peak in a weight average molecular weight range of 50,000 to 90,000, in terms of polystyrene equivalent molecular weights. [3] The block copolymer resin composition according to [1] or [2], wherein the block copolymer resin composition has a flexural modulus of 1,300 MPa or more, measured in accordance with ISO 178 using a type A test piece conforming to ISO 3167. [4] The block copolymer composition according to any one of [1] to [3], further comprising a block copolymer D, wherein the block copolymer D has a block structure represented by (S4)-(S / B5), (S4) is a block containing 85 to 100% by mass of vinyl aromatic monomer units, and (S / B5) is a tapered block containing vinyl aromatic monomer units and conjugated diene monomer units and containing 5% to less than 20% by mass of conjugated diene monomer units, and the block copolymer D contains 4 to 20% by mass of conjugated diene monomer units. [5] A heat-shrinkable film comprising a layer constituted by the block copolymer composition according to any one of [1] to [4]. [6] A container fitted with the heat-shrinkable film according to [5].

[0009] The block copolymer composition of the present invention has excellent rigidity and impact resistance in molded articles, and can be used for heat-shrinkable films and the like.

[0010] Hereinafter, embodiments of the present invention will be described. Various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an invention independently. Furthermore, in the following embodiments, elements not specified in the claims are optional elements and can be omitted. Any number of "0"s (for example, one or two) may be added to the end of numerical values ​​disclosed in the following description. For example, one or two "0"s may be added after "1.4" to make it "1.40" or "1.400".

[0011] 1. Block Copolymer Composition A block copolymer composition according to one embodiment of the present invention contains a block copolymer comprising vinyl aromatic monomer units and conjugated diene monomer units. A block copolymer having vinyl aromatic monomer units and conjugated diene monomer units can be obtained, for example, by a living anionic polymerization reaction in an organic solvent using an organolithium compound or the like as a polymerization initiator. In living anionic polymerization, almost all of the vinyl aromatic monomer and conjugated diene monomer used in the polymerization reaction can be converted into polymers, and therefore, by changing the amounts and order of addition of these monomers, a block copolymer having any primary structure can be obtained.

[0012] The block copolymer composition contains block copolymers A, B, and C as block copolymers containing vinyl aromatic monomer units and conjugated diene monomer units. The block copolymer composition preferably further contains block copolymer D as a block copolymer containing vinyl aromatic monomer units and conjugated diene monomer units. The block copolymer composition may further contain a block copolymer other than block copolymers A to D that contains vinyl aromatic monomer units and conjugated diene monomer units.

[0013] The block copolymer composition contains 10 to 30% by mass of conjugated diene monomer units, where the total mass of the vinyl aromatic monomer units and the conjugated diene monomer units in the block copolymer composition is taken as 100% by mass. Specific examples of the content of conjugated diene monomer units, where the total mass of the vinyl aromatic monomer units and the conjugated diene monomer units in the block copolymer composition is taken as 100% by mass, are 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, and 30% by mass, and may be within a range between any two of the values ​​exemplified here.

[0014] When the total content of block copolymers containing vinyl aromatic monomer units and conjugated diene monomer units in the block copolymer composition is taken as 100% by mass, the block copolymer composition contains 9 to 39% by mass of block copolymer A, 6 to 26% by mass of block copolymer B, and 35 to 85% by mass of block copolymer C, and preferably contains 15 to 30% by mass of block copolymer A, 10 to 20% by mass of block copolymer B, and 40 to 70% by mass of block copolymer C. Furthermore, when the total content of block copolymers containing vinyl aromatic monomer units and conjugated diene monomer units in the block copolymer composition is taken as 100% by mass, the block copolymer composition may contain 9 to 39% by mass of block copolymer A, 6 to 26% by mass of block copolymer B, 35 to 84% by mass of block copolymer C, and 1 to 30% by mass of block copolymer D, and preferably contains 15 to 30% by mass of block copolymer A, 10 to 20% by mass of block copolymer B, 40 to 70% by mass of block copolymer C, and 5 to 25% by mass of block copolymer D.

[0015] When the total content of the block copolymers containing vinyl aromatic monomer units and conjugated diene monomer units in the block copolymer composition is taken as 100 mass%, the content of block copolymer A is specifically, for example, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, or 39 mass%, and may be within a range between any two of the numerical values ​​exemplified here. When the total content of the block copolymers containing vinyl aromatic monomer units and conjugated diene monomer units in the block copolymer composition is taken as 100 mass%, the content of block copolymer B is specifically, for example, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, or 26 mass%, and may be within a range between any two of the numerical values ​​exemplified here. When the total content of the block copolymers containing vinyl aromatic monomer units and conjugated diene monomer units in the block copolymer composition is taken as 100 mass%, the content of block copolymer C is specifically, for example, 35, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 55, 56, 57, 58, 59, 60, 65, 70, 75, 80, or 85 mass%, and may be within a range between any two of the numerical values ​​exemplified here. When the total content of the block copolymers containing vinyl aromatic monomer units and conjugated diene monomer units in the block copolymer composition is taken as 100 mass%, the content of block copolymer D is specifically, for example, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, or 30 mass%, and may be within a range between any two of the numerical values ​​exemplified here.

[0016] The block copolymer composition can contain, for example, 50 to 100% by mass, and preferably 90 to 100% by mass, of the block copolymer containing vinyl aromatic monomer units and conjugated diene monomer units. The content of the block copolymer containing vinyl aromatic monomer units and conjugated diene monomer units in the block copolymer composition is, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, or 100% by mass, and may be within a range between any two of the values ​​exemplified here. The block copolymer composition can contain, for example, 50 to 100% by mass, and preferably 90 to 100% by mass, of block copolymers A to D in total. The total content of block copolymers A to D in the block copolymer composition is specifically, for example, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 96, 97, 98, 99, or 100 mass%, and may be within a range between any two of the numerical values ​​exemplified here.

[0017] <Block Copolymer A> Block copolymer A has a block structure represented by (S1)-(S / B1). Block copolymer A is a polymer in which the block structure is formed in a linear chain.

[0018] (S1) is a block of a (co)polymer containing a vinyl aromatic monomer unit, and is a block containing 85 to 100 mass% of vinyl aromatic monomer units relative to 100 mass% of the total of the monomer units constituting (S1), preferably a block containing 95 to 100 mass%, and more preferably a block made of a styrene homopolymer.

[0019] (S / B1) is a copolymer block containing vinyl aromatic monomer units and conjugated diene monomer units, and is a tapered block containing 20 to 60 mass% of conjugated diene monomer units relative to 100 mass% of the total monomer units constituting (S / B1), preferably 30 to 50 mass%, and more preferably 35 to 45 mass%. Specific examples of the content of conjugated diene monomer units relative to 100 mass% of the total monomer units constituting (S / B1) include 20, 25, 30, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 50, 55, and 60 mass%, and may be within a range between any two of the values ​​exemplified here.

[0020] Block copolymer A contains 5 to 15% by mass, preferably 7 to 13% by mass, of conjugated diene monomer units relative to 100% by mass of block copolymer A. The content of conjugated diene monomer units relative to 100% by mass of block copolymer A is, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15% by mass, and may be within a range between any two of the values ​​exemplified here. Block copolymer A may also contain 85 to 95% by mass of vinyl aromatic monomer units relative to 100% by mass of block copolymer A. Block copolymer A may contain monomer units (other monomer units) other than vinyl aromatic monomer units and conjugated diene monomer units, and the content of the other monomer units relative to 100% by mass of block copolymer A is, for example, 0 to 2% by mass, preferably 0 to 1% by mass, and more preferably 0 to 0.1% by mass. In one example, block copolymer A is (substantially) free of other monomer units.

[0021] It should be noted that the block copolymer A does not have a block structure represented by (S3)-(S / B3)-(S / B4) described below.

[0022] <Block Copolymer B> Block copolymer B has a block structure represented by (S2)-(S / B2). (S2) is a block of a (co)polymer containing a vinyl aromatic monomer unit, and is a block containing 85 to 100 mass% of the vinyl aromatic monomer unit relative to 100 mass% of the total monomer units constituting (S2), preferably 95 to 100 mass%, and more preferably a block consisting of a styrene homopolymer.

[0023] (S / B2) is a copolymer block containing vinyl aromatic monomer units and conjugated diene monomer units, and is a tapered block containing 20 to 60 mass% of conjugated diene monomer units relative to 100 mass% of the total monomer units constituting (S / B2), preferably 30 to 50 mass%, and more preferably 35 to 45 mass%. Specific examples of the content of conjugated diene monomer units relative to 100 mass% of the total monomer units constituting (S / B2) include 20, 25, 30, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 50, 55, and 60 mass%, and may be within a range between any two of the values ​​exemplified here.

[0024] Block copolymer B contains more than 15% by mass and 50% by mass or less of conjugated diene monomer units, preferably 20 to 40% by mass, based on 100% by mass of block copolymer B. The content of conjugated diene monomer units based on 100% by mass of block copolymer B is, for example, 16, 20, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 40, 45, or 50% by mass, and may be within a range between any two of the values ​​exemplified here. Furthermore, block copolymer B may contain 50% by mass or more and less than 85% by mass of vinyl aromatic monomer units based on 100% by mass of block copolymer B. Block copolymer B may contain monomer units (other monomer units) other than vinyl aromatic monomer units and conjugated diene monomer units, and the content of the other monomer units relative to 100% by mass of block copolymer B is, for example, 0 to 2% by mass, preferably 0 to 1% by mass, and more preferably 0 to 0.1% by mass. In one example, block copolymer B is (substantially) free of other monomer units.

[0025] It should be noted that the block copolymer B does not have a block structure represented by (S3)-(S / B3)-(S / B4) described below.

[0026] <Block Copolymer C> Block copolymer C has a block structure represented by (S3)-(S / B3)-(S / B4). (S3) is a block of a (co)polymer containing a vinyl aromatic monomer unit, and is a block containing 85 to 100 mass% of the vinyl aromatic monomer unit relative to 100 mass% of the total monomer units constituting (S3), preferably 95 to 100 mass%, and more preferably a block consisting of a styrene homopolymer.

[0027] (S / B3) and (S / B4) are each a copolymer block containing vinyl aromatic monomer units and conjugated diene monomer units, and are tapered blocks containing 8 to 36 mass% of conjugated diene monomer units, preferably 10 to 30 mass%, relative to 100 mass% of the total monomer units constituting (S / B3) or (S / B4). The compositions of (S / B3) and (S / B4) may be different from each other. (S / B3) is a tapered block containing conjugated diene monomer units, more preferably 8 to 20 mass%, even more preferably 9 to 15 mass%, relative to 100 mass% of the total monomer units constituting (S / B3). (S / B4) is a tapered block containing conjugated diene monomer units in an amount of more than 20% by mass and not more than 36% by mass, and even more preferably 25 to 35% by mass, relative to 100% by mass of the total monomer units constituting (S / B4). Specific examples of the content of conjugated diene monomer units in each block relative to 100% by mass of the total monomer units constituting (S / B3) or (S / B4) are 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, and 36% by mass, and may be within a range between any two of the values ​​exemplified here.

[0028] Block copolymer C contains 7 to 32% by mass, preferably 15 to 25% by mass, of conjugated diene monomer units relative to 100% by mass of block copolymer C. The content of conjugated diene monomer units relative to 100% by mass of block copolymer C is, for example, 7, 10, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 30, or 32% by mass, and may be within a range between any two of the values ​​exemplified here. Furthermore, block copolymer C may contain 68 to 93% by mass of vinyl aromatic monomer units relative to 100% by mass of block copolymer C. Block copolymer C may contain monomer units (other monomer units) other than vinyl aromatic monomer units and conjugated diene monomer units, and the content of the other monomer units relative to 100% by mass of block copolymer C is, for example, 0 to 2% by mass, preferably 0 to 1% by mass, and more preferably 0 to 0.1% by mass. In one example, block copolymer C is (substantially) free of other monomer units.

[0029] The mass ratio of (S / B3) to (S / B4) [(S / B4) / (S / B3)] is 0.6 to 5.5, preferably 0.7 to 1.5. Specific examples of the mass ratio are 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, and 5.5, and may be within a range between any two of the values ​​exemplified here.

[0030] <Block Copolymer D> Block copolymer D has a block structure represented by (S4)-(S / B5). (S4) is a block of a (co)polymer containing a vinyl aromatic monomer unit, and is a block containing 85 to 100 mass% of the vinyl aromatic monomer unit relative to 100 mass% of the total monomer units constituting (S4), preferably 95 to 100 mass%, and more preferably a block consisting of a styrene homopolymer.

[0031] (S / B5) is a copolymer block containing vinyl aromatic monomer units and conjugated diene monomer units, and is a tapered block containing 5% by mass or more but less than 20% by mass of conjugated diene monomer units relative to 100% by mass of the total monomer units constituting (S / B5), preferably 7 to 15% by mass. Specific examples of the content of conjugated diene monomer units relative to 100% by mass of the total monomer units constituting (S / B5) include 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, and 19% by mass, and may be within a range between any two of the values ​​exemplified here.

[0032] Block copolymer D contains 4 to 20% by mass, preferably 5 to 15% by mass, of conjugated diene monomer units relative to 100% by mass of block copolymer D. The content of conjugated diene monomer units relative to 100% by mass of block copolymer D is, for example, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20% by mass, and may be within a range between any two of the values ​​exemplified here. Furthermore, block copolymer D may contain 80 to 96% by mass of vinyl aromatic monomer units relative to 100% by mass of block copolymer D. Block copolymer D may contain monomer units (other monomer units) other than vinyl aromatic monomer units and conjugated diene monomer units, and the content of the other monomer units relative to 100% by mass of block copolymer D is, for example, 0 to 2% by mass, preferably 0 to 1% by mass, and more preferably 0 to 0.1% by mass. In one example, block copolymer D is (substantially) free of other monomer units.

[0033] It should be noted that the block copolymer D does not have the block structure represented by the above-mentioned (S3)-(S / B3)-(S / B4).

[0034] In this specification, the term "tapered block" refers to a block in which the microscopic composition of vinyl aromatic monomer units and conjugated diene monomer units changes continuously in one direction. For example, when both vinyl aromatic monomer and conjugated diene monomer are added at once, the highly reactive conjugated diene monomer is preferentially polymerized, resulting in a polymer chain with a high proportion of conjugated diene monomer units at the beginning of block formation. However, as the polymerization progresses, the concentration of the conjugated diene monomer decreases and the concentration of the vinyl aromatic monomer increases, resulting in a polymer chain with a low proportion of conjugated diene monomer units at the end of block formation. Note that a block in a state different from a "tapered block" is known as a "random block," which refers to a block in which the microscopic composition of vinyl aromatic monomer units and conjugated diene monomer units is almost constant within the block.

[0035] <Each Monomer Unit> The vinyl aromatic monomer unit is a structural unit derived from the vinyl aromatic monomer used in the polymerization of each block copolymer. The vinyl aromatic monomer is a compound in which a vinyl group is bonded to an aromatic ring. Examples of the vinyl aromatic monomer include vinyl aromatic monomers such as styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, α-methylstyrene, vinylnaphthalene, and vinylanthracene. The vinyl aromatic monomer preferably includes styrene, and more preferably styrene. These monomers may be used alone or in combination of two or more. The vinyl aromatic monomers used in each of the block copolymers A to D (and thus the vinyl aromatic monomer units contained in the block copolymers) may be the same or different, but are preferably the same.

[0036] The conjugated diene monomer units are units derived from the conjugated diene monomers used in the polymerization of the block copolymers. The conjugated diene monomers are compounds having a conjugated chemical structure represented by C=C-C=C. Examples of conjugated diene monomers include 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. The conjugated diene monomer preferably includes 1,3-butadiene, and more preferably 1,3-butadiene. These monomers may be used alone or in combination of two or more. The conjugated diene monomers used in each of the block copolymers A to D (and thus the conjugated diene monomer units contained in the block copolymers) may be the same or different from each other, but are preferably the same.

[0037] The content of conjugated diene monomer units can be calculated from the amounts of vinyl aromatic monomer units and conjugated diene monomers charged when producing each block copolymer, or it may be calculated using a known halogen addition method. A typical example of the halogen addition method involves dissolving the sample in a solvent capable of completely dissolving it, adding an excess amount of iodine monochloride / acetic acid solution to allow for sufficient reaction, adding potassium iodide solution, and titrating with a sodium thiosulfate / ethanol solution. The content of conjugated diene monomer units is calculated from the amount of double bonds obtained by the above-mentioned method. The content of vinyl aromatic monomer units is calculated by subtracting the content of conjugated diene monomer units from the total content of the sample.

[0038] <Molecular Weight> The block copolymer resin composition preferably has, in a molecular weight distribution measured by gel permeation chromatography (GPC), at least one molecular weight peak in a weight average molecular weight range of 140,000 to 220,000 and at least one molecular weight peak in a weight average molecular weight range of 50,000 to 90,000, in terms of polystyrene equivalent molecular weight. The at least one molecular weight peak in the weight average molecular weight range of 140,000 to 220,000 is preferably a peak derived from a block copolymer comprising vinyl aromatic monomer units and conjugated diene monomer units. The at least one molecular weight peak in the weight average molecular weight range of 50,000 to 90,000 is preferably a peak derived from a block copolymer comprising vinyl aromatic monomer units and conjugated diene monomer units.

[0039] In one embodiment, the block copolymer resin composition has, in a molecular weight distribution measured by GPC, at least two molecular weight peaks in a weight average molecular weight range of 140,000 to 220,000 and at least one molecular weight peak in a weight average molecular weight range of 50,000 to 90,000, in terms of polystyrene. One of the molecular weight peaks in the weight average molecular weight range of 140,000 to 220,000 is a peak derived from block copolymer A. One of the molecular weight peaks in the weight average molecular weight range of 140,000 to 220,000 is a peak derived from block copolymer C. One of the molecular weight peaks in the weight average molecular weight range of 50,000 to 90,000 is a peak derived from block copolymer B.

[0040] In one embodiment, the block copolymer resin composition has, in a molecular weight distribution measured by GPC, at least two molecular weight peaks in a weight average molecular weight range of 50,000 to 90,000 and at least two molecular weight peaks in a weight average molecular weight range of 50,000 to 90,000, in terms of polystyrene. One of the molecular weight peaks in the weight average molecular weight range of 140,000 to 220,000 is a peak derived from block copolymer A. One of the molecular weight peaks in the weight average molecular weight range of 140,000 to 220,000 is a peak derived from block copolymer C. One of the molecular weight peaks in the weight average molecular weight range of 50,000 to 90,000 is a peak derived from block copolymer B. One of the molecular weight peaks in the weight average molecular weight range of 50,000 to 90,000 is a peak derived from block copolymer D.

[0041] The weight average molecular weight of block copolymer A (value calculated as polystyrene by GPC measurement) is, for example, 130,000 to 250,000, preferably 140,000 to 200,000, and more preferably 150,000 or more and less than 180,000. Specific examples of the weight average molecular weight of block copolymer A are 130,000, 140,000, 150,000, 160,000, 170,000, 175,000, 180,000, 190,000, 200,000, 210,000, 220,000, 230,000, 240,000, and 250,000, and may be within a range between any two of the values ​​exemplified here.

[0042] The weight average molecular weight of block copolymer B (a polystyrene-equivalent value measured by GPC) is, for example, 40,000 or more and less than 130,000, preferably 50,000 to 100,000. Specific examples of the weight average molecular weight of block copolymer B include 40,000, 50,000, 60,000, 70,000, 80,000, 90,000, 100,000, 110,000, and 120,000, and may be within a range between any two of the values ​​exemplified here.

[0043] The weight average molecular weight of the block copolymer C (value calculated as polystyrene by GPC measurement) is, for example, 140,000 to 300,000, preferably 160,000 to 250,000, and more preferably 180,000 to 220,000. Specific examples of the weight average molecular weight of the block copolymer C include 140,000, 150,000, 160,000, 170,000, 180,000, 190,000, 200,000, 210,000, 220,000, 230,000, 240,000, 250,000, 260,000, 270,000, 280,000, 290,000, and 300,000, and may be within a range between any two of the values ​​exemplified here.

[0044] The weight average molecular weight of block copolymer D (a polystyrene-equivalent value measured by GPC) is, for example, 50,000 or more and less than 130,000, preferably 60,000 to 120,000. Specific examples of the weight average molecular weight of block copolymer D are 50,000, 60,000, 70,000, 80,000, 90,000, 100,000, 110,000, and 120,000, and may be within a range between any two of the values ​​exemplified here.

[0045] <Additives, etc.> The block copolymer resin composition may contain a polymer other than the block copolymer containing vinyl aromatic monomer units and conjugated diene monomer units, and may also contain other additives as necessary.

[0046] Examples of other additives include various stabilizers, lubricants, processing aids, antistatic agents, antifogging agents, light resistance improvers, softeners, plasticizers, pigments, etc. Each additive may be added to a solution of the block copolymer, or may be blended with the recovered copolymer and melt-mixed. The content of these additives in the block copolymer resin composition is, for example, 0 to 10% by mass, specifically, for example, 0, 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10% by mass, and may be within a range between any two of the values ​​exemplified here.

[0047] Examples of stabilizers include phenolic antioxidants such as 2-tert-butyl-6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 2,6-di-tert-butyl-4-methylphenol, and phosphorus-based antioxidants such as trisnonylphenyl phosphite. Examples of antiblocking agents, antistatic agents, and lubricants include fatty acid amides, ethylene bisstearamide, sorbitan monostearate, saturated fatty acid esters of fatty alcohols, and pentaerythritol fatty acid esters.

[0048] <Characteristics of Block Copolymer Composition> (Flexural Modulus) The flexural modulus of the block copolymer composition, measured according to ISO 178 using an A-type test piece obtained by molding the block copolymer composition in accordance with ISO 3167, is preferably 1300 MPa or more, more preferably 1400 MPa or more, and even more preferably 1500 MPa or more. By satisfying this range, excellent rigidity is achieved. The upper limit of the flexural modulus is, for example, 2500 MPa or less, and from the viewpoint of impact resistance, 2000 MPa or less. Specific examples of the flexural modulus are 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, and 2500 MPa, and may be within a range between any two of the values ​​exemplified here.

[0049] <Method for Producing Block Copolymer Composition> (Method for Producing Block Copolymer) The method for producing block copolymers A to D is not particularly limited, and for example, they can be obtained by a living anionic polymerization reaction of a monomer raw material containing a vinyl aromatic monomer and a conjugated diene monomer in an organic solvent using an organolithium compound as a polymerization initiator.

[0050] Examples of organic solvents include aliphatic hydrocarbons such as butane, pentane, hexane, isopentane, heptane, octane, and isooctane, alicyclic hydrocarbons such as cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, and ethylcyclohexane, and aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene. Cyclohexane is a particularly preferred organic solvent.

[0051] An organolithium compound is a compound having one or more lithium atoms bonded to the molecule. Examples of the organolithium compound include monofunctional organolithium compounds such as ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, and tert-butyllithium, and polyfunctional organolithium compounds such as hexamethylenedilithium, butadienyldilithium, and isoprenyldilithium. A particularly preferred organolithium compound is n-butyllithium.

[0052] In living anionic polymerization, block copolymers with any primary structure can be obtained by changing the amount and method of addition of the monomer raw materials. For example, the molecular weight can be adjusted by changing the ratio of the organolithium compound to the monomer raw materials. Furthermore, the ratio of vinyl aromatic monomer units to conjugated diene monomer units in each block chain and the change in the ratio (e.g., tapered blocks can be obtained by adding both monomers at once) can be controlled by changing the addition order or the addition method, such as fractional addition.

[0053] The block copolymer thus obtained is inactivated by adding a polymerization terminator such as water, alcohol, or carbon dioxide in an amount sufficient to inactivate the active terminals. The copolymer can be recovered from the resulting block copolymer solution (polymerization solution) by any method, including (A) precipitation using a poor solvent such as methanol, (B) precipitation by evaporating the solvent using a heated roll or the like (drum dryer method), (C) concentrating the solution using a concentrator and then removing the solvent using a vented extruder (devolatilization extrusion method), or (D) dispersing the solution in water, blowing in steam to heat and remove the solvent, and recovering the copolymer (steam stripping method). Devolatilization extrusion method is particularly preferred.

[0054] The block copolymer composition can be obtained by mixing block copolymers containing three or more types of vinyl aromatic monomer units and conjugated diene monomer units obtained by the above-mentioned production method or the like. Known mixing methods can be used. For example, pellets or powder of the block copolymers can be dry-blended using a Henschel mixer, ribbon blender, super mixer, V blender, or the like, or can be melted and pelletized in an extruder. In one embodiment, melt mixing is preferred. Alternatively, a method can be used in which polymer solutions (polymerization solutions) are mixed together and then the solvent is removed. If necessary, the above-mentioned other additives can be added and mixed.

[0055] 2. Films and Containers A film according to one embodiment of the present invention is a molded article obtained by molding the block copolymer composition. The film is, for example, a heat-shrinkable film containing the block copolymer composition. The heat-shrinkable film can be obtained by uniaxially, biaxially, or multiaxially stretching an unstretched film (hereinafter, the unstretched film will be referred to as a sheet for the sake of distinction) extruded from the block copolymer composition (e.g., pellets thereof) using a known method, such as a T-die method or a tubular method. Biaxial stretching by a T-die method is particularly preferred. During extrusion molding, if necessary, an antiblocking agent such as high-impact polystyrene can be added to the block copolymer composition (e.g., pellets thereof) in an amount of, for example, 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass, per 100 parts by mass of the block copolymer composition.

[0056] A heat-shrinkable film according to one embodiment of the present invention includes a layer formed from the block copolymer composition. The heat-shrinkable film may include only a layer formed from the block copolymer composition (single layer or multiple layers), or may have another resin layer laminated on at least one side of the layer formed from the block copolymer composition. To obtain a multilayer heat-shrinkable film, another resin layer may be laminated on a stretched film formed from the block copolymer composition; another resin layer may be laminated on a sheet obtained by forming a film from the block copolymer composition and then stretched; or a multilayer sheet formed by laminating the block copolymer composition and another resin by multilayer extrusion molding may be stretched. Examples of resins used for the other resin layer include styrene-based resins (e.g., homopolymers of styrene-based monomers).

[0057] Examples of uniaxial stretching include a method of stretching an extruded sheet in a direction perpendicular to the extrusion direction (TD) using a tenter, and a method of stretching an extruded tubular sheet in the circumferential direction.

[0058] Examples of biaxial stretching include a method in which an extruded sheet is stretched in the extrusion direction (MD) with a roll and then stretched in a direction perpendicular to the extrusion direction (TD) with a tenter or the like, and a method in which an extruded tubular sheet is stretched in the extrusion direction and the circumferential direction simultaneously or separately.

[0059] The stretching temperature is preferably, for example, 60 to 120°C. By setting the temperature to 60°C or higher, the sheet or film is less likely to break during stretching, and by setting the temperature to 120°C or lower, the shrinkage properties and thickness precision of the obtained film are likely to be good. The stretching ratio is not particularly limited, but is preferably, for example, 1.5 to 8 times. By setting the temperature to 1.5 times or higher, the heat shrinkability is likely to be good, and by setting the temperature to 8 times or lower, the sheet or film is less likely to break during stretching.

[0060] The thickness of the film is, for example, 10 to 300 μm.

[0061] <Characteristics of Heat-Shrinkable Film> (Impact Strength) The impact strength of the heat-shrinkable film is preferably 40 kJ / m or more, more preferably 45 kJ / m or more, and even more preferably 50 kJ / m or more. By satisfying this range, the film has excellent impact resistance. The upper limit of the impact strength is, for example, 70 kJ / m or less, and from the viewpoint of rigidity, 60 kJ / m or less. Specific examples of the impact strength are 40, 45, 50, 55, 60, 65, and 70 kJ / m, and may be within a range between any two of the values ​​exemplified here. The impact strength of the film is measured in accordance with ASTM D3420 by the following method. (1) A sample piece having an MD of 100 mm and a TD of 100 mm is cut out from the heat-shrinkable film. (2) Using an impact tester manufactured by Tester Sangyo Co., Ltd., the cut sample piece is clamped on the measurement table, and the film is punched out at a torque of 3 N m, a pendulum tip diameter of 25 mm, and a measurement temperature of 23°C. The impact strength displayed on the device is read and divided by the film thickness to calculate the impact strength (kJ / m) per unit thickness.

[0062] (Heat Shrinkage Ratio) The heat shrinkage ratio of the heat shrinkable film at 70°C (T=70) is preferably 5 to 25%, more preferably 7 to 15%. The heat shrinkage ratio of the heat shrinkable film at 100°C (T=100) is preferably 65 to 80%, more preferably 70 to 75%. Each heat shrinkage ratio was measured by the following method. (1) A test piece having an MD of 100 mm and a TD of 100 mm was cut out from the heat shrinkable film. (2) This test piece was completely immersed in warm water at T°C for 10 seconds, then removed, thoroughly wiped to remove moisture, and the TD length L (mm) was measured. (3) The heat shrinkage ratio was calculated using the following formula: Heat shrinkage ratio (%) = {(100 - L) / 100} x 100

[0063] (Compression Strength) The compression strength of the heat-shrinkable film, measured by a method in accordance with JIS P8126, is preferably at least 6 N, and more preferably at least 8 N. The larger this value, the less likely the film is to buckle when attached to a container, and the better the attachment property.

[0064] <Uses> The heat-shrinkable film can be used as a heat-shrinkable label, a heat-shrinkable cap seal, etc. In addition, it can be used as a packaging film, etc.

[0065] A container according to one embodiment of the present invention is a container to which the heat-shrinkable film is attached, such as a PET bottle to which the heat-shrinkable film is attached as a label, a sticker, or the like.

[0066] The present invention will be described in more detail below with reference to examples, but these examples are merely illustrative and are not intended to limit the scope of the present invention.

[0067] [Synthesis of Block Copolymers] Block copolymers P1 to P20 were produced by the following procedures under the conditions shown in Tables 1 and 2. Note that when there is no step corresponding to (5) in the synthesis of each block copolymer, this is indicated below as "-", but step (6) was performed following step (4).

[0068] <Block Copolymer P1> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 1,400 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 150 kg of styrene was added, and the temperature was raised to 40°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 60°C or below, and 30 kg of styrene and 20 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (5)-(6) After the styrene and 1,3-butadiene were completely consumed, 220 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P1 as pellets.

[0069] <Block Copolymer P2> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 4100 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 40 kg of styrene was added, and the temperature was raised to 65°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 35°C or below, and 100 kg of styrene and 60 kg of 1,3-butadiene were simultaneously added in one lump to polymerize. (5)-(6) After the styrene and 1,3-butadiene were completely consumed, 660 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P2.

[0070] <Block Copolymer P3> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 1,300 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 26 kg of styrene was added, and the temperature was raised to 80°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 50°C or below, and 67 kg of styrene and 20 kg of 1,3-butadiene were simultaneously added in one lump sum to polymerize. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to 50°C or below, and 67 kg of styrene and 20 kg of 1,3-butadiene were simultaneously added in one lump sum to polymerize. (6) After the styrene and 1,3-butadiene were completely consumed, 210 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P3.

[0071] <Block Copolymer P4> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 3,000 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 60 kg of styrene was added, and the temperature was raised to 65°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 40°C or below, and 124 kg of styrene and 16 kg of 1,3-butadiene were simultaneously added in one lump to polymerize. (5)-(6) After the styrene and 1,3-butadiene were completely consumed, 480 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P4.

[0072] <Block Copolymer P5> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 1,400 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 150 kg of styrene was added, and the temperature was raised to 40°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 60°C or below, and 40 kg of styrene and 10 kg of 1,3-butadiene were simultaneously added in one lump to polymerize. (5)-(6) After the styrene and 1,3-butadiene were completely consumed, 220 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P5.

[0073] <Block Copolymer P6> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 1,500 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 150 kg of styrene was added, and the temperature was raised to 40°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 60°C or below, and 20 kg of styrene and 30 kg of 1,3-butadiene were simultaneously added in one lump to polymerize. (5)-(6) After the styrene and 1,3-butadiene were completely consumed, 230 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P6.

[0074] <Block Copolymer P7> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 3,600 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 40 kg of styrene was added, and the temperature was raised to 65°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 35°C or below, and 128 kg of styrene and 32 kg of 1,3-butadiene were simultaneously added in one lump to polymerize. (5)-(6) After the styrene and 1,3-butadiene were completely consumed, 570 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P7.

[0075] <Block Copolymer P8> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 4,500 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 40 kg of styrene was added, and the temperature was raised to 65°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 30°C or below, and 64 kg of styrene and 96 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (5)-(6) After the styrene and 1,3-butadiene were completely consumed, 710 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P8.

[0076] <Block Copolymer P9> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 1,200 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 26 kg of styrene was added, and the temperature was raised to 80°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 50°C or below, and 80 kg of styrene and 7 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to 50°C or below, and 80 kg of styrene and 7 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 190 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P9.

[0077] <Block Copolymer P10> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 1,400 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 26 kg of styrene was added, and the temperature was raised to 80°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 50°C or below, and 56 kg of styrene and 31 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to 50°C or below, and 56 kg of styrene and 31 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 230 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P10.

[0078] <Block Copolymer P11> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 1,300 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 26 kg of styrene was added, and the temperature was raised to 80°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 50°C or below, and 22 kg of styrene and 7 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to 35°C or below, and 112 kg of styrene and 33 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 210 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P11.

[0079] <Block Copolymer P12> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 1,300 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 26 kg of styrene was added, and the temperature was raised to 80°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 50°C or below, and 78 kg of styrene and 24 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to 60°C or below, and 56 kg of styrene and 16 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 210 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P12.

[0080] <Block Copolymer P13> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 1,400 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 150 kg of styrene was added, and the temperature was raised to 40°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 60°C or below, and 44 kg of styrene and 6 kg of 1,3-butadiene were simultaneously added in one lump to polymerize. (5)-(6) After the styrene and 1,3-butadiene were completely consumed, 220 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P13.

[0081] <Block Copolymer P14> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 1,400 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 150 kg of styrene was added, and the temperature was raised to 40°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 60°C or below, and 10 kg of styrene and 40 kg of 1,3-butadiene were simultaneously added in one lump to polymerize. (5)-(6) After the styrene and 1,3-butadiene were completely consumed, 240 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P14.

[0082] <Block Copolymer P15> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 3,300 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 40 kg of styrene was added, and the temperature was raised to 80°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 35°C or below, and 144 kg of styrene and 16 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (5)-(6) After the styrene and 1,3-butadiene were completely consumed, 520 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P15.

[0083] <Block Copolymer P16> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 4,700 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 40 kg of styrene was added, and the temperature was raised to 80°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 25°C or below, and 48 kg of styrene and 112 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (5)-(6) After the styrene and 1,3-butadiene were completely consumed, 730 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P16.

[0084] <Block Copolymer P17> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 1,200 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 26 kg of styrene was added, and the temperature was raised to 80°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 40°C or below, and 82 kg of styrene and 5 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to 50°C or below, and 82 kg of styrene and 5 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 190 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P17.

[0085] <Block Copolymer P18> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 1,500 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 26 kg of styrene was added, and the temperature was raised to 80°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 40°C or below, and 46 kg of styrene and 35 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to 50°C or below, and 46 kg of styrene and 35 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 230 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P18.

[0086] <Block Copolymer P19> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 1,300 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 26 kg of styrene was added, and the temperature was raised to 80°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 40°C or below, and 19 kg of styrene and 6 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to 35°C or below, and 115 kg of styrene and 34 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 210 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P19.

[0087] <Block Copolymer P20> (1) 467 kg of cyclohexane was charged into a reaction vessel. (2) While stirring at an internal temperature of 30°C, 1,300 mL of n-butyllithium (10% by mass solution in cyclohexane) was added. (3) 26 kg of styrene was added, and the temperature was raised to 80°C to polymerize. (4) After the styrene was completely consumed, the internal temperature was cooled to 40°C or below, and 88 kg of styrene and 28 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to 70°C or below, and 46 kg of styrene and 12 kg of 1,3-butadiene were simultaneously added in one lump and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 210 g of water was added to inactivate the mixture, thereby obtaining a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a devolatilizing extruder to obtain block copolymer P20.

[0088] The resulting block copolymer was subjected to the following measurements and analyses.

[0089] <Weight-average molecular weight> The weight-average molecular weight of the block copolymer was measured using the following GPC measurement device and conditions, and calculated as the polystyrene-equivalent molecular weight based on a calibration curve using standard polystyrene. Device name: HLC-8220GPC (manufactured by Tosoh Corporation) Column: Four Shodex GPCKF-404 (manufactured by Showa Denko K.K.) connected in series Temperature: 40°C Detection: Differential refractive index Solvent: Tetrahydrofuran Concentration: 2% by mass Calibration curve: Prepared using standard polystyrene (manufactured by VARIAN)

[0090] <Monomer Unit Content / Block Mass> The contents of vinyl aromatic monomer units (styrene units) and conjugated diene monomer units (butadiene units) contained in the block copolymer and each block were calculated from the amounts of vinyl aromatic monomer (styrene) and conjugated diene monomer (1,3-butadiene) charged when producing the block copolymer. The masses of each of the (S / B3) and (S / B4) blocks were also calculated from the amounts of vinyl aromatic monomer units and conjugated diene monomer charged in each polymerization stage.

[0091]

[0092]

[0093] [Preparation of Block Copolymer Compositions] Block copolymer compositions RA1 to RA12 and RB1 to RB11 of Examples and Comparative Examples were obtained by melt-mixing each of the block copolymers P1 to P20 obtained by the above synthesis in an extruder based on the contents shown in Tables 3 and 4. The content (mass %) of each block copolymer represents the content of each block copolymer when the total content of block copolymers P1 to P20 contained in the block copolymer composition is taken as 100 mass %.

[0094] [Measurements and Analysis] The block copolymer compositions of the Examples and Comparative Examples were subjected to the following measurements and analyses.

[0095] <Flexural modulus> Using pellets of the block copolymer composition, an ISO dumbbell test piece having a thickness of 4 mm was prepared using an injection molding machine. Using this dumbbell test piece, measurement was performed in accordance with ISO 178 under conditions of a bending speed of 2 mm / min, a relative humidity of 50%, and an ambient temperature of 23°C.

[0096]

[0097]

[0098] Heat-shrinkable films were prepared by adding (dry blending) 1.3 parts by mass of high-impact polystyrene "E640N" (manufactured by Toyo Styrene Co., Ltd.) as an anti-blocking agent to 100 parts by mass of each of the compositions RA1 to RA12 and RB1 to RB11. The physical properties of the heat-shrinkable films are shown in Tables 5 and 6.

[0099] (1) Extrusion of Sheet Before Stretching Using an extruder equipped with a T-die with a lip width of 300 μm capable of extruding sheets, the block copolymer resin composition of each Example and Comparative Example, dry-blended with high-impact polystyrene, was melted and extruded into a sheet. The extruder that melted the resin and fed it to the T-die was a 65 mmφ short-screw extruder, and the set temperature was 210°C. The set temperature of the T-die was also 210°C. The thickness of the obtained sheet was 0.30 mm.

[0100] (2) Stretching of Pre-Stretched Sheet The obtained pre-stretched sheet was stretched by 1.1 times in the MD direction at 90°C in a longitudinal stretching machine having two rolls with different rotation speeds, and then stretched by 4.5 times in the TD direction at 90°C in a tenter-type transverse stretching machine, to finally obtain a 50 µm-thick heat-shrinkable film using the block copolymer resin composition of each of the Examples and Comparative Examples.

[0101] <Heat Shrinkage> The heat shrinkage of the film was measured by the following method under the conditions of T = 70°C and 100°C. (1) A test piece having an MD width of 100 mm and a TD width of 100 mm was cut out from the heat-shrinkable film obtained by stretching. (2) This test piece was completely immersed in warm water at T°C for 10 seconds, then removed, thoroughly wiped to remove moisture, and the length L (mm) in the TD direction was measured. (3) The heat shrinkage was calculated using the following formula: Heat shrinkage (%) = {(100 - L) / 100} x 100

[0102] <Compression Strength> The compression strength of the film was measured according to JIS P8126. The heat shrinkage film was cut into strips of 12.7 mm in MD and 150 mm in TD, and the strips were set in a cylindrical shape on a pre-prepared support. The support was then placed on the stand of a tensile tester (RTG-1210, manufactured by A&D Co., Ltd.) and measurement was performed. Measurement was performed only on the compression strength in the MD direction.

[0103] <Impact Strength> The impact strength of the heat-shrinkable film obtained by stretching was measured in accordance with ASTM D3420 by the following method. (1) A sample piece measuring 100 mm in MD and 100 mm in TD was cut out from the heat-shrinkable film. (2) Using an impact tester manufactured by Tester Sangyo Co., Ltd., the cut-out sample piece was clamped between the measurement table and the film was punched out at a torque of 3 N m, a pendulum tip diameter of 25 mm, and a measurement temperature of 23°C. The impact strength displayed on the device was read and divided by the film thickness to calculate the impact strength (kJ / m) per unit thickness.

[0104]

[0105]

Claims

1. A block copolymer composition containing a block copolymer comprising vinyl aromatic monomer units and conjugated diene monomer units, wherein when the total mass of the vinyl aromatic monomer units and the conjugated diene monomer units in the block copolymer composition is 100% by mass, the conjugated diene monomer units are contained in an amount of 10 to 30% by mass; when the total content of the block copolymer containing the vinyl aromatic monomer units and the conjugated diene monomer units in the block copolymer composition is 100% by mass, the block copolymer A is contained in an amount of 9 to 39% by mass, the block copolymer B is contained in an amount of 6 to 26% by mass, and the block copolymer C is contained in an amount of 35 to 85% by mass; the block copolymer A has a block structure represented by (S1)-(S / B1), (S1) is a block containing 85 to 100% by mass of vinyl aromatic monomer units, (S / B1) is a tapered block containing vinyl aromatic monomer units and conjugated diene monomer units and containing 20 to 60% by mass of conjugated diene monomer units, the block copolymer A contains 5 to 15% by mass of conjugated diene monomer units; the block copolymer B has a block structure represented by (S2)-(S / B2), (S2) is a block containing 85 to 100% by mass of vinyl aromatic monomer units, (S / B2) is a tapered block containing vinyl aromatic monomer units and conjugated diene monomer units and containing 20 to 60% by mass of conjugated diene monomer units, the block copolymer B contains more than 15% by mass and 50% by mass or less of conjugated diene monomer units; the block copolymer C has a block structure represented by (S3)-(S / B3)-(S / B4), (S3) is a block containing 85 to 100% by mass of vinyl aromatic monomer units, (S / B3) and (S / B4) are each a tapered block containing vinyl aromatic monomer units and conjugated diene monomer units and containing 8 to 36% by mass of conjugated diene monomer units, the block copolymer C contains 7 to 32% by mass of conjugated diene monomer units, and the mass ratio of (S / B3) to (S / B4) is (S / B4) / (S / B3)=0.6 to 5.5, the block copolymer composition.

2. The block copolymer resin composition has at least one molecular weight peak in the range of a polystyrene-equivalent molecular weight of 140,000 to 220,000 and at least one molecular weight peak in the range of a polystyrene-equivalent molecular weight of 50,000 to 90,000 in the molecular weight distribution measured by GPC. The block copolymer resin composition according to claim 1.

3. Using a type A test piece conforming to ISO 3167, the flexural modulus measured according to ISO 178 is 1300 MPa or more. The block copolymer composition according to claim 1.

4. Further containing block copolymer D, the block copolymer D has a block structure represented by (S4)-(S / B5), (S4) is a block containing 85 to 100% by mass of vinyl aromatic monomer units, (S / B5) is a tapered block containing vinyl aromatic monomer units and conjugated diene monomer units, and containing 5% by mass or more and less than 20% by mass of conjugated diene monomer units. The block copolymer D contains 4 to 20% by mass of conjugated diene monomer units. The block copolymer composition according to claim 1.

5. A heat-shrinkable film comprising a layer composed of the block copolymer composition according to any one of claims 1 to 4.

6. A container with the heat-shrinkable film according to claim 5 attached.

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