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

Technical Field

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

[0002] A heat-shrinkable film using a block copolymer obtained by polymerizing a vinyl aromatic compound and a conjugated diene compound is excellent in heat shrinkability and finish after shrinkage, and can accommodate various shapes and mounting methods of articles to be packaged. Therefore, it is widely used for shrink packaging such as labels for PET bottle beverages (Patent Document 1). Prior Art Documents Patent Documents

[0003] Patent Document 1 Japanese Unexamined Patent Publication No. 11-158241

[0004] In recent years, along with the complication of the shape of articles to be packaged, there are demands for high rigidity of the heat-shrinkable film that prevents the film from buckling during mounting, and high impact resistance that prevents the label from breaking when the packaged article is dropped after the label is mounted. Summary of the Invention Problems to be Solved by the Invention

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

[0006] The present invention has been made in view of the above circumstances, and provides a block copolymer composition capable of producing a heat-shrinkable film excellent in rigidity and impact resistance. Means for Solving the Problems

[0007] As a result of diligent research to solve the above problems, the inventors of the present invention have found that the above problems can be solved by including several types of block copolymers containing vinyl aromatic monomer units and conjugated diene monomer units in a specific formulation, and have completed the present invention.

[0008] The present invention provides the following: [1] A block copolymer composition comprising a block copolymer containing vinyl aromatic monomer units and conjugated diene monomer units, The block copolymer composition contains 10 to 30% by mass of conjugated diene monomer units, when the total mass of vinyl aromatic monomer units and conjugated diene monomer units in the block copolymer composition is 100% by mass. 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 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. The aforementioned block copolymer A has a block structure represented by (S1)-(S / B1), (S1) is a block containing 85-100% by mass of vinyl aromatic monomer units. (S / B1) is a tapered block containing vinyl aromatic monomer units and conjugated diene monomer units, with 20-60% by mass of conjugated diene monomer units. The aforementioned block copolymer A contains 5 to 15% by mass of conjugated diene monomer units, The aforementioned block copolymer B has a block structure represented as (S2)-(S / B2), (S2) is a block containing 85-100% by mass of vinyl aromatic monomer units. (S / B2) is a tapered block containing vinyl aromatic monomer units and conjugated diene monomer units, with 20-60% by mass of conjugated diene monomer units. The aforementioned block copolymer B contains more than 15% by mass and 50% by mass or less of conjugated diene monomer units. The aforementioned block copolymer C has a block structure represented as (S3)-(S / B3)-(S / B4), (S3) is a block containing 85-100% by mass of vinyl aromatic monomer units. (S / B3) and (S / B4) each contain vinyl aromatic monomer units and conjugated diene monomer units, and are tapered blocks containing 8 to 36% by mass of conjugated diene monomer units. The aforementioned block copolymer C contains 7 to 32% by mass of conjugated diene monomer units. The mass ratio of (S / B3) to (S / B4) is (S / B4) / (S / B3) = 0.6 to 5.5. Block copolymer composition. [2] The block copolymer resin composition, in terms of molecular weight distribution determined by GPC measurement, has a polystyrene-based molecular weight, At least one molecular weight peak is present in the range of 140,000 to 220,000 weight-average molecular weight, At least one molecular weight peak in the range of 50,000 to 90,000 weight-average molecular weight, A block copolymer resin composition according to [1], having the following characteristics: [3] The block copolymer composition according to [1] or [2], wherein the flexural modulus measured in accordance with ISO 178 using a Type A test specimen in accordance with ISO 3167 is 1300 MPa or more. [4] Further containing block copolymer D, The aforementioned block copolymer D has a block structure represented by (S4)-(S / B5), (S4) is a block containing 85-100% by mass of vinyl aromatic monomer units. (S / B5) is a tapered block containing vinyl aromatic monomer units and conjugated diene monomer units, with the conjugated diene monomer units being 5% by mass or more and less than 20% by mass. The aforementioned block copolymer D contains 4 to 20% by mass of conjugated diene monomer units. A block copolymer composition as described in any one of [1] to [3]. A heat-shrinkable film comprising a layer composed of a block copolymer composition described in any one of [5][1] to [4]. A container fitted with the heat-shrinkable film described in [6][5]. [Effects of the Invention]

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

[0010] Embodiments of the present invention will be described below. The various features shown in the embodiments below can be combined with each other. Furthermore, each feature can constitute an invention independently. In addition, any element not specified in the claims in the embodiments below is an optional element and can be omitted. Any number of zeros (for example, one or two) may be added to the end of the numerical values ​​disclosed in the following description. For example, one or two zeros 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. The block copolymer having vinyl aromatic monomer units and conjugated diene monomer units can be obtained, for example, by a living anionic polymerization reaction using an organolithium compound or the like as a polymerization initiator in an organic solvent. In living anionic polymerization, almost the entire amount of vinyl aromatic monomers and conjugated diene monomers subjected to the polymerization reaction can be converted into polymers, so a block copolymer having any primary structure can be obtained by changing the amount and order of addition of these monomers.

[0012] The block copolymer composition contains, as a block copolymer comprising a vinyl aromatic monomer unit and a conjugated diene monomer unit, a block copolymer A, a block copolymer B, and a block copolymer C. Preferably, the block copolymer composition further contains a block copolymer D as a block copolymer comprising a vinyl aromatic monomer unit and a conjugated diene monomer unit. In addition, the block copolymer composition may further contain a block copolymer comprising a vinyl aromatic monomer unit and a conjugated diene monomer unit other than the block copolymers A to D.

[0013] The block copolymer composition contains 10 to 30% by mass of the conjugated diene monomer unit when the total mass of the vinyl aromatic monomer unit and the conjugated diene monomer unit in the block copolymer composition is 100% by mass. Specific examples of the content of the conjugated diene monomer unit when the total mass of the vinyl aromatic monomer unit and the conjugated diene monomer unit in the block copolymer composition is 100% by mass include 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 the content may be within a range between any two of the numerical values exemplified herein.

[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 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, preferably containing 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. Alternatively, 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 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, preferably containing 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 block copolymers including vinyl aromatic monomer units and conjugated diene monomer units in the block copolymer composition is taken as 100% by mass, the content of the 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, 39% by mass, and may be within a range between any two of the numerical values exemplified herein. When the total content of block copolymers including vinyl aromatic monomer units and conjugated diene monomer units in the block copolymer composition is taken as 100% by mass, the content of the 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, 26% by mass, and may be within a range between any two of the numerical values exemplified herein. When the total content of block copolymers including vinyl aromatic monomer units and conjugated diene monomer units in the block copolymer composition is taken as 100% by mass, the content of the block copolymer C is specifically, for example, 35, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55 ,5 6, 57, 58, 59, 60, 65, 70, 75, 80, 85% by mass, and may be within a range between any two of the numerical values exemplified herein. When the total content of block copolymers including vinyl aromatic monomer units and conjugated diene monomer units in the block copolymer composition is taken as 100% by mass, the content of the 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, 30% by mass, and may be within a range between any two of the numerical values exemplified herein.

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

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

[0018] (S1) is a block of a (co)polymer containing vinyl aromatic monomer units, wherein the block contains vinyl aromatic monomer units in an amount of 85 to 100% by mass, preferably 95 to 100% by mass, relative to 100% by mass of the total monomer units constituting (S1), 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% by mass of conjugated diene monomer units relative to 100% by mass of the total monomer units constituting (S / B1), preferably 30 to 50% by mass, and more preferably 35 to 45% by mass. Specifically, the content of conjugated diene monomer units relative to 100% by mass of the total monomer units constituting (S / B1) is, for example, 20, 25, 30, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 50, 55, or 60% by mass, and may be within the range of any two of the values ​​exemplified here.

[0020] Block copolymer A contains 5 to 15% by mass of conjugated diene monomer units, preferably 7 to 13% by mass, relative to 100% by mass of block copolymer A. Specifically, 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 the range of 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 also contain monomer units other than vinyl aromatic monomer units and conjugated diene monomer units (other monomer units), and the content of 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 contains (substantially) no other monomer units.

[0021] Furthermore, block copolymer A does not have the block structure represented by (S3)-(S / B3)-(S / B4) described later.

[0022] <Block Copolymer B> Block copolymer B has a block structure represented as (S2)-(S / B2). (S2) is a block of a (co)polymer containing vinyl aromatic monomer units, and is a block containing vinyl aromatic monomer units in an amount of 85 to 100% by mass, preferably 95 to 100% by mass, relative to 100% by mass of the total monomer units constituting (S2). More preferably, it is a block made 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% by mass of conjugated diene monomer units relative to 100% by mass of the total monomer units constituting (S / B2), preferably 30 to 50% by mass, and more preferably 35 to 45% by mass. Specifically, the content of conjugated diene monomer units relative to 100% by mass of the total monomer units constituting (S / B2) is, for example, 20, 25, 30, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 50, 55, 60% by mass, and may be within the range of any two of the values ​​exemplified here.

[0024] Block copolymer B contains more than 15% by mass and 50% by mass of conjugated diene monomer units, preferably 20-40% by mass, based on 100% by mass of block copolymer B. Specifically, 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 the range of any two of the values ​​exemplified here. In addition, 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 than vinyl aromatic monomer units and conjugated diene monomer units (other monomer units), and the content of other monomer units is, for example, 0 to 2% by mass, preferably 0 to 1% by mass, and more preferably 0 to 0.1% by mass, relative to 100% by mass of block copolymer B. In one example, block copolymer B does not contain (substantially) other monomer units.

[0025] Furthermore, block copolymer B does not have the block structure represented by (S3)-(S / B3)-(S / B4) described later.

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

[0027] (S / B3) and (S / B4) are each copolymer blocks containing vinyl aromatic monomer units and conjugated diene monomer units, and are tapered blocks containing 8 to 36% by mass of conjugated diene monomer units relative to 100% by mass of the total monomer units constituting (S / B3) or (S / B4), preferably 10 to 30% by mass. The compositions of (S / B3) and (S / B4) may be different from each other. (S / B3) is a tapered block more preferably containing 8 to 20% by mass of conjugated diene monomer units relative to 100% by mass of the total monomer units constituting (S / B3), and even more preferably 9 to 15% by mass. (S / B4) is a tapered block containing conjugated diene monomer units in an amount of more than 20% by mass and 36% by mass or less, more preferably 25-35% by mass, relative to 100% by mass of the total monomer units constituting (S / B4). Specifically, 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) is, for example, 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, 36% by mass, and may be within the range of any two of the values ​​exemplified here.

[0028] Block copolymer C contains 7 to 32% by mass of conjugated diene monomer units, preferably 15 to 25% by mass, per 100% by mass of block copolymer C. Specifically, the content of conjugated diene monomer units per 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 the range of any two of the values ​​exemplified here. Block copolymer C may also contain 68 to 93% by mass of vinyl aromatic monomer units, per 100% by mass of block copolymer C. Block copolymer C may also contain monomer units other than vinyl aromatic monomer units and conjugated diene monomer units (other monomer units), and the content of other monomer units per 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 contains (substantially) no 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. Specifically, this mass ratio may be, for example, 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, 5.5, or within the range of 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 vinyl aromatic monomer units, and is a block containing vinyl aromatic monomer units in an amount of 85 to 100% by mass, preferably 95 to 100% by mass, relative to 100% by mass of the total monomer units constituting (S4). More preferably, it is a block made 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 and 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. Specifically, the content of conjugated diene monomer units relative to 100% by mass of the total monomer units constituting (S / B5) is, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19% by mass, and may be within the range of any two of the values ​​exemplified here.

[0032] Block copolymer D contains 4 to 20% by mass of conjugated diene monomer units, preferably 5 to 15% by mass, per 100% by mass of block copolymer D. Specifically, the content of conjugated diene monomer units per 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 the range of any two of the values ​​exemplified here. Block copolymer D may also contain 80 to 96% by mass of vinyl aromatic monomer units, per 100% by mass of block copolymer D. Block copolymer D may also contain monomer units other than vinyl aromatic monomer units and conjugated diene monomer units (other monomer units), and the content of other monomer units per 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 contains (substantially) no other monomer units.

[0033] Furthermore, block copolymer D does not have the block structure represented by (S3)-(S / B3)-(S / B4) as described above.

[0034] In this specification, "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 vinyl aromatic monomers and conjugated diene monomers are added together, the more reactive conjugated diene monomers polymerize preferentially, resulting in a polymerization chain with a high proportion of conjugated diene monomer units in the initial stages of block formation. However, as polymerization progresses, the concentration of conjugated diene monomers decreases and the concentration of vinyl aromatic monomers increases, resulting in a polymerization chain with a low proportion of conjugated diene monomer units in the final stages of block formation. Note that there are also blocks called "random blocks," etc., which are different from "tapered blocks." These refer to blocks in which the microscopic composition of vinyl aromatic monomer units and conjugated diene monomer units remains almost constant within the block.

[0035] <Each monomer unit> Vinyl aromatic monomer units are structural units derived from vinyl aromatic monomers used in the polymerization of each block copolymer. Vinyl aromatic monomers are compounds in which a vinyl group is bonded to an aromatic ring. Examples of vinyl aromatic monomers include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, α-methylstyrene, vinylnaphthalene, and vinylanthracene. The vinyl aromatic monomer preferably contains styrene, and more preferably styrene. These monomers may be used individually or in combination of two or more types. The vinyl aromatic monomers used in each block copolymer A to D (and thus the vinyl aromatic monomer units contained in the block copolymers) may be the same or different from each other, 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 copolymer. Conjugated diene monomers are compounds having a conjugated chemical structure represented as C=CC=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 contains 1,3-butadiene, and more preferably 1,3-butadiene. These monomers may be used individually or in combination of two or more types. 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, but they are preferably the same.

[0037] Furthermore, the content of conjugated diene monomer units is determined by the amount of vinyl aromatic monomers used in the production of each block copolymer. body and The amount of conjugated diene monomers can be calculated from the amount of conjugated diene monomers used, 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 and allowing it to react thoroughly, then adding potassium iodide solution and titrating with sodium thiosulfate / ethanol solution. The amount of conjugated diene monomer units is calculated from the amount of double bonds obtained by the method described above. For vinyl aromatic monomer units, the amount obtained by subtracting the amount of conjugated diene monomer units from the total amount of the sample is used to calculate the amount of vinyl aromatic monomer units.

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

[0039] Block copolymerization Body composition In one embodiment, the product has, in its molecular weight distribution determined by GPC measurement, at least two molecular weight peaks in the range of 140,000 to 220,000 weight-average molecular weight (polystyrene equivalent molecular weight), and at least one molecular weight peak in the range of 50,000 to 90,000 weight-average molecular weight. One of the molecular weight peaks in the range of 140,000 to 220,000 weight-average molecular weight is derived from block copolymer A. One of the molecular weight peaks in the range of 140,000 to 220,000 weight-average molecular weight is derived from block copolymer C. One of the molecular weight peaks in the range of 50,000 to 90,000 weight-average molecular weight is derived from block copolymer B.

[0040] Block copolymerization Body composition In one embodiment, the product has a molecular weight distribution determined by GPC measurement, with polystyrene-represented molecular weight and weight-average molecular weight. 140,000~220,000It has at least two molecular weight peaks in the range of 50,000 to 90,000 and at least two molecular weight peaks in the weight-average molecular weight range of 50,000 to 90,000. One of the molecular weight peaks in the weight-average molecular weight range of 140,000 to 220,000 is 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 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 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 derived from block copolymer D.

[0041] The weight-average molecular weight of block copolymer A (values ​​converted to 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. Specifically, the weight-average molecular weight of block copolymer A is, for example, 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 the range of any two of the values ​​exemplified here.

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

[0043] The weight-average molecular weight of block copolymer C (values ​​converted to 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. Specifically, the weight-average molecular weight of block copolymer C may be, for example, 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, or 300,000, and may be within the range of any two of the values ​​exemplified here.

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

[0045] <Additives, etc.> Block copolymerization Body composition The product may contain polymers other than block copolymers containing vinyl aromatic monomer units and conjugated diene monomer units. It may also contain other additives as needed.

[0046] Other additives include, for example, various stabilizers, lubricants, processing aids, antistatic agents, antifogging agents, lightfastness enhancers, softeners, plasticizers, and pigments. Each additive may be added to the block copolymer solution, or it 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, and 10% by mass, and may be within the range of any two of the values ​​exemplified here.

[0047] Examples of stabilizers include 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, phenolic antioxidants such as 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 bisstearoamide, sorbitan monostearate, saturated fatty acid esters of aliphatic alcohols, and pentaerythritol fatty acid esters.

[0048] <Properties of block copolymer compositions> (Flexural modulus) The block copolymer composition has a flexural modulus of elasticity measured according to ISO 178 using a Type A test specimen obtained by molding the block copolymer composition in accordance with ISO 3167, preferably 1300 MPa or higher, more preferably 1400 MPa or higher, and even more preferably 1500 MPa or higher. Meeting this range provides excellent rigidity. The upper limit of the flexural modulus of elasticity is, for example, 2500 MPa or less, and from the viewpoint of impact resistance, 2000 MPa or less. Specifically, the flexural modulus of elasticity is, for example, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500 MPa, and may be within the range of any two of the values ​​exemplified here.

[0049] <Method for producing block copolymer composition> (Method of manufacturing block copolymers) The method for producing block copolymers A to D is not particularly limited, but for example, they can be obtained by a living anionic polymerization reaction of monomer raw materials including vinyl aromatic monomers and conjugated diene monomers using an organolithium compound as a polymerization initiator in an organic solvent.

[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] Organolithium compounds are compounds in which one or more lithium atoms are bonded to the molecule. Examples of organolithium compounds include monofunctional organolithium compounds such as ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, and tert-butyllithium, and polyfunctional organolithium compounds such as hexamethylenedisitium, butadienyldilithium, and isoprenyldilithium. A particularly preferred organolithium compound is n-butyllithium.

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

[0053] The block copolymer obtained in this way is deactivated by adding a polymerization inhibitor such as water, alcohol, or carbon dioxide in an amount sufficient to deactivate the active ends. Any method can be used to recover the copolymer from the obtained block copolymer solution (polymerization solution), such as (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) precipitation by concentrating the solution with a concentrator and then removing the solvent with a vented extruder (devaporation extrusion method), or (D) recovery of the copolymer by dispersing the solution in water and heating and removing the solvent by blowing in steam (steam stripping method). Devaporation extrusion is particularly preferred.

[0054] The block copolymer composition is obtained by mixing a block copolymer containing three or more vinyl aromatic monomer units and conjugated diene monomer units obtained by the above-described manufacturing method. Known methods can be used for mixing. For example, pellets or powders of the block copolymer may be dry-blended using a Henschel mixer, ribbon blender, super mixer, and V-blender, or they may be melted and pelletized using an extruder. In one embodiment, melt mixing is preferred. Alternatively, a method of mixing polymer solutions (polymerization solutions) and then removing the solvent can also be used. In addition, other additives mentioned above may be added and mixed as needed.

[0055] 2. Film and container A film according to one embodiment of the present invention is a molded article obtained by molding the block copolymer composition described above. The film is, for example, a heat-shrinkable film, and is a heat-shrinkable film containing the block copolymer composition described above. 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 distinction) extruded using the block copolymer composition (e.g., its pellets) by a known method, such as the T-die method or the tubular method. Biaxial stretching by the T-die method is particularly preferred. When extruding, if necessary, an anti-blocking agent such as high-impact polystyrene may be added to the block copolymer composition (e.g., its pellets) 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 comprises a layer composed of the block copolymer composition. The heat-shrinkable film may also comprise only a layer composed of the block copolymer composition (single layer or multiple layer), or another resin layer may be laminated on at least one side of the layer composed of the block copolymer composition. To obtain a heat-shrinkable film with a multilayer structure, another resin layer may be laminated onto a film composed of the block copolymer composition after stretching, or a sheet obtained by forming a film of the block copolymer composition may be laminated with another resin layer and then stretched, or a multilayer sheet obtained 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 (such as homopolymers of styrene monomers).

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

[0058] Examples of biaxial stretching include, for instance, 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 simultaneously or separately in the extrusion direction and the circumferential direction.

[0059] The stretching temperature is preferably, for example, 60 to 120°C. A temperature of 60°C or higher makes the sheet or film less likely to break during stretching, while a temperature of 120°C or lower tends to result in good shrinkage characteristics and thickness accuracy of the resulting film. There are no particular restrictions on the stretching ratio, but a ratio of 1.5 to 8 times is preferable. A ratio of 1.5 times or higher tends to result in good thermal shrinkage, while a ratio of 8 times or lower makes the sheet or film less likely to break during stretching.

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

[0061] <Characteristics of heat-shrinkable film> (Impact strength) Heat shrinkable fill Mu The impact strength is preferably 40 kJ / m or more, more preferably 45 kJ / m or more, and even more preferably 50 kJ / m or more. Meeting this range provides 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. Specifically, the impact strength is, for example, 40, 45, 50, 55, 60, 65, 70 kJ / m, and may be within the range of any two of the values ​​exemplified here. The impact strength of the film is measured in accordance with ASTM D3420 by the method described below. (1) Cut out sample pieces from the heat-shrinkable film, with the MD measuring 100 mm and the TD measuring 100 mm. (2) Using an impact tester manufactured by Tester Industries Co., Ltd., the cut sample piece is placed in the measuring stand, and the film is punched with 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 the impact strength per unit thickness (kJ / m) is calculated by dividing it by the film thickness.

[0062] (Thermal shrinkage rate) The heat shrinkage rate of the heat shrinkable film at 70°C (T=70) is preferably 5-25%, more preferably 7-15%. The heat shrinkage rate of the heat shrinkable film at 100°C (T=100) is preferably 65-80%, more preferably 70-75%. Each heat shrinkage rate is measured by the following method. do . (1) Cut out test pieces from the heat-shrinkable film with MD measuring 100 mm and TD measuring 100 mm. (2) Immerse the test specimen completely in warm water at T°C for 10 seconds, then remove it, wipe off the moisture thoroughly, and measure the length L (mm) of TD. (3) The thermal shrinkage rate is calculated using the following formula. Thermal shrinkage rate (%) = {(100-L) / 100} × 100

[0063] (Compressive strength) The compressive strength of the heat-shrinkable film, measured according to the method in accordance with JIS P8126, is preferably 6N or higher, and more preferably 8N or higher. The higher this value, the less likely the film is to buckle when attached to a container, resulting in superior attachment performance.

[0064] <Application> The above heat-shrinkable film can be used as a heat-shrinkable label, a heat-shrinkable cap seal, etc. It can also be used as a packaging film, etc.

[0065] A container according to one embodiment of the present invention is the heat-shrinkable film Mu This refers to a container to which a label, sticker, or other label has been attached, such as a PET bottle. [Examples]

[0066] The present invention will be described in more detail below with reference to examples. These examples are illustrative and do not limit the scope of the present invention.

[0067] [Synthesis of block copolymers] Block copolymers P1 to P20 were produced according to the conditions in Tables 1 and 2 by the following procedure. In the synthesis of each block copolymer, if there was no step corresponding to (5) in the table, it is indicated as "-" below, but in this case, step (6) was performed following (4).

[0068] <Block copolymer P1> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 1400 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 150 kg of styrene was added and the temperature was raised to 40°C to allow polymerization. (4) After the styrene was completely consumed, the internal temperature was cooled to below 60°C, and 30 kg of styrene and 20 kg of 1,3-butadiene were added simultaneously and polymerized. (5)- (6) After the styrene and 1,3-butadiene were completely consumed, 220 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P1 as pellets.

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

[0070] <Block copolymer P3> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 1300 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 26 kg of styrene was added and the temperature was raised to 80°C to polymerize it. (4) After the styrene was completely consumed, the internal temperature was cooled to below 50°C, and 67 kg of styrene and 20 kg of 1,3-butadiene were added simultaneously and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to below 50°C, and 67 kg of styrene and 20 kg of 1,3-butadiene were added simultaneously and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 210 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P3.

[0071] <Block Copolymer P4> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 3000 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 60 kg of styrene was added and the temperature was raised to 65°C to polymerize it. (4) After the styrene was completely consumed, the internal temperature was cooled to below 40°C, and 124 kg of styrene and 16 kg of 1,3-butadiene were added simultaneously and polymerized. (5)- (6) After the styrene and 1,3-butadiene were completely consumed, 480 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P4.

[0072] <Block Copolymer P5> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 1400 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 150 kg of styrene was added and the temperature was raised to 40°C to allow polymerization. (4) After the styrene was completely consumed, the internal temperature was cooled to below 60°C, and 40 kg of styrene and 10 kg of 1,3-butadiene were added simultaneously and polymerized. (5)- (6) After the styrene and 1,3-butadiene were completely consumed, 220 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P5.

[0073] <Block Copolymer P6> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 1500 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 150 kg of styrene was added and the temperature was raised to 40°C to allow polymerization. (4) After the styrene was completely consumed, the internal temperature was cooled to below 60°C, and 20 kg of styrene and 30 kg of 1,3-butadiene were added simultaneously and polymerized. (5)- (6) After the styrene and 1,3-butadiene were completely consumed, 230 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P6.

[0074] <Block Copolymer P7> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 3600 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 40 kg of styrene was added and the temperature was raised to 65°C to polymerize it. (4) After the styrene was completely consumed, the internal temperature was cooled to below 35°C, and 128 kg of styrene and 32 kg of 1,3-butadiene were added simultaneously and polymerized. (5)- (6) After the styrene and 1,3-butadiene were completely consumed, 570 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P7.

[0075] <Block Copolymer P8> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 4500 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 40 kg of styrene was added and the temperature was raised to 65°C to polymerize it. (4) After the styrene was completely consumed, the internal temperature was cooled to below 30°C, and 64 kg of styrene and 96 kg of 1,3-butadiene were added simultaneously and polymerized. (5)- (6) After the styrene and 1,3-butadiene were completely consumed, 710 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P8.

[0076] <Block Copolymer P9> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 1200 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 26 kg of styrene was added and the temperature was raised to 80°C to polymerize it. (4) After the styrene was completely consumed, the internal temperature was cooled to below 50°C, and 80 kg of styrene and 7 kg of 1,3-butadiene were added simultaneously and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to below 50°C, and 80 kg of styrene and 7 kg of 1,3-butadiene were added simultaneously and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 190 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P9.

[0077] <Block copolymer P10> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 1400 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 26 kg of styrene was added and the temperature was raised to 80°C to polymerize it. (4) After the styrene was completely consumed, the internal temperature was cooled to below 50°C, and 56 kg of styrene and 31 kg of 1,3-butadiene were added simultaneously and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to below 50°C, and 56 kg of styrene and 31 kg of 1,3-butadiene were added simultaneously and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 230 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P10.

[0078] <Block copolymer P11> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 1300 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 26 kg of styrene was added and the temperature was raised to 80°C to polymerize it. (4) After the styrene was completely consumed, the internal temperature was cooled to below 50°C, and 22 kg of styrene and 7 kg of 1,3-butadiene were added simultaneously and polymerized. (5) After the styrene and 1,3-butadiene have been completely consumed, the internal temperature is cooled to below 35°C. 、1 12 kg of styrene and 33 kg of 1,3-butadiene were added simultaneously and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 210 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P11.

[0079] <Block copolymer P12> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 1300 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 26 kg of styrene was added and the temperature was raised to 80°C to polymerize it. (4) After the styrene was completely consumed, the internal temperature was cooled to below 50°C, and 78 kg of styrene and 24 kg of 1,3-butadiene were added simultaneously and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to below 60°C, and 56 kg of styrene and 16 kg of 1,3-butadiene were added simultaneously and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 210 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P12.

[0080] <Block copolymer P13> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 1400 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 150 kg of styrene was added and the temperature was raised to 40°C to allow polymerization. (4) After the styrene was completely consumed, the internal temperature was cooled to below 60°C, and 44 kg of styrene and 6 kg of 1,3-butadiene were added simultaneously and polymerized. (5)- (6) After the styrene and 1,3-butadiene were completely consumed, 220 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P13.

[0081] <Block copolymer P14> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 1400 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 150 kg of styrene was added and the temperature was raised to 40°C to allow polymerization. (4) After the styrene was completely consumed, the internal temperature was cooled to below 60°C, and 10 kg of styrene and 40 kg of 1,3-butadiene were added simultaneously and polymerized. (5)- (6) After the styrene and 1,3-butadiene were completely consumed, 240 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P14.

[0082] <Block Copolymer P15> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 3300 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 40 kg of styrene was added and the temperature was raised to 80°C to polymerize it. (4) After the styrene was completely consumed, the internal temperature was cooled to below 35°C, and 144 kg of styrene and 16 kg of 1,3-butadiene were added simultaneously and polymerized. (5)- (6) After the styrene and 1,3-butadiene were completely consumed, 520 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P15.

[0083] <Block Copolymer P16> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 4700 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 40 kg of styrene was added and the temperature was raised to 80°C to polymerize it. (4) After the styrene was completely consumed, the internal temperature was cooled to below 25°C, and 48 kg of styrene and 112 kg of 1,3-butadiene were added simultaneously and polymerized. (5)- (6) After the styrene and 1,3-butadiene were completely consumed, 730 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P16.

[0084] <Block Copolymer P17> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 1200 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 26 kg of styrene was added and the temperature was raised to 80°C to polymerize it. (4) After the styrene was completely consumed, the internal temperature was cooled to below 40°C, and 82 kg of styrene and 5 kg of 1,3-butadiene were added simultaneously and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to below 50°C, and 82 kg of styrene and 5 kg of 1,3-butadiene were added simultaneously and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 190 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P17.

[0085] <Block Copolymer P18> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 1500 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 26 kg of styrene was added and the temperature was raised to 80°C to polymerize it. (4) After the styrene was completely consumed, the internal temperature was cooled to below 40°C, and 46 kg of styrene and 35 kg of 1,3-butadiene were added simultaneously and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to below 50°C, and 46 kg of styrene and 35 kg of 1,3-butadiene were added simultaneously and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 230 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P18.

[0086] <Block copolymer P19> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 1300 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 26 kg of styrene was added and the temperature was raised to 80°C to polymerize it. (4) After the styrene was completely consumed, the internal temperature was cooled to below 40°C, and 19 kg of styrene and 6 kg of 1,3-butadiene were added simultaneously and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to below 35°C, and 115 kg of styrene and 34 kg of 1,3-butadiene were added simultaneously and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 210 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P19.

[0087] <Block copolymer P20> (1) 467 kg of cyclohexane was placed in the reaction vessel. (2) While stirring at an internal temperature of 30°C, 1300 mL of n-butyllithium (10% by mass cyclohexane solution) was added. (3) 26 kg of styrene was added and the temperature was raised to 80°C to polymerize it. (4) After the styrene was completely consumed, the internal temperature was cooled to below 40°C, and 88 kg of styrene and 28 kg of 1,3-butadiene were added simultaneously and polymerized. (5) After the styrene and 1,3-butadiene were completely consumed, the internal temperature was cooled to below 70°C, and 46 kg of styrene and 12 kg of 1,3-butadiene were added simultaneously and polymerized. (6) After the styrene and 1,3-butadiene were completely consumed, 210 g of water was added to deactivate the mixture and obtain a block copolymer polymerization solution. The block copolymer polymerization solution was pelletized using a defoliation extruder to obtain block copolymer P20.

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

[0089] <Weight average molecular weight> Block copolymer weight The average molecular weight was measured using the GPC measuring device and under the conditions described below, and calculated as the polystyrene-equivalent molecular weight using a calibration curve with standard polystyrene. Device name: HLC-8220GPC (manufactured by Tosoh Corporation) Columns: Four ShodexGPCKF-404 (manufactured by Showa Denko) connected in series. Temperature: 40℃ Detection: Differential refractive index Solvent: tetrahydrofuran Concentration: 2% by mass Calibration curve: Created using standard polystyrene (VARIAN).

[0090] <Monomeric content and block mass> The content of vinyl aromatic monomer units (styrene units) and conjugated diene monomer units (butadiene units) in the block copolymer and each block was calculated from the amount of vinyl aromatic monomer (styrene) and conjugated diene monomer (1,3-butadiene) charged during the production of the block copolymer. In addition, the mass of each block (S / B3) and (S / B4) was calculated from the amount of vinyl aromatic monomer at each polymerization stage. body and It was calculated from the amount of conjugated diene monomer used.

[0091] [Table 1]

[0092] [Table 2]

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

[0094] [Measurement / Analysis] The following measurements and analyses were performed on the block copolymer compositions of each example and comparative example.

[0095] <Flexural modulus> ISO dumbbell test specimens with a thickness of 4 mmt were prepared using pellets of a block copolymer composition by injection molding. These dumbbell specimens were measured in accordance with ISO 178 under conditions of a bending speed of 2 mm / min, relative humidity of 50%, and ambient temperature of 23°C.

[0096] [Table 3]

[0097] [Table 4]

[0098] To each of the RA1-RA12 and RB1-RB11 compositions, 1.3 parts by mass of high-impact polystyrene "E640N" (manufactured by Toyo Styrene Co., Ltd.) was added (dry blended) to 100 parts by mass of each composition to prepare heat-shrinkable films. The physical properties of the heat-shrinkable films are shown in Tables 5 and 6.

[0099] (1) Extrusion of the sheet before stretching Block copolymerization of each example and comparative example using a dry blend of high-impact polystyrene with an extruder equipped with a T-die with a lip width of 300 μm, capable of extruding sheets. Body composition The material was melted and extruded into a sheet. The extruder that melted the resin and supplied it to the T-die was 65mm in diameter. single A spool extruder was used, with a set temperature of 210°C. The T-die temperature was also set to 210°C. The resulting sheet thickness was 0.30 mm.

[0100] (2) Extension of the sheet before extension The obtained pre-stretched sheet was subjected to a longitudinal stretcher having two rolls with different rotation speeds, stretched 1.1 times in the MD direction at 90°C, and then subjected to a tenter-type transverse stretcher, stretched 4.5 times in the TD direction at 90°C, to finally produce a 50 μm thick block copolymer of the example and comparative example. Body composition A heat-shrinkable film was obtained using the resulting material.

[0101] <Thermal shrinkage rate> The thermal shrinkage rate of the film was measured under the conditions of T=70°C and 100°C, respectively, using the methods described below. (1) From the heat-shrinkable film obtained by stretching, test pieces with an MD width of 100 mm and a TD width of 100 mm were cut out. (2) The test specimen was completely immersed in warm water at T°C for 10 seconds, then removed, thoroughly wiped dry, and its length L (mm) in the TD direction was measured. (3) The thermal shrinkage rate was calculated using the following formula. Thermal shrinkage rate (%) = {(100-L) / 100} × 100

[0102] <Compressive strength> The compressive strength of the film was measured using a method compliant with JIS P8126. sexThe film was cut into strips measuring MD12.7mm and TD150mm, and then set in a cylindrical shape on a pre-fabricated support. The support was then placed on the stand of a tensile testing machine (RTG-1210, manufactured by A&D Co., Ltd.), and measurements were taken. Measurements were taken only for compressive 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 using the following method. (1) Sample pieces measuring 100 mm for the medium diameter and 100 mm for the torso diameter were cut from a heat-shrinkable film. (2) Using an impact tester manufactured by Tester Industries Co., Ltd., the cut sample piece was clamped in the measuring stand, and the film was punched with 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 per unit thickness (kJ / m).

[0104] [Table 5]

[0105] [Table 6]

Claims

1. A block copolymer composition containing a block copolymer comprising vinyl aromatic monomer units and conjugated diene monomer units, The block copolymer composition contains 10 to 30% by mass of conjugated diene monomer units, when the total mass of vinyl aromatic monomer units and conjugated diene monomer units in the block copolymer composition is 100% by mass. 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 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. The aforementioned 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, with 20 to 60% by mass of conjugated diene monomer units. The aforementioned block copolymer A contains 5 to 15% by mass of conjugated diene monomer units, The aforementioned 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, with 20 to 60% by mass of conjugated diene monomer units. The aforementioned block copolymer B contains more than 15% by mass and 50% by mass or less of conjugated diene monomer units. The aforementioned block copolymer C has a block structure represented as (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) each contain vinyl aromatic monomer units and conjugated diene monomer units, and are tapered blocks containing 8 to 36% by mass of conjugated diene monomer units. The aforementioned block copolymer C contains 7 to 32% by mass of conjugated diene monomer units. The mass ratio of (S / B3) to (S / B4) is (S / B4) / (S / B3) = 0.6 to 5.

5. Block copolymer composition.

2. The aforementioned block copolymer composition, in terms of its molecular weight distribution as measured by GPC, has a polystyrene-based molecular weight, At least one molecular weight peak is present in the range of 140,000 to 220,000 weight-average molecular weight, At least one molecular weight peak in the range of 50,000 to 90,000 weight-average molecular weight, A block copolymer composition according to claim 1, having the following characteristics.

3. The block copolymer composition according to claim 1, wherein the flexural modulus measured in accordance with ISO 178 using a Type A test specimen conforming to ISO 3167 is 1300 MPa or more.

4. Further containing block copolymer D, The aforementioned 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, with the conjugated diene monomer units being 5% by mass or more and less than 20% by mass. 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 a block copolymer composition according to any one of claims 1 to 4.

6. A container fitted with the heat-shrinkable film described in claim 5.

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