Block copolymer and method for producing the same

Abstract

The present invention provides a block copolymer that, when compounded with diene-based rubber, can yield a rubber composition with a higher glass transition temperature (Tg), and a method for producing the same. [Solution] A block copolymer comprising polymer block A containing vinyl aromatic monomer units and copolymer block B containing vinyl aromatic monomer units and conjugated diene monomer units, The total amount of 1,2-conjugates and 3,4-conjugates in the block copolymer is 30-90% of the total amount of conjugated diene monomer units. The content of conjugated diene monomer units in the total amount of the block copolymer is 5 to 30% by mass. The block copolymer is defined as one in which the content of polymer block A in the total amount of the block copolymer is 30% by mass or less.

Description

Technical Field

[0001] The present disclosure relates to a block copolymer and a method for producing the same.

Background Art

[0002] A block copolymer containing monomer units derived from an aromatic vinyl hydrocarbon and monomer units derived from a conjugated diene monomer has elasticity similar to that of natural rubber and synthetic rubber at room temperature, and has processability similar to that of a thermoplastic resin at high temperatures. Therefore, it is used in a wide range of fields such as various packaging materials, adhesive materials, resin modifiers, and substrate materials.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, diene rubbers such as styrene-butadiene rubber (SBR) are used as general-purpose rubber components, for example, in rubber compositions for tires. A rubber composition for tires preferably has a higher glass transition temperature Tg in terms of wear resistance.

[0005] An object of the present disclosure is to provide a block copolymer that can give a rubber composition having a higher glass transition temperature Tg when blended with a diene rubber, and a method for producing the same.

Means for Solving the Problems

[0006] The present disclosure includes the following aspects. [1] A block copolymer comprising a polymer block A containing vinyl aromatic monomer units and a copolymer block B containing vinyl aromatic monomer units and conjugated diene monomer units, The total amount of 1,2-conjugates and 3,4-conjugates in the block copolymer is 30-90% of the total amount of conjugated diene monomer units. The content of conjugated diene monomer units in the total amount of the block copolymer is 5 to 30% by mass. A block copolymer in which the content of polymer block A in the total amount of the block copolymer is 30% by mass or less. [2] A method for producing the block copolymer described in [1] above, The process involves forming copolymer block B in a reaction solution containing a chelating agent and an alkali metal alkoxide. A method for producing a block copolymer, wherein the ratio of the chelating agent to the alkali metal alkoxide in the reaction solution (chelating agent / alkali metal alkoxide) is 1.0 to 6.5 in molar ratio. [Effects of the Invention]

[0007] According to this disclosure, a block copolymer that can give a rubber composition with a higher glass transition temperature Tg when compounded with diene rubber, and a method for producing the same can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] Figures 1(a) to 1(c) are charts showing the results of dynamic viscoelasticity measurements at a frequency of 1 Hz for compositions containing the block copolymers of Example 1, Comparative Examples 1 and 2, and Reference Example (SBR), in the temperature range of -60°C to -10°C. [Figure 2] Figure 2 is a chart showing the results of dynamic viscoelasticity measurements at a frequency of 1 Hz for the composition containing the block copolymer of Example 1 and the reference example (SBR), specifically for the temperature range of -60°C to 120°C. [Modes for carrying out the invention]

[0009] One embodiment of the present disclosure will be described in detail below, but the scope of the present disclosure is not limited to the embodiment described herein, and various modifications can be made without departing from the spirit of the present disclosure. Each embodiment disclosed herein can be combined with any other features disclosed herein. If multiple upper and lower limits are given for a particular parameter, any combination of these upper and lower limits can be used to create a suitable numerical range. The lower and / or upper limits of the numerical ranges described herein may be replaced with numerical values ​​within that range, as shown in the examples. The expression "X~Y" indicating a numerical range means "X or greater and Y or less". If a particular description given for one embodiment also applies to other embodiments, that description may be omitted in the other embodiments.

[0010] [Block copolymer] The block copolymer according to this embodiment (hereinafter also simply referred to as "block copolymer") comprises aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units, and preferably the constituent units consist only of aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units.

[0011] The block copolymer comprises polymer block A containing vinyl aromatic monomer units (hereinafter also simply referred to as "block A") and copolymer block B containing vinyl aromatic monomer units and conjugated diene monomer units (hereinafter also simply referred to as "copolymer block B"). The total amount of 1,2-conjugates and 3,4-conjugates in the block copolymer is 30-90%, the content of conjugated diene monomer units in the total amount of block copolymer is 5-30% by mass, and the content of polymer block A in the total amount of block copolymer is 30% by mass or less.

[0012] The block copolymer according to this embodiment contains monomer units derived from aromatic vinyl hydrocarbons in both block A and block B, and its total content is greater than that of diene rubbers such as SBR, so the glass transition temperature Tg tends to be higher than that of diene rubbers. Furthermore, because it contains a large amount of copolymer block B, which has a structure similar to that of general diene rubbers, it has excellent compatibility with diene rubbers. As a result, when the block copolymer according to this embodiment is compounded with diene rubbers, it is highly compatible with diene rubbers and tends to yield a rubber composition with a higher glass transition temperature Tg. Moreover, when the total amount of 1,2-conjugates and 3,4-conjugates in the total amount of conjugated diene monomer units in the block copolymer is a predetermined amount, the glass transition temperature Tg tends to be even higher when compounded with diene rubbers. Furthermore, since the block copolymer according to this embodiment contains 1,2-conjugates and / or 3,4-conjugates in the conjugated diene monomer unit, carbon-carbon double bonds are also present in the side chains of the block copolymer. In this block copolymer, not only the carbon-carbon double bonds in the main chain but also the carbon-carbon double bonds in the side chains can act as reaction sites. Therefore, for example, a rubber composition containing a block copolymer and a diene-based rubber tends to have a higher crosslink density when vulcanized. Rubber compositions with a high glass transition temperature (Tg) and a high crosslink density tend to have better abrasion resistance.

[0013] The following will first describe the constituent units, such as aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units, and then the block structures, such as Block A and copolymer Block B.

[0014] (Aromatic vinyl hydrocarbon monomer units) Aromatic vinyl hydrocarbon monomer units are constituent units derived from aromatic vinyl hydrocarbon monomers. In this specification, "monomer units derived from monomers" refers to constituent units formed from monomers in polymerization reactions using those monomers.

[0015] The aromatic vinyl hydrocarbon monomer may be, for example, a compound having an aromatic ring and a vinyl group or vinylidene group bonded to the aromatic ring. Examples of aromatic rings include benzene rings and naphthalene rings, and these aromatic rings may have substituents. Examples of substituents that the aromatic ring may have include alkyl groups, alkoxy groups, halogeno groups (e.g., fluoro groups, chloro groups, bromo groups, iodo groups), etc. The vinyl group is a group represented as -CH=CH2. The vinylidene group bonded to the aromatic ring may be a group represented as, for example, -CR=CH2 (where R represents an alkyl group). The number of carbon atoms in the alkyl group in R may be, for example, 1 to 10, 1 to 5, or 1. R may be, for example, a methyl group.

[0016] Examples of aromatic vinyl hydrocarbon monomers include styrene compounds such as styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, and α-methylstyrene, as well as vinylnaphthalene and vinylanthracene. In one embodiment, the vinyl aromatic hydrocarbon monomer preferably comprises one or more styrene compounds selected from the group consisting of styrene, α-methylstyrene, o-methylstyrene, and p-methylstyrene, more preferably comprising one or more styrene compounds selected from the group consisting of α-methylstyrene and p-methylstyrene, and even more preferably containing styrene. The aromatic vinyl hydrocarbon monomer may be used alone or in combination of two or more.

[0017] Aromatic vinyl hydrocarbon monomer units are, for example, defined by the following formula (A-1): The constituent units may be represented by TIFF2026123726000002.tif28170. In formula (A-1), R 1 Ar represents a hydrogen atom or an alkyl group. 1 R indicates an aryl group. 1The number of carbon atoms in the alkyl group may be, for example, 1 to 10, 1 to 5, or 1. 1 This could be, for example, a methyl group. 1 Examples of aryl groups in this context include optionally substituted phenyl groups and optionally substituted naphthyl groups. Examples of substituents include alkyl groups, alkoxy groups, and halogen groups (e.g., fluoro groups, chloro groups, bromo groups, iodo groups). 1 This may be, for example, a phenyl group, a 4-methylphenyl group, a 2,4-dimethylphenyl group, or a 2,5-dimethylphenyl group, or it may be a phenyl group or a 4-methylphenyl group.

[0018] In one embodiment, the vinyl aromatic monomer unit preferably includes monomer units derived from one or more aromatic vinyl compounds selected from the group consisting of styrene, α-methylstyrene, and p-methylstyrene.

[0019] In one embodiment, the content of aromatic vinyl hydrocarbon monomer units in the total amount (100% by mass) of the block copolymer is preferably 50 to 95% by mass, more preferably 65 to 95% by mass, even more preferably 70 to 95% by mass, and particularly preferably 75 to 90% by mass. A content of 50 to 95% by mass of aromatic vinyl hydrocarbon monomer units tends to yield a rubber composition with a higher glass transition temperature (Tg) when compounded with diene-based rubber. The content of aromatic vinyl hydrocarbon monomer units in the total amount of the block copolymer can be calculated, for example, from the mass of aromatic vinyl hydrocarbon monomers used during the polymerization of the block copolymer. Furthermore, 1 It can also be calculated by 1H-NMR measurement.

[0020] (Conjugated diene monomer units) Conjugated diene monomer units are constituent units derived from conjugated diene monomers. Examples of conjugated diene monomers include butadiene monomers such as 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), and 2,3-dimethyl-1,3-butadiene, as well as 1,3-pentadiene and 1,3-hexadiene. In one embodiment, the conjugated diene monomer preferably contains 1,3-butadiene or isoprene, and more preferably contains 1,3-butadiene. These monomers may be used individually or in combination of two or more.

[0021] In one embodiment, the conjugated diene monomer unit preferably includes monomer units derived from one or more conjugated dienes selected from the group consisting of 1,3-butadiene and isoprene.

[0022] In one embodiment, it is preferable that the vinyl aromatic monomer unit comprises monomer units derived from one or more aromatic vinyl compounds selected from the group consisting of styrene, α-methylstyrene, and p-methylstyrene, and the conjugated diene monomer unit comprises monomer units derived from one or more conjugated dienes selected from the group consisting of 1,3-butadiene and isoprene.

[0023] Each conjugated diene monomer unit contains at least one conjugate selected from 1,2-conjugates and 3,4-conjugates. The 1,2-conjugate (or 3,4-conjugate) is formed by polymerization such that the carbon atoms at positions 1 and 2 (or 3 and 4) of the conjugated diene skeleton bond with an adjacent monomer unit, and has a carbon-carbon double bond in its side chain. Including at least one conjugate selected from 1,2-conjugates and 3,4-conjugates makes it easier to obtain a rubber composition with a higher glass transition temperature (Tg) when compounded into diene-based rubber. Furthermore, when the rubber composition is vulcanized by a crosslinking reaction, the carbon-carbon double bonds in the side chains of the block copolymer can also act as crosslinking reaction sites, making it easier to achieve a higher crosslink density in the rubber composition. Rubber compositions with a high glass transition temperature (Tg) and high crosslink density tend to have better abrasion resistance.

[0024] In one embodiment, the conjugated diene monomer unit may have a 1,4 - conjugate in addition to the 1,2 - conjugate and the 3,4 - conjugate. The 1,4 - conjugate is a structure formed by polymerization such that the carbon atoms at the 1 - position and 4 - position of the conjugated diene skeleton are bonded to adjacent monomer units, and has a carbon - carbon double bond in the main chain.

[0025] In one embodiment, the conjugated diene monomer unit is, for example, the following formula (B - i), formula (B - ii) and formula (B - iii): Among the structural units represented by TIFF2026123726000003.tif39170, it is preferable to contain one or more structural units selected from the structural units represented by formula (B - ii) and formula (B - iii), and it may further contain each structural unit represented by formula (B - i). The structural unit represented by formula (B - i) is a 1,4 - conjugate, the structural unit represented by formula (B - ii) is a 1,2 - conjugate, and the structural unit represented by formula (B - iii) is a 3,4 - conjugate. In formula (B - i), formula (B - ii) and formula (B - iii), R 2a , R 2b , R 2c each independently represents a hydrogen atom or an alkyl group. When R 2b is a hydrogen atom, formula (B - ii) and formula (B - iii) represent the same structural unit. The number of carbon atoms of the alkyl group in R 2a , R 2b , R 2c may be, for example, 1 to 10, may be 1 to 5, or may be 1. R 2 may be, for example, a methyl group.

[0026] The total of the 1,2 - conjugate and the 3,4 - conjugate in the total amount (100 mol%) of the conjugated diene monomer units in the block copolymer is 30 to 90 mol%. When the total of the 1,2 - conjugate and the 3,4 - conjugate in the total amount of the conjugated diene monomer units in the block copolymer is 30 to 90 mol%, it is easy to provide a rubber composition having a higher glass transition temperature Tg when blended with a diene - based rubber. From the viewpoint of making it easier for the resulting rubber composition to have a higher glass transition temperature (Tg), the total amount of 1,2-bonds and 3,4-bonds is preferably 40-90 mol%, more preferably 50-85 mol%, even more preferably 60-80 mol%, and particularly preferably 65-75 mol%. The content of 1,2-conjugates and 3,4-conjugates in the total amount (100 mol%) of conjugated diene monomer units in the block copolymer is: 1 It can be calculated by 1H-NMR measurement.

[0027] 1,2- and 3,4-conjugates are readily formed during the polymerization of block copolymers by polymerizing blocks containing conjugated diene monomer units in the presence of a chelating agent and an alkali metal alkoxide. By selecting the type of alkali metal ion contained in the alkali metal alkoxide, the content of 1,2- and 3,4-conjugates relative to the total amount of conjugated diene monomer units in the block copolymer can be easily adjusted. For example, sodium ions (Na) can be used as alkali metal ions. + If ) is selected, lithium ion (Li + Compared to using ( ), the content of 1,2- and 3,4-conjugates tends to be higher. Furthermore, the ratio of 1,2- and 3,4-conjugates can be controlled by adjusting the polymerization temperature. For example, as the polymerization temperature increases, the content of 1,2- and 3,4-conjugates tends to decrease, so lowering the polymerization temperature tends to increase the ratio of 1,2- and 3,4-conjugates.

[0028] The content of conjugated diene monomer units in the total amount (100% by mass) of the block copolymer is 5 to 30% by mass, more preferably 8 to 28% by mass, even more preferably 10 to 25% by mass, and particularly preferably 15 to 23% by mass. A conjugated diene monomer unit content of 5 to 30% by mass makes it easier to obtain a rubber composition with a higher glass transition temperature (Tg) when compounded with diene-based rubber. The content of conjugated diene monomer units in the total amount of the block copolymer can be calculated, for example, from the mass of conjugated diene monomers used during the polymerization of the block copolymer. Furthermore, halogen addition methods and 1 It can also be calculated by 1H-NMR measurement.

[0029] (Primary structure (block structure)) The block copolymer comprises block A and copolymer block B as described above. The inclusion of block A and copolymer block B makes it easier to obtain a rubber composition with a higher glass transition temperature (Tg) when compounded with diene rubber.

[0030] In this specification, the content of each block in the block copolymer described below can be calculated from the mass of the monomer used for polymerization of that block relative to the total mass of monomers used for polymerization of the block copolymer. 1 It can also be calculated by 1H-NMR measurement. Furthermore, the content of aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units in each block can be calculated from the mass of aromatic vinyl hydrocarbon monomers or conjugated diene monomers relative to the total mass of monomers used in the polymerization of each block. 1 It can also be calculated by 1H-NMR measurement.

[0031] (Block A) Block A is a block mainly containing aromatic vinyl hydrocarbon monomer units, such as a polymer block of aromatic vinyl hydrocarbon monomers. The aromatic vinyl hydrocarbon monomers are as described above. In this specification, "mainly containing" means that it is contained in an amount exceeding 50% by mass of all constituent units contained in the block. The content of aromatic vinyl hydrocarbon monomer units in block A is preferably 70% by mass or more, more preferably 90% by mass or more, even more preferably 97% by mass or more, and may be 100% by mass, of all constituent units of block A. By including block A in the block copolymer, it is easier to obtain a rubber composition having a higher glass transition temperature Tg than conventional rubbers when compounded with diene rubbers.

[0032] A block copolymer may contain one block A, or it may contain two or more. In one embodiment, it is preferable that the block copolymer has block A at both ends of the molecular difference chain. When the block copolymer contains two or more block As, the two or more block As may be identical, or it may contain two or more types of block As that differ in the type and / or content of aromatic vinyl hydrocarbon monomers.

[0033] Block A may contain monomer units (a) derived from monomers that can copolymerize with aromatic vinyl hydrocarbon monomers. Examples of such monomer units (a) include ethylene, propylene, vinyl chloride, vinyl acetate, (meth)acrylic acid, alkyl (meth)acrylate, (meth)acrylamide, (meth)acrylonitrile, and conjugated dienes.

[0034] The size of one block A is preferably 1 to 30% by mass, more preferably 1.5 to 20% by mass, even more preferably 2.0 to 10% by mass, and particularly preferably 2.5 to 6.0% by mass, based on the total amount (100% by mass) of the block copolymer. When the size of one block A is 1 to 30% by mass, it is easier to achieve high compatibility when compounded with diene-based rubbers, and it is easier to obtain a rubber composition with a higher glass transition temperature (Tg).

[0035] The total amount of block A in the block copolymer is 30% by mass or less of the total amount of block copolymer (100% by mass), preferably 1 to 25% by mass, more preferably 3 to 20% by mass, and even more preferably 5 to 15% by mass. Having a total amount of block A in the block copolymer of 30% by mass or less of the total amount of block copolymer makes it easier to achieve high compatibility when compounded with diene-based rubbers, and more easily yields a rubber composition with a higher glass transition temperature (Tg).

[0036] (Copolymer Block B) Copolymer block B is a block containing a copolymer of aromatic vinyl hydrocarbon monomer units and the conjugated diene monomer units, for example, a copolymer block of aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units. The copolymer block of aromatic vinyl hydrocarbon monomers and conjugated diene monomers may be either a random block or a tapered block. A tapered block is a block having a tapered structure in which the distribution density of specific monomer units constituting the copolymer is gradient and arranged in a tapered shape within the block. When copolymer block B is polymerized, if aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units are added simultaneously, a tapered block is easily formed, and if aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units are added separately at predetermined flow rates, a random block is easily formed. The inclusion of copolymer block B in the block copolymer makes it easier to achieve higher compatibility with diene-based rubbers, thereby making it easier to obtain a rubber composition with a higher glass transition temperature Tg when compounded with diene-based rubbers.

[0037] The aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units are as described above. The aromatic vinyl hydrocarbon monomer units contained in copolymer block B may be the same as or different from the aromatic vinyl hydrocarbon monomer units contained in block A. Furthermore, each of the aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units may be used individually or in combination of two or more types.

[0038] A block copolymer may contain one copolymer block B, or two or more. If a block copolymer contains two or more copolymer block Bs, these two or more copolymer block Bs may be identical, or they may have different block structures such as random blocks or tapered blocks, or they may contain two or more copolymer block Bs with different types and / or content of aromatic vinyl hydrocarbon monomers and / or conjugated diene monomers.

[0039] From the viewpoint of easily obtaining a rubber composition with a higher glass transition temperature Tg when compounded with diene rubber, the content of aromatic vinyl hydrocarbon monomer units in one copolymer block B is preferably 40 to 90% by mass, more preferably 50 to 90% by mass, even more preferably 60 to 85% by mass, and particularly preferably 65 to 80% by mass, in the total amount (100% by mass) of one copolymer block B. The total content of aromatic vinyl hydrocarbon monomer units in copolymer block B is preferably 40 to 90% by mass, more preferably 50 to 90% by mass, even more preferably 60 to 85% by mass, and particularly preferably 65 to 80% by mass, based on the total amount (100% by mass) of copolymer block B, from the viewpoint of easily yielding a rubber composition with a higher glass transition temperature Tg.

[0040] From the viewpoint of easily yielding a rubber composition with a higher glass transition temperature Tg, the content of conjugated diene monomer units in one copolymer block B is preferably 10 to 60% by mass, more preferably 10 to 50% by mass, even more preferably 15 to 40% by mass, and particularly preferably 20 to 35% by mass, in the total amount (100% by mass) of one copolymer block B. The total content of conjugated diene monomer units in copolymer block B is preferably 10 to 60% by mass, more preferably 10 to 50% by mass, even more preferably 15 to 40% by mass, and particularly preferably 20 to 35% by mass, based on the total amount (100% by mass) of copolymer block B, from the viewpoint of easily yielding a rubber composition with a higher glass transition temperature Tg.

[0041] From the viewpoint of easily yielding a rubber composition with a higher glass transition temperature Tg, and from the viewpoint of easily increasing the crosslinking density in the vulcanized rubber composition, the size of one copolymer block B is preferably 30 to 98% by mass, more preferably 35 to 95% by mass, even more preferably 40 to 93% by mass, and particularly preferably 45 to 90% by mass, of the total amount (100% by mass) of the block copolymer.

[0042] From the viewpoint of making it easier to improve compatibility with diene-based rubbers and thereby easily obtain a rubber composition with a higher glass transition temperature Tg, the total amount of copolymer block B in the block copolymer is preferably 30 to 98% by mass, more preferably 35 to 95% by mass, even more preferably 40 to 93% by mass, and particularly preferably 45 to 90% by mass, relative to the total amount of block copolymer (100% by mass).

[0043] (Block structure) The block copolymer preferably contains one or more block structures selected from the structures represented by the following formulas 1 to 3. (A) l -(B) m formula 1 (A) l -(B) m -(A) n formula 2 (B) l -(A) m -(B) n formula 3 In formulas 1 to 3, (A) represents polymer block A containing vinyl aromatic monomer units, and (B) represents copolymer block B containing vinyl aromatic monomer units and conjugated diene monomer units. l, m, and n are independent integers of 1 or more in each formula, preferably integers from 1 to 3, more preferably 1 or 2, and even more preferably 1. When l, m, and n are integers of 2 or more, adjacent blocks can be distinguished from cases where l, m, and n are 1 by differences in the types and / or content of monomers they contain. In formulas 1 and 2, when m is an integer of 2 or more, and in formula 3, when n is an integer of 2 or more, adjacent blocks B can also be distinguished by differences in block structure, such as random blocks and tapered blocks. In Equation 2, the two blocks A may have the same or different types and / or content of aromatic vinyl hydrocarbon monomers. In Equation 3, the two blocks B may have the same or different types and / or content of conjugated diene monomers, and their block structures may be the same or different. In one embodiment, from the viewpoint of easily increasing the glass transition temperature Tg of the rubber composition, the block copolymer preferably contains a structure represented by formula 2.

[0044] In one embodiment, if the block copolymer contains a structure represented by formula 2, it is preferable that it contains one or more structures selected from the following structures represented by formulas 2-1 to 2-6. (A) l -(B-2) m -(A) n Formula 2-1 (A) l -(B-1) m -(B-2) n -(A) o Formula 2-2 (A) l -(B-2) m -(B-1) n -(B-2) o -(A)p Formula 2-3 (A) l -(B-1) m -(B-2) n -(B-1) o -(A) p Formula 2-4 (A) l -(B-1) m -(B-2) n -(B-1) o -(B-2) p -(A) q Formula 2-5

[0045] In formulas 2-1 to 2-5, (A) represents polymer block A containing vinyl aromatic monomer units, (B-1) represents a block consisting of conjugated diene monomer units, and (B-2) represents a block containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units. l, m, n, o, p, and q each represent an integer of 1 or more independently for each formula, preferably an integer between 1 and 3, more preferably 1 or 2, and even more preferably 1. When l, m, n, o, p, and q are integers of 2 or more, adjacent blocks can be distinguished from the case where l, m, n, o, p, and q are 1 by the difference in the types and / or content of the monomers contained, or by the difference in the content of 1,2-conjugates and 3,4-conjugates contained.

[0046] In formulas 2-3 and 2-5, block B-2, which contains two aromatic vinyl hydrocarbon monomer units and a conjugated diene monomer unit, may have the same or different types and / or content of aromatic vinyl hydrocarbon monomers and / or conjugated diene monomers, and may have the same or different content of 1,2-bonds and 3,4-bonds. In formulas 2-4 and 2-5, the two blocks B-1 may have the same or different types of conjugated diene monomers, and may have the same or different content of 1,2-bonds and 3,4-bonds.

[0047] In one embodiment, the block copolymer preferably includes a structure represented by formula 2-1 and / or a structure represented by formula 2-2, and more preferably includes a structure represented by formula 2-1. The structure of the block copolymer is 1 H-NMR and 13 Measurement can be performed using methods such as 13C-NMR and ozonolysis GPC.

[0048] The block copolymer may have a structure in which two or more structures selected from formulas 1 to 3 and formulas 2-1 to 2-5 are bonded together by a coupling agent. A block copolymer in which the structures of formulas 1 to 3 and formulas 2-1 to 2-5 are bonded together by a coupling agent can be obtained, for example, by adding the required amount of a bifunctional or more coupling agent at the end of polymerization and carrying out a coupling reaction.

[0049] The block copolymer has a number-average molecular weight (Mn) of preferably 30,000 or less, more preferably 3,000 to 30,000, even more preferably 5,000 to 20,000, even more preferably 6,000 to 15,000, and particularly preferably 7,000 to 12,000. In one embodiment, the number-average molecular weight (Mn) of the block copolymer is preferably 6,000 to 10,000. When the number-average molecular weight (Mn) of the block copolymer is 30,000 or less, it is easier to achieve higher compatibility when compounded with diene-based rubbers, thereby making it easier to obtain a rubber composition with a higher glass transition temperature (Tg). The number-average molecular weight (Mn) can be measured, for example, using gel permeation chromatography (GPC).

[0050] The molecular weight distribution (Mw / Mn) of the block copolymer is preferably 3 or less, more preferably 1.05 to 2.20, more preferably 1.10 to 2.18, even more preferably 1.20 to 1.85, and particularly preferably 1.30 to 1.80. The molecular weight distribution (Mw / Mn) can be measured, for example, using gel permeation chromatography (GPC).

[0051] The glass transition temperature (Tg) of the block copolymer is preferably 0 to 100°C, more preferably 10 to 80°C, even more preferably 30 to 75°C, and particularly preferably 40 to 65°C. When the glass transition temperature (Tg) of the block copolymer is 0 to 100°C, it is easier to obtain a rubber composition with a higher glass transition temperature (Tg) when compounded with diene-based rubber. The glass transition temperature (Tg) of the block copolymer can be calculated from the inflection point of the thermal analysis curve obtained by measurement using differential scanning calorimeter (DSC).

[0052] When the polymerization of block copolymers is carried out in the presence of sodium alkoxide, sodium may be detected in measurements such as atomic absorption spectrometry, X-ray fluorescence spectrometry, and ICP emission spectrometry.

[0053] [Method for manufacturing block copolymer] The method for producing a block copolymer according to this embodiment includes forming a copolymer block B in a reaction solution containing a chelating agent and an alkali metal alkoxide, wherein the blending ratio of the chelating agent and the alkali metal alkoxide in the reaction solution (chelating agent / alkali metal alkoxide) is 1.0 to 6.5 in molar ratio, preferably 2.0 to 6.3, more preferably 3.0 to 6.2, even more preferably 4.0 to 6.1, and particularly preferably 5.0 to 6.0. The method for producing a block copolymer includes forming a copolymer block B in a reaction solution containing a chelating agent and an alkali metal alkoxide, and by setting the blending ratio of the chelating agent and the alkali metal alkoxide within the above predetermined range, a block copolymer that can give a rubber composition with a higher glass transition temperature Tg when blended with diene rubber is easily obtained.

[0054] In reaction solutions to which chelating agents and alkali metal alkoxides are added, the stability and reactivity of polymerization-active species are improved, making it easier to obtain block copolymers with large molecular weights. Furthermore, in reaction solutions to which chelating agents and alkali metal alkoxides are added, the polymerization rate is increased, and the polymerization reaction proceeds even at room temperature (e.g., 23°C), eliminating the need to heat the reaction solution, and the reaction can be carried out using only a cooling means to cool the reaction solution. In addition, in reaction solutions to which chelating agents and alkali metal alkoxides are added, 1,2-conjugates (or 3,4-conjugates) are more easily formed from conjugated dienes.

[0055] In one embodiment, the method for producing a block copolymer is: (iA): Using aromatic vinyl hydrocarbon monomers to form block A containing aromatic vinyl hydrocarbon monomer units (hereinafter also simply referred to as "step iA"), and (iB): Forming copolymer block B containing aromatic vinyl hydrocarbon monomers and conjugated diene monomers using aromatic vinyl hydrocarbon monomers and conjugated diene monomer units (hereinafter also simply referred to as "step iB"). Includes, It is preferable that the formation of (iB) copolymer block B is carried out in the presence of a chelating agent and an alkali metal alkoxide.

[0056] Block A and copolymer block B, aromatic vinyl hydrocarbon monomers and conjugated diene monomers, and aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units are as described above and will therefore not be described here.

[0057] (Chelating agents and alkali metal alkoxides) In the method for producing the block copolymer according to this embodiment, the copolymer block B is formed in a reaction solution containing a chelating agent and an alkali metal alkoxide. In one embodiment, it is preferable that the process of obtaining a copolymer block B containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units by anionic polymerization of an aromatic vinyl hydrocarbon monomer and a conjugated diene monomer (step iB) is carried out in a reaction solution containing a chelating agent and an alkali metal alkoxide.

[0058] Any chelating agent capable of coordinating to a cation derived from an anionic polymerization initiator (e.g., a lithium cation) is acceptable. The chelating agent may be appropriately selected from known chelating agents. Examples of chelating agents include compounds having a linear molecular skeleton and nitrogen atoms bonded to both ends of the molecular skeleton.

[0059] In one embodiment, the chelating agent is, for example, the following formula (I): The compound may be represented by TIFF2026123726000004.tif30170. In formula (I), n and m each independently represent integers from 0 to 3, preferably 0 or 1, and R 3 These are single bonds, -O-, or -NR 8 - indicates, R 4 , R 5 , R 6 , R 7 , and R 8 Each of these independently represents an alkyl group. Examples of alkyl groups include linear or branched alkyl groups, and their number of carbon atoms may be, for example, 1 to 10, 1 to 5, 1 to 3, or a methyl group.

[0060] Specific examples of chelating agents include, for example, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'',N''-pentamethyldiethylenetriamine, and bis(2-dimethylaminoethyl) ether.

[0061] Alkali metal alkoxides are, for example, M(OR 9 It can be expressed as ). M is an alkali metal, and R 9 is an alkyl group. M is preferably sodium. That is, the alkali metal alkoxide is preferably a sodium alkoxide. 9 Examples include linear or branched alkyl groups, the number of carbon atoms may be, for example, 2 to 10, 2 to 8, or 3 to 6. Specific examples of alkali metal alkoxides include sodium tert-butoxide and sodium tert-amilate (NaOAm), with sodium tert-amilate being preferred.

[0062] The mixing ratio of the chelating agent to the alkali metal alkoxide (the molar ratio of chelating agent to alkali metal alkoxide is preferably 1.0 to 7.0, more preferably 1.0 to 6.5, and even more preferably 2.0 to 6.0) is preferred.

[0063] The chelating agent and alkali metal alkoxide may be added to the reaction solution from the beginning of the polymerization reaction of the block copolymer, or they may be added to the reaction solution during the polymerization reaction of the block copolymer (for example, after the formation of block A in step iA and before the formation of copolymer block B in step iB).

[0064] (Anionic polymerization) The block copolymer is preferably produced by anionic polymerization. That is, it is preferable that the copolymer block B is formed by anionic polymerization in a reaction solution containing a chelating agent and an alkali metal alkoxide. Furthermore, it is preferable that step iA includes anionic polymerization of aromatic vinyl hydrocarbon monomers to obtain block A containing aromatic vinyl hydrocarbon monomer units. It is preferable that step iB includes anionic polymerization of aromatic vinyl hydrocarbon monomers and conjugated diene monomers to obtain copolymer block B containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units. It is preferable that steps iA and iB are carried out consecutively.

[0065] As for anionic polymerization, a method in which each monomer is polymerized in an organic solvent using an organolithium compound as an initiator is preferred. When the anionic polymerization initiator is organolithium, the effects of adding chelating agents and alkali metal alkoxides, which will be described later, tend to be more pronounced. In so-called living anionic polymerization using an organolithium compound as an initiator, almost the entire amount of monomers subjected to the polymerization reaction can be converted into polymers.

[0066] Examples of organic solvents include hydrocarbon solvents. Examples of hydrocarbon 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.

[0067] 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.

[0068] The polymerization temperature for forming block A (step iA) is preferably 25 to 70°C, more preferably 30 to 65°C, and even more preferably 35 to 60°C.

[0069] The polymerization temperature for forming copolymer block B (step iB) is preferably 40 to 85°C, more preferably 50 to 85°C, and even more preferably 50 to 83°C. In one embodiment, the formation of copolymer block B is carried out in a hydrocarbon solvent, preferably in a temperature range of 50 to 85°C, and more preferably in a temperature range of 50 to 75°C, from the viewpoint of obtaining a block copolymer with a narrower molecular weight distribution.

[0070] In the anionic polymerization of block copolymers, the formation of block A and the formation of block B may be performed once or multiple times, depending on the desired block configuration.

[0071] Block copolymers obtained by anionic polymerization are 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 block copolymer from the resulting reaction solution, including (1) precipitation using a poor solvent such as methanol, (2) precipitation by evaporating the solvent using a heated roll or the like (drum dryer method), (3) a method of concentrating the solution with a concentrator and then removing the solvent with a vented extruder, or (4) a method of dispersing the solution in water, blowing in steam to heat and remove the solvent, and recovering the copolymer (steam stripping method).

[0072] [Application] The block copolymer according to this embodiment can provide a rubber composition with a higher glass transition temperature (Tg) when compounded with diene-based rubber, and can therefore be suitably used as a modifier for diene-based rubber, for example. Furthermore, since rubber compositions with a high glass transition temperature (Tg) have excellent wear resistance, they can also be applied to rubber compositions for manufacturing various parts of tires, such as the tread and sidewall portions of pneumatic tires for various applications and sizes, including passenger car tires and large tires for trucks and buses.

[0073] Examples of diene rubbers include natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), nitrile rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, and styrene-isoprene-butadiene copolymer rubber. The examples of each of the above diene rubbers include modified diene rubbers that have been modified with functional groups such as hydroxyl groups, amino groups, carboxyl groups, alkoxy groups, alkoxysilyl groups, and epoxy groups at their molecular ends or in their molecular chains.

[0074] The amount of block copolymer to be blended with diene rubber is not limited, but for example, it is preferably 0.1 to 50 parts by mass, more preferably 0.5 to 40 parts by mass, even more preferably 1.0 to 30 parts by mass, and particularly preferably 5.0 to 20 parts by mass per 100 parts by mass of diene rubber.

[0075] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of this disclosure are disclosed below. [1] A block copolymer comprising polymer block A containing vinyl aromatic monomer units and copolymer block B containing vinyl aromatic monomer units and conjugated diene monomer units, The total amount of 1,2-conjugates and 3,4-conjugates in the block copolymer is 30-90% of the total amount of conjugated diene monomer units. The content of conjugated diene monomer units in the total amount of the block copolymer is 5 to 30% by mass. A block copolymer in which the content of polymer block A in the total amount of the block copolymer is 30% by mass or less. [2] The block copolymer according to [1], wherein the molecular weight distribution Mw / Mn is 1.05 to 2.20. [3] The block copolymer according to [1] or [2], wherein the number average molecular weight Mn is 30,000 or less. [4] The block copolymer according to any one of [1] to [3], wherein the content of conjugated diene monomer units in the total amount of copolymer block B is 10 to 60% by mass. [5] The vinyl aromatic monomer unit comprises monomer units derived from one or more aromatic vinyl compounds selected from the group consisting of styrene, α-methylstyrene, and p-methylstyrene. The block copolymer according to any one of [1] to [6], wherein the conjugated diene monomer unit comprises monomer units derived from one or more conjugated dienes selected from the group consisting of 1,3-butadiene and isoprene. [6] A block copolymer according to any one of [1] to [5], wherein the element sodium is detected by any measurement selected from atomic absorption spectrometry, X-ray fluorescence spectrometry, and ICP emission spectrometry. A method for producing a block copolymer according to any one of [7], [1] to [6], The process involves forming copolymer block B in a reaction solution containing a chelating agent and an alkali metal alkoxide. A method for producing a block copolymer, wherein the ratio of the chelating agent to the alkali metal alkoxide in the reaction solution (chelating agent / alkali metal alkoxide) is 1.0 to 6.5 in molar ratio. [8] The method for producing a block copolymer according to [7], wherein the copolymer block B is formed in a hydrocarbon solvent in a temperature range of 50 to 85°C. Each configuration and its combination in each embodiment is an example, and additions, omissions, substitutions, and other modifications can be made as appropriate without departing from the spirit of this disclosure. This disclosure is not limited by the embodiments. [Examples]

[0076] The present disclosure will be further illustrated by the following examples, but these examples will not limit the interpretation of the present disclosure.

[0077] [Example 1] (1) Under a nitrogen atmosphere, 160 kg of cyclohexane, 28.8 g of tetrahydrofuran (THF), 1520 g of N,N,N',N'-tetramethylethylenediamine (TMEDA), and 242 g of sodium tert-amilate (NaOAm) were added to the reaction vessel. Next, 6170 mL of n-butyllithium / cyclohexane solution (10% by mass) was added as a polymerization initiator, and the internal temperature was maintained at 35°C.

[0078] (2) Next, while cooling the reaction vessel with water, 2.0 kg of styrene was added to the reaction vessel and the polymerization reaction was carried out. At this time, the internal temperature rose to a maximum of 36°C. (3) Next, after the styrene had been completely consumed, the internal temperature of the reaction vessel was lowered to 50°C, and 28.0 kg of styrene monomer and 8.0 kg of butadiene monomer were added simultaneously at constant addition rates of 70.0 kg / h and 20.0 kg / h, respectively, and this state was maintained for 10 minutes after the addition was completed. At this time, the internal temperature rose to a maximum of 60°C. (4) Next, after the styrene and butadiene had been completely consumed and the internal temperature had dropped to 50°C, 2.0 kg of styrene was added and the polymerization reaction was carried out. Subsequently, the polymerization active species were deactivated with water to obtain a polymerization solution containing the block copolymer. By pouring the resulting polymerization solution into an excess amount of methanol and allowing it to precipitate, a block copolymer 1 having polystyrene blocks - (styrene-butadiene random blocks) - polystyrene blocks was obtained.

[0079] [Example 2] (1) Under a nitrogen atmosphere, 160 kg of cyclohexane, 28.8 g of tetrahydrofuran (THF), 1670 g of N,N,N',N'-tetramethylethylenediamine (TMEDA), and 264 g of sodium tert-amilate (NaOAm) were added to the reaction vessel. Next, 6170 mL of n-butyllithium / cyclohexane solution (10% by mass) was added as a polymerization initiator, and the internal temperature was maintained at 35°C.

[0080] (2) Next, while cooling the reaction vessel with water, 2.0 kg of styrene was added to the reaction vessel and the polymerization reaction was carried out. At this time, the internal temperature rose to a maximum of 36°C. (3) Next, after the styrene had been completely consumed, the internal temperature of the reaction vessel was raised to 70°C, and 28.0 kg of styrene monomer and 8.0 kg of butadiene monomer were added simultaneously at constant addition rates of 70.0 kg / h and 20.0 kg / h, respectively, and this state was maintained for 10 minutes after the addition was completed. At this time, the internal temperature rose to a maximum of 72°C. (4) Next, after the styrene and butadiene had been completely consumed and the internal temperature had dropped to 50°C, 2.0 kg of styrene was added and the polymerization reaction was carried out. Subsequently, the polymerization active species were deactivated with water to obtain a polymerization solution containing the block copolymer. By pouring the resulting polymerization solution into an excess amount of methanol and allowing it to precipitate, a block copolymer 1 having polystyrene blocks - (styrene-butadiene random blocks) - polystyrene blocks was obtained.

[0081] [Example 3] (1) Under a nitrogen atmosphere, 160 kg of cyclohexane, 28.8 g of tetrahydrofuran (THF), 1520 g of N,N,N',N'-tetramethylethylenediamine (TMEDA), and 256 g of sodium tert-amilate (NaOAm) were added to the reaction vessel. Next, 5000 mL of n-butyllithium / cyclohexane solution (10% by mass) was added as a polymerization initiator, and the internal temperature was maintained at 30°C.

[0082] (2) Next, while cooling the reaction vessel with water, 2.0 kg of styrene was added to the reaction vessel and the polymerization reaction was carried out. At this time, the internal temperature rose to a maximum of 32°C. (3) Next, after the styrene had been completely consumed, the internal temperature of the reaction vessel was raised to 80°C, and 28.0 kg of styrene monomer and 8.0 kg of butadiene monomer were added simultaneously at constant addition rates of 70.0 kg / h and 20.0 kg / h, respectively, and this state was maintained for 10 minutes after the addition was completed. At this time, the internal temperature rose to a maximum of 82°C. (4) Next, after the styrene and butadiene had been completely consumed and the internal temperature had dropped to 50°C, 2.0 kg of styrene was added and the polymerization reaction was carried out. Subsequently, the polymerization active species were deactivated with water to obtain a polymerization solution containing the block copolymer. By pouring the obtained polymerization solution into an excess amount of methanol and allowing it to precipitate, a block copolymer 3 having polystyrene blocks - (styrene-butadiene random blocks) - polystyrene blocks was obtained.

[0083] [Comparative Example 1] (1) Under a nitrogen atmosphere, 160 kg of cyclohexane, 28.8 g of tetrahydrofuran (THF), 1616 g of N,N,N',N'-tetramethylethylenediamine (TMEDA), and 256 g of sodium tert-amilate (NaOAm) were added to the reaction vessel. Next, 5000 mL of n-butyllithium / cyclohexane solution (10% by mass) was added as a polymerization initiator, and the internal temperature was maintained at 30°C.

[0084] (2) Next, while cooling the reaction vessel with water, 16.0 kg of styrene was added to the reaction vessel and the polymerization reaction was carried out. At this time, the internal temperature rose to a maximum of 49°C. After the styrene was completely consumed, the internal temperature of the reaction vessel was lowered to 40°C, and an additional 14.0 kg of styrene was added and the polymerization reaction was carried out. At this time, the internal temperature rose to a maximum of 56°C. (3) Next, after the styrene had been completely consumed, the internal temperature of the reaction vessel was lowered to 40°C, and 8.0 kg of butadiene was added to carry out the polymerization reaction. At this time, the internal temperature rose to a maximum of 57°C. (4) Next, after the butadiene had been completely consumed and the internal temperature had dropped to 40°C, 2.0 kg of styrene was added to carry out the polymerization reaction. Subsequently, the polymerization active species were deactivated with water to obtain a polymerization solution containing the block copolymer. By pouring the obtained polymerization solution into an excess amount of methanol and allowing it to precipitate, a block copolymer 4 having polystyrene blocks, polybutadiene blocks, and polystyrene blocks was obtained.

[0085] [Comparative Example 2] (1) Under a nitrogen atmosphere, 160 kg of cyclohexane and 28.8 g of tetrahydrofuran (THF) were added to the reaction vessel. Next, 5000 mL of n-butyllithium / cyclohexane solution (10% by mass) was added as a polymerization initiator, and the internal temperature was maintained at 35°C.

[0086] (2) Next, while cooling the reaction vessel with water, 16.0 kg of styrene was added to the reaction vessel to raise the internal temperature to 60°C and carry out the polymerization reaction. At this time, the internal temperature rose to a maximum of 67°C. Next, after waiting for the internal temperature of the reaction vessel to drop to 50°C, an additional 14.0 kg of styrene was added and the polymerization reaction was carried out. At this time, the internal temperature rose to 73°C. (3) Next, after the styrene had been completely consumed, the internal temperature of the reaction vessel was allowed to drop to 50°C, and then 8.0 kg of butadiene was added to carry out the polymerization reaction. At this point, the internal temperature rose to 68°C. (4) Next, after the butadiene had been completely consumed and the internal temperature had dropped to 50°C, 2.0 kg of styrene was added and the polymerization reaction was carried out. Subsequently, the polymerization active species were deactivated with water to obtain a polymerization solution containing the block copolymer. By pouring the obtained polymerization solution into an excess amount of methanol and allowing it to precipitate, a block copolymer 5 having polystyrene blocks, polybutadiene blocks, and polystyrene blocks was obtained.

[0087] [measurement] The obtained block copolymers 1 to 5 were subjected to various physical and structural analyses using the following methods. The results are shown in Table 1.

[0088] <Content of butadiene monomer units> The content of butadiene monomer units was measured by nuclear magnetic resonance (NMR) under the following conditions. Observed nuclei: 1 H Observation frequency: 500.13MHz Pulse waiting time: 3.0 seconds Total number of times: 64 Solvent: Deuterated chloroform (CDCl3)

[0089] <Number-average molecular weight (Mn) and molecular weight distribution (Mw / Mn)> The number-average molecular weight and molecular weight distribution were measured using the GPC method under the following conditions. Device name: HLC-8220GPC (manufactured by Tosoh Corporation) Columns: Four ShodexGPCKF-404 (manufactured by Showa Denko) were connected in series. Temperature: 40℃ Detection: Ultraviolet-Vis spectroscopy (254 nm) Solvent: tetrahydrofuran Concentration: 2% by mass Calibration curve: Created using standard polystyrene (VARIAN).

[0090] <Content of 1,2-compounds> Proton nuclear magnetic resonance ( 1 Using 1H-NMR, the integral values ​​of the signals attributed to the 1,4-conjugate and the integral values ​​of the signals attributed to the 1,2-conjugate were determined. The proportion (mol%) of the 1,2-conjugate to the total amount (100 mol%) of the 1,4-conjugate and 1,2-conjugate was calculated, and this was used as the total amount of 1,2-conjugates in relation to the total amount of conjugated diene monomer units. 1 The conditions for 1H-NMR are the same as those for measuring the content of butadiene monomer units as described above.

[0091] <Glass transition temperature (Tg) of block copolymers> The glass transition temperature (Tg) of block copolymers 1, 4, and 5 obtained in Example 1 and Comparative Examples 1 and 2 was measured using a differential scanning calorimeter (TA Instruments Q2000). A 4 mg block copolymer sample was weighed into an aluminum pan and quenched under a nitrogen atmosphere by heating it to 120°C at a rate of 10°C / min, and then cooling it to 30°C. Subsequently, the temperature was increased to 150°C at a rate of 10°C / min, and the glass transition temperature (Tg) was determined from the inflection point of the resulting thermal analysis curve.

[0092] [Table 1]

[0093] [Reference example] Styrene-butadiene rubber (SBR) (manufactured by ENEOS Material, "ESBR1500") was prepared as the rubber component and used as a reference example.

[0094] [Measurement and Evaluation] Using a Toyo Seiki Laboplast Mill, 11 parts by mass of block copolymer 1 obtained in Example 1 were mixed with 100 parts by mass of SBR from Reference Example and kneaded at 100°C to obtain a rubber composition containing SBR and block copolymer 1 from Example 1. Similarly, rubber compositions containing block copolymer 4 from Comparative Example 1 and block copolymer 5 from Comparative Example 2 were obtained using these two materials, respectively.

[0095] <Glass transition temperature (Tg) of rubber compositions> The storage modulus (E') of the rubber composition containing the reference example SBR and the block copolymers of Example 1, Comparative Examples 1 and 2, as well as the reference example SBR, was measured according to the following procedure. Furthermore, the loss tangent value (tanδ) was calculated by dividing the simultaneously measured loss modulus (E”) by (E'). (1) A sheet with a thickness of 2 mm was prepared using a rubber composition or SBR, and strip-shaped test pieces were prepared by cutting the obtained sheet into a shape of 4 cm in length and 5 mm in width. (2) Using the RSA-GIII dynamic viscoelasticity analyzer manufactured by TA Instruments, E', E'', and tanδ were measured in the temperature range of -100 to 120°C under conditions of a heating rate of 4°C / min and a frequency of 1 Hz. From the results of each dynamic viscoelasticity measurement, the temperature at which the loss tangent (tanδ) peaked was read, and the glass transition temperature Tg was calculated. The difference between the calculated glass transition temperature Tg and the glass transition temperature Tg of the reference example SBR was calculated as the Tg increase. A sample was evaluated as "passing" if its glass transition temperature (Tg) was 2°C or more higher than that of the reference SBR sample, and as "failing" if its glass transition temperature (Tg) was higher than that of the reference SBR sample but the difference was less than 2°C. The results are shown in Table 2.

[0096] Figure 1 shows the results of dynamic viscoelasticity measurements performed in the temperature range of -60°C to -10°C for rubber compositions containing SBR and the block copolymers of Example 1, Comparative Examples 1 and 2, respectively, and for the SBR of the Reference Example, as described in (2) above. Figure 2 shows the results of the dynamic viscoelasticity measurements performed in the temperature range of -60°C to 120°C for the rubber composition containing SBR and the block copolymer of Example 1, and for the SBR of the Reference Example, as described in (2) above.

[0097] [Table 2]

[0098] As shown in Table 2 and Figure 1, the rubber composition containing block copolymer 1 of Example 1 has a glass transition temperature Tg that is 2°C or more higher than that of SBR alone. Furthermore, the rubber composition containing block copolymer 1 of Example 1 has a higher glass transition temperature Tg than the rubber compositions containing block copolymer 4 or 5 of Comparative Examples 1 and 2.

[0099] As shown in Examples 1-3 of Table 1, when polymer block B is formed in a hydrocarbon solvent at a temperature range of 50-80°C, the content of 1,2-bonds in the conjugated diene monomer units tends to increase.

[0100] Referring to Table 1 and Figure 2, the compatibility of block copolymers with diene rubbers can be examined. Since block copolymer 1 has a glass transition temperature Tg of 47°C, if it is incompatible with diene rubber (SBR) when compounded with diene rubber, peaks should be observed around 47°C in the dynamic viscoelasticity measurement of the rubber composition. However, as shown in Figure 2, the rubber composition containing block copolymer 1 in Example 1 does not show any peaks originating from block copolymer 1 on the high temperature side above 0°C in the dynamic viscoelasticity measurement. Therefore, it can be seen that block copolymer 1 has good compatibility with rubber components such as SBR. [Industrial applicability]

[0101] The block copolymer of this embodiment can be suitably used in various packaging materials, adhesive materials, resin modifiers, etc., and is particularly suitable as a modifier for diene rubbers, thus possessing industrial applicability.

Claims

1. This is a block copolymer comprising polymer block A containing vinyl aromatic monomer units and copolymer block B containing vinyl aromatic monomer units and conjugated diene monomer units. The total amount of 1,2-conjugates and 3,4-conjugates in the block copolymer is 30-90% of the total amount of conjugated diene monomer units. The content of conjugated diene monomer units in the total amount of the block copolymer is 5 to 30% by mass. A block copolymer in which the content of polymer block A in the total amount of the block copolymer is 30% by mass or less.

2. The block copolymer according to claim 1, wherein the molecular weight distribution Mw / Mn is 1.05 to 2.

20.

3. The block copolymer according to claim 1 or 2, wherein the number average molecular weight Mn is 30,000 or less.

4. The block copolymer according to claim 1 or 2, wherein the content of conjugated diene monomer units in the total amount of copolymer block B is 10 to 60% by mass.

5. The vinyl aromatic monomer unit comprises monomer units derived from one or more aromatic vinyl compounds selected from the group consisting of styrene, α-methylstyrene, and p-methylstyrene. The block copolymer according to claim 1 or 2, wherein the conjugated diene monomer unit comprises monomer units derived from one or more conjugated dienes selected from the group consisting of 1,3-butadiene and isoprene.

6. The block copolymer according to claim 1 or 2, wherein the element sodium is detected in any measurement selected from atomic absorption spectrometry, X-ray fluorescence spectrometry, and ICP emission spectrometry.

7. A method for producing a block copolymer according to claim 1 or 2, The process involves forming copolymer block B in a reaction solution containing a chelating agent and an alkali metal alkoxide. A method for producing a block copolymer, wherein the ratio of the chelating agent to the alkali metal alkoxide in the reaction solution (chelating agent / alkali metal alkoxide) is 1.0 to 6.5 in molar ratio.

8. The method for producing a block copolymer according to claim 7, wherein the copolymer block B is formed in a hydrocarbon solvent in a temperature range of 50 to 85°C.

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