Tire rubber composition and method for producing same

Abstract

Provided are: a tire rubber composition having a glass transition temperature Tg higher than that of conventional ones; and a method for producing the same.　The present invention provides a tire rubber composition comprising a rubber component I and a block copolymer II which contains a vinyl aromatic hydrocarbon monomer unit and a conjugated diene monomer unit.　The present invention provides a method for producing a tire rubber composition, in which in a step (i) for obtaining the block copolymer II, a step (i-B) for forming a conjugated diene monomer unit-containing block B is performed in the presence of a chelating agent and an alkali metal alkoxide.

Description

Rubber composition for tires, and method for manufacturing the same.

[0001] The present invention relates to a rubber composition for tires and a method for producing the same.

[0002] Conventional tire compositions consist of a rubber component such as styrene-butadiene rubber (SBR) blended with reinforcing fillers, and are vulcanized to impart the desired rubber elasticity and strength. In recent years, wear resistance has become one of the properties required for automobile tires. In particular, electric vehicles (EVs) tend to experience faster tire wear compared to conventional gasoline vehicles due to the increased vehicle weight. As a technology to improve wear resistance, for example, there are rubber compositions containing a styrene-butadiene copolymer having a predetermined structure and a filler (for example, Patent Document 1, etc.).

[0003] Japanese Patent Publication No. 2017-203085

[0004] Patent Document 1 describes a method for improving the composition of styrene monomer units and butadiene monomer units in rubber components such as styrene-butadiene rubber. On the other hand, the present inventors have conducted extensive research on block copolymers containing monomer units derived from aromatic vinyl hydrocarbons and monomer units derived from conjugated diene monomers. Such block copolymers have elasticity at room temperature similar to vulcanized natural rubber and synthetic rubber without vulcanization, and have processability similar to thermoplastic resins at high temperatures, and are therefore used in a wide range of fields such as various packaging materials, adhesive materials, and resin modifiers. The present inventors focused on the fact that the above block copolymer has a monomer structure similar to SBR, and that those containing a large amount of styrene have a higher glass transition temperature Tg than natural rubber and synthetic rubber. The inventors then concluded that by incorporating the above block copolymer into the rubber component for tires, the glass transition temperature Tg of the rubber composition can be improved, thereby increasing the wear resistance of tires, and thus completed the present invention.

[0005] The object of this disclosure is to provide a rubber composition for tires having a higher glass transition temperature Tg than conventional rubber compositions, and a method for producing the same.

[0006] The present disclosure includes the following aspects. [1] A rubber composition for tires, comprising a rubber component I and a block copolymer II containing an aromatic vinyl hydrocarbon monomer unit and a conjugated diene monomer unit. [2] A method for producing the rubber composition for tires according to [1], which includes (i) obtaining a block copolymer II containing an aromatic vinyl hydrocarbon monomer unit and a conjugated diene monomer unit by using an aromatic vinyl hydrocarbon monomer and a conjugated diene monomer, and (ii) blending the block copolymer II with the rubber component I. The step (i) of obtaining the block copolymer II includes (i-A) forming a block A containing an aromatic vinyl hydrocarbon monomer unit by using an aromatic vinyl hydrocarbon monomer, and (i-B) forming at least one conjugated diene monomer unit-containing block B selected from a block B-1 containing a conjugated diene monomer unit and a block B-2 containing an aromatic vinyl hydrocarbon monomer unit and a conjugated diene monomer unit by using an aromatic vinyl hydrocarbon monomer and / or a conjugated diene monomer. The step (i-B) of forming the conjugated diene monomer unit-containing block B is carried out in the presence of a chelating agent and an alkali metal alkoxide.

[0007] According to the present disclosure, it is possible to provide a rubber composition for tires having a higher glass transition temperature Tg than before, and a method for producing the same.

[0008] FIGS. 1(a) to (c) are charts showing the results in the temperature range of -60°C to -10°C among the results of dynamic viscoelasticity measurement at a frequency of 1 Hz of the rubber compositions for tires of Examples 1 to 3 and the rubber component (SBR) of Comparative Example 1. FIGS. 2(a) and (b) are charts showing the results in the temperature range of -60°C to 120°C among the results of dynamic viscoelasticity measurement at a frequency of 1 Hz of the rubber compositions for tires of Examples 1 and 2 and the rubber component (SBR) of Comparative Example 1.

[0009] One embodiment of this disclosure will be described in detail below, but the scope of this disclosure is not limited to the embodiment described herein, and various modifications can be made without departing from the spirit of this 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. If multiple numerical ranges are given for multiple parameters, any numerical range can be adopted for each parameter and combined as desired. The expression "X to 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] [Rubber Composition for Tires] The rubber composition for tires according to this disclosure (hereinafter also simply referred to as "rubber composition") comprises rubber component I and block copolymer II (hereinafter also simply referred to as "block copolymer II") containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units. "For tires" means used in the manufacture of tires. By including block copolymer II containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units, a rubber composition having a higher glass transition temperature Tg than conventional rubber compositions using only known rubber components can be obtained. As confirmed in the examples described later, rubber component I and block copolymer II were found to have excellent compatibility. Because rubber component I and block copolymer II have excellent compatibility, the glass transition temperature Tg of the rubber composition as a whole is increased.

[0011] <Rubber Component I> As the rubber component I, a diene rubber is preferred, and a rubber mainly containing diene monomer units is more preferred. "Mainly containing" means that it is contained in an amount exceeding 50% by mass in the total amount (100% by mass) of the rubber component I, preferably 55 to 100% by mass, more preferably 60 to 90% by mass, and may be 65 to 85% by mass or 70 to 80% by mass.

[0012] Examples of the diene rubber 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, styrene-isoprene-butadiene copolymer rubber, etc. The exemplified diene rubbers above include modified diene rubbers modified with functional groups such as hydroxyl group, amino group, carboxyl group, alkoxy group, alkoxysilyl group, and epoxy group at their molecular terminals or in their molecular chains. The rubber component I can be used alone or in combination of two or more.

[0013] Among these, it is preferable to contain at least one rubber selected from the group consisting of IR, BR, and SBR, and it is more preferable to contain SBR from the viewpoint of being more likely to have higher compatibility with the block copolymer II described later. There is no particular limitation on SBR, and examples include solution polymerization SBR (S-SBR), emulsion polymerization SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). As SBR, oil-extended SBR can be used, or non-oil-extended SBR can be used.

[0014] The glass transition temperature Tg of rubber component I is preferably -70°C to 0°C, more preferably -65°C to -10°C, even more preferably -60°C to -20°C, even more preferably -55°C to -25°C, and particularly preferably -50°C to -30°C. When the glass transition temperature is 0°C or lower, it is easier to suppress the deterioration of the tire's low-temperature performance. When the glass transition temperature is -70°C or higher, it is easier to obtain an improvement in the tire's wet grip performance. The glass transition temperature Tg may be the value in the manufacturer's catalog. Alternatively, it may be measured by performing dynamic viscoelasticity measurements at a heating rate of 4°C / min and a frequency of 1 Hz, measuring E', E'', and tanδ in the temperature range of -100 to 120°C, and reading the temperature at which the loss tangent value (tanδ) shows a peak.

[0015] When rubber component I includes rubber containing styrene monomer units (e.g., SBR), the content of styrene monomer units in rubber component I is preferably less than 50% by mass, more preferably 5 to 45% by mass, and even more preferably 10 to 40% by mass, based on the total amount of rubber component I (100% by mass). When the content of styrene monomer units in rubber component I is less than 50% by mass, a good balance of strength, elasticity, low-temperature performance, etc., tends to be achieved. The content of styrene monomer units in rubber component I is: １ It can be calculated by H-NMR measurement.

[0016] The content of rubber component I in the rubber composition is preferably 30 to 95% by mass, more preferably 50 to 93% by mass, and even more preferably 55 to 90% by mass, based on the total amount (100% by mass) of the rubber composition.

[0017] <Block Copolymer II> Block copolymer II 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.

[0018] The content of block copolymer II 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 rubber component I. When the content of block copolymer II is 0.1 to 50 parts by mass per 100 parts by mass of rubber component I, the glass transition temperature Tg of the rubber composition tends to be higher.

[0019] (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.

[0020] Aromatic vinyl hydrocarbon monomers may be compounds having, for example, 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 -CH=CH ２ This is the group represented by . The vinylidene group attached to the aromatic ring is, for example, -CR=CH ２ The group may be represented by (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.

[0021] Examples of the aromatic vinyl hydrocarbon monomer include styrene-based compounds such as styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, and α-methylstyrene; vinyl naphthalene; vinyl anthracene; and the like. In one embodiment, from the viewpoint of excellent compatibility with the rubber component I, the aromatic vinyl hydrocarbon monomer preferably contains one or more styrene-based compounds selected from the group consisting of styrene, o-methylstyrene, and p-methylstyrene, and more preferably contains styrene. The aromatic vinyl hydrocarbon monomer may be used alone or in combination of two or more.

[0022] The aromatic vinyl hydrocarbon monomer unit may be, for example, a structural unit represented by the following formula (A-1): In the formula (A-1), R １ represents a hydrogen atom or an alkyl group, and Ar １ represents an aryl group. The carbon number of the alkyl group in R １ may be, for example, 1 to 10, may be 1 to 5, or may be 1. R １ may be, for example, a methyl group. Examples of the aryl group in Ar １ include a phenyl group which may have a substituent, a naphthyl group which may have a substituent, and the like. Examples of the substituent include an alkyl group, an alkoxy group, a halogeno group (for example, a fluoro group, a chloro group, a bromo group, an iodo group), and the like. Ar １ may be, for example, a phenyl group, a 4-methylphenyl group, a 2,4-dimethylphenyl group, or a 2,5-dimethylphenyl group, or may be a phenyl group or a 4-methylphenyl group.

[0023] In one embodiment, the content of aromatic vinyl hydrocarbon monomer units in the total monomer units (100% by mass) of block copolymer II 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. When the content of aromatic vinyl hydrocarbon monomer units is 50 to 95% by mass, the glass transition temperature Tg of the rubber composition tends to be higher. The content of aromatic vinyl hydrocarbon monomer units in the total monomer units of block copolymer II can be calculated, for example, from the mass of aromatic vinyl hydrocarbon monomers used during the polymerization of block copolymer II. Furthermore, １ It can also be calculated by H-NMR measurement.

[0024] (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.

[0025] In one embodiment, the conjugated diene monomer unit may have 1,4-conjugates, 1,2-conjugates, and 3,4-conjugates. The 1,4-conjugate is a structure formed by polymerizing the carbon atoms at positions 1 and 4 of the conjugated diene skeleton so as to bond with adjacent monomer units, and has a carbon-carbon double bond in the main chain. In contrast, the 1,2-conjugate (or 3,4-conjugate) is a structure formed by polymerizing the carbon atoms at positions 1 and 2 (or 3 and 4) of the conjugated diene skeleton so as to bond with adjacent monomer units, and has a carbon-carbon double bond in the side chain.

[0026] In one embodiment, the conjugated diene monomer unit preferably includes at least one conjugate selected from 1,2-conjugates and 3,4-conjugates. Including at least one conjugate selected from 1,2-conjugates and 3,4-conjugates makes it easier for the glass transition temperature Tg of the rubber composition to be higher. Furthermore, when the rubber composition is vulcanized by a crosslinking reaction, the carbon-carbon double bonds in the side chains of block copolymer II can also act as crosslinking reaction sites, making it easier for the crosslink density of the rubber composition to be higher. For example, in a vulcanized product of a rubber composition containing rubber component I and block copolymer II, a network structure is formed by the carbon-carbon double bonds of rubber component I and the carbon-carbon double bonds of the main chain of block copolymer II, and the carbon-carbon double bonds of the side chains of block copolymer II can act as crosslinking reaction sites to further form a crosslinked structure, making it easier for the crosslink density to be higher. Rubber compositions with a high glass transition temperature Tg and high crosslink density tend to have better abrasion resistance.

[0027] In one embodiment, the conjugated diene monomer unit is, for example, the following formula (B-i), formula (B-ii), and formula (B-iii): It is preferable that the constituent units represented by include one or more units selected from the constituent units represented by formula (B-ii) and formula (B-iiii), and it is also preferable that each constituent unit represented by formula (B-i) is included. The constituent unit represented by formula (B-i) is a 1,4-compound, the constituent unit represented by formula (B-ii) is a 1,2-compound, and the constituent unit represented by formula (B-iiii) is a 3,4-compound. In formulas (B-i), (B-ii), and (B-iiii), R ２ａ , R ２ｂ , R ２ｃ Each of these independently represents either a hydrogen atom or an alkyl group. ２ｂ When is a hydrogen atom, formulas (B-ii) and (B-iii) represent the same constituent unit. ２ａ , R ２ｂ , R ２ｃ The number of carbon atoms in the alkyl group may be, for example, 1 to 10, 1 to 5, or 1. ２ This could be, for example, a methyl group.

[0028] In one embodiment, the total amount of 1,2-conjugates and 3,4-conjugates in the total amount (100 mol%) of conjugated diene monomer units in block copolymer II is preferably 90 mol% or less. When the total amount of 1,2-conjugates and 3,4-conjugates in the total amount (100 mol%) of conjugated diene monomer units in block copolymer II is 90 mol% or less, the Tg of the polymer block containing the conjugated diene monomers tends to improve. From the viewpoint of making it easier for the glass transition temperature Tg of the rubber composition to be higher, the total amount of 1,2-conjugates and 3,4-conjugates is preferably 10 to 90 mol%, more preferably 20 to 90 mol%, even more preferably 50 to 85 mol%, even more preferably 60 to 80 mol%, and particularly preferably 65 to 75 mol%. The content of 1,2-conjugates and 3,4-conjugates in the total amount (100 mol%) of conjugated diene monomer units in block copolymer II is １ It can be calculated by H-NMR measurement.

[0029] 1,2- and 3,4-conjugates are readily formed during the polymerization of block copolymer II by polymerizing the block containing conjugated diene monomer units in the presence of a chelating agent and an alkali metal alkoxide. By appropriately selecting the type of alkali metal ion contained in the alkali metal alkoxide, the content of 1,2- and 3,4-conjugates in the total amount of conjugated diene monomer units in block copolymer II can be easily adjusted. For example, sodium ions (Na) can be used as alkali metal ions. ＋ If ) is selected, lithium ion (Li ＋ Compared to the case where ( ) is used, the content of 1,2-conjugates and 3,4-conjugates is increased. Furthermore, the ratio of 1,2-conjugates and 3,4-conjugates can be controlled by adjusting the polymerization temperature. For example, as the polymerization temperature increases, the content of 1,2-conjugates and 3,4-conjugates tends to decrease, so if you want to increase the ratio of 1,2-conjugates and 3,4-conjugates, it is preferable to lower the polymerization temperature.

[0030] In one embodiment, the content of conjugated diene monomer units in the total monomer units (100% by mass) of block copolymer II is preferably 5 to 50% by mass, more preferably 5 to 40% by mass, even more preferably 5 to 30% by mass, and particularly preferably 10 to 25% by mass. When the content of conjugated diene monomer units is 5 to 50% by mass, the glass transition temperature Tg of the rubber composition tends to be higher. The content of conjugated diene monomer units in the total monomer units of block copolymer II can be calculated, for example, from the mass of conjugated diene monomers used during the polymerization of block copolymer II. In addition, halogen addition methods and １ It can also be calculated by H-NMR measurement.

[0031] (Primary structure (block structure)) Block copolymer II preferably comprises one or more conjugated diene monomer unit-containing blocks B (hereinafter also simply referred to as "conjugated diene monomer unit-containing blocks B") selected from Block A (hereinafter also simply referred to as "block A") which comprises aromatic vinyl hydrocarbon monomer units, Block B-1 (hereinafter also simply referred to as "block B-1") which comprises conjugated diene monomer units, and Block B-2 (hereinafter also simply referred to as "block B-2") which comprises aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units. By comprising (1) Block A and (2) conjugated diene monomer unit-containing blocks B, it is easier to obtain a rubber composition having a higher glass transition temperature Tg than conventional rubber compositions.

[0032] In this specification, the content of each block in block copolymer II 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 block copolymer II. 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 in the total mass of monomers used in the polymerization of each block. １ It can also be calculated by H-NMR measurement.

[0033] (Block A) Block A is a block mainly containing aromatic vinyl hydrocarbon monomer units, for example, 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 the total monomer 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 the total monomer units in block A. In one embodiment, block A may consist only of aromatic vinyl hydrocarbon monomers. By including block A in block copolymer II, it is easier to obtain a rubber composition having a higher glass transition temperature Tg than conventional rubber compositions.

[0034] Block copolymer II may contain one block A, or two or more. In one embodiment, it is preferable that block copolymer II has block A at both ends of its molecular chain. When block copolymer II contains two or more block A, the two or more block A may be identical, or it may contain two or more types of block A that differ in the type and / or content of aromatic vinyl hydrocarbon monomers.

[0035] 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.

[0036] The size of one block A is not limited and may be 1 to 80% by mass, 1 to 50% by mass, or 1 to 30% by mass of the total monomer units (100% by mass) of the block copolymer II. In one embodiment, from the viewpoint of making it easier to raise the glass transition temperature Tg of the rubber composition, the size of one block A is preferably 1 to 20% by mass, more preferably 1 to 15% by mass, and even more preferably 1 to 10% by mass, of the total monomer units (100% by mass) of the block copolymer II.

[0037] From the viewpoint of making it easier to raise the glass transition temperature Tg of the rubber composition, the total amount of block A in block copolymer II is preferably 1 to 45% by mass, more preferably 3 to 30% by mass, and even more preferably 5 to 20% by mass, relative to the total monomer units (100% by mass) of block copolymer II.

[0038] (Block B containing conjugated diene monomer units) Block B containing conjugated diene monomer units comprises one or more selected from Block B-1 containing conjugated diene monomer units and Block B-2 containing aromatic vinyl hydrocarbon monomer units and the aforementioned conjugated diene monomer units.

[0039] (Block B-1) Block B-1 is a block mainly containing conjugated diene monomer units, for example, a polymer block of conjugated diene monomers. The conjugated diene monomer units are as described above. The content of conjugated diene monomer units in block B-1 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, in the total monomer units of block B-1. In one embodiment, block B-1 may consist only of conjugated diene monomer units. The inclusion of block B-1 in block copolymer II makes it easier to form a high-density crosslinked structure during vulcanization of the rubber composition. This makes it easier to achieve higher abrasion resistance. Block copolymer II may contain one block B-1, or two or more. If block copolymer II contains two or more block B-1s, these two or more block B-1s may be identical, or they may contain two or more block B-1s that differ in the type and / or content of the conjugated diene monomer.

[0040] Block B-1 may contain monomer units (b) derived from monomers that can copolymerize with conjugated diene monomers. Examples of such monomer units (b) include ethylene, propylene, vinyl chloride, vinyl acetate, (meth)acrylic acid, alkyl (meth)acrylate, (meth)acrylamide, (meth)acrylonitrile, aromatic vinyl hydrocarbons, and the like.

[0041] The size of a single block B-1 is not limited, but from the viewpoint of making it easier to increase the crosslinking density in the vulcanized rubber composition, it is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, and even more preferably 10 to 30% by mass, of the total monomer units (100% by mass) of the block copolymer II.

[0042] The total amount of block B-1 in block copolymer II is preferably 0 to 50% by mass, more preferably 5 to 40% by mass, and even more preferably 10 to 30% by mass, relative to the total monomer units (100% by mass) of block copolymer II.

[0043] (Block B-2) Block B-2 is a block containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units, for example, a copolymer block of aromatic vinyl hydrocarbon monomers and conjugated diene monomers. 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. When aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units are added simultaneously during the polymerization of block B-2, a tapered block is easily formed, and when 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 block B-2 in block copolymer II makes it easier for the compatibility with rubber component (I) to be increased, which in turn makes it easier for the glass transition temperature Tg of the rubber composition to be increased. As a result, the abrasion resistance is easily increased.

[0044] The aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units are as described above. The aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units contained in Block B-2 may be the same as or different from the aromatic vinyl hydrocarbon monomer units contained in Block A and the conjugated diene monomer units contained in Block B-1. 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.

[0045] Block copolymer II may contain one block B-2, or two or more. When block copolymer II contains two or more blocks B-2, these two or more blocks B-2 may be identical, have different block structures such as random blocks or tapered blocks, or contain two or more types of blocks B-2 with different types and / or content of aromatic vinyl hydrocarbon monomers and / or conjugated diene monomers. In one embodiment, from the viewpoint of making it easier to raise the glass transition temperature Tg of the rubber composition, it is preferable that the conjugated diene monomer unit-containing block B contains at least one block B-2.

[0046] From the viewpoint of making it easier to achieve a higher glass transition temperature Tg of the rubber composition, the content of aromatic vinyl hydrocarbon monomer units in one block B-2 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 monomer units (100% by mass) of one block B-2. From the viewpoint of making it easier to achieve a higher glass transition temperature Tg of the rubber composition, the total content of aromatic vinyl hydrocarbon monomer units in block B-2 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 monomer units (100% by mass) of block B-2.

[0047] From the viewpoint of making it easier to raise the glass transition temperature Tg of the rubber composition, the content of conjugated diene monomer units in one block B-2 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 monomer units (100% by mass) of one block B-2. From the viewpoint of making it easier to raise the glass transition temperature Tg of the rubber composition, the total content of conjugated diene monomer units in block B-2 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 monomer units (100% by mass) of block B-2.

[0048] The size of one block B-2 is not limited, but from the viewpoint of making it easier to increase the crosslinking density in the vulcanized rubber composition, it 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 monomer units (100% by mass) of the block copolymer II.

[0049] From the viewpoint of making it easier to improve compatibility with rubber component (I) and thereby make it easier to raise the glass transition temperature Tg, the total amount of block B-2 in block copolymer II 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 monomer units (100% by mass) of block copolymer II.

[0050] The total amount of block B in block copolymer II (the total amount of block B-1 and block B-2) is preferably 55 to 99% by mass, more preferably 70 to 98% by mass, and even more preferably 80 to 95% by mass, of the total monomer units (100% by mass) of block copolymer II, from the viewpoint of making it easier to increase compatibility with rubber component (I) and thereby make it easier to raise the glass transition temperature Tg, and from the viewpoint of making it easier to form a high-density crosslinked structure during vulcanization of the rubber composition.

[0051] (Block Structure) Block copolymer II 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) ｎFormula 3 In Formulas 1 to 3, (A) represents polymer block A containing aromatic vinyl hydrocarbon monomer units, and (B) represents copolymer block B containing conjugated diene monomer units. Preferably, (B) is one or more conjugated diene monomer unit-containing blocks B selected from block B-1 containing conjugated diene monomer units and block B-2 containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units. In Formulas 1 to 3, l, m, and n each independently represent an integer of 1 or more for each formula, preferably an integer 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 the case where l, m, and n are 1 by the type and / or content of the 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 formula 2, the types and / or contents of aromatic vinyl hydrocarbon monomers in the two blocks A may be the same or different. In formula 3, the types and / or contents of conjugated diene monomers in the two blocks B may be the same or different, and the block structures may be the same or different. In one embodiment, from the viewpoint of making it easier to increase the glass transition temperature Tg of the rubber composition, it is preferable that the block copolymer II contains the structure represented by formula 2.

[0052] In one embodiment, when the block copolymer II 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-1) ｍ - (A) ｎ Formula 2-1 (A) ｌ - (B-2) ｍ - (A) ｎ Formula 2-2 (A) ｌ - (B-1) ｍ - (B-2) ｎ - (A) ｏ Formula 2-3 (A) ｌ - (B-2)ｍ - (B-1) ｎ - (B-2) ｏ - (A) ｐ Formula 2-4 (A) ｌ - (B-1) ｍ - (B-2) ｎ - (B-1) ｏ - (A) ｐ Formula 2-5 (A) ｌ - (B-1) ｍ - (B-2) ｎ - (B-1) ｏ - (B-2) ｐ - (A) ｑ Formula 2-6 In formulas 2-1 to 2-6, (B-1) represents block B-1 containing conjugated diene monomer units, and (B-2) represents block B-2 containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units. l, m, n, o, p, q each independently represent an integer of 1 or more for each formula, preferably an integer from 1 to 3, more preferably 1 or 2, and even more preferably 1. When l, m, n, o, p, q are integers of 2 or more, adjacent blocks can be distinguished from the case where l, m, n, o, p, q are 1 by the difference in the types and / or content of the monomers contained, or by the difference in the content of the 1,2-conjugates and 3,4-conjugates contained. In formulas 2-4 and 2-6, the two blocks B-2 may have the same or different types and / or content of aromatic vinyl hydrocarbon monomers and / or conjugated diene monomers, and the content of 1,2-conjugates and 3,4-conjugates may be the same or different. In formulas 2-5 and 2-6, the two blocks B-1 may have the same or different types and / or content of conjugated diene monomers, and the content of 1,2-conjugates and 3,4-conjugates may be the same or different. In one embodiment, block copolymer II preferably includes the structure represented by formula 2-1 and / or the structure represented by formula 2-2, and more preferably includes the structure represented by formula 2-2. The structure of block copolymer II is, １ H-NMR and １３It can be measured by 13C-NMR, ozonolysis GPC, etc. Block copolymer II may have a structure in which two or more structures selected from formulas 1 to 3 and formulas 2-1 to 2-6 are linked together by a coupling agent. Block copolymer II in which the structures of formulas 1 to 3 and formulas 2-1 to 2-6 are linked 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.

[0053] The block copolymer II 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 25,000, even more preferably 6,000 to 23,000, and particularly preferably 7,000 to 20,000. In one embodiment, the number average molecular weight Mn of the block copolymer II is preferably 6,000 to 10,000. When the number average molecular weight Mn of the block copolymer II is 30,000 or less, the compatibility with rubber component I tends to be higher, which in turn tends to raise the glass transition temperature Tg of the rubber composition. The number average molecular weight Mn can be measured, for example, using gel permeation chromatography (GPC).

[0054] The molecular weight distribution (Mw / Mn) of block copolymer II is preferably 3 or less, more preferably 1.00 to 2.50, more preferably 1.05 to 2.30, even more preferably 1.10 to 2.00, and particularly preferably 1.20 to 1.80. The molecular weight distribution (Mw / Mn) can be measured, for example, using gel permeation chromatography (GPC).

[0055] The glass transition temperature Tg of block copolymer II 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 block copolymer II is 0 to 100°C, the glass transition temperature Tg of the rubber composition tends to be higher. The glass transition temperature Tg of block copolymer II can be calculated from the inflection point of the thermal analysis curve obtained by measurement using differential scanning calorimeter (DSC).

[0056] (Method for producing block copolymer II) The method for producing block copolymer II according to this embodiment includes: (i-A): forming block A containing aromatic vinyl hydrocarbon monomer units using aromatic vinyl hydrocarbon monomers (hereinafter also simply referred to as "step i-A"), and (i-B): forming one or more conjugated diene monomer unit-containing block B selected from block B-1 containing conjugated diene monomer units and block B-2 containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units using aromatic vinyl hydrocarbon monomers and / or conjugated diene monomers (hereinafter also simply referred to as "step i-B"), wherein (i-B) forming conjugated diene monomer unit-containing block B is carried out in the presence of a chelating agent and an alkali metal alkoxide.

[0057] By forming (i-B) conjugated diene monomer unit-containing block B in the presence of a chelating agent and an alkali metal alkoxide, block copolymer II is easily obtained, which has excellent compatibility with rubber component I and, when compounded with rubber component I, gives a tire rubber composition having a higher glass transition temperature Tg than conventional materials.

[0058] (Anionic Polymerization) Block copolymer II is preferably produced by anionic polymerization. Specifically, step i-A preferably includes anionic polymerization of aromatic vinyl hydrocarbon monomers. Step i-B preferably includes anionic polymerization of conjugated diene monomers to obtain block B-1 containing conjugated diene monomer units (hereinafter also referred to as "step i-B-1"), and / or anionic polymerization of aromatic vinyl hydrocarbon monomers and conjugated diene monomers to obtain block B-2 containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units (hereinafter also referred to as "step i-B-2"). Steps i-A and i-B are preferably carried out consecutively.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] The polymerization temperature for forming block A (step i-A) is preferably 25 to 70°C, more preferably 30 to 65°C, and even more preferably 35 to 60°C.

[0063] The polymerization temperature for forming copolymer block B (step i-B) 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 even 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.

[0064] In the anionic polymerization of block copolymer II, the formation of block A and the formation of block B may be performed once or multiple times, depending on the desired block configuration.

[0065] Block copolymer II obtained by anionic polymerization 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 block copolymer II 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).

[0066] (Chelating agent and alkali metal alkoxide) In the method for producing block copolymer II according to this embodiment, step i-B is carried out in the presence of a chelating agent and an alkali metal alkoxide. In one embodiment, it is preferable that the following steps are carried out in the presence of a chelating agent and an alkali metal alkoxide: anionic polymerization of a conjugated diene monomer to obtain block B-1 containing conjugated diene monomer units (step i-B-1), and / or anionic polymerization of an aromatic vinyl hydrocarbon monomer and a conjugated diene monomer to obtain block B-2 containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units (step i-B-2).

[0067] 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.

[0068] The chelating agent can be any chelating agent capable of coordinating to a cation derived from the anionic polymerization initiator (e.g., a lithium cation). 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. In one embodiment, the chelating agent is, for example, the following formula (I): The compound may be represented by formula (I). In formula (I), n and m each independently represent an integer from 0 to 3, preferably 0 or 1, and R ３ is a single bond, -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, for example, a methyl group.

[0069] Specific examples of chelating agents include, for example, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'',N''-pentamethyldiethylenetriamine, and bis(2-dimethylaminoethyl) ether.

[0070] Alkali metal alkoxides are, for example, M(OR ９ It can be expressed as ). M is an alkali metal, and R ９ R 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 being, 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.

[0071] 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.

[0072] The chelating agent and alkali metal alkoxide may be added to the reaction solution from the beginning of the polymerization reaction of block copolymer II, or they may be added to the reaction solution during the polymerization reaction of block copolymer II (for example, after the formation of block A by step i-A and before the formation of block B by step i-B).

[0073] <Other Additives> In addition to rubber component I and block copolymer II, the rubber composition may contain various additives commonly used in rubber compositions, such as reinforcing fillers, silane coupling agents, oils, zinc oxide, stearic acid, antioxidants, waxes, vulcanizing agents, and vulcanization accelerators. Examples of reinforcing fillers include silica such as wet silica (hydrated silica) and carbon black. Sulfur is preferably used as the vulcanizing agent. Examples of vulcanization accelerators include various vulcanization accelerators such as sulfenamide-based, thiuram-based, thiazole-based, and guanidine-based accelerators, which can be used individually or in combination of two or more.

[0074] The rubber composition has a higher glass transition temperature Tg than rubber component I. In one embodiment, the glass transition temperature Tg of the rubber composition is preferably 0.5°C or higher, more preferably 1.0°C or higher, and even more preferably 2.0°C or higher than the glass transition temperature Tg of rubber component I. The glass transition temperature Tg of the rubber composition can be measured by performing dynamic viscoelasticity measurements at a heating rate of 4°C / min and a frequency of 1 Hz, measuring E', E'', and tanδ in the temperature range of -100 to 120°C, and reading the temperature at which the loss tangent value (tanδ) shows a peak.

[0075] <Applications> The tire rubber composition according to this embodiment can be applied to various parts of tires, such as the tread and sidewall, of pneumatic tires of various uses and sizes, including passenger car tires and large tires for trucks and buses.

[0076] [Method for producing a rubber composition for tires] The method for producing a rubber composition for tires according to this embodiment includes (i) obtaining a block copolymer II containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units using an aromatic vinyl hydrocarbon monomer and a conjugated diene monomer, and (ii) blending the block copolymer II with rubber component I.

[0077] <Step (i)> (i) Obtaining block copolymer II includes (i-A) forming block A containing aromatic vinyl hydrocarbon monomer units using aromatic vinyl hydrocarbon monomers, and (i-B) forming one or more conjugated diene monomer unit-containing block B selected from block B-1 containing conjugated diene monomer units and block B-2 containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units using aromatic vinyl hydrocarbon monomers and / or conjugated diene monomers, wherein (i-B) forming conjugated diene monomer unit-containing block B is carried out in the presence of a chelating agent and an alkali metal alkoxide.

[0078] (i) It is preferable that block copolymer II be obtained by anionic polymerization using organolithium as an initiator. (i) Block copolymer II can be obtained in the same manner as the method for producing block copolymer II described above. The details are as described above, so they will not be described here.

[0079] <Step (ii)> In step (ii), block copolymer II is blended with rubber component I. The blending method is not limited, and the mixture can be kneaded and blended according to a conventional method using a commonly used mixer such as a Banbury mixer, kneader, or roll mixer at a temperature range of 100 to 140°C. If the rubber composition contains additives in addition to rubber component I and block copolymer II, other additives other than vulcanizing agents and vulcanization accelerators may be blended when blending block copolymer II with rubber component I. The rubber composition may also be prepared by adding and mixing vulcanizing agents and vulcanization accelerators to the resulting mixture in the final mixing stage.

[0080] [Block Copolymer II for Tire Rubber Compositions] The block copolymer II for tire rubber compositions according to this embodiment contains aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units. When block copolymer II containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units is blended with rubber component I, it is easy to obtain a tire rubber composition having a higher glass transition temperature Tg than conventional rubber compositions. Tires manufactured using a tire rubber component with a high glass transition temperature Tg tend to have higher wear resistance. The types and content of aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units, and the content of 1,2-bonds and 3,4-bonds in the conjugated diene monomers are as described above. The block structure, physical properties, manufacturing method, etc. of block copolymer II are also as described above.

[0081] [Modifier for Tire Rubber Components] The modifier for tire rubber components according to this embodiment includes block copolymer II containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units. When block copolymer II containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units is blended with tire rubber components, it becomes compatible with the tire rubber components and can modify them to have a higher glass transition temperature Tg. Tires manufactured using tire rubber components with a high glass transition temperature Tg tend to have higher wear resistance. The types and content of aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units, and the content of 1,2-bonds and 3,4-bonds in the conjugated diene monomers are as described above. The block structure, physical properties, manufacturing method, etc. of block copolymer II are also as described above.

[0082] [Method for improving the glass transition temperature Tg of tire rubber components] The method for improving the glass transition temperature Tg of tire rubber components according to this embodiment includes blending a block copolymer II containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units into the tire rubber components. Since block copolymer II has a high glass transition temperature Tg and is compatible with tire rubber components, blending it into the tire rubber components can increase the glass transition temperature Tg of the tire rubber components.

[0083] The amount of block copolymer II added 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, based on 100 parts by mass of the total of rubber component I and block copolymer.

[0084] The types and content of aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units, as well as the content of 1,2- and 3,4-bonds in the conjugated diene monomers, are as described above. The block structure, physical properties, and manufacturing method of block copolymer II are also as described above.

[0085] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of the present disclosure is disclosed below: [1] A tire rubber composition comprising rubber component I and block copolymer II comprising aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units. [2] The tire rubber composition according to [1], wherein the content of block copolymer II is 0.1 to 50 parts by mass per 100 parts by mass of rubber component I. [3] The tire rubber composition according to [1] or [2], wherein the content of aromatic vinyl hydrocarbon monomer units in the total monomer units of block copolymer II is 50 to 95% by mass. [4] The tire rubber composition according to any one of [1] to [3], wherein block copolymer II comprises block A comprising the aromatic vinyl hydrocarbon monomer units, block B-1 comprising the conjugated diene monomer units, and one or more conjugated diene monomer unit-containing block B selected from block B-2 comprising the aromatic vinyl hydrocarbon monomer units and the conjugated diene monomer units. [5] The tire rubber composition according to any one of [1] to [4], wherein the total amount of 1,2-conjugates and 3,4-conjugates in the block copolymer II is 90 mol% or less of the total amount of conjugated diene monomer units. [6] The tire rubber composition according to any one of [1] to [5], wherein the number average molecular weight Mn of the block copolymer II is 30,000 or less.A method for producing a rubber composition for tires according to any one of [7] [1] to [6], comprising: (i) obtaining a block copolymer II containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units using an aromatic vinyl hydrocarbon monomer and a conjugated diene monomer; and (ii) blending the block copolymer II with rubber component I, wherein obtaining the block copolymer II (i) comprises: forming a block A containing aromatic vinyl hydrocarbon monomer units using an aromatic vinyl hydrocarbon monomer (i-A); and forming one or more conjugated diene monomer unit-containing block B selected from block B-1 containing conjugated diene monomer units and block B-2 containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units using an aromatic vinyl hydrocarbon monomer and / or a conjugated diene monomer, wherein forming the conjugated diene monomer unit-containing block B (i-B) is carried out in the presence of a chelating agent and an alkali metal alkoxide. [8] Block copolymer II for tire rubber compositions, comprising aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units. [9] A method for producing the block copolymer II described in [8], comprising: (i-A) forming a block A comprising aromatic vinyl hydrocarbon monomer units using aromatic vinyl hydrocarbon monomers; and (i-B) forming one or more conjugated diene monomer unit-containing blocks B selected from block B-1 comprising conjugated diene monomer units and block B-2 comprising aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units, wherein the formation of the (i-B) conjugated diene monomer unit-containing block B is carried out in the presence of a chelating agent and an alkali metal alkoxide.

[10] A modifier for tire rubber components, comprising block copolymer II comprising aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units.

[11] A method for improving the glass transition temperature Tg of a tire rubber component, comprising blending a block copolymer II containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units into the tire rubber component.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.

[0086] The present disclosure will be further illustrated by the following examples, but these examples will not limit the interpretation of the present disclosure.

[0087] [Synthesis 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.

[0088] (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. After that, 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 precipitating it, block copolymer 1 having polystyrene block-(styrene-butadiene random block)-polystyrene block was obtained.

[0089] [Synthesis 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.

[0090] (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 a total of 28.0 kg of styrene monomer and a total of 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, when the internal temperature had dropped to 50°C, 2.0 kg of styrene was added and the polymerization reaction was carried out. After that, the polymerization active species were deactivated with water to obtain a polymerization solution containing block copolymer. By pouring the obtained polymerization solution into an excess amount of methanol and precipitating it, block copolymer 1 having polystyrene block-(styrene-butadiene random block)-polystyrene block was obtained.

[0091] [Synthesis 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.

[0092] (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, when the internal temperature had dropped to 50°C, 2.0 kg of styrene was added and the polymerization reaction was carried out. After that, the polymerization active species were deactivated with water to obtain a polymerization solution containing block copolymer. By pouring the obtained polymerization solution into an excess amount of methanol and precipitating it, block copolymer 3 having polystyrene block-(styrene-butadiene random block)-polystyrene block was obtained.

[0093] [Synthesis Example 4] (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.

[0094] (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. Next, after the styrene had been 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 and the polymerization reaction was carried out. 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 and the polymerization reaction was carried out. After that, 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 precipitating it, a block copolymer 4 having polystyrene block - polybutadiene block - polystyrene block was obtained.

[0095] [Synthesis Example 5] (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.

[0096] (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 was completely consumed, after waiting for the internal temperature of the reaction vessel to drop to 50°C, 8.0 kg of butadiene was added and the polymerization reaction was carried out. At this time, the internal temperature rose to 68°C. (4) Next, after the butadiene was 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. After that, 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 precipitating it, a block copolymer 5 having polystyrene block - polybutadiene block - polystyrene block was obtained.

[0097] [Measurement] The obtained block copolymers 1 to 5 were subjected to various physical property and structural analyses using the following methods. The results are shown in Table 1.

[0098] <Butadiene monomer unit content> The butadiene monomer unit content was measured by nuclear magnetic resonance (NMR) under the following conditions. Observed nuclei: １ H Observation frequency: 500.13 MHz Pulse waiting time: 3.0 seconds Number of integrations: 64 Solvent: Deuterated chloroform (CDCl) ３ )

[0099] <Number-average molecular weight (Mn) and molecular weight distribution (Mw / Mn)> The number-average molecular weight and molecular weight distribution were measured by GPC under the following conditions. Instrument name: HLC-8220GPC (Tosoh Corporation) Column: Four Shodex GPCKF-404 columns (Showa Denko Corporation) connected in series. Temperature: 40°C Detection: Ultraviolet-Vis spectroscopy (254 nm) Solvent: Tetrahydrofuran concentration: 2% by mass Calibration curve: Created using standard polystyrene (VARIAN Corporation).

[0100] <1,2-Structure content> Proton nuclear magnetic resonance ( １Using ¹H-NMR, the integral values ​​of signals attributed to the 1,4-structure (1,4-conjugate) and the integral values ​​of signals attributed to the 1,2-structure (1,2-conjugate) were determined. The proportion (mol%) of the 1,2-structure to the total amount (100 mol%) of the 1,4-structure and 1,2-structure was calculated and used as the total amount of 1,2-structure 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.

[0101] <Glass transition temperature Tg of block copolymers> The glass transition temperature Tg of block copolymers 1, 4, and 5 obtained in synthesis examples 1, 4, and 5 was measured using a differential scanning calorimeter (TA Instruments Q2000). 4 mg of the block copolymer sample was weighed into an aluminum pan and heated to 120°C at a heating rate of 10°C / min under a nitrogen atmosphere, then cooled to 30°C to quench the sample. Subsequently, the temperature was increased to 150°C at a heating rate of 10°C / min, and the glass transition temperature Tg was determined from the inflection point of the resulting thermal analysis curve.

[0102]

[0103] [Comparative Example 1] Styrene-butadiene rubber (SBR) (manufactured by ENEOS Material, "ESBR1500") was prepared as the rubber component and designated as Comparative Example 1.

[0104] [Examples 1-3] Using Toyo Seiki Laboplast Mill, 11 parts by mass of block copolymer 1 obtained in Synthesis Example 1 were mixed with 100 parts by mass of the rubber component of Comparative Example 1 and kneaded at 100°C to obtain the rubber composition of Example 1. Similarly, the rubber compositions of Examples 2 and 3 were obtained using block copolymer 4 obtained in Synthesis Example 4 and block copolymer 5 obtained in Synthesis Example 5, respectively.

[0105] [Measurement and Evaluation] <Glass Transition Temperature Tg of Rubber Compositions> The storage modulus (E') of the rubber compositions of Examples 1 to 3 and the rubber component of Comparative Example 1 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 2 mm thick sheet was prepared using the rubber compositions of Examples 1 to 3, 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 measuring instrument manufactured by TA Instruments, E', E'', and tanδ were measured in the temperature range of -100 to 120°C under the conditions of a heating rate of 4°C / min and a frequency of 1 Hz. From the dynamic viscoelasticity measurement of each rubber composition, the temperature at which the loss tangent value (tanδ) showed a peak 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 rubber component of Comparative Example 1 was calculated as the Tg increase. The results are shown in Table 2. Charts obtained by dynamic viscoelasticity measurement are shown in Figures 1 and 2. For the rubber composition of Example 3, since data on the high-temperature side has not been obtained, only the results for the temperature range of -60°C to -10°C (Figure 1) are shown.

[0106]

[0107] As shown in Table 2 and Figure 1, the rubber compositions of Examples 1 to 3 have a higher glass transition temperature Tg than the rubber component of Comparative Example 1, which used SBR alone. A comparison between Examples 1 and 2 and Example 3 shows that a higher total amount of 1,2-bonds relative to the total amount of conjugated diene monomer units in block copolymer II can further increase the glass transition temperature Tg. A comparison between Example 1 and Example 2 shows that if block B containing conjugated diene monomer units in block copolymer II includes block B-2 (especially random blocks) containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units, the glass transition temperature Tg can be further increased.

[0108] The compatibility of block copolymer II with rubber components is examined with reference to Table 1 and Figure 2. Since block copolymers 1 and 4 have glass transition temperatures Tg of 47°C and 63°C, respectively, if they are incompatible with the rubber component (SBR) when blended into a rubber composition, peaks should be observed around 47°C and 63°C, respectively, in the dynamic viscoelasticity measurement of the rubber composition. However, as shown in Figure 2, in both rubber compositions of Examples 1 and 2, no peaks originating from block copolymer II are found on the high-temperature side above 0°C in the dynamic viscoelasticity measurement. Therefore, it can be seen that block copolymer II has good compatibility with rubber components such as SBR.

[0109] The tire rubber composition of this embodiment can be applied to various parts of pneumatic tires, such as the tread and sidewall, for various applications and sizes, including passenger car tires and large tires for trucks and buses, thus possessing industrial applicability.

Claims

1. A rubber composition for tires comprising rubber component I and block copolymer II containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units.

2. The tire rubber composition according to claim 1, wherein the content of the block copolymer II is 0.1 to 50 parts by mass per 100 parts by mass of the rubber component I.

3. The tire rubber composition according to claim 1 or 2, wherein the content of aromatic vinyl hydrocarbon monomer units in the total monomer units of the block copolymer II is 50 to 95% by mass.

4. The tire rubber composition according to claim 1 or 2, wherein the block copolymer II comprises block A containing the aromatic vinyl hydrocarbon monomer units, block B-1 containing the conjugated diene monomer units, and one or more conjugated diene monomer unit-containing blocks B selected from block B-2 containing the aromatic vinyl hydrocarbon monomer units and the conjugated diene monomer units.

5. The tire rubber composition according to claim 1 or 2, wherein the total amount of 1,2-conjugates and 3,4-conjugates in relation to the total amount of conjugated diene monomer units in the block copolymer II is 90 mol% or less.

6. The tire rubber composition according to claim 1 or 2, wherein the number average molecular weight Mn of the block copolymer II is 30,000 or less.

7. A method for producing a rubber composition for tires according to claim 1 or 2, comprising: (i) obtaining a block copolymer II containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units using an aromatic vinyl hydrocarbon monomer and a conjugated diene monomer; and (ii) blending the block copolymer II with a rubber component I, wherein obtaining the block copolymer II (i) comprises: forming a block A containing aromatic vinyl hydrocarbon monomer units using an aromatic vinyl hydrocarbon monomer (i-A); and forming one or more conjugated diene monomer unit-containing blocks B selected from block B-1 containing conjugated diene monomer units and block B-2 containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units using an aromatic vinyl hydrocarbon monomer and / or a conjugated diene monomer, wherein forming the conjugated diene monomer unit-containing blocks B (i-B) is carried out in the presence of a chelating agent and an alkali metal alkoxide.

8. Block copolymer II for tire rubber compositions, comprising aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units.

9. A method for producing block copolymer II according to claim 8, comprising: forming a block A containing aromatic vinyl hydrocarbon monomer units using (i-A) an aromatic vinyl hydrocarbon monomer; and forming one or more conjugated diene monomer unit-containing blocks B selected from block B-1 containing conjugated diene monomer units and block B-2 containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units using (i-B) an aromatic vinyl hydrocarbon monomer and / or a conjugated diene monomer, wherein the formation of the (i-B) conjugated diene monomer unit-containing block B is carried out in the presence of a chelating agent and an alkali metal alkoxide.

10. A tire rubber component modifier comprising block copolymer II containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units.

11. A method for improving the glass transition temperature Tg of a tire rubber component, comprising blending a block copolymer II containing aromatic vinyl hydrocarbon monomer units and conjugated diene monomer units into the tire rubber component.

Images