Rubber composition and tire

Abstract

To provide a rubber composition which achieves steering stability of a tire and low heat build-up properties.SOLUTION: The rubber composition contains: a rubber component containing a copolymer having a conjugated diene unit and less than 10 mass% of an aromatic vinyl unit; and a filler. The copolymer is a modified copolymer modified with a compound represented by formula (1) (where R1-R8 are each independently a C1-20 alkyl group; L1 and L2 are each independently a C1-20 alkylene group; and n is an integer of 2-4).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition and a tire. [Background technology]

[0002] In recent years, in connection with the global movement toward carbon dioxide emission regulations accompanying societal demands for energy conservation and growing interest in environmental issues, there has been an increasing demand for improved fuel efficiency in automobiles. In order to meet such demands for improved fuel efficiency, there has also been a demand for reduced rolling resistance in tire performance. Although optimization of tire structure has been investigated as a method for reducing tire rolling resistance, the general method used is to use a material with lower heat buildup as the rubber composition.

[0003] As a technique for improving the low heat buildup of a rubber composition, for example, Patent Document 1 discloses a rubber composition that uses, as a rubber component, a modified copolymer obtained by reacting a specific imino group-containing hydrocarbyloxysilane compound. The rubber composition of Patent Document 1 has improved dispersibility of the filler in the rubber composition, and therefore can achieve a certain rolling resistance reduction effect when applied to tires. However, the improvement effect of the rubber composition of Patent Document 1 is not sufficient to meet the recent demand for improved fuel economy, and further improvement in low heat buildup has been desired.

[0004] Furthermore, techniques for adjusting the rubber components have been developed to improve the low heat buildup of rubber compositions. For example, Patent Document 2 discloses a rubber composition that uses a styrene-butadiene rubber with a reduced styrene content as the rubber component. However, when a styrene-butadiene rubber having a reduced amount of styrene is used, although the low heat buildup property can be improved, it is thought that performance such as steering stability may be reduced when the rubber composition is applied to a tire.

[0005] Furthermore, in order to improve the low heat buildup of the rubber composition, it is conceivable to reduce the content of fillers such as carbon black. However, as in the case of using styrene-butadiene rubber with a reduced amount of styrene, it is conceivable that such performance as reinforcement of the rubber, abrasion resistance, and handling stability when applied to tires will be reduced. Therefore, there is a demand for the development of a technology that can significantly improve low heat buildup without degrading performance other than low heat buildup, such as steering stability when applied to tires. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 4478262 [Patent Document 2] Japanese Patent Application Publication No. 2018-131560 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide a rubber composition that achieves excellent low heat buildup while maintaining good handling stability when applied to a tire, and further to provide a tire that has improved rolling resistance and handling stability. [Means for solving the problem]

[0008] The present inventors conducted research to solve the above-mentioned problems and found that the low heat buildup of a rubber composition can be improved by using a copolymer having conjugated diene units and aromatic vinyl units as the rubber component and reducing the aromatic vinyl unit content of the copolymer to less than 10% by mass. However, as mentioned above, a low aromatic vinyl unit content in the copolymer leads to a problem of reduced performance, such as poor handling stability, when the rubber composition is applied to a tire. Therefore, the present inventors conducted further research and found that modifying the copolymer with a specific modifier having an oligosiloxane and a tertiary amino group can significantly improve the dispersibility of the filler. Therefore, in addition to the low heat buildup effect achieved by improving the polymer, the improved dispersibility of the filler can further improve the low heat buildup and the handling stability when applied to a tire.

[0009] The gist of the present invention is as follows. The rubber composition of the present invention is a rubber composition comprising a rubber component containing a copolymer having a conjugated diene unit and an aromatic vinyl unit, and a filler, The copolymer is characterized in that the content of the aromatic vinyl unit is less than 10% by mass and is a modified copolymer modified with a modifying agent containing a compound represented by formula (1). [ka] (In the formula, R1 to R8 are each independently an alkyl group having 1 to 20 carbon atoms; L1 and L2 are each independently an alkylene group having 1 to 20 carbon atoms; and n is an integer of 2 to 4.) The above-mentioned configuration makes it possible to achieve excellent low heat buildup while maintaining good steering stability when applied to a tire.

[0010] The rubber composition of the present invention preferably further contains a conjugated diene rubber different from the modified copolymer, because this can further improve the handling stability, abrasion resistance, etc. when applied to a tire.

[0011] Furthermore, in the rubber composition of the present invention, the content of the aromatic vinyl unit in the copolymer is preferably 8% by mass or less, because this allows for obtaining better low heat buildup properties.

[0012] In addition, in the rubber composition of the present invention, the modifier is preferably any one of the formulae (1a) to (1e). [ka] This is because it is possible to achieve both low heat buildup and higher levels of handling stability when applied to tires.

[0013] Furthermore, the copolymer is preferably a modified copolymer that has been further modified with a modifying agent containing a compound represented by formula (2). [ka] (In formula (2), R1 to R3 are each independently hydrogen; an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms, a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms; R4 is a single bond; a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituted or unsubstituted arylene group having 5 to 20 carbon atoms, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkylene group having 5 to 20 carbon atoms, or a heterocyclic group having 5 to 30 carbon atoms; or an aryl group having 6 to 20 carbon atoms, and R5 is an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; a heterocyclic group having 3 to 30 carbon atoms; or a functional group represented by the following chemical formula (2a) or chemical formula (2b), where n is an integer of 1 to 5, and at least one of R5 is a functional group represented by the following chemical formula (2a) or chemical formula (2b), and when n is an integer of 2 to 5, multiple R5 may be the same or different. [ka] In formula (2a), R6 is a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms; R7 and R8 are each independently an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms. an alkylene group having 1 to 20 carbon atoms, substituted or unsubstituted with an aryl group, wherein R9 is hydrogen, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an alkynyl group having 2 to 30 carbon atoms, a heteroalkyl group having 1 to 30 carbon atoms, a heteroalkenyl group having 2 to 30 carbon atoms, a heteroalkynyl group having 2 to 30 carbon atoms, a cycloalkyl group having 5 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or a heterocyclic group having 3 to 30 carbon atoms; and X is an N, O, or S atom, and when X is O or S, R9 does not exist. [ka] In formula (2b), R 10 represents a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms; R 11 and R 12 are each independently an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms. This is because it is possible to achieve both low heat buildup and higher levels of handling stability when applied to tires.

[0014] The tire of the present invention is characterized by using the rubber composition of the present invention described above. The above configuration can improve rolling resistance and steering stability. [Effects of the Invention]

[0015] According to the present invention, a rubber composition can be provided that achieves excellent low heat buildup while maintaining good handling stability when applied to a tire, and a tire with improved rolling resistance and handling stability can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, one embodiment of the present invention will be specifically described. <Rubber composition> The rubber composition of the present invention is a rubber composition containing a rubber component and a filler. Each component constituting the rubber composition of the present invention will be described below.

[0017] (rubber component) The rubber composition of the present invention contains a rubber component. The rubber component contains a copolymer having a conjugated diene unit and an aromatic vinyl unit, and the copolymer is a modified copolymer modified with a modifier containing a compound represented by formula (1). [ka] By using as the rubber component a copolymer modified with a modifier containing a compound represented by formula (1) containing an oligosiloxane, which is a filler affinity functional group, and a tertiary amino group, the dispersibility of fillers such as silica in the rubber composition can be improved. As a result, the rubber composition of the present invention has significantly improved low heat buildup properties and improved filler dispersibility, which makes it possible to improve other physical properties such as reinforcement, handling stability when applied to tires, and processability.

[0018] In formula (1), R1 to R8 are each independently an alkyl group having 1 to 20 carbon atoms; L1 and L2 are each independently an alkylene group having 1 to 20 carbon atoms; and n is an integer of 2 to 4.

[0019] Specifically, in formula (1), R1 to R4 may each independently represent a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. When R1 to R4 are substituted, they each independently represent an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkoxy group having 4 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, an alkanoyloxy group having 2 to 12 carbon atoms (alkanoyl, RaCOO - wherein Ra is an alkyl group having 1 to 9 carbon atoms), an aralkyloxy group having 7 to 13 carbon atoms, an arylalkyl group having 7 to 13 carbon atoms, and an alkylaryl group having 7 to 13 carbon atoms. More specifically, R1 to R4 may be a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and even more specifically, R1 to R4 may each independently be a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0020] In addition, in formula (1), R5 to R8 are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, specifically a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, more specifically a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and when substituted, may be substituted with the substituents described above for R1 to R4. If R5 to R8 are not alkyl groups but hydrolyzable substituents, the bonds N-R5R6 and N-R7R8 may be hydrolyzed to NH in the presence of moisture, which may adversely affect the processability of the polymer.

[0021] More specifically, in the compound represented by the formula (1), R1 to R4 can be a methyl group or an ethyl group, and R5 to R8 can be an alkyl group having 1 to 10 carbon atoms.

[0022] In the present invention, the amino groups in the compound represented by formula (1), i.e., N-R5R6 and N-R7R8, are preferably tertiary amino groups, which provide better processability when the compound represented by formula (1) is used as a modifying agent. If a protecting group for protecting the amino group or hydrogen is bonded to R5 to R8, it may be difficult to realize the effect of the compound represented by formula (1). If hydrogen is bonded, the anion reacts with hydrogen during the modification process and loses its reactivity, making the modification reaction impossible. If a protecting group is bonded, the modification reaction will occur, but while it remains bonded to the polymer end, it will be deprotected by hydrolysis during post-processing to become a primary or secondary amino group. The deprotected primary or secondary amino group may cause the compound to increase in viscosity during subsequent blending, potentially resulting in reduced processability.

[0023] In addition, L1 and L2 in the compound represented by the formula (1) are each independently a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms. More specifically, L1 and L2 can each independently be an alkylene group having 1 to 10 carbon atoms, and even more specifically, an alkylene group having 1 to 6 carbon atoms such as a methylene group, an ethylene group, or a propylene group.

[0024] Regarding L1 and L2 in the compound represented by formula (1), the shorter the distance between the Si atom and the N atom in the molecule, the better the effect. However, if Si is directly bonded to N, the bond between Si and N may be broken during subsequent processing steps. The secondary amino group generated in this case is likely to be washed away by water during post-processing. In the resulting modified copolymer, the amino group that promotes bonding with the silica filler makes it difficult to bond with the silica filler, which may result in a reduced dispersing effect of the dispersant. Considering the improvement effect depending on the bond length between Si and N, L1 and L2 are preferably each independently an alkylene group having 1 to 3 carbon atoms, such as a methylene group, an ethylene group, or a propylene group. More specifically, they can be a propylene group. Furthermore, L1 and L2 can be substituted with the substituents described above for R1 to R4.

[0025] The compound represented by formula (1) is preferably, for example, any one of the compounds represented by the following formulas (1a) to (1e), because this allows for a higher level of both low heat buildup and steering stability when applied to a tire. [ka]

[0026] In the modifier of the present invention, the compound represented by formula (1) has an alkoxysilane structure that bonds to the activated end of a conjugated diene polymer, while the Si-O-Si structure and three or more amino groups bonded to the end exhibit affinity for fillers such as silica, thereby promoting bonding between the filler and the modified copolymer compared to conventional modifiers containing only one amino group per molecule. Furthermore, the degree of bonding at the activated end of the conjugated diene polymer is uniform, and when observing the change in molecular weight distribution before and after coupling, the molecular weight distribution remains constant without increasing compared to before coupling. Therefore, there is no deterioration in the physical properties of the modified copolymer itself, and filler aggregation in the rubber composition can be prevented, improving filler dispersibility and improving the processability of the rubber composition. These effects, in particular, can result in balanced improvements in fuel economy, wear characteristics, and handling stability when the rubber composition is applied to tires.

[0027] The compound represented by formula (1) can be prepared through a condensation reaction represented by the following reaction scheme 1. [ka]

[0028] In the reaction formula 1, R1 to R8, L1 and L2, and n are the same as those defined in the above formula (1), and R' and R'' are any substituents that do not affect the condensation reaction. For example, R' and R'' can each independently be the same as any one of R1 to R4.

[0029] The reaction of Reaction Scheme 1 is carried out under acidic conditions, and any acid generally used in condensation reactions can be used without limitation. Those skilled in the art can select an optimal acid depending on various process variables such as the type of reactor in which the reaction is carried out, starting materials, and reaction temperature.

[0030] The copolymer modified with the modifying agent containing the compound represented by the formula (1) is a copolymer having a conjugated diene unit and an aromatic vinyl unit. The conjugated diene units and aromatic vinyl units may be randomly arranged and bonded to form a random copolymer.

[0031] In the rubber composition of the present invention, the content of aromatic vinyl units in the copolymer (the mass of aromatic vinyl units relative to the total mass of the copolymer) must be less than 10% by mass. This is because the low heat buildup properties of the rubber composition can be improved. From the same viewpoint, the content of aromatic vinyl units is preferably 8% by mass or less, and more preferably 7% by mass or less. Note that, from the viewpoint of maintaining good levels of handling stability and abrasion resistance when the rubber composition is applied to a tire, the content of aromatic vinyl units in the copolymer is preferably 3% by mass or more.

[0032] The type of conjugated diene monomer that forms the conjugated diene unit is not particularly limited, and may be, for example, one or more selected from the group consisting of 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, piperylene, 3-butyl-1,3-octadiene, isoprene, and 2-phenyl-1,3-butadiene.

[0033] The type of aromatic vinyl monomer that forms the aromatic vinyl unit is not particularly limited, and may be, for example, at least one selected from the group consisting of styrene, α-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 1-vinylnaphthalene, 4-cyclohexylstyrene, 4-(p-methylphenyl)styrene, and 1-vinyl-5-hexylnaphthalene.

[0034] Furthermore, the copolymer of the modified copolymer can be a combination of the above-mentioned conjugated diene monomer and aromatic vinyl monomer, but among them, styrene-butadiene rubber is preferable, because it can more reliably achieve excellent low heat buildup without deteriorating other performances, and also provides excellent wet performance when applied to tires.

[0035] The modified copolymer may have a narrow molecular weight distribution: Mw / Mn (also referred to as polydispersity index (PDI)) of 1.1 to 3.0. If the molecular weight distribution of the modified copolymer exceeds 3.0 or is less than 1.1, the tensile properties and viscoelasticity may be reduced when applied to a rubber composition. Considering the remarkable effect of improving the tensile properties and viscoelasticity of a polymer by controlling the molecular weight distribution of the modified copolymer, it is preferable that the molecular weight distribution of the modified copolymer be 1.3 to 2.0. Note that, by using the modifier, the molecular weight distribution of the modified copolymer becomes similar to that of the copolymer before modification.

[0036] The molecular weight distribution of the modified copolymer can be calculated from the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn). The number average molecular weight (Mn) is the common average of the molecular weights of individual polymers calculated by measuring the molecular weights of n polymer molecules, summing the molecular weights, and dividing by n. The weight average molecular weight (Mw) represents the molecular weight distribution of the polymer composition. The average of the total molecular weight can be expressed in grams per mole (g / mol). In the present invention, the weight average molecular weight and number average molecular weight are each a polystyrene-equivalent molecular weight analyzed by gel permeation chromatography (GPC).

[0037] The modified copolymer satisfies the above-mentioned molecular weight distribution conditions and may have a number average molecular weight (Mn) of 50,000 g / mol to 2,000,000 g / mol, more specifically, 200,000 g / mol to 800,000 g / mol, and a weight average molecular weight (Mw) of 100,000 g / mol to 4,000,000 g / mol, more specifically, 300,000 g / mol to 1,500,000 g / mol.

[0038] If the weight-average molecular weight (Mw) of the modified copolymer is less than 100,000 g / mol or the number-average molecular weight (Mn) is less than 50,000 g / mol, the tensile properties may be reduced when applied to a rubber composition. On the other hand, if the weight-average molecular weight (Mw) is greater than 4,000,000 g / mol or the number-average molecular weight (Mn) is greater than 2,000,000 g / mol, the processability of the modified copolymer may be reduced, resulting in a deterioration in the workability of the rubber composition, making kneading difficult and making it difficult to sufficiently improve the physical properties of the rubber composition. More specifically, when the modified copolymer according to one embodiment of the present invention simultaneously satisfies the requirements for weight average molecular weight (Mw) and number average molecular weight (Mn) in addition to the molecular weight distribution, it can improve the viscoelasticity and processability of the rubber composition in a balanced manner when applied to the rubber composition.

[0039] The present invention also provides a method for producing the modified copolymer, which utilizes a modifying agent containing the compound represented by formula (1). Specifically, the method for preparing the modified copolymer may include the steps of: 1) polymerizing an aromatic vinyl monomer and a conjugated diene monomer in a hydrocarbon solvent in the presence of an organic alkali metal compound to prepare an activated polymer having an alkali metal bonded to at least one end; and 2) reacting the activated polymer with a modifying agent containing the compound represented by Formula 1.

[0040] The step 1) is a step for preparing an activated polymer having an alkali metal bonded to at least one end thereof, and can be carried out by polymerizing an aromatic vinyl monomer and a conjugated diene monomer in a hydrocarbon solvent in the presence of an organic alkali metal compound.

[0041] The hydrocarbon solvent is not particularly limited, but may be, for example, one or more selected from the group consisting of n-pentane, n-hexane, n-heptane, isooctane, cyclohexane, toluene, benzene, and xylene.

[0042] The organic alkali metal compound can be used in an amount of 0.1 mmol to 1.0 mmol based on 100 g of the total monomers. The organic alkali metal compound is not particularly limited, and for example, one or more compounds selected from the group consisting of methyl lithium, ethyl lithium, propyl lithium, n-butyl lithium, s-butyl lithium, t-butyl lithium, hexyl lithium, n-decyl lithium, t-octyl lithium, phenyl lithium, 1-naphthyl lithium, n-eicosyl lithium, 4-butylphenyl lithium, 4-tolyl lithium, cyclohexyl lithium, 3,5-di-n-heptylcyclohexyl lithium, 4-cyclopentyl lithium, naphthyl sodium, naphthyl potassium, lithium alkoxide, sodium alkoxide, potassium alkoxide, lithium sulfonate, sodium sulfonate, potassium sulfonate, lithium amide, sodium amide, potassium amide, and lithium isopropylamide can be used.

[0043] The polymerization in step 1 may be carried out by further adding a polar additive, if necessary, and the polar additive may be added in an amount of 0.001 to 1.0 part by weight relative to 100 parts by weight of the total monomers, specifically 0.005 to 0.5 parts by weight, more specifically 0.01 to 0.3 parts by weight relative to 100 parts by weight of the total monomers. As the polar additive, for example, one or more selected from the group consisting of tetrahydrofuran, ditetrahydrofurylpropane, diethyl ether, cycloamethyl ether, dipropyl ether, ethylene dimethyl ether, ethylene dimethyl ether, diethyl glycol, dimethyl ether, tert-butoxyethoxyethane, bis(3-dimethylaminoethyl)ether, (dimethylaminoethyl)ethyl ether, trimethylamine, triethylamine, tripropylamine, and tetramethylethylenediamine can be used.

[0044] In the above-mentioned production method, when a conjugated diene monomer and an aromatic vinyl monomer are copolymerized by using the polar additive, the difference in reaction rate between them can be compensated for, thereby guiding the formation of a random copolymer.

[0045] The polymerization in the step 1) can be carried out via adiabatic polymerization or isothermal polymerization. Here, the adiabatic polymerization refers to a polymerization method including a step of polymerizing an organic alkali metal compound by heat of self-reaction without adding any heat after adding the organic alkali metal compound, and the isothermal polymerization refers to a polymerization method of maintaining a constant temperature of the polymer by adding or removing heat after adding the organic alkali metal compound.

[0046] Furthermore, the polymerization may be carried out in a temperature range of 20°C to 200°C, specifically in a temperature range of 0°C to 150°C, and more specifically in a temperature range of 10°C to 120°C.

[0047] The step 2) is a modification reaction step in which the activated polymer is reacted with a modifying agent containing the compound represented by formula (1) to produce a modified copolymer.

[0048] In this case, the modifying agent containing the compound represented by formula (1) may be the same as that described above. The compound represented by formula (1) can be used in an amount of 0.1 to 2.0 moles per mole of the organic alkali metal compound. Furthermore, the reaction in step 2) is a modification reaction for introducing a functional group into the polymer, and each of the reactions may be carried out at a temperature in the range of 0°C to 90°C for 1 minute to 5 hours.

[0049] In addition, the above-mentioned preparation method may further include, after step 2), one or more steps of recovering the solvent and unreacted monomer and drying, if necessary.

[0050] Furthermore, the rubber component preferably contains a conjugated diene rubber other than the modified copolymer (hereinafter, sometimes referred to as "other conjugated diene rubber") for the purpose of improving steering stability, reinforcement, abrasion resistance, etc. when applied to a tire. The other conjugated diene rubbers can be appropriately selected depending on the required performance, and may be, for example, natural rubber (NR) containing cis-1,4-polyisoprene; modified natural rubbers such as epoxidized natural rubber (ENR), deproteinized natural rubber (DPNR), and hydrogenated natural rubber, which are obtained by modifying or refining the general natural rubbers; or synthetic rubbers such as styrene-butadiene copolymer (SBR), polybutadiene (BR), polyisoprene (IR), and ethylene-propylene copolymer rubber, or a mixture of two or more of these may be used.

[0051] The content of the modified copolymer in the rubber component by the modifier containing the compound represented by formula (1) is not particularly limited, but can be 0.1 to 100% by mass, preferably 10 to 100% by mass, and more preferably 20 to 90% by mass. When the content of the modified copolymer is 0.1% by mass or more, low heat buildup can be improved while maintaining other physical properties well, and as a result, effects such as fuel economy, wear characteristics, and braking characteristics can be more reliably obtained in molded articles manufactured using the rubber composition, such as tires.

[0052] As described above, the copolymer is modified with a modifier containing a compound represented by formula (1), but it is preferably further modified with a modifier containing a compound represented by formula (2). This can further improve the dispersibility of the filler in the rubber composition, thereby achieving both low heat buildup and improved handling stability when applied to tires, and also further improving wear resistance and processability.

[0053] [ka] In the above formula (2), R1 to R3 are each independently hydrogen; an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms, a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms; and R4 is a single bond; a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituted or unsubstituted arylene group having 5 to 20 carbon atoms, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a heteroalkenyl group having 2 to 30 carbon atoms, a heteroalkynyl group having 2 to 30 carbon atoms, a cycloalkyl group having 5 to 30 carbon atoms, or a heterocyclic group having 3 to 30 carbon atoms. R5 is a functional group represented by the following chemical formula (2a) or (2b), wherein n is an integer of 1 to 5, and at least one of R5 is a functional group represented by the following chemical formula (2a) or (2b), and when n is an integer of 2 to 5, the multiple R5s may be the same or different.

[0054] [ka] In the above formula (2a), R6 is a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms; R7 and R8 are each independently an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms. an alkylene group having 1 to 20 carbon atoms, substituted or unsubstituted with an aryl group having 1 to 0 carbon atoms, R9 is hydrogen, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an alkynyl group having 2 to 30 carbon atoms, a heteroalkyl group having 1 to 30 carbon atoms, a heteroalkenyl group having 2 to 30 carbon atoms, a heteroalkynyl group having 2 to 30 carbon atoms, a cycloalkyl group having 5 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or a heterocyclic group having 3 to 30 carbon atoms, and X is an N, O, or S atom, and when X is O or S, R9 does not exist.

[0055] [ka] In the above formula (2b), R 10 represents a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms; R 11 and R 12 are each independently an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms.

[0056] In the compound represented by the above formula (2), R1 to R3 are each independently hydrogen; an alkyl group having 1 to 10 carbon atoms; an alkenyl group having 2 to 10 carbon atoms; or an alkynyl group having 2 to 10 carbon atoms; R4 is a single bond; or an unsubstituted alkylene group having 1 to 10 carbon atoms; R5 is an alkyl group having 1 to 10 carbon atoms; an alkenyl group having 2 to 10 carbon atoms; or a group represented by the following chemical formula (2a) or is a functional group represented by chemical formula (2b), and in the above chemical formula (2a), R6 is an unsubstituted alkylene group having 1 to 10 carbon atoms, R7 and R8 are each independently an unsubstituted alkylene group having 1 to 10 carbon atoms, and R7 is an alkyl group having 1 to 10 carbon atoms; a cycloalkyl group having 5 to 20 carbon atoms; an aryl group having 6 to 20 carbon atoms; or a heterocyclic group having 3 to 20 carbon atoms, and in the above chemical formula (2b), R 10 is an unsubstituted alkylene group having 1 to 10 carbon atoms, and R 11 and R 12 may each independently be an alkyl group having 1 to 10 carbon atoms; a cycloalkyl group having 5 to 20 carbon atoms; an aryl group having 6 to 20 carbon atoms; or a heterocyclic group having 3 to 20 carbon atoms.

[0057] More specifically, the compound represented by the above formula (2) can be the compounds represented by the following formulas (2-1) to (2-3).

[0058] [ka]

[0059] When the copolymer is modified with a modifying agent containing the compound represented by the formula (2), the modifying agent containing the compound represented by the formula (2) is used as a modification initiator. Specifically, for example, a conjugated diene monomer and an aromatic vinyl monomer are polymerized in a hydrocarbon solvent in the presence of a modifying agent containing a compound represented by formula (2), thereby imparting a modifying group derived from the compound represented by formula (2) to the copolymer.

[0060] Here, the polymerization of the conjugated diene monomer and the aromatic vinyl monomer may be, for example, anionic polymerization. A specific example thereof may be living anionic polymerization in which an anionic active site is formed at the polymerization terminal by a growth polymerization reaction using an anion. The polymerization may be temperature-rising polymerization, isothermal polymerization, or constant-temperature polymerization (adiabatic polymerization). The constant-temperature polymerization refers to a polymerization method including a step of polymerizing by self-reaction heat without adding any heat after adding a modifying agent containing the compound represented by formula (2). The temperature-rising polymerization refers to a polymerization method of increasing the temperature by adding any heat after adding a modifying initiator. The isothermal polymerization refers to a polymerization method of maintaining a constant temperature of the polymer by adding heat or removing heat after adding the modifying initiator.

[0061] (filler) The rubber composition of the present invention contains a filler in addition to the above-mentioned rubber component. By using a filler together with a rubber component containing the modified copolymer, the dispersibility of the filler is improved, and when the rubber composition is applied to a tire, excellent low heat buildup can be achieved while maintaining high levels of performance such as steering stability, strength, abrasion resistance, and wet grip performance.

[0062] Here, the content of the filler is not particularly limited, but is preferably 10 to 160 parts by mass, and more preferably 30 to 120 parts by mass, per 100 parts by mass of the rubber component. By optimizing the amount of filler, better low heat buildup and wear resistance can be achieved, and when the content is 10 parts by mass or more, sufficient wear resistance can be obtained, and when the content is 160 parts by mass or less, deterioration of low heat buildup can be suppressed.

[0063] The type of filler is not particularly limited. For example, it may contain carbon black, silica, or other inorganic fillers. Among these, it is preferable that the filler contains at least silica. This is because it is possible to further improve low heat buildup, abrasion resistance, and wet performance when used in tires. This can prevent deterioration in the processability of the composition.

[0064] The silica preferably has a specific surface area of ​​50 m 2 / g or more, and preferably 350m 2 / g or less. The CTAB specific surface area of ​​silica is 50m 2 / g or more, the abrasion resistance is further improved, and the CTAB specific surface area of ​​the silica is 350m 2 / g or less, the rolling resistance will be small. The type of silica is not particularly limited. For example, wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc. are listed, and among these, wet silica is preferred. These silicas may be used alone or in combination of two or more. Examples of the silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate, and among these, wet silica is preferred. These silicas may be used alone or in combination of two or more. The wet silica may be precipitated silica, which is obtained by growing primary silica particles in a reaction solution at a relatively high temperature in a neutral to alkaline pH range in the early stages of production, and then aggregating the primary particles by controlling the temperature to the acidic side.

[0065] Furthermore, the content of the silica is not particularly limited, but is preferably 10 to 160 parts by mass, and more preferably 30 to 120 parts by mass, per 100 parts by mass of the rubber component. By optimizing the amount of filler, better low heat buildup and abrasion resistance can be achieved; when the content is 10 parts by mass or more, sufficient abrasion resistance can be obtained, and when the content is 30 parts by mass or less, deterioration of low heat buildup can be suppressed.

[0066] Furthermore, the filler preferably contains carbon black in addition to the silica, because this allows for better reinforcement and abrasion resistance to be achieved. Examples of the carbon black include GPF, FEF, SRF, HAF, ISAF, IISAF, and SAF grade carbon black.

[0067] From the viewpoint of obtaining better abrasion resistance, the content of the carbon black is preferably 2 parts by mass or more, and more preferably 4 parts by mass or more, per 100 parts by mass of the rubber component. By setting the content of the carbon black to 2 parts by mass or more, per 100 parts by mass of the rubber component, the abrasion resistance of the rubber composition can be further improved. Furthermore, the content of the carbon black is preferably 90 parts by mass or less, and more preferably 70 parts by mass or less, per 100 parts by mass of the rubber component. By setting the content of the carbon black to 90 parts by mass or less, per 100 parts by mass of the rubber component, it is possible to further improve low heat build-up and processability while maintaining a high level of abrasion resistance.

[0068] As the other filler, for example, an inorganic compound represented by the following formula (A) can also be used. nM xSiO Y zH2O (A) (In the formula, M represents at least one metal selected from the group consisting of Al, Mg, Ti, Ca, and Zr, oxides or hydroxides of these metals, hydrates thereof, and carbonates of these metals; and n, x, y, and z represent an integer of 1 to 5, an integer of 0 to 10, an integer of 2 to 5, and an integer of 0 to 10, respectively.)

[0069] Inorganic compounds of the above formula (A) include alumina (Al2O3) such as γ-alumina and α-alumina; alumina monohydrate (Al2O3·H2O) such as boehmite and diaspore; aluminum hydroxide [Al(OH)3] such as gibbsite and bayerite; aluminum carbonate [Al2(CO3)3], magnesium hydroxide [Mg(OH)2], magnesium oxide (MgO), magnesium carbonate (MgCO3), talc (3MgO·4SiO2·H2O), attapulgite (5MgO·8SiO2·9H2O), titanium dioxide (TiO2), titanium black (TiO 2n-1 ), calcium oxide (CaO), calcium hydroxide [Ca(OH)2], magnesium aluminum oxide (MgO·Al2O3), clay (Al2O3·2SiO2), kaolin (Al2O3·2SiO2·2H2O), pyrophyllite (Al2O3·4SiO2·H2O), bentonite (Al2O3·4SiO2·2H2O), aluminum silicate (Al2SiO5, Al4·3SiO4·5H2O, etc.), magnesium silicate (Mg2SiO4, MgSiO3, etc.), ke Examples include calcium silicate (Ca2SiO4, etc.), calcium aluminum silicate (Al2O3·CaO·2SiO2, etc.), calcium magnesium silicate (CaMgSiO4), calcium carbonate (CaCO3), zirconium oxide (ZrO2), zirconium hydroxide [ZrO(OH)2·nH2O], zirconium carbonate [Zr(CO3)2], and crystalline aluminosilicates containing hydrogen, alkali metals, or alkaline earth metals to compensate for the charge, such as various zeolites.

[0070] (Other ingredients) The rubber composition of the present invention may contain other components in addition to the rubber component and filler described above, to the extent that the effects of the present invention are not impaired. Other components may include, as appropriate, additives commonly used in the rubber industry, such as silane coupling agents, thermoplastic resins, plasticizers, liquid rubbers, antioxidants, crosslinking accelerators, crosslinking agents, crosslinking accelerator assistants, antiozonants, surfactants, etc.

[0071] When silica is contained as the filler, the use of the silane coupling agent together increases the dispersibility of the silica, and more excellent low heat generation properties and reinforcing properties can be obtained. Here, the silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, and 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide. Examples of the silyl ester include 3-triethoxysilylpropyl benzothiazolyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide, and any one of these or a mixture of two or more thereof can be used. From the viewpoint of improving the reinforcement of the rubber composition, it is preferable that the silane coupling agent contains bis(3-triethoxysilylpropyl) polysulfide or 3-trimethoxysilylpropyl benzothiazyl tetrasulfide.

[0072] In addition, since the rubber composition of the present invention uses a modified copolymer in which a functional group having high affinity for silica-based fillers is introduced into the active site as the rubber component, the amount of silane coupling agent can be reduced compared to normal cases. For example, the content of the silane coupling agent can be 1 to 20 parts by mass per 100 parts by weight of the silica. When used within this range, the effect as a coupling agent can be fully exerted and gelation of the rubber component can be prevented. From the same perspective, the content of the silane coupling agent can be 5 to 15 parts by mass per 100 parts by mass of the silica.

[0073] The rubber composition of the present invention may further contain a thermoplastic resin, which can improve the processability of the rubber composition and also improve the braking performance on dry and wet road surfaces when the rubber composition is used in a tire.

[0074] The type of the thermoplastic resin is not particularly limited, and examples thereof include C5 resins, C9 resins, C5-C9 resins, dicyclopentadiene resins, rosin resins, alkylphenol resins, and terpene phenol resins.

[0075] Here, the C5 resin refers to a C5 synthetic petroleum resin, a solid polymer obtained by polymerizing a C5 fraction using a Friedel-Crafts catalyst such as AlCl3 or BF3. Specific examples include copolymers containing isoprene, cyclopentadiene, 1,3-pentadiene, and 1-pentene as main components, copolymers of 2-pentene and dicyclopentadiene, and polymers mainly containing 1,3-pentadiene. The C9 resin refers to a C9 synthetic petroleum resin, a solid polymer obtained by polymerizing a C9 fraction using a Friedel-Crafts catalyst such as AlCl3 or BF3. Specific examples include copolymers containing indene, methylindene, α-methylstyrene, vinyltoluene, etc. as main components. Furthermore, the C5-C9 resin refers to a C5-C9 synthetic petroleum resin, specifically a solid polymer obtained by polymerizing a C5-C9 fraction using a Friedel-Crafts catalyst such as AlCl3 or BF3. Examples include copolymers primarily composed of styrene, vinyltoluene, α-methylstyrene, and indene. In the present invention, a resin with a low content of C9 or higher components is preferred as the C5-C9 resin from the viewpoint of compatibility with the rubber component. Here, "low content of C9 or higher components" means that the content of C9 or higher components in the total resin is less than 50% by mass, preferably 40% by mass or less.

[0076] The dicyclopentadiene-based resin is a petroleum resin that uses dicyclopentadiene in the C5 fraction as a main raw material. Examples include the "Marukaretzu M" series (M-890A, M-845A, M-990A, etc.) manufactured by Maruzen Petrochemical Co., Ltd. Furthermore, the rosin-based resins include natural resin rosins such as gum rosin, tall oil rosin, and wood rosin contained in raw pine resin and tall oil, and modified rosins, rosin derivatives, and modified rosin derivatives such as polymerized rosin and partially hydrogenated rosin thereof; glycerin ester rosin and partially hydrogenated rosin thereof and fully hydrogenated rosin thereof; pentaerythritol ester rosin and partially hydrogenated rosin thereof and polymerized rosin.

[0077] The alkylphenol resin is a phenol resin having an alkyl group, and examples thereof include alkylphenol-acetylene resins such as p-tert-butylphenol-acetylene resin, and alkylphenol-formaldehyde resins with a low degree of polymerization. Furthermore, the terpene phenol resin is a resin that can be obtained by reacting terpenes with various phenols using a Friedel-Crafts catalyst or by further condensing them with formalin. There are no particular restrictions on the terpenes used as raw materials, but monoterpene hydrocarbons such as α-pinene and limonene are preferred, with those containing α-pinene being more preferred, and α-pinene being particularly preferred. In the present invention, terpene phenol resins with a high phenol content are preferred. These resins can be used alone or in combination of two or more. Furthermore, the phenolic resin preferably contains a novolac phenolic resin, which can increase the elastic modulus of the rubber composition and improve handling stability without using a curing agent and without deteriorating wet performance.

[0078] The content of the thermoplastic resin is not particularly limited, but from the viewpoint of improving processability and braking performance when applied to a tire while not deteriorating abrasion resistance and reinforcement, it is preferably 3 to 50 parts by mass, and more preferably 5 to 30 parts by mass, per 100 parts by mass of the rubber component.

[0079] The antiaging agent may be any known agent and is not particularly limited. Examples include phenol-based antiaging agents, imidazole-based antiaging agents, and amine-based antiaging agents. These antiaging agents may be used alone or in combination of two or more.

[0080] The crosslinking accelerator may be any known accelerator and is not particularly limited. Examples include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole and dibenzothiazyl disulfide; sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazyl sulfenamide and Nt-butyl-2-benzothiazyl sulfenamide; guanidine-based vulcanization accelerators such as diphenyl guanidine; thiuram-based vulcanization accelerators such as tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, tetrabutyl thiuram disulfide, tetradodecyl thiuram disulfide, tetraoctyl thiuram disulfide, tetrabenzyl thiuram disulfide, and dipentamethylene thiuram tetrasulfide; dithiocarbamate-based vulcanization accelerators such as zinc dimethyldithiocarbamate; and zinc dialkyldithiophosphate. These crosslinking accelerators may be used alone or in combination.

[0081] The crosslinking agent is not particularly limited, and examples thereof include sulfur, bismaleimide compounds, etc. These crosslinking agents can be used alone or in combination of two or more. Examples of the bismaleimide compound include N,N'-o-phenylene bismaleimide, N,N'-m-phenylene bismaleimide, N,N'-p-phenylene bismaleimide, N,N'-(4,4'-diphenylmethane)bismaleimide, 2,2-bis-[4-(4-maleimidophenoxy)phenyl]propane, bis(3-ethyl-5-methyl-4-maleimidophenyl)methane, etc. In the present invention, N,N'-m-phenylene bismaleimide and N,N'-(4,4'-diphenylmethane)bismaleimide, etc., can be preferably used.

[0082] Examples of the crosslinking accelerator aid include zinc oxide (ZnO) and fatty acids. The fatty acid may be saturated or unsaturated, linear or branched, and the number of carbon atoms of the fatty acid is not particularly limited. Examples include fatty acids having 1 to 30 carbon atoms, preferably 15 to 30 carbon atoms. More specifically, naphthenic acids such as cyclohexanoic acid (cyclohexanecarboxylic acid) and alkylcyclopentanes having side chains; saturated fatty acids such as hexanoic acid, octanoic acid, decanoic acid (including branched carboxylic acids such as neodecanoic acid), dodecanoic acid, tetradecanoic acid, hexadecanoic acid, and octadecanoic acid (stearic acid); unsaturated fatty acids such as methacrylic acid, oleic acid, linoleic acid, and linolenic acid; and resin acids such as rosin, tall oil acid, and abietic acid. These may be used alone or in combination. In the present invention, zinc oxide or stearic acid is preferably used.

[0083] The method for producing the rubber composition of the present invention is not particularly limited, and the rubber composition can be obtained by blending and kneading the components that make up the rubber composition (rubber component, filler, and other components).

[0084] <Tires> The tire of the present invention is characterized by using the above-mentioned rubber composition of the present invention. By using the rubber composition of the present invention as a tire material, the resulting tire can be significantly improved in handling stability and rolling resistance. Specifically, in the tire of the present invention, the above-mentioned rubber composition is applied to any of the components, but among such tire components, it is particularly preferable to apply it to the tread. A tire using the above-mentioned rubber composition in the tread can achieve a high level of reinforcement (and thus abrasion resistance, handling stability, etc.) in addition to the effect of reducing rolling resistance. The gas to be filled into the tire of the present invention can be normal air or air with a modified oxygen partial pressure, or an inert gas such as nitrogen. [Example]

[0085] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0086] <Example 1, Comparative Example 1> A sample of each rubber composition is prepared according to the component composition in Table 1. The compounding amount of each component is shown in parts by mass relative to 100 parts by mass of the rubber component.

[0087] "Modified SBR-1" and "Modified SBR-2" in Table 1 are prepared under the following conditions. (Preparation of modified SBR-1) A cyclohexane solution of 1,3-butadiene and a cyclohexane solution of styrene were added to a dried, nitrogen-purged 800 mL pressure-resistant glass vessel so that the total weight of the mixture was 67.5 g of 1,3-butadiene and 7.5 g of styrene. 0.6 mmol of 2,2-ditetrahydrofurylpropane and 0.8 mmol of n-butyllithium were then added, and polymerization was carried out at 50°C for 1.5 hours. When the polymerization conversion rate reached nearly 100%, 0.72 mmol of [N,N-bis(trimethylsilyl)-(3-amino-1-propyl)](methyl)(diethoxy)silane was added, and the modification reaction was carried out at 50°C for 30 minutes. The reaction was then terminated by adding 2 mL of a 5% by weight solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol, and the mixture was dried according to standard methods to obtain modified SBR-1. Furthermore, the microstructure of the resulting modified SBR-1 was measured, and the results showed that the bound styrene content was 10% by mass, the vinyl content of the butadiene moiety was 40%, and the peak molecular weight in terms of polystyrene obtained by gel permeation chromatography was 200,000.

[0088] (Example of manufacturing a modifier) Two vacuum-dried 4L stainless steel pressure vessels were prepared. 944g of cyclohexane, 161g of the compound represented by the following chemical formula 2-1, and 86g of tetramethylethylenediamine were charged into the first pressure vessel to produce a first reaction solution. Simultaneously, 318g of 20wt% liquid n-butyllithium and 874g of cyclohexane were charged into the second pressure vessel to produce a second reaction solution. The molar ratio of the compound represented by the following chemical formula (2-1), n-butyllithium, and tetramethylethylenediamine was 1:1:1. With the pressure in each pressure vessel maintained at 7 bar, the first reaction solution was injected into the first continuous channel at a rate of 1.0g / min using a mass flow meter, and the second reaction solution was injected into the second continuous channel at a rate of 1.0g / min. During this time, the temperature of the continuous reactor is maintained at -10°C, the internal pressure is maintained at 3 bar using a backpressure regulator, and the residence time in the reactor is adjusted to within 10 minutes. The reaction is terminated to obtain the modified initiator. [ka] (Preparation of modified SBR-2) Into the first reactor of the series reactor in which three reactors are connected in series, 0.84 kg / h of a styrene solution in which styrene was dissolved in n-hexane at 60 wt%, 15.10 kg / h of a 1,3-butadiene solution in which 1,3-butadiene was dissolved in n-hexane at 60 wt%, 47.66 kg / h of n-hexane, 10 g / h of a 1,2-butadiene solution in which 1,2-butadiene was dissolved in n-hexane at 2.0 wt%, 10.0 g / h of a solution in which 2,2-(di-2(tetrahydrofuryl)propane was dissolved in n-hexane at 10 wt% as a polar additive, and 292.50 g / h of the modified initiator prepared in the above Preparation Example were injected. During this time, the temperature of the first reactor was maintained at 50°C, and when the polymerization conversion rate reached 43%, the polymer was transferred from the first reactor to the second reactor through the transfer pipe. Subsequently, a 1,3-butadiene solution in which 1,3-butadiene was dissolved in n-hexane at a concentration of 60 wt% was injected into the second reactor at a rate of 0.68 kg / h. At this time, the temperature of the second reactor was maintained at 65°C, and when the polymerization conversion rate reached 95% or more, the polymer was transferred from the second reactor to the third reactor through the transfer pipe. The polymer is transferred from the second reactor to the third reactor, and a solution of the following formula (1a) dissolved as a modifier is added to the third reactor (modifier:act. Li=1:1 mol). The temperature of the third reactor is maintained at 65°C. [ka] Then, a 30 wt% solution of IR1520 (BASF) as an antioxidant is added to the polymer solution discharged from the third reactor at a rate of 170 g / h and stirred. The resulting polymer is then added to steam-heated water and stirred to remove the solvent, yielding modified SBR-2. Measurement of the microstructure of the resulting modified SBR-2 revealed that the styrene content was 5% by mass and the vinyl content of the butadiene moiety was 37%.

[0089] <Evaluation> The following evaluations were carried out on the obtained rubber composition samples of Example 1 and Comparative Example 1. The results are shown in Table 1.

[0090] (1) Low heat generation The loss tangent (tanδ) of each sample was measured using a high-frequency dynamic viscoelasticity measuring device manufactured by Metravib under conditions of a temperature of 30°C, a strain of 5%, and a frequency of 15 Hz. The obtained tanδ values ​​were expressed as an index, with the value of Comparative Example 1 being set at 100, and are shown in Table 1. The smaller the tanδ index value, the better the low heat buildup property.

[0091] (2) Steering stability For each sample, the storage shear modulus G' (Pa) is measured under conditions of 30°C, 10% strain, and 15 Hz using a high-frequency dynamic viscoelasticity measuring device manufactured by Metravib. The obtained G' values ​​are expressed as index values ​​with the value of Comparative Example 1 set to 100, and are shown in Table 1. Note that a larger G' index value indicates better handling stability when applied to a tire.

[0092] [Table 1]

[0093] *1: Natural rubber, RSS#3 *2: Asahi Carbon Co., Ltd. "#80" *3: "Nipsil HQ-N" manufactured by Tosoh Silica Corporation *4: “T-REZ RD104” manufactured by Tonen Chemical LLC *5: Kiri Stearic Acid, manufactured by NOF Corporation *6: "Zinc oxide type 2" manufactured by Hakusui Tech Co., Ltd. *7: Idemitsu Kosan Co., Ltd.'s "Diana Process NH-70S" *8: "Suntite A" manufactured by Seiko Chemical Co., Ltd. *9: "Antigen 6C" manufactured by Sumitomo Chemical Co., Ltd. *10: Shin-Etsu Chemical Co., Ltd. "ABC-856", bis-triethoxysilylpropyl-polysulfide *11: "Nonflex RD-S" manufactured by Seiko Chemical Co., Ltd. *12: "Soccinol DG" manufactured by Sumitomo Chemical Co., Ltd. *13: Sansera DM-TG manufactured by Sanshin Chemical Industry Co., Ltd. *14: "Noccela NS-P" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. *15: "HK200-5" manufactured by Hosoi Chemical Industry Co., Ltd. *16: "Actiplast (registered trademark) PP" manufactured by LANXESS *17: HAMBURG STRUCTOL "VP1405"

[0094] The results in Table 1 show that the sample of Example 1, which contains a modified copolymer modified with a modifying agent containing a compound represented by formula (1) and has a low vinyl unit content, received higher ratings in both low heat buildup and handling stability than the sample of Comparative Example 1. [Industrial Applicability]

[0095] According to the present invention, a rubber composition can be provided that achieves excellent low heat buildup while maintaining good handling stability when applied to a tire. Also, according to the present invention, a tire can be provided that has improved rolling resistance and handling stability.

Claims

1. A rubber composition comprising a rubber component containing a copolymer having a conjugated diene unit and an aromatic vinyl unit, and a filler, The filler contains at least silica, the content of the filler is 10 to 160 parts by mass based on 100 parts by mass of the rubber component, The copolymer is a modified copolymer having a content of aromatic vinyl units of less than 10% by mass and modified with a modifier containing a compound represented by any one of formulas (1a) to (1e). 【Chemical 1】 【change】

2. The rubber composition according to claim 1, wherein the rubber component further contains a conjugated diene rubber different from the modified copolymer.

3. 3. The rubber composition according to claim 1, wherein the content of the aromatic vinyl unit in the copolymer is 8% by mass or less.

4. The copolymer is a modified copolymer further modified with a modifier containing a compound represented by formula (2). The rubber composition according to any one of claims 1 to 3. 【Chemistry 3】 (In formula (2), R １ ~R ３ are each independently hydrogen; an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms, a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms; ４ is a single bond; a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituted or unsubstituted arylene group having 5 to 20 carbon atoms, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms; R ５ is an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; a heterocyclic group having 3 to 30 carbon atoms; or a functional group represented by the following chemical formula (2a) or chemical formula (2b), where n is an integer of 1 to 5, and R ５ At least one of the functional groups is represented by the following chemical formula (2a) or (2b), and when n is an integer of 2 to 5, a plurality of R ５ may be the same as or different from each other. 【Chemistry 4】 In formula (2a), R ６ represents a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms; R ７ and R ８ are each independently an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an alkylene group having 1 to 20 carbon atoms which is substituted or unsubstituted with an aryl group having 6 to 20 carbon atoms, and R ９ is hydrogen; an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms; and X is an N, O, or S atom. When X is O or S, R ９ does not exist. 【Chemistry 5】 In formula (2b), R １０ is a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms; R １１ and R １２ are each independently an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms.

5. A tire comprising the rubber composition according to any one of claims 1 to 4.

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