Rubber composition for tire and tire

Abstract

To provide a rubber composition for tires and a tire, which are excellent in low temperature embrittlement resistance and silica reinforcement property capable of achieving both rubber hardness and low exothermic property at an excellent level and silica reinforcement when formed into a cured product.SOLUTION: A rubber composition comprises, with respect to a 100 pts.mass of a rubber component containing 10 pts. mass or more of a hydrogenated aromatic vinyl-conjugated diene copolymer with a weight average molecular weight of 200,000 or more: 10 pts.mass or more of silica with a CTAB adsorption specific surface area of 60 to 250 m2 / g; a silane coupling agent; and 0.5 to 20 pts.mass of a modified butadiene polymer or modified styrene-butadiene polymer having at least one functional group selected from groups consisting of amino groups, hydroxyl groups, alkoxysilyl groups, and functional group containing nitrogen atoms and silicon atoms, in the side chains or terminal groups, with a weight average molecular weight of 1,000 to 100,000 and a molecular weight distribution of 2.0 or less, in which a content of the silane coupling agent is 1 to 15 mass% of the silica content.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rubber composition for tires and a tire.

Background Art

[0002] In order to reduce the environmental load, weight reduction and low heat generation of tires are required. On the other hand, a method for producing a rubber composition for tires, which kneads a hydrogenated (hydrogenated) aromatic vinyl-conjugated diene copolymer or the like, is known (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the present inventors examined a cured product obtained from a rubber composition containing a hydrogenated aromatic vinyl-conjugated diene copolymer, silica, etc., they found that while the cured product can achieve both excellent hardness (rubber hardness) and low heat generation, the low-temperature embrittlement of the cured product may deteriorate (i.e., the embrittlement temperature may increase), or there may be room for improvement in the reinforcing property of silica. When a cured product with excellent hardness (rubber hardness) is used for a tire, the tire can be lightened. Further, when a liquid rubber was added to the above rubber composition and a cured product obtained from such a rubber composition was examined, it was found that the cured product could not achieve both its hardness (rubber hardness) and low heat generation, and the reinforcing property of silica may decrease.

[0005] Therefore, an object of the present invention is to provide a rubber composition for tires that can achieve both excellent rubber hardness and low heat build-up at a high level when cured, and has excellent low-temperature embrittlement resistance (i.e., can suppress an increase in the embrittlement temperature; the same applies to low-temperature embrittlement resistance hereinafter) and excellent silica reinforcement. Another object of the present invention is to provide a tire.

Means for Solving the Problems

[0006] As a result of intensive studies to solve the above problems, the present inventors have found that the problems can be solved by the following configuration.

[0007] [1] Based on 100 parts by mass of a rubber component containing 10 parts by mass or more of a hydrogenated aromatic vinyl-conjugated diene copolymer having a weight average molecular weight of 200,000 or more, 10 parts by mass or more of silica having a CTAB adsorption specific surface area of 60 to 250 m 2 / g, a silane coupling agent, 0.5 to 20 parts by mass of a modified butadiene polymer or a modified styrene-butadiene polymer having at least one functional group selected from the group consisting of an amino group, a hydroxy group, an alkoxysilyl group, and a functional group containing a nitrogen atom and a silicon atom in its side chain or terminal, having a weight average molecular weight of 1,000 to 100,000, and a molecular weight distribution of 2.0 or less, A rubber composition for tires, wherein the content of the silane coupling agent is 1 to 15% by mass of the content of the silica. [2] The rubber composition for tires according to [1], wherein the CTAB adsorption specific surface area is 60 to 170 m 2 / g. [3] The rubber composition for tires according to [1] or [2], wherein the hydrogenation rate of the hydrogenated aromatic vinyl-conjugated diene copolymer is 60 mol% or more. [4] The rubber composition for tires according to any one of [1] to [3], wherein the rubber component further contains 10 parts by mass or more of an isoprene-based rubber. [5] The rubber composition for a tire according to any one of [1] to [4], wherein the modified butadiene polymer or the modified styrene-butadiene polymer has a functional group containing a nitrogen atom and a silicon atom at its terminal. [6] A tire in which at least one selected from the group consisting of a tread, a sidewall, and a rim cushion is formed of the rubber composition for a tire according to any one of [1] to [5]. [Advantages of the Invention]

[0008] According to the present invention, it is possible to provide a rubber composition for a tire that can achieve both excellent rubber hardness and low heat build-up at an excellent level when it becomes a cured product, has excellent low-temperature brittleness resistance, and has excellent reinforcing properties of silica. Further, the present invention can also provide a tire. [Brief Description of the Drawings]

[0009]

Figure 1

[0010] Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be made based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In this specification, a numerical range represented by "~" means a range including the numerical values described before and after "~" as a lower limit value and an upper limit value. In this specification, each component can be used alone or in combination of two or more. In this specification, when a certain component is used in combination of two or more, the "content" of that component means the total content of those two or more unless otherwise specified. In this specification, the production method of each component is not particularly limited unless otherwise specified. For example, conventionally known methods can be mentioned.

[0011] [Rubber Composition for Tires] Hereinafter, the rubber composition for tires (the rubber composition of the present invention) of the present invention will be described in detail. The rubber composition for tires of the present invention is Based on 100 parts by mass of the rubber component containing 10 parts by mass or more of a hydrogenated aromatic vinyl-conjugated diene copolymer having a weight average molecular weight of 200,000 or more, 10 parts by mass or more of silica having a CTAB adsorption specific surface area of 60 to 250 m 2 / g, a silane coupling agent, and 0.5 to 20 parts by mass of a modified butadiene polymer or a modified styrene-butadiene polymer having at least one functional group selected from the group consisting of an amino group, a hydroxy group, an alkoxysilyl group, and a functional group containing a nitrogen atom and a silicon atom in the side chain or at the terminal, having a weight average molecular weight of 1,000 to 100,000, and a molecular weight distribution of 2.0 or less. The rubber composition for tires is such that the content of the above silane coupling agent is 1 to 15% by mass of the content of the above silica.

[0012] In this specification, a hydrogenated aromatic vinyl-conjugated diene copolymer having a weight average molecular weight of 200,000 or more may be referred to as a "specific hydrogenated copolymer". Also, in this specification, a modified butadiene polymer having at least one functional group selected from the group consisting of an amino group, a hydroxy group, an alkoxysilyl group, and a functional group containing a nitrogen atom and a silicon atom in the side chain or at the terminal, having a weight average molecular weight of 1,000 to 100,000, and a molecular weight distribution of 2.0 or less may be referred to as a "specific modified butadiene polymer" or a "specific modified BR". In this specification, a modified styrene-butadiene polymer having at least one functional group selected from the group consisting of an amino group, a hydroxy group, an alkoxysilyl group, and a functional group containing a nitrogen atom and a silicon atom in the side chain or at the terminal, having a weight average molecular weight of 1,000 to 100,000, and a molecular weight distribution of 2.0 or less may be referred to as a "specific modified styrene-butadiene polymer" or a "specific modified SBR". In this specification, the specific modified butadiene polymer and the specific modified styrene-butadiene polymer may be collectively referred to as the "specific modified polymer". In this specification, at least one functional group selected from the group consisting of an amino group, a hydroxy group, an alkoxysilyl group, and a functional group containing a nitrogen atom and a silicon atom, which the specific modified polymer has, may be referred to as the "specific functional group". In this specification, the CTAB adsorption specific surface area (cetyltrimethylammonium bromide adsorption specific surface area) may be simply referred to as "CTAB". In this specification, that at least one of rubber hardness, low heat build-up property, low temperature brittleness resistance, and silica reinforcement property is more excellent is also referred to as "the effect of the present invention is more excellent".

[0013] The reason why the rubber composition of the present invention having the above configuration can solve the problems of the present invention is not necessarily clear, but the present inventors presume as follows. Note that the mechanism by which the effect is obtained is not limited by the following presumption. In other words, even when the effect is obtained by a mechanism other than the following, it is included in the scope of the present invention. The rubber composition of the present invention contains the above specific modified polymer, so that when it becomes a cured product, rubber hardness and low heat build-up property can be compatible at an excellent level, and excellent silica reinforcement property is exhibited. This is presumably because the dispersibility of silica in the rubber composition of the present invention is improved by containing the above specific modified polymer in the rubber composition of the present invention. In addition, when the above specific modified polymer is added to the hydrogenated aromatic vinyl-conjugated diene copolymer, the present inventors have found that an unexpected effect is obtained with respect to the improvement of low temperature brittleness resistance as compared with the case where the above specific modified polymer is added to the unhydrogenated aromatic vinyl-conjugated diene copolymer.

[0014] [Rubber component] In the rubber composition of the present invention, the rubber component includes a hydrogenated aromatic vinyl-conjugated diene copolymer (specific hydrogenated copolymer) having a weight average molecular weight of 200,000 or more. In the rubber composition of the present invention, the rubber component does not contain a specific modified polymer.

[0015] [Hydrogenated aromatic vinyl-conjugated diene copolymer having a weight average molecular weight of 200,000 or more] The specific hydrogenated copolymer contained in the rubber composition of the present invention is a rubber component obtained by hydrogenating an aromatic vinyl-conjugated diene copolymer. In the present specification, when simply described as "aromatic vinyl-conjugated diene copolymer", the "aromatic vinyl-conjugated diene copolymer" refers to the aromatic vinyl-conjugated diene copolymer before hydrogenation.

[0016] (Aromatic vinyl-conjugated diene copolymer) The aromatic vinyl-conjugated diene copolymer (before hydrogenation) is a copolymer of an aromatic vinyl and a conjugated diene, and is preferably a random copolymer for the reason that the effects of the present invention are more excellent. Examples of the aromatic vinyl compound constituting the aromatic vinyl-conjugated diene copolymer include styrene, methylstyrene, ethylstyrene, t-butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, chlorostyrene, bromostyrene, methoxystyrene, dimethylaminomethylstyrene, dimethylaminoethylstyrene, diethylaminomethylstyrene, diethylaminoethylstyrene, cyanoethylstyrene, vinylnaphthalene, etc. Among these, styrene is preferred. Examples of the conjugated diene compound constituting the aromatic vinyl-conjugated diene copolymer include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, etc. Among these, 1,3-butadiene and isoprene are preferred. Examples of the aromatic vinyl-conjugated diene copolymer include styrene-butadiene copolymer rubber (SBR), styrene-isoprene copolymer rubber, etc. In addition to the aromatic vinyl compound and the conjugated diene compound, the aromatic vinyl-conjugated diene copolymer may optionally use other copolymerizable monomers. The polymerization method of the aromatic vinyl-conjugated diene copolymer may use any of solution polymerization method, gas phase polymerization method, and bulk polymerization method, but the solution polymerization method is preferred. Also, as the polymerization form, either batch type or continuous type may be used.

[0017] (Vinyl content of the aromatic vinyl-conjugated diene copolymer) As a microstructure, the vinyl content (in the aromatic vinyl-conjugated diene copolymer, the amount of vinyl bonds such as 1,2-bonds in the conjugated diene part) in the conjugated diene part of the aromatic vinyl-conjugated diene copolymer is preferably 5 to 70% by mass, more preferably 15 to 65% by mass, and still more preferably 20 to 60% by mass. When the conjugated diene in the aromatic vinyl-conjugated diene copolymer is, for example, 1,3-butadiene, the conjugated diene part as a microstructure in the aromatic vinyl-conjugated diene copolymer consists of repeating units of cis-1,4 bond, trans-1,4 bond, and 1,2-bond, and the percentage (mass%) of 1,2-bond in the total 100% by mass of these is referred to as the vinyl content. When the conjugated diene in the aromatic vinyl-conjugated diene copolymer is, for example, isoprene, the conjugated diene part as a microstructure in the aromatic vinyl-conjugated diene copolymer consists of repeating units of cis-1,4 bond, trans-1,4 bond, 1,2-bond, and 3,4-bond, and the percentage (mass%) of 1,2-bond and 3,4-bond in the total 100% by mass of these is referred to as the vinyl content. In the present invention, the vinyl content, cis-1,4 bond, and trans-1,4 bond (mass%) of the conjugated diene part of the specific hydrogenated copolymer and the conjugated diene part of the aromatic vinyl-conjugated diene copolymer are 1 measurable by 1H-NMR.

[0018] (Hydrogenation of the aromatic vinyl-conjugated diene copolymer) The hydrogenated aromatic vinyl-conjugated diene copolymer (specific hydrogenated copolymer) is mentioned as one of the preferred embodiments in which the above-mentioned conjugated diene part of the raw material aromatic vinyl-conjugated diene copolymer is hydrogenated. In addition, the hydrogenated aromatic vinyl-conjugated diene copolymer (specific hydrogenated copolymer) is one of the preferred embodiments in which the aromatic vinyl portion (aromatic hydrocarbon group in the repeating unit formed by aromatic vinyl) of the aromatic vinyl-conjugated diene copolymer as a raw material is not hydrogenated.

[0019] The method and conditions for the hydrogenation (hydrogen addition) reaction of the aromatic vinyl-conjugated diene polymer are not particularly limited. Examples of the hydrogenation method of the aromatic vinyl-conjugated diene polymer include a method using a catalyst mainly composed of an organometallic compound of titanium as a hydrogenation catalyst, a method using a catalyst composed of an organic compound of iron, nickel, cobalt and an organometallic compound such as alkylaluminum, a method using an organic complex of an organometallic compound such as ruthenium and rhodium, and a method using a catalyst in which metals such as palladium, platinum, ruthenium, cobalt and nickel are supported on a carrier such as carbon, silica and alumina.

[0020] (Hydrogenation rate of the specific hydrogenated copolymer) The hydrogenation rate (hydrogenation rate) of the specific hydrogenated copolymer is preferably 60 mol% or more, more preferably 60 to 90 mol%, and still more preferably 60 to 80 mol% for the reason that the effects of the present invention are more excellent. The specific hydrogenated copolymer is one of the preferred embodiments in which its hydrogenation rate is less than 100 mol%. When the hydrogenation rate is less than 100 mol%, it is preferable because crosslinkability can be imparted to the specific hydrogenated copolymer. In this specification, the hydrogenation rate refers to the percentage (%) of the hydrogenated carbon-carbon bond portion with respect to a total of 100 mol% of the carbon-carbon double bond portions before hydrogenation in the conjugated diene portion of the aromatic vinyl-conjugated diene copolymer. A hydrogenation rate of 100 mol% means that the carbon-carbon double bonds in the conjugated diene portion are completely hydrogenated. The hydrogenation rate can be calculated from the spectral reduction rate of the unsaturated bond portion in the conjugated diene portion of the spectrum obtained by measuring 1H-NMR. 1 It can be calculated from the spectral reduction rate of the unsaturated bond portion in the conjugated diene portion of the spectrum obtained by measuring 1H-NMR.

[0021] (Content of the repeating unit derived from the aromatic vinyl compound as the microstructure of the specific hydrogenated copolymer) The content of the repeating unit derived from the aromatic vinyl compound in the specific hydrogenated copolymer is not particularly limited, but is preferably 50% by mass or less, more preferably 1 to 45% by mass, and even more preferably 2 to 40% by mass. For example, when the aromatic vinyl compound is styrene, the amount of styrene in the hydrogenated styrene-conjugated diene copolymer being 50% by mass or less is cited as one of the preferred embodiments. In addition, the content (mass%) of the repeating unit derived from the aromatic vinyl compound in the aromatic vinyl-conjugated diene copolymer can be the same as described above. In the present specification, the content (mass%) of the repeating unit derived from the aromatic vinyl compound in the specific hydrogenated copolymer and in the aromatic vinyl-conjugated diene copolymer 1 can be measured by 1H-NMR.

[0022] In the specific hydrogenated copolymer, one of the preferred embodiments is that any of the repeating units such as cis-1,4 bond, trans-1,4 bond, 1,2-bond, etc. in the conjugated diene portion of the aromatic vinyl-conjugated diene copolymer before hydrogenation as the raw material is hydrogenated. The range of the hydrogenated vinyl amount in the conjugated diene portion of the specific hydrogenated copolymer can be part or all of the range of the vinyl amount in the conjugated diene portion described above for the aromatic vinyl-conjugated diene copolymer before hydrogenation. In the present specification, the hydrogenated vinyl group or unhydrogenated vinyl group (mol%) in the conjugated diene portion of the specific hydrogenated copolymer 1 can be measured by 1H-NMR.

[0023] [Weight-average molecular weight of the specific hydrogenated copolymer] In the rubber composition of the present invention, the weight-average molecular weight of the specific hydrogenated copolymer is 200,000 or more. By the weight-average molecular weight of the specific hydrogenated copolymer being 200,000 or more, the rubber hardness and tensile fracture properties (tensile fracture strength and / or elongation at break) of the cured product obtained from the rubber composition of the present invention can be increased. The weight average molecular weight of the specific hydrogenated copolymer is preferably from 200,000 to 700,000, more preferably from 300,000 to 600,000, because the effects of the present invention are more excellent, the viscosity of the rubber composition of the present invention becomes appropriate, and the processability is excellent. In addition, the weight average molecular weight of the aromatic vinyl-conjugated diene copolymer can be the same as described above. In this specification, the weight average molecular weights of the hydrogenated specific copolymer and the aromatic vinyl-conjugated diene copolymer can be values in terms of polystyrene measured by gel permeation chromatography (GPC) under the following conditions. · Solvent: Tetrahydrofuran · Detector: RI detector

[0024] (Glass transition temperature of the specific hydrogenated copolymer) The glass transition temperature of the specific hydrogenated copolymer is preferably -40°C or lower, more preferably from -80°C to -40°C, and still more preferably from -75°C to -40°C, because the effects of the present invention are more excellent and sufficient flexibility can be ensured even in use in cold regions. In this specification, the glass transition temperature can be the temperature at the midpoint of the transition region by measuring a thermogram by differential scanning calorimetry (DSC) under the condition of a heating rate of 20°C / min.

[0025] [Content of the specific hydrogenated copolymer] In the rubber composition of the present invention, 100 parts by mass of the above rubber component (100 parts by mass which is the total amount of the rubber component; the same applies hereinafter) contains 10 parts by mass or more of the specific hydrogenated copolymer. That is, the content of the specific hydrogenated copolymer is 10 parts by mass or more in 100 parts by mass of the above rubber component. All of the rubber components may be the specific hydrogenated copolymer. The content of the specific hydrogenated copolymer is preferably from 20 to 90 parts by mass, more preferably from 40 to 80 parts by mass, in 100 parts by mass of the above rubber component, because the effects of the present invention are more excellent.

[0026] (Other rubber components) The above rubber component can further contain a rubber component other than the specific hydrogenated copolymer (other rubber components). Examples of the other rubber components include diene rubbers such as isoprene-based rubbers, unhydrogenated aromatic vinyl-conjugated diene copolymers (such as styrene-butadiene rubber), butadiene rubber, butyl rubber, halogenated butyl rubber, and acrylonitrile-butadiene rubber. The content of the other rubber component can be 0 to 90% by mass in 100 parts by mass of the rubber component. When the rubber component further contains the other rubber component, the content of the other rubber component in the total amount of the rubber component can be the remainder obtained by subtracting the content of the above specific hydrogenated copolymer from the total amount of the rubber component.

[0027] (Isoprene-based rubber) The rubber component preferably further contains an isoprene-based rubber as the other rubber component because the effects of the present invention are more excellent and the processability of the unvulcanized rubber is excellent. Further, since the isoprene-based rubber has the property of being incompatible (or hardly compatible) with the specific hydrogenated copolymer and the specific modified polymer, when the rubber component further contains the isoprene-based rubber, in the matrix formed by the rubber component, the characteristic modified polymer can be more unevenly distributed in the phase of the specific hydrogenated copolymer than when the rubber component further contains a rubber compatible with the specific hydrogenated copolymer or the specific modified polymer. Therefore, it is considered that the effects of the present invention are more effectively exhibited. Examples of the rubber compatible with the specific hydrogenated copolymer or the specific modified polymer include a liquid butadiene polymer (excluding the characteristic modified BR) and a liquid styrene-butadiene polymer (excluding the specific modified SBR). Examples of the isoprene-based rubber include natural rubber, epoxidized natural rubber, and isoprene rubber (synthetic isoprene rubber). When the rubber component further contains the isoprene-based rubber, the content of the isoprene-based rubber is preferably 10 parts by mass or more, more preferably 10 to 80 parts by mass, and still more preferably 20 to 60 parts by mass in 100 parts by mass of the rubber component because the effects of the present invention are more excellent and the processability of the unvulcanized rubber is excellent.

[0028] The rubber component contained in the rubber composition of the present invention is preferably solid under the condition of 23°C, which is an exemplary embodiment.

[0029] [Silica] The rubber composition of the present invention contains silica having a CTAB adsorption specific surface area of 60 to 250 m 2 / g (silica having a CTAB adsorption specific surface area of 60 to 250 m 2 / g).

[0030] Examples of silica having a CTAB of 60 to 250 m 2 / g include wet-process silica, dry-process silica, surface-treated silica, and the like.

[0031] (CTAB of silica) The CTAB adsorption specific surface area of the above silica is preferably 60 to 170 m 2 / g for the reason that the effects of the present invention are more excellent. In this specification, the CTAB adsorption specific surface area of silica can be measured in accordance with JIS K6430:2008.

[0032] [Content of silica] The rubber composition of the present invention contains 10 parts by mass or more of silica having a CTAB adsorption specific surface area of 60 to 250 m 2 / g based on 100 parts by mass of the rubber component. The content of silica having a CTAB adsorption specific surface area of 60 to 250 m 2 / g is 10 to 180 parts by mass, more preferably 15 to 130 parts by mass, and even more preferably 20 to 90 parts by mass based on 100 parts by mass of the rubber component for the reason that the effects of the present invention are more excellent.

[0033] [Silane coupling agent] The rubber composition of the present invention contains a silane coupling agent. Examples of the silane coupling agent include sulfur-containing silane coupling agents such as bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)disulfide, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, and dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl-tetrasulfide. The silane coupling agent is mentioned as one of the preferred embodiments that preferably contains a sulfide-based silane coupling agent because the effects of the present invention are more excellent. The sulfide-based silane coupling agent is a silane coupling agent having a sulfide group (including a monosulfide group and a polysulfide group).

[0034] [Content of silane coupling agent] In the rubber composition of the present invention, the content of the silane coupling agent is 1 to 15% by mass of the content of the silica having a CTAB adsorption specific surface area of 60 to 250 m 2 / g. The content of the silane coupling agent is preferably 3 to 10% by mass of the content of the silica having a CTAB adsorption specific surface area of 60 to 250 m 2 / g because the effects of the present invention are more excellent.

[0035] [Specific modified polymer] The rubber composition of the present invention contains the above-mentioned modified butadiene polymer or modified styrene-butadiene polymer having at least one functional group selected from the group consisting of an amino group, a hydroxy group, an alkoxysilyl group, and a functional group containing a nitrogen atom and a silicon atom in a side chain or at a terminal, a weight average molecular weight of 1,000 to 100,000, and a molecular weight distribution of 2.0 or less. In the present invention, the modified butadiene polymer has a basic skeleton (portion other than the specific functional group) that is a butadiene polymer, and has at least one functional group (specific functional group) selected from the group consisting of an amino group, a hydroxy group, an alkoxysilyl group, and a functional group containing a nitrogen atom and a silicon atom, on the side chain or at the terminal. The modified butadiene polymer is a butadiene polymer. The weight average molecular weight of the modified butadiene polymer is 1,000 to 100,000. The molecular weight distribution of the modified butadiene polymer is 2.0 or less. In the modified butadiene polymer, any one of the total repeating units derived from butadiene constituting the basic skeleton may be modified by the specific functional group. The modified styrene-butadiene polymer has a basic skeleton (portion other than the specific functional group) that is a styrene-butadiene polymer, and has at least one functional group (specific functional group) selected from the group consisting of an amino group, a hydroxy group, an alkoxysilyl group, and a functional group containing a nitrogen atom and a silicon atom, on the side chain or at the terminal. The modified styrene-butadiene polymer is a styrene-butadiene copolymer. The weight average molecular weight of the modified styrene-butadiene polymer is 1,000 to 100,000. The molecular weight distribution of the modified styrene-butadiene polymer is 2.0 or less. In the modified styrene-butadiene polymer, any one of the total repeating units derived from styrene and butadiene constituting the basic skeleton may be modified by the specific functional group. Note that the modified butadiene polymer does not include the modified styrene-butadiene polymer. The rubber composition of the present invention may contain the modified butadiene polymer and the modified styrene-butadiene polymer.

[0036] [Specific functional group possessed by the specific modified polymer] In the rubber composition of the present invention, the specific modified polymer has at least one functional group (specific functional group) selected from the group consisting of an amino group, a hydroxy group, an alkoxysilyl group, and a functional group containing a nitrogen atom and a silicon atom. Examples of the amino group include a primary amino group (-NH2), a secondary amino group (-NH-), and a tertiary amino group (-N<). When a specific functional group contains an amino group, the amino group excludes a functional group containing a nitrogen atom and a silicon atom. The specific functional group preferably contains at least one selected from the group consisting of an alkoxysilyl group and a functional group containing a nitrogen atom and a silicon atom, and more preferably contains a functional group containing a nitrogen atom and a silicon atom, because the effects of the present invention are more excellent.

[0037] (Alkoxysilyl group) When the specific functional group contains an alkoxysilyl group, the alkoxysilyl group is a group in which 1 to 3 alkoxy groups are bonded to one silicon atom. The alkoxy group of the alkoxysilyl group is not particularly limited. For example, an alkoxy group having 1 to 6 carbon atoms such as a methoxy group and an ethoxy group can be mentioned. When 1 to 2 alkoxy groups are bonded to the silicon atom in the alkoxysilyl group, the alkoxysilyl group can further have an alkyl group having 1 to 6 carbon atoms. Examples of the alkoxysilyl group include a trialkoxysilyl group such as a trimethoxysilyl group and a triethoxysilyl group; a monoalkyldialkoxysilyl group; and a dialkylmonoalkoxysilyl group. When the specific functional group contains an alkoxysilyl group, the alkoxysilyl group excludes a functional group containing a nitrogen atom and a silicon atom.

[0038] (Functional group containing a nitrogen atom and a silicon atom) When the specific functional group contains a functional group containing a nitrogen atom and a silicon atom, the functional group containing a nitrogen atom and a silicon atom is not particularly limited as long as it is a functional group containing a nitrogen atom and a silicon atom. However, for the reason that the effects of the present invention are more excellent, it preferably contains a nitrogen atom as an amino group (-NR2: R is independently a hydrogen atom or a hydrocarbon group), and preferably contains a silicon atom as a hydrocarbyloxysilyl group (≡SiOR: R is a hydrocarbon group).

[0039] The functional group containing a nitrogen atom and a silicon atom is preferably a group represented by the following formula (M) because the effects of the present invention are more excellent.

[0040] [Chemical formula]

[0041] In the above formula (M), R1 and R2 each independently represent a hydrogen atom or a substituent. In the above formula (M), L represents a divalent organic group.

[0042] The above substituent is not particularly limited as long as it is a monovalent substituent. Examples thereof include a halogen atom, a hydroxy group, a nitro group, a carboxy group, an alkoxy group, an amino group, a mercapto group, an acyl group, an imide group, a phosphino group, a phosphinyl group, a silyl group, and a hydrocarbon group which may have a hetero atom. Examples of the above halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the hetero atom of the hydrocarbon group which may have the above hetero atom include an oxygen atom, a nitrogen atom, a sulfur atom, and a phosphorus atom. Examples of the hydrocarbon group which may have the above hetero atom include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or a group combining these. The above aliphatic hydrocarbon group may be linear, branched, or cyclic. Specific examples of the above aliphatic hydrocarbon group include a linear or branched alkyl group (particularly having 1 to 30 carbon atoms), a linear or branched alkenyl group (particularly having 2 to 30 carbon atoms), and a linear or branched alkynyl group (particularly having 2 to 30 carbon atoms). Examples of the above aromatic hydrocarbon group include aromatic hydrocarbon groups having 6 to 18 carbon atoms such as a phenyl group, a tolyl group, a xylyl group, and a naphthyl group.

[0043] In the above formula (M), for the reason that the effects of the present invention are more excellent, R1 is preferably a hydrogen atom, an alkyl group (preferably having 1 to 10 carbon atoms), an alkylsilyl group (preferably having 1 to 10 carbon atoms), or an aromatic hydrocarbon group (preferably having 6 to 18 carbon atoms), and more preferably a hydrogen atom. A plurality of R1s may be the same or different.

[0044] For the reason that the effects of the present invention are more excellent, R2 is preferably a hydrocarbyloxy group (-OR group: R is a hydrocarbon group), and more preferably an alkoxy group (preferably having 1 to 10 carbon atoms).

[0045] As described above, in the above formula (M), L represents a single bond or a divalent organic group. Examples of the divalent organic group include an aliphatic hydrocarbon group (for example, an alkylene group, preferably having 1 to 10 carbon atoms), an aromatic hydrocarbon group (for example, an arylene group, preferably having 6 to 18 carbon atoms), -O-, -S-, -SO2-, -N(R)- (R is an alkyl group), -CO-, -NH-, -COO-, -CONH-, or a group combining these (for example, an alkyleneoxy group (-C m H 2m O-: m is a positive integer), an alkyleneoxycarbonyl group, an alkylenecarbonyloxy group, etc.). For the reason that the effects of the present invention are more excellent, L is preferably an alkylene group (preferably having 1 to 10 carbon atoms).

[0046] In the above formula (M), n represents an integer from 0 to 2. For the reason that the effects of the present invention are more excellent, n is preferably 2.

[0047] In the above formula (M), m represents an integer from 1 to 3. For the reason that the effects of the present invention are more excellent, m is preferably 1.

[0048] In the above formula (M), n and m satisfy the relational expression n + m = 3.

[0049] In the above formula (M), * represents the bonding position.

[0050] Examples of the group represented by the above formula (M) include a functional group represented by the following formula (m1). [Chemical formula]

[0051] [Position of the specific functional group possessed by the specific modified polymer] In the rubber composition of the present invention, the specific modified polymer has a specific functional group in the side chain or at the terminal of the specific modified polymer. The specific modified polymer may have a specific functional group in both the side chain and at the terminal of the specific modified polymer. For the reason that the effects of the present invention are more excellent, it is preferable that the specific modified polymer has a specific functional group at least at the terminal of the specific modified polymer. In the specific modified polymer, the specific functional group can be bonded to the above basic skeleton of the specific modified polymer directly or via a linking group. The linking group is not particularly limited.

[0052] [Weight average molecular weight of the specific modified polymer] In the rubber composition of the present invention, the weight average molecular weight (Mw) of the specific modified polymer is 1,000 to 100,000. Among them, for the reason that the effects of the present invention are more excellent, it is preferably 5,000 or more and 20,000 or less, and more preferably 5,000 or more and 12,000 or less.

[0053] (Number average molecular weight of the specific modified polymer) The number average molecular weight (Mn) of the specific modified polymer is not particularly limited as long as the weight average molecular weight and the molecular weight distribution of the specific modified polymer are within a specific range. However, for the reason that the effects of the present invention are more excellent, it is preferably 1,000 or more and 100,000 or less, and more preferably 5,000 or more and 20,000 or less.

[0054] [Molecular weight distribution of the specific modified polymer] In the rubber composition of the present invention, the molecular weight distribution (Mw / Mn) of the specific modified polymer is 2.0 or less. Among them, for the reason that the effects of the present invention are more excellent, it is preferably 1.7 or less, and more preferably 1.6 or less. The lower limit of the molecular weight distribution of the specific modified polymer is not particularly limited, but is usually 1.0 or more. From the reason that the effects of the present invention are more excellent, the above lower limit is preferably 1.3 or more.

[0055] In addition, in this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) of the specific modified polymer are the standard polystyrene conversion values obtained by gel permeation chromatography (GPC) measurement under the following conditions. · Solvent: Tetrahydrofuran · Detector: RI detector

[0056] 〔Microstructure of specific modified BR〕 Hereinafter, the microstructure of the specific modified BR will be described. <Vinyl structure of specific modified BR> In the specific modified BR, the proportion of the vinyl structure is not particularly limited, but for the reason that the effects of the present invention are more excellent, it is preferably 10 to 50 mol%, and more preferably 20 to 45 mol%. Here, the proportion of the vinyl structure refers to the proportion (mol%) of the repeating unit having a vinyl structure among the repeating units derived from butadiene.

[0057] <1,4-trans structure of specific modified BR> In the specific modified BR, the proportion of the 1,4-trans structure is not particularly limited, but for the reason that the effects of the present invention are more excellent, it is preferably 30 to 70 mol%, and more preferably 35 to 60 mol%. Here, the proportion of the 1,4-trans structure refers to the proportion (mol%) of the repeating unit having a 1,4-trans structure among all the repeating units derived from butadiene.

[0058] <1,4-cis structure of specific modified BR> In the case of the specific modified BR, the proportion of the 1,4-cis structure is not particularly limited, but for the reason that the effects of the present invention are more excellent, it is preferably 20 to 60 mol%, and more preferably 20 to 45 mol%. Here, the proportion of the 1,4-cis structure refers to the proportion (mol%) occupied by the repeating unit having the 1,4-cis structure among all the repeating units derived from butadiene.

[0059] Hereinafter, among the repeating units derived from butadiene in the specific modified SBR, the "proportion of vinyl structure (mol%), proportion of 1,4-trans structure (mol%), proportion of 1,4-cis structure (mol%)" is also represented as "vinyl / trans / cis".

[0060] 〔Microstructure of specific modified SBR〕 Hereinafter, the microstructure of the specific modified SBR will be described. <Styrene content of specific modified SBR> The content of the repeating unit derived from styrene in the specific modified SBR (hereinafter, also referred to as "styrene content") is preferably 20% by mass or more in the specific modified SBR, and more preferably 25% by mass or more, for the reason that the effects of the present invention are more excellent. The upper limit is not particularly limited, but for the reason that the effects of the present invention are more excellent, it is preferably 90% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less.

[0061] <Butadiene content of specific modified SBR> The content of the repeating unit derived from butadiene in the specific modified SBR (hereinafter, also referred to as "butadiene content") is preferably 80% by mass or less in the specific modified SBR, and more preferably 75% by mass or less, for the reason that the effects of the present invention are more excellent. Also, the lower limit is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, for the reason that the effects of the present invention are more excellent.

[0062] <Vinyl structure of specific modified SBR> In the specific modified SBR, among the repeating units derived from butadiene, the proportion of the vinyl structure is preferably 10 to 50 mol%, more preferably 20 to 40 mol%, because the effects of the present invention and the like are more excellent. Here, the proportion of the vinyl structure means the proportion (mol%) of the repeating units having a vinyl structure (for example, a 1,2-vinyl structure when the diene is 1,3-butadiene) among all the repeating units derived from butadiene.

[0063] <1,4-Trans structure of specific modified SBR> In the specific modified SBR, among the repeating units derived from butadiene, the proportion of the 1,4-trans structure is preferably 30 to 70 mol%, more preferably 35 to 55 mol%, because the effects of the present invention and the like are more excellent. Here, the proportion of the 1,4-trans structure means the proportion (mol%) of the repeating units having a 1,4-trans structure among all the repeating units derived from butadiene.

[0064] <1,4-Cis structure of specific modified SBR> In the specific modified SBR, among the repeating units derived from butadiene, the proportion of the 1,4-cis structure is preferably 20 to 60 mol%, more preferably 25 to 45 mol%, because the effects of the present invention and the like are more excellent. Here, the proportion of the 1,4-cis structure means the proportion (mol%) of the repeating units having a 1,4-cis structure among all the repeating units derived from butadiene.

[0065] In the following, among the repeating units derived from butadiene in the specific modified SBR, "the proportion of the vinyl structure (mol%), the proportion of the 1,4-trans structure (mol%), the proportion of the 1,4-cis structure (mol%)" is also represented as "vinyl / trans / cis". In this specification, the microstructure of the specific modified polymer (the vinyl, trans, and cis structures of the butadiene component, and the proportion of styrene) was obtained by IR analysis.

[0066] [Glass transition temperature of the specific modified polymer] The glass transition temperature (Tg) of the specific modified polymer is not particularly limited, but for the reason that the effects of the present invention are more excellent, it is preferably -100 to -50 °C, more preferably -90 to -70 °C, and even more preferably -85 to -75 °C. In this specification, the glass transition temperature (Tg) is measured using a differential scanning calorimeter (DSC) at a heating rate of 10 °C / min and calculated by the midpoint method.

[0067] [Viscosity] The viscosity of the specific modified polymer (under the condition of 20 °C) is not particularly limited, but for the reason that the effects of the present invention are more excellent, it is preferably 1,000 to 10,000 mPa·s, and more preferably 3,000 to 6,000 mPa·s. Also, the viscosity of the polymer before modifying the specific modified polymer (the polymer before modification) (under the condition of 20 °C) is not particularly limited, but for the reason that the effects of the present invention are more excellent, it is preferably 500 to 5,000 mPa·s, and more preferably 1,500 to 3,000 mPa·s. Also, for the reason that the effects of the present invention are more excellent, the viscosity of the specific modified polymer (under the condition of 20 °C) is preferably 150 to 240% with respect to the viscosity of the polymer before modification (under the condition of 20 °C). Hereinafter, the ratio of the viscosity of the modified specific modified polymer to the viscosity of the polymer before modification is also referred to as "% of viscosity after modification / viscosity before modification". In this specification, the viscosity is measured using a cone-plate viscometer in accordance with JIS K5600-2-3:2014.

[0068] The specific modified polymer is preferably liquid under the condition of 23 °C for the reason that the effects of the present invention are more excellent.

[0069] [Production method of the specific modified polymer] The method for manufacturing a specific modified polymer is not particularly limited, and conventionally known methods can be used. The method for setting the molecular weight and molecular weight distribution within specific ranges is not particularly limited, and examples thereof include methods for adjusting the quantitative ratios of the initiator, monomer, and terminator, the reaction temperature, and the rate of adding the initiator.

[0070] <Preferred embodiment> As a preferred embodiment of the method for manufacturing a specific modified polymer, for example, a method of polymerizing butadiene or styrene and butadiene using an organolithium compound and then terminating the polymerization using an electrophile can be mentioned (hereinafter, the above embodiment is also referred to as "the preferred embodiment of the method for manufacturing a specific modified polymer"). When the specific modified polymer obtained using the preferred embodiment of the method for manufacturing a specific modified polymer is used in a rubber composition containing a specific hydrogenated copolymer, silica in which the above-mentioned CTAB is within a specific range, etc., it can exhibit more excellent rubber hardness, low heat build-up properties, low-temperature brittleness resistance, and reinforcing properties of silica.

[0071] (Organolithium compound) The above organolithium compound is not particularly limited, and specific examples thereof include mono-organolithium compounds such as n-butyllithium, sec-butyllithium, tert-butyllithium, n-propyllithium, isopropyllithium, and benzyllithium; polyfunctional organolithium compounds such as 1,4-dilithiobutane, 1,5-dilithiopentane, 1,6-dilithiohexane, 1,10-dilithiodecane, 1,1-dilithiodiphenylene, dilithiopolybutadiene, dilithiopolyisoprene, 1,4-dithiobenzene, 1,2-dithio-1,2-diphenylethane, 1,4-dithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, and 1,3,5-trilithio-2,4,6-triethylbenzene. Among them, mono-organolithium compounds such as n-butyllithium, sec-butyllithium, and tert-butyllithium are preferred because the effects of the present invention are more excellent.

[0072] The amount of the organolithium compound used is not particularly limited, but from the reason that the effects of the present invention are more excellent, it is preferably 0.001 to 10 mol% based on the total amount of butadiene, or styrene and butadiene.

[0073] (Polymerization of butadiene, or styrene and butadiene) The polymerization method of polymerizing butadiene using an organolithium compound, or copolymerizing styrene and butadiene is not particularly limited, but examples include adding the above-mentioned organolithium compound to an organic solvent solution containing butadiene, or styrene and butadiene, and stirring in a temperature range of 0 to 120°C (preferably 30 to 100°C). The polybutadiene, or styrene-butadiene copolymer polymerized using an organolithium compound can have an anionic active end.

[0074] (Specific electrophile) In a preferred embodiment of the method for producing the above-mentioned specific modified polymer, the polymerization of butadiene, or the copolymerization of styrene and butadiene can be terminated using an electrophile (hereinafter also referred to as "specific electrophile") containing at least one functional group selected from the group consisting of an amino group, a hydroxy group, an alkoxysilyl group, and a nitrogen atom and a silicon atom. At least one functional group selected from the group consisting of an amino group, a hydroxy group, an alkoxysilyl group, and a nitrogen atom and a silicon atom that the specific electrophile has corresponds to the specific functional group that the specific modified polymer has. By terminating the above polymerization using a specific electrophile, the above-mentioned specific functional group can be introduced into the specific modified polymer. When the preferred embodiment of the method for producing the above-mentioned specific modified polymer is used, a specific modified polymer having a specific functional group at the end can be obtained.

[0075] The specific electrophile is not particularly limited, but from the reason that the effects of the present invention are more excellent, it preferably contains a compound containing an alkoxysilyl group, or a compound containing a nitrogen atom and a silicon atom, It is more preferable to contain a compound containing a nitrogen atom and a silicon atom, more preferably, it contains a compound containing a nitrogen atom and a silicon atom, and the nitrogen atom is contained as an amino group (-NR2: R is a hydrogen atom or a hydrocarbon group), and / or the silicon atom is contained as a hydrocarbyloxysilyl group (≡SiOR: R is a hydrocarbon group).

[0076] Examples of the compound containing an alkoxysilyl group include N-n-butyl-1,1-dimethoxy-2-azasilacyclopentane, N-phenyl-1,1-dimethoxy-2-azasilacyclopentane, N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane, and N-trimethylsilyl-1,1-diethoxy-2-azasilacyclopentane.

[0077] The specific electrophile is preferably a silazane, more preferably a cyclic silazane, for the reason that the effect of the present invention is more excellent. Here, the silazane is intended to be a compound having a structure in which a silicon atom and a nitrogen atom are directly bonded (a compound having a Si-N bond).

[0078] The cyclic silazane is preferably a compound represented by the following formula (S) for the reason that the effect of the present invention is more excellent.

[0079]

Chemical formula

[0080] In the above formula (S), R1 to R3 each independently represent a hydrogen atom or a substituent. R1 of formula (S) corresponds to R1 of formula (M). R2 to R3 of formula (S) correspond to R2 of formula (M). Specific examples and preferred embodiments of R1, R2 and R3 in formula (S) are the same as R1 and R2 in formula (M) described above, respectively. In the above formula (S), L represents a divalent organic group. L of formula (S) corresponds to L of formula (M). Specific examples and preferred embodiments of the divalent organic group are the same as L in formula (M) described above.

[0081] In the above formula (S), R1 is preferably an alkyl group (preferably having 1 to 10 carbon atoms), an alkylsilyl group (preferably having 1 to 10 carbon atoms), or an aromatic hydrocarbon group (preferably having 6 to 18 carbon atoms) for the reason that the effects of the present invention are more excellent, and more preferably an alkylsilyl group.

[0082] In the above formula (S), R2 and R3 are each preferably independently a hydrocarbyloxy group (-OR group; R is a hydrocarbon group), and more preferably an alkoxy group (preferably having 1 to 10 carbon atoms) for the reason that the effects of the present invention are more excellent.

[0083] In the above formula (S), L is preferably an alkylene group (preferably having 1 to 10 carbon atoms, more preferably 2 to 8 carbon atoms, and even more preferably 3 to 5 carbon atoms) for the reason that the effects of the present invention are more excellent.

[0084] Examples of the compound represented by the above formula (S) include N-n-butyl-1,1-dimethoxy-2-azasilacyclopentane, N-phenyl-1,1-dimethoxy-2-azasilacyclopentane, N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane, N-trimethylsilyl-1,1-diethoxy-2-azasilacyclopentane, and the like.

[0085] It is considered that the silicon atom of the cyclic silazane exhibits electrophilicity. Therefore, when the silicon atom of the cyclic silazane is reacted with polybutadiene or a styrene-butadiene copolymer (which have anionic active terminals) that has been weighted using an organolithium compound as described above, the active terminal of the anion such as the above polybutadiene attacks the silicon atom of the above cyclic silazane, and the above cyclic silazane can be ring-opened at Si-N to form a group represented by, for example, formula (M). In the above case, the group represented by the above formula (M) can be directly bonded to the terminal of the above polybutadiene or the like at the bonding position represented by *.

[0086] The amount of the specific electrophile with respect to the organolithium compound is not particularly limited, but from the reason that the effects of the present invention are more excellent, it is preferably 0.1 to 10, more preferably 1 to 5 in terms of molar ratio.

[0087] (Preferred embodiments of the specific modified polymer) The specific modified polymer, for the reason that the effects of the present invention are more excellent, preferably has a functional group containing a nitrogen atom and a silicon atom at the terminal, and more preferably contains a modified butadiene polymer having a functional group containing a nitrogen atom and a silicon atom at the terminal.

[0088] [Content of the specific modified polymer] In the rubber composition of the present invention, the content of the specific modified BR or the specific modified SBR is 0.5 to 20 parts by mass with respect to 100 parts by mass of the above rubber component. The content of the specific modified BR or the specific modified SBR, for the reason that the effects of the present invention are more excellent, is preferably 1.0 to 15 parts by mass, more preferably 5.0 to 12 parts by mass with respect to 100 parts by mass of the above rubber component. When the rubber composition of the present invention contains the specific modified BR and the specific modified SBR, the contents of the specific modified BR and the specific modified SBR are each independently 0.5 to 20 parts by mass with respect to 100 parts by mass of the above rubber component, preferably 1.0 to 15 parts by mass, and more preferably 5.0 to 12 parts by mass.

[0089] (Other inorganic fillers) The rubber composition of the present invention can further contain other inorganic fillers other than the above-mentioned silica. Examples of other inorganic fillers include silica not corresponding to a CTAB adsorption specific surface area of 60 to 250 m 2 / g, carbon black, clay, calcium carbonate, mica, talc, aluminum hydroxide, aluminum oxide, titanium oxide, barium sulfate, and the like.

[0090] (Carbon black) The rubber composition of the present invention preferably further contains carbon black as another inorganic filler other than the above-described silica because the effects of the present invention are more excellent. When the rubber composition of the present invention further contains carbon black, the carbon black preferably contains carbon black having a nitrogen adsorption specific surface area of 20 to 120 m 2 / g, more preferably contains carbon black having a nitrogen adsorption specific surface area of 30 to 100 m 2 / g, and even more preferably contains carbon black having a nitrogen adsorption specific surface area of 40 to 90 m 2 / g, for the reason that the effects of the present invention are more excellent. In this specification, the nitrogen adsorption specific surface area of carbon black can be measured in accordance with JIS K6217-2:2017.

[0091] Examples of carbon black include furnace black, acetylene black, thermal black, channel black, graphite, and the like. Among these, furnace black is preferable.

[0092] (Content of other inorganic fillers) The content of other inorganic fillers (for example, carbon black) other than the above-described silica can be 0 to 100 parts by mass with respect to 100 parts by mass of the above-described rubber component, and is preferably 5 to 50 parts by mass for the reason that the effects of the present invention are more excellent.

[0093] (Compound agents) In addition to the above components, the rubber composition of the present invention can further contain various compound agents generally used in tire rubber compositions, such as vulcanizing agents or crosslinking agents, vulcanization accelerators, zinc oxide, stearic acid, anti-aging agents, processing aids, plasticizers, waxes, liquid polymers (the above liquid polymers do not include specific modified polymers), thermosetting resins, and thermoplastic resins, according to conventional methods. Such compound agents can be mixed by a general method to form a rubber composition and used for vulcanization or crosslinking. The amounts of these compound agents can be conventional general amounts as long as they do not contravene the object of the present invention.

[0094] The rubber composition of the present invention can be prepared by mixing the above components using a known rubber kneading machine, such as a Banbury mixer, a kneader, a roll, etc. The curing conditions (vulcanization conditions) and the curing method (vulcanization method) of the rubber composition of the present invention are not particularly limited. For example, a cured product (vulcanized product) can be obtained by curing according to conventionally known curing conditions and curing methods.

[0095] The rubber composition of the present invention is a rubber composition for tires. Although there is no particular limitation on which constituent part of the tire the rubber composition of the present invention is applied to, it is preferable to apply the rubber composition of the present invention to form at least one selected from the group consisting of the undertread, the sidewall, and the rim cushion of the tire. A tire formed of at least one selected from the group consisting of the undertread, the sidewall, and the rim cushion with the rubber composition of the present invention can achieve both weight reduction and low fuel consumption performance, and can have excellent low-temperature brittleness resistance and silica reinforcing properties that are superior to the conventional level.

[0096] [Tire] The tire of the present invention is a tire in which at least one selected from the group consisting of the undertread, the sidewall, and the rim cushion is formed of the rubber composition for tires of the present invention.

[0097] In the tire of the present invention, the rubber composition for tires used to form at least one selected from the group consisting of the undertread, the sidewall, and the rim cushion is not particularly limited as long as it is the rubber composition for tires of the present invention.

[0098] Hereinafter, the tire of the present invention will be described with reference to the accompanying drawings. Note that the tire of the present invention is not limited to the embodiment shown in the accompanying drawings. FIG. 1 is a schematic partial cross-sectional view of an example of an embodiment of the tire of the present invention. In FIG. 1, the tire has a bead portion 1, a sidewall portion 2, and a tire tread portion 3. Between the pair of left and right bead portions 1 of the tire, a carcass layer 4 in which a fiber cord is embedded is mounted, and the end portion of the carcass layer 4 is folded back from the inside to the outside of the tire around the bead core 5 and the bead filler 6 and wound up. Further, in the bead portion 1, a rim cushion 8 is disposed at a portion in contact with the rim. The tire tread portion 3 has a tread in a portion in contact with a road or the like, and the tread has an undertread 9 and a cap tread 10. Further, in the tire tread portion 3, a belt layer 7 is disposed over the entire circumference of the tire outside the carcass layer 4. In FIG. 1, at least one selected from the group consisting of the undertread 9, the sidewall portion 2, and the rim cushion 8 is formed of the rubber composition for tires of the present invention. When the sidewall portion 2 is formed of the rubber composition for tires of the present invention, one preferred embodiment is that in the sidewall portion 2, a portion outside the carcass layer 4 is formed of the rubber composition for tires of the present invention.

[0099] The tire of the present invention can be manufactured, for example, according to a conventionally known method. Further, as the gas that can be filled in the tire of the present invention, for example, in addition to normal air or air with adjusted oxygen partial pressure, inert gases such as nitrogen, argon, and helium can be used.

Examples

[0100] The present invention will be described in more detail below based on examples. The materials, amounts used, ratios, processing contents, processing procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below.

[0101] 〔Production of hydrogenated SBR〕 ·Preparation of SBR A nitrogen-replaced autoclave reactor with an internal volume of 10 L was charged with 4200 g of cyclohexane, 15 g (0.144 mol) of styrene, 585 g (10.85 mol) of butadiene, 0.433 g (6.0 mmol) of tetrahydrofuran, and 0.037 g (0.20 mmol) of 2,2-di(2-tetrahydrofuryl)propane, and stirring was started. After the temperature of the contents in the reaction vessel was set to 50 °C, a hexane solution of n-butyllithium (3.03 ml at a concentration of 1.55 mol / L, 4.69 mmol of n-butyllithium) was added. After the polymerization conversion rate reached almost 100%, 0.254 g (0.82 mmol) of 2,2-dimethoxy-1-(3-trimethoxysilylpropyl)-1-aza-2-silacyclopentane was added and reacted for 30 minutes. After the reaction, 80.1 mg (2.5 mmol) of methanol was added to stop the reaction, and a part was withdrawn, dried, and then analyzed. The styrene content of the obtained SBR was 2% by mass, the vinyl content was 25% by mass in butadiene, and the weight-average molecular weight was 400,000. The above SBR is a random copolymer of styrene and butadiene. ·Hydrogenation of SBR As described above, the reaction solution stopped with methanol was heated to 80 °C or higher and hydrogen was introduced into the system. Next, 0.70 g of a catalyst mainly composed of titanocene dichloride, 1.2 g of diethylaluminum chloride, and 0.30 g of n-butyllithium were added, and the reaction was carried out while maintaining a hydrogen pressure of 1.0 MPa. After reaching a predetermined hydrogen integrated flow rate, the reaction solution was returned to normal temperature and pressure and withdrawn from the reaction vessel to obtain a polymerization solution. After neutralization, solid rubber was recovered by the steam stripping method. The obtained solid rubber was dehydrated by a roll and dried in a dryer to obtain hydrogenated SBR. The hydrogenation rate of the hydrogenated SBR was 75 mol%, and the glass transition temperature was -65 °C. The styrene content of the hydrogenated SBR (hydrogenated random copolymer of styrene and butadiene) prepared as described above was 2% by mass, and the weight-average molecular weight was 400,000. The hydrogenated SBR was solid under the condition of 23 °C.

[0102] 〔Production of Liquid Rubber 4〕 n-BuLi (manufactured by Kanto Chemical Co., Inc.: 1.60 mol / L (hexane solution), (100 mL, 160 mmol)) was added to a mixed solution of styrene (271 g, 2.6 mol), 1,3-butadiene (640 g, 11.8 mol) and 2,2-di(2-tetrahydrofuryl)propane (manufactured by Tokyo Chemical Industry Co., Ltd., 0.1 mL, 0.55 mmol) in cyclohexane (4.2 kg), and the mixture was stirred at room temperature for 3 hours. After the reaction, N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane (50 g, 228 mmol) was added to stop the polymerization. The resulting solution was taken out and concentrated under reduced pressure. The concentrated solution was poured into methanol (5.0 L) to separate the methanol-insoluble component. As a result, modified SBR (liquid rubber 4) having a functional group represented by the following formula (m1) at the terminal was obtained in a yield of 93% (850 g, Mn = 9,000, Mw = 9,800, Mw / Mn = 1.1). By IR analysis, it was estimated that cis / trans / vinyl = 26 / 40 / 34. Also, Tg was -55°C. The viscosity of liquid rubber 4 at 20°C was 135,000 mPa·s. The ratio of the viscosity at 20°C (viscosity after modification / viscosity before modification in %) was 190%. Liquid rubber 4 was liquid under the condition of 23°C.

Chemical formula

[0103] 〔Production of Liquid Rubber 5〕 n-BuLi (manufactured by Kanto Chemical Co., Inc.: 1.60 mol / L (hexane solution), 100 mL, 160 mmol) was added to a mixed solution of 1,3-butadiene (640 g, 11.8 mol) and 2,2-di(2-tetrahydrofuryl)propane (manufactured by Tokyo Chemical Industry Co., Ltd., 0.1 mL, 0.55 mmol) in cyclohexane (4.2 kg), and the mixture was stirred at room temperature for 3 hours. After the reaction, N-trimethylsilyl-1,1-dimethoxy-2-azasilacyclopentane (50 g, 228 mmol) was added to terminate the polymerization. The resulting solution was taken out and concentrated under reduced pressure. The concentrated solution was poured into methanol (5.0 L) to separate the methanol-insoluble component. As a result, modified BR (liquid rubber 5) having a functional group represented by the following formula (m1) at the terminal was obtained in a 95% yield (608 g, Mn = 6,300, Mw = 9,400, Mw / Mn = 1.5). By IR analysis, it was estimated that cis / trans / vinyl = 24 / 38 / 38. Also, Tg was -76°C. The viscosity of liquid rubber 5 at 20°C was 1500 mPa·s. Also, the ratio of the viscosity at 20°C (viscosity after modification / viscosity before modification in %) was 181%. Liquid rubber 5 was liquid under the condition of 23°C. [Chemical formula]

[0104] [Manufacture of rubber composition] The components shown in Table 1 below were used in the proportions (parts by mass) shown in the same table. First, the components excluding sulfur and vulcanization accelerator among the components shown in Table 1 below were mixed in a 1.7-liter sealed Banbury mixer for 5 minutes, and then the masterbatch was discharged out of the mixer and cooled to room temperature. This masterbatch was put back into the same Banbury mixer, sulfur and vulcanization accelerator were added and mixed to obtain a rubber composition for tires.

[0105] [Preparation of cured product] Using each rubber composition manufactured as described above, a cured product (vulcanized rubber) was prepared by vulcanizing in a mold of a predetermined shape at 160°C for 20 minutes.

[0106] [Evaluation] Using each of the cured products prepared as described above, or liquid rubbers 1 to 5 used in producing each of the above rubber compositions, the following evaluations were conducted. The results are shown in Table 1.

[0107] (Rubber hardness) Using each of the cured products prepared as described above, in accordance with JIS K6253-3:2012 (Vulcanized rubbers and thermoplastic rubbers - Methods for the determination of hardness - Part 3: Durometer hardness), the rubber hardness at a temperature of 23°C was measured using a Type A durometer. The obtained results were described in the "Rubber hardness" column as an index with the value of Comparative Example 1 being 100. In the present invention, when the above index was 98 or more, it was evaluated that the rubber hardness of the obtained cured product was excellent. When the above index was 98 or more, the abrasion resistance was excellent, the obtained cured product could be made thinner, and the tire using the above cured product could be lightened. The larger the above index was than 98, the more excellent the rubber hardness was evaluated. On the other hand, when the above index was less than 98, it was evaluated that the rubber hardness was poor.

[0108] (Low heat build-up property: tanδ(60°C)) The dynamic viscoelasticity of each of the cured products prepared as described above was measured using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho Co., Ltd. under the conditions of a tensile strain of 10 ± 2%, a frequency of 20 Hz, and a temperature of 60°C, and tanδ(60°C) was determined. The obtained value of tanδ(60°C) was described in the "tanδ(60°C)" column as an index with the value of Comparative Example 1 being 100. In the present invention, when the above index was less than 100, it was evaluated that the low heat build-up property of the obtained cured product was excellent. Excellent low heat build-up property means low rolling resistance. The smaller the above index was than 100, the more excellent the low heat build-up property was evaluated. On the other hand, when the above index was 100 or more, it was evaluated that the low heat build-up property was poor.

[0109] (Balance between rubber hardness and low heat build-up property) In the present invention, when the index of the rubber hardness was 98 or more and the index of the tanδ(60°C) was less than 100, it was evaluated that the obtained cured product could achieve both excellent rubber hardness and low heat generation at an excellent level.

[0110] (Low temperature brittleness resistance) Based on JIS K6261-2:2017 (Vulcanized rubber and thermoplastic rubber - Methods for determining low-temperature characteristics - Part 2: Low-temperature impact embrittlement test), the embrittlement temperature of each cured product prepared as described above was measured by Method A (embrittlement limit temperature). The results of the embrittlement temperature of each cured product obtained as described above were shown in the column of "low temperature brittleness resistance" as the difference from the embrittlement temperature of Comparative Example 1 (unit: °C). In the present invention, when the difference from the embrittlement temperature of Comparative Example 1 was less than 0 (that is, a negative value), it was evaluated that the obtained cured product had excellent low-temperature brittleness (excellent low-temperature brittleness resistance). Also, the greater the difference in the negative direction, the more excellent the low-temperature brittleness (low-temperature brittleness resistance). On the other hand, when the difference from the embrittlement temperature of Comparative Example 1 was 0 or more (that is, 0 or a positive value), it was evaluated that the obtained cured product had poor low-temperature brittleness (poor low-temperature brittleness resistance).

[0111] (Reinforcing property of silica: amount of bound rubber) 0.3 g of each unvulcanized rubber composition was put into a wire mesh basket, immersed in 300 mL of toluene at room temperature for 48 hours, then taken out and dried, and the mass of the sample was measured to calculate the amount of bound rubber from the following formula. Amount of bound rubber = [(mass of sample after toluene immersion and drying) - (mass of silica + zinc oxide)] / (mass of rubber component) × 100 (unit: %) The obtained results were described in the column of "amount of bound rubber" as an index with the value of Comparative Example 1 set to 100. In the present invention, when the above index was more than 100, it was evaluated that the reinforcing property of silica by the liquid rubber was excellent. Note that the reinforcing property of silica by the liquid rubber evaluated above is also reflected in the state of the cured product. It was evaluated that the greater the above index was than 100, the more excellent the reinforcing property of silica was. On the one hand, when the above index was 100 or less, it was evaluated that the reinforcing property of silica was poor.

[0112] [Table 1]

[0113] The details of each component shown in Table 1 are as follows. (Rubber component) · NR: Natural rubber. TSR20 · Hydrogenated SBR: Hydrogenated SBR produced as described above. Weight-average molecular weight 400,000. Hydrogenation rate 75%, Tg -65°C. Styrene content is 2% by mass in hydrogenated SBR. (Filler) · CB: Carbon black. Seast F manufactured by Tokai Carbon Co., Ltd. Nitrogen adsorption specific surface area is 41m 2 / g (Silica) · Silica: Zeosil 115GR manufactured by Solvay. CTAB specific surface area is 115m 2 / g (Silane coupling agent) · Silane coupling agent: Si69 manufactured by Evonik Degussa Japan

[0114] (Additive) · Zinc oxide: Three types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd. · Stearic acid: Bead stearic acid manufactured by NOF CORPORATION · Antioxidant: SANTOFLEX 6PPD manufactured by Solutia Europe · Wax: Oz Ace 0015A manufactured by Nippon Seiro Co., Ltd.

[0115] · Liquid rubber 1 (unmodified): Unmodified liquid BR. POLYVEST110 manufactured by Evonik. Liquid polybutadiene, weight-average molecular weight 8,200, molecular weight distribution 1.9 · Liquid rubber 2 (unmodified): Unmodified liquid SBR. RICON184 manufactured by CRAY VALLEY. Liquid butadiene-styrene-random copolymer, number-average molecular weight 8,600 Since both liquid rubbers 1 and 2 are unmodified, they do not correspond to the specific modified polymers in the present invention.

[0116] (Specific modified polymer) · Liquid rubber 3 (specific modified BR having a triethoxysilyl group at the terminal): terminally modified LBR. Polybutadiene having a triethoxysilyl group as a functional group at the terminal. POLYVEST EP ST-E 60 manufactured by Evonik Since liquid rubber 3 has an alkoxysilyl group as a functional group at the terminal as described above, has a weight average molecular weight of 14,100, and a molecular weight distribution of 1.9, it is a modified butadiene polymer and corresponds to a specific modified polymer. The Tg of liquid rubber 3 is -80°C. The viscosity of liquid rubber 3 (under the condition of 20°C) is 7500 - 15000 mPa·s. Liquid rubber 3 is liquid under the condition of 23°C.

[0117] · Liquid rubber 4 (specific modified SBR having a functional group represented by formula (m1) at the terminal): Liquid rubber 4 manufactured as described above. Since liquid rubber 4 has a functional group represented by formula (m1) as a functional group at the terminal as described above, has a weight average molecular weight of 9800, and a molecular weight distribution of 1.1, it is a modified styrene-butadiene polymer and corresponds to a specific modified polymer (specific modified SBR). In liquid rubber 4, the styrene-butadiene polymer is a random copolymer. The Tg of liquid rubber 4 was -55°C. The viscosity of liquid rubber 4 (under the condition of 20°C) was 135000 mPa·s. The ratio of viscosity under the condition of 20°C (viscosity after modification / viscosity before modification in %) was 190%. Liquid rubber 4 is liquid under the condition of 23°C.

[0118] · Liquid rubber 5 (specific modified BR having a functional group represented by formula (m1) at the terminal): Liquid rubber 5 manufactured as described above. Since the liquid rubber 5 has a functional group represented by the formula (m1) as a functional group containing a nitrogen atom and a silicon atom at its terminal, has a weight average molecular weight of 9400, and a molecular weight distribution of 1.5, it corresponds to a specific modified polymer (specific modified BR). The Tg of the liquid rubber 5 was -76°C. The viscosity of the liquid rubber 5 (under the condition of 20°C) was 1500 mPa·s. The ratio of the viscosity under the condition of 20°C (viscosity after modification / %) of the viscosity before modification was 181%. The liquid rubber 5 is liquid under the condition of 23°C.

[0119] · Sulfur: Micronized sulfur, Kinka printing ink, manufactured by Tsurumi Chemical Industry Co., Ltd. · Vulcanization accelerator: Nocceler CZ-G, manufactured by Ouchi Shinsei Chemical Co., Ltd.

[0120] From the results in Table 1, it was confirmed that the rubber composition of the present invention exhibits the desired effects.

[0121] On the other hand, Comparative Example 1 which does not contain a predetermined specific modified polymer could not achieve both rubber hardness and low heat build-up properties, and had poor low-temperature brittleness resistance and poor silica reinforcement. Comparative Examples 2 and 3 which do not contain a predetermined specific modified polymer and instead contain unmodified liquid rubber 1 or 2 could not achieve both rubber hardness and low heat build-up properties, and had poor silica reinforcement.

Explanation of symbols

[0122] 1 Bead part 2 Sidewall part 3 Tire tread part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Rim cushion 9 Under tread 10 Cap tread

Claims

1. Based on 100 parts by mass of a rubber component containing 10 parts by mass or more of a hydrogenated aromatic vinyl-conjugated diene copolymer having a weight average molecular weight of 200,000 or more, CTAB adsorption specific surface area of 60 to 250 m ２ / g of silica in an amount of 10 parts by mass or more, and a silane coupling agent, and 0.5 to 20 parts by mass of a modified butadiene polymer or a modified styrene-butadiene polymer having at least one functional group selected from the group consisting of an amino group, a hydroxy group, an alkoxysilyl group, and a functional group containing a nitrogen atom and a silicon atom in a side chain or at a terminal, having a weight average molecular weight of 1,000 to 100,000, and a molecular weight distribution of 2.0 or less, A rubber composition for a tire, wherein the content of the silane coupling agent is 1 to 15% by mass of the content of the silica.

2. The CTAB adsorption specific surface area is 60 to 170 m ２ / g, and the rubber composition for tires according to claim 1.

3. The rubber composition for a tire according to claim 1, wherein the hydrogenation rate of the hydrogenated aromatic vinyl-conjugated diene copolymer is 60 mol% or more.

4. The rubber composition for a tire according to claim 1, wherein the rubber component further contains 10 parts by mass or more of an isoprene-based rubber.

5. The rubber composition for a tire according to claim 1, wherein the modified butadiene polymer or the modified styrene-butadiene polymer has a functional group containing a nitrogen atom and a silicon atom at a terminal.

6. A tire, wherein at least one selected from the group consisting of a tread, a sidewall, and a rim cushion is formed of the rubber composition for a tire according to any one of claims 1 to 5.

Images