Rubber composition for tires, tread rubber for tires, and tire

Abstract

The present invention addresses the problem of providing a rubber composition for tires, which has improved workability in kneading while maintaining fracture resistance. The means for solving the problem is a rubber composition for tires, comprising a rubber component, a resin component, and a filler, and comprising or not comprising oil, characterized in that the rubber component contains an isoprene skeleton rubber and a styrene-butadiene rubber, the content of the resin component is 1 part by mass or more and less than 50 parts by mass with respect to 100 parts by mass of the rubber component, the resin component is at least partially hydrogenated, and the following formula is satisfied: 0.70 ≤ (the number of parts by mass of the resin component-the number of parts by mass of the oil) / the number of parts by mass of the isoprene skeleton rubber ≤ 1.18.

Description

Rubber composition for tires, tire tread rubber, and tire

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

[0002] Conventionally, from the viewpoint of improving vehicle safety, various studies have been conducted to improve braking performance on wet road surfaces (hereinafter abbreviated as "wet grip performance"). For example, Patent Document 1 below discloses that by applying a rubber composition obtained by compounding a rubber component containing 70% by mass or more of natural rubber with a resin (thermoplastic resin) and a filler containing silica to the tread rubber of a tire, the braking performance of the tire on both dry and wet road surfaces is improved. Also, a method of adding a softener such as a resin or oil to reduce the unvulcanized viscosity of the rubber composition and improve workability during kneading of the rubber composition is known.

[0003] International Publication No. 2015 / 079703

[0004] However, when a softener is added to reduce the unvulcanized viscosity of the rubber composition, the fracture resistance of the rubber composition deteriorates.

[0005] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a rubber composition for a tire that has improved workability in kneading while maintaining fracture resistance, and a tire tread rubber made from such a rubber composition.A further object of the present invention is to provide a tire that has improved productivity while maintaining fracture resistance.

[0006] The rubber composition for a tire, the tread rubber for a tire, and the tire of the present invention that solve the above problems are summarized as follows.

[0007] [1] A rubber composition for a tire, comprising a rubber component, a resin component, and a filler, and with or without oil, wherein the rubber component comprises an isoprene-skeleton rubber and a styrene-butadiene rubber, the content of the resin component is 1 part by mass or more and less than 50 parts by mass per 100 parts by mass of the rubber component, the resin component is at least partially hydrogenated, and the rubber composition for a tire satisfies the relationship of the following formula (1): 0.70≦(parts by mass of the resin component−parts by mass of the oil) / parts by mass of the isoprene-skeleton rubber≦1.18 (1).

[0008] [2] The rubber composition for a tire according to [1], wherein the styrene-butadiene rubber has a glass transition temperature of less than −40° C.

[0009] [3] The resin component has an SP value difference from the isoprene skeleton rubber of 1.40 (cal / cm ３ ) １／２ The rubber composition for a tire according to [1] or [2] below.

[0010] [4] The resin component has an SP value difference from the isoprene skeleton rubber of 0.50 (cal / cm ３ ) １／２ The rubber composition for a tire according to [3] below.

[0011] [5] The difference in SP value between the isoprene skeleton rubber and the styrene-butadiene rubber is 0.3 (cal / cm ３ ) １／２ The rubber composition for a tire according to any one of [1] to [4] above.

[0012] [6] The rubber composition for a tire according to any one of [1] to [5], wherein the content of the isoprene skeleton rubber is 1 to 80 parts by mass per 100 parts by mass of the rubber component.

[0013] [7] The rubber composition for a tire according to [6], wherein the content of the isoprene skeleton rubber is 1 to 40 parts by mass per 100 parts by mass of the rubber component.

[0014] [8] The rubber composition for a tire according to any one of [1] to [7], wherein the styrene-butadiene rubber is modified with a modifier having a functional group containing a nitrogen atom and an alkoxy group.

[0015] [9] The rubber composition for a tire according to any one of [1] to [8], wherein the resin component has a softening point higher than 110°C and a weight average molecular weight in terms of polystyrene of 200 to 1600 g / mol.

[0016]

[10] The rubber composition for a tire according to [9], wherein the resin component has a weight average molecular weight in terms of polystyrene of 200 to 1200 g / mol.

[0017]

[11] The resin component is hydrogenated C ５ based resin, hydrogenated C ５ -C ９

[11] The rubber composition for a tire according to any one of [1] to

[10] , wherein the rubber component is at least one selected from the group consisting of a cyclopentadiene-based resin, a hydrogenated dicyclopentadiene-based resin, and a hydrogenated terpene-based resin.

[0018]

[12] The rubber composition for a tire according to any one of [1] to

[11] , which satisfies the relationship of the following formula (1'): 0.79≦(parts by mass of the resin component−parts by mass of the oil) / parts by mass of the isoprene skeleton rubber≦1.00 (1').

[0019]

[13] A tread rubber for a tire, comprising the rubber composition for a tire according to any one of [1] to

[12] .

[0020]

[14] A tire comprising the tire tread rubber according to

[13] .

[0021] According to the present invention, it is possible to provide a rubber composition for a tire that has improved workability in kneading while maintaining fracture resistance, and a tire tread rubber made of such a rubber composition. Furthermore, according to the present invention, it is possible to provide a tire that has improved productivity while maintaining fracture resistance.

[0022] The rubber composition for a tire, the tread rubber for a tire, and the tire of the present invention will be described in detail below by way of example based on embodiments thereof.

[0023] <Definitions> The compounds described herein may be derived in whole or in part from fossil resources, from biological resources such as plant resources, from recycled resources such as used tires, or from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0024] <Rubber Composition for Tire> The rubber composition for tire of this embodiment includes a rubber component, a resin component, and a filler, and may or may not include oil. The rubber component for tire of this embodiment includes an isoprene-skeleton rubber and a styrene-butadiene rubber, the content of the resin component is 1 part by mass or more and less than 50 parts by mass per 100 parts by mass of the rubber component, the resin component is at least partially hydrogenated, and the relationship of the following formula (1) is satisfied: 0.70≦(parts by mass of the resin component−parts by mass of the oil) / parts by mass of the isoprene-skeleton rubber≦1.18 (1).

[0025] In the rubber composition for a tire of this embodiment, by blending a resin component (and optionally blending oil), the unvulcanized viscosity of the rubber composition is reduced, and workability during kneading can be improved. Furthermore, in the rubber composition for a tire of this embodiment, by setting the content of the resin component to less than 50 parts by mass per 100 parts by mass of the rubber component, and further selecting the parts by mass of the resin component, the parts by mass of the oil, and the parts by mass of the isoprene skeleton rubber so as to satisfy the relationship of formula (1), it is possible to achieve both workability during kneading and fracture resistance. Therefore, the rubber composition for a tire of this embodiment has improved workability during kneading while maintaining fracture resistance.

[0026] (Rubber Component) The rubber composition for a tire of this embodiment contains a rubber component, and the rubber component contains an isoprene-skeleton rubber and a styrene-butadiene rubber, and may further contain other rubber components.

[0027] -Isoprene Skeleton Rubber- The isoprene skeleton rubber is a rubber having an isoprene unit as the main skeleton, and specific examples thereof include natural rubber (NR) and synthetic isoprene rubber (IR). When the rubber component contains an isoprene skeleton rubber, the breaking strength of the rubber composition can be increased. As a result, the rolling resistance of a tire using the rubber composition can be reduced, improving fuel economy, and also improving the breaking resistance and wear resistance of the tire.

[0028] The content of the isoprene skeleton rubber is preferably 1 to 80 parts by mass, and more preferably 1 to 40 parts by mass, per 100 parts by mass of the rubber component. When the content of the isoprene skeleton rubber is 1 to 80 parts by mass per 100 parts by mass of the rubber component, the fuel economy performance and wet grip performance of a tire to which the rubber composition is applied can be improved. Furthermore, when the content of the isoprene skeleton rubber is 1 to 40 parts by mass per 100 parts by mass of the rubber component, the fuel economy performance and wet grip performance of a tire to which the rubber composition is applied can be further improved. Furthermore, from the viewpoint of further increasing the compounding effect of the isoprene skeleton rubber, the content of the isoprene skeleton rubber is more preferably 10 parts by mass or more per 100 parts by mass of the rubber component.

[0029] -Styrene-butadiene rubber- The styrene-butadiene rubber (SBR) preferably has a glass transition temperature of less than -40°C, more preferably not more than -45°C, even more preferably not more than -50°C, and preferably higher than -90°C. When the glass transition temperature of the styrene-butadiene rubber is lower than -40°C, the fuel economy and wear resistance of a tire using the rubber composition can be improved. Furthermore, styrene-butadiene rubber having a glass transition temperature higher than -90°C is easy to synthesize.

[0030] The amount of the styrene-butadiene rubber is preferably 20 to 99 parts by mass, more preferably 30 to 99 parts by mass, more preferably 40 to 99 parts by mass, even more preferably 50 to 99 parts by mass, and still more preferably 60 to 99 parts by mass, per 100 parts by mass of the rubber component. When the amount of the styrene-butadiene rubber is 60 to 99 parts by mass, per 100 parts by mass of the rubber component, the fuel economy and wet grip performance of a tire to which the rubber composition for tires is applied can be further improved.

[0031] The difference in SP value between the isoprene skeleton rubber and the styrene-butadiene rubber is 0.3 (cal / cm ３ ) １／２ It is preferable that the calorie content is 0.35 (cal / cm ３ ) １／２ It is more preferable that the difference in SP value between the isoprene skeleton rubber and the styrene-butadiene rubber is 0.3 (cal / cm ３ ) １／２ In the above cases, the isoprene skeleton rubber and the styrene-butadiene rubber tend to become incompatible.

[0032] The styrene-butadiene rubber preferably has a bound styrene content of less than 15% by mass. The bound styrene content of the styrene-butadiene rubber refers to the proportion of styrene units contained in the styrene-butadiene rubber. If the bound styrene content of the styrene-butadiene rubber is less than 15% by mass, the glass transition temperature is likely to be low. The bound styrene content of the styrene-butadiene rubber is more preferably 14% by mass or less, more preferably 13% by mass or less, and even more preferably 12% by mass or less. Furthermore, from the viewpoint of the wear resistance of a tire to which the rubber composition is applied, the bound styrene content of the styrene-butadiene rubber is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 8% by mass or more. The bound styrene content of the styrene-butadiene rubber can be adjusted by the amount of monomers used in the polymerization of the styrene-butadiene rubber, the degree of polymerization, etc.

[0033] The styrene-butadiene rubber is preferably modified with a modifier having a nitrogen-containing functional group and an alkoxy group. When the styrene-butadiene rubber is modified with a modifier having a nitrogen-containing functional group and an alkoxy group, the balance between wet grip performance, fuel economy, and wear resistance of a tire to which the rubber composition is applied is improved, and in particular, fuel economy and wear resistance can be improved. The modifier having a nitrogen-containing functional group and an alkoxy group is a general term for modifiers having at least one nitrogen-containing functional group and at least one alkoxy group. The nitrogen-containing functional group is preferably selected from the following: The functional group is a monovalent hydrocarbon group having 1 to 30 carbon atoms and containing a straight-chain, branched, alicyclic, or aromatic ring, and having a functional group selected from the group consisting of a primary amino group, a primary amino group protected with a hydrolyzable protecting group, an onium salt residue of a primary amine, an isocyanate group, a thioisocyanate group, an imine group, an imine residue, an amide group, a secondary amino group protected with a hydrolyzable protecting group, a cyclic secondary amino group, an onium salt residue of a cyclic secondary amine, an acyclic secondary amino group, an onium salt residue of an acyclic secondary amine, an isocyanuric acid triester residue, a cyclic tertiary amino group, an acyclic tertiary amino group, a nitrile group, a pyridine residue, an onium salt residue of a cyclic tertiary amine, and an onium salt residue of an acyclic tertiary amine, or a monovalent hydrocarbon group having 1 to 30 carbon atoms and containing a straight-chain, branched, alicyclic, or aromatic ring, which may contain at least one heteroatom selected from an oxygen atom, a sulfur atom, and a phosphorus atom.

[0034] --Modified Styrene-Butadiene Rubber of First Preferred Embodiment-- The styrene-butadiene rubber (SBR) is preferably modified with an aminoalkoxysilane compound, and from the viewpoint of having a high affinity for fillers, it is more preferable that the terminals of the styrene-butadiene rubber be modified with an aminoalkoxysilane compound. When the terminals of the styrene-butadiene rubber are modified with an aminoalkoxysilane compound, the interaction between the modified styrene-butadiene rubber and the filler (particularly silica) becomes particularly strong.

[0035] The modified site of the styrene-butadiene rubber may be the molecular terminal as described above, or may be the main chain. Styrene-butadiene rubber having a molecular terminal modified can be produced, for example, by reacting various modifiers with the terminal of a styrene-butadiene copolymer having an active terminal, according to the methods described in WO 2003 / 046020 and JP 2007-217562 A. In one preferred embodiment, the styrene-butadiene rubber having a molecular terminal modified can be produced, according to the methods described in WO 2003 / 046020 and JP 2007-217562 A, by reacting an aminoalkoxysilane compound with the terminal of a styrene-butadiene copolymer having an active terminal with a cis-1,4 bond content of 75% or more, and then reacting the resulting mixture with a carboxylic acid partial ester of a polyhydric alcohol for stabilization.

[0036] The carboxylic acid partial ester of a polyhydric alcohol refers to an ester of a polyhydric alcohol and a carboxylic acid, which has one or more hydroxyl groups. Specifically, esters of fatty acids with sugars or modified sugars having 4 or more carbon atoms are preferably used. More preferred examples of this ester include (1) fatty acid partial esters of polyhydric alcohols, particularly partial esters (monoesters, diesters, or triesters) of saturated or unsaturated higher fatty acids having 10 to 20 carbon atoms with polyhydric alcohols, and (2) ester compounds in which 1 to 3 partial esters of polycarboxylic acids and higher alcohols are bonded to a polyhydric alcohol. Polyhydric alcohols used as raw materials for the partial esters are preferably sugars (whether hydrogenated or unhydrogenated) having 5 or 6 carbon atoms and at least three hydroxyl groups, glycols, polyhydroxy compounds, and the like. Furthermore, the raw fatty acids are preferably saturated or unsaturated fatty acids having 10 to 20 carbon atoms, such as stearic acid, lauric acid, and palmitic acid. Among the fatty acid partial esters of polyhydric alcohols, sorbitan fatty acid esters are preferred, and specific examples include sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, and sorbitan trioleate.

[0037] The aminoalkoxysilane compound is not particularly limited, but is preferably an aminoalkoxysilane compound represented by the following general formula (i): １１ ａ -Si-(OR １２ ) ４－ａ ... (i)

[0038] In general formula (i), R １１ and R １２ each independently represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms; R １１ and R １２ At least one of the groups is substituted with an amino group, a is an integer of 0 to 2, and OR １２If there are multiple, each OR １２ may be the same or different, and the molecule does not contain any active protons.

[0039] The aminoalkoxysilane compound is also preferably an aminoalkoxysilane compound represented by the following general formula (ii):

[0040] In the general formula (ii), n1+n2+n3+n4=4 (wherein n2 is an integer of 1 to 4, and n1, n3, and n4 are integers of 0 to 3). １ is at least one functional group selected from a saturated cyclic tertiary amine compound residue, an unsaturated cyclic tertiary amine compound residue, a ketimine residue, a nitrile group, a (thio)isocyanate group, an isocyanuric acid trihydrocarbyl ester group, a nitrile group, a pyridine group, a (thio)ketone group, an amide group, and a primary or secondary amino group having a hydrolyzable group. １ may be the same or different, and A １ may be a divalent group that bonds with Si to form a cyclic structure. ２１ represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when n1 is 2 or more, they may be the same or different. ２２ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, both of which may contain a nitrogen atom and / or a silicon atom. ２２ may be the same or different, or may be joined together to form a ring. ２３ represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom, and when n3 is 2 or greater, may be the same or different. ２４represents a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and may be the same or different when n4 is 2 or greater. As the hydrolyzable group in the primary or secondary amino group having a hydrolyzable group, a trimethylsilyl group or a tert-butyldimethylsilyl group is preferred, and a trimethylsilyl group is particularly preferred.

[0041] The aminoalkoxysilane compound represented by the above general formula (ii) is preferably an aminoalkoxysilane compound represented by the following general formula (iii).

[0042] In the general formula (iii), p1+p2+p3=2 (wherein p2 is an integer of 1 to 2, and p1 and p3 are integers of 0 to 1). ２ is NRa (Ra is a monovalent hydrocarbon group, a hydrolyzable group, or a nitrogen-containing organic group). ２５ R is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ２６ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a nitrogen-containing organic group, any of which may contain a nitrogen atom and / or a silicon atom. ２６ may be the same or different, or may be joined together to form a ring. ２７ R is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom. ２８ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. As the hydrolyzable group, a trimethylsilyl group or a tert-butyldimethylsilyl group is preferred, and a trimethylsilyl group is particularly preferred.

[0043] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (iv) or (v).

[0044] In the general formula (iv), q1+q2=3 (wherein q1 is an integer of 0 to 2, and q2 is an integer of 1 to 3). ３１ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ３２ and R ３３ are each independently a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ３４ are monovalent aliphatic or alicyclic hydrocarbon groups having 1 to 20 carbon atoms or monovalent aromatic hydrocarbon groups having 6 to 18 carbon atoms, and when q1 is 2, they may be the same or different. ３５ represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when q2 is 2 or more, may be the same or different.

[0045]

[0046] In the general formula (v), r1+r2=3 (where r1 is an integer of 1 to 3, and r2 is an integer of 0 to 2). ３６ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ３７ represents a dimethylaminomethyl group, a dimethylaminoethyl group, a diethylaminomethyl group, a diethylaminoethyl group, a methylsilyl(methyl)aminomethyl group, a methylsilyl(methyl)aminoethyl group, a methylsilyl(ethyl)aminomethyl group, a methylsilyl(ethyl)aminoethyl group, a dimethylsilylaminomethyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when r1 is 2 or more, they may be the same or different. R ３８represents a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and may be the same or different when r2 is 2. A specific example of the aminoalkoxysilane compound represented by general formula (v) is N-(1,3-dimethylbutylidene)-3-triethoxysilyl-1-propanamine.

[0047] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (vi) or (vii):

[0048] In general formula (vi), R ４０ is a trimethylsilyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ４１ R is a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ４２ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, where TMS represents a trimethylsilyl group (the same applies hereinafter).

[0049]

[0050] In general formula (vii), R ４３ and R ４４ are each independently a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ４５ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and each R ４５ may be the same or different.

[0051] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (viii) or the following general formula (ix).

[0052] In general formula (viii), s1+s2 is 3 (wherein s1 is an integer of 0 to 2, and s2 is an integer of 1 to 3). ４６ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ４７ and R ４８ are each independently a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ４７ or R ４８ may be the same or different.

[0053]

[0054] In general formula (ix), X is a halogen atom. ４９ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ５０ and R ５１ are each independently a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or R ５０ and R ５１ are bonded to form a divalent organic group. ５２ and R ５３ are each independently a halogen atom, a hydrocarbyloxy group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ５０ and R ５１ As the hydrolyzable group, a hydrolyzable group is preferred, and as the hydrolyzable group, a trimethylsilyl group or a tert-butyldimethylsilyl group is preferred, and a trimethylsilyl group is particularly preferred.

[0055] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (x), the following general formula (xi), the following general formula (xii), or the following general formula (xiii).

[0056] In the general formulas (x) to (xiii), the symbols U and V are each an integer of 0 to 2 and satisfy U+V=2. ５４ ~ ９２ may be the same or different and are monovalent or divalent aliphatic or alicyclic hydrocarbon groups having 1 to 20 carbon atoms, or monovalent or divalent aromatic hydrocarbon groups having 6 to 18 carbon atoms. α and β in general formula (xiii) are integers of 0 to 5.

[0057] Among the compounds satisfying general formula (x), general formula (xi), and general formula (xii), N1,N1,N7,N7-tetramethyl-4-((trimethoxysilyl)methyl)heptane-1,7-diamine, 2-((hexyl-dimethoxysilyl)methyl)-N1,N1,N3,N3-2-pentamethylpropane-1,3-diamine, N1-(3-(dimethylamino)propyl)-N3,N3-dimethyl-N1-(3-(trimethoxysilyl)propyl)propane-1,3-diamine, and 4-(3-(dimethylamino)propyl)-N1,N1,N7,N7-tetramethyl-4-((trimethoxysilyl)methyl)heptane-1,7-diamine are particularly preferred. Among the compounds satisfying general formula (xiii), N,N-dimethyl-2-(3-(dimethoxymethylsilyl)propoxy)ethanamine, N,N-bis(trimethylsilyl)-2-(3-(trimethoxysilyl)propoxy)ethanamine, N,N-dimethyl-2-(3-(trimethoxysilyl)propoxy)ethanamine, and N,N-dimethyl-3-(3-(trimethoxysilyl)propoxy)propan-1-amine are particularly preferred.

[0058] --Modified Styrene-Butadiene Rubber of Second Preferred Embodiment-- The styrene-butadiene rubber (SBR) is also preferably modified with a coupling agent represented by the following general formula (I). In this case, the fuel economy and wear resistance of a tire using the rubber composition can be further improved.

[0059] In the above general formula (I), R １ , R ２ and R３ R each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. ４ , R ５ , R ６ , R ７ and R ９ R each independently represents an alkyl group having 1 to 20 carbon atoms. ８ and R １１ R each independently represents an alkylene group having 1 to 20 carbon atoms. １０ represents an alkyl group or a trialkylsilyl group having 1 to 20 carbon atoms, m represents an integer of 1 to 3, and p represents 1 or 2. R １ ~R １１ When a plurality of i, j, and p are present, they are each independent. i, j, and k each independently represent an integer of 0 to 6, provided that (i + j + k) is an integer of 3 to 10. A represents a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom, and a phosphorus atom, and having no active hydrogen. Here, in general formula (I), the hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of organic groups having no active hydrogen include a hydroxyl group (-OH), a secondary amino group (>NH), a primary amino group (-NH ２ ), a functional group having an active hydrogen such as a sulfhydryl group (-SH), or an organic group not having such a functional group.

[0060] The styrene-butadiene rubber modified with the coupling agent represented by the general formula (I) has a weight average molecular weight (Mw) of 20×10 ４ ~300 x 10 ４ and the molecular weight is 200 × 10 relative to the total amount of the modified styrene-butadiene rubber. ４ ~500 x 10 ４ It is preferable that the modified styrene-butadiene rubber contains 0.25 to 30 mass % of the modified styrene-butadiene rubber represented by the formula (I) and has a shrinkage factor (g') of less than 0.64.

[0061] In general, polymers having branches tend to have smaller molecular size compared to linear polymers having the same absolute molecular weight, and the shrinkage factor (g') is an index of the ratio of the molecular size to that of a linear polymer having the same assumed absolute molecular weight. In other words, the shrinkage factor (g') tends to decrease as the degree of branching of a polymer increases. In this embodiment, intrinsic viscosity is used as an index of molecular size, and linear polymers have an intrinsic viscosity [η] = -3.883 M ０．７７１ The shrinkage factor (g') for each absolute molecular weight of the modified styrene-butadiene rubber is calculated, and the shrinkage factor (g') is used as the value that follows the relational expression below when the absolute molecular weight is 100 x 10 ４ ~200 x 10 ４The average value of the contraction factor (g') when the above formula is used is the contraction factor (g') of the modified styrene-butadiene rubber. Here, "branching" refers to a branch formed by direct or indirect bonding of one polymer to another polymer. Furthermore, the "degree of branching" refers to the number of polymers that are directly or indirectly bonded to one branch. For example, when five styrene-butadiene copolymer chains (described below) are indirectly bonded to each other via coupling residues (described below), the degree of branching is 5. Note that the coupling residue is a structural unit of the modified styrene-butadiene rubber that is bonded to the styrene-butadiene copolymer chain, and is, for example, a structural unit derived from a coupling agent that is generated by reacting a styrene-butadiene copolymer (described below) with a coupling agent. Furthermore, the styrene-butadiene copolymer chain is a structural unit of the modified styrene-butadiene rubber, and is, for example, a structural unit derived from a styrene-butadiene copolymer that is generated by reacting a styrene-butadiene copolymer (described below) with a coupling agent. The shrinkage factor (g') is preferably less than 0.64, more preferably 0.63 or less, more preferably 0.60 or less, even more preferably 0.59 or less, and even more preferably 0.57 or less. The lower limit of the shrinkage factor (g') is not particularly limited and may be below the detection limit, but is preferably 0.30 or more, more preferably 0.33 or more, even more preferably 0.35 or more, and even more preferably 0.45 or more. By using a modified styrene-butadiene rubber having a shrinkage factor (g') within this range, the processability of the rubber composition is improved. Since the shrinkage factor (g') tends to depend on the degree of branching, the shrinkage factor (g') can be controlled, for example, using the degree of branching as an index. Specifically, when a modified styrene-butadiene rubber has a branching degree of 6, its shrinkage factor (g') tends to be 0.59 or more and 0.63 or less, and when a modified styrene-butadiene rubber has a branching degree of 8, its shrinkage factor (g') tends to be 0.45 or more and 0.59 or less.

[0062] The styrene-butadiene rubber modified with the coupling agent represented by the general formula (I) preferably has branches and a degree of branching of 5 or more. Furthermore, the modified styrene-butadiene rubber has one or more coupling residues and a styrene-butadiene copolymer chain bonded to the coupling residue, and more preferably, the branches include branches in which five or more styrene-butadiene copolymer chains are bonded to one coupling residue. By specifying the structure of the modified styrene-butadiene rubber so that the degree of branching is 5 or more and the branches include branches in which five or more styrene-butadiene copolymer chains are bonded to one coupling residue, the contraction factor (g') can be more reliably reduced to less than 0.64. The number of styrene-butadiene copolymer chains bonded to one coupling residue can be confirmed from the value of the contraction factor (g'). Furthermore, the modified styrene-butadiene rubber more preferably has branches and a degree of branching of 6 or more. Furthermore, it is more preferable that the modified styrene-butadiene rubber has one or more coupling residues and a styrene-butadiene copolymer chain bonded to the coupling residue, and further, that the branching includes branches in which six or more styrene-butadiene copolymer chains are bonded to one coupling residue. By specifying the structure of the modified styrene-butadiene rubber so that the branching degree is 6 or more and the branching includes branches in which six or more styrene-butadiene copolymer chains are bonded to one coupling residue, the shrinkage factor (g') can be made 0.63 or less. Furthermore, it is more preferable that the modified styrene-butadiene rubber has branches, and the branching degree is 7 or more, and even more preferably 8 or more. The upper limit of the branching degree is not particularly limited, but it is preferably 18 or less.Furthermore, the modified styrene-butadiene rubber has one or more coupling residues and styrene-butadiene copolymer chains bonded to the coupling residues, and further, it is more preferable that the branches include branches in which seven or more styrene-butadiene copolymer chains are bonded to one coupling residue, and it is particularly preferable that the branches include branches in which eight or more styrene-butadiene copolymer chains are bonded to one coupling residue. By specifying the structure of the modified styrene-butadiene rubber so that the branching degree is 8 or more and the branches include branches in which eight or more styrene-butadiene copolymer chains are bonded to one coupling residue, the shrinkage factor (g') can be made 0.59 or less.

[0063] It is preferable that at least one end of the styrene-butadiene copolymer chain is bonded to a silicon atom of each coupling residue. In this case, the ends of a plurality of styrene-butadiene copolymer chains may be bonded to one silicon atom. Alternatively, an end of the styrene-butadiene copolymer chain and an alkoxy group or hydroxyl group having 1 to 20 carbon atoms may be bonded to one silicon atom, and as a result, that one silicon atom may constitute an alkoxysilyl group or silanol group having 1 to 20 carbon atoms.

[0064] The modified styrene-butadiene rubber may be an oil-extended rubber obtained by adding an extender oil. The modified styrene-butadiene rubber may be either non-oil-extended or oil-extended, but from the viewpoint of abrasion resistance, the Mooney viscosity measured at 100°C is preferably 20 or more and 100 or less, and more preferably 30 or more and 80 or less.

[0065] The weight average molecular weight (Mw) of the modified styrene-butadiene rubber is preferably 20×10 ４ 300 x 10 or more ４ or less, more preferably 50×10 ４ or more, more preferably 64×10 ４ More preferably, it is 80×10 ４ The weight average molecular weight is preferably 250×10 ４or less, and more preferably 180×10 ４ or less, and more preferably 150×10 ４ The weight average molecular weight is 20×10 or less. ４ When the weight average molecular weight is 300×10 or more, the low loss property and abrasion resistance of the rubber composition can be sufficiently improved. ４ When it is equal to or less than this, the processability of the rubber composition is improved.

[0066] The modified styrene-butadiene rubber has a molecular weight of 200×10 relative to the total amount (100% by mass) of the modified styrene-butadiene rubber. ４ Above 500 x 10 ４ It is preferable that the modified styrene-butadiene rubber (hereinafter also referred to as "specific high molecular weight component") contains 0.25% by mass or more and 30% by mass or less of the specific high molecular weight component. When the content of the specific high molecular weight component is 0.25% by mass or more and 30% by mass or less, the low loss and wear resistance of the rubber composition can be sufficiently improved. The modified styrene-butadiene rubber contains the specific high molecular weight component preferably at 1.0% by mass or more, more preferably at 1.4% by mass or more, even more preferably at 1.75% by mass or more, still more preferably at 2.0% by mass or more, particularly preferably at 2.15% by mass or more, and extremely preferably at 2.5% by mass or more. Furthermore, the modified styrene-butadiene rubber contains the specific high molecular weight component preferably at 28% by mass or less, more preferably at 25% by mass or less, even more preferably at 20% by mass or less, and even more preferably at 18% by mass or less. In this specification, the "molecular weight" of the rubber component refers to the standard polystyrene equivalent molecular weight obtained by GPC (gel permeation chromatography). In order to obtain a modified styrene-butadiene rubber having a content of a specific high molecular weight component within this range, it is preferable to control the reaction conditions in the polymerization step and reaction step described below. For example, in the polymerization step, the amount of an organic monolithium compound used as a polymerization initiator, described below, may be adjusted. Furthermore, in the polymerization step, whether the polymerization method is continuous or batchwise, it is preferable to use a method having a residence time distribution, that is, to widen the time distribution of the propagation reaction.

[0067] In the modified styrene-butadiene rubber, the molecular weight distribution (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably 1.6 to 3.0. If the molecular weight distribution of the modified styrene-butadiene rubber is in this range, the processability of the rubber composition will be good.

[0068] The method for producing the modified styrene-butadiene rubber is not particularly limited, but preferably includes a polymerization step of copolymerizing butadiene and styrene using an organic monolithium compound as a polymerization initiator to obtain a styrene-butadiene copolymer, and a reaction step of reacting an active terminal of the styrene-butadiene copolymer with a pentafunctional or higher reactive compound (hereinafter also referred to as a "coupling agent").

[0069] The polymerization step is preferably a propagation polymerization by a living anionic polymerization reaction, which can produce a styrene-butadiene copolymer having active terminals and a modified styrene-butadiene rubber with a high modification rate. The styrene-butadiene copolymer is obtained by copolymerizing 1,3-butadiene and styrene.

[0070] The amount of the organic monolithium compound used as a polymerization initiator is preferably determined based on the target molecular weight of the styrene-butadiene copolymer or modified styrene-butadiene rubber. The amount of monomers, such as 1,3-butadiene and styrene, used relative to the amount of polymerization initiator is related to the degree of polymerization, i.e., the number average molecular weight and / or weight average molecular weight. Therefore, to increase the molecular weight, it is advisable to adjust the amount of polymerization initiator to a smaller amount, and to decrease the molecular weight, it is advisable to adjust the amount of polymerization initiator to a larger amount. The organic monolithium compound is preferably an alkyllithium compound from the viewpoints of industrial availability and ease of control of the polymerization reaction. In this case, a styrene-butadiene copolymer having an alkyl group at the polymerization initiation terminal is obtained. Examples of alkyllithium compounds include n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenelithium. As the alkyllithium compound, n-butyllithium and sec-butyllithium are preferred from the viewpoints of industrial availability and ease of control of the polymerization reaction. These organic monolithium compounds may be used alone or in combination of two or more.

[0071] In the polymerization step, examples of the polymerization reaction mode include batch and continuous polymerization modes. In a continuous mode, one or two or more connected reactors can be used. Continuous reactors, for example, tank-type or tubular reactors equipped with a stirrer, are used. In a continuous mode, preferably, monomers, an inert solvent, and a polymerization initiator are continuously fed into the reactor, a polymer solution containing a polymer is obtained in the reactor, and the polymer solution is continuously discharged. Batch reactors, for example, tank-type reactors equipped with a stirrer, are used. In a batch mode, preferably, monomers, an inert solvent, and a polymerization initiator are fed, and if necessary, monomers are added continuously or intermittently during polymerization, a polymer solution containing a polymer is obtained in the reactor, and the polymer solution is discharged after the polymerization is completed. In this embodiment, in order to obtain a styrene-butadiene copolymer having a high proportion of active ends, a continuous mode is preferred, which allows the polymer to be continuously discharged and subjected to the next reaction in a short period of time.

[0072] The polymerization step is preferably carried out in an inert solvent. Examples of the solvent include hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. Specific hydrocarbon solvents include, but are not limited to, aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene, and hydrocarbons consisting of mixtures thereof. Treating impurities such as allenes and acetylenes with an organometallic compound before subjecting the mixture to the polymerization reaction tends to produce a styrene-butadiene copolymer having a high concentration of active terminals, and thus tends to produce a modified styrene-butadiene rubber with a high modification rate, which is preferable.

[0073] A polar compound may be added in the polymerization step. Adding a polar compound allows styrene to be randomly copolymerized with 1,3-butadiene, and the polar compound also tends to be useful as a vinylating agent for controlling the microstructure of the 1,3-butadiene moiety. Examples of the polar compound include ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium tert-amylate, potassium tert-butylate, sodium tert-butylate, and sodium tert-amylate; and phosphine compounds such as triphenylphosphine. These polar compounds may be used alone or in combination of two or more.

[0074] In the polymerization step, from the viewpoint of productivity, the polymerization temperature is preferably 0° C. or higher, more preferably 120° C. or lower, and particularly preferably 50° C. or higher and 100° C. or lower. When the temperature is within such a range, it tends to be possible to ensure a sufficient amount of the coupling agent to react with the active terminals after the completion of polymerization.

[0075] The amount of bound butadiene in the styrene-butadiene copolymer or modified styrene-butadiene rubber is not particularly limited, but is preferably 40% by mass or more and 100% by mass or less, and more preferably 55% by mass or more and 80% by mass or less. The amount of bound styrene in the styrene-butadiene copolymer or modified styrene-butadiene rubber is not particularly limited, but is preferably more than 0% by mass or less and 60% by mass or less, and more preferably 20% by mass or more and 45% by mass or less. When the amount of bound butadiene and the amount of bound styrene are within the above ranges, the low loss properties and wear resistance of the rubber composition can be further improved. The amount of bound styrene can be measured by ultraviolet absorption of phenyl groups, and the amount of bound butadiene can also be determined from this.

[0076] In the styrene-butadiene copolymer or modified styrene-butadiene rubber, the amount of vinyl bonds in the butadiene bond units is not particularly limited, but is preferably 10 mol% or more and 75 mol% or less, and more preferably 20 mol% or more and 65 mol% or less. When the amount of vinyl bonds is within the above range, the low loss properties and wear resistance of the rubber composition can be further improved. For modified styrene-butadiene rubber, the amount of vinyl bonds (1,2-bond amount) in the butadiene bond units can be determined by Hampton's method [R. R. Hampton, Analytical Chemistry, 21, 923 (1949)].

[0077] The alkoxysilyl group possessed by the coupling agent represented by the general formula (I) above tends to react with, for example, the active terminal possessed by the styrene-butadiene copolymer, dissociating the alkoxylithium and forming a bond between the terminal of the styrene-butadiene copolymer chain and the silicon of the coupling residue. The number of alkoxysilyl groups possessed by the coupling residue is the value obtained by subtracting the number of SiOR groups subtracted by the reaction from the total number of SiOR groups possessed by one molecule of the coupling agent. Furthermore, the azasilacycle group possessed by the coupling agent forms an >N-Li bond and a bond between the terminal of the styrene-butadiene copolymer and the silicon of the coupling residue. Note that the >N-Li bond tends to easily become >NH and LiOH upon exposure to water, etc. during finishing. Furthermore, any alkoxysilyl groups remaining unreacted in the coupling agent tend to easily become silanols (Si-OH groups) upon exposure to water, etc. during finishing.

[0078] The reaction temperature in the reaction step is preferably the same as the polymerization temperature of the styrene-butadiene copolymer, more preferably 0°C or higher and 120°C or lower, and even more preferably 50°C or higher and 100°C or lower. The temperature change from the end of the polymerization step to the addition of the coupling agent is preferably 10°C or lower, more preferably 5°C or lower. The reaction time in the reaction step is preferably 10 seconds or longer, more preferably 30 seconds or longer. From the viewpoint of the coupling rate, the shorter the time from the end of the polymerization step to the start of the reaction step, the more preferably it is within 5 minutes. Mixing in the reaction step may be performed by mechanical stirring, stirring with a static mixer, or the like. When the polymerization step is continuous, the reaction step is also preferably continuous. For example, a tank-type or tubular reactor equipped with a stirrer is used in the reaction step. The coupling agent may be diluted with an inert solvent and continuously supplied to the reactor. When the polymerization step is batchwise, the reaction step may be performed by either adding the coupling agent to the polymerization reactor or transferring it to a separate reactor.

[0079] In the general formula (I), A is preferably represented by any one of the following general formulas (II) to (V): When A is represented by any one of the general formulas (II) to (V), a modified styrene-butadiene rubber having better performance can be obtained.

[0080] In the general formula (II), B １ represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. １ are each independent of each other.

[0081] In the general formula (III), B ２ represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, B ３ represents an alkyl group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. ２ and B ３ are each independent of each other.

[0082] In the general formula (IV), B ４ represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. ４ are each independent of each other.

[0083] In the general formula (V), B ５ represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. ５ are each independent of each other.

[0084] B in the general formulas (II) to (V) １ , B ２ , B ４ , B ５ Regarding the above, examples of the hydrocarbon group having 1 to 20 carbon atoms include an alkylene group having 1 to 20 carbon atoms.

[0085] Preferably, in the general formula (I), A is represented by the general formula (II) or (III), and k is 0. More preferably, in the general formula (I), A is represented by the general formula (II) or (III), and k is 0, and in the general formula (II) or (III), a is an integer of 2 to 10. Even more preferably, in the general formula (I), A is represented by the general formula (II), and k is 0, and in the general formula (II), a is an integer of 2 to 10. Examples of such coupling agents include bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine, tris(3-trimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, and tetrakis(3-trimethoxysilylpropyl). bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trismethoxysilylpropyl)methyl-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane, tris(3-trimethoxysilylpropyl)-methyl-1,3-propanediamine, bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trismethoxysilylpropyl)-methyl-1,3-propanediamine, and the like are particularly preferred among these.

[0086] The amount of the compound represented by general formula (I) added as the coupling agent can be adjusted so that the moles of styrene-butadiene copolymer to the moles of coupling agent react in a desired stoichiometric ratio, which tends to achieve a desired degree of branching. Specifically, the moles of the polymerization initiator are preferably 5.0 times or more, more preferably 6.0 times or more, relative to the moles of the coupling agent. In this case, in general formula (I), the number of functional groups of the coupling agent ((m-1) x i + p x j + k) is preferably an integer of 5 to 10, and more preferably an integer of 6 to 10.

[0087] In order to obtain a modified styrene-butadiene rubber having the specific polymer component, the molecular weight distribution (Mw / Mn) of the styrene-butadiene copolymer is preferably 1.5 or more and 2.5 or less, more preferably 1.8 or more and 2.2 or less. The obtained modified styrene-butadiene rubber is preferably one in which a single peak is detected in the molecular weight curve by GPC. The peak molecular weight of the modified styrene-butadiene rubber by GPC is Mp １ , the peak molecular weight of the styrene-butadiene copolymer is Mp ２ In this case, it is preferable that the following formula is satisfied: １ / Mp ２ )<1.8×10-12×(Mp ２ -120 x 10 ４ ) ２ +2 MP ２ is 20 x 10 ４ Above 80 x 10 ４ Below, Mp １ is 30 x 10 ４ Above 150 x 10 ４ The following is more preferred: １ and Mp ２ is determined by the method described in the Examples below.

[0088] The modification rate of the modified styrene-butadiene rubber is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more. When the modification rate is 30% by mass or more, the low loss property and abrasion resistance of the rubber composition can be further improved.

[0089] After the reaction step, a deactivator, neutralizer, or the like may be added to the copolymer solution as needed. Examples of deactivators include, but are not limited to, water; alcohols such as methanol, ethanol, and isopropanol; and neutralizers include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and versatic acid (a highly branched carboxylic acid mixture having 9 to 11 carbon atoms, with the majority having 10 carbon atoms); aqueous solutions of inorganic acids; and carbon dioxide gas. Furthermore, from the viewpoint of preventing gel formation after polymerization and improving stability during processing, it is preferable to add an antioxidant such as 2,6-di-tert-butyl-4-hydroxytoluene (BHT), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol)propionate, or 2-methyl-4,6-bis[(octylthio)methyl]phenol to the modified styrene-butadiene rubber.

[0090] The modified styrene-butadiene rubber can be obtained from the polymer solution by any known method, including, for example, a method in which the solvent is separated by steam stripping or the like, the polymer is filtered, and then the polymer is dehydrated and dried to obtain the polymer, a method in which the polymer is concentrated in a flashing tank and then devolatilized using a vent extruder or the like, and a method in which the polymer is directly devolatilized using a drum dryer or the like.

[0091] The modified styrene-butadiene rubber obtained by reacting the coupling agent represented by the above general formula (I) with a styrene-butadiene copolymer is represented, for example, by the following general formula (VI).

[0092] In the general formula (VI), D represents a styrene-butadiene copolymer chain, and the weight average molecular weight of the styrene-butadiene copolymer chain is 10 × 10 ４ ~100 x 10 ４The styrene-butadiene copolymer chain is a structural unit of a modified styrene-butadiene rubber, and is, for example, a structural unit derived from a styrene-butadiene copolymer, which is generated by reacting a styrene-butadiene copolymer with a coupling agent. １２ , R １３ and R １４ R each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. １５ and R １８ R each independently represents an alkyl group having 1 to 20 carbon atoms. １６ , R １９ , and R ２０ R each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. １７ and R ２１ R each independently represents an alkylene group having 1 to 20 carbon atoms. ２２ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. m and x represent integers of 1 to 3, with x≦m, p represents 1 or 2, y represents an integer of 1 to 3, with y≦(p+1), and z represents an integer of 1 or 2. When there are multiple D and R, １２ ~R ２２ , m, p, x, y, and z are each independent and may be the same or different. Furthermore, i represents an integer of 0 to 6, j represents an integer of 0 to 6, k represents an integer of 0 to 6, (i + j + k) is an integer of 3 to 10, and ((x × i) + (y × j) + (z × k)) is an integer of 5 to 30. A represents a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom, and a phosphorus atom, and having no active hydrogen. The hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of the organic group having no active hydrogen include a hydroxyl group (—OH), a secondary amino group (>NH), a primary amino group (—NH ２ ), a functional group having an active hydrogen such as a sulfhydryl group (-SH), or an organic group not having such a functional group.

[0093] In the general formula (VI), A is preferably represented by any one of the general formulas (II) to (V). When A is represented by any one of the general formulas (II) to (V), the low loss properties and wear resistance of the rubber composition can be further improved.

[0094] --Third Preferred Embodiment of Modified Styrene-Butadiene Rubber-- It is also preferable that at least one end of the styrene-butadiene rubber (SBR) is modified with a modifier containing a compound (alkoxysilane) represented by the following general formula (1):

[0095] By using as the rubber component a styrene-butadiene rubber modified with a modifier containing a compound represented by the general formula (1) containing an oligosiloxane, which is a filler affinity functional group, and a tertiary amino group, the dispersibility of fillers such as silica can be improved. As a result, the rubber composition of the present invention has improved filler dispersibility, which significantly improves low loss properties, allowing tires using the rubber composition to have reduced rolling resistance and improved fuel economy.

[0096] In the above general formula (1), R １ ~R ８ are each independently an alkyl group having 1 to 20 carbon atoms; L １ and L ２ are each independently an alkylene group having 1 to 20 carbon atoms; and n is an integer of 2 to 4.

[0097] Specifically, in formula (1), R １ ~R ４ may each independently represent a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, １ ~R ４When substituted, each independently may be substituted with one or more substituents selected from the group consisting of 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 (Ra-COO-, where 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, １ ~R ４ may be a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and more specifically, １ ~R ４ may each independently be a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0098] In addition, in formula (1), R ５ ~R ８ 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, １ ~R ４ It should be noted that the R ５ ~R ８ is not an alkyl group but a hydrolyzable substituent, N-R ５ R ６ and N-R ７ R ８ The bond can be hydrolyzed to N--H in the presence of moisture, adversely affecting the processability of the polymer.

[0099] More specifically, in the compound represented by the formula (1), R １ ~R ４ is a methyl group or an ethyl group, and R ５ ~R ８ can be an alkyl group having 1 to 10 carbon atoms.

[0100] The amino group in the compound represented by the formula (1), i.e., N—R５ R ６ and N-R ７ R ８ is preferably a tertiary amino group. The tertiary amino group makes the compound represented by formula (1) have better processability when used as a modifying agent. ５ ~R ８ If a protecting group for protecting the amino group is bonded to the terminal of the polymer or if hydrogen is bonded to the terminal of the polymer, 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, losing its reactivity and making the modification reaction impossible. If a protecting group is bonded, the modification reaction occurs, but the terminal of the polymer is deprotected by hydrolysis during post-processing to become a primary or secondary amino group. The deprotected primary or secondary amino group may cause the viscosity of the compound to increase during subsequent blending, potentially resulting in reduced processability.

[0101] In addition, L in the compound represented by the formula (1) １ and L ２ are each independently a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms. １ and L ２ may each independently be an alkylene group having 1 to 10 carbon atoms, more specifically an alkylene group having 1 to 6 carbon atoms, such as a methylene group, an ethylene group, or a propylene group.

[0102] L in the compound represented by formula (1) １ and L ２ Regarding the above, the shorter the distance between the Si atom and the N atom in the molecule, the better the effect. However, when Si is directly bonded to N, there is a risk that the bond between Si and N may break during the subsequent treatment process, and the secondary amino group generated in this case is likely to be washed away by water during the post-treatment. In the modified styrene-butadiene rubber produced, it is difficult for the amino group, which promotes bonding with fillers such as silica, to bond with the filler, and as a result, the effect of improving the dispersibility of the filler may be reduced. In this way, when the improvement effect depending on the length of the bond between Si and N is taken into consideration, the above L １ and L ２is more preferably each independently an alkylene group having 1 to 3 carbon atoms such as a methylene group, an ethylene group, or a propylene group, and more specifically, can be a propylene group. １ and L ２ First, R １ ~R ４ It may be substituted with substituents as described above.

[0103] The compound represented by formula (1) is preferably, for example, any one of the compounds represented by the following structural formulas (1-1) to (1-5), because this allows for the realization of even better low loss properties.

[0104] The compound represented by formula (1) has an alkoxysilane structure that bonds to the active terminal of the styrene-butadiene copolymer, while the Si—O—Si structure and three or more amino groups bonded to the terminal exhibit affinity for fillers such as silica, thereby promoting bonding between the filler and the modified styrene-butadiene rubber compared to conventional modifiers containing a single amino group per molecule. Furthermore, the degree of bonding at the active terminal of the styrene-butadiene copolymer is uniform, and when observing the change in molecular weight distribution before and after coupling, the molecular weight distribution remains constant without increasing after coupling compared to before coupling. Therefore, there is no deterioration in the physical properties of the modified styrene-butadiene rubber itself, and the aggregation of the filler in the rubber composition can be prevented, increasing the dispersibility of the filler, thereby improving the processability of the rubber composition. These effects, particularly when the rubber composition is applied to tires, enable a balanced improvement in fuel economy and wet grip performance.

[0105] The compound represented by formula (1) can be produced through a condensation reaction represented by the following reaction scheme.

[0106] In the above reaction scheme, R １ ~R ８ , L １ and L ２and 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″ are each independently R １ ~R ４ It can be identical to any one of the following:

[0107] The reaction in the above reaction scheme proceeds in the presence of an acid, 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.

[0108] The styrene-butadiene rubber modified with a modifier containing the compound represented by formula (1) can 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 styrene-butadiene rubber exceeds 3.0 or is less than 1.1, there is a risk of reduced tensile properties and viscoelasticity when applied to a rubber composition. Considering the significant effect of improving tensile properties and viscoelasticity by controlling the molecular weight distribution of the modified styrene-butadiene rubber, the molecular weight distribution of the modified styrene-butadiene rubber is preferably in the range of 1.3 to 2.0. By using the modifier, the modified styrene-butadiene rubber has a molecular weight distribution similar to that of the styrene-butadiene copolymer before modification.

[0109] The molecular weight distribution of the modified styrene-butadiene rubber 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). The weight average molecular weight and number average molecular weight are each polystyrene-equivalent molecular weights analyzed by gel permeation chromatography (GPC).

[0110] Furthermore, the modified styrene-butadiene rubber satisfies the above-mentioned molecular weight distribution condition, and at the same time, the number average molecular weight (Mn) can be 50,000 g / mol to 2,000,000 g / mol, more specifically, 200,000 g / mol to 800,000 g / mol. The modified styrene-butadiene rubber can have 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. If the weight average molecular weight (Mw) of the modified styrene-butadiene rubber is less than 100,000 g / mol or the number average molecular weight (Mn) is less than 50,000 g / mol, there is a risk of a decrease in tensile properties when applied to a rubber composition. Furthermore, if the weight average molecular weight (Mw) exceeds 4,000,000 g / mol or the number average molecular weight (Mn) exceeds 2,000,000 g / mol, the processability of the modified styrene-butadiene rubber decreases, 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, if the modified styrene-butadiene rubber simultaneously satisfies the conditions of the weight average molecular weight (Mw) and number average molecular weight (Mn) as well as the molecular weight distribution, when applied to a rubber composition, it can improve the viscoelasticity and processability of the rubber composition in a well-balanced manner.

[0111] The modified styrene-butadiene rubber preferably has a vinyl bond content in the butadiene moiety of 5% or more, more preferably 10% or more, and is preferably 60% or less. By adjusting the vinyl bond content in the butadiene moiety to fall within the above range, the glass transition temperature can be adjusted to an appropriate range.

[0112] The modified styrene-butadiene rubber may have a Mooney viscosity (MV) at 100°C of 40 to 140, specifically 60 to 100. A Mooney viscosity within this range can exhibit better processability. The Mooney viscosity can be measured using a Mooney viscometer, for example, a Monsanto MV2000E, at 100°C, a rotor speed of 2±0.02 rpm, and a large rotor. The sample used here is left at room temperature (23±3°C) for 30 minutes or more, and then 27±3 g of the sample is taken and filled into the die cavity. The platen is then operated to measure the viscosity.

[0113] As described above, the modified styrene-butadiene rubber is preferably modified at one end with a modifier containing a compound represented by the above general formula (1), and is preferably further modified at the other end with a modifier containing a compound represented by the following general formula (2). By modifying both ends of the modified styrene-butadiene rubber, the dispersibility of the filler in the rubber composition is further improved, and a tire using the rubber composition can achieve both low fuel consumption performance and wet grip performance at a higher level.

[0114] In the above general formula (2), R ９ ~R １１ 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. １２ 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. １３is 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 general formula (2a) or general formula (2b), wherein m is an integer of 1 to 5, and R １３ At least one of the functional groups is represented by the following general formula (2a) or (2b), and when m is an integer of 2 to 5, a plurality of R １３ may be the same as or different from each other.

[0115]

[0116] In the above general formula (2a), R １４ 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. １５ and R １６ 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. １７ 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, provided that when X is O or S, R １７ does not exist.

[0117]

[0118] In the above general formula (2b), R １８is 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. １９ and R ２０ 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.

[0119] In addition, in the compound represented by the general formula (2), R ９ ~R １１ 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; R １２ is a single bond; or an unsubstituted alkylene group having 1 to 10 carbon atoms, R １３ is an alkyl group having 1 to 10 carbon atoms; an alkenyl group having 2 to 10 carbon atoms; an alkynyl group having 2 to 10 carbon atoms; or a functional group represented by the above general formula (2a) or (2b), and in the above general formula (2a), R １４ is an unsubstituted alkylene group having 1 to 10 carbon atoms, and R １５ and R １６ are each independently an unsubstituted alkylene group having 1 to 10 carbon atoms, and R １７ 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 general formula (2b), R １８ is an unsubstituted alkylene group having 1 to 10 carbon atoms, and R １９ and R ２０ 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.

[0120] More specifically, the compound represented by the general formula (2) can be a compound represented by the following structural formulas (2-1) to (2-3).

[0121] When the styrene-butadiene copolymer is modified with a modifying agent containing a compound represented by the general formula (2), the modifying agent containing the compound represented by formula (2) is used as a modification initiator. Specifically, for example, a butadiene monomer and a styrene 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 styrene-butadiene copolymer.

[0122] -Other Rubber- The rubber component may further contain other rubbers, and the content of the other rubbers is preferably 35 parts by mass or less per 100 parts by mass of the rubber component. Examples of such other rubbers include styrene-butadiene rubber, butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), halogenated butyl rubber, ethylene-propylene rubber (EPR, EPDM), fluororubber, silicone rubber, and urethane rubber, all of which have a glass transition temperature of -40°C or higher. Among these, diene rubbers such as butadiene rubber (BR) and chloroprene rubber (CR) are preferred, and butadiene rubber (BR) is more preferred. Furthermore, as the butadiene rubber (BR), high-cis polybutadiene is preferred, and the high-cis polybutadiene preferably has a cis-1,4 bond content of 90% by mass or more. When the rubber component contains butadiene rubber, the content of the butadiene rubber is preferably in the range of 1 to 35 parts by mass per 100 parts by mass of the rubber component.

[0123] (Resin Component) The rubber composition for a tire of this embodiment includes a resin component, and the resin component is at least partially hydrogenated. By at least partially hydrogenating the resin component, compatibility with isoprene-skeleton rubber is increased, the mobility of the rubber component is controlled, and hysteresis loss (tan δ) in the low temperature range can be improved, thereby improving the wet grip performance of a tire using the rubber composition.

[0124] The resin component has an SP value difference of 1.40 (cal / cm) from the isoprene skeleton rubber. ３ ) １／２ The difference in SP value between the resin component and the isoprene skeleton rubber is preferably 1.40 (cal / cm ３ ) １／２ When the SP value of the resin component is not more than 1.35 (cal / cm), the compatibility with the isoprene skeleton rubber is further improved, the mobility of the rubber component is further controlled, and the hysteresis loss (tan δ) in the low temperature region can be further improved, thereby further improving the wet grip performance of a tire to which the rubber composition is applied. ３ ) １／２ It is preferable that the value is 0.50 (cal / cm ３ ) １／２ More preferably, it is 0.45 (cal / cm ３ ) １／２ More preferably, it is 0.3 (cal / cm ３ ) １／２ More preferably, it is 0.25 (cal / cm ３ ) １／２ It is more preferable that the difference in SP value between the resin component and the isoprene skeleton rubber is 0.50 (cal / cm ３ ) １／２ When the content is not more than this, the compatibility between the resin component and the isoprene skeleton rubber is further improved, and the wet grip performance of a tire using the rubber composition is further improved.

[0125] The content of the resin component is 1 part by mass or more and less than 50 parts by mass per 100 parts by mass of the rubber component. When the content of the resin component in the rubber composition is 1 part by mass or more per 100 parts by mass of the rubber component, the effect of the resin component is fully exhibited, and when it is less than 50 parts by mass, the resin component is less likely to precipitate from the tire, allowing the effect of the resin component to be fully exhibited. On the other hand, when the content of the resin component is 50 parts by mass or more per 100 parts by mass of the rubber component, the fracture resistance of the rubber composition is deteriorated, and the fuel economy and wear resistance of a tire using the rubber composition are deteriorated. From the viewpoint of further enhancing the effect of the resin component, the content of the resin component in the rubber composition is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, more preferably 9 parts by mass or more, more preferably 15 parts by mass or more, and even more preferably 17 parts by mass or more per 100 parts by mass of the rubber component. From the viewpoint of suppressing precipitation of the resin component from the tire and suppressing deterioration in the appearance of the tire, the content of the resin component in the rubber composition is more preferably 45 parts by mass or less, and even more preferably 40 parts by mass or less, per 100 parts by mass of the rubber component.

[0126] The resin component preferably has a softening point higher than 110°C and a weight-average molecular weight in polystyrene equivalent of 200 to 1600 g / mol. By applying a rubber composition containing such a resin component to a tire, the wear resistance of the tire can be further improved. Here, the softening point of the resin component is measured in accordance with JIS-K2207-1996 (ring and ball method). The weight-average molecular weight of the resin component is measured by gel permeation chromatography (GPC) and calculated as a polystyrene equivalent value.

[0127] If the softening point of the resin component is higher than 110°C, a tire to which the rubber composition is applied can be sufficiently reinforced, and abrasion resistance can be further improved. From the viewpoint of abrasion resistance of the tire, the softening point of the resin component is more preferably 116°C or higher, more preferably 120°C or higher, more preferably 123°C or higher, and even more preferably 127°C or higher. Furthermore, from the viewpoint of processability, the softening point of the resin component is preferably 160°C or lower, more preferably 150°C or lower, more preferably 145°C or lower, more preferably 141°C or lower, and even more preferably 136°C or lower.

[0128] When the polystyrene-equivalent weight-average molecular weight of the resin component is 200 g / mol or more, the resin component is less likely to precipitate from the tire and the effects of the resin component can be fully exhibited, and when it is 1600 g / mol or less, the resin component is more likely to be compatible with the rubber component. From the viewpoint of suppressing the resin component from precipitating from the tire and suppressing deterioration in the tire appearance, the polystyrene-equivalent weight-average molecular weight of the resin component is preferably 500 g / mol or more, more preferably 550 g / mol or more, even more preferably 600 g / mol or more, even more preferably 650 g / mol or more, and still more preferably 700 g / mol or more. Furthermore, from the viewpoint of improving the compatibility of the resin component with the rubber component and further enhancing the effects of the resin component, the polystyrene-equivalent weight average molecular weight of the resin component is more preferably 1570 g / mol or less, more preferably 1530 g / mol or less, more preferably 1500 g / mol or less, more preferably 1470 g / mol or less, more preferably 1430 g / mol or less, more preferably 1400 g / mol or less, more preferably 1370 g / mol or less, more preferably 1330 g / mol or less, more preferably 1300 g / mol or less, more preferably 1200 g / mol or less, more preferably 1100 g / mol or less, more preferably 1000 g / mol or less, and even more preferably 950 g / mol or less. When the weight average molecular weight of the resin component in terms of polystyrene is 200 to 1200 g / mol, the resin component is less likely to precipitate from the tire, and the resin component is more easily compatible with the rubber component, making the effects of the resin component more pronounced.

[0129] The weight average molecular weight (Mw ＨＲ ) (unit: g / mol) to the softening point (Ts ＨＲ ) (unit: °C) ratio (Ts ＨＲ / Mw ＨＲ) is preferably 0.07 or more, more preferably 0.083 or more, more preferably 0.095 or more, more preferably 0.104 or more, more preferably 0.125 or more, more preferably 0.135 or more, more preferably 0.14 or more, and even more preferably 0.141 or more. ＨＲ / Mw ＨＲ ) is preferably 0.25 or less, more preferably 0.24 or less, more preferably 0.23 or less, more preferably 0.19 or less, more preferably 0.18 or less, and even more preferably 0.17 or less.

[0130] The above-mentioned at least partially hydrogenated resin component means a resin obtained by reducing and hydrogenating a resin. The resins that can be used as raw materials for the hydrogenated resin component include C ５ based resin, C ５ -C ９ based resin, C ９ These resins may be used alone or in combination of two or more.

[0131] Said C ５ As a resin based on C, there is C obtained by thermal decomposition of naphtha in the petrochemical industry. ５ and aliphatic petroleum resins obtained by (co)polymerizing the distillate. ５ The fraction usually contains olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene. ５ Commercially available resins can be used.

[0132] Said C ５ -C ９ The C-based resin is ５ -C ９ It refers to synthetic petroleum resin, ５ -C９ Examples of the resin include petroleum-derived C ５ -C １１ The fraction was treated with AlCl ３ , B.F. ３ More specifically, copolymers containing styrene, vinyltoluene, α-methylstyrene, indene, etc. as the main component may be mentioned. ５ -C ９ As the resin, ９ Resins containing less of the above components are preferred from the viewpoint of compatibility with the rubber component. ９ "Low amount of the above components" means that the C ９ This means that the above components are contained in an amount of less than 50% by mass, preferably 40% by mass or less. ５ -C ９ Commercially available resins can be used.

[0133] Said C ９ The C-based resin is ９ This refers to synthetic petroleum resins, such as AlCl ３ or BF ３ Using a Friedel-Crafts type catalyst such as C ９ It refers to a solid polymer obtained by polymerizing the fraction. ９ Examples of the resin include copolymers containing indene, α-methylstyrene, vinyltoluene, etc. as main components.

[0134] The terpene resin is a solid resin obtained by blending turpentine, which is obtained simultaneously with the extraction of rosin from pine trees, or a polymerization component separated from the blend, and polymerizing the blend using a Friedel-Crafts catalyst. Examples of such resins include β-pinene resin and α-pinene resin. Furthermore, a representative example of a terpene-aromatic compound resin is terpene-phenol resin. This terpene-phenol resin can be obtained by reacting terpenes with various phenols using a Friedel-Crafts catalyst, or by further condensing the terpene with formalin. There are no particular limitations on the terpenes used as raw materials; monoterpene hydrocarbons such as α-pinene and limonene are preferred, with those containing α-pinene being more preferred, and α-pinene being particularly preferred. Styrene or the like may also be included in the skeleton.

[0135] The dicyclopentadiene resin is, for example, AlCl ３ or BF ３ This refers to a resin obtained by polymerizing dicyclopentadiene using a Friedel-Crafts catalyst such as

[0136] The resin that is the raw material for the hydrogenated resin component is, for example, C ５ A resin (C) copolymerized with the fraction and dicyclopentadiene (DCPD) ５ -DCPD-based resin). When the dicyclopentadiene-derived component is 50% by mass or more in the total amount of the resin, C ５ - DCPD-based resins are included in dicyclopentadiene-based resins. When the dicyclopentadiene-derived component is less than 50% by mass in the total amount of resin, C ５ -DCPD resin is C ５ The same applies to cases where a small amount of a third component is contained.

[0137] From the viewpoints of increasing the compatibility between the rubber component and the resin component, further improving the wet grip performance of a tire using the rubber composition, and further reducing the rolling resistance, the resin component is ５ based resin, hydrogenated C ５ -C ９The resin is preferably at least one selected from the group consisting of hydrogenated dicyclopentadiene resins (hydrogenated DCPD resins) and hydrogenated terpene resins, and hydrogenated C ５ Resin and hydrogenated C ５ -C ９ It is more preferable that the resin is at least one selected from the group consisting of hydrogenated C ５ It is more preferable that the resin component is a hydrogenated DCPD-based resin. It is also preferable that the resin component is a resin having at least a hydrogenated DCPD structure or a hydrogenated cyclic structure in the monomer. ５ based resin, hydrogenated C ５ -C ９ When the rubber composition is at least one selected from the group consisting of a cyclopentadiene-based resin, a hydrogenated dicyclopentadiene-based resin, and a hydrogenated terpene-based resin, the wet grip performance of a tire to which the rubber composition is applied can be further improved, and the rolling resistance can be further reduced.

[0138] (Filler) The rubber composition for tires of this embodiment contains a filler. The inclusion of a filler improves the reinforcement properties of the rubber composition. The content of the filler in the rubber composition is preferably in the range of 40 to 125 parts by mass per 100 parts by mass of the rubber component. When the content of the filler in the rubber composition is 40 parts by mass or more per 100 parts by mass of the rubber component, the tire using the rubber composition is sufficiently reinforced, and the fracture resistance and abrasion resistance can be further improved. When the content of the filler in the rubber composition is 125 parts by mass or less per 100 parts by mass of the rubber component, the modulus of elasticity of the rubber composition does not become too high, and the wet grip performance of the tire using the rubber composition is further improved. From the viewpoint of further reducing the rolling resistance of the tire (from the viewpoint of improving fuel economy), the content of the filler in the rubber composition is more preferably 45 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of improving the wet grip performance of the tire, the content of the filler in the rubber composition is more preferably 105 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 95 parts by mass or less, per 100 parts by mass of the rubber component.

[0139] -Silica- The filler preferably contains silica, and has a nitrogen adsorption specific surface area (BET method) of 80 m ２ / g or more 330m ２ It is more preferable that the silica contains silica having a nitrogen adsorption specific surface area (BET method) of less than 80 m / g. ２ When the silica has a nitrogen adsorption specific surface area (BET method) of 330 m / g or more, a tire to which the rubber composition is applied can be sufficiently reinforced, and the rolling resistance of the tire can be further reduced. ２ When the modulus of elasticity of the rubber composition is less than 1 / g, the rubber composition does not become too high, and the wet grip performance of a tire using the rubber composition is further improved. From the viewpoint of further reducing the rolling resistance and further improving the wear resistance of a tire, the nitrogen adsorption specific surface area (BET method) of silica is 110 m ２ / g or more, and ２ / g or more, and ２ / g or more, and ２ From the viewpoint of further improving the wet grip performance of the tire, the nitrogen adsorption specific surface area (BET method) of the silica is more preferably 300 m ２ / g or less, and ２ / g or less is more preferable, and 270m ２ It is more preferable that the tensile strength is 1 / g or less.

[0140] 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.

[0141] As the silica, plant-derived silica is also preferred. From the viewpoint of reducing environmental impact, the plant-derived silica is preferably silica derived from silicic acid plants. Examples of such silicic acid plants include mosses, ferns, horsetails, Cucurbitaceae, Urticaceae, and Poaceae plants. Among these plants, grasses are preferred, i.e., grasses are preferred as the plant-derived silica. Grass-derived silica can be procured locally near tire manufacturing plants, reducing the energy and costs required for transportation and storage, making it environmentally preferable from various perspectives. Examples of such grasses include rice, bamboo grass, and sugarcane, with rice being preferred. Rice is widely cultivated for food and therefore can be procured locally over a wide area. Furthermore, rice husks are generated in large quantities as industrial waste, making it easy to secure a sufficient amount. Therefore, from the viewpoint of availability, rice husk-derived silica (hereinafter also referred to as "rice husk silica") is particularly preferred as the plant-derived silica. The use of rice husk silica allows for the effective utilization of rice husks, which are industrial waste, and also allows for the local procurement of raw materials near tire manufacturing plants, thereby reducing the energy and costs of transportation and storage, making it environmentally advantageous from various perspectives. The rice husk silica may be rice husk charcoal powder obtained by carbonizing rice husks by heating, or may be precipitated silica produced by a wet process using an alkali silicate aqueous solution obtained by extracting rice husk ash, which is generated when rice husks are burned as fuel in a biomass boiler, with an alkali. The method for producing rice husk charcoal is not particularly limited, and various known methods can be used. For example, rice husk charcoal can be obtained by pyrolyzing rice husks by steaming them in a kiln. The rice husk charcoal obtained in this manner can be pulverized using a known pulverizer (e.g., a ball mill), sorted, and classified into particles of a predetermined particle size range, to obtain rice husk charcoal powder. The precipitated silica derived from rice husks can be produced by the method described in JP-A-2019-38728.

[0142] From the viewpoint of improving the mechanical strength of the tire and further improving the fracture resistance and abrasion resistance, the content of silica in the rubber composition is preferably 40 parts by mass or more, more preferably 45 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more, per 100 parts by mass of the rubber component. Also, from the viewpoint of further improving the wet grip performance of the tire, the content of silica in the rubber composition is preferably 125 parts by mass or less, more preferably 105 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 95 parts by mass or less, per 100 parts by mass of the rubber component.

[0143] -Carbon Black- The filler preferably contains carbon black. The carbon black reinforces the rubber composition and can improve the fracture resistance and abrasion resistance of the rubber composition. The carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF grade carbon black. These carbon blacks may be used alone or in combination of two or more. The carbon black may also be recycled carbon black.

[0144] In this specification, "recycled carbon black" refers to carbon black recovered from raw materials that are waste materials that have been recycled. Examples of the waste materials that have been recycled include rubber products (particularly vulcanized rubber products) containing carbon black, such as used rubber and used tires, and waste oil. "Recycled carbon black" differs from carbon black that is produced directly from hydrocarbons such as petroleum and natural gas, i.e., non-recycled carbon black. Note that "used" here refers not only to carbon black that has been discarded after actual use, but also to carbon black that has been produced but discarded without actually being used.

[0145] From the viewpoint of improving the fracture resistance and abrasion resistance of the rubber composition and a tire using the same, the content of carbon black in the rubber composition is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of workability of the rubber composition, the content of carbon black in the rubber composition is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, per 100 parts by mass of the rubber component. When the filler contains silica and carbon black, the proportion of silica in the total amount of silica and carbon black is preferably 80% by mass or more and less than 100% by mass, and more preferably 90% by mass or more and less than 100% by mass. A silica proportion of 80% by mass or more improves the mechanical strength of a tire using the rubber composition, and can further reduce rolling resistance.

[0146] -Other Fillers- In addition to silica and carbon black, the filler may contain inorganic fillers such as clay, talc, calcium carbonate, and aluminum hydroxide. The above-mentioned other fillers are preferably contained in such a range that the proportion of silica in the filler is 70% by mass or more. When the proportion of silica in the filler is 70% by mass or more, the mechanical strength of a tire to which the rubber composition is applied can be improved and the rolling resistance can be further reduced. The proportion of silica in the filler is more preferably 80% by mass or more, even more preferably 85% by mass or more, and even more preferably 90% by mass or more but less than 100% by mass.

[0147] (Oil) The rubber composition for a tire of this embodiment may or may not contain oil; that is, in the rubber composition for a tire of this embodiment, oil is not an essential component but an optional component.

[0148] The oil is a general term for extender oil contained in the rubber component and liquid oils [more specifically, liquid at 25°C (room temperature)] added as compounding agents to the rubber composition, and includes petroleum oils such as aromatic oils, paraffinic oils, naphthenic oils, etc.; and vegetable oils such as palm oil, castor oil, cottonseed oil, soybean oil, etc. Among these, petroleum oils such as aromatic oils, paraffinic oils, naphthenic oils, etc. are preferred.

[0149] The content of the oil may be 0 part by mass (i.e., 0 part by mass or more) per 100 parts by mass of the rubber component, and is preferably 1 part by mass or more, more preferably 2.5 parts by mass or more, and is preferably 5 parts by mass or less, and more preferably 3 parts by mass or less. When the content of the oil is 2.5 parts by mass or more per 100 parts by mass of the rubber component, the unvulcanized viscosity of the rubber composition is further reduced, and workability in kneading is further improved. Furthermore, when the content of the oil is 3 parts by mass or less per 100 parts by mass of the rubber component, the fracture resistance of the rubber composition can be more reliably maintained.

[0150] The difference between the number of parts by mass of the resin component (i.e., the content (parts by mass) of the resin component per 100 parts by mass of the rubber component) and the number of parts by mass of the oil (i.e., the content (parts by mass) of the oil per 100 parts by mass of the rubber component) (number of parts by mass of resin component - number of parts by mass of oil) is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, and is preferably 40 parts by mass or less, and more preferably 30 parts by mass or less. When [number of parts by mass of resin component - number of parts by mass of oil] is 20 parts by mass or more, fracture resistance can be maintained, and when [number of parts by mass of resin component - number of parts by mass of oil] is 40 parts by mass or less, workability in kneading can be improved.

[0151] (Relationship Between Resin Component, Oil, and Parts by Mass of Isoprene Skeleton Rubber) The rubber composition for a tire of this embodiment is characterized by satisfying the relationship of the following formula (1): 0.70≦(Parts by mass of the resin component−Parts by mass of the oil) / Parts by mass of the isoprene skeleton rubber≦1.18 (1). Here, the "parts by mass of the resin component" refers to the content (parts by mass) of the resin component per 100 parts by mass of the rubber component, the "parts by mass of the oil" refers to the content (parts by mass) of the oil per 100 parts by mass of the rubber component, and the "parts by mass of the isoprene skeleton rubber" refers to the content (parts by mass) of the isoprene skeleton rubber per 100 parts by mass of the rubber component. If the ratio [(Parts by mass of the resin component−Parts by mass of the oil) / Parts by mass of the isoprene skeleton rubber] is less than 0.70, the fracture resistance of the rubber composition is significantly deteriorated. Furthermore, if the ratio [(parts by mass of resin component - parts by mass of oil) / parts by mass of isoprene skeleton rubber] exceeds 1.18, the fracture resistance of the rubber composition also deteriorates. From the viewpoint of the fracture resistance of the rubber composition, [(parts by mass of resin component - parts by mass of oil) / parts by mass of isoprene skeleton rubber] is preferably 0.71 or more, more preferably 0.79 or more, and is preferably 1.18 or less, and even more preferably 1.00 or less. Furthermore, it is particularly preferable that the rubber composition for tires of this embodiment satisfy the relationship of the following formula (1'): 0.79≦(parts by mass of the resin component - parts by mass of the oil) / parts by mass of the isoprene skeleton rubber≦1.00 (1'). A rubber composition that satisfies the relationship of formula (1') more reliably maintains fracture resistance.

[0152] (Styrene-Based Thermoplastic Elastomer) The rubber composition for tires of this embodiment may contain a styrene-based thermoplastic elastomer (TPS). The styrene-based thermoplastic elastomer (TPS) has a styrene-based polymer block (hard segment) and a conjugated diene-based polymer block (soft segment), where the styrene-based polymer portion forms physical crosslinks to serve as crosslinking points, while the conjugated diene-based polymer block imparts rubber elasticity. The double bonds of the conjugated diene-based polymer block (soft segment) may be partially or completely hydrogenated. Note that while the styrene-based thermoplastic elastomer (TPS) is thermoplastic, the rubber component (preferably, a diene-based rubber) is not thermoplastic. Therefore, in this specification, the styrene-based thermoplastic elastomer (TPS) is not included in the rubber component. The content of the styrene-based thermoplastic elastomer (TPS) is preferably in the range of 1 to 30 parts by mass per 100 parts by mass of the rubber component.

[0153] Examples of the styrene-based thermoplastic elastomer (TPS) include styrene / butadiene / styrene (SBS) block copolymers, styrene / isoprene / styrene (SIS) block copolymers, styrene / butadiene / isoprene / styrene (SBIS) block copolymers, styrene / butadiene (SB) block copolymers, styrene / isoprene (SI) block copolymers, styrene / butadiene / isoprene (SBI) block copolymers, styrene / ethylene / butylene / styrene (SEBS) block copolymers, styrene / ethylene / propylene / styrene (SEPS) block copolymers, styrene / ethylene / ethylene / propylene / styrene (SEEPS) block copolymers, styrene / ethylene / butylene (SEB) block copolymers, styrene / ethylene / propylene (SEP) block copolymers, and styrene / ethylene / ethylene / propylene (SEEP) block copolymers.

[0154] (Others) The rubber composition for a tire of this embodiment may contain the above-mentioned rubber component, resin component, filler, oil, and styrene-based thermoplastic elastomer, as well as various components commonly used in the rubber industry, as needed, such as silane coupling agents, antioxidants, waxes, processing aids, stearic acid, zinc oxide (zinc white), vulcanization accelerators, and vulcanizing agents, all of which may be appropriately selected within ranges that do not impair the object of the present invention. Commercially available products can be suitably used as these compounding ingredients.

[0155] When the rubber composition for a tire of this embodiment contains silica, it is preferable to contain a silane coupling agent to improve the effect of the silica. Examples of the silane coupling agent 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, Examples of the silane coupling agent include N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl 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. The content of the silane coupling agent is preferably in the range of 2 to 20 parts by mass, more preferably 5 to 15 parts by mass, per 100 parts by mass of the silica.

[0156] Examples of the antioxidant include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6C), 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (AW), N,N'-diphenyl-p-phenylenediamine (DPPD), etc. The content of the antioxidant is not particularly limited, and is preferably in the range of 0.1 to 5 parts by mass, and more preferably 1 to 4 parts by mass, per 100 parts by mass of the rubber component.

[0157] Examples of the wax include paraffin wax, microcrystalline wax, etc. The content of the wax is not particularly limited, but is preferably in the range of 0.1 to 5 parts by mass, and more preferably 1 to 4 parts by mass, per 100 parts by mass of the rubber component.

[0158] The content of the zinc oxide (zinc white) is not particularly limited, but is preferably in the range of 0.1 to 10 parts by mass, and more preferably 1 to 8 parts by mass, per 100 parts by mass of the rubber component.

[0159] Examples of the vulcanization accelerator include sulfenamide vulcanization accelerators, guanidine vulcanization accelerators, thiazole vulcanization accelerators, thiuram vulcanization accelerators, and dithiocarbamate vulcanization accelerators. These vulcanization accelerators may be used alone or in combination of two or more. The content of the vulcanization accelerator is not particularly limited, and is preferably in the range of 0.1 to 5 parts by mass, more preferably 0.2 to 4 parts by mass, per 100 parts by mass of the rubber component.

[0160] The vulcanizing agent may be sulfur, etc. The content of the vulcanizing agent is preferably in the range of 0.1 to 10 parts by mass, more preferably 1 to 4 parts by mass, in terms of sulfur content, per 100 parts by mass of the rubber component.

[0161] (Method for producing rubber composition for tire) The method for producing the rubber composition is not particularly limited, but the rubber composition can be produced, for example, by blending various components appropriately selected as necessary with the above-mentioned rubber component, resin component, and filler, and kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.

[0162] The conditions for the kneading are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of kneading device, etc. can be appropriately selected depending on the purpose. Examples of the kneading device include a Banbury mixer, an intermix, a kneader, a roll, etc. that are usually used for kneading rubber compositions.

[0163] The conditions for the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, and heat-in device can be appropriately selected depending on the purpose. Examples of the heat-in device include a heat-in roll mill typically used for heat-in of rubber compositions.

[0164] The extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of the extrusion device include an extruder typically used for extruding rubber compositions. The extrusion temperature can be appropriately determined.

[0165] The vulcanization apparatus, method, conditions, etc. are not particularly limited and can be appropriately selected depending on the purpose. Examples of vulcanization apparatus include a molding vulcanizer using a mold used for vulcanizing rubber compositions. The vulcanization temperature is, for example, about 100 to 190°C.

[0166] (Uses) The rubber composition for a tire of this embodiment can be applied to various constituent members of a tire, and can be used for, for example, tread (cap tread, base tread, undertread), cushion rubber, shoulder, side rubber, clinch, bead filler, carcass coating rubber, insulation, chafer, inner liner, etc., and can also be used for side reinforcing layers of run-flat tires, etc. Furthermore, the rubber composition for a tire of this embodiment can also be applied to rubber crawlers, seismic isolation rubber, etc., in addition to tires. Among these, the rubber composition for a tire of this embodiment is suitable as tire tread rubber.

[0167] <Tire tread rubber> The tire tread rubber of this embodiment is characterized by being made of the above-mentioned rubber composition for a tire of this embodiment. Since the tire tread rubber of this embodiment is made of the above-mentioned rubber composition for a tire, workability in production is improved while maintaining fracture resistance. The tire tread rubber of this embodiment may be applied to new tires or retread tires.

[0168] <Tire> The tire of this embodiment is characterized by including the tire tread rubber of this embodiment described above. Because the tire of this embodiment includes the tire tread rubber described above, productivity is improved while maintaining fracture resistance.

[0169] The tire of this embodiment may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, depending on the type of tire to be applied, or by molding a semi-vulcanized rubber that has been subjected to a pre-vulcanization step or the like and then further vulcanizing it. The tire of this embodiment is preferably a pneumatic tire, and the gas to be filled into the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium.

[0170] 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.

[0171] <Analysis Method of Rubber Component> The glass transition temperature (Tg) and bound styrene content of styrene-butadiene rubber were measured by the following methods. The SP values ​​(solubility parameters) of natural rubber (isoprene skeleton rubber) and styrene-butadiene rubber were calculated according to the Fedors method.

[0172] (1) Glass Transition Temperature (Tg) Using the synthesized styrene-butadiene rubber as a sample, a DSC curve was recorded using a DSC250 manufactured by TA Instruments, while increasing the temperature from −100° C. at a rate of 20° C. / min under a helium flow of 50 mL / min, and the peak top (inflection point) of the DSC differential curve was determined as the glass transition temperature.

[0173] (2) Bound Styrene Amount The synthesized styrene-butadiene rubber was used as a sample, and 100 mg of the sample was diluted with chloroform to 100 mL and dissolved to prepare a measurement sample. The amount of bound styrene (mass%) relative to 100 mass% of the sample was measured based on the amount of absorption at the ultraviolet absorption wavelength (near 254 nm) by the phenyl group of styrene. A spectrophotometer "UV-2450" manufactured by Shimadzu Corporation was used as the measurement device.

[0174] <Method of Analyzing Resin Component> The softening point and weight average molecular weight of the resin component were measured by the following methods: The SP value (solubility parameter) of the resin component was calculated according to the Fedors method.

[0175] (3) Softening Point The softening point of the resin component was measured in accordance with JIS-K2207-1996 (ring and ball method).

[0176] (4) Weight-average molecular weight The average molecular weight of the resin component was measured by gel permeation chromatography (GPC) under the following conditions, and the weight-average molecular weight in terms of polystyrene was calculated: Column temperature: 40°C Injection volume: 50 μL Carrier and flow rate: tetrahydrofuran 0.6 mL / min Sample preparation: Approximately 2.5 mg of the resin component was dissolved in 10 mL of tetrahydrofuran.

[0177] <Preparation and Evaluation of Rubber Compositions> Rubber compositions of Examples 1 to 5 and Comparative Examples 1 and 2 were prepared by blending and kneading the components according to the formulations shown in Table 1. The unvulcanized viscosity and fracture resistance of the resulting rubber compositions were evaluated by the following methods. The results are shown in Table 1. The unvulcanized viscosity and fracture resistance of Example 6 were calculated from the results of Examples 1 and 3.

[0178] (5) Unvulcanized Viscosity The unvulcanized viscosity of the rubber composition [Mooney viscosity ML １＋４ (130°C)] was measured and expressed as an index, with the reciprocal of the unvulcanized viscosity of Comparative Example 1 set as 100. A larger index value indicates a lower unvulcanized viscosity and better operability during kneading.

[0179] (6) Puncture Resistance The rubber composition obtained was vulcanized to obtain vulcanized rubber test pieces. A tensile test was conducted on the vulcanized rubber test pieces in accordance with JIS K6251 to measure the tensile stress at 300% elongation (M300), the tensile strength at break (Tb), and the elongation at break (Eb). The product of these values ​​(M300 x Tb x Eb) was used as an index of fracture resistance, and was expressed as an index with Comparative Example 1 set to 100. A larger index value indicates a larger product (M300 x Tb x Eb) and better fracture resistance.

[0180]

[0181] *1 Natural rubber: TSR #20, SP value = 8.20 (cal / cm ３ ) １／２ *2 Low Tg modified SBR: Hydrocarbyloxysilane compound modified styrene-butadiene rubber synthesized by the following method, Tg = -65 ° C., SP value = 8.65 (cal / cm ３ ) １／２ * 3 Silica: Tosoh Silica Corporation, trade name "Nipsil AQ" * 4 Carbon black: Asahi Carbon Co., Ltd., trade name "#80" * 5 Resin component: Hydrogenated C ５ based resin, manufactured by Eastman, trade name "Registered Trademark Impera E1780", softening point = 130°C, weight average molecular weight (Mw) = 909 g / mol, SP value = 8.35 (cal / cm ３ ) １／２ * 6 Oil: Idemitsu Kosan Co., Ltd., product name "Diana Process Oil NS-100" * 7 Silane coupling agent: Evonik Degussa Co., Ltd., product name "Si75" * 8 Anti-aging agent: Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrac 6C" * 9 Vulcanization system: Sulfur, vulcanization accelerator, stearic acid, and zinc oxide mixed in equal proportions

[0182] <Method for synthesizing low-Tg modified SBR (*2)> 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. To the polymerization reaction system, which had reached a polymerization conversion rate of nearly 100%, 0.72 mmol of N,N-bis(trimethylsilyl)-3-[diethoxy(methyl)silyl]propylamine was added as a modifier, and the modification reaction was carried out at 50°C for 30 minutes. Thereafter, 2 mL of a 5% by mass solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol was added to terminate the reaction, and the mixture was dried in a conventional manner to obtain a modified SBR. Measurement of the microstructure of the resulting modified SBR revealed that the bound styrene content was 10% by mass and the glass transition temperature (Tg) was -65°C.

[0183] It can be seen from Table 1 that the rubber compositions of the examples according to the present invention were able to reduce the unvulcanized viscosity while maintaining fracture resistance. On the other hand, the rubber composition of Comparative Example 2, in which [(parts by mass of resin component - parts by mass of oil) / parts by mass of isoprene skeleton rubber] was less than 0.70, had a lower unvulcanized viscosity than the rubber composition of Comparative Example 1, but showed a significant decrease in fracture resistance.

[0184] The rubber composition for tires of the present invention is suitable as a tread rubber for tires.

Claims

1. A rubber composition for tires, comprising a rubber component, a resin component, and a filler, with or without oil, wherein the rubber component comprises an isoprene-skeleton rubber and a styrene-butadiene rubber, the content of the resin component is 1 part by mass or more and less than 50 parts by mass per 100 parts by mass of the rubber component, the resin component is at least partially hydrogenated, and the rubber composition for tires satisfies the following formula (1): 0.70≦(parts by mass of the resin component−parts by mass of the oil) / parts by mass of the isoprene-skeleton rubber≦1.18 ... (1).

2. The rubber composition for tires according to claim 1, wherein the styrene-butadiene rubber has a glass transition temperature of less than -40°C.

3. The resin component has an SP value difference of 1.40 (cal / cm) from the isoprene skeleton rubber. ３ ) １／２ 2. The rubber composition for tires according to claim 1, wherein:

4. The resin component has an SP value difference of 0.50 (cal / cm) from the isoprene skeleton rubber. ３ ) １／２ The rubber composition for tires according to claim 3, wherein:

5. The difference in SP value between the isoprene skeleton rubber and the styrene-butadiene rubber is 0.3 (cal / cm ３ ) １／２ The rubber composition for tires according to claim 1 .

6. The rubber composition for tires according to claim 1, wherein the content of the isoprene skeleton rubber is 1 to 80 parts by mass per 100 parts by mass of the rubber component.

7. The rubber composition for tires according to claim 6, wherein the content of the isoprene skeleton rubber is 1 to 40 parts by mass per 100 parts by mass of the rubber component.

8. The rubber composition for tires according to claim 1, wherein the styrene-butadiene rubber is modified with a modifier having a functional group containing a nitrogen atom and an alkoxy group.

9. The rubber composition for tires according to claim 1, wherein the resin component has a softening point higher than 110° C. and a weight average molecular weight in terms of polystyrene of 200 to 1600 g / mol.

10. The rubber composition for tires according to claim 9, wherein the resin component has a weight average molecular weight in terms of polystyrene of 200 to 1200 g / mol.

11. The resin component is hydrogenated C ５ based resin, hydrogenated C ５ -C ９ 2. The rubber composition for tires according to claim 1, wherein the rubber component is at least one selected from the group consisting of a cyclopentadiene-based resin, a hydrogenated dicyclopentadiene-based resin, and a hydrogenated terpene-based resin.

12. The rubber composition for tires according to claim 1, which satisfies the following formula (1'): 0.79≦(parts by mass of the resin component−parts by mass of the oil) / parts by mass of the isoprene-skeleton rubber≦1.00 (1').

13. A tread rubber for tires, comprising the rubber composition for tires according to any one of claims 1 to 12.

14. A tire comprising a tire tread rubber according to claim 13.

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