Tire rubber composition, tread rubber, and tire

Abstract

Provided is a tire rubber composition that has both excellent wet-grip properties on dense graded asphalt pavement and excellent wet-grip properties on porous asphalt pavement, and has high road surface robustness. This tire rubber composition is characterized in by comprising: a rubber component containing an isoprene-based rubber (A) having a glass transition temperature of at most -50°C; a reinforcing filler (B); and a resin component (C). The rubber composition is characterized in that: the proportion of the isoprene-based rubber (A) in 100 parts by mass of the rubber component is not less than 15 parts by mass but less than 50 parts by mass; the resin component (C) is at least partially hydrogenated, and the difference in SP value between the resin component (C) and the isoprene-based rubber (A) is at most 1.40 (cal / cm3)1 / 2; and composition parameter P1 calculated from predetermined formula (I-1) is at least 1000, and composition parameter P2 calculated from predetermined formula (I-2) is at least 0.25.

Description

Rubber composition for tires, tread rubber and tires

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

[0002] BACKGROUND ART 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").

[0003] For example, Patent Document 1 listed 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 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.

[0004] International Publication No. 2015 / 079703

[0005] Here, wet grip performance is required not only for dense-graded asphalt pavements that are common in general areas, but also for porous asphalt pavements that are found in snowy, cold regions.

[0006] However, after investigations by the present inventors, it was found that the rubber composition described in Patent Document 1 has room for further improvement in terms of achieving high levels of wet grip performance for both dense-graded asphalt pavement and porous asphalt pavement.

[0007] 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 can provide a tire with excellent wet grip performance on both dense-graded asphalt pavement and porous asphalt pavement and high road surface robustness, and a tread rubber made of such a rubber composition.A further object of the present invention is to provide a tire with excellent wet grip performance on both dense-graded asphalt pavement and porous asphalt pavement and high road surface robustness.

[0008] The gist and configuration of the present invention to solve the above problems is as follows.

[0009] [1] A rubber composition for tires, comprising a rubber component containing an isoprene-based rubber (A) having a glass transition temperature of −50° C. or lower, a reinforcing filler (B), and a resin component (C), wherein the proportion of the isoprene-based rubber (A) in 100 parts by mass of the rubber component is 15 parts by mass or more and less than 50 parts by mass, and the resin component (C) is at least partially hydrogenated, and the difference in SP value between the isoprene-based rubber (A) and the resin component (C) is 1.40 (cal / cm ３ ) １／２ a rubber composition for a tire, characterized in that, when the diene rubber component is taken as 100 parts by mass, a composition parameter P1 calculated from the following formula (I-1): composition parameter P1=(number of parts by mass of isoprene-based rubber (A))×(number of parts by mass of resin component (C)) ... (I-1) is 1,000 or more, and a composition parameter P2 calculated from the following formula (I-2): composition parameter P2={(number of parts by mass of resin component (C)) / (number of parts by mass of isoprene-based rubber (A))}×(mass fraction of reinforcing filler (B) in the rubber composition) ... (I-2) is 0.25 or more.

[0010] [2] The difference in SP value between the resin component (C) and the isoprene-based rubber (A) is 0.50 (cal / cm ３ ) １／２ The rubber composition for a tire according to [1] below.

[0011] [3] The rubber composition for a tire according to [1] or [2], wherein the reinforcing filler (B) contains silica.

[0012] [4] The rubber composition for a tire according to any one of [1] to [3], wherein the resin component (C) has a softening point higher than 110°C and a weight average molecular weight in terms of polystyrene of 200 to 1600 g / mol.

[0013] [5] The rubber composition for a tire according to any one of [1] to [4], wherein the content of the resin component (C) is 35 parts by mass or more per 100 parts by mass of the rubber component.

[0014] [6] A tread rubber comprising the rubber composition for tires according to any one of [1] to [5].

[0015] [7] A tire characterized by comprising the tread rubber according to [6].

[0016] According to the present invention, it is possible to provide a rubber composition for a tire that can provide a tire with excellent wet grip performance on both dense-graded asphalt pavement and porous asphalt pavement, and high road surface robustness, and a tread rubber made of such a rubber composition. Furthermore, according to the present invention, it is possible to provide a tire with excellent wet grip performance on both dense-graded asphalt pavement and porous asphalt pavement, and high road surface robustness.

[0017] The rubber composition for a tire, tread rubber, and tire of the present invention will be described in detail below by way of example based on embodiments. The compounds described in this specification may be derived partially or entirely from fossil resources, from biological resources such as plant resources, or from recycled resources such as used tires. They may also be derived from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0018] <Rubber Composition for Tire> The rubber composition for tire of the present invention contains a rubber component, a reinforcing filler (B), and a resin component (C). The rubber component in the rubber composition for tire of the present invention includes an isoprene-based rubber (A) having a glass transition temperature of −50° C. or lower, the proportion of the isoprene-based rubber (A) in 100 parts by mass of the rubber component is 15 parts by mass or more and less than 50 parts by mass, the resin component (C) is at least partially hydrogenated, and the difference in SP value between the isoprene-based rubber and the resin component (C) is 1.40 (cal / cm ３ ) １／２When the diene rubber component is taken as 100 parts by mass, the composition parameter P1 calculated from the following formula (I-1): composition parameter P1=(number of parts by mass of isoprene rubber (A))×(number of parts by mass of resin component (C)) ... (I-1) is 1,000 or more, and the composition parameter P2 calculated from the following formula (I-2): composition parameter P2={(number of parts by mass of resin component (C)) / (number of parts by mass of isoprene rubber (A))}×(mass fraction of reinforcing filler (B) in the rubber composition) ... (I-2) is 0.25 or more.

[0019] In this specification, the glass transition temperature of a rubber component such as an isoprene-based rubber (A) is determined by recording a DSC curve while increasing the temperature within a predetermined temperature range, and taking the peak top (inflection point) of the DSC differential curve in accordance with ISO 22768: 2006. In addition, in this specification, the SP values ​​(solubility parameters) of a rubber component such as an isoprene-based rubber (A) and a resin component (C) are calculated according to the Fedors method.

[0020] The rubber composition for tires of the present invention is at least partially hydrogenated, and the difference in SP value from the isoprene-based rubber (A) is 1.40 (cal / cm ３ ) １／２The basic wet grip performance of a tire can be improved by using the following resin component (C) in combination with the isoprene-based rubber (A). It has been confirmed that the ratio of the mass parts of the resin component (C) to the isoprene-based rubber (A) contributes to road-following performance on all road surfaces, including dense-graded asphalt pavement and porous asphalt pavement. It has also been confirmed that the product of the mass parts of the resin component (C) and the isoprene-based rubber (A) contributes to wet grip performance. Meanwhile, the reinforcing filler (B) contributes to suppressing block deformation and thus to braking force. Therefore, the present inventors have focused on the correlation between the composition of these components and road surface robustness and conducted extensive research. As a result, by establishing the above-mentioned "composition parameter P1" and "composition parameter P2" and appropriately adjusting the composition of the rubber component, reinforcing filler (B), resin component (C), and other components that make up the rubber composition so that the composition parameter P1 is 1000 or more and the composition parameter P2 is 0.25 or more, it was found that it is possible to improve the wet grip performance on porous asphalt pavement while maintaining the wet grip performance on dense-graded asphalt pavement commonly used in general areas at the same level as before, and also improve the wet grip performance on porous asphalt pavement. Therefore, by applying the rubber composition for tires of the present invention to tires, it is possible to achieve a high level of balance between the wet grip performance on dense-graded asphalt pavement and the wet grip performance on porous asphalt pavement, thereby improving road surface robustness.

[0021] In the formula for composition parameter P2, the value of the reinforcing filler (B) is used as the mass fraction in the rubber composition, rather than the number of parts by mass per 100 parts by mass of the rubber component. In other words, it should be noted that this value is also affected by the contents of various components, such as vulcanizing agents and vulcanization accelerators, that may be blended in addition to the rubber component and resin component (C).

[0022] From the viewpoint of further improving wet grip performance, the rubber composition for a tire of the present invention has a composition parameter P1 calculated from the above formula (I-1) of preferably 1200 or more, more preferably 1350 or more, and even more preferably 1500 or more. On the other hand, from the viewpoint of sufficiently maintaining other performances such as abrasion resistance and fuel economy, the composition parameter P1 calculated from the above formula (I-1) can be set to 2200 or less.

[0023] In the rubber composition for a tire of the present invention, from the viewpoint of further improving road surface robustness, the composition parameter P2 calculated from the above formula (I-2) is preferably 0.35 or more, more preferably 0.40 or more, and even more preferably 0.45 or more. On the other hand, from the viewpoint of sufficiently maintaining other performance properties such as abrasion resistance and fuel economy, the composition parameter P2 calculated from the above formula (I-2) can be 0.80 or less.

[0024] (Rubber Component) The rubber composition for a tire of the present invention contains a rubber component, and as the rubber component, an isoprene-based rubber (A) having a glass transition temperature of −50° C. or lower and another rubber component other than the isoprene-based rubber (A) (hereinafter, sometimes simply referred to as “another rubber component”) are used in combination.

[0025] -Isoprene-based rubber (A)- The isoprene-based rubber (A) is a rubber whose main skeleton is an isoprene unit, and specific examples thereof include natural rubber (NR) and synthetic isoprene rubber (IR). When the rubber component contains the isoprene-based rubber (A), the breaking strength of the rubber composition can be increased. In addition, the isoprene-based rubber (A) has a glass transition temperature of -50°C or lower. The isoprene-based rubber (A) may be used alone or in combination of two or more types.

[0026] The proportion of the isoprene-based rubber (A) in 100 parts by mass of the rubber component is 15 parts by mass or more but less than 50 parts by mass. If the proportion is less than 15 parts by mass or more than 50 parts by mass, the wet grip performance on dense-graded asphalt road surfaces and / or the wet grip performance on porous asphalt pavements becomes insufficient, and road surface robustness deteriorates. From the viewpoint of further improving road surface robustness, the proportion of the isoprene-based rubber (A) in 100 parts by mass of the rubber component is preferably 25 parts by mass or more, preferably 45 parts by mass or less, and more preferably 40 parts by mass or less.

[0027] -Other Rubber Components- Examples of other rubber components other than the isoprene-based rubber (A) include isoprene-based rubbers having a glass transition temperature higher than -50°C, styrene-butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), halogenated butyl rubber, ethylene-propylene rubber (EPR, EPDM), fluororubber, silicone rubber, and urethane rubber. Among these, as the other rubber component, diene-based rubbers such as styrene-butadiene rubber, butadiene rubber, and chloroprene rubber are preferred, and styrene-butadiene rubber is more preferred. These other rubber components other than the isoprene-based rubber (A) may be used alone or in combination of two or more. Furthermore, the other rubber components other than the isoprene-based rubber (A) may be unmodified or modified.

[0028] The glass transition temperature of the other rubber component is preferably less than −30° C., more preferably less than −40° C., more preferably −45° C. or less, even more preferably −50° C. or less, and preferably higher than −90° C. If the glass transition temperature of the other rubber component is lower than −30° C., the fuel economy and wear resistance of a tire using the rubber composition can be improved. Furthermore, a rubber component having a glass transition temperature higher than −90° C. is easy to synthesize.

[0029] The difference in SP value between the isoprene-based rubber (A) and other rubber components 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-based rubber (A) and the other rubber component is 0.3 (cal / cm ３ ) １／２ In the above cases, the isoprene-based rubber (A) and the other rubber components tend to become incompatible with each other.

[0030] When styrene-butadiene rubber is used as the other rubber component, 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. When the bound styrene content of the styrene-butadiene rubber is less than 15% by mass, the glass transition temperature tends 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.

[0031] When styrene-butadiene rubber is used as the other rubber component, 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 the wet grip performance, fuel economy, and wear resistance of a tire to which the rubber composition is applied is improved, and in particular, the fuel economy and wear resistance can be further 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.

[0032] --Modified Styrene-Butadiene Rubber of First Preferred Embodiment-- The styrene-butadiene rubber (SBR) is preferably modified with an aminoalkoxysilane compound, and more preferably has its terminals modified with an aminoalkoxysilane compound from the viewpoint of having a high affinity for the reinforcing filler (B). When the terminals of the styrene-butadiene rubber are modified with an aminoalkoxysilane compound, the interaction between the modified styrene-butadiene rubber and the reinforcing filler (B) (particularly silica) becomes particularly strong.

[0033] 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.

[0034] 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.

[0035] 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)

[0036] 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.

[0037] The aminoalkoxysilane compound is also preferably an aminoalkoxysilane compound represented by the following general formula (ii):

[0038] 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.

[0039] The aminoalkoxysilane compound represented by the above general formula (ii) is preferably an aminoalkoxysilane compound represented by the following general formula (iii).

[0040] 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 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.

[0041] 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).

[0042] 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.

[0043]

[0044] 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.

[0045] 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):

[0046] 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).

[0047]

[0048] 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.

[0049] 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).

[0050] 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.

[0051]

[0052] 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.

[0053] 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).

[0054] 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.

[0055] 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.

[0056] --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.

[0057] In the above general formula (I), R １ , R ２and R ３ 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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 abrasion 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.

[0065] 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.

[0066] 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").

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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)].

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] B in the general formulae (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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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).

[0090] 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.

[0091] 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.

[0092] --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):

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] The compound represented by formula (1) can be produced through a condensation reaction represented by the following reaction scheme.

[0104] 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:

[0105] 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.

[0106] 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.

[0107] 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).

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113]

[0114] 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.

[0115]

[0116] 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.

[0117] 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.

[0118] 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).

[0119] 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.

[0120] (Reinforcing Filler (B)) The rubber composition for a tire of the present invention contains a reinforcing filler (B). By containing the reinforcing filler (B), the reinforcing property of the rubber composition is improved. Examples of the reinforcing filler (B) include silica, carbon black, clay, talc, calcium carbonate, and aluminum hydroxide. The reinforcing filler (B) may be used alone or in combination of two or more.

[0121] The content of the reinforcing filler (B) in the rubber composition is not particularly limited as long as the composition parameter P2 calculated from formula (I-2) is a predetermined value or more. However, the content of the reinforcing filler (B) in the rubber composition is preferably 40 parts by mass or more and 125 parts by mass or less per 100 parts by mass of the rubber component. When the content of the reinforcing filler (B) per 100 parts by mass of the rubber component is 40 parts by mass or more, wet grip performance, particularly wet grip performance on porous asphalt pavement, can be further improved, and when it is 125 parts by mass or less, the elastic modulus of the rubber composition does not become too high, and the deterioration of wet grip performance of tires using the rubber composition on various road surfaces can be more sufficiently suppressed. From the same viewpoint, the content of the reinforcing filler (B) per 100 parts by mass of the rubber component is more preferably 55 parts by mass or more, more preferably 65 parts by mass or more, more preferably 70 parts by mass or more, even more preferably 75 parts by mass or more, particularly preferably 80 parts by mass or more, and is more preferably 105 parts by mass or less, and more preferably 100 parts by mass or less.

[0122] The reinforcing filler (B) preferably contains silica. By using silica, road surface robustness can be more effectively improved. Examples of silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc., and among these, wet silica is preferred. These silicas may be used alone or in combination of two or more.

[0123] In addition, when silica is used, the silica has a nitrogen adsorption specific surface area (BET method) of 80 m ２ / g or more 330m ２ It is more preferable that the nitrogen adsorption specific surface area (BET method) of silica is less than 80 m 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 reduced. ２From the same viewpoint, when the nitrogen adsorption specific surface area (BET method) of silica is less than 110 m / g, deterioration of wet grip performance of a tire to which the rubber composition is applied on various road surfaces can be more sufficiently suppressed. 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.

[0124] (Resin Component (C)) The rubber composition for a tire of the present invention contains a resin component (C). The resin component (C) is at least partially hydrogenated, and the difference in SP value between the resin component (C) and the isoprene-based rubber (A) is 1.40 (cal / cm ３ ) １／２ Such a resin component (C) has high compatibility with the isoprene-based rubber (A), controls the mobility of the rubber component, and can improve the hysteresis loss (tan δ) in the low temperature range, thereby improving the basic wet grip performance of a tire to which the rubber composition is applied. Note that, from the viewpoint of further improving compatibility, the difference in SP value between the resin component (C) and the isoprene-based rubber (A) is set to 1.35 (cal / cm 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 particularly preferred that:

[0125] The content of the resin component (C) is not particularly limited as long as the composition parameter P1 calculated from formula (I-1) and the composition parameter P2 calculated from formula (I-2) are each equal to or greater than a predetermined value. However, the content of the resin component (C) in the rubber composition is preferably 35 parts by mass or more per 100 parts by mass of the rubber component. When the content of the resin component (C) per 100 parts by mass of the rubber component is 35 parts by mass or more, wet grip performance, particularly wet grip performance on porous asphalt pavement, can be further improved. From the same viewpoint, the content of the resin component (C) per 100 parts by mass of the rubber component is more preferably more than 35 parts by mass, more preferably 45 parts by mass or more, more preferably 50 parts by mass or more, more preferably more than 50 parts by mass, more preferably 51 parts by mass or more, even more preferably 53 parts by mass or more, and even more preferably 55 parts by mass or more. Furthermore, the content of the resin component (C) per 100 parts by mass of the rubber component is preferably 70 parts by mass or less. In this case, the resin component (C) is less likely to precipitate from the tire, and therefore the effects of the resin component (C) can be fully exerted, and deterioration of the tire appearance can be suppressed.

[0126] The resin component (C) preferably has a softening point higher than 110° C. and a weight average molecular weight in terms of polystyrene of 200 to 1600 g / mol. By applying a rubber composition containing such a resin component (C) to a tire, the wear resistance of the tire can be improved.

[0127] If the softening point of the resin component (C) is higher than 110°C, the tire to which the rubber composition is applied can be sufficiently reinforced and the wear resistance can be improved. From the viewpoint of the wear resistance of the tire, the softening point of the resin component (C) 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 (C) is preferably 160°C or lower, more preferably 150°C or lower, more preferably 145°C or lower, even 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 (C) is 200 g / mol or more, the resin component (C) is less likely to precipitate from the tire and the effects of the resin component (C) can be fully exhibited, and when it is 1600 g / mol or less, the resin component (C) is more likely to be compatible with the rubber component. From the viewpoint of suppressing the precipitation of the resin component (C) from the tire and suppressing deterioration of the tire appearance, the polystyrene-equivalent weight-average molecular weight of the resin component (C) 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 (C) with the rubber component and further enhancing the effects of the resin component (C), the polystyrene-equivalent weight average molecular weight of the resin component (C) 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.

[0129] The weight average molecular weight (Mw ＨＲ ) (unit: g / mol) of the resin component (C) 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, even more preferably 0.14 or more, and even more preferably 0.141 or more. ＨＲ / MwＨＲ ) is preferably 0.25 or less, more preferably 0.24 or less, even more preferably 0.23 or less, even more preferably 0.19 or less, even more preferably 0.18 or less, and particularly preferably 0.17 or less.

[0130] The softening point of resin component (C) is measured in accordance with JIS-K2207-1996 (ring and ball method), and the weight average molecular weight of resin component (C) in terms of polystyrene is measured by gel permeation chromatography (GPC).

[0131] The above-mentioned at least partially hydrogenated resin component (C) means a resin obtained by reducing and hydrogenating a resin. The resins that can be used as raw materials for the hydrogenated resin component (C) 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.

[0132] 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.

[0133] C ５ -C ９ The C-based resin is ５ -C ９ It refers to synthetic petroleum resin, ５ -C ９ Examples of the resins include petroleum-derived C ５ -C１１ 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.

[0134] 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.

[0135] Terpene resins are solid resins obtained by blending turpentine, which is obtained simultaneously with the extraction of rosin from pine trees, or polymerization components separated therefrom, and polymerizing them using a Friedel-Crafts catalyst. Examples 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 with formalin. There are no particular restrictions 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.

[0136] Dicyclopentadiene resins include, for example, AlCl ３ or BF ３ This refers to a resin obtained by polymerizing dicyclopentadiene using a Friedel-Crafts catalyst such as

[0137] The resin used as the raw material for the hydrogenated resin component (C) 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 in the resin.

[0138] In order to enhance the compatibility between the rubber component containing the isoprene-based rubber (A) and the resin component (C), to further improve the wet grip performance of a tire using the rubber composition, and to reduce the rolling resistance, the resin component (C) is preferably a hydrogenated C ５ based resin, hydrogenated C ５ -C ９ The resin is preferably at least one selected from the group consisting of hydrogenated dicyclopentadiene-based resins (hydrogenated DCPD-based resins), hydrogenated terpene-based 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 Furthermore, the resin component (C) is preferably a resin having a hydrogenated DCPD structure or a hydrogenated cyclic structure in at least one monomer.

[0139] The rubber composition for tires of the present invention 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), with the styrene-based polymer portion forming physical crosslinks and serving 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.

[0140] 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.

[0141] (Others) In addition to the rubber component, reinforcing filler (B), resin component (C), and styrene-based thermoplastic elastomer described above, the rubber composition for tires of the present invention may contain, as necessary, various components commonly used in the rubber industry, such as silane coupling agents, antioxidants, waxes, softeners, processing aids, stearic acid, zinc oxide (zinc white), vulcanization accelerators, vulcanizing agents, etc., which are 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.

[0142] When the rubber composition for a tire of the present invention contains silica, the rubber composition preferably contains 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.

[0143] 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.

[0144] Examples of waxes 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.

[0145] The content of 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.

[0146] 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.

[0147] Examples of the vulcanizing agent include 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.

[0148] (Method for Producing Rubber Composition) 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, reinforcing filler (B), and resin component (C), and kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.

[0149] 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.

[0150] 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 roller typically used for heat-in of a rubber composition.

[0151] 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.

[0152] 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.

[0153] <Tread Rubber> The tread rubber of the present invention is characterized by comprising the above-mentioned rubber composition for tires. Because the tread rubber of the present invention comprises the above-mentioned rubber composition for tires, by applying it to tires, the tire's wet grip performance on dense-graded asphalt pavement and the wet grip performance on porous asphalt pavement can be improved, and road surface robustness can be increased. The tread rubber of the present invention may be applied to new tires or retread tires.

[0154] <Tire> The tire of the present invention is characterized by including the above-mentioned tread rubber. Because the tire of the present invention includes the above-mentioned tread rubber, it has excellent wet grip performance on both dense-graded asphalt pavement and porous asphalt pavement, and is highly robust on road surfaces.

[0155] Depending on the type of tire to be applied, the tire of the present invention may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, 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 the present invention 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.

[0156] 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.

[0157] <Analysis Method of Rubber Component> The glass transition temperature (Tg) of the rubber component and the bound styrene content of the styrene-butadiene rubber were measured by the following methods. The SP values ​​(solubility parameters) of the natural rubber (isoprene-based rubber (A)) and the styrene-butadiene rubber were calculated according to the Fedors method.

[0158] (1) Glass Transition Temperature (Tg) Using a rubber component 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 taken as the glass transition temperature.

[0159] (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.

[0160] <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.

[0161] (3) Softening Point The softening point of the resin component was measured in accordance with JIS-K2207-1996 (ring and ball method).

[0162] (4) Weight-average molecular weight The average molecular weight of the hydrogenated resin 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: About 2.5 mg of the resin component was dissolved in 10 mL of tetrahydrofuran.

[0163] <Preparation of Rubber Composition> According to the compounding recipes shown in Table 1, the components were compounded and kneaded to prepare rubber compositions of Examples and Comparative Examples.

[0164] <Preparation and Evaluation of Vulcanized Rubber> The rubber compositions of the examples and comparative examples were vulcanized to obtain vulcanized rubber test pieces. The wet grip performance of the vulcanized rubber test pieces was evaluated by the following method.

[0165] (5) Wet Grip Performance (Dense Gradient Asphalt Pavement and Porous Asphalt Pavement) Using a portable friction tester, the coefficient of friction of the test specimens for dense-graded asphalt pavement and porous asphalt pavement was measured. The evaluation results were expressed as an index, with the coefficient of friction for the dense-graded asphalt pavement of Comparative Example 1 set at 100. In each example, the sum of the index value of the friction coefficient for the dense-graded asphalt pavement and the index value of the friction coefficient for the porous asphalt pavement was used as the overall index of wet grip performance. The larger the index value, the larger the friction coefficient and the better the wet grip performance.

[0166]

[0167] * 1 Isoprene rubber (A): Natural rubber, "TSR #20", Tg = -56 ° C, SP value = 8.20 (cal / cm ３ ) １／２*2 Modified SBR1: Hydrocarbyloxysilane compound-modified styrene-butadiene rubber synthesized by the following method, Tg = -65 ° C., SP value = 8.65 (cal / cm ３ ) １／２ * 3 Modified SBR2: Modified styrene-butadiene rubber obtained by modifying the terminals of styrene-butadiene rubber obtained using butyl lithium as an initiator with N-(1,3-dimethylbutylidene)-3-triethoxysilyl-1-propanamine, bound styrene content = 35% by mass, Tg = -38 ° C, SP value = 8.95 (cal / cm ３ ) １／２ * 4 Reinforcing filler (B): Silica, manufactured by Tosoh Silica Corporation, trade name "Nipsil AQ" * 5 Resin component (C): 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 Silane coupling agent: Evonik Degussa, trade name "Si75" * 7 Anti-aging agent: Ouchi Shinko Chemical Industry Co., Ltd., trade name "Nocrac 6C" * 8 Wax: Nippon Seiro Co., Ltd., trade name "Ozoace 0701" * 9 Vulcanization accelerator 1: Ouchi Shinko Chemical Industry Co., Ltd., trade name "Nocceler DM-P" * 10 Vulcanization accelerator 2: Sanshin Chemical Industry Co., Ltd., trade name "Suncerer NS-G"

[0168] <Method for Synthesizing Modified SBR1 (*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. 0.09 mmol of 2,2-ditetrahydrofurylpropane and 0.7 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%, 0.63 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 Modified SBR1. The microstructure of the resulting modified SBR1 was measured, and as a result, the amount of bound styrene was 10% by mass, and the glass transition temperature (Tg) was -65°C.

[0169] From Table 1, it can be seen that the rubber compositions of the examples according to the present invention are excellent in wet grip performance on both dense-graded asphalt pavement and porous asphalt pavement, and can improve the road surface robustness of tires. On the other hand, it can be seen that the rubber compositions of the comparative examples do not simultaneously satisfy the requirements of at least the composition parameters (P1, P2), and therefore have poor wet grip performance.

[0170] According to the present invention, it is possible to provide a rubber composition for a tire that can provide a tire with excellent wet grip performance on both dense-graded asphalt pavement and porous asphalt pavement, and high road surface robustness, and a tread rubber made of such a rubber composition. Furthermore, according to the present invention, it is possible to provide a tire with excellent wet grip performance on both dense-graded asphalt pavement and porous asphalt pavement, and high road surface robustness.

Claims

1. A rubber composition for tires containing a rubber component containing an isoprene rubber (A) having a glass transition temperature of -50°C or lower, a reinforcing filler (B), and a resin component (C), wherein the proportion of the isoprene rubber (A) in 100 parts by mass of the rubber component is 15 parts by mass or more and less than 50 parts by mass, the resin component (C) is at least partially hydrogenated, and the difference in SP value from the isoprene rubber (A) is 1.40 (cal / cm ３ ) １／２ or less, when the diene rubber component is 100 parts by mass, the following formula (I-1): Composition parameter P1 = (number of parts by mass of isoprene rubber (A)) × (number of parts by mass of resin component (C))... (I-1) the composition parameter P1 calculated therefrom is 1000 or more, the following formula (I-2): Composition parameter P2 = {(number of parts by mass of resin component (C)) / (number of parts by mass of isoprene rubber (A))} × (mass fraction of reinforcing filler (B) in the rubber composition)... (I-2) the composition parameter P2 calculated therefrom is 0.25 or more, a rubber composition for tires, characterized in that.

2. The difference in SP value between the resin component (C) and the isoprene rubber (A) is 0.50 (cal / cm ３ ) １／２ or less, the rubber composition for tires according to claim 1.

3. The rubber composition for tires according to claim 1 or 2, wherein the reinforcing filler (B) contains silica.

4. The resin component (C) has a softening point higher than 110°C and a polystyrene-equivalent weight average molecular weight of 200 to 1600 g / mol, the rubber composition for tires according to claim 1.

5. The rubber composition for tires according to claim 1, wherein the content of the resin component (C) is 35 parts by mass or more with respect to 100 parts by mass of the rubber component.

6. A tread rubber comprising the rubber composition for tires according to claim 1.

7. A tire comprising the tread rubber according to claim 6.