JP2014231550A - Rubber composition for tire and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire excellent in wet grip performance, rigidity and wear resistance.SOLUTION: Provided is a rubber composition for a tire comprising: diene rubber (A); silica (B); an aromatic modified terpene resin (C); and a low molecular weight styrene-butadiene copolymer (D), and in which the diene rubber (A) includes conjugated diene rubber (A1), the conjugated diene rubber (A1) includes a specified structure (a) by 5 mass% or more, the content of the conjugated diene rubber (A) is 30 mass% or more to the content of the diene rubber (A), the content of the silica (B) is 60 to 170 pts.mass to 100 pts.mass of the diene rubber (A), the content of the aromatic modified terpene resin (C) is 10 to 50 pts.mass to 100 pts.mass of the diene rubber (A), and the content of the low molecular weight styrene-butadiene copolymer (D) is 5 to 100 pts.mass to 100 pts.mass of the diene rubber (A).

Description

  The present invention relates to a tire rubber composition and a pneumatic tire.

In recent years, improvement in wet grip performance (braking performance on a wet road surface) has been demanded from the viewpoint of safety during vehicle travel. On the other hand, a method is known in which silica is mixed with a rubber component constituting a tread portion of a tire to improve wet grip performance.
However, since silica has a low affinity with the rubber component and has high cohesiveness between silicas, even if silica is simply added to the rubber component, the silica does not disperse, and the effect of improving wet grip performance is sufficient. There was a problem that it could not be obtained.

  Under such circumstances, Patent Document 1 discloses a rubber composition containing a conjugated diene rubber having an isoprene block. According to Patent Document 1, it is described that by using the above composition, the affinity between silica and rubber is improved, and wet grip properties can be improved.

International Publication No. 2011/105362

On the other hand, in recent years, in order to improve safety and the like, further improvement in wet grip performance of tires is desired. In particular, competition wet tires are required to have a very high level of wet grip performance.
In addition to the wet grip performance, tires (particularly competition wet tires) are required to have various characteristics such as rigidity and wear resistance.
When the present inventor examined the rubber composition described in Patent Document 1, at least one of the properties of wet grip performance, rigidity, and wear resistance does not satisfy the level required recently. Became clear.
In view of the above circumstances, an object of the present invention is to provide a tire rubber composition that is excellent in wet grip performance, rigidity, and wear resistance when formed into a tire.

As a result of intensive studies on the above problems, the present inventors have used a specific conjugated diene rubber, silica, a specific aromatic modified terpene resin, and a low-molecular-weight styrene-butadiene copolymer in combination. As a result, it was found that a rubber composition for a tire excellent in wet grip performance, rigidity and abrasion resistance can be obtained, and the present invention has been achieved.
That is, the present inventors have found that the above problem can be solved by the following configuration.

(1) A diene rubber (A) having a weight average molecular weight of 100,000 to 3,000,000, silica (B), an aromatic modified terpene resin (C) having a softening point of 60 to 180 ° C., A low molecular weight styrene-butadiene copolymer (D) having a weight average molecular weight of 2,000 to 20,000,
The diene rubber (A) includes a conjugated diene rubber (A1),
Three or more conjugated diene polymer chains (a1) obtained by reacting the conjugated diene rubber (A1) with a conjugated diene polymer chain (a1) and a modifier (a2) are the modifier. Containing 5 mass% or more of the structure (a) formed by bonding via (a2),
The conjugated diene polymer chain (a1) has an isoprene block containing 70% by mass or more of isoprene units at one end, has an active end at the other end,
The styrene unit content of the part other than the isoprene block in the conjugated diene polymer chain (a1) is 35 to 45% by mass,
The modifier (a2) has an epoxy group and / or a hydrocarbyloxysilyl group, and the total number of the epoxy group and the hydrocarbyloxy group contained in the hydrocarbyloxysilyl group is 3 or more. Yes,
The diene rubber (A) has an average glass transition temperature of −35 ° C. or higher,
The content of the conjugated diene rubber (A1) is 30% by mass or more with respect to the content of the diene rubber (A).
Content of the said silica (B) is 60-170 mass parts with respect to 100 mass parts of said diene rubbers (A),
The content of the aromatic modified terpene resin (C) is 10 to 50 parts by mass with respect to 100 parts by mass of the diene rubber (A).
The rubber composition for tires, wherein the content of the low molecular weight styrene-butadiene copolymer (D) is 5 to 100 parts by mass with respect to 100 parts by mass of the diene rubber (A).
(2) Further, carbon black having a nitrogen adsorption specific surface area of 100 to 400 m ² / g is contained,
The styrene unit content of the low molecular weight styrene-butadiene copolymer (D) is 20 to 40% by mass,
The rubber composition for tires according to (1) above, wherein a vinyl bond content in a butadiene monomer unit of the low molecular weight styrene-butadiene copolymer (D) is 40 to 70%.
(3) The rubber composition for a tire according to the above (1) or (2), which is used for a competition wet tire.
(4) A pneumatic tire manufactured using the tire rubber composition described in any one of (1) to (3) above.
(5) The pneumatic tire according to (4), which is a competition wet tire.

  As described below, according to the present invention, a tire rubber composition excellent in wet grip performance, rigidity, and wear resistance when made into a tire, and air using such a tire rubber composition An inset tire can be provided.

It is a partial section schematic diagram of the tire showing an example of the embodiment of the pneumatic tire of the present invention.

  Below, the rubber composition for tires of this invention and the pneumatic tire using the rubber composition for tires of this invention are demonstrated.

[Rubber composition for tire]
The rubber composition for tires of the present invention (hereinafter also referred to as the composition of the present invention) includes a diene rubber (A) having a weight average molecular weight of 100,000 to 3,000,000, silica (B), Containing an aromatic modified terpene resin (C) having a softening point of 60 to 180 ° C. and a low molecular weight styrene-butadiene copolymer (D) having a weight average molecular weight of 2,000 to 20,000; The rubber (A) includes a conjugated diene rubber (A1).
Here, the conjugated diene rubber (A1) has three or more conjugated diene polymer chains (a1) obtained by a reaction between the conjugated diene polymer chain (a1) and the modifier (a2). 5 mass% or more of structures (a) formed by bonding via the modifier (a2) are included.
The conjugated diene polymer chain (a1) has an isoprene block containing 70% by mass or more of isoprene units at one end and an active end at the other end.
Moreover, styrene unit content of parts other than the said isoprene block in the said conjugated diene polymer chain (a1) is 35-45 mass%.
The modifier (a2) has an epoxy group and / or a hydrocarbyloxysilyl group, and the total number of the epoxy group and the hydrocarbyloxy group contained in the hydrocarbyloxysilyl group is 3 or more. It is an agent.
The average glass transition temperature of the diene rubber (A) is −35 ° C. or higher.
The content of the conjugated diene rubber (A1) is 30% by mass or more based on the content of the diene rubber (A), and the content of the silica (B) is the diene rubber. (A) It is 60-170 mass parts with respect to 100 mass parts, and content of the said aromatic modified terpene resin (C) is 10-50 mass with respect to 100 mass parts of said diene rubber (A). The content of the low molecular weight styrene-butadiene copolymer (D) is 5 to 100 parts by mass with respect to 100 parts by mass of the diene rubber (A).

  The composition of the present invention comprises a conjugated diene rubber (A1) containing a predetermined amount of a structure (a) described later, silica (B), an aromatic modified terpene resin (C), and a low molecular weight styrene-butadiene copolymer. Since the polymer (D) is used in combination, it is considered that the tire rubber composition exhibits excellent characteristics in terms of wet grip performance, rigidity and wear resistance when formed into a tire.

The reason is not clear, but it is presumed that it is as follows.
As will be described later, the structure (a) has an isoprene block, and the conjugated diene polymer chain (a1) having a styrene unit content in a portion other than the isoprene block has a specific functional group. It has a structure bonded through the modifying agent (a2).
Since the composition of the present invention uses a predetermined amount of the conjugated diene rubber (A1) containing the structure (a) and the low molecular weight styrene-butadiene copolymer (D), the conjugated diene rubber ( A three-dimensional network structure excellent in mechanical properties (rigidity, wear resistance, etc.) is formed by crosslinking of A1) and the low molecular weight styrene-butadiene copolymer (D), and isoprene in the three-dimensional network structure. A block and a specific functional group of the modifier (a2) interact with silica to improve the dispersibility of the silica, resulting in excellent wet grip performance, rigidity, durability and wear resistance it is conceivable that.
In particular, it is considered that the mechanical properties are improved by packing the styrene units by setting the content of the styrene units other than the isoprene block in the conjugated diene polymer chain (a1) within a specific range. This is because, in comparison with Comparative Example 4 described later in which the styrene unit content deviates from a specific range, all of the present examples in which the styrene unit content is in a specific range are excellent in rigidity and wear resistance. Also guessed.

  Hereinafter, each component contained in the composition of this invention is explained in full detail.

[Diene rubber (A)]
The diene rubber (A) contained in the composition of the present invention includes a conjugated diene rubber (A1) described later. The diene rubber (A) may contain other rubber components other than the conjugated diene rubber (A1), as will be described later.

  The diene rubber (A) has a weight average molecular weight of 100,000 to 3,000,000. That is, the weight average molecular weight of each rubber component (such as conjugated diene rubber (A1)) contained in the diene rubber (A) is 100,000 to 3,000,000. The weight average molecular weight of each rubber component is preferably 100,000 to 2,000,000, and more preferably 300,000 to 1,500,000. In addition, the weight average molecular weight (Mw) in this application shall be measured by the standard polystyrene conversion by the gel permeation chromatography (GPC) which uses tetrahydrofuran as a solvent.

The diene rubber (A) has an average glass transition temperature (hereinafter also referred to as average Tg) of −35 ° C. or higher. Since the diene rubber (A) has the above-mentioned specific average Tg, the tire using the composition of the present invention is excellent in the balance of wet grip performance and rigidity. The average Tg of the diene rubber (A) is preferably -30 to -10 ° C.
The average Tg of the diene rubber (A) is obtained by multiplying the Tg of each rubber component by the mass% of each rubber component. In addition, Tg of each rubber | gum was measured with the temperature increase rate of 20 degree-C / min using the differential scanning calorimeter (DSC), and was calculated by the midpoint method.

  In the conjugated diene rubber (A1), three or more conjugated diene polymer chains (a1) obtained by a reaction between a conjugated diene polymer chain (a1) described later and a modifier (a2) described later are modified. It contains 5% by mass or more of a structure (a) described later formed by bonding via an agent (a2).

<Conjugated Diene Polymer Chain (a1)>
The conjugated diene polymer chain (a1) used for forming the structure (a) contained in the conjugated diene rubber (A1) is a polymer chain comprising a conjugated diene monomer unit. There is no particular limitation as long as it has an isoprene block at one end and an active end (polymerization active end or living growth end) at the other end.

  The conjugated diene polymer chain (a1) is obtained by subjecting an isoprene or an isoprene mixture containing a predetermined amount of isoprene in an inert solvent to living polymerization using a polymerization initiator, thereby producing an active end (polymerization active end or Isoprene block having a living growth end), and then a monomer mixture comprising a butadiene monomer and a styrene monomer is coupled to the isoprene block having an active end, followed by living polymerization. be able to.

  The isoprene block is a homopolymer of isoprene or a copolymer of isoprene and another monomer (monomer), and is a polyisoprene having a content of isoprene units of 70% by mass or more. The content of isoprene units in the isoprene block is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass.

  As described above, the conjugated diene polymer chain (a1) has the isoprene block at one end. An isoprene block may be further included in the chain of the conjugated diene polymer chain (a1). It has an isoprene block at both ends, and an isoprene block at one end of them may have an active end, but it is preferable from the viewpoint of productivity to have an isoprene block only at the end that is not the active end. .

  The weight average molecular weight of the isoprene block is not particularly limited, but is preferably 500 to 25,000, more preferably 1,000 to 15,000, and particularly preferably 1,500 to 10,000, for the reason that the strength is more excellent. 000.

  The molecular weight distribution represented by the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the isoprene block is not particularly limited, but from the viewpoint of productivity, preferably 1.0 to 1. 5, More preferably, it is 1.0-1.4, Most preferably, it is 1.0-1.3.

  The other monomer that can be copolymerized with isoprene used for obtaining the isoprene block is not particularly limited as long as it is copolymerizable with isoprene. For example, 1,3-butadiene, styrene, α-methylstyrene Etc. can be used. Among these, styrene is preferable. In the isoprene block, the content of other monomer units is less than 30% by mass, preferably less than 20% by mass, more preferably less than 10% by mass, and monomers other than isoprene units. It is particularly preferred not to contain.

  As the inert solvent used for the polymerization of isoprene (or isoprene mixture), any solvent that is usually used in solution polymerization and does not inhibit the polymerization reaction can be used without particular limitation. Specific examples thereof include, for example, chain aliphatic hydrocarbons such as butane, pentane, hexane, heptane and 2-butene; alicyclic hydrocarbons such as cyclopentane, cyclohexane and cyclohexene; aromatics such as benzene, toluene and xylene. Group hydrocarbons; and the like. The amount of the inert solvent used is not particularly limited, but is usually an amount such that the concentration of all monomers (isoprene and other monomers) is 1 to 50% by mass, preferably 10 to 40% by mass. It is the quantity which becomes.

  The polymerization initiator for synthesizing the isoprene block is not particularly limited as long as it is capable of living polymerizing isoprene (or an isoprene mixture) to give a polymer chain having an active end. A polymerization initiator mainly comprising an alkali metal compound, an organic alkaline earth metal compound, a lanthanum series metal compound, or the like is preferably used. Specific examples of the organic alkali metal compound include, for example, organic monolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium, and stilbenelithium; dilithiomethane, 1,4-dilithiobutane Organic polyvalent lithium compounds such as 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, and 1,3,5-tris (lithiomethyl) benzene; organic sodium compounds such as sodium naphthalene; Organic potassium compounds such as potassium naphthalene; and the like. Examples of organic alkaline earth metal compounds include di-n-butylmagnesium, di-n-hexylmagnesium, diethoxycalcium, calcium distearate, di-t-butoxystrontium, diethoxybarium, diisopropoxybarium, and diethyl. Examples include mercaptobarium, di-t-butoxybarium, diphenoxybarium, diethylaminobarium, barium distearate, and diketylbarium. As a polymerization initiator having a lanthanum series metal compound as a main catalyst, a lanthanum series metal salt comprising a lanthanum series metal such as lanthanum, cerium, praseodymium, neodymium, samarium and gadolinium, a carboxylic acid, and a phosphorus-containing organic acid As a main catalyst, and a polymerization initiator comprising this and a co-catalyst such as an alkylaluminum compound, an organoaluminum hydride compound, and an organoaluminum halide compound. Among these polymerization initiators, it is preferable to use an organic monolithium compound and an organic polyvalent lithium compound, more preferably an organic monolithium compound, and particularly preferably n-butyllithium. In addition, the organic alkali metal compound is a secondary compound such as dibutylamine, dihexylamine, dibenzylamine, pyrrolidine, hexamethyleneimine, and heptamethyleneimine (preferably pyrrolidine, hexamethyleneimine, and heptamethyleneimine). You may make it react with an amine and use it as an organic alkali metal amide compound. These polymerization initiators can be used alone or in combination of two or more.

  The amount of the polymerization initiator used may be determined according to the target molecular weight, but is preferably 4 to 250 mmol, more preferably 30 to 200 mmol, and particularly preferably 40 to 100 mmol per 100 g of isoprene (or isoprene mixture). It is a range.

  When polymerizing isoprene (or isoprene mixture), the polymerization temperature is usually in the range of -80 to 150 ° C, preferably 0 to 100 ° C, more preferably 20 to 90 ° C.

  In order to adjust the vinyl bond content in the isoprene monomer unit in the isoprene block (hereinafter also simply referred to as “vinyl bond content in the isoprene monomer unit”), a polar compound is added to the inert organic solvent during the polymerization. Is preferably added. Examples of the polar compound include ether compounds such as dibutyl ether, tetrahydrofuran and 2,2-di (tetrahydrofuryl) propane; tertiary amines such as tetramethylethylenediamine; alkali metal alkoxides; phosphine compounds; Among these, ether compounds and tertiary amines are preferable, and among them, those capable of forming a chelate structure with the metal of the polymerization initiator are more preferable, and 2,2-di (tetrahydrofuryl) propane and tetramethylethylenediamine are particularly preferable. preferable. The amount of the polar compound used may be determined according to the target vinyl bond content, and is preferably adjusted in the range of 0.1 to 30 mol, more preferably 0.5 to 10 mol, relative to 1 mol of the polymerization initiator. do it. When the amount of the polar compound used is within this range, it is easy to adjust the vinyl bond content in the isoprene monomer unit, and problems due to deactivation of the polymerization initiator hardly occur.

  The vinyl bond content in the isoprene monomer unit is preferably from 21 to 85% by mass, more preferably from 50 to 80% by mass, and even more preferably from 70 to 80%, because of low rolling resistance and better wet grip performance. % By mass. The vinyl bond content in the isoprene monomer unit in the isoprene block refers to the unit of 1,2-vinyl bond and the unit of 3,4-vinyl bond in the isoprene monomer unit in the isoprene block. It is a total ratio (mass%).

The portion other than the isoprene block in the conjugated diene polymer chain (a1) is a copolymer chain of a styrene monomer and another monomer. Of these, a copolymer chain of a styrene monomer and a butadiene monomer is preferable.
Although it does not specifically limit as said styrene monomer, For example, styrene, (alpha) -methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethyl Mention may be made of styrene, 2,4-diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, dimethylaminomethylstyrene, dimethylaminoethylstyrene and the like. . Among these, styrene, α-methylstyrene, and 4-methylstyrene are preferable, and styrene is more preferable. These styrene monomers can be used alone or in combination of two or more.

  Further, the butadiene monomer is not particularly limited. For example, 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, 2- Examples include chloro-1,3-butadiene. Among these, 1,3-butadiene or isoprene is preferably used, and 1,3-butadiene is more preferably used. These butadiene monomers can be used alone or in combination of two or more.

  Examples of the monomer other than the butadiene monomer include aromatic vinyl monomers other than styrene monomers such as vinyl naphthalene; butadiene monomers such as 1,3-pentadiene and 1,3-hexadiene. Conjugated diene monomers other than monomers; α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids or acid anhydrides such as acrylic acid, methacrylic acid, and maleic anhydride; methyl methacrylate Unsaturated carboxylic acid esters such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene Non-conjugated dienes can be mentioned. The amount of the monomer other than the butadiene monomer used is 10% by mass or less in the total monomer used for obtaining a portion other than the isoprene block in the conjugated diene polymer chain (a1). Preferably, it is more preferably 5% by mass or less, and particularly preferably 4 to 0% by mass.

  The styrene unit content of the portion other than the isoprene block in the conjugated diene polymer chain (a1) is 35 to 45% by mass. Especially, it is preferable that it is 36 to 42 mass% from the reason which wet grip performance and rigidity are more excellent. When the styrene unit content is less than 35% by mass, rigidity and wear resistance are insufficient when a tire is formed. In addition, the styrene unit content in the portion other than the isoprene block in the conjugated diene polymer chain (a1) is the average of the ratio (mass%) of the styrene monomer unit to the portion other than the isoprene block in the tire rubber composition. Represents a value.

When the portion other than the isoprene block in the conjugated diene polymer chain (a1) has a butadiene monomer unit, the vinyl bond content in the butadiene monomer unit in the portion other than the isoprene block (hereinafter simply referred to as “butadiene unit amount”). The “vinyl bond content in the body unit” is also not particularly limited, but is preferably 30 to 70%. The vinyl bond content in the butadiene monomer unit in the portion other than the isoprene block is the ratio (%) of the unit of 1,2-vinyl bond in the butadiene monomer unit in the portion other than the isoprene block. is there. For example, when there are 10 butadiene monomer units in a portion other than the isoprene block, and among them, 6 butadiene monomer units are units of 1,2 vinyl bond, vinyl in the butadiene monomer unit The bond content is 60% (= 6 ÷ 10 × 100%).
In order to adjust the vinyl bond content in the butadiene monomer unit, a polar compound may be added to the inert organic solvent during the polymerization as in the case of adjusting the vinyl bond content in the isoprene unit in the isoprene block. preferable. However, at the time of synthesizing the isoprene block, if an inert organic solvent is added with a polar compound in an amount sufficient to adjust the vinyl bond content in the butadiene monomer unit in the portion other than the isoprene block, It is not necessary to newly add a polar compound. Specific examples of the polar compound used for adjusting the vinyl bond content in the butadiene monomer unit are the same as the polar compound used for the synthesis of the above-described isoprene block. The amount of the polar compound used may be determined according to the target vinyl bond content, and is preferably adjusted in the range of 0.01 to 100 mol, more preferably 0.1 to 30 mol with respect to 1 mol of the polymerization initiator. do it. When the amount of the polar compound used is within this range, it is easy to adjust the vinyl bond content in the butadiene monomer unit, and problems due to deactivation of the polymerization initiator hardly occur.

  The inert solvent used for polymerization of a portion other than the isoprene block in the conjugated diene polymer chain (a1) is the same as the inert solvent used for the synthesis of the above-described isoprene block.

  As the polymerization initiator used for the synthesis of a portion other than the isoprene block in the conjugated diene polymer chain (a1), the above-described isoprene block having an active end is used as it is. The amount of the polymerization initiator used may be determined according to the target molecular weight, but is usually 0.1 to 5 mmol, preferably 0.2 to 2 mmol, more preferably 0 per 100 g of the monomer (mixture). The range is from 3 to 1.5 mmol.

  In polymerizing a portion other than the isoprene block in the conjugated diene polymer chain (a1), the polymerization temperature is usually -80 to 150 ° C, preferably 0 to 100 ° C, more preferably 20 to 90 ° C. is there. As the polymerization mode, any mode such as batch mode or continuous mode can be adopted. Of these, the batch method is preferable because the randomness of the bond can be easily controlled.

  The bonding mode in the portion other than the isoprene block can be various bonding modes such as a block shape, a taper shape, or a random shape. Among these, a random shape is preferable. When the portion other than the isoprene block is a copolymer chain of a styrene monomer and a butadiene monomer, and the bonding mode between the styrene monomer and the butadiene monomer is random, In order to prevent the ratio of the styrene monomer to the total amount of the styrene monomer and the butadiene monomer from becoming too high, the butadiene monomer or the butadiene monomer and the styrene monomer are continuously or It is preferable to intermittently supply into the polymerization system for polymerization.

  The weight average molecular weight of the conjugated diene polymer chain (a1) is not particularly limited, but is preferably 1,000 to 2,000,000, more preferably 10,000 to 1,500,000, and 100,000 to 1 1,000,000 is particularly preferred. When the weight average molecular weight of the conjugated diene polymer chain (a1) is within the above range, the strength of the tire becomes better. The method for measuring the weight average molecular weight is as described above.

  The molecular weight distribution represented by the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the conjugated diene polymer chain (a1) is preferably 1.0 to 3.0, more preferably. Is 1.0 to 2.5, particularly preferably 1.0 to 2.2. When the molecular weight distribution value (Mw / Mn) is within the above range, the conjugated diene rubber (A1) can be easily produced. In addition, the measuring method of a number average molecular weight is the same as the weight average molecular weight mentioned above.

  As described above, the conjugated diene polymer chain (a1) forms an isoprene block having an active end by first living polymerizing isoprene (or an isoprene mixture) using an initiator in an inert solvent. Then, using this isoprene block as a new polymerization initiator, it can be obtained by living polymerizing monomers such as styrene monomer and butadiene monomer. At this time, an isoprene block may be added to a monomer solution such as styrene monomer or butadiene monomer, or a monomer such as styrene monomer or butadiene monomer may be added to the solution of isoprene block. However, it is preferable to add an isoprene block in a solution of a monomer such as a styrene monomer or a butadiene monomer. Further, when the polymerization conversion rate of monomers such as styrene monomer and butadiene monomer is usually 95% or more, a conjugated diene polymer is newly added by adding isoprene (or isoprene mixture). An isoprene block can also be formed on the active terminal side of the chain (a1). The amount of isoprene (or isoprene mixture) used is preferably 10 to 100 mol, more preferably 15 to 70 mol, and particularly preferably 20 to 35 mol with respect to 1 mol of the polymerization initiator used in the initial polymerization reaction.

<Modifier (a2)>
The conjugated diene rubber (A1) used in the present invention has an active terminal of the conjugated diene polymer chain (a1) obtained as described above, an epoxy group and / or a hydrocarbyloxysilyl group, and The epoxy group and the hydrocarbyloxy group (—OR: where R is a hydrocarbon group or aryl group) contained in the hydrocarbyloxysilyl group react with the modifier (a2) having a total number of 3 or more. 5 mass% or more of structure (a) mentioned later is included.

  In the present specification, the “modifier” is a compound having a functional group that reacts with the active end of the conjugated diene polymer chain (a1) in one molecule. However, the functional group to be contained is limited to those having an affinity for silica. In the present invention, the functional group is an epoxy group or a hydrocarbyloxy group contained in a hydrocarbyloxysilyl group.

  The modifier (a2) used to form the structure (a) contained in the conjugated diene rubber (A1) of the present invention has an epoxy group and / or a hydrocarbyloxysilyl group, If it is a modifier | denaturant whose total number with the hydrocarbyl oxy group contained in a hydrocarbyl oxysilyl group is 3 or more, it will not specifically limit. That is, as the modifier (a2), there are those having 3 or more epoxy groups in the molecule, and hydrocarbyloxy groups having hydrocarbyloxysilyl groups in the molecules and bonded to silicon atoms in the hydrocarbyloxysilyl groups. Those having 3 or more in the molecule can be used, and in addition, both the epoxy group and the hydrocarbyloxysilyl group are included in the molecule, and in one molecule, in the epoxy group and the hydrocarbyloxysilyl group Those having a total number of 3 or more of hydrocarbyloxy groups bonded to silicon atoms can also be used. In the case where the molecule has a hydrocarbyloxysilyl group and the hydrocarbyloxysilyl group has two or more hydrocarbyloxy groups bonded to a silicon atom, the silicon atom having one hydrocarbyloxy group Includes two or more, those having two or more hydrocarbyloxy groups on the same silicon atom, and combinations thereof. When an organic group other than the hydrocarbyloxy group is bonded to the silicon atom of the hydrocarbyloxysilyl group, the organic group is not particularly limited.

  In addition, when the conjugated diene polymer chain (a1) reacts with the modifier (a2) having an epoxy group, at least a part of the epoxy group in the modifier (a2) is ring-opened so that the epoxy group becomes It is considered that a bond is formed between the carbon atom of the ring-opened portion and the active end of the conjugated diene polymer chain (a1). Further, when the conjugated diene polymer chain (a1) reacts with the modifier (a2) having a hydrocarbyloxysilyl group, at least a part of the hydrocarbyloxysilyl group in the hydrocarbyloxysilyl group of the modifier (a2) is removed. By separating, it is considered that a bond between the silicon atom contained in the modifier (a2) and the active end of the conjugated diene polymer chain (a1) is formed.

  By using the modifier (a2) in which the total number of epoxy groups and hydrocarbyloxy groups contained in the hydrocarbyloxysilyl group is 3 or more, the conjugated diene polymer chain (a1) of 3 or more is converted into the modifier. A conjugated diene rubber (A1) having a structure (a) bonded through (a2) can be obtained. The upper limit of the total number is not particularly limited, but is preferably 20 or less, and more preferably 10 or less.

  Examples of the hydrocarbyloxysilyl group contained in the modifier (a2) include alkoxysilyl groups such as methoxysilyl group, ethoxysilyl group, propoxysilyl group, butoxysilyl group, and aryloxysilyl groups such as phenoxysilyl group. It is done. Among these, an alkoxysilyl group is preferable and an ethoxysilyl group is more preferable.

  Examples of the hydrocarbyloxy group contained in the hydrocarbyloxysilyl group contained in the modifier (a2) include alkoxy groups such as methoxy group, ethoxy group, propoxy group and butoxy group, and aryloxy groups such as phenoxy group. Can be mentioned. Among these, an alkoxy group is preferable and an ethoxy group is more preferable.

  The modifier (a2) is preferably a polyorganosiloxane for the reason that the low rolling resistance and the wet grip performance are more excellent.

  Preferred embodiments of the modifier (a2) include a polyorganosiloxane represented by the following formula (1), a polyorganosiloxane represented by the following formula (2), and a polyorganosiloxane represented by the following formula (3). Examples thereof include siloxane and hydrocarbyloxysilane represented by the following formula (4). Among these, a polyorganosiloxane represented by the following formula (1), a polyorganosiloxane represented by the following formula (2), and a polyorganosiloxane represented by the following formula (3) are preferable. The polyorganosiloxane represented by (1) is more preferable.

In said formula (1), R < ₁ > -R < ₈ > is a C1-C6 alkyl group or a C6-C12 aryl group, and these may mutually be same or different. In the above formula (1), X ₁ and X ₄ are each an alkoxy group having 1 to 5 carbon atoms, an aryloxy group having 6 to 14 carbon atoms, or a group having 4 to 12 carbon atoms containing an epoxy group, or carbon It is a C1-C6 alkyl group or a C6-C12 aryl group, and X < ₁ > and X < ₄ > may be the same or different. In the above formula (1), X ₂ is an alkoxy group having 1 to 5 carbon atoms, a group having 4 to 12 carbon atoms containing an aryl group or an epoxy group, having 6 to 14 carbon atoms. In the above formula (1), X ₃ is a group containing 2 to 20 alkylene glycol repeating units. In said formula (1), m is an integer of 3-200, n is an integer of 0-200, k is an integer of 0-200.

In said formula (2), R < ₉ > -R < ₁₆ > is a C1-C6 alkyl group or a C6-C12 aryl group, and these may mutually be same or different. In the above formula (2), X ₅ ~X ₈ is an alkoxy group having 1 to 5 carbon atoms, a group having 4 to 12 carbon atoms containing an aryl group or an epoxy group, having 6 to 14 carbon atoms, these May be the same or different.

In said formula (3), R < ₁₇ > -R < ₁₉ > is a C1-C6 alkyl group or a C6-C12 aryl group, and these may mutually be same or different. In the above formula (3), X ₉ ~X ₁₁ is an alkoxy group having 1 to 5 carbon atoms, a group having 4 to 12 carbon atoms containing an aryl group or an epoxy group, having 6 to 14 carbon atoms, these May be the same or different. In said formula (3), s is an integer of 1-18.

In the formula (4), R ₂₀ is an alkylene group having 1 to 12 carbon atoms. In the formula (4), R ₂₁ ~R ₂₉ is an alkyl group or an aryl group having 6 to 12 carbon atoms, 1 to 6 carbon atoms, which may be different from be the same as each other. In said formula (4), r is an integer of 1-10.

In the polyorganosiloxane represented by the above formula (1), examples of the alkyl group having 1 to 6 carbon atoms represented by R _{1 to} R ₈ , X ₁ and X ₄ include a methyl group, an ethyl group, and n- Examples include propyl group, isopropyl group, butyl group, pentyl group, hexyl group, and cyclohexyl group. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group and a methylphenyl group. Among these, a methyl group and an ethyl group are preferable from the viewpoint of production of the polyorganosiloxane itself.

In the polyorganosiloxane represented by the above formula (1), examples of the alkoxy group having 1 to 5 carbon atoms represented by X ₁ , X ₂ and X ₄ include a methoxy group, an ethoxy group, a propoxy group, A propoxy group, a butoxy group, etc. are mentioned. Of these, a methoxy group and an ethoxy group are preferable from the viewpoint of reactivity with the active terminal of the conjugated diene polymer chain (a1).

In the polyorganosiloxane represented by the above formula (1), examples of the aryloxy group having 6 to 14 carbon atoms represented by X ₁ , X ₂ and X ₄ include a phenoxy group and a tolyloxy group. It is done.

In the polyorganosiloxane represented by the above formula (1), the group having 4 to 12 carbon atoms containing an epoxy group represented by X ₁ , X ₂ , and X ₄ is represented by the following formula (5). Group.

The formula (5) in, Z ₁ is an alkylene group or an alkyl arylene group having 1 to 10 carbon atoms, Z ₂ is methylene group, a sulfur atom or an oxygen atom, 2 carbon atoms E is an epoxy group -10 hydrocarbyl groups (hydrocarbon groups). In the above formula (5), * represents a bonding position.

In the group represented by the formula (5) is preferably a Z ₂ is an oxygen atom, Z ₂ is an oxygen atom, and is more preferable E is a glycidyl group, Z ₁ is 3 carbon atoms Are particularly preferred, wherein Z ₂ is an oxygen atom and E is a glycidyl group.

In the polyorganosiloxane represented by the above formula (1), X ₁ and X ₄ are preferably a group having 4 to 12 carbon atoms or an alkyl group having 1 to 6 carbon atoms containing an epoxy group. X ₂ is preferably an epoxy group-containing group having 4 to 12 carbon atoms, X ₁ and X ₄ are alkyl groups having 1 to 6 carbon atoms, and X ₂ is an epoxy group. It is more preferable that it is a C4-C12 group containing group.

In the polyorganosiloxane represented by the above formula (1), the group containing a repeating unit of X ₃ , that is, an alkylene glycol of 2 to 20, is preferably a group represented by the following formula (6).

  In said formula (6), t is an integer of 2-20, P is a C2-C10 alkylene group or alkylarylene group, R is a hydrogen atom or a methyl group, Q is C1-C1. 10 alkoxy groups or aryloxy groups. In the above formula (6), * represents a bonding position. Among these, it is preferable that t is an integer of 2 to 8, P is an alkylene group having 3 carbon atoms, R is a hydrogen atom, and Q is a methoxy group.

  In the polyorganosiloxane represented by the above formula (1), m is preferably an integer of 20 to 150, more preferably 30 to 120, because the mechanical strength is more excellent.

  In the polyorganosiloxane represented by the above formula (1), n is preferably an integer of 0 to 150, more preferably an integer of 0 to 120. In the polyorganosiloxane represented by the above formula (1), k is preferably an integer of 0 to 150, more preferably an integer of 0 to 120.

  In the polyorganosiloxane represented by the above formula (1), the total number of m, n, and k is preferably 400 or less, more preferably 300 or less, and particularly preferably 250 or less. . When the total number of m, n, and k is 400 or less, the production of the polyorganosiloxane itself is facilitated, the viscosity is not excessively increased, and the handling is facilitated.

In the polyorganosiloxane represented by the above formula (2), specific examples and preferred embodiments of R _{9 to} R ₁₆ are the same as R _{1 to} R ₈ in the above formula (1). In the polyorganosiloxane represented by the above formula (2), specific examples and preferred embodiments of X _{5 to} X ₈ are the same as X ₂ in the above formula (1).

In the polyorganosiloxane represented by the above formula (3), specific examples and preferred embodiments of R _{17 to} R ₁₉ are the same as R _{1 to} R ₈ in the above formula (1). In the polyorganosiloxane represented by the above formula (3), specific examples and preferred embodiments of X _{9 to} X ₁₁ are the same as X ₂ in the above formula (1).

In the hydrocarbyloxysilane represented by the above formula (4), examples of the alkylene group having 1 to 12 carbon atoms represented by R ₂₀ include a methylene group, an ethylene group, and a propylene group. Among these, a propylene group is preferable.
In the hydrocarbyloxysilane represented by the above formula (4), specific examples and preferred embodiments of R _{21 to} R ₂₉ are the same as R _{1 to} R ₈ in the above formula (1).

  Specific examples of the hydrocarbyloxysilane represented by the above formula (4) include N, N-bis (trimethylsilyl) -3-aminopropyltrimethoxysilane and N, N-bis (trimethylsilyl) -3-aminopropyltriethoxy. Examples thereof include silane, N, N-bis (trimethylsilyl) aminoethyltrimethoxysilane, and N, N-bis (trimethylsilyl) aminoethyltriethoxysilane. Among these, it is preferable to use N, N-bis (trimethylsilyl) -3-aminopropyltrimethoxysilane and N, N-bis (trimethylsilyl) -3-aminopropyltriethoxysilane.

  Other examples of the modifier (a2) include tetraalkoxysilane compounds such as tetramethoxysilane; hexaalkoxysilane compounds such as bis (trimethoxysilyl) methane; alkylalkoxysilane compounds such as methyltriethoxysilane; vinyltrimethoxy Alkenylalkoxysilane compounds such as Silane; arylalkoxysilane compounds such as phenyltrimethoxysilane; halogenoalkoxysilane compounds such as triethoxychlorosilane; 3-glycidoxyethyltrimethoxysilane, 3-glycidoxybutylpropyltri Epoxy group-containing alkoxysilane compounds such as methoxysilane and bis (3-glycidoxypropyl) dimethoxysilane; sulfur-containing compounds such as bis (3- (triethoxysilyl) propyl) disulfide Coxisilane compounds; amino group-containing alkoxysilane compounds such as bis (3-trimethoxysilylpropyl) methylamine; isocyanate group-containing alkoxysilane compounds such as tris (3-trimethoxysilylpropyl) isocyanurate; tetraglycidyl-1,3- And epoxy group-containing compounds such as bisaminomethylcyclohexane.

  A modifier | denaturant (a2) may be used individually by 1 type, and can also be used in combination of 2 or more type.

  Although the usage-amount of modifier | denaturant (a2) is not specifically limited, The modifier in the modifier | denaturant (a2) which reacts with the active terminal of a conjugated diene type polymer chain (a1) with respect to the mole number of the polymerization initiator used for polymerization reaction. The ratio of the total number of moles of the epoxy group and the hydrocarbyloxy group contained in the hydrocarbyloxysilyl group is usually 0.1 to 5, and the mechanical strength is more excellent. Preferably there is.

  The conjugated diene polymer chain (a1) is a polymerization terminator other than the polymerization terminator and the modifier (a2), as long as the effect of the present invention is not inhibited before the above-described modifier (a2) is reacted. A coupling agent or the like may be added to the polymerization system to inactivate a part of the active end of the conjugated diene polymer chain (a1).

  Examples of the polymerization terminal modifier and coupling agent used at this time include N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, and N-methyl-ε-caprolactam. N-substituted cyclic amides; N-substituted cyclic ureas such as 1,3-dimethylethyleneurea and 1,3-diethyl-2-imidazolidinone; 4,4′-bis (dimethylamino) benzophenone, and N-substituted aminoketones such as 4,4′-bis (diethylamino) benzophenone; aromatic isocyanates such as diphenylmethane diisocyanate and 2,4-tolylene diisocyanate; N, N-dimethylaminopropyl methacrylamide and the like N, N-disubstituted aminoalkylmethacrylamides; 4-N, N-di N-substituted aminoaldehydes such as tilaminobenzaldehyde; N-substituted carbodiimides such as dicyclohexylcarbodiimide; Schiff bases such as N-ethylethylideneimine and N-methylbenzylideneimine; pyridyl group-containing vinyl compounds such as 4-vinylpyridine Tin tetrachloride, silicon tetrachloride, hexachlorodisilane, bis (trichlorosilyl) methane, 1,2-bis (trichlorosilyl) ethane, 1,3-bis (trichlorosilyl) propane, 1,4-bis (trichlorosilyl) And metal halide compounds such as butane, 1,5-bis (trichlorosilyl) pentane, and 1,6-bis (trichlorosilyl) hexane. Among these, it is preferable to use a metal halide compound as a coupling agent because the coupling efficiency is more excellent. A silicon halide compound having 5 or more silicon-halogen atom bonds in one molecule is used as a coupling agent. More preferably, 1,6-bis (trichlorosilyl) hexane is particularly preferably used.

  The amount of the coupling agent used is not particularly limited as long as the effect of the present invention is not impaired. For example, in the case of a halogenated silicon compound having 5 or more silicon-halogen atom bonds in one molecule, the amount used is as follows. The ratio of the number of moles of silicon-halogen atom bonds of the silicon halide compound to the number of moles of the polymerization initiator used in the polymerization reaction is 0.001 to 0.25 because the mechanical strength is superior. It is preferable that it is 0.01-0.2.

  The said coupling agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  When adding the modifier (a2) and the coupling agent to the solution containing the conjugated diene polymer chain (a1), they are dissolved in an inert solvent from the viewpoint of controlling the reaction well. It is preferable to add to the polymerization system. The solution concentration is preferably in the range of 1 to 50% by mass.

<Conjugated diene rubber (A1)>
The conjugated diene rubber (A1) contained in the composition of the present invention is a conjugated diene rubber obtained by reacting the conjugated diene polymer chain (a1) with the modifier (a2). Specifically, it contains 5% by mass or more of the structure (a) formed by bonding three or more conjugated diene polymer chains (a1) via the modifier (a2).

  The reaction between the conjugated diene polymer chain (a1) and the modifier (a2) can be performed, for example, by adding the modifier (a2) to a solution containing the conjugated diene polymer chain (a1). it can. The timing for adding the modifier (a2) and the coupling agent is not particularly limited, but the polymerization reaction in the conjugated diene polymer chain (a1) is not completed and the conjugated diene polymer chain (a1) is contained. The solution containing the monomer such as isoprene, more specifically, the solution containing the conjugated diene polymer chain (a1) is preferably 100 ppm or more, more preferably 300 to 50,000 ppm. It is desirable to add a modifier (a2), a coupling agent, and the like to this solution in a state where the monomer is contained. By adding a modifier (a2), a coupling agent, etc., the side reaction between the conjugated diene polymer chain (a1) and impurities contained in the polymerization system is suppressed, and the reaction is controlled well. Is possible.

  In obtaining conjugated diene rubber (A1), when two or more modifiers (a2) and coupling agents are used in combination, the order of adding them to the polymerization system is not particularly limited. Even when the modifying agent (a2) and a silicon halide compound as a coupling agent having 5 or more silicon-halogen atom bonds in one molecule are used in combination, the order of addition is not particularly limited. It is preferable to add the agent prior to the addition of the modifier (a2). By adding in this order, it becomes easy to obtain a highly branched conjugated diene rubber obtained via a coupling agent, and a tire obtained using the highly branched conjugated diene rubber has a steering stability. Better.

  As conditions for reacting the modifier (a2) and the coupling agent, the temperature is usually in the range of 0 to 100 ° C., preferably 30 to 90 ° C., and each reaction time is usually 1 to 1 ° C. The range is 120 minutes, preferably 2 to 60 minutes.

  After the modifier (a2) is reacted with the conjugated diene polymer chain (a1), it is preferable to deactivate the active terminal by adding alcohol such as methanol or water.

  After deactivating the active end of the conjugated diene polymer chain (a1), if desired, an anti-aging agent such as a phenol-based stabilizer, a phosphorus-based stabilizer, a sulfur-based stabilizer, a crumbizing agent, and a scale-inhibiting agent Are added to the polymerization solution, and then the polymerization solvent is separated from the polymerization solution by direct drying and steam stripping to recover the conjugated diene rubber (A1). Before separating the polymerization solvent from the polymerization solution, an extending oil may be mixed into the polymerization solution, and the conjugated diene rubber (A1) may be recovered as an oil-extended rubber.

  Examples of the extending oil used when recovering the conjugated diene rubber (A1) as an oil-extended rubber include paraffinic, aromatic and naphthenic petroleum softeners, plant softeners, and fatty acids. . When using a petroleum softener, the polycyclic aromatic content is preferably less than 3%. This content is measured by the method of IP346 (the testing method of THE INSTITUTE PETROLEUM, UK). When using the extender oil, the amount used is usually 5 to 100 parts by weight, preferably 10 to 60 parts by weight, more preferably 20 to 50 parts by weight with respect to 100 parts by weight of the conjugated diene rubber (A1). It is.

The conjugated diene rubber (A1) preferably contains 5% by mass or more of the structure (a) in which three or more conjugated diene polymer chains (a1) are bonded via a modifier (a2). Is contained in an amount of 5 to 40% by mass, particularly preferably 10 to 30% by mass.
The ratio of the structure (a) in which three or more conjugated diene polymer chains (a1) are bonded via the modifier (a2) to the total amount of the conjugated diene rubber (A1) finally obtained is expressed as “ It is expressed as “coupling ratio of 3 or more branches (mass%)” (hereinafter also simply referred to as coupling ratio). This can be measured by gel permeation chromatography (polystyrene conversion). From the chart obtained by gel permeation chromatography measurement, the area of the peak portion (s2) having a peak top molecular weight of 2.8 times or more of the peak top molecular weight indicated by the peak with the smallest molecular weight relative to the total elution area (s1). The ratio (s2 / s1) is a coupling rate of three or more branches. When a coupling agent other than the modifying agent (a2) is added before the modification, a sample is taken before the modifying agent (a2) is added, and the coupling agent is measured by measuring GPC. The proportion of the conjugated diene polymer chain bonded only to the monomer can be corrected.

  The conjugated diene rubber (A1) has a weight average molecular weight of 100,000 to 3,000,000 as described above. The range is preferably 100,000 to 2,000,000, more preferably 300,000 to 1,500,000. The method for measuring the weight average molecular weight is as described above.

  The molecular weight distribution represented by the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the conjugated diene rubber (A1) is not particularly limited, but preferably 1.1 to 3.0. More preferably, it is 1.2-2.5, Most preferably, it is 1.3-2.2. When the molecular weight distribution value (Mw / Mn) is 3.0 or less, the resulting tire has more excellent low rolling resistance. In addition, the measuring method of a number average molecular weight is the same as the weight average molecular weight mentioned above.

The Mooney viscosity (ML _{1 + 4} (100 ° C.)) of the conjugated diene rubber (A1) is not particularly limited, but is usually in the range of 20 to 100, preferably 30 to 90, and more preferably 40 to 85. When the conjugated diene rubber (A1) is an oil-extended rubber, the Mooney viscosity of the oil-extended rubber is preferably in the above range.

The content of the conjugated diene rubber (A1) is 30% by mass or more with respect to the content of the diene rubber (A). Especially, it is preferable that it is 50-100 mass% from the reason which wet grip performance and rigidity are more excellent.
When the content of the conjugated diene rubber (A1) is less than 30% by mass with respect to the content of the diene rubber (A), the wet grip performance becomes insufficient.

<Other rubber components>
As described above, the diene rubber (A) contained in the composition of the present invention may contain other rubber components other than the conjugated diene rubber (A1).
The other rubber components are not particularly limited. Specific examples thereof include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), and aromatic vinyl-conjugated diene copolymer rubber (for example, styrene). Examples thereof include butadiene rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), and chloroprene rubber (CR). The other rubber components may be used alone or in combination of two or more rubber components.
When the composition of this invention contains SBR, the suitable aspect of the styrene unit content of SBR is the same as parts other than the isoprene block in the conjugated diene polymer chain (a1) described above.

[Silica (B)]
The silica (B) contained in the composition of the present invention is not particularly limited, and any conventionally known silica that is blended in a rubber composition for uses such as tires can be used.
Examples of the silica (B) include wet silica, dry silica, fumed silica, and diatomaceous earth. As the silica (B), one type of silica may be used alone, or two or more types of silica may be used in combination.

The silica (B) preferably has a cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of 100 to 300 m ² / g for reasons of better wet grip performance and wear resistance when formed into a tire, and 140 to More preferably, it is 260 m ² / g.
Here, the CTAB adsorption specific surface area is a surrogate property of the surface area that silica can be used for adsorption with the silane coupling agent, and the amount of CTAB adsorption on the silica surface is JIS K6217-3: 2001 “Part 3: Specific surface area of It is a value measured according to “How to obtain—CTAB adsorption method”.

In the composition of the present invention, the content of the silica (B) is 60 to 170 parts by mass with respect to 100 parts by mass of the diene rubber (A), and wet grip performance and low rolling when used as a tire. From the reason that the resistance is more excellent and the mixing workability is excellent, it is preferably 65 to 145 parts by mass, and more preferably 70 to 140 parts by mass.
When the content of silica (B) is less than 60 parts by mass with respect to 100 parts by mass of the diene rubber (A), the wet grip performance becomes insufficient. On the other hand, when the content of silica (B) exceeds 170 parts by mass with respect to 100 parts by mass of the diene rubber (A), rigidity and wear resistance become insufficient.

[Aromatically modified terpene resin (C)]
The aromatic modified terpene resin (C) contained in the composition of the present invention is not particularly limited as long as it is an aromatic modified terpene resin having a softening point of 60 to 180 ° C.
Here, the softening point is a Vicat softening point measured according to JIS K7206: 1999.

In the composition of the present invention, the content of the aromatic modified terpene resin (C) is 10 to 50 parts by mass with respect to 100 parts by mass of the diene rubber (A), and the wet grip performance and rigidity are more. It is preferable that it is 10-40 mass parts from the reason which is excellent.
When the content of the aromatic terpene resin (C) exceeds 50 parts by mass with respect to 100 parts by mass of the diene rubber (A), rigidity and wear resistance are insufficient.

[Low molecular weight styrene-butadiene copolymer (D)]
The low molecular weight styrene-butadiene copolymer (D) contained in the composition of the present invention is not particularly limited as long as it is a low molecular weight styrene-butadiene copolymer having a weight average molecular weight of 2,000 to 20,000. The method for obtaining the weight average molecular weight is the same as that for the diene rubber (A) described above.
The weight average molecular weight of the low molecular weight styrene-butadiene copolymer (D) is preferably 3,000 to 10,000 because the wet grip performance, rigidity and wear resistance of the resulting tire are more excellent.
The styrene unit content of the low molecular weight styrene-butadiene copolymer (D) is preferably 20 to 40% by mass.
The vinyl bond content in the butadiene monomer unit of the low molecular weight styrene-butadiene copolymer (D) is preferably 40 to 70%.

The content of the low molecular weight styrene-butadiene copolymer (D) is 5 to 100 parts by mass with respect to 100 parts by mass of the diene rubber (A), and wet grip performance, rigidity and wear resistance of the resulting tire. From the reason that the properties are more excellent, it is preferably 10 to 90 parts by mass, and more preferably 40 to 70% by mass.
When the content of the low molecular weight styrene-butadiene copolymer (D) exceeds 100 parts by mass with respect to 100 parts by mass of the diene rubber (A), rigidity and wear resistance are insufficient.

[Optional ingredients]
If necessary, the composition of the present invention may further contain an additive within a range not impairing its effects and purposes.
Examples of the additives include silane coupling agents, fillers other than silica (B) (for example, carbon black), zinc oxide (zinc white), stearic acid, anti-aging agents, processing aids, aroma oils, and processes. Various additives generally used in tire rubber compositions such as oils, liquid polymers, terpene resins other than aromatic-modified terpene resins (C), thermosetting resins, vulcanizing agents, vulcanization accelerators, etc. It is done.

The composition of the present invention preferably contains carbon black from the viewpoint of processability.
The carbon black contained in the composition of the present invention is not particularly limited. For example, SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, Various grades such as FEF can be used.
The nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is preferably 100 to 400 m ² / g, preferably 110 to 320 m ² / g, because the wear resistance of the resulting tire is more excellent. More preferred.
Here, the nitrogen adsorption specific surface area (N ₂ SA) is the nitrogen adsorption amount on the carbon black surface according to JIS K6217-2: 2001 “Part 2: Determination of specific surface area—nitrogen adsorption method—single point method”. It is a measured value.

  The content of carbon black is not particularly limited, but is preferably 1 to 20 parts by mass with respect to 100 parts by mass of the diene rubber (A).

<Silane coupling agent>
The composition of the present invention preferably contains a silane coupling agent for the reason that the dispersibility of silica is more excellent.
Specific examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, Mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide And dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide. These may be used alone or in combination of two or more.

Moreover, as a suitable aspect of the said silane coupling agent, the mercapto type | system | group silane coupling agent which has a mercapto group and a hydrolysable group is mentioned, for example.
Examples of the hydrolyzable group include an alkoxy group, a phenoxy group, a carboxyl group, and an alkenyloxy group. Among these, an alkoxy group is preferable because the dispersibility of silica is more excellent. When the hydrolyzable group is an alkoxy group, the alkoxy group preferably has 1 to 16 carbon atoms, more preferably 1 to 4 carbon atoms. As a C1-C4 alkoxy group, a methoxy group, an ethoxy group, a propoxy group etc. are mentioned, for example.

Preferred embodiments of the mercapto silane coupling agent include a mercapto silane coupling agent having a polyether chain and / or a mercapto silane coupling agent having a polysiloxane structure (—Si—O—). Can be mentioned.
Here, the polyether chain is a side chain having two or more ether bonds, and specific examples thereof include, for example, a side chain having two or more structural units —R ^a —O—R ^b — in total. Can be mentioned. Here, in the structural unit, R ^a and R ^b are each independently a linear or branched alkylene group, a linear or branched alkenylene group, a linear or branched alkynylene group, Alternatively, it represents a substituted or unsubstituted arylene group. Of these, a linear alkylene group is preferable.

  As a suitable aspect of the mercapto type | system | group silane coupling agent which has the said polyether chain, the compound represented by a following formula (E2) is mentioned, for example.

In the formula (E2), R ²¹ represents an alkoxy group having 1 to 8 carbon atoms, among them, preferably an alkoxy group having 1 to 3 carbon atoms. Examples of the alkoxy group having 1 to 3 carbon atoms include a methoxy group and an ethoxy group. A plurality of R ²¹ when l is 2 may be the same or different.
In the formula (E2), R ²² represents a straight-chain polyether group having 4 to 30 carbon atoms. The polyether group is a group having two or more ether bonds, and specific examples thereof include a group having two or more structural units —R ^a —O—R ^b — in total. Definitions and preferred embodiments of R ^a and R ^b are the same as R ^a and R ^b as described above. When m is 2, the plurality of R ²² may be the same or different.
As a suitable aspect of a C4-C30 linear polyether group, group represented by a following formula (E5) is mentioned.

In the above formula (E5), R ⁵¹ represents a linear alkyl group, a linear alkenyl group, or a linear alkynyl group, and among them, a linear alkyl group is preferable. As the linear alkyl group, a linear alkyl group having 1 to 20 carbon atoms is preferable, and a linear alkyl group having 8 to 15 carbon atoms is more preferable. Specific examples of the linear alkyl group having 8 to 15 carbon atoms include octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group and the like, and tridecyl group is particularly preferable.
In the above formula (E5), R ⁵² represents a linear alkylene group, a linear alkenylene group, or a linear alkynylene group, and among them, a linear alkylene group is preferable. As said linear alkylene group, a C1-C2 linear alkylene group is preferable and an ethylene group is more preferable.
In said formula (E5), p represents the integer of 1-10 and it is preferable that it is 3-7.
In the above formula (E5), * indicates a bonding position.

In the formula (E2), R ²³ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.
In the formula (E2), R ²⁴ represents an alkylene group having 1 to 30 carbon atoms, among them preferably an alkylene group having 1 to 12 carbon atoms, more preferably an alkylene group having 1 to 5 carbon atoms. Specific examples of the alkylene group having 1 to 5 carbon atoms include a methylene group, an ethylene group, and a propylene group.
In said formula (E2), l represents the integer of 1-2 and it is preferable that it is 1. In said formula (E2), m represents the integer of 1-2 and it is preferable that it is 2. n represents an integer of 0 to 1, and is preferably 0. l, m, and n satisfy the relationship of l + m + n = 3.

  On the other hand, as a suitable aspect of the mercapto-based silane coupling agent having the polysiloxane structure, for example, a copolymer having a repeating unit represented by the following formula (E3) and a repeating unit represented by the following formula (E4) Things.

In the above formulas (E3) and (E4), R ³¹ and R ⁴¹ each independently represent an alkylene group having 1 to 5 carbon atoms, and specific examples thereof include a methylene group, an ethylene group, and a propylene group. It is done. Of these, a propylene group is preferred. A plurality of R ³¹ and R ⁴¹ may be the same or different.
In the above formulas (E3) and (E4), R ³² and R ⁴² are each independently a linear or branched alkylene group having 1 to 30 carbon atoms, or a linear or branched carbon group having 2 to 30 carbon atoms. The alkenylene group or the linear or branched alkynylene group having 2 to 30 carbon atoms is preferable, and those having 3 to 20 carbon atoms are preferable. When R ³² is a terminal, R ³² is a hydrogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, or a straight chain. It represents a chain or branched alkynyl group having 2 to 30 carbon atoms, and among them, those having 3 to 20 carbon atoms are preferable. If R ⁴² is terminated, the definition of R ^42, specific examples and preferred embodiments are the same as above R ^32. A plurality of R ³² and R ⁴² may be the same or different.
In the above formulas (E3) and (E4), R ³³ and R ⁴³ are each independently a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched group. A alkenyl group having 2 to 30 carbon atoms, a linear or branched alkynyl group having 2 to 30 carbon atoms, a linear or branched alkyl group having 1 to 30 carbon atoms, and a hydroxyl group or a carboxyl group at the terminal Or a linear or branched alkenyl group having 2 to 30 carbon atoms and having a hydroxyl group or a carboxyl group at the terminal. R ⁴³ is preferably a group having a hydroxyl group at the terminal. R ³² and R ³³ may form a ring with R ³² and R ³³ . R ⁴² and R ⁴³ may form a ring with R ⁴² and R ⁴³ . A plurality of R ³³ and R ⁴³ may be the same or different.
R ³⁴ represents an alkyl group having 1 to 13 carbon atoms, and among them, an alkyl group having 3 to 10 carbon atoms is preferable. Specific examples of the alkyl group having 3 to 10 carbon atoms include a hexyl group, a heptyl group, and an octyl group. A plurality of R ³⁴ may be the same or different.

  In the composition of the present invention, the content of the silane coupling agent is preferably 0.5 to 20% by mass with respect to the content of the silica (D) because the dispersibility of the silica is more excellent. 1 to 18% by mass, and more preferably 2 to 15% by mass.

[Method for producing rubber composition for tire]
The production method of the composition of the present invention is not particularly limited, and specific examples thereof include, for example, kneading the above-described components using a known method and apparatus (for example, a Banbury mixer, a kneader, a roll, etc.). The method etc. are mentioned.
The composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[Pneumatic tire]
The pneumatic tire of the present invention is a pneumatic tire manufactured using the composition of the present invention described above. Especially, it is preferable that it is a pneumatic tire manufactured using the composition of this invention for a tire tread.
FIG. 1 shows a schematic partial sectional view of a tire representing an example of an embodiment of the pneumatic tire of the present invention, but the pneumatic tire of the present invention is not limited to the embodiment shown in FIG.

In FIG. 1, reference numeral 1 represents a bead portion, reference numeral 2 represents a sidewall portion, and reference numeral 3 represents a tire tread portion.
Further, a carcass layer 4 in which fiber cords are embedded is mounted between the pair of left and right bead portions 1, and the end of the carcass layer 4 extends from the inside of the tire to the outside around the bead core 5 and the bead filler 6. Wrapped and rolled up.
In the tire tread 3, a belt layer 7 is disposed over the circumference of the tire on the outside of the carcass layer 4.
Moreover, in the bead part 1, the rim cushion 8 is arrange | positioned in the part which touches a rim | limb.

  The pneumatic tire of the present invention can be manufactured, for example, according to a conventionally known method. Moreover, as gas with which a tire is filled, inert gas, such as nitrogen, argon, helium other than the air which adjusted normal or oxygen partial pressure, can be used.

  Since the pneumatic tire of the present invention is excellent in wet grip performance, rigidity and wear resistance, it is particularly suitable for competitive wet tires.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.

<Synthesis Example 1: Conjugated Diene Rubber A11>
To a 100 ml ampule bottle purged with nitrogen, 28 g of cyclohexane and 8.6 mmol of tetramethylethylenediamine were added, and 6.1 mmol of n-butyllithium was further added. Then, 8.0 g of isoprene was slowly added and reacted in an ampoule bottle at 60 ° C. for 120 minutes to obtain an isoprene block (referred to as initiator 1). For this initiator 1, the weight average molecular weight, molecular weight distribution, and vinyl bond content in the isoprene monomer unit were measured. The measurement results are shown in Table 1. The measuring method is as described later.

  Next, in a nitrogen atmosphere, 4000 g of cyclohexane, 444.1 g of 1,3-butadiene, 260.9 g of styrene and 0.18 g of tetramethylethylenediamine were charged in an autoclave equipped with a stirrer. The polymerization was started. The maximum temperature during the polymerization reaction was 60 ° C. After confirming that the polymerization conversion was in the range of 95% to 100%, 0.08 mmol of 1,6-bis (trichlorosilyl) hexane was then added in the form of a 20% strength by weight cyclohexane solution, The reaction was allowed for 10 minutes. Furthermore, 0.027 mmol of polyorganosiloxane A represented by the following formula (11) was added in the form of a 20% by mass concentration of xylene solution and reacted for 30 minutes. Thereafter, as a polymerization terminator, an amount of methanol corresponding to twice the mole of n-butyllithium used was added to obtain a solution containing a conjugated diene rubber. To this solution, Irganox 1520L (manufactured by Ciba Specialty Chemicals) as an anti-aging agent was added in an amount of 0.15 parts by mass with respect to 100 parts by mass of the conjugated diene rubber, and then the solvent was removed by steam stripping. Then, it was vacuum dried at 60 ° C. for 24 hours to obtain a solid conjugated diene rubber. The obtained conjugated diene rubber is designated as conjugated diene rubber A11.

In the formula _{(11), X 1, X} 4, R 1 ~R 3 and R ₅ to R ₈ is a methyl group. In the above formula (11), m is 80 and k is 120. In the above formula (11), X ₂ is a group represented by the following formula (12).

  In the above formula (12), * represents a bonding position.

  For the conjugated diene rubber A11, the weight average molecular weight, molecular weight distribution, coupling rate, styrene unit content other than the isoprene block, vinyl bond content in the butadiene monomer unit other than the isoprene block, and Mooney The viscosity was measured. The measurement results are shown in Table 2. The measuring method is as described later.

(Weight average molecular weight, molecular weight distribution and coupling rate)
Regarding the weight average molecular weight, molecular weight distribution, and coupling rate (ratio (mass%) of the structure (a) to the conjugated diene rubber (A1)), a chart based on the molecular weight in terms of polystyrene was obtained by gel permeation chromatography. And based on the chart. The specific measurement conditions for gel permeation chromatography are as follows.

・ Measurement device: HLC-8020 (manufactured by Tosoh Corporation)
Column: GMH-HR-H (manufactured by Tosoh Corporation) connected in series Detector: Differential refractometer RI-8020 (manufactured by Tosoh Company)
-Elution night: Tetrahydrofuran-Column temperature: 40 ° C

  Here, the coupling rate is the ratio of the area (s2) of the peak portion having a peak top molecular weight of 2.8 times or more of the peak top molecular weight indicated by the smallest peak of molecular weight to the total elution area (s1) (s2 / s1).

(Styrene unit content and vinyl bond content)
The styrene unit content and the vinyl bond content were measured by ¹ H-NMR.

(Mooney viscosity)
The Mooney viscosity (ML _{1 + 4} (100 ° C.)) was measured according to JIS K6300-1: 2001.

<Synthesis Example 2: Conjugated Diene Rubber A12>
Initiator 1 was obtained according to the same procedure as in Synthesis Example 1.
Next, in a nitrogen atmosphere, 4000 g of cyclohexane, 446.2 g of 1,3-butadiene, 261.0 g of styrene, and 0.10 g of tetramethylethylenediamine were charged in an autoclave equipped with a stirrer. The polymerization was started. The maximum temperature during the polymerization reaction was 60 ° C. After confirming that the polymerization conversion was in the range of 95% to 100%, 0.08 mmol of 1,6-bis (trichlorosilyl) hexane was then added in the form of a 20% strength by weight cyclohexane solution, The reaction was allowed for 10 minutes. Furthermore, 0.027 mmol of polyorganosiloxane A represented by the above formula (11) was added in the form of a 20% by mass concentration xylene solution and reacted for 30 minutes. Thereafter, as a polymerization terminator, an amount of methanol corresponding to twice the mole of n-butyllithium used was added to obtain a solution containing the conjugated diene rubber 1. To this solution, 0.15 parts by mass of Irganox 1520L (manufactured by Ciba Specialty Chemicals) as an anti-aging agent was added to 100 parts by mass of the conjugated diene rubber 1, and then the solvent was removed by steam stripping. Then, it was vacuum-dried at 60 ° C. for 24 hours to obtain a solid conjugated diene rubber. The obtained conjugated diene rubber is designated as conjugated diene rubber A12.
For conjugated diene rubber A12, weight average molecular weight, molecular weight distribution, coupling rate, styrene unit content in portions other than isoprene blocks, vinyl bond content in butadiene monomer units in portions other than isoprene blocks, and Mooney The viscosity was measured. The measurement results are shown in Table 2. The measuring method is as described above.

<Synthesis Example 3: Conjugated Diene Rubber X>
Initiator 1 was obtained according to the same procedure as in Synthesis Example 1.
Next, in a nitrogen atmosphere, 4000 g of cyclohexane, 483.5 g of 1,3-butadiene, 211.5 g of styrene, and 0.18 g of tetramethylethylenediamine were charged in an autoclave equipped with a stirrer. The polymerization was started. The maximum temperature during the polymerization reaction was 60 ° C. After confirming that the polymerization conversion was in the range of 95% to 100%, 0.08 mmol of 1,6-bis (trichlorosilyl) hexane was then added in the form of a 20% strength by weight cyclohexane solution, The reaction was allowed for 10 minutes. Furthermore, 0.027 mmol of polyorganosiloxane A represented by the above formula (11) was added in the form of a 20% by mass concentration xylene solution and reacted for 30 minutes. Thereafter, as a polymerization terminator, an amount of methanol corresponding to twice the mole of n-butyllithium used was added to obtain a solution containing the conjugated diene rubber 1. To this solution, 0.15 parts by mass of Irganox 1520L (manufactured by Ciba Specialty Chemicals) as an anti-aging agent was added to 100 parts by mass of the conjugated diene rubber 1, and then the solvent was removed by steam stripping. Then, it was vacuum-dried at 60 ° C. for 24 hours to obtain a solid conjugated diene rubber. The obtained conjugated diene rubber is designated as conjugated diene rubber X.
For the conjugated diene rubber X, the weight average molecular weight, molecular weight distribution, coupling rate, styrene unit content other than the isoprene block, vinyl bond content in the butadiene monomer unit other than the isoprene block, and Mooney The viscosity was measured. The measurement results are shown in Table 2. The measuring method is as described above.

<Examples 1-3, Comparative Examples 1-10>
The components shown in Table 3 below were blended in the proportions (parts by mass) shown in Table 3 below.
Specifically, first, among the components shown in Table 3 below, components excluding sulfur and a vulcanization accelerator were mixed for 5 minutes using a 1.7 liter closed Banbury mixer, and reached 150 ± 5 ° C. Was released and cooled to room temperature to obtain a masterbatch. Furthermore, using the Banbury mixer, sulfur and a vulcanization accelerator were mixed into the obtained master batch to obtain a tire rubber composition.
In Table 3, for SBR1, SBR2, and SBR4, the upper value is the amount of oil-extended product (unit: parts by mass), and the lower value is the net amount (unit: parts by mass) of the rubber component.
In Table 3, “average Tg (° C.) of diene rubber” represents an average Tg (° C.) of diene rubber (weight average molecular weight: 100,000 to 3,000,000). The method for calculating the average Tg is as described above.

<Preparation of vulcanized rubber sheet for evaluation>
The prepared tire rubber composition (unvulcanized) was press-vulcanized at 160 ° C. for 20 minutes in a mold (15 cm × 15 cm × 0.2 cm) to produce a vulcanized rubber sheet.

<Tan δ (0 ° C.)>
About the vulcanized rubber sheet produced as described above, in accordance with JIS K6394: 2007, using a viscoelastic spectrometer (manufactured by Iwamoto Seisakusho Co., Ltd.), the tensile deformation strain rate is 10% ± 2%, the frequency is 20 Hz, and the temperature is 0 ° C. Tan δ (0 ° C.) was measured under the following conditions.
The results are shown in Table 3. The results were expressed as an index with tan δ (0 ° C.) of Comparative Example 1 as 100. The larger the index, the larger the tan δ (0 ° C.), and the better the wet grip performance when made into a tire.

<300% modulus>
About the vulcanized rubber sheet produced as described above, a JIS No. 3 dumbbell-shaped test piece (thickness 2 mm) is punched in accordance with JIS K6251: 2010, and a 300% modulus (300% at a temperature of 20 ° C. and a pulling speed of 500 mm / min. % Stress at the time of deformation).
The results are shown in Table 3. The results were expressed as an index with the 300% modulus of Comparative Example 1 as 100. The larger the index, the larger the 300% modulus, and the better the rigidity when made into a tire.

<Abrasion resistance>
The vulcanized rubber sheet produced as described above is subjected to wear loss under the conditions of a temperature of 20 ° C. and a slip rate of 50% using a Lambone abrasion tester (manufactured by Iwamoto Seisakusho) in accordance with JIS K6264-1, 2: 2005. It was measured.
The results are shown in Table 3. The results were expressed as an index according to the following equation, with the wear amount of Comparative Example 1 being 100. The larger the index, the smaller the amount of wear, and the better the wear resistance when made into a tire.
Abrasion resistance = (wear amount of Comparative Example 1 / wear amount of sample) × 100

Details of each component shown in Table 3 are as follows.
SBR1: E581 (oil-extended product (including 37.5 parts by mass of oil-extended oil with respect to 100 parts by mass of SBR. The net content of SBR in SBR is 72.7% by mass), styrene content: 37% by mass, vinyl bond (Amount: 42%, Tg: -27 ° C., weight average molecular weight: 1,260,000, manufactured by Asahi Kasei Corporation)
-SBR2: E680 (oil-extended product (including 37.5 parts by mass of oil-extended oil with respect to 100 parts by mass of SBR. The net content of SBR in SBR is 72.7% by mass), styrene content: 35% by mass, vinyl bond (Amount: 64%, Tg: −13 ° C., weight average molecular weight: 1,470,000, manufactured by Asahi Kasei Corporation)
Conjugated diene rubber A11: Conjugated diene rubber A11 produced as described above
Conjugated diene rubber A12: Conjugated diene rubber A12 produced as described above
Conjugated diene rubber X: Conjugated diene rubber X produced as described above
SBR3: Nipol NS616 (styrene content: 23 mass%, vinyl bond content: 70%, Tg: -23 ° C, weight average molecular weight: 510,000, manufactured by Nippon Zeon)
SBR4: Toughden 1834 (oil-extended product (including 37.5 parts by mass of oil-extended oil with respect to 100 parts by mass of SBR. The net content of SBR in SBR is 72.7% by mass), styrene content: 19% by mass, vinyl Bond amount: 10%, Tg: -71 ° C., weight average molecular weight: 700,000, manufactured by Asahi Kasei Corporation)
Silica: Zeosil 1165MP (CTAB specific surface area = 159 m ² / g, manufactured by Rhodia)
Carbon black: Seast 9 (N ₂ SA = 142 m ² / g, manufactured by Tokai Carbon Co., Ltd.)
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide, manufactured by Evonik Degussa)
Resin 1: YS resin TO-125 (aromatic modified terpene resin, softening point: 125 ° C., manufactured by Yasuhara Chemical Co., Ltd.)
Resin 2: YS Polystar T160 (aromatic modified terpene resin, softening point: 160 ° C., manufactured by Yasuhara Chemical Co., Ltd.)
・ Oil: Extract No. 4 S (made by Showa Shell Sekiyu KK)
Low molecular weight SB copolymer: RICON 100 (Tg: −15 ° C., weight average molecular weight: 4,500, styrene unit content: 25 mass%, vinyl bond content in butadiene monomer unit: 60%, Cray Valley (Made by company)
・ Zinc flower: 3 types of zinc oxide (manufactured by Shodo Chemical Industries)
・ Stearic acid: Bead stearic acid YR (manufactured by NOF Corporation)
・ Sulfur: Fine sulfur with Jinhua stamp oil (manufactured by Tsurumi Chemical Co., Ltd.)
・ Vulcanization accelerator 1: Noxeller D (Vulcanization accelerator DPG, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
・ Vulcanization accelerator 2: Noxeller CZ-G (vulcanization accelerator CBS, manufactured by Ouchi Shinsei Chemical Co., Ltd.)

  As can be seen from Table 3, a predetermined amount of conjugated diene rubber (A1), silica (B), aromatic terpene resin (C), and low molecular weight styrene-butadiene copolymer (D) are used in combination. All of the examples of the present application showed excellent wet grip performance, rigidity and wear resistance.

On the other hand, Comparative Example 1 not containing the conjugated diene rubber (A1) was insufficient in wet grip performance, rigidity and wear resistance.
Further, Comparative Example 3 in which the average glass transition temperature of the diene rubber was less than -35 ° C was insufficient in wet grip performance and rigidity.
Further, Comparative Example 4 in which the styrene unit content of the portion other than the isoprene block in the conjugated diene polymer chain was less than 35% by mass was insufficient in rigidity and wear resistance.
Moreover, the comparative example 7 which does not contain an aromatic terpene resin (C) had insufficient wet grip performance.
Moreover, the comparative example 10 which does not contain a low molecular weight styrene-butadiene copolymer (D) had insufficient wet grip performance.

Conjugated diene rubber (A1), silica (B), aromatic terpene resin (C), and low molecular weight styrene-butadiene copolymer (D) are used in combination. The comparative example 2 whose quantity is less than 30 mass% with respect to content of a diene rubber (A) had inadequate wet grip performance.
Similarly, although (A) to (D) are used together, Comparative Example 5 in which the content of silica (B) is less than 60 parts by mass with respect to 100 parts by mass of the diene rubber (A) has wet grip performance. It was insufficient.
Similarly, although (A) to (D) are used together, Comparative Example 6 in which the content of silica (B) exceeds 170 parts by mass with respect to 100 parts by mass of the diene rubber (A) is rigid and wear resistant. Was insufficient.
Similarly, (A) to (D) are used in combination, but the content of the aromatic terpene resin (C) exceeds 50 parts by mass with respect to 100 parts by mass of the diene rubber (A). Insufficient wear resistance.
Similarly, (A) to (D) are used in combination, but the content of the low molecular weight styrene-butadiene copolymer (D) exceeds 100 parts by mass with respect to 100 parts by mass of the diene rubber (A). Was insufficient in rigidity and wear resistance.

1 Bead part 2 Side wall part 3 Tire tread part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Rim cushion

Claims (5)

Diene rubber (A) having a weight average molecular weight of 100,000 to 3,000,000, silica (B), aromatic modified terpene resin (C) having a softening point of 60 to 180 ° C., and weight average molecular weight Low molecular weight styrene-butadiene copolymer (D) having a molecular weight of 2,000 to 20,000,
The diene rubber (A) includes a conjugated diene rubber (A1),
Three or more conjugated diene polymer chains (a1) obtained by reacting the conjugated diene rubber (A1) with a conjugated diene polymer chain (a1) and a modifier (a2) are the modifier. Containing 5 mass% or more of the structure (a) formed by bonding via (a2),
The conjugated diene polymer chain (a1) has an isoprene block containing 70% by mass or more of isoprene units at one end, and an active end at the other end.
The styrene unit content of the portion other than the isoprene block in the conjugated diene polymer chain (a1) is 35 to 45% by mass,
The modifier (a2) has an epoxy group and / or a hydrocarbyloxysilyl group, and the total number of the epoxy group and the hydrocarbyloxy group contained in the hydrocarbyloxysilyl group is 3 or more. Yes,
The average glass transition temperature of the diene rubber (A) is −35 ° C. or higher,
The content of the conjugated diene rubber (A1) is 30% by mass or more based on the content of the diene rubber (A).
The content of the silica (B) is 60 to 170 parts by mass with respect to 100 parts by mass of the diene rubber (A),
The content of the aromatic modified terpene resin (C) is 10 to 50 parts by mass with respect to 100 parts by mass of the diene rubber (A),
The rubber composition for tires, wherein the content of the low molecular weight styrene-butadiene copolymer (D) is 5 to 100 parts by mass with respect to 100 parts by mass of the diene rubber (A). Furthermore, it contains carbon black having a nitrogen adsorption specific surface area of 100 to 400 m ² / g,
The styrene unit content of the low molecular weight styrene-butadiene copolymer (D) is 20 to 40% by mass,
The rubber composition for tires according to claim 1, wherein a vinyl bond content in a butadiene monomer unit of the low molecular weight styrene-butadiene copolymer (D) is 40 to 70%.   The rubber composition for tires according to claim 1 or 2 used for a competition wet tire.   The pneumatic tire manufactured using the rubber composition for tires of any one of Claims 1-3.   The pneumatic tire according to claim 4 which is a competition wet tire.