JP2019108430A - Rubber composition and pneumatic tire - Google Patents

Abstract

To provide a rubber composition capable of providing a vulcanizate achieving excellent on-ice performance and excellent abrasion resistance by improving on-ice performance, and a pneumatic tire achieving excellent on-ice performance and excellent abrasion resistance by improving on-ice performance.SOLUTION: There is provided a rubber composition containing 100 pts.mass of a rubber component (A) containing a natural rubber of 45 to 75 mass%, and a conjugated diene polymer having bound styrene amount of a conjugated diene compound part of 25% or less of 25 to 55 mass%, 1 to 40 pts.mass of an unmodified conjugated diene polymer having polystyrene conversion weight average molecular weight measured by a gel permeation chromatography of 5,000 or more and less than 40,000, bound styrene amount of the conjugated diene compound part of less than 10%, and vinyl binding amount of the conjugated diene compound part and the bound styrene amount S satisfying a relationship of 25≤[S+(V/2)].SELECTED DRAWING: None

Description

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

  Conventionally, a studless tire having a soft tread rubber has been used as a tire for traveling safely on ice in addition to a normal road surface, and the performance of the tire on ice can be improved by softening the tread rubber. Are known. However, in general, a tire having a soft tread rubber has a problem that the wear resistance on a normal road surface is poor, and the on-ice performance and the wear resistance of the tire are in a trade-off relationship.

On the other hand, natural rubber, isoprene rubber, styrene, and the like can be added to the rubber composition in order to provide a rubber composition having an improved coefficient of friction on ice and excellent flexibility at low temperatures and excellent wet grip and ice grip properties. In a rubber composition comprising, as a rubber component, at least one diene polymer selected from the group consisting of butadiene rubber, butadiene rubber, and isobutylene / isoprene copolymer, the rubber composition comprises foamable cells in a rubber matrix. (A) polystyrene-converted weight average molecular weight is 0.2 × 10 ⁴ to 8 × 10 ⁴ , and (b) bound styrene content is 30% by weight or less based on 100 parts by weight of the rubber component, (C) Low molecular weight styrene-butadiene satisfying the relationship of S + (V / 2) <25, where S is a bound styrene amount and V is a vinyl binding amount. It is disclosed to contain 2 to 50 parts by weight of a copolymer (see, for example, Patent Document 1).

Unexamined-Japanese-Patent No. 9-194640 gazette

However, with the rubber composition of Patent Document 1, the balance between on-ice performance and abrasion resistance was insufficient.
The present invention provides a rubber composition which further improves the performance on ice and provides a vulcanized rubber having both excellent performance on ice and excellent abrasion resistance, and further improves the performance on ice, and the excellent performance on ice and excellent It aims at providing a pneumatic tire compatible with abrasion resistance, and it makes it a subject to solve the purpose.

<1> 100 parts by mass of a rubber component (A) containing 45 to 75% by mass of a natural rubber, and 25 to 55% by mass of a conjugated diene-based polymer having a bound styrene content of 25% or less of a conjugated diene compound portion;
The polystyrene conversion weight average molecular weight measured by gel permeation chromatography is 5,000 or more and less than 40,000, the bound styrene amount S of the conjugated diene compound portion is less than 10%, and the vinyl bound amount V of the conjugated diene compound portion and the bound styrene 1 to 40 parts by mass of a non-modified conjugated diene-based polymer (B) in which the amount S satisfies the relationship of 25 ≦ [S + (V / 2)],
Filler (C),
Is a rubber composition containing

<2> The rubber composition according to <1>, wherein a vinyl bond amount of a conjugated diene compound portion of the conjugated diene polymer (B) is 50 to 70%.
<3> The rubber composition according to <1> or <2>, wherein the conjugated diene polymer (B) is polybutadiene.
It is a rubber composition as described in any one of <1>-<3> which has a <4> blowing agent.
It is a rubber composition as described in any one of <1>-<4> which has a <5> hydrophilic short fiber.

It is the pneumatic tire which used the rubber composition as described in any one of <6> <1>-<5> for a tread part.

  According to the present invention, a rubber composition capable of obtaining a vulcanized rubber having improved on-ice performance and having both excellent on-ice performance and excellent abrasion resistance, and further improved on-ice performance and excellent on-ice performance It is possible to provide a pneumatic tire compatible with excellent wear resistance.

<Rubber composition>
The rubber composition of the present invention comprises 100 parts by mass of a rubber component (A) containing 45 to 75% by mass of a natural rubber and 25 to 55% by mass of a conjugated diene polymer having 25% or less bound styrene in a conjugated diene compound portion. And a weight-average molecular weight in terms of polystyrene as measured by gel permeation chromatography of 5,000 or more and less than 40,000, a bound styrene amount S of the conjugated diene compound portion is less than 10%, and a vinyl bound amount V of the conjugated diene compound portion The bound styrene amount S contains 1 to 40 parts by mass of the unmodified conjugated diene polymer (B) satisfying the relationship of 25 ≦ [S + (V / 2)], and the filler (C).
The conjugated diene polymer in which the bound styrene content of the conjugated diene compound portion is 25% or less may be hereinafter referred to as "conjugated diene polymer (a)".
The rubber composition of the present invention may contain, for example, a foaming agent, a hydrophilic short fiber and the like in addition to the rubber component (A), the conjugated diene polymer (B) and the filler (C).

As stated above, the tire ice performance and wear resistance are in a trade-off relationship.
The tire's tread (especially the tread) should be flexible to have the tire's braking performance on ice, making it difficult for the tire to slip on a frozen road surface, braking well, and running with grip. Is required. On the other hand, flexible tires are prone to wear. By improving the rigidity of the tire to improve the wear resistance of the tire, the flexibility of the tire is lost, so the tire with excellent wear resistance has reduced on-ice performance.
On the other hand, in the rubber composition of the present invention, since the vinyl bond amount V of the conjugated diene-based polymer and the amount S of bound styrene satisfy the relationship of 25 ≦ [S + (V / 2)], the storage elasticity of the rubber composition The rate, loss factor (tan δ) and fracture strength are highly balanced. Therefore, it is considered that a vulcanized rubber obtained by vulcanizing such a rubber composition and a tire having a tread portion obtained from the rubber composition can achieve both excellent on-ice performance and excellent abrasion resistance. .
Hereinafter, the rubber composition and the pneumatic tire of the present invention will be described in detail.

[Rubber component (A)]
The rubber composition of the present invention comprises 45 to 75% by mass of a natural rubber, and 25 to 55 parts by mass of a conjugated diene polymer [conjugated diene polymer (a)] having a bound styrene content of 25% or less in a conjugated diene compound portion. % Contains a rubber component (A).
In addition, the natural rubber and the conjugated diene polymer (a) contained in the rubber component (A) are high molecular weight compounds (polymer compounds) having a polystyrene equivalent weight average molecular weight measured by gel permeation chromatography exceeding 200,000. is there.

When the content of the natural rubber in the rubber component (A) is less than 45% by mass, the rubber becomes too soft and wear resistance decreases, and when it exceeds 75% by mass, the rubber becomes too hard and performance on ice decreases . From such a viewpoint, the content of the natural rubber in the rubber component (A) is preferably 48 to 70% by mass, and more preferably 50 to 65% by mass.
When the content of the conjugated diene polymer (a) in the rubber component (A) is less than 25% by mass, the rubber becomes too hard and the performance on ice decreases, and when it exceeds 55% by mass, the rubber becomes soft. Too much and wear resistance is reduced. From such a viewpoint, the content of the conjugated diene polymer (a) in the rubber component (A) is preferably 30 to 52% by mass, and more preferably 35 to 50% by mass.

(Conjugated diene-based polymer in which the bound styrene content of the conjugated diene compound portion is 25% or less)
The conjugated diene polymer [conjugated diene polymer (a)] in which the bound styrene content of the conjugated diene compound portion is 25% or less may be a copolymer or a homopolymer. Moreover, a modified conjugated diene polymer may be used, or an unmodified conjugated diene polymer may be used.

The conjugated diene polymer (a) has an amount of bound styrene (proportion of styrene units contained in the polymer) of 25% or less regardless of whether it is a modified polymer or a non-modified polymer. If the bound styrene content of the conjugated diene compound portion exceeds 25%, the rigidity of the rubber composition becomes excessive and the performance on ice can not be improved.
The bound styrene content of the conjugated diene polymer (a) is preferably 15% or less, more preferably 5% or less, and still more preferably 0% from the viewpoint of further improving the performance on ice. .

The bound styrene amount of the conjugated diene compound portion of the conjugated diene polymer (a) can be adjusted by the amount of the monomer used for polymerization, the degree of polymerization, and the like. In addition, the bound styrene content of the conjugated diene compound portion of the conjugated diene polymer (a) can be determined by the infrared method (morelo method).
In addition, the amount of bound styrene and the amount of vinyl bond of the polymer may be referred to as the microstructure of the polymer.

The conjugated diene polymer constituting the conjugated diene polymer (a) is derived from conjugated diene compounds such as 1,3-butadiene, 1,3-pentadiene, 2,3-dimethylbutadiene, 1,3-hexadiene and the like The polymer is not particularly limited as long as it has a unit, and examples thereof include styrene-butadiene copolymer rubber (SBR) and polybutadiene rubber (BR).
Among them, polybutadiene rubber (BR) is preferable.

  The conjugated diene polymer (a) preferably has a butadiene skeleton. When the conjugated diene polymer (a) has a butadiene skeleton, the rubber composition becomes soft, and when the rubber composition is used for the tread, the ground contact area of the tread becomes large, and the performance on ice is further improved. Here, as the conjugated diene polymer (a) having a butadiene skeleton, polybutadiene rubber (BR), styrene-butadiene copolymer rubber (SBR) and the like can be mentioned, and from the viewpoint of performance on ice, polybutadiene rubber (BR) Is particularly preferred.

  When the terminal of the conjugated diene polymer is modified with a silane compound, the modified conjugated diene polymer has a large interaction with the silica, and a conjugated diene polymer (a) phase containing the modified conjugated diene polymer In addition, more silica is distributed to soften the conjugated diene polymer (a) phase while imparting micro unevenness to the conjugated diene polymer (a) phase. Therefore, when the rubber composition is used for the tread of a tire, the contact area of the tread becomes large, and the on-ice performance of the tire can be improved.

  As a modified conjugated diene polymer, a polymer or copolymer of the conjugated diene compound obtained using a conjugated diene compound as a monomer, or a conjugated diene compound and an aromatic vinyl compound as a monomer Copolymers of the conjugated diene compound and the aromatic vinyl compound obtained by using it can be used, and those obtained by modifying the molecular terminal and / or main chain of these (co) polymers are used It can also be done. Specifically, as known modified conjugated diene-based polymers in which the molecular terminal is modified, WO 2003/029299, WO 2003/046020, JP 2004-513987 A, JP-A-11-29603 The modified diene polymers disclosed in JP-A-2003-113202 and JP-B-6-29338 can be exemplified, and as a known modified diene-based polymer in which the main chain has been modified, JP-A-2003-147202 is available. Examples of modified diene polymers disclosed in JP-A-534426 and JP-A-2002-201310 can be given.

The modified conjugated diene-based polymer in which the molecular end is modified is, for example, according to the method described in WO 2003/046020 and JP-A 2007-217562, at the end of the conjugated diene-based polymer having an active end. It can be produced by reacting various modifiers.
In a preferred embodiment, the modified conjugated diene-based polymer in which the molecular terminal is modified has a cis-1,4 bond content according to the method described in WO 2003/046020 and JP 2007-217562 A. Is reacted with a silane compound (for example, a hydrocarbyloxysilane compound) at the end of a conjugated diene polymer having an active end of 75% or more, and then reacted with a carboxylic acid partial ester of a polyhydric alcohol to perform stabilization Can be manufactured by

[Conjugated diene-based polymer (B)]
The rubber composition of the present invention has a polystyrene equivalent weight average molecular weight measured by gel permeation chromatography of 5,000 or more and less than 40,000, a bound styrene amount S of a conjugated diene compound portion is less than 10%, and a conjugated diene compound portion The unmodified conjugated diene polymer (B) containing the vinyl bond amount V and the bonded styrene amount S satisfying the relationship of 25 ≦ [S + (V / 2)] is contained. Further, the content of the conjugated diene-based polymer (B) in the rubber composition of the present invention is an amount to be 1 to 40 parts by mass with respect to 100 parts by mass of the rubber component (A).
When the vinyl bond amount V of the conjugated diene polymer and the amount S of the bonded styrene satisfy the relationship of 25 ≦ [S + (V / 2)], the balance of the storage elastic modulus, the loss coefficient (tan δ), and the breaking strength is An extremely high rubber composition is obtained.
“S + (V / 2)” is preferably 40 or less, more preferably 35 or less. "S + (V / 2)" is controlled by adjusting the amount of styrene / butadiene monomer, and adjusting the type, addition amount, etc. of randomizers such as tetrahydrofuran (THF), ditetrahydrofurylpropane, tertiary amine, etc. be able to.

  By concentrating the conjugated diene polymer (B), which easily contributes to the flexibility of the rubber composition, in the natural rubber phase, the performance on ice can be improved, and from such a viewpoint, the conjugated diene polymer (B) The vinyl bond amount V of the conjugated diene compound portion is preferably 50% or more. Further, from the viewpoint of suppressing the increase in hardness of the rubber, the vinyl bond amount V of the conjugated diene compound portion of the conjugated diene polymer (B) is preferably 75% or less, more preferably 70% or less, and 65 It is further more preferable that the content is% or less.

The conjugated diene polymer (B), which is 1 to 40 parts by mass with respect to 100 parts by mass of the rubber component (A), is distributively distributed in the natural rubber phase to provide flexibility to the rubber composition, and from the rubber composition It is easy to improve the on-ice performance of a tire provided with the obtained vulcanized rubber and tread portion.
In addition, when the amount of the conjugated diene-based polymer (B) is less than 1 part by mass with respect to 100 parts by mass of the rubber component (A), the rubber composition can not be provided with flexibility, and when it exceeds 40 parts by mass The rigidity of the rubber composition is impaired, and the wear resistance of the tire provided with the vulcanized rubber and the tread portion obtained from the rubber composition is reduced.
From the viewpoint of further improving the on-ice performance of a tire provided with a vulcanized rubber and a tread portion obtained from the rubber composition and achieving both excellent on-ice performance and excellent abrasion resistance, conjugation to 100 parts by mass of the rubber component (A) The amount of the diene polymer (B) is preferably 5 to 35 parts by mass, more preferably 10 to 30 parts by mass, and still more preferably 15 to 25 parts by mass.

The conjugated diene polymer (B) has a low molecular weight so as not to form a crosslinked structure with the rubber component (A) even when the rubber composition is vulcanized, and specifically, it is measured by gel permeation chromatography The polystyrene equivalent weight average molecular weight (hereinafter, may be simply referred to as weight average molecular weight) is 5,000 or more and less than 40,000.
If the weight average molecular weight of the conjugated diene polymer (B) is less than 5,000, the tread portion of the vulcanized rubber and tire obtained from the rubber composition may be excessively softened and the abrasion resistance may be impaired. . When the weight-average molecular weight of the conjugated diene-based polymer (B) is 40,000 or more, the flexibility is lost and the on-ice performance of the tire provided with the vulcanized rubber and the tread portion obtained from the on-ice rubber composition is impaired. there is a possibility.
From the viewpoint of further improving the on-ice performance of a tire provided with a vulcanized rubber and a tread portion obtained from a rubber composition and achieving both excellent on-ice performance and excellent abrasion resistance, the weight of the conjugated diene polymer (B) The average molecular weight is preferably 6,000 to 30,000, more preferably 7,000 to 27,500, and still more preferably 8,000 to 26,000.

The conjugated diene polymer (B) has a bound styrene content of less than 10% in the conjugated diene compound portion. If the bound styrene content of the conjugated diene compound portion is 10% or more, the flexibility of the rubber composition is lost, and the on-ice performance of the tire provided with the vulcanized rubber and the tread portion obtained from the on-ice rubber composition is impaired. there is a possibility,
The conjugated diene polymer (B) preferably has a bound styrene content of 5% or less, more preferably 3% or less, and still more preferably 0%.

  In addition, the conjugated diene polymer (B) is a non-modified polymer, so it is difficult to have an interaction with the filler (C) and suppresses the inclusion of the filler (C) in the natural rubber phase. be able to.

The conjugated diene-based polymer (B) is not particularly limited as long as it has a specific weight average molecular weight, a bound styrene amount of a conjugated diene compound portion less than a certain value, and a specific vinyl bond amount. Or homopolymers of an aromatic vinyl compound and a conjugated diene compound. Here, as the conjugated diene compound as a monomer, 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene And the like, and among these, 1,3-butadiene and isoprene are preferable. On the other hand, examples of the aromatic vinyl compound as the monomer include styrene, p-methylstyrene, m-methylstyrene, p-tert-butylstyrene, α-methylstyrene, chloromethylstyrene, vinyl toluene and the like.
As the conjugated diene polymer (B), either or both of polybutadiene and polyisoprene are preferable, and polybutadiene is more preferable. These monomers may be used alone or in combination of two or more.

  When the conjugated diene polymer (B) is an aromatic vinyl compound-conjugated diene compound copolymer, it is preferable that the bonding amount of the aromatic vinyl compound is less than 5% by mass. When the amount of the aromatic vinyl compound bonded is less than 5% by mass, the hardness of the rubber is increased, and the performance on ice can be suppressed from being deteriorated.

The method for producing the conjugated diene polymer (B) is not particularly limited. For example, the conjugated diene compound which is a monomer alone or in a hydrocarbon solvent inert to the polymerization reaction is used. It can be obtained by polymerizing a mixture of an aromatic vinyl compound and a conjugated diene compound.
As a polymerization initiator used for the synthesis | combination of a conjugated diene type polymer (B), a lithium compound is preferable and n-butyl thylium is still more preferable. When a lithium compound is used as the polymerization initiator, the aromatic vinyl compound and the conjugated diene compound are polymerized by anionic polymerization.

The method for producing the conjugated diene polymer (B) using the polymerization initiator is not particularly limited as described above, and, for example, the monomer is polymerized in a hydrocarbon solvent inert to the polymerization reaction. Thus, the conjugated diene polymer (B) can be produced.
Here, as a hydrocarbon solvent inert to the polymerization reaction, propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene, trans-2-butene, cis -2-butene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene and the like. These may be used alone or in combination of two or more.

The polymerization reaction may be carried out in the presence of a randomizer.
The randomizer can control the microstructure of the conjugated diene compound portion of the (co) polymer, and more specifically, control the vinyl bond amount of the conjugated diene compound portion of the (co) polymer, or It has an action such as randomizing the conjugated diene compound unit and the aromatic vinyl compound unit in the polymer.
As randomizers, dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, ditetrahydrofurylpropane, triethylamine, pyridine, N-methylmorpholine, N, N, N ', N'-tetramethylethylenediamine, 1, 2-dipiperidinoethane, potassium-t-amylate, potassium-t-butoxide, sodium-t-amylate and the like. The use amount of these randomizers is preferably in the range of 0.1 to 100 molar equivalents per mole of the polymerization initiator.

  The anionic polymerization is preferably carried out by solution polymerization, and the concentration of the monomer in the polymerization reaction solution is preferably in the range of 5 to 50% by mass, and more preferably in the range of 10 to 30% by mass. When the conjugated diene compound and the aromatic vinyl compound are used in combination, the content of the aromatic vinyl compound in the monomer mixture may be appropriately selected according to the amount of the aromatic vinyl compound of the target copolymer. it can. Further, the polymerization type is not particularly limited, and may be a batch system or a continuous system.

  The range of 0-150 degreeC is preferable, and, as for the polymerization temperature of anionic polymerization, the range of 20-130 degreeC is still more preferable. Also, although the polymerization can be carried out under the generation pressure, it is usually preferred to carry out under a pressure sufficient to substantially keep the monomers used in the liquid phase. Here, when the polymerization reaction is carried out under a pressure higher than the generation pressure, it is preferable to pressurize the reaction system with an inert gas. Moreover, it is preferable to use what removed reaction inhibiting substances, such as water, oxygen, a carbon dioxide, a protic compound, beforehand as raw materials, such as a monomer used for superposition | polymerization, a polymerization initiator, and a solvent.

  The weight average molecular weight of the conjugated diene polymer (B), the amount of bound styrene in the conjugated diene compound portion, and the amount of vinyl bond in the conjugated diene compound portion can be adjusted by the amount of monomers used for polymerization, the degree of polymerization, etc. . Further, the bound styrene amount of the conjugated diene compound portion of the conjugated diene polymer (B) and the vinyl bond amount of the conjugated diene compound portion (sometimes referred to as the microstructure of the conjugated diene polymer (B)) are infrared rays. It can be determined by the law (Morero law).

[Filler (C)]
The rubber composition of the present invention contains a filler (C).
The filler (C) is preferably a reinforcing filler that easily imparts rigidity to the rubber composition, and examples thereof include inorganic fillers such as silica, clay, talc, calcium carbonate and aluminum hydroxide, and carbon black Etc. can be mentioned. The type of the filler (C) is not particularly limited, and any filler can be selected from those conventionally used as a filler for rubber, and it may contain carbon black and / or silica. Preferably, both are more preferably included.
When using an inorganic filler such as silica, a silane coupling agent may be used in combination.

(silica)
The rubber composition of the present invention preferably contains silica.
The silica preferably has a CTAB (cetyltrimethylammonium bromide) specific surface area of 50 m ² / g or more, more preferably 90 m ² g or more, and preferably 350 m ² / g or less, more preferably 300 m ² / g or less. is there. When the CTAB specific surface area of silica is 50 m ² / g or more, the wear resistance is further improved, and when the CTAB specific surface area of silica is 350 m ² / g or less, the rolling resistance decreases.
The silica is not particularly limited, and examples thereof include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate and the like, and among these, wet silica is preferable. These silicas may be used alone or in a combination of two or more.

  The content of silica in the rubber composition of the present invention is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, still more preferably 30 parts by mass or more based on 100 parts by mass of the total of the rubber component (A). And preferably 60 parts by mass or less, more preferably 50 parts by mass or less. The performance on ice can be further improved by setting the content of silica to 20 parts by mass or more with respect to 100 parts by mass in total of the rubber component (A). Moreover, the workability of a rubber composition can be made favorable by making content of a silica 60 mass parts or less with respect to a total of 100 mass parts of a rubber component (A).

(Carbon black)
The rubber composition of the present invention preferably contains carbon black.
Carbon black reinforces the polymer phase formed from the rubber component (A) to improve abrasion resistance.
The carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF grade carbon black. These carbon blacks may be used alone or in combination of two or more.

  The content of carbon black in the rubber composition of the present invention is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 30 parts by mass with respect to 100 parts by mass in total of the rubber component (A). It is the above, and preferably 60 parts by mass or less, more preferably 50 parts by mass or less. The abrasion resistance can be further improved by setting the content of carbon black to 20 parts by mass or more with respect to 100 parts by mass in total of the rubber component (A). Moreover, the workability of a rubber composition can be made favorable by making content of carbon black into 60 mass parts or less with respect to a total of 100 mass parts of rubber components (A).

  In the rubber composition of the present invention, the content of silica is preferably 20 parts by mass or more and the content of carbon black is preferably 20 parts by mass or more with respect to a total of 100 parts by mass of the rubber component (A). In this case, when the rubber composition is applied to a tire, the performance on ice is further improved by containing 20 parts by mass or more of silica, and the abrasion resistance is further improved by containing 20 parts by mass or more of carbon black. The tire ice performance and abrasion resistance can be highly improved.

  The total content of silica and carbon black is preferably 50 parts by mass or more, and more preferably 60 parts by mass or more, with respect to 100 parts by mass in total of the rubber component (A). When the rubber composition containing 50 parts by mass or more of silica and carbon black in total with respect to 100 parts by mass of the rubber component (A) is used for the tread of the tire, the on-ice performance and wear resistance of the tire are further improved. .

(Silane coupling agent)
The rubber composition of the present invention preferably further contains a silane coupling agent.
As a silane coupling agent, the silane coupling agent normally used in the rubber industry can be used.

[Blowing agent]
The rubber composition of the present invention preferably further contains a foaming agent.
When the rubber composition contains a foaming agent, when the rubber composition is vulcanized to produce a vulcanized rubber, bubbles derived from the foaming agent are formed in the vulcanized rubber. Therefore, when a tire is manufactured using a rubber composition containing a foaming agent for a tread, the tire's performance on ice can be further improved by the drainage effect of air bubbles in the tread.

Specific examples of the foaming agent include azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), dinitrosopentastyrenetetramine, benzenesulfonylhydrazide derivatives, p, p'-oxybisbenzenesulfonylhydrazide ( OBSH), ammonium bicarbonate which generates carbon dioxide, sodium bicarbonate, ammonium carbonate, nitrososulfonylazo compound which generates nitrogen, N, N'-dimethyl-N, N'-dinitrosophthalamide, toluenesulfonyl hydrazide, p -Toluenesulfonyl semicarbazide, p, p'- oxybis benzene sulfonyl semicarbazide etc. are mentioned. Among them, azodicarbonamide (ADCA) and dinitrosopentamethylenetetramine (DPT) are preferable, and azodicarbonamide (ADCA) is more preferable, from the viewpoint of production processability. These foaming agents may be used alone or in combination of two or more.
The content of the foaming agent in the rubber composition is not particularly limited, but is preferably in the range of 0.1 to 30 parts by mass, and in the range of 1 to 20 parts by mass with respect to 100 parts by mass of the rubber component. Is more preferred.

  When a foaming agent is used to foam the vulcanized rubber, it is preferable to use urea, zinc stearate, zinc benzenesulfinate, zinc white or the like in combination as a foaming aid. These may be used singly or in combination of two or more. By using the foaming aid in combination, the foaming reaction can be promoted to increase the degree of completion of the reaction, and unnecessary deterioration can be suppressed with time.

In the vulcanized rubber obtained after vulcanizing the rubber composition containing a foaming agent, the foaming ratio is usually 1 to 50%, preferably 5 to 40%. When a foaming agent is compounded, if the foaming ratio is too large, the voids on the rubber surface will also be large, and there is a possibility that a sufficient ground contact area can not be secured. Since the amount of air bubbles can be held appropriately while securing the formation of air bubbles, durability is hardly impaired. Here, the foaming ratio of the vulcanized rubber means an average foaming ratio Vs, and specifically means a value calculated by the following equation (1).
Vs = (ρ ₀ / ρ ₁ −1) × 100 (%) (1)
In formula (1), ρ ₁ represents the density (g / cm ³ ) of the vulcanized rubber (foam rubber), and ρ ₀ represents the density (g / cm ³ ) of the solid phase portion in the vulcanized rubber (foam rubber) Show.

(Hydrophilic short fiber)
The rubber composition of the present invention preferably contains hydrophilic short fibers.
When the rubber composition contains a hydrophilic short fiber and a foaming agent, a gas generated from the foaming agent at the time of vulcanization intrudes into the interior of the hydrophilic short fiber to form a cell having a shape corresponding to the shape of the hydrophilic short fiber. The air bubbles can be formed, and the air bubbles are covered with a resin derived from hydrophilic short fibers and made hydrophilic. Therefore, when a tire is manufactured using a rubber composition containing hydrophilic short fibers and a foaming agent in a tread, the affinity of water is improved by exposing the wall surface of air bubbles to the tread surface at the time of use of the tire. As a result, air bubbles can actively take in water, and the tire can be provided with excellent drainage, and the performance of the tire on ice can be greatly improved.
As a hydrophilic resin used as a raw material of hydrophilic short fiber, ethylene-vinyl alcohol copolymer, vinyl alcohol homopolymer, poly (meth) acrylic acid or ester thereof, polyethylene glycol, carboxyvinyl copolymer, styrene-maleic acid Acid copolymer, polyvinyl pyrrolidone, vinyl pyrrolidone-vinyl acetate copolymer, mercaptoethanol and the like, and among them, ethylene-vinyl alcohol copolymer, vinyl alcohol homopolymer, poly (meth) acrylic acid is preferable. And ethylene-vinyl alcohol copolymers are particularly preferred.

  On the surface of the hydrophilic staple fiber, a coating layer is formed of a low melting point resin having an affinity for the rubber component (A), and preferably having a melting point lower than the vulcanization maximum temperature of the rubber composition. It may be By forming such a coating layer, the affinity between the coating layer and the rubber component (A) is good while effectively maintaining the affinity of the hydrophilic short fibers with water, A) Dispersion is improved. In addition, the low melting point resin melts at the time of vulcanization to form a flowable coating layer, which contributes to adhesion between the rubber component (A) and the hydrophilic short fiber, resulting in good drainage and durability. It is possible to easily realize a tire provided with a property. The thickness of the coating layer may vary depending on the content of the hydrophilic short fiber, the average diameter and the like, but is usually 0.001 to 10 μm, preferably 0.001 to 5 μm.

  The melting point of the low melting point resin used for the coating layer is preferably lower than the maximum temperature of vulcanization of the rubber composition. In addition, the maximum temperature of vulcanization means the maximum temperature which a rubber composition reaches at the time of vulcanization of a rubber composition. For example, in the case of mold vulcanization, it means the maximum temperature to which the rubber composition reaches from the time the rubber composition enters the mold to the time it is cooled out of the mold; It can be measured by embedding a thermocouple in the rubber composition. The upper limit of the melting point of the low melting point resin is not particularly limited, but is preferably selected in consideration of the above points, and is generally lower by at least 10 ° C. than the maximum vulcanization temperature of the rubber composition. Is preferable, and it is more preferable that the temperature is lower than 20.degree. The industrial vulcanization temperature of the rubber composition is generally at most about 190 ° C., for example, when the vulcanization maximum temperature is set to 190 ° C., a low melting point resin is used. The melting point of is usually selected in the range of less than 190 ° C., preferably 180 ° C. or less, more preferably 170 ° C. or less.

  The low melting point resin is preferably a polyolefin resin, and examples thereof include polyethylene, polypropylene, polybutene, polystyrene, ethylene-propylene copolymer, ethylene-methacrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-propylene And diene terpolymers, ethylene-vinyl acetate copolymers, ionomer resins of these, and the like.

The hydrophilic short fibers preferably have an average length of 0.1 to 50 mm, more preferably 1 to 7 mm, and an average diameter of preferably 1 μm to 2 mm, more preferably 5 μm to 0.5 mm. When the average length and the average diameter are in the above range, there is no possibility that the short fibers are tangled with each other more than necessary, and it is possible to secure good dispersibility.
The content of the hydrophilic short fiber in the rubber composition is preferably in the range of 0.1 to 100 parts by mass, more preferably in the range of 1 to 50 parts by mass with respect to 100 parts by mass in total of the rubber component (A). The range of 1 to 10 parts by mass is even more preferable. By keeping the content of the hydrophilic short fiber in the above range, a good balance between on-ice performance and abrasion resistance can be obtained.

(Various ingredients)
The rubber composition of the present invention comprises the rubber component (A) described above, the conjugated diene polymer (B), the filler (C), and the silane coupling agent, the blowing agent, and the hydrophilic agent contained as needed. In addition to the short staple fibers, if necessary, various components commonly used in the rubber industry, such as softeners, resins, processability improvers, stearic acid, anti-aging agents, zinc flower, vulcanization accelerators, additives A vulcanizing agent etc. may be suitably selected and contained within the range which does not injure the object of the present invention.

[Softener]
The rubber composition of the present invention may or may not contain a softener.
In general, the rubber composition improves the processability of the rubber composition by containing a softener and brings flexibility to the vulcanized rubber, but the conjugated diene polymer (B) also functions as a softener. Because of this, the rubber composition of the present invention may not contain a softener. On the other hand, the rubber composition of the present invention can also contain a softener in addition to the conjugated diene polymer (B).
Softeners include process oils, lubricating oils, naphthenic oils, paraffins, liquid paraffins, petroleum asphalts, petroleum softeners such as petroleum asphalt and petrolatum, castor oil, linseed oil, rapeseed oil, rapeseed oil, fatty oil softeners such as coconut oil, honey Wax, carnauba wax, lanolin and the like can be mentioned. These softeners may be used alone or in combination of two or more.
The content of the softener in the rubber composition of the present invention is preferably 20 parts by mass or less and more preferably 15 parts by mass or less with respect to 100 parts by mass of the rubber component.

[resin]
The rubber composition of the present invention preferably contains a resin.
As the resin, C ₅ resins, C ₅ -C ₉ resins, C ₉ resins, terpene resins, dicyclopentadiene resins, terpene - aromatic compound based resins. These resins, alone Or a combination of two or more.
The rubber composition of the present invention preferably contains a C ₅ resin or terpene resin. Using a rubber composition in a tire comprising a C ₅ resin or terpene resin, it is possible to further improve the on-ice performance of the tire.

The C ₅ resins, and petroleum chemical industry the C ₅ fraction obtained by thermal cracking of naphtha (co) polymer obtained by aliphatic petroleum resin.
The C ₅ fraction, typically 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, 3-methyl-1-olefin hydrocarbons butene, 2-methyl - Diolefin hydrocarbons such as 1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, 3-methyl-1,2-butadiene and the like are included. As the C ₅ resin may be commercially available products.

The content of _{C 5} resin is not particularly limited, preferably in the range of 5 to 50 parts by weight per 100 parts by weight of the rubber component (A), the range of 13 to 43 parts by weight Is more preferable, and the range of 15 to 25 parts by mass is even more preferable. When the content of the C ₅ resin is 5 parts by mass or more, the performance on ice is sufficiently improved, and if more than 50 parts by mass, it is possible to sufficiently ensure wear resistance.

Further, the rubber composition of the present invention may contain a C ₅ -C ₉ resins.
When a rubber composition containing a C ₅ -C ₉ resins used in the tire, it is possible to further improve the on-ice performance of the tire.
The C ₅ -C _{9 resins,} refers to C 5 -C ₉ based synthetic petroleum _resins, as the C 5 -C ₉ resins, for example, a _C 5 _{-C 11} fraction derived from petroleum, AlCl ₃ or BF Solid polymers obtained by polymerization using a Friedel-Crafts catalyst such as _{3 and the} like, more specifically, copolymers mainly comprising styrene, vinyl toluene, α-methylstyrene, indene and the like It can be mentioned.
The C ₅ -C ₉ resins, less resin of _{C 9} or more components is preferable from the viewpoint of compatibility with the rubber component (A). Here, "less C ₉ or more components", C ₉ or more components in the total resin is less than 50 wt%, preferably shall refer to or less than 40 wt%. Is the C ₅ -C ₉ resins, it is possible to use a commercially available product, for example, (manufactured by Nippon Zeon Co., Ltd.) trade name "Quinton (registered trademark) G100B", trade name "ECR213" (ExxonMobil Chemical Co., Ltd. Etc.).

The content of C ₅ -C ₉ resins include, but are not limited to, a range of 13 to 43 parts by weight is more preferable relative to 100 parts by weight of the total of the rubber component (A). When the content of C ₅ -C ₉ resins 13 parts by mass or more, the performance on ice is sufficiently improved, and if less 43 parts by mass, it is possible to sufficiently ensure wear resistance.

[Method of producing rubber composition]
Although the method for producing the rubber composition of the present invention is not particularly limited, for example, the rubber component (A) conjugated diene polymer (B) and the filler (C) were appropriately selected as necessary. It can be produced by blending various components and kneading, heating, extruding and the like.

<Pneumatic tire, studless tire>
The tire of the present invention uses the rubber composition of the present invention in a tread portion.
As described above, the vulcanized rubber obtained from the rubber composition of the present invention has more improved on-ice performance, and both the excellent on-ice performance and the excellent abrasion resistance are compatible. It is suitable for the tread portion of the inner tire, and particularly suitable for a studless tire.

  The pneumatic tire may be obtained by molding and curing after molding using an unvulcanized rubber composition according to the type and members of the applied tire, or it may be temporarily unvulcanized through a prevulcanization step or the like. After a semi-vulcanized rubber is obtained from the rubber composition, it may be molded and finally vulcanized. In addition, as a gas with which the pneumatic tire is filled, an inert gas such as nitrogen, argon, helium or the like can be used in addition to a normal air or air whose oxygen partial pressure is adjusted.

  EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples. However, these examples are for the purpose of illustration of the present invention and do not limit the present invention at all.

<Preparation of Rubber Composition>
In the compounding formulations shown in Tables 2 to 3, the rubber compositions of Examples and Comparative Examples were prepared by performing mixing in the order of the first mixing step and the final mixing step using a normal Banbury mixer. After the completion of the first mixing step, the mixture was once taken out of the Banbury mixer, and then the mixture was again introduced into the Banbury mixer to carry out the final mixing step. Further, the maximum temperature of the mixture in the first mixing step was 170 ° C., and the maximum temperature of the rubber composition in the final mixing step was 110 ° C.

<Components of Rubber Composition>
The details of each component in Tables 2 to 3 are as follows.

[Rubber component]
Polybutadiene rubber: High cis polybutadiene rubber, trade name "UBEPOL 150L", Ube Industries, Ltd., 0% of bound styrene in conjugated diene compound portion)

[Filler, silane coupling agent, oil]
Carbon black: N134, manufactured by Asahi Carbon Co., Ltd., nitrogen adsorption specific surface area (N ₂ SA) = 146 m ² / g
Silica: trade name “Nipsil AQ” manufactured by Tosoh Silica Corporation, CTAB specific surface area = 150 m ² / g, nitrogen adsorption specific surface area (N ₂ SA) = 200 m ² / g
Silane coupling agent: "Si 69", Evonic process oil: Naphthene process oil, trade name "Diana process oil NS-24", Idemitsu Kosan Co., Ltd.

[Polymer]
Polymers 1 to 8: Polymers 1 to 8 obtained by the following method

[Various ingredients]
Resin: trade name "Escorez 1102", Tonen Chemical Co., Ltd. _{(C 5} resin)
Antiaging agent: N-isopropyl-N'-phenyl-p-phenylenediamine hydrophilic short fiber: hydrophilic short fiber vulcanization accelerator prepared by the following method 1: di-2-benzothiazolyl disulfide (MBTS)
Vulcanization accelerator 2: N-cyclohexyl-2-benzothiazolylsulfenamide (CBS)
Effervescent agent: dinitrosopentamethylenetetramine (DPT)

[Polymer]
Polymers 1 to 8 were obtained as follows.
In addition, the amount of bound styrene of the conjugated diene compound portion of the polymers 1 to 8 (described as “the amount of bound styrene” in the table) and the amount of vinyl bond of the conjugated diene compound portion (described as the “vinyl bound amount” in the table) It calculated | required by the exterior method (Morero method), and showed in following Table 1. Moreover, the polystyrene conversion weight average molecular weight (it described as "weight average molecular weight" in the table | surface) measured by the gel permeation chromatography of the polymers 1-8 was shown in following Table 1.

(Polymer 1)
In a dry, nitrogen-substituted 800 mL pressure-resistant glass container, 300 g of cyclohexane, 40 g of 1,3-butadiene, and 0.66 mmol of ditetrahydrofurylpropane are injected, and then 1.46 mmol of n-butyllithium (n-BuLi) After the addition, a polymerization reaction was carried out at 50 ° C. for 1.5 hours. The polymerization conversion rate at this time was approximately 100%. Thereafter, 0.5 mL of a solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol (BHT concentration: 5% by mass) is added to the polymerization reaction system to terminate the polymerization reaction, and further the conventional method It dried according to, and the polymer 1 was obtained.
The microstructure (vinyl bond content, styrene bond content), and weight average molecular weight (Mw) of the resulting polymer 1 were measured. As a result, the vinyl bond content was 50% by mass, the styrene bond content was 0% by mass, and the Mw was 9,000.

(Polymer 2)
In a dry, nitrogen-substituted 800 mL pressure-resistant glass container, 300 g of cyclohexane, 40 g of 1,3-butadiene, and 0.66 mmol of ditetrahydrofurylpropane are injected, and then 1.02 mmol of n-butyllithium (n-BuLi) After the addition, a polymerization reaction was carried out at 50 ° C. for 1.5 hours. The polymerization conversion rate at this time was approximately 100%. Thereafter, 0.5 mL of a solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol (BHT concentration: 5% by mass) is added to the polymerization reaction system to terminate the polymerization reaction, and further the conventional method It dried according to, and the polymer 2 was obtained.
The microstructure (vinyl bond content, styrene bond content), and weight average molecular weight (Mw) of the resulting polymer 2 were measured. As a result, the vinyl bond content was 50% by mass, the styrene bond content was 0% by mass, and the Mw was 15,000.

(Polymer 3)
In a dry, nitrogen-substituted 800 mL pressure-resistant glass container, 300 g of cyclohexane, 40 g of 1,3-butadiene, 0.85 mmol of ditetrahydrofurylpropane are injected, and 1.32 mmol of n-butyllithium (n-BuLi) is further added. After the addition, a polymerization reaction was carried out at 50 ° C. for 1.5 hours. The polymerization conversion rate at this time was approximately 100%. Thereafter, 0.5 mL of a solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol (BHT concentration: 5% by mass) is added to the polymerization reaction system to terminate the polymerization reaction, and further the conventional method It dried according to, and the polymer 3 was obtained.
The microstructure (vinyl bond content, styrene bond content) and weight average molecular weight (Mw) of the obtained polymer 3 were measured. As a result, the vinyl bond content was 65% by mass, the styrene bond content was 0% by mass, and the Mw was 10,000.

(Polymer 4)
In a dry, nitrogen-substituted, 800-mL pressure-resistant glass container, 300 g of cyclohexane, 40 g of 1,3-butadiene, and 0.85 mmol of ditetrahydrofurylpropane are injected, and then 1.02 mmol of n-butyllithium (n-BuLi) After the addition, a polymerization reaction was carried out at 50 ° C. for 1.5 hours. The polymerization conversion rate at this time was approximately 100%. Thereafter, 0.5 mL of a solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol (BHT concentration: 5% by mass) is added to the polymerization reaction system to terminate the polymerization reaction, and further the conventional method It dried according to, and the polymer 4 was obtained.
The microstructure (vinyl bond content, styrene bond content) and weight average molecular weight (Mw) of the resulting polymer 4 were measured. As a result, the vinyl bond content was 65% by mass, the styrene bond content was 0% by mass, and the Mw was 15,000.

(Polymer 5)
In a dry, nitrogen-substituted 800 mL pressure-resistant glass container, 300 g of cyclohexane, 40 g of 1,3-butadiene, and 0.85 mmol of ditetrahydrofurylpropane are injected, and then 0.59 mmol of n-butyllithium (n-BuLi) After the addition, a polymerization reaction was carried out at 50 ° C. for 1.5 hours. The polymerization conversion rate at this time was approximately 100%. Thereafter, 0.5 mL of a solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol (BHT concentration: 5% by mass) is added to the polymerization reaction system to terminate the polymerization reaction, and further the conventional method It dried according to, and the polymer 5 was obtained.
The microstructure (vinyl bond content, styrene bond content) and weight average molecular weight (Mw) of the resulting polymer 5 were measured. As a result, the vinyl bond content was 65% by mass, the styrene bond content was 0% by mass, and the Mw was 25,000.

(Polymer 6)
As the polymer 6, LBR305 manufactured by Kuraray Co., Ltd. was used.
The microstructure (vinyl bond content, styrene bond content), and weight average molecular weight (Mw) of the polymer 6 were measured. As a result, the vinyl bond content was 8% by mass, the styrene bond content was 0% by mass, and the Mw was 26,000.

(Polymer 7)
In a dry, nitrogen-substituted 800 mL pressure-resistant glass container, 300 g of cyclohexane, 40 g of 1,3-butadiene, and 0.66 mmol of ditetrahydrofurylpropane are injected, and then 0.35 mmol of n-butyllithium (n-BuLi) After the addition, a polymerization reaction was carried out at 50 ° C. for 1.5 hours. The polymerization conversion rate at this time was approximately 100%. Thereafter, 0.5 mL of a solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol (BHT concentration: 5% by mass) is added to the polymerization reaction system to terminate the polymerization reaction, and further the conventional method It dried according to, and the polymer 7 was obtained.
The microstructure (vinyl bond content, styrene bond content), and weight average molecular weight (Mw) of the obtained polymer 7 were measured. As a result, the vinyl bond content was 50% by mass, the styrene bond content was 0% by mass, and the Mw was 45,000.

(Polymer 8)
300 g of cyclohexane, 30 g of 1,3-butadiene, and 10 g of styrene are poured into a dry, nitrogen-substituted, 800-mL pressure-resistant glass container, and then 1.02 mmol of n-butyllithium (n-BuLi) is added, and then 50 The polymerization reaction was carried out at ° C for 1.5 hours. The polymerization conversion rate at this time was approximately 100%. Thereafter, 0.5 mL of a solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol (BHT concentration: 5% by mass) is added to the polymerization reaction system to terminate the polymerization reaction, and further the conventional method It dried according to, and the polymer 8 was obtained.
The microstructure (vinyl bond content, styrene bond content), and weight average molecular weight (Mw) of the resulting polymer 8 were measured. As a result, the vinyl bond content was 25% by mass, the styrene bond content was 25% by mass, and the Mw was 15,000.

  Polymers 1-5, as shown in Table 1 above, had a weight-average molecular weight of 5,000 or more and less than 40,000 as measured by gel permeation chromatography, and a bound styrene content of a conjugated diene compound portion of less than 10%, It is a non-modified conjugated diene copolymer having “S + (V / 2)” of 25 or more, and is a conjugated diene polymer (B) in the present invention.

[Hydrophilic short fiber]
40 parts by mass of polyethylene [Novatec HJ360 (MFR 5.5, melting point 132 ° C.) made by Japan Polyethylene Corporation] is used in the hopper using two twin-screw extruders according to Production Example 3 disclosed in JP 2012-219245 A, 40 parts by mass of ethylene-vinyl alcohol copolymer (manufactured by Kuraray Co., Ltd., Evar F104B (MFR 4.4, melting point 183 ° C.)) was charged, and each was extruded simultaneously from the die outlet, and the fibers obtained according to the conventional method It cut into 2 mm and produced the hydrophilic staple fiber in which the coating layer which consists of polyethylene was formed.

<Vulcanization of rubber composition and evaluation of vulcanized rubber>
1. Storage modulus (G ') and loss tangent (tan δ)
With respect to a vulcanized rubber obtained by vulcanizing the rubber composition at 145 ° C. for 33 minutes, a storage elastic modulus (G ′) and a loss tangent (tan δ) were measured using a viscoelasticity measuring device ARES (manufactured by TA Instruments). The measurement was performed under the conditions of a temperature of -20 ° C, a strain of 1%, and a frequency of 15 Hz. The results are shown in Tables 2 and 3.

<Production and evaluation of tires>
Using the rubber composition obtained as described above for the tread, a test tire (tire size 195 / 65R15) was produced by a conventional method, and the foaming ratio of the tread was calculated according to the above formula (1). Next, the performance and abrasion resistance on ice were evaluated for the tire by the following method, and a comprehensive evaluation was obtained from the results of both. The results are shown in Tables 2 and 3.

2. Performance on ice Four test tires of each example and comparative example were mounted on a domestic passenger car of 1600 cc class, and braking performance on ice at ice temperature of -1 ° C was confirmed. The test tire of Comparative Example 3 was used as a control, and the index on ice was expressed as: performance on ice = (the braking distance of the test tire of Comparative Example 3 / the braking distance of the test tire other than Comparative Example 3) × 100. The larger the index value, the better the performance on ice.

3. Abrasion resistance After traveling 10,000 km on a paved road surface with a test vehicle of each example and each comparative example, the remaining groove is measured, and the travel distance required for the tread to wear 1 mm is relatively compared, The test tire of Comparative Example 3 was indexed as 100. The larger the index value, the better the wear resistance.

  From the results of the examples shown in Tables 2 to 3, it is understood that the use of the rubber composition according to the present invention is excellent in the on-ice performance and the abrasion resistance of the tire.

  The rubber composition of the present invention can be used as a tread rubber of a tire, particularly a studless tire. The tire of the present invention is also useful as a studless tire.

Claims (6)

100 parts by mass of a rubber component (A) containing 45 to 75% by mass of a natural rubber and 25 to 55% by mass of a conjugated diene-based polymer having a conjugated styrene content of 25% or less of a conjugated diene compound portion;
The polystyrene conversion weight average molecular weight measured by gel permeation chromatography is 5,000 or more and less than 40,000, the bound styrene amount S of the conjugated diene compound portion is less than 10%, and the vinyl bound amount V of the conjugated diene compound portion and the bound styrene 1 to 40 parts by mass of a non-modified conjugated diene-based polymer (B) in which the amount S satisfies the relationship of 25 ≦ [S + (V / 2)],
Filler (C),
A rubber composition containing   The rubber composition according to claim 1, wherein the vinyl bond amount V of the conjugated diene compound portion of the conjugated diene polymer (B) is 50 to 70%.   The rubber composition according to claim 1 or 2, wherein the conjugated diene polymer (B) is polybutadiene.   The rubber composition according to any one of claims 1 to 3, which has a foaming agent.   The rubber composition according to any one of claims 1 to 4, which has a hydrophilic short fiber.   The pneumatic tire which used the rubber composition of any one of Claims 1-5 for the tread part.