JP2022025672A - Rubber composition, vulcanized rubber, tread rubber for tire, and tire - Google Patents

Abstract

To provide a rubber composition capable of improving on-ice performance of a tire and excellent in workability, and a vulcanized rubber capable of improving on-ice performance of a tire and excellent in productivity.SOLUTION: The rubber composition contains a rubber component containing a diene rubber, an inorganic foaming agent, and an organic acid. The organic acid has an SP value of 9.15-16.0 (cal/cm3)1/2. The vulcanized rubber is obtained by vulcanizing the rubber composition and has a foaming rate of 1-45%.SELECTED DRAWING: None

Description

The present invention relates to a rubber composition, a vulcanized rubber, a tread rubber for a tire, and a tire.

In order to improve the braking and driving performance of tires on ice and snow roads (hereinafter referred to as "performance on ice"), research on tire tread is being actively conducted. On an ice-snow road surface, a water film is likely to be generated due to frictional heat between the ice-snow road surface and the tire, and the water film reduces the coefficient of friction between the tire and the ice-snow road surface. Therefore, in order to improve the on-ice performance of the tire, it is necessary to improve the water film removing ability of the tread of the tire.

In order to give the tread of the tire the ability to remove water film, a micro drainage groove should be provided on the road surface of the tire, the water film should be eliminated by this micro drainage groove, and the coefficient of friction of the tire on the ice and snow road surface should be increased. Can be considered. However, in this case, although it is possible to improve the performance on ice at the initial stage of use of the tire, when the tire wears, the performance on ice deteriorates. Therefore, there is a demand for a technique that does not deteriorate the performance on ice even if the tire wears.

On the other hand, a technique of applying foam rubber to the tread of a tire is also known in order to give the tread of the tire a water film removing ability. As the foamed rubber, a rubber composition containing a rubber component and a foaming agent is generally used, and here, as the foaming agent, an organic foaming agent has been mainly used. Further, in addition to the conventional organic foaming agent, efforts are being made to use an inorganic foaming agent as the foaming agent (for example, Patent Document 1 below). Since the inorganic foaming agent has a low environmental load, it is possible to provide a rubber composition having a lower environmental load by ripening the inorganic foaming agent.

International Publication No. 2017/068772

However, as examined by the present inventor, when an inorganic foaming agent such as baking soda is used as the foaming agent of the rubber composition, it is difficult to secure a balance between the vulcanization rate and the foaming rate of the rubber composition. It turned out that it was difficult to sufficiently improve the performance of tires on ice. In order to solve this problem, the present inventor has studied various additives, but depending on the type of the additive, when blended in the rubber composition, the adhesion of the rubber composition is enhanced and the rubber composition is produced. At times, it was found that the rubber composition adhered to manufacturing equipment such as rolls, resulting in poor workability.

Therefore, it is an object of the present invention to provide a rubber composition which can solve the above-mentioned problems of the prior art, can improve the performance on ice of a tire, and has excellent workability.
Further, the present invention can improve the on-ice performance of the tire, and can provide a vulcanized rubber and a tread rubber for a tire having excellent productivity, and further, a tire having excellent on-ice performance and excellent productivity. Providing is a further issue.

The gist structure of the present invention for solving the above problems is as follows.

The rubber composition of the present invention is a rubber composition containing a rubber component containing a diene-based rubber, an inorganic foaming agent, and an organic acid.
The SP value of the organic acid is 9.15 to 16.0 (cal / cm ³ ) ^1/2 .
The rubber composition of the present invention is excellent in workability, and when applied to a tire, the performance on ice of the tire can be improved.

In a preferred example of the rubber composition of the present invention, the inorganic foaming agent is selected from ammonium bicarbonate and sodium bicarbonate. In this case, the foaming of the inorganic foaming agent progresses further, and the foaming rate of the vulcanized rubber is further improved.

Here, it is particularly preferable that the inorganic foaming agent is sodium bicarbonate. In this case, foaming due to sodium bicarbonate progresses further, and the foaming rate of the vulcanized rubber is further improved.

In another preferred example of the rubber composition of the present invention, the SP value of the organic acid is 10.5 to 14.3 (cal / cm ³ ) ^1/2 . In this case, the effect of accelerating the decomposition of the inorganic foaming agent is further enhanced, and the adhesion of the rubber composition can be further reduced.

In another preferred example of the rubber composition of the present invention, the organic acid has an aromatic ring. In this case, the workability of the rubber composition is further improved.

Here, it is particularly preferable that the organic acid is benzoic acid. In this case, the workability of the rubber composition is further improved.

The rubber composition of the present invention preferably further contains a foaming aid. In this case, the foaming reaction of the inorganic foaming agent is promoted, and the foaming rate of the vulcanized rubber obtained by vulcanizing the rubber composition can be improved.

Here, it is particularly preferable to include urea as the foaming aid. In this case, the foaming of the inorganic foaming agent progresses further, and the foaming rate of the vulcanized rubber is further improved.

In another preferred example of the rubber composition of the present invention, the diene-based rubber contains at least one of a natural rubber and a synthetic diene-based rubber. In this case, by applying the rubber composition to the tire, the performance on ice of the tire can be further improved.

Here, it is more preferable that the synthetic diene rubber contains at least one selected from the group consisting of isoprene rubber, styrene-butadiene rubber, and butadiene rubber. In this case, by applying the rubber composition to the tire, the performance on ice of the tire can be further improved.

Further, the vulcanized rubber of the present invention is characterized by having the above rubber composition vulcanized and having a foaming rate of 1 to 45%. The vulcanized rubber of the present invention is excellent in productivity, and when applied to a tire, the performance on ice of the tire can be improved.

Further, the tread rubber for a tire of the present invention is characterized by comprising the above-mentioned rubber composition or the above-mentioned vulcanized rubber. The tread rubber for a tire of the present invention is excellent in productivity, and when applied to a tire, the performance on ice of the tire can be improved.

Further, the tire of the present invention is characterized in that the above-mentioned rubber composition or the above-mentioned vulcanized rubber is provided in the tread portion. The tire of the present invention has excellent productivity and excellent on-ice performance.

According to the present invention, it is possible to improve the performance of a tire on ice, and it is possible to provide a rubber composition having excellent workability.
Further, according to the present invention, it is possible to improve the on-ice performance of the tire, and the vulcanized rubber and the tread rubber for the tire, which are excellent in productivity, and further, the on-ice performance is excellent, and the productivity is excellent. Tires can be provided.

Hereinafter, the rubber composition, the vulcanized rubber, the tread rubber for a tire, and the tire of the present invention will be illustrated and described in detail based on the embodiments thereof.

<Rubber composition>
The rubber composition of the present invention contains a rubber component containing a diene-based rubber, an inorganic foaming agent, and an organic acid, and the SP value of the organic acid is 9.15 to 16.0 (cal / cm ³ ). It is characterized by being ^1/2 .

In the rubber composition of the present invention, the inorganic foaming agent foams during vulcanization of the rubber composition to generate bubbles (voids) in the rubber composition (vulcanized rubber), and the organic acid is rubber. At the time of vulcanization of the composition, the rate of decomposition / foaming reaction of the inorganic foaming agent and the rate of vulcanization reaction of the rubber composition are balanced and optimized to improve the foaming rate of the vulcanized rubber. If the rubber composition does not contain an organic acid, it is difficult to cause a sufficient foaming reaction during vulcanization (heating) of the rubber composition, and the foaming rate of the vulcanized rubber cannot be sufficiently improved. ..
Further, the organic acid contained in the rubber composition of the present invention has an SP value of 9.15 to 16.0 (cal / cm ³ ) ^1/2 , while suppressing an increase in the adhesion of the rubber composition. The decomposition of the inorganic foaming agent can be sufficiently promoted. Here, if the SP value of the organic acid is less than 9.15 (cal / cm ³ ) ^1/2 , the decomposition of the inorganic foaming agent cannot be sufficiently promoted, and the SP value of the organic acid is 16.0 (16.0). cal / cm ³ ) If it exceeds ^1/2 , the adhesion of the rubber composition containing an organic acid becomes high, and the rubber composition adheres to the production equipment such as a roll during the production of the rubber composition. Sex gets worse.
Therefore, the rubber composition of the present invention is excellent in workability, and when applied to a tire, the performance on ice of the tire can be improved.

(Rubber component)
The rubber component of the rubber composition of the present invention contains a diene-based rubber. The ratio of the diene-based rubber in the rubber component is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass. The rubber component may contain a rubber other than the diene-based rubber, but is preferably composed of only the diene-based rubber.

The diene-based rubber may be natural rubber (NR), synthetic diene-based rubber, or both. By applying a rubber composition containing at least one of natural rubber and synthetic diene rubber to the tire, the on-ice performance of the tire can be further improved.

Examples of the synthetic diene rubber include isoprene rubber (IR), styrene-butadiene rubber (SBR), butadiene rubber (BR), styrene-isoprene rubber (SIR), and chloroprene rubber (CR). Among these, isoprene rubber, styrene-butadiene rubber, and butadiene rubber are more preferable as the synthetic diene rubber. By applying a rubber composition containing at least one selected from the group consisting of isoprene rubber, styrene-butadiene rubber, and butadiene rubber to a tire, the on-ice performance of the tire can be further improved.
Further, the diene-based rubber (rubber component) may be used alone or in a blend of two or more.

The diene-based rubber (rubber component) may be unmodified rubber or modified rubber.
When the diene-based rubber is modified, the diene-based rubber is a hydrocarbyloxysilane compound represented by the following general formula (I), a hydrocarbyloxysilane compound represented by the following general formula (II), and the following general formula. The hydrocarbyloxysilane compound represented by (III), the coupling agent represented by the following general formula (IV), the coupling agent represented by the following general formula (V), and the following general formula (VI). It is preferably modified with at least one selected from the group consisting of lithioamine and vinylpyridine.

上記一般式（Ｉ）中、ｑ１＋ｑ２＝３（但し、ｑ１は０～２の整数であり、ｑ２は１～３の整数である。）である。
Ｒ^１１は、炭素数１～２０の二価の脂肪族若しくは脂環式炭化水素基又は炭素数６～１８の二価の芳香族炭化水素基である。
Ｒ^１２及びＲ^１３は、それぞれ独立して、加水分解性基、炭素数１～２０の一価の脂肪族若しくは脂環式炭化水素基又は炭素数６～１８の一価の芳香族炭化水素基である。
Ｒ^１４は、炭素数１～２０の一価の脂肪族若しくは脂環式炭化水素基又は炭素数６～１８の一価の芳香族炭化水素基であり、ｑ１が２の場合には同一でも異なっていてもよい。
Ｒ^１５は、炭素数１～２０の一価の脂肪族若しくは脂環式炭化水素基又は炭素数６～１８の一価の芳香族炭化水素基であり、ｑ２が２以上の場合には同一でも異なっていてもよい。

In the above general formula (I), q1 + q2 = 3 (where q1 is an integer of 0 to 2 and q2 is an integer of 1 to 3).
R ¹¹ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ¹² and R ¹³ are independently hydrolyzable groups, monovalent aliphatic or alicyclic hydrocarbon groups having 1 to 20 carbon atoms, or monovalent aromatic hydrocarbon groups having 6 to 18 carbon atoms. Is.
R ¹⁴ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when q1 is 2, they are the same or different. May be.
^R15 is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and may be the same when q2 is 2 or more. It may be different.

上記一般式（ＩＩ）中、ｒ１＋ｒ２＝３（但し、ｒ１は１～３の整数であり、ｒ２は０～２の整数である。）である。
Ｒ^２１は、炭素数１～２０の二価の脂肪族若しくは脂環式炭化水素基又は炭素数６～１８の二価の芳香族炭化水素基である。
Ｒ^２２は、ジメチルアミノメチル基、ジメチルアミノエチル基、ジエチルアミノメチル基、ジエチルアミノエチル基、メチルシリル（メチル）アミノメチル基、メチルシリル（メチル）アミノエチル基、メチルシリル（エチル）アミノメチル基、メチルシリル（エチル）アミノエチル基、ジメチルシリルアミノメチル基、ジメチルシリルアミノエチル基、炭素数１～２０の一価の脂肪族若しくは脂環式炭化水素基又は炭素数６～１８の一価の芳香族炭化水素基であり、ｒ１が２以上の場合には同一でも異なっていてもよい。
Ｒ^２３は、炭素数１～２０のヒドロカルビルオキシ基、炭素数１～２０の一価の脂肪族若しくは脂環式炭化水素基又は炭素数６～１８の一価の芳香族炭化水素基であり、ｒ２が２の場合には同一でも異なっていてもよい。

In the above general formula (II), r1 + r2 = 3 (where r1 is an integer of 1 to 3 and r2 is an integer of 0 to 2).
R ²¹ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.
R ²² has a dimethylaminomethyl group, a dimethylaminoethyl group, a diethylaminomethyl group, a diethylaminoethyl group, a methylsilyl (methyl) aminomethyl group, a methylsilyl (methyl) aminoethyl group, a methylsilyl (ethyl) aminomethyl group, and a methylsilyl (ethyl). Aminoethyl group, dimethylsilylaminomethyl group, dimethylsilylaminoethyl group, monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. Yes, when r1 is 2 or more, it may be the same or different.
R ²³ is a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. When r2 is 2, they may be the same or different.

上記一般式（ＩＩＩ）中、Ａ^３は、（チオ）エポキシ、（チオ）イソシアネート、（チオ）ケトン、（チオ）アルデヒド、イミン、アミド、イソシアヌル酸トリヒドロカルビルエステル、（チオ）カルボン酸エステル、（チオ）カルボン酸の金属塩、カルボン酸無水物、カルボン酸ハロゲン化物及び炭酸ジヒドロカルビルエステルから選ばれる少なくとも１種の官能基を有する一価の基である。ここで、「（チオ）エポキシ」とは、エポキシ及びチオエポキシを指し、「（チオ）インシアネート」とは、インシアネート及びチオインシアネートを指し、「（チオ）ケトン」とは、ケトン及びチオケトンを指し、「（チオ）アルデヒド」とは、アルデヒド及びチオアルデヒドを指し、「（チオ）カルボン酸エステル」とは、カルボン酸エステル及びチオカルボン酸エステルを指し、「（チオ）カルボン酸の金属塩」とは、カルボン酸の金属塩及びチオカルボン酸の金属塩を指す。
Ｒ^３１は、単結合又は二価の不活性炭化水素基であり、該二価の不活性炭化水素基は、炭素数が１～２０であることが好ましい。
Ｒ^３２及びＲ^３３は、それぞれ独立に炭素数１～２０の一価の脂肪族炭化水素基又は炭素数６～１８の一価の芳香族炭化水素基を示し、ｎは０から２の整数であり、Ｒ^３２が複数ある場合、複数のＲ^３２は同一でも異なっていてもよく、ＯＲ^３３が複数ある場合、複数のＯＲ^３３は同一でも異なっていてもよい。
また、一般式（ＩＩＩ）で表されるヒドロカルビルオキシシラン化合物の分子中には、活性プロトン及びオニウム塩は含まれない。

In the above general formula ( ^III ), A3 is (thio) epoxy, (thio) isocyanate, (thio) ketone, (thio) aldehyde, imine, amide, isocyanuric acid trihydrocarbyl ester, (thio) carboxylic acid ester, (thio) Thio) A monovalent group having at least one functional group selected from metal salts of carboxylic acids, carboxylic acid anhydrides, carboxylic acid halides and dihydrocarbylcarbonates. Here, "(thio) epoxy" refers to epoxy and thioepoxy, "(thio) incyanate" refers to incyanate and thioincyanate, and "(thio) ketone" refers to ketone and thioketone. The term "(thio) aldehyde" refers to aldehydes and thioaldehydes, the term "(thio) carboxylic acid ester" refers to carboxylic acid esters and thiocarboxylic acid esters, and the term "metal salt of (thio) carboxylic acid". Refers to a metal salt of carboxylic acid and a metal salt of thiocarboxylic acid.
R ³¹ is a single bond or a divalent inert hydrocarbon group, and the divalent inert hydrocarbon group preferably has 1 to 20 carbon atoms.
R ³² and R ³³ independently represent a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and n is an integer of 0 to 2. If there are a plurality of R ^32s , the plurality of R ^32s may be the same or different, and if there are a plurality of OR ^{33s, the plurality of OR 33s may} be the same or different.
Further, the molecule of the hydrocarbyloxysilane compound represented by the general formula (III) does not contain an active proton and an onium salt.

In the general formula ( ^III ), among the functional groups in A3, imine includes ketimine, aldimine and amidine, and the (thio) carboxylic acid ester includes unsaturated carboxylic acid ester such as acrylate and methacrylate. Examples of the metal of the metal salt of (thio) carboxylic acid include alkali metals, alkaline earth metals, Al, Sn, Zn and the like.
As the divalent inert hydrocarbon group of R ³¹ , an alkylene group having 1 to 20 carbon atoms can be preferably mentioned. The alkylene group may be linear, branched or cyclic, but a linear group is particularly preferable. Examples of the linear alkylene group include a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, an octamethylene group, a decamethylene group, a dodecamethylene group and the like.
Examples of R ³² and R ³³ include an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, and an aralkyl group having 7 to 18 carbon atoms. Here, the alkyl group and the alkenyl group may be linear, branched or cyclic, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group and an n-butyl group. Isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group, cyclopentyl group, cyclohexyl group, vinyl group, propenyl group, allyl group, hexenyl group, octenyl group, Cyclopentenyl group, cyclohexenyl group, etc. may be mentioned. Further, the aryl group may have a substituent such as a lower alkyl group on the aromatic ring, and examples thereof include a phenyl group, a tolyl group, a xsilyl group, a naphthyl group and the like. Further, the aralkyl group may have a substituent such as a lower alkyl group on the aromatic ring, and examples thereof include a benzyl group, a phenethyl group, a naphthylmethyl group and the like.
n is an integer of 0 to 2, preferably 0, and it is necessary that the molecule does not have an active proton and an onium salt.

Examples of the hydrocarbyloxysilane compound represented by the general formula (III) include 2-glycidoxyethyltrimethoxysilane and 2-glycidoxyethyltriethoxysilane as the (thio) epoxy group-containing hydrocarbyloxysilane compound. (2-glycidoxyethyl) methyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, (3-glycidoxypropyl) methyldimethoxysilane, 2- (3,4) -Epoxide cyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxidecyclohexyl) ethyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyl (methyl) dimethoxysilane, 2- (3,4-epoxidecyclohexyl) ) Trimethoxysilanes and those in which the epoxy group in these compounds is replaced with a thioepoxide group can be preferably mentioned. Among these, 3-glycidoxypropyltrimethoxysilane and 2- (3,4-epoxycyclohexyl) Trimethoxysilane is particularly suitable.
Further, as the imine group-containing hydrocarbyloxycyan compound, N- (1,3-dimethylbutylidene) -3- (triethoxysilyl) -1-propaneamine and N- (1-methylethylidene) -3- (triethoxy). Cyril) -1-propaneamine, N-ethylidene-3- (triethoxysilyl) -1-propaneamine, N- (1-methylpropanol) -3- (triethoxysilyl) -1-propaneamine, N- (4-N, N-dimethylaminobenzylidene) -3- (triethoxysilyl) -1-propaneamine, N- (cyclohexylidene) -3- (triethoxysilyl) -1-propaneamine and their triethoxy Trimethoxysilyl compound, methyldiethoxysilyl compound, ethyldiethoxysilyl compound, methyldimethoxysilyl compound, ethyldimethoxysilyl compound and the like corresponding to the silyl compound can be preferably mentioned, and among these, N- (1-methyl) can be preferably mentioned. Propyridene) -3- (triethoxysilyl) -1-propaneamine and N- (1,3-dimethylbutylidene) -3- (triethoxysilyl) -1-propaneamine are particularly suitable.

上記一般式（ＩＶ）中、Ｒ^４１、Ｒ^４２及びＲ^４３は、それぞれ独立して単結合又は炭素数１～２０のアルキレン基を示す。
Ｒ^４４、Ｒ^４５、Ｒ^４６、Ｒ^４７及びＲ^４９は、それぞれ独立して炭素数１～２０のアルキル基を示す。
Ｒ^４８及びＲ^５１は、それぞれ独立して炭素数１～２０のアルキレン基を示す。
Ｒ^５０は、炭素数１～２０の、アルキル基又はトリアルキルシリル基を示す。
ｍは、１～３の整数を示し、ｐは、１又は２を示す。
Ｒ^４１～Ｒ^５１、ｍ及びｐは、複数存在する場合、それぞれ独立しており、ｉ、ｊ及びｋは、それぞれ独立して０～６の整数を示し、但し、（ｉ＋ｊ＋ｋ）は、３～１０の整数である。
Ａ^４は、炭素数１～２０の、炭化水素基、又は、酸素原子、窒素原子、ケイ素原子、硫黄原子及びリン原子からなる群から選択される少なくとも一種の原子を有し、活性水素を有しない有機基を示す。

In the above general formula (IV), R ⁴¹ , R ⁴² and R ⁴³ each independently represent a single bond or an alkylene group having 1 to 20 carbon atoms.
R ⁴⁴ , R ⁴⁵ , R ⁴⁶ , R ⁴⁷ and R ⁴⁹ each independently represent an alkyl group having 1 to 20 carbon atoms.
R ⁴⁸ and R ⁵¹ each independently represent an alkylene group having 1 to 20 carbon atoms.
R50 represents an alkyl group or a trialkylsilyl group having 1 to ²⁰ carbon atoms.
m represents an integer of 1 to 3, and p represents 1 or 2.
When a plurality of R ⁴¹ to R ⁵¹ , m and p exist, they are independent of each other, i, j and k each independently indicate an integer of 0 to 6, where (i + j + k) is 3 to 3. It is an integer of 10.
^A4 has a hydrocarbon group having 1 to 20 carbon atoms or at least one atom selected from the group consisting of an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom and a phosphorus atom, and has active hydrogen. Indicates an organic group that does not.

Here, the coupling agent represented by the general formula (IV) is tetrakis [3- (2,2-dimethoxy-1-aza-2-silacyclopentane) propyl] -1,3-propanediamine, tetrakis. It is preferably at least one selected from the group consisting of (3-trimethoxysilylpropyl) -1,3-propanediamine and tetrakis (3-trimethoxysilylpropyl) -1,3-bisaminomethylcyclohexane.

(R ⁵ ) _a ZX _b ... (V)
In the general formula (V), Z is tin or silicon, and X is chlorine or bromine.
(R ⁵ ) has an alkyl having 1 to 20 carbon atoms, a cycloalkyl having 3 to 20 carbon atoms, an aryl having 6 to 20 carbon atoms, and 7 to 20 carbon atoms. Selected from a group of Aralkils. Here, specific examples of ⁽ R5) include a methyl group, an ethyl group, an n-butyl group, a neophil group, a cyclohexyl group, an n-octyl group, a 2-ethylhexyl group and the like.
a is 0 to 3 and b is 1 to 4, where a + b = 4.

As the coupling agent represented by the general formula (V), tin tetrachloride, (R ⁵ ) SnCl ₃ , (R ⁵ ) ₂ SnCl ₂ , (R ⁵ ) ₃ SnCl and the like are preferable, and among them, tetrachloride is preferable. Tin is particularly preferred.

［式（ＶＩＩ）中、Ｒ^７１及びＲ^７２は、それぞれ独立して、１～１２の炭素原子を有する、アルキル、シクロアルキル又はアラルキル基を示す。］又は下記式（ＶＩＩＩ）：

［式（ＶＩＩＩ）中、Ｒ^８１は、３～１６のメチレン基を有するアルキレン、１～１２個の炭素原子を有する線状若しくは分枝アルキル、シクロアルキル、ビシクロアルキル、アリール、アラルキルを置換基とする置換アルキレン、オキシジエチレン又はＮ－アルキルアミノ－アルキレン基を示す。］である。 (AM) Li (Q) _y ... (VI)
In the above general formula (VI), y is 0 or 0.5 to 3, and (Q) is a solubilizing component selected from the group consisting of hydrocarbons, ethers, amines or mixtures thereof. , (AM) is the following formula (VII):

[In formula (VII), R ⁷¹ and R ⁷² each independently represent an alkyl, cycloalkyl or aralkyl group having 1-12 carbon atoms. ] Or the following formula (VIII):

[In formula (VIII), R ⁸¹ is alkylene having 3 to 16 methylene groups, linear or branched alkyl having 1 to 12 carbon atoms, cycloalkyl, bicycloalkyl, aryl, aralkyl as substituents. Substituents to be substituted alkylene, oxydiethylene or N-alkylamino-alkylene groups. ].

The presence of Q in the general formula (VI) makes the lithioamine soluble in the hydrocarbon solvent. Further, Q includes dienyl or vinyl aromatic polymers or copolymers having a degree of polymerization consisting of 3 to about 300 polymerization units. These polymers and copolymers include polybutadiene, polystyrene, polyisoprene and copolymers thereof. Other examples of Q include polar ligands [eg, tetrahydrofuran (THF), tetramethylethylenediamine (TMEDA), etc.].

The lithioamine represented by the above general formula (VI) can also be a mixture with an organic alkali metal. The organic alkali metals are preferably of the general formula: (R ⁹¹ ) M, (R ⁹² ) OM, (R ⁹³ ) C (O) OM, (R ⁹⁴ ) (R ⁹⁵ ) NM and (R ⁹⁶ ) SO. Selected from the group consisting of compounds represented by 3M, where _each of (R ⁹¹ ), (R ⁹² ), (R ⁹³ ), (R ⁹⁴ ), (R ⁹⁵ ) and (R ⁹⁶ ) is It is selected from the group consisting of alkyl, cycloalkyl, alkenyl, aryl and phenyl having about 1 to about 12 carbon atoms. The metal component M is selected from the group consisting of Na, K, Rb and Cs. Preferably M is Na or K.
The mixture may also preferably contain the organic alkali metal in a mixing ratio consisting of about 0.5 to about 0.02 equivalents per lithium equivalent in the lithioamine.

Further, in the mixture of the lithioamine and the organic alkali metal, a chelating agent can be used as an aid to prevent the polymerization from becoming non-uniform. Useful chelating agents include, for example, tetramethylethylenediamine (TMEDA), oxolanyl cyclic acetals, cyclic oligomeric oxolanyl alkanes and the like. Particularly preferred are cyclic oligomeric oxolanyl alkanes, and specific examples thereof include 2,2-bis (tetrahydrofuryl) propane.

Examples of the vinylpyridine include 2-vinylpyridine, 4-vinylpyridine and the like.

Among the various modifiers mentioned above, N, N-bis (trimethylsilyl) -3- [diethoxy (methyl) silyl] propylamine, N- (1,3-dimethylbutylidene) -3-triethoxysilyl-1- Propylamine, 3-glycidoxypropyltrimethoxysilane, tetrakis (3-trimethoxysilylpropyl) -1,3-propanediamine, tin tetrachloride, reaction product of hexamethyleneimine and n-butyllithium, 4-vinyl Pyridyl and 2-vinylpyridine are preferred.

Further, it is more preferable that the rubber composition of the present invention contains the styrene-butadiene rubber having a styrene bond amount of 15% by mass or less as the styrene-butadiene rubber. By applying a rubber composition containing styrene-butadiene rubber having a styrene bond amount of 15% by mass or less to a tire, the on-ice performance of the tire can be significantly improved.
In the present specification, the styrene bond amount of the styrene-butadiene rubber can be obtained from the integral ratio of the ¹ H-NMR spectrum.

(Inorganic foaming agent)
The rubber composition of the present invention contains an inorganic foaming agent. The inorganic foaming agent is an inorganic compound and has a low environmental load. Further, the inorganic foaming agent has an action of foaming (foaming by heating) at the time of vulcanization of the rubber composition to generate bubbles (voids) in the rubber composition (vulcanized rubber).

Examples of the inorganic foaming agent include carbonates and bicarbonates (bicarbonates), and among these, hydrogen carbonate is preferable.
Examples of the carbonate include ammonium carbonate, sodium carbonate, potassium carbonate and the like. Examples of the bicarbonate include ammonium bicarbonate, sodium bicarbonate, potassium bicarbonate and the like. Among these, as the inorganic foaming agent, ammonium bicarbonate and sodium bicarbonate are preferable. In this case, the foaming of the inorganic foaming agent progresses further, the foaming rate of the vulture rubber is further improved, and the performance on ice of the tire is further improved. Can be improved.
The inorganic foaming agent may be used alone or in combination of two or more.

Further, as the inorganic foaming agent, sodium bicarbonate (NaHCO ₃ ) is particularly preferable. When the rubber composition contains sodium bicarbonate, the foaming due to sodium bicarbonate progresses further, the foaming rate of the vulture rubber is further improved, and when applied to the tire, the performance on ice of the tire is further improved. be able to.

The content of the inorganic foaming agent is preferably in the range of 1 to 12 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of the foaming rate of the vulcanized rubber and the performance on ice of the tire, and is preferably 1 to 10 parts by mass. The range is even more preferred, the range of 2 to 7 parts by mass is even more preferred, and the range of 4 to 6.5 parts by mass is particularly preferred.

(Organic acid)
The rubber composition of the present invention contains an organic acid, and the SP value of the organic acid is 9.15 to 16.0 (cal / cm ³ ) ^1/2 . The organic acid balances the rate of decomposition / foaming reaction of the inorganic foaming agent and the rate of vulcanization reaction of the rubber composition at the time of vulcanization of the rubber composition, and improves the foaming rate of the vulcanized rubber. Has the effect of causing. By blending the organic acid into the rubber composition, while maintaining good workability of the rubber composition, the decomposition / foaming reaction of the inorganic foaming agent is promoted, and the speed of the decomposition / foaming reaction and the rubber composition. It is possible to improve the foaming rate of the vulcanized rubber by balancing the speed of the vulcanization reaction of the object, and by applying it to the tire, the performance on ice of the tire can be improved. If the rubber composition does not contain the organic acid, it is difficult to cause a sufficient foaming reaction during vulcanization (heating) of the rubber composition, and the foaming rate of the vulcanized rubber can be sufficiently improved. Can not.

If the SP value of the organic acid is less than 9.15 (cal / cm ³ ) ^1/2 , the decomposition of the inorganic foaming agent cannot be sufficiently promoted, and the SP value of the organic acid is 16.0 (cal / cm 3). / Cm ³ ) If it exceeds ^1/2 , the adhesion of the rubber composition containing an organic acid becomes high, and the rubber composition adheres to the production equipment such as a roll during the production of the rubber composition, and the rubber composition Workability of things deteriorates.
The SP value of the organic acid is preferably 10.5 to 14.3 (cal / cm ³ ) ^1/2 . When the SP value of the organic acid is 10.5 (cal / cm ³ ) ^1/2 or more, the effect of promoting the decomposition of the inorganic foaming agent is further enhanced, and the SP value of the organic acid is 14.3 (14.3). cal / cm ³ ) When it is ^1/2 or less, the adhesion of the rubber composition containing an organic acid can be further reduced, and the workability of the rubber composition is further improved.
The general-purpose stearic acid as a vulcanization aid in the rubber composition has an SP value of 9.12 (cal / cm ³ ) ^1/2 , and has a low effect of promoting the decomposition of the inorganic foaming agent.
Here, in the present specification, the SP value (solubility parameter) of the organic acid is calculated according to the Fedors method.

The organic acid may be any of monocarboxylic acid, dicarboxylic acid, tricarboxylic acid and the like, and may be aliphatic or aromatic, and further, a hydroxyl group, a ketone group or an ethylenically non-philic acid. It may have a functional group other than the carboxyl group, such as a saturated group.
As the organic acid, one having an aromatic ring (aromatic) is preferable, and a monocarboxylic acid is preferable. When the organic acid has an aromatic ring, the adhesion of the rubber composition can be further reduced, the workability of the rubber composition is further improved, and it becomes more difficult to adhere to the manufacturing equipment such as rolls.

Examples of the aliphatic monocarboxylic acid include palmitic acid and the like.
Examples of the aliphatic dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid.
Examples of the aromatic monocarboxylic acid include benzoic acid and salicylic acid.
Examples of the aromatic dicarboxylic acid include phthalic acid and the like.
Examples of the organic acid having a functional group other than the carboxyl group include tartrate acid, malic acid, maleic acid, glycolic acid, α-ketoglutaric acid and the like.
The organic acid may be used alone or in combination of two or more.

Benzoic acid is particularly preferable as the organic acid. When benzoic acid is added to the rubber composition, the adhesion of the rubber composition can be further reduced, the workability of the rubber composition is further improved, and it becomes more difficult to adhere to the rubber composition by manufacturing equipment such as a roll.

The content of the organic acid is in the range of 0.1 to 7 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of workability of the rubber composition, foaming rate of vulcanized rubber and performance on ice of the tire. The range of 1.5 to 7 parts by mass is more preferable, and the range of 3 to 7 parts by mass is even more preferable.

The total content of the inorganic foaming agent and the organic acid is 3 parts by mass or more and 15 parts by mass with respect to 100 parts by mass of the rubber component from the viewpoint of the foaming rate of the vulgarized rubber and the performance on ice of the tire. It is preferably less than, more preferably 5 parts by mass or more and less than 15 parts by mass, and even more preferably 7 parts by mass or more and less than 15 parts by mass.

The mass ratio of the inorganic foaming agent to the organic acid (inorganic foaming agent: organic acid) is 1: 0.5 to 1: 1.5 from the viewpoint of the foaming rate of the vulcanized rubber and the performance on ice of the tire. Is preferable, and 1: 0.7 to 1: 1.3 is more preferable.

(Effervescent aid)
The rubber composition of the present invention preferably further contains a foaming aid. The foaming aid has an action of promoting the foaming reaction of the inorganic foaming agent during vulcanization of the rubber composition. When the rubber composition contains a foaming aid, the foaming reaction of the inorganic foaming agent is promoted, the foaming rate of the obtained vulcanized rubber can be improved, and by applying it to a tire, the performance on ice of the tire can be improved. It can be further improved.

Examples of the foaming aid include urea, zinc stearate, zinc benzenesulfinate, zinc white and the like, and among these, urea is particularly preferable. When the rubber composition contains urea, the foaming of the inorganic foaming agent proceeds further, the foaming rate of the vulcanized rubber is further improved, and by applying it to a tire, the performance on ice of the tire can be further improved.
The urea may be treated with an oil treat or the like. By treating with oil treat or the like, urea can be made hydrophobic and the dispersibility of urea in the rubber component can be improved. The oil used for the oil treat is not particularly limited, and various oils can be used.
The foaming aid may be used alone or in combination of two or more.

The content of the foaming aid is preferably in the range of 4 to 14 parts by mass, preferably 6 to 14 parts by mass with respect to 100 parts by mass of the rubber component, from the viewpoint of the foaming rate of the vulcanized rubber and the performance on ice of the tire. The range is more preferred.

When the rubber composition of the present invention contains a foaming aid, the total content of the inorganic foaming agent and the foaming aid is preferably in the range of 1 to 30 parts by mass with respect to 100 parts by mass of the rubber component. When the total content of the inorganic foaming agent and the foaming aid is 1 to 30 parts by mass, the rubber composition is sufficiently foamed during vulcanization, and the foaming rate of the vulcanized rubber is further improved.
The total content of the inorganic foaming agent and the foaming aid is more preferably 3 parts by mass or more, more preferably 5 parts by mass or more, based on 100 parts by mass of the rubber component, from the viewpoint of the foaming rate of the vulcanized rubber. More preferred. Further, the total content of the inorganic foaming agent and the foaming aid is more preferably 25 parts by mass or less, more preferably 20 parts by mass or less, based on 100 parts by mass of the rubber component, from the viewpoint of the foaming rate of the vulcanized rubber. Is even more preferable.

When the rubber composition of the present invention contains a foaming aid, the mass ratio of the inorganic foaming agent to the foaming aid (inorganic foaming agent: foaming aid) is 1: 1.1 to 1: 3.3. The range is preferred. When the mass ratio (inorganic foaming agent: foaming aid) is in the range of 1: 1.1 to 1: 3.3, the rubber composition is sufficiently foamed during vulcanization, and the foaming rate of the vulcanized rubber is increased. Further improvement.
The mass ratio of the inorganic foaming agent to the foaming aid (inorganic foaming agent: foaming aid) is more preferably 1: 1.2 or more from the viewpoint of the foaming ratio of the vulcanized rubber. 3 or more is more preferable. Further, the mass ratio of the inorganic foaming agent to the foaming aid (inorganic foaming agent: foaming aid) is more preferably 1: 3.2 or less from the viewpoint of the foaming rate of the vulcanized rubber, and 1: 3. 1 or less is more preferable, 1: 2.9 or less is further preferable, 1: 2.7 or less is further preferable, 1: 2.5 or less is further preferable, and 1: 2.3 or less is particularly preferable.

When the rubber composition of the present invention contains a foaming aid, the total content of the inorganic foaming agent, the organic acid and the foaming aid is determined from the viewpoint of the foaming rate of the vulcanized rubber and the on-ice performance of the tire. The range of 5 to 40 parts by mass is preferable, the range of 9 to 35 parts by mass is more preferable, and the range of 12 to 31 parts by mass is even more preferable with respect to 100 parts by mass of the rubber component.

When the rubber composition of the present invention contains a foaming aid, the mass ratio of the inorganic foaming agent, the organic acid and the foaming aid (inorganic foaming agent: organic acid: foaming aid) is determined by the vulture rubber. From the viewpoint of the foaming ratio and the performance of the tire on ice, 1: 0.3: 0.8 to 1: 2: 5 is preferable, and 1: 0.5: 1 to 1: 1.5: 3.5 is more preferable. , 1: 0.6: 1.1 to 1: 1.4: 3.3 are even more preferable, and 1: 0.7: 1.3 to 1: 1.3: 2.7 are particularly preferable.

(Staple)
The rubber composition of the present invention further preferably contains short fibers, and more preferably hydrophilic short fibers. Here, the hydrophilic short fibers refer to short fibers having a contact angle with water of 5 to 80 °. For the contact angle of the hydrophilic short fibers with water, prepare a test piece obtained by molding the hydrophilic resin used as the raw material of the hydrophilic short fibers into a smooth plate shape, and prepare an automatic contact angle meter DM-manufactured by Kyowa Surface Chemical Co., Ltd. When water is dropped on the surface of the test piece under the condition of 25 ° C. and 55% relative humidity using 301, and immediately after that, when observed from the side, the straight line formed by the surface of the test piece and the tangent line on the surface of the water drop are formed. It can be obtained by measuring the angle formed.

When the rubber composition contains short fibers, the gas generated from the inorganic foaming agent during vulcanization penetrates into the short fibers, and the shape of the short fibers is contained in the vulcanized rubber obtained by vulcanizing the rubber composition. A void (bubble) having a shape corresponding to the above is formed. When such vulcanized rubber is applied to the tread of a tire, the voids exist in the vulcanized rubber, so that the voids function as drainage grooves as the tire wears, and the tire is provided with excellent water film removing ability. , The performance on ice of the tire can be further improved.

When the rubber composition contains hydrophilic staple fibers, the gas generated from the inorganic foaming agent during brewing infiltrates into the inside of the hydrophilic staple fibers, and voids having a shape corresponding to the shape of the hydrophilic staple fibers. (Bubbles) are formed, and the walls of the voids are covered with a resin derived from hydrophilic staple fibers to make them hydrophilic. Therefore, when a tire is manufactured using a rubber composition containing hydrophilic short fibers for a tread, the wall surface of the void is exposed on the surface of the tread when the tire is used, so that the affinity with water is improved and the void is used. Can take in water positively, and the tire is provided with excellent water film removing ability and drainage property, and the performance on ice of the tire can be greatly improved.
Further, when the rubber composition contains hydrophilic short fibers, the length of the voids (bubbles) of the vulcanized rubber obtained by vulcanizing the rubber composition becomes longer, and the performance on ice can be further improved. ..

Examples of the hydrophilic resin used as a raw material for the hydrophilic short fibers include a resin having a hydrophilic group in the molecule, and specifically, a resin containing an oxygen atom, a nitrogen atom or a sulfur atom is preferable. A resin containing at least one functional group selected from the group consisting of -OH, -COOH, -OCOR (R is an alkyl group), -NH ₂ , -NCO, and -SH is more preferable, and -OH, It is even more preferable that the resin contains at least one functional group selected from the group consisting of -COOH, -NH ₂ and -NCO.

Various resins can be used as the raw material for the staple fibers. Further, as the hydrophilic resin used as a raw material for the hydrophilic short fibers, more specifically, ethylene-vinyl alcohol copolymer, vinyl alcohol homopolymer, poly (meth) acrylic acid or an ester thereof, polyethylene glycol, carboxy Examples thereof include vinyl copolymers, styrene-maleic acid copolymers, polyvinylpyrrolidone, vinylpyrrolidone-vinyl acetate copolymers, mercaptoethanol, etc. Among these, ethylene-vinyl alcohol copolymers, vinyl alcohol homopolymers, etc. Poly (meth) acrylic acid is preferred, and ethylene-vinyl alcohol copolymer is particularly preferred.

On the surface of the hydrophilic short fibers, a coating layer made of a low melting point resin having an affinity for the rubber component and preferably having a melting point lower than the maximum vulcanization temperature of the rubber composition is formed. You may. By forming such a coating layer, the affinity of the hydrophilic short fibers with water is effectively maintained, and the affinity between the coating layer and the rubber component is good, so that the dispersibility of the short fibers in the rubber component is good. Is improved. In addition, the low melting point resin melts during vulcanization to form a fluidized coating layer, which contributes to the adhesion between the rubber component and the hydrophilic short fibers, resulting in good drainage and durability. The given tire can be easily realized. The thickness of the coating layer may vary depending on the blending amount of the hydrophilic short fibers, 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 for vulcanization of the rubber composition. The maximum temperature of vulcanization means the maximum temperature reached by the rubber composition when the rubber composition is vulcanized. For example, in the case of mold vulcanization, it means the maximum temperature at which the rubber composition reaches from the time when the rubber composition enters the mold to the time when the rubber composition exits the mold and is cooled, and the maximum temperature for vulcanization is, for example,. , It can be measured by embedding a thermocouple in the rubber composition or the like. Although the upper limit of the melting point of the low melting point resin is not particularly limited, it is preferable to select it in consideration of the above points, and generally, it is 10 ° C. or more lower than the maximum vulcanization temperature of the rubber composition. Is preferable, and it is more preferable that the temperature is as low as 20 ° C. or higher. The industrial vulcanization temperature of the rubber composition is generally about 190 ° C. at the maximum, but for example, when the maximum vulcanization temperature is set to this 190 ° C., a low melting point resin The melting point of the above is usually selected in the range of less than 190 ° C., preferably 180 ° C. or lower, and more preferably 170 ° C. or lower.
As the low melting point resin, a polyolefin resin is preferable, and examples thereof include polyethylene, polypropylene, polybutene, polystyrene, ethylene-propylene copolymer, ethylene-methacrylic acid copolymer, ethylene-ethylacrylate copolymer, and ethylene-. Examples thereof include a propylene-diene ternary copolymer, an ethylene-vinyl acetate copolymer, and an ionomer resin thereof.

The staple fibers have an average length of preferably 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 within the above ranges, there is no possibility that the staple fibers are entangled with each other more than necessary, and good dispersibility can be ensured.

The content of the staple fibers 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 of the rubber component. By keeping the content of the hydrophilic staple fibers within the above range, it is possible to strike a good balance between the on-ice performance and the wear resistance of the tire.

(Other ingredients)
In addition to the above-mentioned rubber components, inorganic foaming agents, organic acids, foaming aids, and short fibers, the rubber composition of the present invention includes compounding agents commonly used in the rubber industry, such as fillers, softeners, and stearic acids. An acid, an antioxidant, zinc oxide (zinc white), a vulcanization accelerator, a vulcanizing agent and the like may be appropriately selected and blended within a range that does not impair the object of the present invention. Commercially available products can be preferably used as these compounding agents.

Examples of the filler include carbon black and silica. These fillers may be used alone or in combination of two or more. The content of the filler is not particularly limited, and is preferably in the range of 10 to 150 parts by mass, more preferably 20 to 100 parts by mass with respect to 100 parts by mass of the rubber component.

Examples of the vulcanizing agent include sulfur and the like. The content of the vulcanizing agent is preferably in the range of 0.1 to 10 parts by mass and more preferably in the range of 1 to 4 parts by mass as the sulfur content with respect to 100 parts by mass of the rubber component.

Examples of the vulcanization accelerator include a thiazole-based vulcanization accelerator and a guanidine-based vulcanization accelerator. These vulcanization accelerators may be used alone or in combination of two or more. The content of the vulcanization accelerator is preferably in the range of 0.1 to 5 parts by mass, more preferably in the range of 0.2 to 3 parts by mass with respect to 100 parts by mass of the rubber component.

In the rubber composition of the present invention, for example, using a Banbury mixer, a roll, or the like, an inorganic foaming agent and an organic acid are mixed with a rubber component, and various compounding agents appropriately selected as necessary are mixed and kneaded, and then kneaded. It can be manufactured by heating, extruding, or the like.

The rubber composition of the present invention can be used for various rubber products such as tires. In particular, the rubber composition of the present invention is suitable as a tread rubber for tires.

<Vulcanized rubber>
The vulcanized rubber of the present invention is obtained by vulcanizing the above rubber composition, and is characterized by having a foaming ratio of 1 to 45%. Since the vulcanized rubber of the present invention is obtained by vulcanizing the above rubber composition, it is excellent in productivity, and by applying it to a tire, the performance on ice of the tire can be improved.
When the foaming rate of the vulcanized rubber is 1% or more, the effect of improving the on-ice performance of the tire can be sufficiently obtained, and when the foaming rate of the vulcanized rubber is 45% or less, when applied to the tire, Sufficient wear resistance of the tire can be ensured.

Here, in the present specification, the foaming rate of the vulcanized rubber means the average foaming rate Vs, and specifically, means the value calculated by the following formula (1).
Vs = (ρ ₀ / ρ _1-1 ) × 100 (%) ・ ・ ・ (1)
In the formula (1), ρ ₁ indicates the density (g / cm ³ ) of the vulcanized rubber (foam rubber), and ρ ₀ indicates the density (g / cm ³ ) of the solid phase portion of the vulcanized rubber (foam rubber). show. The density of the vulcanized rubber and the density of the solid phase portion of the vulcanized rubber are calculated from the mass in ethanol and the mass in air.
Further, the foaming rate of the vulcanized rubber can be appropriately changed depending on the type, content and the like of the above-mentioned inorganic foaming agent, organic acid and foaming aid.

The vulcanized rubber of the present invention can be used for various rubber products such as tires. In particular, the vulcanized rubber of the present invention is suitable as a tread rubber for tires.

<Tread rubber for tires>
The tread rubber for a tire of the present invention is characterized by comprising the above-mentioned rubber composition or the above-mentioned vulcanized rubber. Since the tread rubber for a tire of the present invention is made of the above-mentioned rubber composition or vulcanized rubber, it has excellent productivity, and when applied to a tire, the performance on ice of the tire can be improved.
The tire tread rubber of the present invention may be applied to a new tire or a rehabilitated tire.

<Tire>
The tire of the present invention is characterized in that the above-mentioned rubber composition or the above-mentioned vulcanized rubber is provided in a tread portion. Since the tire of the present invention has the above-mentioned rubber composition or vulcanized rubber in the tread portion, the tire has excellent productivity and excellent on-ice performance.
Since the tire of the present invention has excellent on-ice performance, it is particularly useful as a winter tire such as a studless tire.

The tire of the present invention may be obtained by vulcanizing after molding using an unvulcanized rubber composition, depending on the type of tire to be applied, or using a semi-vulcanized rubber that has undergone a preliminary vulcanization step or the like. After molding, it may be obtained by further vulcanization. The tire of the present invention is preferably a pneumatic tire, and as the gas to be filled in the pneumatic tire, an inert gas such as nitrogen, argon, or helium is used in addition to normal or adjusted oxygen partial pressure. Can be used.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

<Preparation and evaluation of rubber composition>
A rubber composition was produced using a normal Banbury mixer with the formulation shown in Table 1, and the workability during the production was evaluated.
Further, the rubber composition was vulcanized according to a conventional method to obtain a vulcanized rubber. The foaming rate of the obtained vulcanized rubber was measured by the following method, and the performance on ice was further evaluated. The results are shown in Table 1.

(1) Workability The workability in producing the rubber composition was evaluated. Specifically, when producing the rubber composition, it was evaluated whether or not the rubber composition adheres to the production equipment such as a roll.
In Table 1, "good" indicates that the rubber composition did not adhere to the manufacturing equipment such as a roll and the workability was good, and "roll adhesion" means that the rubber composition adhered to the roll and the work was performed. Indicates that the sex was bad.

(2) Foaming rate As the foaming rate of vulcanized rubber, the following formula (1):
Vs = (ρ ₀ / ρ _1-1 ) × 100 (%) ・ ・ ・ (1)
The average foaming rate Vs calculated by the above was calculated and evaluated according to the following criteria.
〇 (excellent): When the average foaming rate Vs is 1 to 45% △ (Good): When the average foaming rate Vs is 0.5% or more and less than 1% × ₁ (Poor): Average foaming rate Vs is 0.5 When less than% × ₂ (defective): When the average foaming rate Vs exceeds 45% In formula (1), ρ ₁ indicates the density of vultured rubber (foam rubber) (g / cm ³ ), and ρ ₀ is. The density (g / cm ³ ) of the solid phase portion in vultured rubber (foam rubber) is shown. The density of the vulcanized rubber and the density of the solid phase portion of the vulcanized rubber were calculated from the mass in ethanol and the mass in air.

(3) Performance on ice (ICEμ)
The frictional force generated when a vulcanized rubber having a side of 25 mm and a thickness of 2 mm was pressed against fixed ice at −2 ° C. and reciprocated was detected by a load cell, and a dynamic friction coefficient μ was calculated. The dynamic friction coefficient μ of Comparative Example 1 was set to 100, and the index was displayed. The larger the index value, the larger the dynamic friction coefficient μ, indicating that the performance on ice is good.

* 1 NR: Natural rubber * 2 BR: Butadiene rubber, manufactured by Ube Industries, Ltd., "BR150L"
* 3 Modified BR: Modified butadiene rubber, manufactured by JSR Corporation, "BR500"
* 4 SBR: Styrene-butadiene rubber, manufactured by JSR Corporation, "1500"
* 5 Modified SBR: Modified styrene-butadiene rubber synthesized by the following method.

(Method for synthesizing modified SBR)
To a dry, nitrogen-substituted 800 mL pressure-resistant glass container, add 1,3-butadiene cyclohexane solution and styrene cyclohexane solution to 67.5 g of 1,3-butadiene and 7.5 g of styrene, and add 2,2. -Ditetrahydrofurylpropane 0.6 mmol was added, 0.8 mmol of n-butyllithium was added, and then polymerization was carried out at 50 ° C. for 1.5 hours. To the polymerization reaction system in which the polymerization conversion rate at this time was almost 100%, 0.72 mmol of N, N-bis (trimethylsilyl) -3- [diethoxy (methyl) silyl] propylamine was added as a denaturing agent. The denaturation reaction was carried out at 50 ° C. for 30 minutes. Then, 2 mL of an isopropanol 5% by mass solution of 2,6-di-t-butyl-p-cresol (BHT) was added to stop the reaction, and the mixture was dried according to a conventional method to obtain a modified SBR. As a result of measuring the microstructure of the obtained modified SBR, the amount of bound styrene was 10% by mass, the amount of vinyl bonded in the butadiene portion was 40%, and the peak molecular weight was 200,000.

* 6 Carbon black: "N134" manufactured by Asahi Carbon Co., Ltd.
* 7 Hardened fatty acid: "Stearic acid 50S" manufactured by Shin Nihon Rika Co., Ltd.
* 8 Anti-aging agent: "Nocrack NS-6" manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.
* 9 Vulcanization accelerator: "Sun Cellar CZ" manufactured by Sanshin Chemical Industry Co., Ltd.
* 10 Baking soda: Sodium bicarbonate, manufactured by Eiwa Kasei Kogyo Co., Ltd., "Cerbon FE507"
* 11 Benzoic acid: manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., SP value = 11.93 (cal / cm ³ ) ^1/2
* 12 Malonic acid: manufactured by Kanto Chemical Co., Inc., SP value = 14.03 (cal / cm ³ ) ^1/2
* 13 Citric acid: manufactured by Kanto Chemical Co., Inc., SP value = 16.53 (cal / cm ³ ) ^1/2
* 14 Salicylic acid: manufactured by Kanto Chemical Co., Inc., SP value = 15.53 (cal / cm ³ ) ^1/2
* 15 Urea: "Cell Paste K5" manufactured by Eiwa Kasei Kogyo Co., Ltd.

From Table 1, the rubber composition of the example containing the inorganic foaming agent and the organic acid having an SP value of 9.15 to 16.0 (cal / cm ³ ) ^1/2 has good workability. Also, it can be seen that the performance on ice is excellent.
In Example 4, the workability was good and the on-ice performance (ICEμ) was the same as that of Comparative Example 1, but the foaming rate was improved as compared with Comparative Example 1.
Further, in Comparative Example 3, although the performance on ice was improved as compared with Comparative Example 1, the rubber composition adhered to the roll and the workability was poor, so that the problem of the present application could not be solved.

The rubber composition, vulcanized rubber and tread rubber of the present invention can be used for tires, particularly studless tires and the like. Further, the tire of the present invention is particularly useful as a studless tire.

Claims (13)

A rubber composition containing a rubber component containing a diene-based rubber, an inorganic foaming agent, and an organic acid.
A rubber composition characterized in that the SP value of the organic acid is 9.15 to 16.0 (cal / cm ³ ) ^1/2 . The rubber composition according to claim 1, wherein the inorganic foaming agent is selected from ammonium bicarbonate and sodium bicarbonate. The rubber composition according to claim 2, wherein the inorganic foaming agent is sodium bicarbonate. The rubber composition according to any one of claims 1 to 3, wherein the SP value of the organic acid is 10.5 to 14.3 (cal / cm ³ ) ^1/2 . The rubber composition according to any one of claims 1 to 4, wherein the organic acid has an aromatic ring. The rubber composition according to claim 5, wherein the organic acid is benzoic acid. The rubber composition according to any one of claims 1 to 6, further comprising a foaming aid. The rubber composition according to claim 7, which contains urea as the foaming aid. The rubber composition according to any one of claims 1 to 8, wherein the diene-based rubber contains at least one of a natural rubber and a synthetic diene-based rubber. The rubber composition according to claim 9, wherein the synthetic diene rubber contains at least one selected from the group consisting of isoprene rubber, styrene-butadiene rubber, and butadiene rubber. A vulcanized rubber obtained by vulcanizing the rubber composition according to any one of claims 1 to 10 and having a foaming ratio of 1 to 45%. A tread rubber for a tire, which comprises the rubber composition according to any one of claims 1 to 10 or the vulcanized rubber according to claim 11. A tire comprising the rubber composition according to any one of claims 1 to 10 or the vulcanized rubber according to claim 11 in a tread portion.