JP6155667B2 - Rubber composition - Google Patents

Description

  The present invention relates to a rubber composition, and more particularly, to a rubber composition capable of providing a tire excellent in low heat build-up, wet grip properties, and wear resistance.

  In recent years, due to environmental issues and resource issues, automobile tires are also strongly required to have low heat build-up, and in terms of safety, they have excellent wet grip properties and durability in terms of wear resistance. Is required. A tire obtained from a rubber composition blended with silica is superior in low heat build-up compared to a tire obtained from a rubber composition blended with a commonly used carbon black. Therefore, by using a rubber composition blended with silica, A low fuel consumption tire can be manufactured. However, even if silica is blended with rubber that is usually used, the affinity with silica is poor, so the rubber and silica are easily separated, the processability of the uncrosslinked rubber composition is poor, and the resulting tire has low Exothermic property and wear resistance become insufficient.

  Therefore, a technique has been studied in which a rubber is allowed to have an affinity for silica by reacting a polymer with a modifier. For example, Patent Document 1 discloses a rubber composition obtained by blending silica with a conjugated diene rubber obtained by reacting a polymer chain having an active end with a specific polyorganosiloxane as a modifier. Yes.

International Publication No. 2003/102053

  In the technology described in Patent Document 1, a rubber composition excellent in processability is obtained when silica is blended, and a rubber cross-linked product obtained by crosslinking the rubber composition is excellent in low heat buildup, wet grip properties, and wear resistance. . However, in view of the recent increase in performance required for automobile tires, further improvement in performance is desired.

  In view of such circumstances, an object of the present invention is to provide a rubber composition that can provide a tire excellent in low heat generation property, wet grip property, and wear resistance.

  As a result of intensive studies to achieve the above object, the present inventors have reacted a conjugated diene polymer chain having an active end with a silicon compound having a functional group capable of reacting with the active end. The rubber composition containing a predetermined amount of silica having a predetermined pH with respect to 100 parts by weight of the rubber component containing the modified conjugated diene rubber obtained as described above has found that the above object can be achieved, and has completed the present invention. It was.

That is, according to the present invention, a modified conjugated diene rubber obtained by reacting a conjugated diene polymer chain having an active end with a silicon compound having a functional group capable of reacting with the active end is obtained. Provided is a rubber composition containing 10 to 200 parts by weight of silica having a pH of 8 to 12 and a nitrogen adsorption specific surface area (BET method) of 119 to 300 m ² / g with respect to 100 parts by weight of the rubber component contained. .

Preferably, the silicon compound is a polyorganosiloxane or a hydrocarbyloxysilane compound.
Preferably, the rubber composition further contains a crosslinking agent.

Moreover, according to this invention, the rubber crosslinked material formed by bridge | crosslinking the said rubber composition is provided.
Moreover, according to this invention, the tire which uses the said rubber crosslinked material is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition which can give the tire excellent in low heat build-up property, wet grip property, and abrasion resistance can be provided. Moreover, the rubber | gum crosslinked material formed by bridge | crosslinking this rubber composition and the tire which uses the rubber | gum crosslinked material can be provided.

  The rubber composition of the present invention comprises a modified conjugated diene rubber obtained by reacting a conjugated diene polymer chain having an active end with a silicon compound having a functional group capable of reacting with the active end. It is characterized by containing 10 to 200 parts by weight of silica having a pH of 8 to 12 with respect to 100 parts by weight of the rubber component to be contained.

<Modified conjugated diene rubber>
The modified conjugated diene rubber used in the present invention is obtained by reacting a conjugated diene polymer chain having an active end with a silicon compound having a functional group capable of reacting with the active end.

(Conjugated diene polymer chain having an active end)
Examples of the conjugated diene monomer used to form a conjugated diene polymer chain having an active end include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3- Examples include dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene, and 1,3-hexadiene. Among these, 1,3-butadiene and isoprene are preferable. These conjugated diene monomers can be used alone or in combination of two or more.

  The conjugated diene polymer chain having an active terminus may contain an aromatic vinyl monomer in addition to the conjugated diene monomer. Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2, 4-Diisopropylstyrene, 2,4-dimethylstyrene, 4-t-butylstyrene, 5-t-butyl-2-methylstyrene, vinylnaphthalene, dimethylaminomethylstyrene, dimethylaminoethylstyrene, and the like can be used. Among these, styrene is preferable. These aromatic vinyl monomers can be used alone or in combination of two or more.

  The conjugated diene polymer chain having an active terminal used in the present invention is a homopolymer chain of a conjugated diene monomer or a copolymer chain of a conjugated diene monomer and an aromatic vinyl monomer. It is more preferable that the chain is a copolymer chain of a conjugated diene monomer and an aromatic vinyl monomer, from the viewpoint of better wet grip and wear resistance of the finally obtained tire. The conjugated diene polymer chain having an active end preferably contains 50 to 100% by weight of conjugated diene monomer units, more preferably contains 55 to 90% by weight, and contains 55 to 85% by weight. Particularly preferred, those containing 0 to 50% by weight of aromatic vinyl monomer units are preferred, those containing 10 to 45% by weight are more preferred, and those containing 15 to 45% by weight are particularly preferred.

  The conjugated diene polymer chain having an active terminus used in the present invention is, as long as it does not impair the object of the present invention, optionally other monomers other than the conjugated diene monomer and the aromatic vinyl monomer. May be contained. Examples of other monomers include α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids or acid anhydrides such as acrylic acid, methacrylic acid, and maleic anhydride; methyl methacrylate, acrylic Unsaturated carboxylic acid esters such as ethyl acrylate and butyl acrylate; Non-conjugated dienes such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, 5-ethylidene-2-norbornene; etc. Can be mentioned. These monomers are preferably 10% by weight or less, more preferably 5% by weight or less as monomer units in the conjugated diene polymer chain having an active end.

  The conjugated diene polymer chain having an active end used in the present invention is obtained by polymerizing a conjugated diene monomer, or a conjugated diene monomer and an aromatic vinyl monomer with an initiator in an inert solvent. Is obtained.

  The inert solvent used for the polymerization is not particularly limited as long as it is one that is usually used in solution polymerization and does not inhibit the polymerization reaction. Specific examples include chain aliphatic hydrocarbons such as butane, pentane, hexane, and 2-butene; alicyclic hydrocarbons such as cyclopentane, cyclohexane, and cyclohexene; aromatic carbonization such as benzene, toluene, and xylene. Hydrogen; and the like. The amount of the inert solvent used is such that the monomer concentration is usually 1 to 50% by weight, preferably 10 to 40% by weight.

  The polymerization initiator used for the polymerization is not particularly limited as long as each of these monomers can be polymerized to give a polymer chain having an active end. As a specific example thereof, a polymerization initiator mainly containing an organic alkali metal compound, an organic alkaline earth metal compound, a lanthanum series metal compound, or the like is preferably used. Examples of the organic alkali metal compound include organic monolithium compounds such as n-butyllithium, sec-butyllithium, t-butyllithium, hexyllithium, phenyllithium and stilbenelithium; dilithiomethane, 1,4-dilithiobutane, 1,4 -Organic polyvalent lithium compounds such as dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, 1,3,5-tris (lithiomethyl) benzene; organic sodium compounds such as sodium naphthalene; organic such as potassium naphthalene Potassium compounds; and the like. Examples of the organic alkaline earth metal compound include di-n-butylmagnesium, di-n-hexylmagnesium, diethoxycalcium, calcium distearate, di-t-butoxystrontium, diethoxybarium, and diisopropoxybarium. , Diethyl mercaptobarium, di-t-butoxybarium, diphenoxybarium, diethylaminobarium, barium distearate, diketylbarium and the like. As a polymerization initiator having a lanthanum series metal compound as a main catalyst, for example, a lanthanum series metal comprising a lanthanum series metal such as lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, a carboxylic acid, and a phosphorus-containing organic acid And a polymerization initiator composed of this salt and a cocatalyst such as an alkylaluminum compound, an organoaluminum hydride compound, and an organoaluminum halide compound. Among these polymerization initiators, an organic monolithium compound and an organic polyvalent lithium compound are preferable, an organic monolithium compound is more preferable, and n-butyllithium is particularly preferable. The organic alkali metal compound is used as an organic alkali metal amide compound by previously reacting with a secondary amine such as dibutylamine, dihexylamine, dibenzylamine, pyrrolidine, hexamethyleneimine, and heptamethyleneimine. Also good. These polymerization initiators can be used alone or in combination of two or more.

  Although the usage-amount of a polymerization initiator should just be determined according to the target molecular weight, it is 1-50 mmol normally per 1000g of monomers, Preferably it is the range of 2-20 mmol, More preferably, it is the range of 4-15 mmol.

  The polymerization temperature is usually in the range of −80 to + 150 ° C., preferably 0 to 100 ° C., more preferably 30 to 90 ° C. As the polymerization mode, any of batch mode, continuous mode and the like can be adopted. However, when copolymerizing a conjugated diene monomer and an aromatic vinyl monomer, a conjugated diene monomer unit and an aromatic are used. The batch method is preferable because the randomness of the bond with the vinyl monomer unit can be easily controlled.

  When the conjugated diene polymer chain having an active end is composed of two or more types of monomer units, the bonding mode is, for example, various bonding modes such as block, taper, and random. However, a random binding mode is preferred. By making it random, the tire finally obtained is excellent in low heat build-up.

  In the conjugated diene polymer chain having an active end, only both ends or one end of the polymer chain may be constituted by isoprene unit blocks. When the terminal is constituted by an isoprene unit block, the affinity between the rubber and the silica in the rubber composition is improved, and the finally obtained tire is excellent in low heat buildup and wear resistance. The amount of isoprene used for constituting the terminal isoprene block of the polymer chain is preferably 10 to 200 mol, more preferably 15 to 150 mol, and more preferably 20 to 100 mol with respect to 1 mol of the polymerization initiator. It is particularly preferred.

  In order to adjust the vinyl bond content in the conjugated diene monomer unit in the conjugated diene polymer chain having an active end, it is preferable to add a polar compound to the inert organic solvent during the polymerization. Examples of the polar compound include ether compounds such as dibutyl ether and tetrahydrofuran; tertiary amines such as tetramethylethylenediamine; alkali metal alkoxides; phosphine compounds. Among these, ether compounds and tertiary amines are preferable, tertiary amines are more preferable, and tetramethylethylenediamine is particularly preferable. These polar compounds can be used alone or in combination of two or more. The amount of the polar compound used may be determined according to the target vinyl bond content, and is usually 0.001 to 10 mol, preferably 0.005 to 8 mol, more preferably 0 to 1 mol of the polymerization initiator. The range is from 0.01 to 5 mol. When the amount of the polar compound used is in the above range, the vinyl bond content in the conjugated diene monomer unit can be easily adjusted, and problems due to deactivation of the polymerization initiator hardly occur.

  The vinyl bond content in the conjugated diene monomer unit in the conjugated diene polymer chain having an active terminal used in the present invention is preferably 0 to 80% by weight, more preferably 5 to 70% by weight. Particularly preferably, it is 10 to 65% by weight. When the vinyl bond amount is in the above range, the tire finally obtained is excellent in low heat buildup.

  The peak top molecular weight detected by gel permeation chromatography of the conjugated diene polymer chain having an active end used in the present invention is preferably 100,000 to 1,000,000 as a value in terms of polystyrene. 150,000 to 850,000, more preferably 200,000 to 700,000. In addition, when multiple peaks of the conjugated diene polymer chain are observed, the peak top molecular weight of the peak having the smallest molecular weight derived from the conjugated diene polymer chain detected by gel permeation chromatography has an active end. The peak top molecular weight of the conjugated diene polymer chain is taken. When the peak top molecular weight of the conjugated diene polymer chain having an active end is in the above range, the finally obtained tire is excellent in low heat buildup.

  The molecular weight distribution represented by the ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the conjugated diene polymer chain having an active end used in the present invention is preferably 1.0 to 1.5, more preferably 1.0 to 1.4, particularly preferably 1.0 to 1.3. When the molecular weight distribution value (Mw / Mn) is in the above range, the low heat buildup of the finally obtained tire is excellent.

(Silicon compound)
The silicon compound used in the present invention (hereinafter also referred to as a modifier) has a functional group capable of reacting with the active terminal of the conjugated diene polymer chain.

  The functional group capable of reacting with the active end of the conjugated diene polymer chain is not particularly limited as long as it can react with the active end, but from the viewpoint of reactivity with the active end, a halogen atom, 2- A pyrrolidonyl group, a vinyl group, an alkoxy group, an amino group or an epoxy group is preferred, a 2-pyrrolidonyl group, an epoxy group and an alkoxy group are more preferred, and an epoxy group is particularly preferred.

（上記一般式（１）中、Ｒ^１〜Ｒ^８は、それぞれ独立して、炭素数１〜６のアルキル基、または炭素数６〜１２のアリール基である。Ｘ^１およびＸ^４は、それぞれ独立して、共役ジエン系重合体鎖の活性末端と反応可能な官能基、炭素数１〜６のアルキル基、または炭素数６〜１２のアリール基である。Ｘ^２は、共役ジエン系重合体鎖の活性末端と反応可能な官能基であり、複数あるＸ^２は互いに同一であっても相違していてもよい。Ｘ^３は、２〜２０のアルキレングリコールの繰返し単位を含有する基であり、Ｘ^３が複数あるときは、それらは互いに同一であっても相違していてもよい。ｍは３〜２００の整数、ｎは０〜２００の整数、ｋは０〜２００の整数である。） Examples of the silicon compound used in the present invention include polyorganosiloxane and hydrocarbyloxysilane compounds. The polyorganosiloxane is not particularly limited as long as it has a functional group capable of reacting with the active terminal of the conjugated diene polymer chain, and specific examples thereof include polyorganosiloxane represented by the following general formula (1). And so on. The hydrocarbyloxysilane compound is not particularly limited as long as it has a functional group capable of reacting with the active end of the conjugated diene polymer chain. Specific examples thereof are represented by the following general formula (2). Hydrocarbyloxysilane compounds; tetraalkoxysilane compounds such as tetramethoxysilane and tetraethoxysilane; hexaalkoxysilane compounds such as bis (trimethoxysilyl) ethane and bis (trimethoxysilyl) hexane; alkylalkoxysilanes such as methyltriethoxysilane Compounds; vinyl alkoxysilane compounds such as vinyltrimethoxysilane; arylalkoxysilane compounds such as phenyltrimethoxysilane; halogenoalkoxysilane compounds such as triethoxychlorosilane; 3-glycidoxyethyltri Epoxy group-containing alkoxysilane compounds such as toxisilane, 3-glycidoxybutylpropyltrimethoxysilane, bis (3-glycidoxypropyl) dimethoxysilane; sulfur-containing alkoxy such as bis (3- (triethoxysilyl) propyl) disulfide Silane compounds; amino group-containing alkoxysilane compounds such as bis (3-trimethoxysilylpropyl) methylamine; isocyanate group-containing alkoxysilane compounds such as tris (3-trimethoxysilylpropyl) isocyanurate; In addition, examples of the silicon compound used in the present invention include tetrahalogenated silane compounds such as tetrachlorosilane. Among these, a polyorganosiloxane represented by the following general formula (1) and a hydrocarbyloxysilane compound represented by the following general formula (2) are preferable. In particular, by using a polyorganosiloxane represented by the following general formula (1), the tire finally obtained is excellent in low heat build-up, wet grip and wear resistance.

(In the general formula (1), R ^{1 to} R ⁸ are each independently an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. X ¹ and X ⁴ are respectively Independently, it is a functional group capable of reacting with the active terminal of the conjugated diene polymer chain, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, X ² being a conjugated diene polymer A plurality of X ² may be the same or different from each other, and X ³ is a group containing 2 to 20 alkylene glycol repeating units. , X ³ may be the same or different from each other, m is an integer of 3 to 200, n is an integer of 0 to 200, and k is an integer of 0 to 200. )

（上記一般式（２）中、Ｒ^９は、炭素数１〜１２のアルキレン基であり、Ｒ^９が複数あるときは、それらは互いに同一であっても相違していてもよい。Ｒ^１０〜Ｒ^１８は、それぞれ独立して、炭素数１〜６のアルキル基、または炭素数６〜１２のアリール基である。ｒは１〜１０の整数である。）

In (above Formula (2), ^{R 9} is an alkylene group having 1 to 12 carbon atoms, ^{when R 9} there are multiple, they mutually identical a good ^{.R 10} be different even ~ R ¹⁸ is each independently an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and r is an integer of 1 to 10.)

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

In the polyorganosiloxane represented by the general formula (1), the functional group capable of reacting with the active terminal of the conjugated diene polymer chain constituting X ¹ , X ² , and X ⁴ has 1 to 5 carbon atoms. A C4-C12 group containing an alkoxy group, a hydrocarbon group containing a 2-pyrrolidonyl group, and an epoxy group is preferred, and a C4-C12 group containing an epoxy group is more preferred.

  Examples of the alkoxy group having 1 to 5 carbon atoms include methoxy group, ethoxy group, propoxy group, isopropoxy group, and butoxy group. Among these, a methoxy group and an ethoxy group are preferable from the viewpoint of reactivity with the active terminal of the conjugated diene polymer chain.

  As a hydrocarbon group containing 2-pyrrolidonyl group, what is represented by following General formula (3) is mentioned, for example.

（上記一般式（３）中、ｊは２〜１０の整数であり、２であることが好ましい。）

(In the general formula (3), j is an integer of 2 to 10, and is preferably 2.)

As a C4-C12 group containing an epoxy group, what is represented by following General formula (4) is mentioned, for example.
-Z ¹ -Z ² -E (4)
(In the general formula (4), Z ¹ is an alkylene group having 1 to 10 carbon atoms or an alkylarylene group, Z ² is a methylene group, a sulfur atom, or an oxygen atom, and E is a carbon having an epoxy group. A hydrocarbon group having a number of 2 to 10. Among these, those in which Z ² is an oxygen atom are preferable, those in which Z ² is an oxygen atom and E is a glycidyl group are more preferable, and Z ¹ is Particularly preferred is an alkylene group having 3 carbon atoms, Z ² is an oxygen atom, and E is a glycidyl group.

In the polyorganosiloxane represented by the general formula (1), R ^{1 to} R ⁸ are preferably an alkyl group having 1 to 6 carbon atoms, and X ¹ and X ⁴ include among them, preferably an alkyl group having 1 to 6 carbon atoms, and X ^2, among the above-mentioned, is preferably a group having 4 to 12 carbon atoms containing an epoxy group.

（上記一般式（５）中、ｔは２〜２０の整数であり、Ｐは炭素数２〜１０のアルキレン基またはアルキルアリーレン基であり、Ｒは、水素原子またはメチル基であり、複数あるＲは互いに同一であっても相違していてもよい。Ｑは炭素数１〜１０のアルコキシ基またはアリーロキシ基である。これらの中でも、ｔが２〜８の整数であり、Ｐが炭素数３のアルキレン基であり、Ｒが水素原子であり、かつＱがメトキシ基であるものが好ましい。 In the polyorganosiloxane represented by the general formula (1), examples of the group containing a repeating unit of X ³ , that is, 2 to 20 alkylene glycol, include those represented by the following general formula (5). .

(In the general formula (5), t is an integer of 2 to 20, P is an alkylene group or alkylarylene group having 2 to 10 carbon atoms, R is a hydrogen atom or a methyl group, and a plurality of R May be the same or different from each other, Q is an alkoxy group having 1 to 10 carbon atoms or an aryloxy group, among which t is an integer of 2 to 8 and P is 3 carbon atoms. An alkylene group, R is a hydrogen atom, and Q is a methoxy group is preferable.

  In the polyorganosiloxane represented by the general formula (1), m is an integer of 3 to 200, preferably 3 to 150, more preferably 3 to 120. If the number m is in the above range, the tire finally obtained is excellent in low heat buildup.

  In the polyorganosiloxane represented by the general formula (1), n is an integer of 0 to 200, preferably 0 to 150, more preferably 0 to 120. k is an integer of 0 to 200, preferably 0 to 150, more preferably 0 to 120. The total number of m, n, and k is preferably 3 to 400, more preferably 3 to 300, and particularly preferably 3 to 250. If the total number of m, n, and k is too large, the viscosity of the polymerization solution during the reaction may become too high, making it difficult to produce a modified conjugated diene rubber.

  In the polyorganosiloxane represented by the general formula (1), when the epoxy group in the polyorganosiloxane reacts with the active end of the conjugated diene polymer chain, at least a part of the epoxy group in the polyorganosiloxane is opened. By ringing, it is considered that a bond between the carbon atom of the portion where the epoxy group is opened and the active end of the conjugated diene polymer chain is formed. Further, when the alkoxy group in the polyorganosiloxane reacts with the active terminal of the conjugated diene polymer chain, the silicon atom contained in the polyorganosiloxane is removed by elimination of at least a part of the alkoxy group in the polyorganosiloxane. It is considered that a bond is formed with the active end of the conjugated diene polymer chain. When the 2-pyrrolidonyl group in the polyorganosiloxane reacts with the active end of the conjugated diene polymer chain, the carbon-oxygen bond of the carbonyl group constituting at least a part of the 2-pyrrolidonyl group in the polyorganosiloxane is present. Cleavage is considered to form a bond between the carbon atom and the conjugated diene polymer chain.

  In the hydrocarbyloxysilane compound represented by the general formula (2), the alkyl group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms are those described for the polyorganosiloxane of the general formula (1). It is the same.

  In the hydrocarbyloxysilane compound represented by the general formula (2), examples of the alkylene group having 1 to 12 carbon atoms include a methylene group, an ethylene group, and a propylene group. Among these, a propylene group is preferable.

  Specific examples of the hydrocarbyloxysilane compound represented by the general formula (2) include N, N-bis (trimethylsilyl) -3-aminopropyltrimethoxysilane, N, N-bis (trimethylsilyl) -3-aminopropyltri Examples include ethoxysilane, N, N-bis (trimethylsilyl) aminoethyltrimethoxysilane, and N, N-bis (trimethylsilyl) aminoethyltriethoxysilane.

  The amount of the modifier used is such that the molar amount of the functional group capable of reacting with the active terminal of the conjugated diene polymer chain is 0.01 to 10 mol with respect to 1 mol of the polymerization initiator used in the polymerization reaction. It is more preferable that the amount is 0.05 to 8 mol, and it is particularly preferable that the amount is 0.1 to 4 mol. When the amount of the modifier used is within the above range, the tire finally obtained is excellent in low heat buildup, wet grip properties, and wear resistance. These modifiers can be used alone or in combination of two or more.

  The modified conjugated diene rubber used in the present invention preferably contains 1 to 100% by weight, preferably 10 to 100% by weight, of a modified polymer obtained by reacting with a modifier in the modified conjugated diene rubber. Is more preferable, and 50 to 100% by weight is particularly preferable. When the content of the modified polymer in the modified conjugated diene rubber is within the above range, the tire finally obtained is excellent in low heat build-up, wet grip and wear resistance.

  The modified conjugated diene rubber used in the present invention, in addition to modifying the conjugated diene polymer chain having an active end by using the above-described modifier, is a part of the active end of the conjugated diene polymer chain. As long as the effects of the present invention are not impaired, the coupling agent may be added to the polymerization system for coupling to contain a coupling polymer.

  Examples of the coupling agent used at this time include tin tetrachloride; hexachlorodisilane, bis (trichlorosilyl) methane, 1,2-bis (trichlorosilyl) ethane, 1,3-bis (trichlorosilyl) propane, 1, And halogenated silicon compounds such as 4-bis (trichlorosilyl) butane, 1,5-bis (trichlorosilyl) pentane, and 1,6-bis (trichlorosilyl) hexane. By using a coupling agent in combination, a high molecular weight coupling polymer can be produced, and as a result, the finally obtained tire is excellent in steering stability. These coupling agents may be used individually by 1 type, and may be used in combination of 2 or more type.

  As a method of reacting a conjugated diene polymer chain having an active end with a modifier or a coupling agent, a solution containing a conjugated diene polymer chain having an active end, a modifier or a coupling agent is used. Although it is not particularly limited as long as it can be mixed, a modifier or a coupling agent is added to a solution containing a conjugated diene polymer chain having an active end from the viewpoint of favorably controlling a modification reaction or a coupling reaction. The method is preferred. In that case, it is more preferable that the modifier or the coupling agent is dissolved in an inert solvent and added to the polymerization system. The solution concentration is preferably in the range of 1 to 50% by weight.

  There is no particular limitation on the timing of adding a modifier or the like to a solution containing a conjugated diene polymer chain having an active end, but the polymerization reaction is not completed and a conjugated diene polymer chain having an active end is contained. The solution containing the monomer, more specifically, the solution containing the conjugated diene polymer chain having an active end is 100 ppm or more, more preferably 300 to 50,000 ppm. It is desirable to add a denaturing agent or the like to this solution while containing the body. By adding modifiers in this way, side reactions between conjugated diene polymer chains having active ends and impurities contained in the polymerization system can be suppressed, and the reaction can be controlled well. It becomes.

  As conditions for reacting a modifier or the like with a conjugated diene polymer chain having an active end, the reaction temperature is usually in the range of 0 to 100 ° C., preferably 30 to 90 ° C., and each reaction time. Is usually in the range of 1 minute to 120 minutes, preferably 2 minutes to 60 minutes.

  The order of addition in the case of adding both the modifier and the coupling agent to the solution containing the conjugated diene polymer chain having an active end is not particularly limited, and either one may be added first. However, it is preferable to add the coupling agent before the modifier. By performing in this order, the coupling polymer can be reliably generated.

  After reacting the above-mentioned modifier and the coupling agent to be added as desired with the active end of the conjugated diene polymer chain, a polymerization terminator such as methanol or alcohol such as isopropanol or water is not added. It is preferred to deactivate the active end of the reaction.

  After deactivating the active end of the conjugated diene polymer chain, polymerize anti-aging agents such as phenol stabilizers, phosphorus stabilizers, sulfur stabilizers, crumbs, and scale inhibitors as desired. After adding to the solution, the polymerization solvent is separated from the polymerization solution by direct drying or steam stripping and the modified conjugated diene rubber is recovered. Before separating the polymerization solvent from the polymerization solution, an extending oil may be mixed into the polymerization solution, and the modified conjugated diene rubber may be recovered as an oil-extended rubber.

  Examples of the extending oil used when the modified conjugated diene rubber is recovered as an oil extended rubber include paraffinic, aromatic and naphthenic petroleum softeners, plant softeners, and fatty acids. When using a petroleum softener, it is preferable that the content of polycyclic aromatics extracted by the method of IP346 (the inspection method of THE INSTITUTE PETROLEUM in the UK) is less than 3%. When using the extender oil, the amount used is usually 5 to 100 parts by weight, preferably 10 to 60 parts by weight, and more preferably 20 to 50 parts by weight with respect to 100 parts by weight of the modified conjugated diene rubber. .

  The weight average molecular weight of the modified conjugated diene rubber used in the present invention is preferably 100,000 to 3,000,000, preferably 150,000 to 2,500,000 as a value measured by gel permeation chromatography in terms of polystyrene. 000 is more preferable, and 200,000 to 2,000,000 is particularly preferable. When the weight average molecular weight of the modified conjugated diene rubber is within the above range, the silica can be easily blended into the modified conjugated diene rubber, the rubber composition has excellent processability, and the resulting tire has low heat build-up. It will be excellent.

  The molecular weight distribution represented by the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the modified conjugated diene rubber used in the present invention is 1.1 to 3.0. Preferably, it is 1.2 to 2.5, more preferably 1.2 to 2.2. If the molecular weight distribution value (Mw / Mn) of the modified conjugated diene rubber is within the above range, the resulting tire will be excellent in low heat buildup.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the modified conjugated diene rubber used in the present invention is preferably 20 to 100, more preferably 30 to 90, and particularly preferably 35 to 80. . When the modified conjugated diene rubber is an oil-extended rubber, the Mooney viscosity of the oil-extended rubber is preferably in the above range.

  The modified conjugated diene rubber thus obtained can be suitably used for various applications after adding compounding agents such as a filler and a crosslinking agent. In particular, when silica having a pH of 8 to 12 is blended as a filler, a rubber composition that is suitably used for obtaining a tire excellent in low heat generation, wet grip properties, and wear resistance is provided.

<Rubber composition>
The rubber composition of the present invention can be obtained by blending 10 to 200 parts by weight of silica having a pH of 8 to 12 with respect to 100 parts by weight of the rubber component containing the modified conjugated diene rubber described above.

  The rubber composition of the present invention may contain other rubbers other than the above-described modified conjugated diene rubber. Other rubbers are not particularly limited. For example, natural rubber, polyisoprene rubber, emulsion polymerization styrene-butadiene copolymer rubber, solution polymerization styrene-butadiene copolymer rubber, polybutadiene rubber (high cis-BR, low cis BR) It may also be a polybutadiene rubber containing crystal fibers made of 1,2-polybutadiene polymer), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer. Of the rubber, acrylonitrile-butadiene copolymer rubber, acrylonitrile-styrene-butadiene copolymer rubber, etc., those other than the above-mentioned modified conjugated diene rubbers. Among these, natural rubber, polyisoprene rubber, polybutadiene rubber, and solution-polymerized styrene-butadiene copolymer rubber are preferable. The other rubbers can be used alone or in combination of two or more.

  In the rubber composition of the present invention, the modified conjugated diene rubber described above preferably occupies 10 to 100% by weight, more preferably 20 to 100% by weight, and 50 to 100% by weight in the rubber component. It is particularly preferred to occupy. By including the modified conjugated diene rubber in the rubber component at such a ratio, it is possible to obtain a rubber composition suitably used for obtaining a tire excellent in low heat buildup, wet grip properties, and wear resistance. it can.

  The rubber composition of the present invention contains 10 to 200 parts by weight of silica having a pH of 8 to 12 with respect to 100 parts by weight of the rubber component, preferably 20 to 120 parts by weight, More preferably, it contains 100 parts by weight. Further, the pH of silica is more preferably 8 to 11.5, and particularly preferably 9 to 11. When the silica pH and the silica content are in the above ranges, a rubber composition suitably used for obtaining a tire excellent in low heat build-up, wet grip properties and wear resistance can be obtained. The pH of silica is the value of pH (4% pH) when silica is dispersed in water to make a 4% aqueous dispersion.

  Specific examples of silica include dry process white carbon, wet process white carbon, colloidal silica, and precipitated silica. Among these, wet method white carbon mainly containing hydrous silicic acid is preferable. Alternatively, a carbon-silica dual phase filler in which silica is supported on the carbon black surface may be used. These silicas can be used alone or in combination of two or more.

Is (measured by the BET method according to ASTM D3037-81) nitrogen adsorption specific surface area of silica used is preferably 50 to 300 m ² / g, more preferably 80~250m ² / g, particularly preferably 100~220m ² / g. When the nitrogen adsorption specific surface area of silica is in this range, the tire finally obtained is particularly excellent in low heat buildup.

  From the viewpoint of further improving the low heat buildup of the tire, it is preferable to further add a silane coupling agent to the rubber composition of the present invention. Examples of the silane coupling agent include vinyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, 3-octathio- 1-propyl-triethoxysilane, bis (3- (triethoxysilyl) propyl) disulfide, bis (3- (triethoxysilyl) propyl) tetrasulfide, γ-trimethoxysilylpropyldimethylthiocarbamyl tetrasulfide, and γ -Trimethoxysilylpropyl benzothiazyl tetrasulfide etc. can be mentioned. Among these, from the viewpoint of avoiding scorch during kneading, those having 4 or less sulfur in one molecule are preferable. These silane coupling agents can be used alone or in combination of two or more. The amount of the silane coupling agent is preferably 0.1 to 30 parts by weight, more preferably 1 to 15 parts by weight, based on 100 parts by weight of silica.

  The rubber composition of the present invention may further contain carbon black such as furnace black, acetylene black, thermal black, channel black and graphite. When carbon black is used, it is preferable to use furnace black. Specific examples thereof include SAF, ISAF, ISAF-HS, ISAF-LS, IISAF-HS, HAF, HAF-HS, HAF-LS, T-HS, Examples include T-NS, MAF, N234, and FEF. These carbon blacks can be used alone or in combination of two or more. The blending amount of carbon black is preferably 120 parts by weight or less with respect to 100 parts by weight of the rubber component, and the total amount of silica and carbon black is preferably 10 to 200 parts by weight with respect to 100 parts by weight of the rubber component. 20-120 weight part is more preferable, and 30-100 weight part is especially preferable.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 5 to 200 m ² / g, more preferably 20 to 150 m ² / g, particularly preferably 40 to 130 m ² / g, and dibutyl phthalate (DBP). The amount of adsorption is preferably 5 to 200 ml / 100 g, more preferably 50 to 160 ml / 100 g, and particularly preferably 70 to 130 ml / 100 g. When the nitrogen adsorption specific surface area of carbon black is in the above range, a rubber composition having good moldability and a tire excellent in low heat build-up can be obtained.

  The method of adding a filler such as silica and carbon black to the rubber composition is not particularly limited, and a method of adding to a solid rubber and kneading (dry kneading method), and a method of adding to a rubber solution and solidifying and drying. Although a method (wet kneading method) can be applied, a method of blending a filler such as silica with a solid rubber is preferable.

  The rubber composition of the present invention preferably further contains a crosslinking agent. Examples of the crosslinking agent include sulfur-containing compounds such as sulfur and sulfur halides, organic peroxides, quinonedioximes, organic polyvalent amine compounds, and alkylphenol resins having a methylol group. Among these, sulfur is preferably used. The amount of the crosslinking agent is preferably 0.1 to 15 parts by weight, more preferably 0.5 to 5 parts by weight, and particularly preferably 1 to 4 parts by weight with respect to 100 parts by weight of the rubber component. When the blending amount of the cross-linking agent is within the above range, the cross-linking is sufficiently performed and the resulting rubber cross-linked product has excellent mechanical properties.

  When sulfur or a sulfur-containing compound is used as the crosslinking agent, it is preferable to use a crosslinking accelerator and a crosslinking activator in combination. Examples of crosslinking accelerators include sulfenamide compounds; guanidine compounds; thiourea compounds; thiazole compounds; thiuram compounds; dithiocarbamate compounds; xanthogenic compounds; Can do. Among these, those containing a sulfenamide-based crosslinking accelerator are preferable. These crosslinking accelerators are used alone or in combination of two or more. The blending amount of the crosslinking accelerator is preferably 0.05 to 15 parts by weight, more preferably 0.5 to 10 parts by weight, and particularly preferably 1 to 5 parts by weight with respect to 100 parts by weight of the rubber component.

  Examples of the crosslinking activator include zinc oxide; higher fatty acids such as stearic acid; and the like. These crosslinking activators are used alone or in combination of two or more. The amount of the crosslinking activator is preferably 0.05 to 20 parts by weight, more preferably 0.5 to 15 parts by weight with respect to 100 parts by weight of the rubber component. When the blending amount of the crosslinking accelerator and the crosslinking activator is within the above range, the crosslinking is sufficiently performed, and the resulting rubber cross-linked product has excellent mechanical properties.

  In addition to the components described above, the rubber composition of the present invention includes an anti-aging agent, an anti-scorch agent, an activator, a process oil, a plasticizer, a lubricant, a filler (excluding silica and carbon black described above), and tackifying. A compounding agent usually used in the rubber processing field, such as an agent;

  In order to obtain the rubber composition of the present invention, each component may be kneaded according to a conventional method. For example, a compounding agent excluding a crosslinking agent and a crosslinking accelerator and a rubber component are kneaded, and then the kneaded product is mixed with a crosslinking agent and a crosslinking accelerator to obtain a desired rubber composition. The kneading temperature of the compounding agent excluding the crosslinking agent and the crosslinking accelerator and the rubber component is preferably 80 to 200 ° C., more preferably 100 to 180 ° C., and the kneading time is preferably 30 seconds to 30 minutes. is there. The kneaded product, the crosslinking agent, and the crosslinking accelerator are usually mixed after cooling to 100 ° C. or lower, preferably 80 ° C. or lower.

  The rubber composition thus obtained can be used for a tire by crosslinking, for example.

<Rubber cross-linked product>
The rubber cross-linked product of the present invention is formed by cross-linking the rubber composition of the present invention containing a cross-linking agent. The method for crosslinking and molding the rubber composition of the present invention is not particularly limited, and may be selected according to the shape and size of the crosslinked product. The mold may be filled with a rubber composition containing a crosslinking agent and heated to be crosslinked at the same time as the molding. The rubber composition containing the crosslinking agent may be preliminarily molded and then heated to be crosslinked. May be. The temperature during molding is preferably 20 to 140 ° C, more preferably 40 to 130 ° C. The crosslinking temperature is preferably 120 to 200 ° C, more preferably 140 to 180 ° C, and the crosslinking time is usually 1 to 120 minutes.

  The rubber cross-linked product of the present invention is used for rubber products such as tires, hoses, window frames, belts, shoe soles, anti-vibration rubbers, automobile parts, and seismic isolation rubbers. Among these, the rubber cross-linked product of the present invention is excellent in low exothermic property, wet grip property, and wear resistance, and is therefore suitably used for tire applications. The rubber cross-linked product of the present invention can be used in various parts of a tire such as a tread, a carcass, a sidewall, and a bead part in various tires such as an all-season tire, a high-performance tire, and a studless tire. Particularly, since it is excellent in low heat generation property, it is particularly suitably used as a tread for a low fuel consumption tire.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples. In the examples, “parts” and “%” are based on weight unless otherwise specified.

Various physical property tests in Examples and Comparative Examples were performed according to the following methods.

(Weight average molecular weight and molecular weight distribution)
The weight average molecular weight and the molecular weight distribution were obtained based on the chart obtained by gel permeation chromatography based on a polystyrene-based molecular weight. The specific measurement conditions for gel permeation chromatography are as follows.

Measuring instrument: HLC-8020 (manufactured by Tosoh Corporation)
Column: GMH-HR-H (manufactured by Tosoh Corporation) connected in series Detector: Differential refractometer RI-8020 (manufactured by Tosoh Corporation)
Eluent: Tetrahydrofuran Column temperature: 40 ° C

(Styrene content and vinyl bond content)
Styrene content and vinyl bond content were measured by ¹ H-NMR.

(Mooney viscosity (ML _{1 + 4} , 100 ° C))
The Mooney viscosity was measured using a Mooney viscometer (manufactured by Shimadzu Corporation) in accordance with JIS K6300.

(Wet grip)
Wet grip properties are 50 mm long, 12.7 mm wide and 2 mm thick test pieces made of a rubber cross-linked product, using ARES-G2 manufactured by TA Instruments Inc., dynamic strain 0.5%, Tanδ at 0 ° C. was measured at 10 Hz. About this characteristic, the comparative example 1 mentioned later was made into the reference | standard sample, and it showed with the index | exponent which makes the measured value of the comparative example 1 100. The larger this index, the better the wet grip property when the rubber cross-linked product is used for a tire. Moreover, in order to express the effect by the pH of silica, among rubber compositions using the same rubber, a rubber composition using a nip seal AQ having a silica pH of 6.1 was used as a reference sample, and Comparative Examples 1 to 3 were used. An index with a measured value of 100 as 100 was also shown (Examples 1 and 2 for Comparative Example 1 and Comparative Example 4, Comparative Example 5 for Comparative Example 2 and Comparative Example 6 for Comparative Example 3). And an index of 7 was shown).

(Low heat generation)
The low exothermic property is a test piece having a length of 50 mm, a width of 12.7 mm, and a thickness of 2 mm made of a crosslinked rubber, using ARES-G2 manufactured by TA Instruments Inc., with a dynamic strain of 2.5%, Tanδ at 60 ° C. was measured under the condition of 10 Hz. About this characteristic, the comparative example 1 mentioned later was made into the reference | standard sample, and it showed with the index | exponent which makes the measured value of the comparative example 1 100. The smaller the index, the better the low heat buildup when the rubber cross-linked product is used for a tire. Moreover, in order to express the effect by the pH of silica, among rubber compositions using the same rubber, a rubber composition using a nip seal AQ having a silica pH of 6.1 was used as a reference sample, and Comparative Examples 1 to 3 were used. An index with a measured value of 100 as 100 was also shown (Examples 1 and 2 for Comparative Example 1 and Comparative Example 4, Comparative Example 5 for Comparative Example 2 and Comparative Example 6 for Comparative Example 3). And an index of 7 was shown).

(Abrasion resistance)
Abrasion resistance was measured using a FPS abrasion tester manufactured by Ueshima Seisakusho Co., Ltd. with a test piece having an outer diameter of 50 mm, an inner diameter of 15 mm, and a thickness of 10 mm made of a rubber cross-linked product at a load of 1 kgf and a slip ratio of 15%. About this characteristic, the comparative example 1 mentioned later was made into the reference | standard sample, and it showed with the index | exponent which makes the measured value of the comparative example 1 100. The larger this index is, the better the abrasion resistance is when a rubber cross-linked product is used in a tire. Moreover, in order to express the effect by the pH of silica, among rubber compositions using the same rubber, a rubber composition using a nip seal AQ having a silica pH of 6.1 was used as a reference sample, and Comparative Examples 1 to 3 were used. An index with a measured value of 100 as 100 was also shown (Examples 1 and 2 for Comparative Example 1 and Comparative Example 4, Comparative Example 5 for Comparative Example 2 and Comparative Example 6 for Comparative Example 3). And an index of 7 was shown).

[Production Example 1: Preparation of Modified Conjugated Diene Rubber I]
In an autoclave equipped with a stirrer, 800 g of cyclohexane, 0.85 mmol of tetramethylethylenediamine, 94.8 g of 1,3-butadiene, and 25.2 g of styrene were charged in a nitrogen atmosphere, and then 0.71 mmol of n-butyllithium was added, and 60 ° C. The polymerization was started. Subsequently, after confirming that the polymerization conversion rate was in the range of 95% to 100%, 0.08 mmol of tin tetrachloride was added and reacted for 30 minutes. Next, the polyorganosiloxane A represented by the following formula (6) was added to a 20 weight percent concentration xylene solution so as to have an epoxy group content corresponding to 0.33 moles of n-butyllithium used. It was added in the state and allowed to react for 30 minutes. Thereafter, as a polymerization terminator, an amount of methanol corresponding to twice the mole of n-butyllithium used was added to obtain a solution containing the modified conjugated diene rubber I. Irganox 1520L (manufactured by Ciba Specialty Chemicals) as an anti-aging agent was added to this solution in an amount of 0.15 parts per 100 parts of the modified conjugated diene rubber I, and the solvent was removed by steam stripping. Vacuum-dried at 60 ° C. for 24 hours to obtain a solid modified conjugated diene rubber I.

  The resulting modified conjugated diene rubber I had an overall Mn of 336,000, Mw of 481,000, and molecular weight distribution (Mw / Mn) of 1.43 in GPC measurement. The modified conjugated diene rubber I had a styrene content of 21.2% by weight and a vinyl bond content in the butadiene monomer unit of 62.6% by weight.

[Production Example 2: Preparation of modified conjugated diene rubber II]
An autoclave equipped with a stirrer was charged with 800 g of cyclohexane, 0.96 mmol of tetramethylethylenediamine, 94.8 g of 1,3-butadiene, and 25.2 g of styrene under a nitrogen atmosphere, and then 0.80 mmol of n-butyllithium was added, The polymerization was started. Subsequently, after confirming that the polymerization conversion rate was in the range of 95% to 100%, 0.04 mmol of tin tetrachloride was added and reacted for 30 minutes. Next, 0.692 mmol of N-phenylpyrrolidone was added and reacted for 30 minutes. Thereafter, as a polymerization terminator, an amount of methanol corresponding to twice the mole of n-butyllithium used was added to obtain a solution containing the modified conjugated diene rubber II. Irganox 1520L (manufactured by Ciba Specialty Chemicals) as an anti-aging agent was added to this solution in an amount of 0.15 parts per 100 parts of the modified conjugated diene rubber II, and the solvent was removed by steam stripping. Vacuum-dried at 60 ° C. for 24 hours to obtain a solid modified conjugated diene rubber II.

  The resulting modified conjugated diene rubber II had an overall Mn of 287,000, Mw of 400,000, and a molecular weight distribution (Mw / Mn) of 1.4 in GPC measurement. The modified conjugated diene rubber II had a styrene content of 20.8% by weight and a vinyl bond content in the butadiene monomer unit of 62.3% by weight.

Example 1
100 parts of the modified conjugated diene rubber I obtained in Production Example 1 was masticated using a Banbury mixer with a capacity of 250 ml. Next, 43 parts of silica 1 (trade name “Nip Seal NA”, manufactured by Tosoh Silica Co., Ltd., pH = 11 of 4% aqueous dispersion, nitrogen adsorption specific surface area (BET method): 160 m ² / g), silane coupling agent ( 4.6 parts of bis (3- (triethoxysilyl) propyl) tetrasulfide, trade name “Si69” (manufactured by Degussa), and 15 parts of process oil (trade name “Fukor Eramic 30”, manufactured by Nippon Oil Corporation) The mixture was added and kneaded for 1.5 minutes starting at 110 ° C. To this kneaded product, 22 parts of silica 1 (trade name “Nip Seal NA”, manufactured by Tosoh Silica Co., Ltd., pH = 11 of 4% aqueous dispersion, nitrogen adsorption specific surface area (BET method): 160 m ² / g), zinc oxide (Zinc flower No. 1) 2.5 parts, stearic acid (trade name “Tubeki bead stearate”, manufactured by NOF Corporation), and anti-aging agent (N-phenyl-N ′-(1,3-dimethylbutyl) ) -P-phenylenediamine, trade name “NOCRACK 6C”, manufactured by Ouchi Shinsei Chemical Co., Ltd.) was added and kneaded for 2.5 minutes, and the rubber composition was discharged from the Banbury mixer. The temperature of the rubber composition at the end of kneading was 145 ° C. The rubber composition was cooled to room temperature and then kneaded again in a Banbury mixer for 3 minutes, and then the rubber composition was discharged from the Banbury mixer. Subsequently, using an open roll at 50 ° C., the obtained rubber composition, 1.6 parts of sulfur and a crosslinking accelerator (N-cyclohexyl-2-benzothiazolylsulfenamide (trade name “Noxeller CZ-G”) In addition, 1.4 parts of Ouchi Shinsei Chemical Co., Ltd.) and 1.4 parts of diphenylguanidine (trade name “Noxeller D”, manufactured by Ouchi Shinsei Chemical Co., Ltd.) 1.4 kneaded, The rubber composition was taken out.

  About the obtained rubber composition, the Mooney viscosity was measured. The rubber composition was press-crosslinked at 160 ° C. for 20 minutes to prepare each test piece, and each of the test pieces was evaluated for wet grip property, low heat generation property, and wear resistance. Table 1 shows the results.

(Example 2)
Instead of silica 1, silica 2 (trade name “Nip Seal ER”, manufactured by Tosoh Silica Co., Ltd., pH of 4% aqueous dispersion = 8.2, nitrogen adsorption specific surface area (BET method): 119 m ² / g) is used. The rubber composition was obtained in the same manner as in Example 1 except that the compounding amount of the silane coupling agent was changed from 4.6 parts to 3.3 parts. And each evaluation was performed. Table 1 shows the results.

(Comparative Example 1)
Instead of silica 1, silica 3 (trade name “Nip Seal AQ”, manufactured by Tosoh Silica Co., Ltd., pH of 4% aqueous dispersion = 6.1, nitrogen adsorption specific surface area (BET method): 200 m ² / g) is used. The rubber composition was obtained in the same manner as in Example 1 except that the blending amount of the silane coupling agent was changed from 4.6 parts to 5.7 parts. And each evaluation was performed. Table 1 shows the results.

(Comparative Example 2)
A rubber composition was obtained in the same manner as in Comparative Example 1 except that the modified conjugated diene rubber II was used instead of the modified conjugated diene rubber II, and each test piece was prepared. went. Table 1 shows the results.

(Comparative Example 3)
Comparative Example 1 except that unmodified conjugated diene rubber III (trade name “Nipol 1502”, manufactured by Nippon Zeon Co., Ltd., styrene content: 23.8% by weight) was used in place of the modified conjugated diene rubber I. Similarly, a rubber composition was obtained, each test piece was produced, and each measurement and each evaluation were performed. Table 1 shows the results.

(Comparative Example 4)
Instead of silica 3, silica 4 (trade name “Zeosil 1165MP”, manufactured by Rhodia, pH of 5% aqueous dispersion = 6.2, nitrogen adsorption specific surface area (BET method): 163 m ² / g) was used. Except for the above, a rubber composition was obtained in the same manner as in Comparative Example 1, each test piece was prepared, and each measurement and each evaluation were performed. Table 1 shows the results.

(Comparative Example 5)
A rubber composition was obtained in the same manner as in Example 1 except that the modified conjugated diene rubber II was used instead of the modified conjugated diene rubber II, and each test piece was prepared. went. Table 1 shows the results.

(Comparative Example 6)
A rubber composition was obtained in the same manner as in Example 1 except that the unmodified conjugated diene rubber III was used in place of the modified conjugated diene rubber I, and each test piece was prepared. Went. Table 1 shows the results.

(Comparative Example 7)
A rubber composition was obtained in the same manner as in Example 2 except that the unmodified conjugated diene rubber III was used in place of the modified conjugated diene rubber I, and each test piece was prepared. Went. Table 1 shows the results.

From the results shown in Table 1, the rubber compositions of the present invention (Examples 1 and 2) were compared with rubber compositions (Comparative Examples 1 and 4) in which silica having a pH of less than 8 was blended. The low exothermic property and wet grip property of the product were remarkably excellent, and the wear resistance was also excellent. Further, even when compared with other rubber compositions (Comparative Examples 2, 3, 5, 6, and 7), the low heat build-up property and wet grip property of the rubber cross-linked product were remarkably excellent.
On the other hand, the rubber composition containing no modified conjugated diene rubber specified in the present invention and containing a modified conjugated diene rubber not specified in the present invention (Comparative Example 5) has a pH of less than 8. Compared with the rubber composition (Comparative Example 2) formed by blending, the effect of improving the low heat build-up and wear resistance of the rubber cross-linked product was small. In addition, the rubber composition (Comparative Examples 6 and 7) which does not contain the modified conjugated diene rubber specified in the present invention and contains an unmodified conjugated diene rubber is a rubber formed by blending silica having a pH of less than 8. Compared to the composition (Comparative Example 3), the effect of improving the low heat build-up of the crosslinked rubber was small and the wear resistance was inferior.

Claims (4)

100 parts by weight of a rubber component containing a modified conjugated diene rubber obtained by reacting a conjugated diene polymer chain having an active end with a silicon compound having a functional group capable of reacting with the active end 10 to 200 parts by weight of silica having a pH of 8 to 12 and a nitrogen adsorption specific surface area (BET method) of 119 to 300 m ² / g ,
A rubber composition in which the silicon compound is a polyorganosiloxane or a hydrocarbyloxysilane compound . A rubber composition according to the cross-linking agent further comprising Claim 1. A crosslinked rubber product obtained by crosslinking the rubber composition according to claim 2 . A tire using the rubber cross-linked product according to claim 3 .