JP2012224768A - Rubber composition for tire, and pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for a tire, capable of being well balancedly improved in low fuel cost and wet grip performance.SOLUTION: The rubber composition for a tire contains: a copolymer which is obtained by copolymerizing 1,3-butadiene, a compound represented by formula (I) (wherein Rto Rare a hydrocarbon group, and r is an integer) and a styrenic compound having a specific substituent, and whose terminal is modified with a modifier having a functional group containing at least one atom selected from the group consisting of nitrogen, oxygen and silicon; and a modified natural rubber having a phosphorus content of ≤200 ppm.

Description

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

In recent years, from the standpoint of resource saving, energy saving, and environmental protection, social demands for reduction of carbon dioxide emissions have increased. Various countermeasures such as reducing the weight of automobiles and using electric energy have been studied for the purpose of reducing carbon dioxide emissions from automobiles.

As a common problem for automobiles, it is necessary to improve fuel efficiency by improving the rolling resistance of tires, and further, there is an increasing demand for automobiles to improve safety during driving. The fuel efficiency and safety of these automobiles depend largely on the performance of the tires used, and the demand for improvements in fuel economy, wet grip performance, handling stability, and durability has been increasing for automobile tires. Yes. These tire characteristics depend on various factors such as the structure and materials used of the tire, but in particular, greatly depend on the performance of the rubber composition used for the tread portion in contact with the road surface. For this reason, many technical improvements of rubber compositions for tires have been studied and proposed and put into practical use.

For example, the tire tread rubber is required to have low hysteresis loss for improving fuel efficiency and high wet skid resistance for improving wet grip performance. However, the relationship between low hysteresis loss and high wet skid resistance is contradictory, and it is difficult to solve the problem with only one performance improvement. A typical technique for improving the rubber composition for tires is to improve the raw materials used, improving the structure of the raw rubber typified by styrene butadiene rubber and butadiene rubber, reinforcing fillers such as carbon black and silica, Improvements in the structure and composition of vulcanizing agents and plasticizers have been made.

As a method for improving fuel economy and wet grip performance in a well-balanced manner, there is a method using silica as a filler. Silica has strong self-aggregation property and there is room for improvement in that it is difficult to disperse. In Patent Document 1, a styrene butadiene rubber terminal-modified with a specific compound containing a nitrogen atom and a silicon atom and an aliphatic carboxylic acid zinc salt are blended, and a rubber composition excellent in fuel efficiency and wet grip performance is obtained. Although a method for obtaining an object is described, provision of other methods is also sought.

JP 2010-111754 A

The present invention solves the above-mentioned problems and can improve the fuel economy and wet grip performance in a well-balanced manner, and a pneumatic composition using the tire rubber composition for each member (particularly, tread) of the tire. The object is to provide a tire.

（式中、Ｒ^１〜Ｒ^３は、炭化水素基を表す。ｒは整数を表す。）

（式中、Ｒ^４及びＲ^５は、炭化水素基を表す。Ｒ^４及びＲ^５は互いに結合していてもよい。Ｒ^６は水素原子又は炭化水素基を表す。） The present invention is obtained by copolymerizing 1,3-butadiene, a compound represented by the following general formula (I), and a compound represented by the following general formula (II), and the terminal is formed from nitrogen, oxygen and silicon. A copolymer having a weight average molecular weight Mw of 1.0 × 10 ^{5 to} 2.5 × 10 ⁶ and modified with a modifier having a functional group containing at least one atom selected from the group consisting of phosphorus and The present invention relates to a tire rubber composition containing a modified natural rubber in an amount of 200 ppm or less.

^(Wherein, R 1 to R ³ are, .r representing the hydrocarbon radical is an integer.)

(In the formula, R ⁴ and R ⁵ represent a hydrocarbon group. R ⁴ and R ⁵ may be bonded to each other. R ⁶ represents a hydrogen atom or a hydrocarbon group.)

The copolymer may be obtained by copolymerizing styrene together with at least the 1,3-butadiene, the compound represented by the general formula (I), and the compound represented by the general formula (II). preferable.

In the above general formula (I), the hydrocarbon group represented by R ¹ , R ² and R ³ has an integer of 1 to 10 carbon atoms and r is an integer of 1 to 30; in the above general formula (II), R ⁴ , it is preferable carbon number of the hydrocarbon group represented by R ⁵ and ^{R 6} are 1-10.

The content of the compound represented by the general formula (I) in the copolymer is 0.05 to 35% by mass, and the content of the compound represented by the general formula (II) is 0.05 to 35% by mass. It is preferable that

（式中、Ｒ^７、Ｒ^８及びＲ^９は、同一若しくは異なって、アルキル基、アルコキシ基、シリルオキシ基、カルボキシル基、メルカプト基又はこれらの誘導体を表す。Ｒ^１０及びＲ^１１は、同一若しくは異なって、水素原子又はアルキル基を表す。ｎは整数を表す。）

（式中、Ｒ^１２、Ｒ^１３及びＲ^１４は、同一若しくは異なって、アルキル基、アルコキシ基、シリルオキシ基、カルボキシル基、メルカプト基又はこれらの誘導体を表す。Ｒ^１５は、環状エーテル基を表す。ｐ及びｑは整数を表す。） The modifying agent is preferably a compound represented by the following general formula (III) or the following general formula (IV).

(Wherein R ⁷ , R ⁸ and R ⁹ are the same or different and each represents an alkyl group, an alkoxy group, a silyloxy group, a carboxyl group, a mercapto group, or a derivative thereof. R ¹⁰ and R ¹¹ are the same or different. And represents a hydrogen atom or an alkyl group, and n represents an integer.)

(In formula, R <^12> , R <^13> and R < ¹⁴ > are the same or different, and represent an alkyl group, an alkoxy group, a silyloxy group, a carboxyl group, a mercapto group, or derivatives thereof. R < ¹⁵ > represents a cyclic ether group. p and q represent integers.)

The nitrogen content of the modified natural rubber is preferably 0.3% by mass or less.

The tire rubber composition preferably contains 5% by mass or more of the copolymer and 10% by mass or more of the modified natural rubber in 100% by mass of the rubber component.

The present invention also relates to a pneumatic tire produced using the rubber composition.

According to the present invention, a copolymer obtained by copolymerizing 1,3-butadiene and a specific compound, having a terminal modified with a specific modifier, and having a weight average molecular weight Mw within a specific range; Since it is a rubber composition for tires containing a modified natural rubber whose content is not more than a specific amount, fuel economy and wet grip performance can be improved in a well-balanced manner. By using the rubber composition for each member (particularly, tread) of the tire, a pneumatic tire having excellent performance can be provided.

The rubber composition for tires of the present invention is obtained by copolymerizing 1,3-butadiene, a compound represented by the above general formula (I), and a compound represented by the above general formula (II). Co-modified with a modifier having a functional group containing at least one atom selected from the group consisting of nitrogen, oxygen and silicon and having a weight average molecular weight Mw of 1.0 × 10 ^{5 to} 2.5 × 10 ⁶ A polymer and a modified natural rubber (HPNR) having a phosphorus content of 200 ppm or less.

In the copolymer, the main chain is modified with the compound represented by the general formula (I) and the compound represented by the general formula (II), and at least one terminal is modified by the modifying agent. Therefore, the interaction between the compound (especially the oxygen atom contained in the compound) and the filler and the interaction between the modifier and the filler occurs, and the dispersibility of the filler is improved and the copolymer The movement of is restrained. As a result, hysteresis loss can be reduced, fuel efficiency can be improved, and good wet grip performance can be obtained, and these performances can be improved synergistically.

In addition, modified natural rubber with reduced or removed phospholipids contained in natural rubber (NR) (preferably modified natural rubber from which proteins and gels have also been removed) has the property of not generating heat. Compared with, it is possible to further reduce fuel consumption. In addition, the wet grip performance can be improved.

Furthermore, in the present invention, by using the copolymer and the modified natural rubber in combination, low fuel consumption and wet grip performance can be synergistically improved.

（式中、Ｒ^１〜Ｒ^３は、炭化水素基を表す。ｒは整数を表す。）

（式中、Ｒ^４及びＲ^５は、炭化水素基を表す。Ｒ^４及びＲ^５は互いに結合していてもよい。Ｒ^６は水素原子又は炭化水素基を表す。） (Copolymer)
In the present specification, the “copolymer” is described as a concept included in the rubber component.
The copolymer is obtained by copolymerizing at least 1,3-butadiene, a compound represented by the following general formula (I), and a compound represented by the following general formula (II), the terminal of which is nitrogen, oxygen And a modifier having a functional group containing at least one atom selected from the group consisting of silicon and silicon.

^(Wherein, R 1 to R ³ are, .r representing the hydrocarbon radical is an integer.)

(In the formula, R ⁴ and R ⁵ represent a hydrocarbon group. R ⁴ and R ⁵ may be bonded to each other. R ⁶ represents a hydrogen atom or a hydrocarbon group.)

The hydrocarbon group represented by R ¹ and R ² in the general formula (I) preferably has 1 to 10 carbon atoms. If the carbon number exceeds 10, the cost tends to be high. The number of carbon atoms is preferably 1-8, more preferably 1-6, and still more preferably 1-3, because the resulting copolymer is highly effective in improving fuel economy and wet grip performance.

Examples of the hydrocarbon group represented by R ¹ and R ² in the general formula (I) include a divalent aliphatic hydrocarbon group such as an alkylene group and a divalent aromatic hydrocarbon group such as an arylene group. Can be mentioned. R ¹ and R ² are preferably an alkylene group, more preferably a methylene group, an ethylene group, an n-propylene group, and an isopropylene group, because the resulting copolymer has high fuel economy and wet grip performance improvement effect. preferable. R ¹ and R ² may be the same or different.
When r is 2 or more, each R ² may be the same or different.

The hydrocarbon group represented by R ³ in the general formula (I) preferably has 1 to 10 carbon atoms. If the carbon number exceeds 10, the cost tends to be high. The number of carbon atoms is preferably 1-8, more preferably 1-6, from the viewpoint that the resulting copolymer is highly effective in improving fuel economy and wet grip performance.

Examples of the hydrocarbon group represented by R ³ in the general formula (I) include a monovalent aliphatic hydrocarbon group such as an alkyl group and a monovalent aromatic hydrocarbon group such as an aryl group. R ³ is preferably an alkyl group from the viewpoint of high fuel economy and wet grip performance improvement effect by the obtained copolymer, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, An isobutyl group, a sec-butyl group, and a tert-butyl group are more preferable, and an n-butyl group is still more preferable.

As r (integer) of general formula (I), 1-30 are preferable. Further, r is more preferably 1-20, further preferably 1-15, and particularly preferably 5-12. If r exceeds 30, the cost increases.

（上記一般式（Ｉ−Ｉ）中のＲ^１〜Ｒ^３及びｒは、上記一般式（Ｉ）中のＲ^１〜Ｒ^３及びｒと同様である。） Further, among the compounds represented by the general formula (I), the compound represented by the following general formula (I-I) is highly effective in improving fuel economy and wet grip performance due to the obtained copolymer. Compounds are preferred.

^(R 1 to R ³ and r in the general formula (I-I) is the same as ^R 1 to R ³ and r in the general formula (I).)

The compound represented by the general formula (I) can be synthesized by a known method. For example, it can be obtained by reacting a halogenated alkylstyrene with a polyalkylene glycol monoalkyl ether in the presence of a strong base. Specifically, using N, N-dimethylformamide as a solvent, a halogenated alkylstyrene (for example, 4-chloromethylstyrene) and a polyalkylene glycol monoalkyl ether (triethylene glycol monoalkyl ether) in the presence of sodium hydride. And butyl ether). The compound represented by general formula (I) may be used independently and may combine 2 or more types.

The content of the compound represented by the general formula (I) in the copolymer is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and preferably 35% by mass or less. More preferably, it is 20 mass% or less, More preferably, it is 15 mass% or less, Especially preferably, it is 5 mass% or less, Most preferably, it is 2 mass% or less. If it is less than 0.05% by mass, it is difficult to obtain an effect of improving fuel economy and wet grip performance, while if it exceeds 35% by mass, the cost tends to be high.

The hydrocarbon group represented by R ⁴ and R ⁵ in the general formula (II) preferably has 1 to 10 carbon atoms. If the carbon number exceeds 10, the cost tends to be high. The number of carbon atoms is preferably 1-8, more preferably 1-6, from the viewpoint that the resulting copolymer is highly effective in improving fuel economy and wet grip performance.

Examples of the hydrocarbon group represented by R ⁴ and R ⁵ in the general formula (II) include those similar to R ³ . Examples of the hydrocarbon group in which R ⁴ and R ⁵ are bonded to each other include alkylene groups such as an ethylene group formed by connecting R ⁴ and R ⁵ . In addition, the carbon number of the hydrocarbon group formed by connecting R ⁴ and R ⁵ is preferably 1 to 10, more preferably 1 to 8, still more preferably 1 to 6, and particularly preferably 1 to 4. . R ⁴ and R ⁵ are preferably an alkyl group or an alkylene group, and n-butyl group, methyl group, ethyl group, n- A propyl group, an isopropyl group, and an ethylene group are more preferable. R ⁴ and R ⁵ may be the same or different. R ⁴ and R ⁵ are preferably bonded to each other.

The hydrocarbon group represented by R ⁶ in the general formula (II) preferably has 1 to 10 carbon atoms. If the carbon number exceeds 10, the cost tends to be high. The number of carbon atoms is preferably 1 to 6, more preferably 1 to 4, from the viewpoint that the resulting copolymer is highly effective in improving fuel economy and wet grip performance.

Examples of the hydrocarbon group represented by R ⁶ in the general formula (II) include those similar to R ³ . R ⁶ is preferably a hydrogen atom from the viewpoint that the resulting copolymer is highly effective in improving fuel economy and wet grip performance.

（上記一般式（ＩＩ−Ｉ）中のＲ^４〜Ｒ^６は、上記一般式（ＩＩ）中のＲ^４〜Ｒ^６と同様である。） Further, among the compounds represented by the general formula (II), the compound represented by the following general formula (II-I) is highly effective in improving fuel economy and wet grip performance by the obtained copolymer. Compounds are preferred.

^(R 4 to R ⁶ in the general formula (II-I) is the same as ^R 4 to R ⁶ in the general formula (II).)

The compound represented by the general formula (II) can be obtained by acetalizing vinylbenzaldehyde (for example, 4-vinylbenzaldehyde) by a known method. Specific examples thereof include 4-vinylbenzaldehyde dibutyl acetal, 4-vinylbenzaldehyde ethylene acetal, 4-vinylbenzaldehyde dimethyl acetal, 4-vinylbenzaldehyde diethyl acetal, 4-vinylbenzaldehyde di-n-propyl acetal, 4-vinylbenzaldehyde diisopropyl. Examples include acetal and 3-vinylbenzaldehyde dibutyl acetal. These may be used alone or in combination of two or more.

The content of the compound represented by the general formula (II) in the copolymer is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and preferably 35% by mass or less. More preferably, it is 20 mass% or less, More preferably, it is 15 mass% or less, Especially preferably, it is 5 mass% or less, Most preferably, it is 2 mass% or less. If it is less than 0.05% by mass, it is difficult to obtain an effect of improving fuel economy and wet grip performance, while if it exceeds 35% by mass, the cost tends to be high.

The copolymer is obtained by copolymerizing styrene with at least the 1,3-butadiene, the compound represented by the general formula (I), and the compound represented by the general formula (II). May be. When the copolymer contains styrene, the styrene content is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass or less. More preferably, it is 25 mass% or less. If it is less than 5% by mass, the wet grip performance tends to deteriorate, whereas if it exceeds 40% by mass, the fuel efficiency tends to deteriorate.

The content of 1,3-butadiene in the copolymer is not particularly limited, and may be appropriately adjusted according to the content of other components, but is preferably 40% by mass or more, more preferably 60% by mass or more. In addition, it is preferably 90% by mass or less, more preferably 85% by mass or less, and further preferably 80% by mass or less. If it is in the said range, the effect of this invention will be acquired favorably.

The content of the compound represented by the general formula (I), the compound represented by the general formula (II), 1,3-butadiene and styrene in the copolymer can be measured by the method of Examples described later.

<Modifier>
In the copolymer, at least one terminal is modified with a modifier having a functional group containing at least one atom selected from the group consisting of nitrogen, oxygen and silicon.

Examples of the functional group include amino group, amide group, alkoxysilyl group, isocyanate group, imino group, imidazole group, urea group, ether group, carbonyl group, carboxyl group, hydroxyl group, nitrile group, and pyridyl group. . Of these, an amino group (preferably an alkylamino group, more preferably a dialkylamino group), an alkoxysilyl group, and an ether group are preferable from the viewpoint that the effect of improving fuel economy and wet grip performance is great.

Examples of the modifier include 3-glycidoxypropyltrimethoxysilane, (3-triethoxysilylpropyl) tetrasulfide, 1- (4-N, Ndimethylaminophenyl) -1-phenylethylene, 1,1- Dimethoxytrimethylamine, 1,2-bis (trichlorosilyl) ethane, 1,3,5-tris (3-triethoxysilylpropyl) isocyanurate, 1,3,5-tris (3-trimethoxysilylpropyl) isocyanurate, 1,3-dimethyl-2-imidazolidinone, 1,3-propanediamine, 1,4-diaminobutane, 1- [3- (triethoxysilyl) propyl] -4,5-dihydroimidazole, 1-glycidyl- 4- (2-pyridyl) piperazine, 1-glycidyl-4-phenylpiperazine, 1-glycidyl -4-methylpiverazine, 1-glycidyl-4-methylhomopiverazine, 1-glycidylhexamethyleneimine, 11-aminoundecyltriethoxysilane, 11-aminoundecyltrimethoxysilane, 1-benzyl-4-glycidylpiperazine 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (4-morpholinodithio) benzothiazole, 2- (6-aminoethyl) -3-aminopropyltrimethoxysilane, 2- (triethoxy Silylethyl) pyridine, 2- (trimethoxysilylethyl) pyridine, 2- (2-pyridylethyl) thiopropyltrimethoxysilane, 2- (4-pyridylethyl) thioprovir trimethoxysilane, 2,2-diethoxy- 1,6-diaza-2-silacyclooctane, 2 2-dimethoxy-1,6-diaza-2-silacyclooctane, 2,3-dichloro-1,4-naphthoquinone, 2,4-dinitrobenzenesulfonyl chloride, 2,4-tolylene diisocyanate, 2- (4 -Pyridylethyl) triethoxysilane, 2- (4-pyridylethyl) trimethoxysilane, 2-cyanoethyltriethoxysilane, 2-tributylstannyl-1,3-butadiene, 2- (trimethoxysilylethyl) pyridine, 2 -Vinylpyridine, 2- (4-pyridylethyl) triethoxysilane, 2- (4-pyridylethyl) trimethoxysilane, 2-laurylthioethylphenylketone, 3- (1-hexamethyleneimino) propyl (triethoxy) silane , 3- (1,3-Dimethylbutylidene) aminopropyltriethoxysilane Lan, 3- (1,3-dimethylbutylidene) aminopropyltrimethoxysilane, 3- (2-aminoethylaminopropyl) trimethoxysilane, 3- (m-aminophenoxy) propyltrimethoxysilane, 3- (N , N-dimethylamino) propyltriethoxysilane, 3- (N, N-dimethylamino) propyltrimethoxysilane, 3- (N-methylamino) propyltriethoxysilane, 3- (N-methylamino) propyltrimethoxy Silane, 3- (N-allylamino) propyltrimethoxysilane, 3,4-diaminobenzoic acid, 3-aminopropyldimethylethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyl Tris (methoxydiethoxy) silane, 3-amino Propyldiisopropylethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-diethylaminopropyltrimethoxysilane 3-diethoxy (methyl) silylpropyl succinic anhydride, 3- (N, N-diethylaminopropyl) triethoxysilane, 3- (N, N-diethylaminopropyl) trimethoxysilane, 3- (N, N-dimethylamino) Propyl) diethoxymethylsilane, 3- (N, N-dimethylaminopropyl) triethoxysilane, 3- (N, N-dimethylaminopropyl) trimethoxysilane, 3-triethoxysilylpropyl succinic anhydride, 3-tri Toxisilylpropyl acetic anhydride, 3-triphenoxysilylpropyl succinic anhydride, 3-triphenoxysilylpropyl acetic anhydride, 3-trimethoxysilylpropylbenzothiazole tetrasulfide, 3-hexamethyleneiminopropyltriethoxysilane, 3-mercaptopropyl Trimethoxysilane, (3-triethoxysilylpropyl) diethylenetriamine, (3-trimethoxysilylpropyl) diethylenetriamine, 4,4′-bis (diethylamino) benzophenone, 4,4′-bis (dimethylamino) benzophenone, 4′- (Imidazol-1-yl) -acetophenone, 4- [3- (N, N-diglycidylamino) propyl] morpholine, 4-glycidyl-2,2,6,6-tetramethylpiberidinyloxy, 4- amino Butyltriethoxysilane, 4-vinylpyridine, 4-morpholinoacetophenone, 4-morpholinobenzophenone, m-aminophenyltrimethoxysilane, N- (1,3-dimethylbutylidene) -3- (triethoxysilyl) -1- Propanamine, N- (1,3-dimethylbutylidene) -3- (trimethoxysilyl) -1-propanamine, N- (1-methylethylidene) -3- (triethoxysilyl) -1-propanamine, N- (2-aminoethyl) -3-aminopropylmethyldiethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminopropyltri Ethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-a Noethyl) -11-aminoundecyltriethoxysilane, N- (2-aminoethyl) -11-aminoundecyltrimethoxysilane, N- (2-aminoethyl) -3-aminoisobutylmethyldiethoxysilane, N- (2-aminoethyl) -3-aminoisobutylmethyldimethoxysilane, N- (3-diethoxymethylsilylpropyl) succinimide, N- (3-triethoxysilylpropyl) -4,5-dihydroimidazole, N- (3 -Triethoxysilylpropyl) pyrrole, N- (3-trimethoxysilylpropyl) pyrrole, N-3- [amino (polypropyleneoxy)] aminopropyltrimethoxysilane, N- [5- (triethoxysilyl) -2- Aza-1-oxopentyl] caprolactam, N- [5- (trimethoxy) Silyl) -2-aza-1-oxopentyl] caprolactam, N- (6-aminohexyl) aminomethyltriethoxysilane, N- (6-aminohexyl) aminomethyltrimethoxysilane, N-allyl-aza-2, 2-diethoxysilacyclopentane, N-allyl-aza-2,2-dimethoxysilacyclopentane, N- (cyclohexylthio) phthalimide, Nn-butyl-aza-2,2-diethoxysilacyclopentane, N -N-butyl-aza-2,2-dimethoxysilacyclopentane, N, N, N ', N'-tetraethylaminobenzophenone, N, N, N', N'-tetramethylthiourea, N, N, N ' , N′-tetramethylurea, N, N′-ethyleneurea, N, N′-diethylaminobenzophenone, N, N′-diethylaminobenzopheno N, N′-diethylaminobenzofuran, methyl N, N′-diethylcarbamate, N, N′-diethylurea, (N, N-diethyl-3-aminopropyl) triethoxysilane, (N, N-diethyl) -3-aminopropyl) trimethoxysilane, N, N-dioctyl-N′-triethoxysilylpropylurea, N, N-dioctyl-N′-trimethoxysilylpropylurea, methyl N, N-diethylcarbamate, N , N-diglycidylcyclohexylamine, N, N-dimethyl-o-toluidine, N, N-dimethylaminostyrene, N, N-diethylaminopropylacrylamide, N, N-dimethylaminopropylacrylamide, N-ethylaminoisobutyltriethoxy Silane, N-ethylaminoisobutyltrimethoxysilane, -Ethylaminoisobutylmethyldiethoxysilane, N-oxydiethylene-2-benzothiazolesulfenamide, N-cyclohexylaminopropyltriethoxysilane, N-cyclohexylaminopropyltrimethoxysilane, N-methylaminopropylmethyldimethoxysilane, N -Methylaminopropylmethyldiethoxysilane, N-vinylbenzylazacycloheptane, N-phenylpyrrolidone, N-phenylaminopropyltriethoxysilane, N-phenylaminopropyltrimethoxysilane, N-phenylaminomethyltriethoxysilane, N -Phenylaminomethyltrimethoxysilane, n-butylaminopropyltriethoxysilane, n-butylaminopropyltrimethoxysilane, N-methylaminopropyltri Ethoxysilane, N-methylaminopropyltrimethoxysilane, N-methyl-2-piperidone, N-methyl-2-pyrrolidone, N-methyl-ε-caprolactam, N-methylindolinone, N-methylpyrrolidone, p- ( 2-dimethylaminoethyl) styrene, p-aminophenyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, (aminoethylamino) -3-isobutyldiethoxysilane, (amino Ethylamino) -3-isobutyldimethoxysilane, (aminoethylaminomethyl) phenethyltriethoxysilane, (aminoethylaminomethyl) phenethyltrimethoxysilane, acrylic acid, diethyl adipate, acetamidopropyltrimethoxysilane, amino Enyltrimethoxysilane, aminobenzophenone, ureidopropyltriethoxysilane, ureidopropyltrimethoxysilane, ethylene oxide, octadecyldimethyl (3-trimethoxysilylpropyl) ammonium chloride, glycidoxypropyltriethoxysilane, glycidoxypropyltrimethoxysilane , Glycerol tristearate, chlorotriethoxysilane, chloropropyltriethoxysilane, chloropolydimethylsiloxane, chloromethyldiphenoxysilane, diallyldiphenyltin, diethylaminomethyltriethoxysilane, diethylaminomethyltrimethoxysilane, diethyl (glycidyl) amine, diethyl Dithiocarbamic acid 2-benzothiazoyl ester, diethoxydichlorosilane, ( (Cyclohexylaminomethyl) triethoxysilane, (cyclohexylaminomethyl) trimethoxysilane, diglycidylpolysiloxane, dichlorodiphenoxysilane, dicyclohexylcarbodiimide, divinylbenzene, diphenylcarbodiimide, diphenylcyanamide, diphenylmethane diisocyanate, diphenoxymethylchlorosilane, dibutyldichloro Tin, dimethyl (acetoxy-methylsiloxane) polydimethylsiloxane, dimethylaminomethyltriethoxysilane, dimethylaminomethyltrimethoxysilane, dimethyl (methoxy-methylsiloxane) polydimethylsiloxane, dimethylimidazolidinone, dimethylethyleneurea, dimethyldichlorosilane , Dimethylsulfoyl chloride, silsesquioxane , Sorbitan trioleate, sorbitan monolaurate, titanium tetrakis (2-ethylhexoxide), tetraethoxysilane, tetraglycidyl-1, 3-bisaminomethylcyclohexane, tetraphenoxysilane, tetramethylthiuram disulfide, tetramethoxy Silane, triethoxyvinylsilane, tris (3-trimethoxysilylpropyl) cyanurate, triphenyl phosphate, triphenoxychlorosilane, triphenoxymethylsilicon, triphenoxymethylsilane, carbon dioxide, bis (triethoxysilylpropyl) amine, bis (tri Methoxysilylpropyl) amine, bis [3- (triethoxysilyl) propyl] ethylenediamine, bis [3- (trimethoxysilyl) propyl] Range amine, bis [3- (triethoxysilyl) propyl] urea, bis [(trimethoxysilyl) propyl] urea, bis (2-hydroxymethyl) -3-aminopropyltriethoxysilane, bis (2-hydroxymethyl) -3-aminopropyltrimethoxysilane, bis (2-ethylhexanoate) tin, bis (2-methylbutoxy) methylchlorosilane, bis (3-triethoxysilylpropyl) tetrasulfide, bisdiethylaminobenzophenone, bisphenol A diglycidyl Ether, bisphenoxyethanol fluorenediglycidyl ether, bis (methyldiethoxysilylpropyl) amine, bis (methyldimethoxysilylpropyl) -N-methylamine, hydroxymethyltriethoxysilane, vinyltri (2-ethylhexyloxy) silane, vinylbenzyldiethylamine, vinylbenzyldimethylamine, vinylbenzyltributyltin, vinylbenzylpiperidine, vinylbenzylpyrrolidine, pyrrolidine, phenyl isocyanate, phenylisothiocyanate, (phenylaminomethyl) methyldimethoxysilane, ( Phenylaminomethyl) methyldiethoxysilane, phthalic acid amide, hexamethylene diisocyanate, benzylidene aniline, polydiphenylmethane diisocyanate, polydimethylsiloxane, methyl-4-pyridyl ketone, methylcaprolactam, methyltriethoxysilane, methyltriphenoxysilane, Examples include methyl lauryl thiopropionate and silicon tetrachloride.

（式中、Ｒ^７、Ｒ^８及びＲ^９は、同一若しくは異なって、アルキル基、アルコキシ基、シリルオキシ基、カルボキシル基（−ＣＯＯＨ）、メルカプト基（−ＳＨ）又はこれらの誘導体を表す。Ｒ^１０及びＲ^１１は、同一若しくは異なって、水素原子又はアルキル基を表す。ｎは整数を表す。）

（式中、Ｒ^１２、Ｒ^１３及びＲ^１４は、同一若しくは異なって、アルキル基、アルコキシ基、シリルオキシ基、カルボキシル基（−ＣＯＯＨ）、メルカプト基（−ＳＨ）又はこれらの誘導体を表す。Ｒ^１５は、環状エーテル基を表す。ｐ及びｑは整数を表す。） From the viewpoint that the effect of improving fuel economy and wet grip performance is great, the modifier is preferably a compound represented by the following general formula (III) or the following general formula (IV), The compounds represented are more preferred. In addition, a compound in which r in the general formula (I) is 5 to 12, R ⁴ and R ^{5 in} the general formula (II) are bonded to each other, and the modifier is represented by the following general formula (III) When the copolymer is blended, the effect of improving fuel economy and wet grip performance is particularly great.

(Wherein R ⁷ , R ⁸ and R ⁹ are the same or different and represent an alkyl group, an alkoxy group, a silyloxy group, a carboxyl group (—COOH), a mercapto group (—SH) or a derivative thereof. R ¹⁰ And R ¹¹ are the same or different and each represents a hydrogen atom or an alkyl group, and n represents an integer.)

(In formula, R <^12> , R <^13> and R < ¹⁴ > are the same or different and represent an alkyl group, an alkoxy group, a silyloxy group, a carboxyl group (-COOH), a mercapto group (-SH), or these derivatives. R < ¹⁵ >. Represents a cyclic ether group, and p and q represent an integer.)

In the compound represented by the general formula (III), examples of the alkyl group for R ⁷ , R ⁸ and R ⁹ include an alkyl group having 1 to 4 carbon atoms such as a methyl group (preferably having 1 to 3 carbon atoms). Etc. Examples of the alkoxy group of R ⁷ , R ⁸ and R ⁹ include an alkoxy group having 1 to 8 carbon atoms (preferably 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms) such as a methoxy group. . The alkoxy group includes a cycloalkoxy group and an aryloxy group. Examples of the silyloxy group for R ⁷ , R ^8, and R ⁹ include a silyloxy group substituted with an aliphatic group having 1 to 20 carbon atoms or an aromatic group (such as a trimethylsilyloxy group or a tribenzylsilyloxy group). .

In the compound represented by the general formula (III), examples of the alkyl group of R ¹⁰ and R ¹¹ include the same groups as the alkyl groups (alkyl groups of R ⁷ , R ⁸ and R ⁹ ). it can.

R ⁷ , R ⁸ and R ⁹ are preferably an alkoxy group, and R ¹⁰ and R ¹¹ are preferably an alkyl group because the fuel efficiency and the effect of improving wet grip performance are great.

n (integer) is preferably 0 to 5 for the reason of availability. Furthermore, n is more preferably 2 to 4, and most preferably 3. If n is 6 or more, the cost increases.

Specific examples of the compound represented by the general formula (III) include 3- (N, N-dimethylamino) propyltriethoxysilane and 3- (N, N-dimethylamino) propyltrimethyl exemplified as the modifier. And methoxysilane. Of these, 3- (N, N-dimethylamino) propyltrimethoxysilane is preferable.

In the compound represented by the general formula (IV), R ¹² , R ¹³ and R ¹⁴ are the same as R ⁷ , R ⁸ and R ⁹ in the compound represented by the general formula (III). As R ¹² , R ^13, and R ¹⁴ , an alkoxy group is preferable because the effect of improving fuel economy and wet grip performance is great.

In the compound represented by the general formula (IV), examples of the cyclic ether group represented by R ¹⁵ include a cyclic ether group having one ether bond such as an oxirane group and a cyclic ether group having two ether bonds such as a dioxolane group. And cyclic ether groups having three ether bonds such as a trioxane group. Among these, a cyclic ether group having one ether bond is preferable, and an oxirane group is more preferable because the effect of improving fuel economy and wet grip performance is great. Carbon number of a cyclic ether group becomes like this. Preferably it is 2-7, More preferably, it is 2-4. The cyclic ether group preferably has no unsaturated bond in the ring skeleton.

The p (integer) is preferably 0 to 5 for reasons of availability and reactivity. Further, p is more preferably from 2 to 4, and most preferably 3. If p is 6 or more, the cost increases.

q (integer) is preferably 0 to 5 for reasons of availability and reactivity. Furthermore, q is more preferably 1 to 3, and most preferably 1. If q is 6 or more, the cost increases.

Specific examples of the compound represented by the general formula (IV) include 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane exemplified as the modifier. Of these, 3-glycidoxypropyltrimethoxysilane is preferable.

Examples of suitable modifiers other than the compound represented by the general formula (III) or (IV) include N- (3-triethoxysilylpropyl) -4,5-dihydroimidazole, silicon tetrachloride and the like. .

<Method for producing copolymer>
The copolymer is obtained by, for example, copolymerizing 1,3-butadiene, a compound represented by the general formula (I), and a compound represented by the general formula (II) with styrene as necessary. It can manufacture by making the said modifier react with the at least one terminal of the obtained copolymer, Specifically, it can manufacture with the following manufacturing methods.

<Polymerization method>
The polymerization method of the copolymer is not particularly limited, and any of a solution polymerization method, a gas phase polymerization method, and a bulk polymerization method can be used. In particular, the compound represented by the general formula (I), the general formula ( From the viewpoint of the stability of the compound represented by II), the solution polymerization method is preferred. Moreover, any of a batch type and a continuous type may be sufficient as the superposition | polymerization form.

When the solution polymerization method is used, the monomer concentration in the solution (the total of styrene, 1,3-butadiene, the compound represented by the general formula (I), the compound represented by the general formula (II), etc.) is , Preferably 5% by mass or more, more preferably 10% by mass or more. When the monomer concentration in the solution is less than 5% by mass, the amount of the copolymer obtained is small and the cost tends to be high. The monomer concentration in the solution is preferably 50% by mass or less, more preferably 30% by mass or less. If the monomer concentration in the solution exceeds 50% by mass, the solution viscosity becomes too high, stirring becomes difficult, and polymerization tends to be difficult.

<< Polymerization initiator in anionic polymerization >>
When anionic polymerization is performed, the polymerization initiator is not particularly limited, but an organic lithium compound is preferably used. As the organic lithium compound, those having an alkyl group having 2 to 20 carbon atoms are preferable. For example, ethyl lithium, n-propyl lithium, isopropyl lithium, n-butyl lithium, sec-butyl lithium, tert-butyl lithium, tert- Octyl lithium, n-decyl lithium, phenyl lithium, 2-naphthyl lithium, 2-butyl-phenyl lithium, 4-phenyl-butyl lithium, cyclohexyl lithium, cyclopentyl lithium, reaction products of diisopropenylbenzene and butyl lithium, etc. Among these, n-butyllithium or sec-butyllithium is preferable from the viewpoints of availability and safety.

<Method of anionic polymerization>
There is no restriction | limiting in particular as a method of manufacturing a copolymer by anionic polymerization using the said organolithium compound as a polymerization initiator, A conventionally well-known method can be used. Specifically, in an organic solvent inert to the reaction, for example, a hydrocarbon solvent such as an aliphatic, alicyclic, or aromatic hydrocarbon compound, butyl lithium or the like is used as a polymerization initiator, and a randomizer is used as necessary. 1,3-butadiene, the compound represented by the general formula (I), and the compound represented by the general formula (II) may be anionically polymerized with styrene, if necessary. In addition, after anionic polymerization, you may add a well-known anti-aging agent and alcohol etc. for the purpose of stopping a polymerization reaction as needed.

<< Hydrocarbon solvents in anionic polymerization >>
The hydrocarbon solvent is preferably one having 3 to 8 carbon atoms, such as propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene and trans-2. -Butene, cis-2-butene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene and the like.

《Randomizer in anionic polymerization》
The randomizer is a microstructure control of a conjugated diene moiety in a copolymer (for example, an increase in 1,2-bonds in butadiene, etc.) and a control of the composition distribution of monomer units in the copolymer (for example, It is a compound having an action such as a butadiene unit, randomization of a styrene unit, etc. The randomizer is not particularly limited, and any known compound generally used as a conventional randomizer can be used. For example, dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, bistetrahydrofurylpropane, triethylamine, pyridine, N-methylmorpholine, N, N, N ′, N′-tetramethylethylenediamine, 1,2-di Examples include ethers such as piperidinoethane and tertiary amines. Further, potassium salts such as potassium-t-amylate and potassium-t-butoxide, and sodium salts such as sodium-t-amylate can also be used.

The amount of randomizer used is preferably 0.01 molar equivalents or more, more preferably 0.05 molar equivalents or more per mole of the polymerization initiator. If the amount of randomizer used is less than 0.01 molar equivalent, the effect of addition tends to be small and it tends to be difficult to randomize. The amount of randomizer used is preferably 1000 molar equivalents or less, more preferably 500 molar equivalents or less per mole of the polymerization initiator. When the amount of the randomizer used exceeds 1000 molar equivalents, the monomer reaction rate changes greatly, and conversely, it tends to be difficult to randomize.

It does not specifically limit as the modification method by a modifier, A well-known method can be used. For example, after synthesizing a copolymer whose main chain is modified by anionic polymerization, the anion at the end of the copolymer reacts with the functional group of the modifying agent by bringing the copolymer into contact with the modifying agent. The terminal end of the copolymer is modified. As a result, a copolymer having a modified main chain and terminal is obtained. The amount of the modifier to be reacted is usually 0.01 to 10 parts by mass with respect to 100 parts by mass of the copolymer. The copolymer preferably has at least one terminal modified, and more preferably has both terminals modified.

In the present invention, after carrying out the modification reaction with the above-mentioned modifier, a known anti-aging agent or alcohol may be added as necessary to stop the polymerization reaction.

The weight average molecular weight Mw of the copolymer is 1.0 × 10 ^{5 to} 2.5 × 10 ⁶ . When Mw is less than 1.0 × 10 ^5, fuel economy tends to be poor, whereas when Mw exceeds 2.5 × 10 ⁶ , workability tends to be deteriorated. The lower limit of Mw is preferably 2.0 × 10 ⁵ or more, more preferably 3.0 × 10 ⁵ or more, and the upper limit is preferably 1.5 × 10 ⁶ or less, more preferably 1.0 × 10 ^6. It is as follows.
In addition, Mw can be adjusted suitably by methods, such as changing the quantity of the polymerization initiator used at the time of superposition | polymerization, and can be measured by the method of the below-mentioned Example.

The content of the copolymer in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 8% by mass or more. If it is less than 5% by mass, there is a tendency that it is difficult to obtain an effect of improving fuel efficiency and wet grip performance. Further, the content of the copolymer is preferably 50% by mass or less, more preferably 35% by mass or less, and still more preferably 25% by mass or less. When it exceeds 50 mass%, it tends to be expensive.

(Modified natural rubber (HPNR))
The modified natural rubber (HPNR) has a phosphorus content of 200 ppm or less.
If it exceeds 200 ppm, tan δ will increase and fuel economy will deteriorate, the Mooney viscosity of the unvulcanized rubber will increase and processability will deteriorate, and wet grip performance will tend to decrease. The phosphorus content is preferably 150 ppm or less, and more preferably 100 ppm or less. Here, the phosphorus content can be measured by a conventional method such as ICP emission analysis. Phosphorus is derived from phospholipids (phosphorus compounds).

In the modified natural rubber, the nitrogen content is preferably 0.3% by mass or less, more preferably 0.15% by mass or less, and further preferably 0.10% by mass or less. When the nitrogen content exceeds 0.3% by mass, the Mooney viscosity increases during storage and the processability tends to deteriorate, and the fuel economy and wet grip performance tend to deteriorate. The nitrogen content can be measured by a conventional method such as Kjeldahl method. Nitrogen is derived from protein.

A modified natural rubber having a phosphorus content of 100 ppm or less and a nitrogen content of 0.15% by mass or less (preferably 0.10% by mass or less) is bonded to R ⁴ and R ^{5 of} the above general formula (II). When the modifier is a compound in the case where it is a compound represented by the above general formula (III), the effect of improving fuel economy and wet grip performance is particularly great.

The gel content in the modified natural rubber is preferably 20% by mass or less, and more preferably 10% by mass or less. If it exceeds 20% by mass, the processability tends to deteriorate, and the fuel economy and wet grip performance tend to deteriorate. The gel content means a value measured as an insoluble content with respect to toluene which is a nonpolar solvent, and may be simply referred to as “gel content” or “gel content” below. The measuring method of the content rate of a gel part is as follows. First, a natural rubber sample is soaked in dehydrated toluene, light-shielded in the dark and left for 1 week, and then the toluene solution is centrifuged at 1.3 × 10 ⁵ rpm for 30 minutes to obtain an insoluble gel content and a toluene soluble content. Isolate. Methanol is added to the insoluble gel and solidified, and then dried, and the gel content is determined from the ratio between the mass of the gel and the original mass of the sample.

The modified natural rubber can be obtained, for example, by the production method described in JP 2010-138359 A. Among them, the process (A) of preparing a saponified natural rubber latex by saponifying the natural rubber latex, A production method comprising a step (B) of subjecting the agglomerated rubber obtained by agglomerating the saponified natural rubber latex to an alkali treatment and a step (C) of washing until the phosphorus content contained in the rubber is 200 ppm or less. What is prepared is preferred. By this production method, the phosphorus content can be reduced. Further, when the acid is agglomerated with the acid, the remaining acid is neutralized with an alkali treatment to not only prevent the rubber from being deteriorated by the acid but also to further reduce the nitrogen content in the rubber.

In the production method described above, the saponification treatment can be performed by adding an alkali and, if necessary, a surfactant to natural rubber latex and allowing to stand at a predetermined temperature for a certain time. In addition, you may perform stirring etc. as needed. According to the above production method, the phosphorus content and nitrogen content of natural rubber can be suppressed.

As the natural rubber latex, conventionally known latexes such as raw latex, purified latex, and high ammonia latex can be used. Examples of the alkali used for the saponification treatment include sodium hydroxide, potassium hydroxide, calcium hydroxide, and amine compounds, and sodium hydroxide and potassium hydroxide are particularly preferable. As the surfactant, known anionic surfactants, nonionic surfactants, and amphoteric surfactants can be used. Of these, anionic surfactants are preferred, and sulfonic acid anions are preferred. A surfactant is more preferable.

In the saponification treatment, the amount of alkali added may be appropriately set, but is preferably 0.1 to 10 parts by mass, more preferably 5 to 10 parts by mass with respect to 100 parts by mass of the solid content of the natural rubber latex. . The addition amount of the surfactant is preferably 0.01 to 5 parts by mass with respect to 100 parts by weight of the solid content of the natural rubber latex. The temperature and time of the saponification treatment may be set as appropriate, and is usually about 20 to 70 ° C. and about 1 to 72 hours.

After completion of the saponification reaction, the agglomerated rubber obtained by agglomerating the saponified natural rubber latex obtained by the reaction is crushed as necessary, and then the obtained agglomerated rubber or crushed rubber is brought into contact with an alkali. Perform alkali treatment. By the alkali treatment, the amount of nitrogen in the rubber can be further reduced, and the effects of the present invention are further exhibited. Examples of the aggregation method include a method of adding an acid such as formic acid. The alkali treatment method is not particularly limited as long as it is a method in which a rubber and an alkali are brought into contact with each other. Examples of the alkali that can be used for the alkali treatment include potassium carbonate, sodium carbonate, sodium hydrogen carbonate, and aqueous ammonia in addition to the alkali in the saponification treatment. Of these, sodium carbonate is preferred from the viewpoint of excellent effects of the present invention.

When the alkali treatment is performed by the immersion, the treatment can be performed by immersing rubber (crushed rubber) in an alkaline aqueous solution having a concentration of preferably 0.1 to 5 mass%, more preferably 0.2 to 3 mass%. Thereby, the amount of nitrogen in the rubber can be further reduced.

When the alkali treatment is performed by the immersion, the temperature of the alkali treatment can be set as appropriate, but is usually preferably 20 to 70 ° C. The alkali treatment time depends on the treatment temperature, but is preferably 1 to 20 hours, more preferably 2 to 12 hours, considering sufficient treatment and productivity.

Phosphorus content can be reduced by performing a washing treatment after the alkali treatment. Examples of the washing treatment include a method of diluting a rubber component with water and washing, followed by a centrifugal separation treatment, and a method of leaving the rubber to stand and discharging the aqueous phase and taking out the rubber component. When centrifuging, it is first diluted with water so that the rubber content of the natural rubber latex is 5 to 40% by mass, preferably 10 to 30% by mass. Then, it may be centrifuged at 5000 to 10000 rpm for 1 to 60 minutes, and washing may be repeated until a desired phosphorus content is obtained. Also, when the rubber is floated by standing, the addition of water and stirring may be repeated until the desired phosphorus content is obtained. After the washing treatment is completed, the modified natural rubber is obtained by drying.

The content of the modified natural rubber in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 15% by mass or more. If it is less than 10% by mass, there is a tendency that it is difficult to obtain an effect of improving fuel efficiency and wet grip performance. The content of the modified natural rubber is preferably 40% by mass or less, more preferably 30% by mass or less. If it exceeds 40% by mass, the wet grip performance tends to decrease.

Examples of rubber components that can be used in addition to the copolymer and the modified natural rubber include diene rubbers. Natural rubber (NR) and diene synthetic rubber can be used as the diene rubber. Examples of the diene synthetic rubber include isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), and acrylonitrile butadiene. Examples thereof include rubber (NBR), chloroprene rubber (CR), and butyl rubber (IIR). Among these, BR and SBR are preferable because of low fuel consumption and wet grip performance, and it is more preferable to use BR and SBR together with the copolymer and the modified natural rubber. These rubber components may be used alone or in combination of two or more.

The content of BR in 100% by mass of the rubber component is preferably 1% by mass or more, more preferably 5% by mass or more, and preferably 25% by mass or less, more preferably 15% by mass or less. Within the above range, low fuel consumption and wet grip performance can be obtained in a well-balanced manner.

The content of SBR in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 40% by mass or more, and preferably 85% by mass or less, more preferably 75% by mass or less, still more preferably. 65% by mass or less, particularly preferably 55% by mass or less. Within the above range, low fuel consumption and wet grip performance can be obtained in a well-balanced manner.

(silica)
The rubber composition of the present invention preferably contains silica as a reinforcing agent. Dispersion of silica is promoted by the copolymer, and the effect of improving fuel economy and wet grip performance can be enhanced. Silica that can be used is not particularly limited, and those commonly used in the tire industry can be used. Silica may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of silica is preferably 50 m ² / g or more, more preferably 80 m ² / g or more, and preferably 300 m ² / g or less, more preferably 250 m ² / g. It is as follows. Silica having a nitrogen adsorption specific surface area of less than 50 m ² / g has a small reinforcing effect and tends to decrease the wear resistance, and silica exceeding 300 m ² / g has poor dispersibility, increases hysteresis loss, and has low fuel consumption. Tends to decrease.
In addition, the nitrogen adsorption specific surface area by the BET method of a silica can be measured by the method based on ASTM D3037-81.

The content of silica is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and preferably 150 parts by mass or less, more preferably 100 parts by mass or less, with respect to 100 parts by mass of the rubber component. . If the silica content is less than 5 parts by mass, the wear resistance tends to be insufficient. On the other hand, if the silica content exceeds 150 parts by mass, the silica is difficult to disperse, and the workability and fuel efficiency are low. There is a tendency to get worse.

(Silane coupling agent)
In the present invention, it is preferable to use a silane coupling agent together with silica. The silane coupling agent is not particularly limited, and those conventionally used in the tire field can be used. For example, sulfide-based, mercapto-based, vinyl-based, amino-based, glycidoxy-based, nitro-based, chloro-based silane coupling Agents and the like. Among them, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, etc. A sulfide system can be preferably used. From the viewpoint of the effect of improving reinforcing properties, bis (3-triethoxysilylpropyl) tetrasulfide and 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide are preferable. These silane coupling agents may be used alone or in combination of two or more.

The content of the silane coupling agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of silica. When the content of the silane coupling agent is less than 1 part by mass, the viscosity of the unvulcanized rubber composition tends to be high, and the processability tends to deteriorate. Further, the content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less with respect to 100 parts by mass of silica. When the content of the silane coupling agent exceeds 20 parts by mass, the blending effect of the silane coupling agent as much as the content cannot be obtained, and the cost tends to be high.

(Anti-aging agent)
The rubber composition of the present invention can contain an anti-aging agent. As the anti-aging agent, amine-based, phenol-based, and imidazole-based compounds, carbamic acid metal salts, waxes, and the like can be appropriately selected and used.

(Softener)
The rubber composition of the present invention can contain a softening agent. Examples of the softener include petroleum softeners, fatty oil softeners, fatty acids and the like. The content of the softening agent is preferably 100 parts by mass or less with respect to 100 parts by mass of the rubber component because there is little risk of reducing wet grip performance.

(Vulcanizing agent)
The rubber composition of the present invention can contain a vulcanizing agent. As the vulcanizing agent, an organic peroxide, a sulfur vulcanizing agent, or the like can be used. Of these, a sulfur-based vulcanizing agent is preferable and sulfur is more preferable from the viewpoint that the effects of the present invention can be obtained satisfactorily.

(Vulcanization accelerator)
The rubber composition of the present invention can contain a vulcanization accelerator. Examples of the vulcanization accelerator include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine, aldehyde-ammonia, imidazoline, and xanthate vulcanization accelerators. Is mentioned. These may be used alone or in combination of two or more.

(Vulcanization aid)
The rubber composition of the present invention can contain a vulcanization aid. As the vulcanization aid, stearic acid, zinc oxide (zinc white) or the like can be used.

(Other ingredients)
In the rubber composition of the present invention, various reinforcing agents, various oils, plasticizers, coupling agents, etc., various compounding agents and additives compounded for tires or general rubber compositions can be blended. . Moreover, the content of these compounding agents and additives can also be set to general amounts.

The rubber composition of the present invention can be produced by a conventionally known production method, and the production method is not limited. For example, it can be produced by kneading each of the above components using a kneading machine such as a Banbury mixer or a kneading roll under ordinary methods and conditions.

By using the rubber composition of the present invention thus obtained, a pneumatic tire having improved fuel economy and wet grip performance in a well-balanced manner can be obtained. The rubber composition can be used for each member of a tire, and in particular, can be suitably used for a tread, a sidewall, and the like.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition.
That is, by extruding a rubber composition containing the above components in accordance with the shape of a tread or the like at an unvulcanized stage, and molding it with a tire molding machine by a normal method along with other tire members, Form an unvulcanized tire. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a pneumatic tire.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used in the synthesis, polymerization, and HPNR preparation will be described together. In addition, the chemical | medical agent refine | purified according to the usual method as needed.
Natural rubber latex: Field latex Emar-E27C obtained from Muhibah Lateks, Inc. Emar-E27C (polyoxyethylene lauryl ether sulfate sodium) manufactured by Kao Corporation
NaOH: Wako Pure Chemical Industries, Ltd. Formic acid: Wako Pure Chemical Industries, Ltd. Sodium carbonate: Wako Pure Chemical Industries, Ltd. DMF: Kanto Chemical Co., Ltd. N, N-dimethylformamide sodium hydride: Kanto Chemical Co., Ltd. Triethylene glycol monobutyl ether: Kanto Chemical Co., Ltd. 4-chloromethylstyrene: Wako Pure Chemical Industries, Ltd. Octaethylene glycol monobutyl ether: Aldrich Corporation Toluene: Kanto Chemical Co., Ltd. 4- Vinyl benzaldehyde: Sigma-Aldrich 1-butanol: Kanto Chemical Co., Ltd. p-toluenesulfonic acid: Kanto Chemical Co., Ltd. t-butylcatechol: Kanto Chemical Co., Ltd. Ethylene glycol: Kanto Chemical Co., Ltd. n -Hexane: styrene manufactured by Kanto Chemical Co., Ltd .: 1,3-butadiene manufactured by Kanto Chemical Co., Ltd .: tetra manufactured by Tokyo Chemical Industry Co., Ltd. Tylethylenediamine: n-butyllithium manufactured by Kanto Chemical Co., Ltd .: 1.6M n-butyllithium hexane solution 2,6-di-tert-butyl-p-cresol manufactured by Kanto Chemical Co., Ltd. Nocrack 200 manufactured by KK
Denaturant (1): 3- (N, N-dimethylamino) propyltrimethoxysilane manufactured by AMAX Co., Ltd. Modifier (2): 3-glycidoxypropyltrimethoxysilane manufactured by AMAX Co., Ltd.

<Preparation of HPNR (1)>
After adjusting solid content concentration (DRC) of natural rubber latex to 30% (w / v), 25 g of 10% Emar-E27C aqueous solution and 50 g of NaOH aqueous solution are added to 1000 g of natural rubber latex (wet state), A saponification reaction was carried out at room temperature for 48 hours to obtain a saponified natural rubber latex. Water was added to this latex to dilute it to a rubber concentration of 15% (w / v), and then formic acid was added with slow stirring to adjust the pH to 4.0 for aggregation.
The agglomerated rubber is pulverized, dipped in a 1% aqueous sodium carbonate solution at room temperature for 5 hours, pulled up, repeatedly washed with 1000 ml of water, and then dried at 90 ° C. for 4 hours to obtain a solid rubber (HPNR (1)). It was.

<Preparation of HPNR (2)>
A solid rubber (HPNR (2)) was obtained in the same manner as HPNR (1) except that the amount of NaOH aqueous solution was changed to 25 g.

<Preparation of HPNR (3)>
After adding water to the saponified natural rubber latex and diluting it to a rubber concentration of 15% (w / v), adding formic acid with slow stirring, adjusting the pH to 4.0 and agglomerating until HPNR It carried out like (1).
Next, the agglomerated rubber was pulverized, washed with 1000 ml of water without being immersed in a 1% aqueous sodium carbonate solution, and then dried at 90 ° C. for 4 hours to obtain a solid rubber (HPNR (3)).

About HPNR (1)-(3) and TSR, the nitrogen content, phosphorus content, and gel content rate were measured by the method shown below. The results are shown in Table 1.

(Measurement of nitrogen content)
The nitrogen content was measured using CHN CORDER MT-5 (manufactured by Yanaco Analytical Industries). For the measurement, first, a calibration curve for determining the nitrogen content was prepared using antipyrine as a standard substance. Next, about 10 mg of each solid rubber or TSR was weighed, and an average value was obtained from the measurement results of three times to obtain the nitrogen content of the sample.

(Measurement of phosphorus content)
The phosphorus content was determined using an ICP emission spectrometer (ICPS-8100, manufactured by Shimadzu Corporation).

(Measurement of gel content)
A raw rubber sample 70.00 mg cut to 1 mm × 1 mm was weighed, 35 mL of toluene was added thereto, and the mixture was allowed to stand in a cool dark place for 1 week. Subsequently, centrifugation was performed to precipitate a gel component insoluble in toluene, the soluble component of the supernatant was removed, and only the gel component was solidified with methanol, and then dried and the mass was measured. The gel content (%) was determined by the following formula.
Gel content (mass%) = [mass mg after drying / mg of initial sample] × 100

As shown in Table 1, HPNR (1) to (3) had a reduced nitrogen content, phosphorus content, and gel content as compared to TSR. Moreover, when HPNR (1) and (3) were compared, it turned out that nitrogen content, phosphorus content, and gel content rate can be reduced by immersing in sodium carbonate aqueous solution.

<Synthesis of Compound Represented by General Formula (I)>
(Compound A)
To a three-necked flask thoroughly purged with nitrogen, 100 mL of DMF and 1.8 g of sodium hydride were added, and 13 g of triethylene glycol monobutyl ether was added dropwise at 0 ° C. After stirring at room temperature for 1 hour, it was cooled again to 0 ° C., 7.5 g of 4-chloromethylstyrene was added dropwise, and the mixture was stirred as it was for 1 hour. A saturated aqueous ammonium chloride solution was added to the resulting solution, and purification was performed by extraction, concentration, and column purification to obtain Compound A represented by the following structural formula. (R ¹ = methylene group, R ² = ethylene group, R ³ = n-butyl group, r = 3)

(Compound B)
Compound B represented by the following structural formula was obtained by the same formulation as Compound A except that 22 g of octaethylene glycol monobutyl ether was added instead of triethylene glycol monobutyl ether. (R ¹ = methylene group, R ² = ethylene group, R ³ = n-butyl group, r = 8)

<Synthesis of Compound Represented by General Formula (II)>
(Compound C)
100 mL of toluene, 5.3 g of 4-vinylbenzaldehyde, 8.9 g of 1-butanol, 5 mg of p-toluenesulfonic acid and 1 mg of t-butylcatechol were added to a three-necked flask thoroughly purged with nitrogen, and refluxed at 110 ° C. for 2 hours. I let you. Thereafter, the resulting solution was washed with an aqueous sodium hydrogen carbonate solution, dried over magnesium sulfate, filtered, concentrated, and further purified by distillation under reduced pressure to obtain compound C (4-vinylbenzaldehyde dibutyl acetal) represented by the following structural formula. Obtained. (R ⁴ , R ⁵ = n-butyl group, R ⁶ = hydrogen atom)

(Compound D)
Compound D (4-vinylbenzaldehyde ethylene acetal) represented by the following structural formula was obtained by the same formulation as Compound C, except that 4.1 g of ethylene glycol was added instead of 1-butanol. (R ⁴ , R ⁵ = linked ethylene group, R ⁶ = hydrogen atom)

<Analysis of copolymer>
The copolymer obtained as described below was analyzed by the following method.

(Measurement of weight average molecular weight Mw)
The weight average molecular weight Mw of the copolymer is a gel permeation chromatograph (GPC) (GPC-8000 series manufactured by Tosoh Corp., detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M manufactured by Tosoh Corp.) It calculated | required by standard polystyrene conversion based on the measured value by.

(Structural identification of copolymer)
The structure of the copolymer was identified using a JNM-ECA series device manufactured by JEOL Ltd. From the measurement results, the compounds represented by general formula (I) (compound A, compound B), the compounds represented by general formula (II) (compound C, compound D), styrene, and 1, The content of 3-butadiene was calculated.

<Synthesis of copolymer>
(Copolymer (1))
To a heat-resistant container sufficiently purged with nitrogen, 1500 mL of n-hexane, 100 mmol of styrene, 800 mmol of 1,3-butadiene, 0.2 mmol of tetramethylethylenediamine, and 0.12 mmol of n-butyllithium were added and stirred at 0 ° C. for 48 hours. Thereafter, alcohol was added to stop the reaction, and 1 g of 2,6-di-tert-butyl-p-cresol was added to the reaction solution, and then copolymer (1) was obtained by reprecipitation purification. As a result of analysis, the weight average molecular weight Mw was 470,000, and the styrene content was 19% by mass.

(Copolymer (2))
To a heat-resistant container sufficiently substituted with nitrogen, add 1500 mL of n-hexane, 100 mmol of styrene, 800 mmol of 1,3-butadiene, 2.5 mmol of compound A, 2.5 mmol of compound C, 0.2 mmol of tetramethylethylenediamine, and 0.12 mmol of n-butyllithium. And stirred at 0 ° C. for 48 hours. Thereafter, 0.15 mmol of the modifying agent (1) was added and stirred at 0 ° C. for 1 hour. Thereafter, alcohol was added to stop the reaction, and 1 g of 2,6-di-tert-butyl-p-cresol was added to the reaction solution, and then copolymer (2) was obtained by reprecipitation purification. As a result of the analysis, the weight average molecular weight Mw was 500,000, the compound A content was 0.7% by mass, the compound C content was 0.7% by mass, and the styrene content was 19% by mass.

(Copolymer (3))
A copolymer (3) was obtained by the same formulation as the copolymer (2) except that the modifier (2) was added instead of the modifier (1).
As a result of the analysis, the weight average molecular weight Mw was 490,000, the compound A content was 0.7% by mass, the compound C content was 0.8% by mass, and the styrene content was 20% by mass.

(Copolymer (4))
Instead of compound C, copolymer (4) was obtained by the same formulation as copolymer (2) except that 2.5 mmol of compound D was added. As a result of the analysis, the weight average molecular weight Mw was 460,000, the compound A content was 0.7% by mass, the compound D content was 0.5% by mass, and the styrene content was 20% by mass.

(Copolymer (5))
Instead of compound A, copolymer (5) was obtained by the same formulation as copolymer (4) except that 2.5 mmol of compound B was added.
As a result of the analysis, the weight average molecular weight Mw was 500,000, the compound B content was 0.7% by mass, the compound D content was 0.6% by mass, and the styrene content was 19% by mass.

(Copolymer (6))
A copolymer (6) was obtained by the same formulation as the copolymer (2) except that styrene was not added. As a result of the analysis, the weight average molecular weight Mw was 560,000, the compound A content was 0.9% by mass, and the compound C content was 0.8% by mass.

(Copolymer (7))
A copolymer (7) was obtained by the same formulation as the copolymer (2) except that 8 mmol of tetramethylethylenediamine and 5 mmol of n-butyllithium were added. As a result of the analysis, the weight average molecular weight Mw was 20,000, the compound A content was 0.8% by mass, the compound C content was 1.1% by mass, and the styrene content was 20% by mass.

The monomer components, modifiers, and weight average molecular weight Mw of the copolymers (1) to (7) are summarized in Table 2.

<Examples and Comparative Examples>
Below, various chemical | medical agents used by the Example and the comparative example are demonstrated.
NR: TSR
BR: Ubepol BR150B manufactured by Ube Industries, Ltd.
SBR: SL574 manufactured by JSR Corporation
HPNR (1) to (3): Prepared by the above method Copolymers (1) to (7): Synthetic silica by the above method: Ultrasil VN3 (N ₂ SA: 175 m ² / g) manufactured by Degussa
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Anti-aging agent: NOCRACK 6C (N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Stearic acid: Zinc stearate manufactured by NOF Corporation: Zinc Hua No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. (1): Ouchi Shinsei Chemical Noxeller CZ made by Kogyo Co., Ltd.
Vulcanization accelerator (2): Noxeller D manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

According to the formulation shown in Table 3, the chemicals were kneaded and blended to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized at 170 ° C. for 15 minutes to obtain a vulcanized rubber composition.
Further, the unvulcanized rubber composition is formed into a tread shape and bonded together with other tire members to form an unvulcanized tire, press vulcanized at 170 ° C. for 10 minutes, and a test tire ( Size 195 / 65R15) was produced.
The resulting vulcanized rubber composition and test tire were evaluated for fuel economy and wet grip performance by the following test methods.

<Evaluation items and test methods>
(Low fuel consumption)
The obtained vulcanized rubber composition was measured for tan δ at a dynamic strain amplitude of 1%, a frequency of 10 Hz, and a temperature of 50 ° C. using a spectrometer manufactured by Ueshima Seisakusho. And the measurement result was displayed as an index according to the following formula. The larger the index, the lower the rolling resistance and the better the fuel efficiency.
(Low fuel consumption index) = (tan δ of Comparative Example 5) / (tan δ of each formulation) × 100

(Wet grip performance (1))
Wet grip performance was evaluated using a flat belt friction tester (FR5010 type) manufactured by Ueshima Seisakusho. A cylindrical rubber test piece having a width of 20 mm and a diameter of 100 mm made of the above vulcanized rubber composition was used as a sample, and the slip ratio of the sample with respect to the road surface was 0 to 0 at a speed of 20 km / hour, a load of 4 kgf, and a road surface temperature of 20 ° C. The maximum value of the friction coefficient detected at that time was read up to 70%. And the measurement result was displayed as an index according to the following formula. A larger index indicates better wet grip performance.
(Wet grip performance (1) index) = (maximum friction coefficient of each formulation) / (maximum friction coefficient of Comparative Example 5) × 100

(Wet grip performance (2))
On a test course with wet water and wet road surface, the test tire is mounted on a 2000 cc domestic FR vehicle, braked at a speed of 70 km / h, and the distance traveled between braking the tire and stopping (Brake distance) was measured. And the measurement result was displayed as an index according to the following formula. A larger index indicates better wet grip performance.
(Wet grip performance (2) index) = (braking distance of comparative example 5) / (braking distance of each formulation) × 100

As shown in Table 3, a copolymer obtained by copolymerizing 1,3-butadiene and a specific compound, having a terminal modified with a specific modifier, and having a weight average molecular weight Mw within a specific range; In the examples including the modified natural rubber having a phosphorus content of a specific amount or less, the fuel economy and wet grip performance were improved in a well-balanced manner as compared with the comparative example. In Comparative Examples 2 and 4, since a copolymer having a weight average molecular weight Mw outside the specific range was blended, the fuel economy was greatly inferior to the Examples.

From the comparison of Comparative Examples 1, 5, 6 and Example 1, and the comparison of Comparative Examples 3, 5, 6 and Example 6, it is possible to reduce fuel consumption by using the copolymer and the modified natural rubber together. It was found that the performance and wet grip performance can be improved synergistically.

Claims (8)

It is obtained by copolymerizing 1,3-butadiene, a compound represented by the following general formula (I), and a compound represented by the following general formula (II), and the terminal is selected from the group consisting of nitrogen, oxygen and silicon A copolymer having a weight average molecular weight Mw of 1.0 × 10 ^{5 to} 2.5 × 10 ⁶ , modified with a modifier having a functional group containing at least one kind of atom,
A tire rubber composition comprising a modified natural rubber having a phosphorus content of 200 ppm or less.

^(Wherein, R 1 to R ³ are, .r representing the hydrocarbon radical is an integer.)

(In the formula, R ⁴ and R ⁵ represent a hydrocarbon group. R ⁴ and R ⁵ may be bonded to each other. R ⁶ represents a hydrogen atom or a hydrocarbon group.) The copolymer is obtained by copolymerizing styrene together with at least the 1,3-butadiene, the compound represented by the general formula (I), and the compound represented by the general formula (II). The rubber composition for tires according to 1. In the general formula (I), the hydrocarbon group represented by R ¹ , R ² and R ³ has an integer of 1 to 10 carbon atoms and r is an integer of 1 to 30, in the general formula (II), R ⁴ , The rubber composition for tires according to claim 1 or 2, wherein the hydrocarbon group represented by R ⁵ and R ⁶ has 1 to 10 carbon atoms. The content of the compound represented by the general formula (I) in the copolymer is 0.05 to 35% by mass, and the content of the compound represented by the general formula (II) is 0.05 to 35% by mass. The tire rubber composition according to any one of claims 1 to 3. The tire rubber composition according to any one of claims 1 to 4, wherein the modifier is a compound represented by the following general formula (III) or the following general formula (IV).

(Wherein R ⁷ , R ⁸ and R ⁹ are the same or different and each represents an alkyl group, an alkoxy group, a silyloxy group, a carboxyl group, a mercapto group, or a derivative thereof. R ¹⁰ and R ¹¹ are the same or different. And represents a hydrogen atom or an alkyl group, and n represents an integer.)

(In formula, R <^12> , R <^13> and R < ¹⁴ > are the same or different, and represent an alkyl group, an alkoxy group, a silyloxy group, a carboxyl group, a mercapto group, or derivatives thereof. R < ¹⁵ > represents a cyclic ether group. p and q represent integers.) The tire rubber composition according to any one of claims 1 to 5, wherein the nitrogen content of the modified natural rubber is 0.3 mass% or less. The rubber composition for tires according to any one of claims 1 to 6, wherein in 100% by mass of the rubber component, the content of the copolymer is 5% by mass or more and the content of the modified natural rubber is 10% by mass or more. object. The pneumatic tire produced using the rubber composition in any one of Claims 1-7.