JP2005171034A - Rubber composition and tire using the same and used for passenger car - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition which has both low heat generation and wet braking property and has excellent crash resistance and abrasion resistance. <P>SOLUTION: This rubber composition comprising a rubber component and a filler containing at least silica is characterized in that the rubber component contains (a) ≥10 mass% of a modified styrene-butadiene copolymer rubber prepared by reacting the polymerization-active terminal of a styrene-butadiene copolymer having a hydrogen atom or a nitrogen-containing group at one terminal and a polymerization-active terminal as the other terminal with an imino group-containing hydrocarbyloxysilane compound having a specific structure, and (b) ≥10 mass% of styrene-butadiene copolymer rubber having a glass transition point of ≥-35°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rubber composition and a tire for a passenger car using the rubber composition, and particularly relates to a rubber composition that achieves both low heat buildup and wet braking performance and is excellent in fracture resistance and wear resistance.

  In recent years, there has been an increasing demand for lower fuel consumption of automobiles, and a method for reducing the fuel consumption of automobiles includes applying a low heat-generating rubber composition to tires. Here, in order to reduce the heat build-up of the rubber composition, the amount of carbon black generally blended as a filler is reduced, or the carbon black used is reduced in grade (in terms of nitrogen adsorption specific surface area and DBP oil absorption). For example, a low carbon black may be applied), or the amount of oil blended as a softening agent may be reduced.

  However, if the amount of carbon black compounded in the rubber composition is reduced or the grade of carbon black to be used is lowered, the fracture characteristics and wear resistance of the rubber composition are lowered. Moreover, if the compounding quantity of the oil component mix | blended with a rubber composition is reduced, the workability | operativity in the manufacture process of a rubber composition will deteriorate remarkably.

  Further, in recent years, there has been a demand for improvement of tire braking performance, particularly wet braking performance. As a method of improving tire wet braking performance, a rubber composition containing an inorganic filler such as silica is used for a tire tread. It is possible to apply.

  However, the inorganic filler has a lower interaction with the rubber component serving as a matrix of the rubber composition than carbon black, and the reinforcing effect on the rubber composition is small. For this reason, when a rubber composition containing an inorganic filler is used for a tire tread, the fracture characteristics and wear resistance of the tire are reduced.

  Furthermore, when it is required to improve the low heat buildup and wet braking performance of the tire, it is necessary to limit the amount of the mixture while using an inorganic filler. End up.

  On the other hand, a conjugated diene-vinyl aromatic compound in which the terminal is modified with a tin compound as a rubber component of the rubber composition as a method for achieving both fracture resistance, abrasion resistance and low heat build-up of the rubber composition containing carbon black A method using a copolymer (see Patent Document 1), a method using a conjugated diene-vinyl aromatic compound copolymer whose terminal is modified with an amino group-containing compound as a rubber component of a rubber composition (see Patent Document 2), and the like. As is known, these methods cannot improve the wet braking performance of the rubber composition. Moreover, even if these methods are applied to a rubber composition containing silica, the effect cannot be sufficiently exhibited.

  In addition, as a method of achieving both fracture resistance, abrasion resistance and low heat build-up of a rubber composition containing silica, a conjugated diene system in which a terminal is modified with an imino group-containing hydrocarbyloxysilane compound as a rubber component of the rubber composition Although a method using a polymer (see Patent Documents 3 to 5) has been proposed, the method is not sufficient in improving the wet braking performance of the rubber composition, and has low exothermic property, fracture resistance, and The effect of improving wear resistance was not sufficient.

Japanese Patent Publication No. 5-87530 JP 62-207342 A JP 2001-131340 A JP 2001-131343 A JP 2001-131345 A

  Accordingly, an object of the present invention is to provide a rubber composition that solves the above-described problems of the prior art, achieves both low heat buildup and wet braking properties, and is excellent in fracture resistance and wear resistance. Another object of the present invention is to provide a passenger car tire that uses the rubber composition in a tread and is excellent in low heat build-up, wet braking, breakage resistance and wear resistance.

  As a result of intensive studies to achieve the above object, the present inventor has found that a rubber composition containing silica as a filler has a styrene-butadiene copolymer modified with a hydrocarbyloxysilane compound containing an imino group as a rubber component. By using a combined rubber and a styrene-butadiene copolymer rubber having a high glass transition point, it is possible to improve both fracture resistance and wear resistance while achieving both low heat buildup and wet braking performance of the rubber composition. The headline and the present invention have been completed.

（式中、Ｒ¹及びＲ²は、それぞれ独立して炭素数１〜１８の一価の炭化水素基で；Ａは炭素数１〜２０の二価の炭化水素基で；Ｒ³及びＲ⁴は、それぞれ独立して水素原子又は炭素数１〜１８の一価の炭化水素基で、但し、該一価の炭化水素基は置換若しくは無置換のアミノ基及び／又はエーテル基を有していてもよく、また、Ｒ³及びＲ⁴は互いに結合して環構造を形成してもよく；ｎは１〜３の整数である）で表されるイミノ基含有ヒドロカルビルオキシシラン化合物を反応させてなる変性スチレン-ブタジエン共重合体ゴム（ａ）10質量％以上と、
ガラス転移点(Ｔg)が-35℃より高いスチレン-ブタジエン共重合体ゴム（ｂ）10質量％以上とを含むことを特徴とする。 That is, the rubber composition of the present invention is a rubber composition obtained by blending a rubber component with a filler containing at least silica.
The rubber component is
The styrene-butadiene copolymer having a hydrogen atom or a nitrogen-containing group at one end and the other end being a polymerization active end has the following general formula (I):

Wherein R ¹ and R ² are each independently a monovalent hydrocarbon group having 1 to 18 carbon atoms; A is a divalent hydrocarbon group having 1 to 20 carbon atoms; R ³ and R ⁴ Are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, provided that the monovalent hydrocarbon group has a substituted or unsubstituted amino group and / or ether group. And R ³ and R ⁴ may be bonded to each other to form a ring structure; n is an integer of 1 to 3) and is reacted with an imino group-containing hydrocarbyloxysilane compound. Modified styrene-butadiene copolymer rubber (a) 10% by mass or more,
The styrene-butadiene copolymer rubber (b) having a glass transition point (Tg) higher than -35 ° C (10%) is contained.

  In a preferred example of the rubber composition of the present invention, the amount of silica is 10 to 100 parts by mass with respect to 100 parts by mass of the rubber component. In this case, low exothermic property and wet braking property can be greatly improved without deteriorating the workability of the rubber composition.

  In another preferable example of the rubber composition of the present invention, the content of the silica in the filler is 10 to 100% by mass. In this case, the effect of blending the modified styrene-butadiene copolymer rubber (a) is sufficiently exerted, and the low exothermic property, wet braking property, fracture resistance and wear resistance of the rubber composition are greatly improved.

  In another preferred embodiment of the rubber composition of the present invention, the rubber component further contains natural rubber. Here, in the rubber composition of the present invention, the rubber component contains 10 to 90% by mass of the modified styrene-butadiene copolymer rubber (a) and the styrene-butadiene copolymer rubber (b) 10 to 90. It is preferable to contain a mass% and natural rubber 0-80 mass%.

  The passenger car tire of the present invention is characterized in that the rubber composition is used in a tread.

  According to the present invention, a styrene-butadiene copolymer rubber (a) in which silica is blended as a filler and a terminal is modified with an imino group-containing hydrocarbyloxysilane compound as a rubber component, and a styrene-butadiene copolymer having a high glass transition point. A rubber composition using the combined rubber (b), which has both low heat build-up and wet braking properties and improved fracture resistance and wear resistance, can be provided. Moreover, the tire for passenger cars which used this rubber composition for the tread and was excellent in low heat build-up property, wet-braking property, destruction resistance, and abrasion resistance can be provided.

  The present invention is described in detail below. The rubber composition of the present invention has a hydrogen atom or nitrogen-containing group at one end and the above-mentioned general formula (I) at the polymerization active end of the styrene-butadiene copolymer whose other end is a polymerization active end. Modified styrene-butadiene copolymer rubber (a) obtained by reacting an imino group-containing hydrocarbyloxysilane compound represented by the formula (10) and a styrene-butadiene copolymer rubber having a glass transition point higher than -35 ° C ( b) A rubber component containing 10% by mass or more is blended with a filler containing at least silica. By blending the rubber composition with styrene-butadiene copolymer rubber (b) having a high glass transition point as a rubber component, the glass transition point of the rubber composition is increased, and the tan δ at 0 ° C. of the rubber composition is increased. Thus, wet braking performance is improved. In addition, by using the terminal-modified styrene-butadiene copolymer rubber (a) as a rubber component, an increase in tan δ at 60 ° C. of the rubber composition is suppressed, and low exothermic property of the rubber composition is ensured. Can do. Furthermore, by using the modified styrene-butadiene copolymer rubber (a) as a rubber component while blending silica as a filler, the interaction between the silica and the rubber component is increased, and a sufficient reinforcing effect is exhibited. The fracture resistance and wear resistance of the rubber composition can be improved. Furthermore, by using the modified styrene-butadiene copolymer rubber (a) as the rubber component and the styrene-butadiene copolymer rubber (b) having a high glass transition point as a rubber component while using silica as a filler, a modified styrene- The effect of improving the low heat buildup, fracture resistance and wear resistance of the rubber composition of the butadiene copolymer rubber (a) is further exhibited, and wet braking performance can be greatly improved.

  The rubber composition of the present invention contains the modified styrene-butadiene copolymer rubber (a) as a rubber component, and the content of the modified styrene-butadiene copolymer rubber (a) in the rubber component is 10% by mass. That's it. If the content of the modified styrene-butadiene copolymer rubber (a) in the rubber component is less than 10% by mass, the effect of improving the low heat buildup, fracture resistance and wear resistance of the rubber composition will not be sufficiently exerted. .

  The modified styrene-butadiene copolymer rubber (a) is a styrene-butadiene copolymer having a hydrogen atom or a nitrogen-containing group at one end and a polymerization active end at the other end. It is obtained by modification with an imino group-containing hydrocarbyloxysilane compound represented by The styrene-butadiene copolymer can be produced, for example, by anionic polymerization of 1,3-butadiene and styrene using an organic lithium compound as a polymerization initiator. As the organolithium compound, hydrocarbyl lithium and lithium amide compound are preferable. When hydrocarbyl lithium is used, a styrene-butadiene copolymer having a hydrogen atom at one end and a polymerization active end is obtained. When a lithium amide compound is used, a styrene-butadiene copolymer having a nitrogen-containing group at one end and a polymerization active end at the other end is obtained.

  As the hydrocarbyl lithium, those having a hydrocarbyl 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-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. Of these, n-butyllithium is preferable.

  Examples of the lithium amide compound include lithium hexamethylene imide, lithium pyrrolidide, lithium piperidide, lithium heptamethylene imide, lithium dodecamethylene imide, lithium dimethyl amide, lithium diethyl amide, lithium dibutyl amide, and lithium dipropyl amide. , Lithium diheptylamide, lithium dihexylamide, lithium dioctylamide, lithium di-2-ethylhexylamide, lithium didecylamide, lithium-N-methylpiperazide, lithium ethylpropylamide, lithium ethylbutyramide, lithium methylbutyramide, lithium ethylbenzyl Amide, lithium methylphenethyl amide, etc., among these, lithium hexamethylene imide, lithium pyrrolidide Cyclic lithium amides such as lithium piperidide, lithium heptamethylene imide and lithium dodecamethylene imide are preferable, and lithium hexamethylene imide and lithium pyrrolidide are particularly preferable.

  There is no restriction | limiting in particular as a method of manufacturing a styrene-butadiene copolymer by anionic polymerization in presence of the said organic lithium compound, A conventionally well-known method can be used. Specifically, in an organic solvent inert to the reaction, an organic lithium compound is used as a polymerization initiator, and 1,3-butadiene and styrene are anionically polymerized in the presence of a randomizer if desired, thereby styrene-butadiene. A copolymer is obtained. The temperature of the polymerization reaction is usually in the range of -80 to 150 ° C, preferably in the range of -20 to 100 ° C. The polymerization reaction can also be carried out under generated pressure, and is preferably operated at a pressure sufficient to keep 1,3-butadiene and styrene in a substantially liquid phase. The polymerization may be performed at a pressure higher than the generated pressure. For example, the pressure of the polymerization system may be increased by pressurizing the reactor with a gas inert to the polymerization reaction.

  The modified styrene-butadiene copolymer rubber (a) has a styrene-butadiene copolymer having a hydrogen atom or a nitrogen-containing group at one end obtained as described above and the other end being a polymerization active end. It can be obtained by reacting the polymerization active terminal of the polymer with an imino group-containing hydrocarbyloxysilane compound represented by the above general formula (I).

In the formula (I), R ¹ and R ² are each independently a monovalent hydrocarbon group having 1 to 18 carbon atoms. Examples of the monovalent hydrocarbon group include an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, and an aralkyl group having 7 to 18 carbon atoms. Here, the alkyl group and alkenyl group may be linear, branched, or cyclic, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec- Butyl, tert-butyl, pentyl, hexyl, octyl, decyl, dodecyl, cyclopentyl, cyclohexyl, vinyl, propenyl, allyl, hexenyl, octenyl, cyclopentenyl, A cyclohexenyl group etc. are mentioned. The aryl group may have a substituent such as a lower alkyl group on the aromatic ring, and examples thereof include a phenyl group, a tolyl group, a xylyl group, and a naphthyl group. Furthermore, the aralkyl group may have a substituent such as a lower alkyl group on the aromatic ring, and examples thereof include a benzyl group, a phenethyl group, and a naphthylmethyl group.

  In the formula (I), A represents a divalent hydrocarbon group having 1 to 20 carbon atoms. Examples of the divalent hydrocarbon group include an alkylene group having 1 to 20 carbon atoms, an alkenylene group having 2 to 20 carbon atoms, an arylene group having 6 to 20 carbon atoms, an aralkylene group having 7 to 20 carbon atoms, and the like. Among these, an alkylene group having 1 to 20 carbon atoms is preferable. The alkylene group may be linear, branched or cyclic, but is preferably linear. Examples of the linear alkylene group include a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, an octamethylene group, a decamethylene group, and a dodecamethylene group.

In formula (I), n is an integer from 1 to 3, when R ¹ O is more, each R ¹ O may be the same or different from each other, when R ² are a plurality, each R ² May be the same as or different from each other.

In the formula (I), R ³ and R ⁴ are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms. Here, a monovalent hydrocarbon group having 1 to 18 carbon atoms as R ³ and R ⁴ may be substituted or unsubstituted amino group and / or ether groups. R ³ and R ⁴ may be the same as or different from each other, and may be bonded to each other to form a ring structure. The ring structure may be a saturated or unsaturated hydrocarbon ring structure, or may be a saturated or unsaturated heterocyclic structure containing a nitrogen atom and / or an oxygen atom as a heteroatom. Incidentally, monovalent hydrocarbon group having 1 to 18 carbon atoms as R ³ and R ⁴ are the same as the monovalent hydrocarbon group having 1 to 18 carbon atoms described in the above R ¹ and R ^2.

  In the formula (I), the imino group bonded to A includes an ethylideneamino group, 1-methylpropylideneamino group, 1,3-dimethylbutylideneamino group, 1-methylethylideneamino group, 4-N, N- Preferable examples include dimethylaminobenzylideneamino group, cyclohexylideneamino group and the like.

  As the imino group-containing hydrocarbyloxysilane compound of formula (I), specifically, N- (1,3-dimethylbutylidene) -3- (triethoxysilyl) -1-propanamine, N- (1-methyl) Ethylidene) -3- (triethoxysilyl) -1-propanamine, N-ethylidene-3- (triethoxysilyl) -1-propanamine, N- (1-methylpropylidene) -3- (triethoxysilyl) -1-Propanamine, N- [4- (N, N-dimethylamino) benzylidene] -3- (triethoxysilyl) -1-propanamine, N- (cyclohexylidene) -3- (triethoxysilyl) Preferred are trimethoxysilyl compounds, methyldiethoxysilyl compounds, ethyldiethoxysilyl compounds, methyldimethoxysilyl compounds, ethyldimethoxysilyl compounds corresponding to -1-propanamine and these triethoxysilyl compounds. Among these, N- (1-methylpropylidene) -3- (triethoxysilyl) -1-propanamine and N- (1,3-dimethylbutylidene) -3- (triethoxysilyl) -1 -Propanamine is particularly preferred.

  When the imide group-containing hydrocarbyloxysilane compound of the formula (I) is reacted with the polymerization active terminal of the styrene-butadiene copolymer, the amount of the compound of the formula (I) is used for the production of the styrene-butadiene copolymer. The amount is usually 0.25 to 3.0 mol, preferably 0.5 to 1.5 mol, based on 1 mol of the organic lithium compound. If it is less than 0.25 mol, hydrocarbyloxy groups are consumed in the coupling reaction, which is not preferable. On the other hand, if it exceeds 3.0 mol, the excessively used compound of the formula (I) is wasted, and the impurities contained in the compound of the formula (I) deactivate the polymerization active terminal, resulting in substantial modification efficiency. It will decline. The reaction temperature during modification may be the same as the polymerization temperature of the styrene-butadiene copolymer, and is preferably in the range of 30 to 100 ° C. If the temperature of the modification reaction is less than 30 ° C, the viscosity of the polymer tends to increase too much, and if it exceeds 100 ° C, the polymerization active terminal tends to be deactivated.

  There is no particular limitation on the timing and method of adding the compound of the above formula (I) to the polymerization active terminal of the styrene-butadiene copolymer, and the method is generally performed after the polymerization of the styrene-butadiene copolymer. Analysis of the polymer chain terminal modified group of the modified styrene-butadiene copolymer rubber (a) thus obtained can be performed by high performance liquid chromatography (HPLC).

  The compound of the formula (I) has a methyleneamino group in the molecule, and the methyleneamino group has excellent basicity like a tertiary amino group and has few steric hindrances. It can hydrogen bond with the group. When the compound of formula (I) is reacted with the polymerization active terminal of a styrene-butadiene copolymer, a mixture of a nucleophilic substitution product with hydrocarbyloxysilane and an addition reaction product with a methyleneamino group is obtained. It is considered a thing. When the compound of formula (I) undergoes a nucleophilic substitution reaction at the polymerization active terminal of the styrene-butadiene copolymer, the acidic functional group (silanol group) on the silica surface interacts with the introduced methyleneamino group. The dispersibility of silica in the rubber component is improved, and the reinforcing effect by silica is sufficiently exhibited. In addition, when the compound of formula (I) is added to the polymerization active terminal of the styrene-butadiene copolymer, a secondary amino group is formed, and the secondary amino group forms a hydrogen bond with a silanol group on the silica surface. Therefore, the dispersibility of silica in the rubber component is improved, and the reinforcing effect by silica is sufficiently exhibited. Further, the compound of formula (I) has a hydrocarbyloxysilyl group, and the hydrocarbyloxysilyl group introduced into the polymerization active terminal of the styrene-butadiene copolymer undergoes a condensation reaction with a silanol group on the silica surface. An extremely high reinforcing effect is exhibited. In addition, when the imino group bonded to A is an N, N-dimethylaminobenzylideneamino group, the use of carbon black together with silica as a filler enhances the interaction with the carbon black and further enhances the reinforcing effect. Is done.

  The rubber composition of the present invention contains a styrene-butadiene copolymer rubber (b) having a glass transition point higher than −35 ° C. as a rubber component, and the styrene-butadiene copolymer rubber (b) in the rubber component Content is 10 mass% or more. When the content of the styrene-butadiene copolymer rubber (b) in the rubber component is less than 10% by mass, the effect of increasing the glass transition point of the rubber composition is small, and the tan δ at 0 ° C. of the rubber composition is increased. The effect of improving wet braking performance is small. In addition, when the glass transition point of the styrene-butadiene copolymer rubber (b) is −35 ° C. or less, the effect of improving the glass transition point of the rubber composition is small, so that the tan δ at 0 ° C. of the rubber composition is sufficiently high. As a result, the wet braking performance cannot be sufficiently improved. Here, the glass transition point of the styrene-butadiene copolymer rubber (b) is preferably −30 ° C. or higher. In the present invention, the glass transition point can be measured with a differential scanning calorimeter (DSC) or the like.

  The rubber composition of the present invention preferably further contains natural rubber as a rubber component. By blending natural rubber, the mechanical properties of the rubber composition can be improved. The rubber composition of the present invention may also contain other diene rubbers that are usually used in tire rubber compositions as a rubber component.

  The rubber component of the rubber composition of the present invention comprises 10 to 90% by mass of the modified styrene-butadiene copolymer rubber (a), 10 to 90% by mass of the styrene-butadiene copolymer rubber (b) and 0 to 90% of natural rubber. The modified styrene-butadiene copolymer rubber (a) is 40 to 70% by mass, the styrene-butadiene copolymer rubber (b) is 10 to 30% by mass, and natural rubber 5 to 30%. It is more preferable that it contains the mass%. If the content of the styrene-butadiene copolymer rubber (b) in the rubber component exceeds 90% by mass or the content of natural rubber in the rubber component exceeds 80% by mass, the modified styrene-butadiene copolymer The content of the combined rubber (a) is insufficient, and the effect of improving the low heat build-up, wet braking performance, fracture resistance and wear resistance of the rubber composition is not sufficiently exhibited.

  The rubber composition of the present invention contains at least silica as a filler. Here, examples of the silica include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), and the like. The amount of the silica is preferably in the range of 10 to 100 parts by mass, more preferably in the range of 25 to 80 parts by mass with respect to 100 parts by mass of the rubber component. When the blending amount of silica is less than 10 parts by weight with respect to 100 parts by weight of the rubber component, the effect of improving the wet braking performance of the rubber composition is small, and since there is little silica, the modified styrene-butadiene copolymer rubber ( The effect of improving the low exothermic property, fracture resistance and wear resistance of the rubber composition by blending a) is small. On the other hand, when the compounding amount of silica exceeds 100 parts by mass with respect to 100 parts by mass of the rubber component, workability in the production process of the rubber composition is deteriorated, and further, the exothermic property of the rubber composition is increased.

  The rubber composition of the present invention may contain carbon black or the like as a filler in addition to the silica. There is no restriction | limiting in particular as this carbon black, For example, FEF, SRF, HAF, ISAF, SAF etc. can be used. Here, the content of silica in the filler is preferably in the range of 10 to 100% by mass, and more preferably in the range of 25 to 100% by mass. When the proportion of silica in the filler is less than 10% by mass, the modified styrene-butadiene copolymer rubber (a) is blended to improve the low heat buildup, fracture resistance and wear resistance of the rubber composition. In addition, the effect of improving the wet braking performance of the rubber composition is reduced.

  In the rubber composition of the present invention, in addition to the rubber component, silica, carbon black and other fillers, softeners such as process oil, anti-aging agent, vulcanizing agent, vulcanization accelerator, stearic acid, wax, A compounding agent usually used in the rubber industry such as zinc white can be appropriately selected and blended within a range not impairing the object of the present invention. As these compounding agents, commercially available products can be suitably used. The rubber composition of the present invention is a rubber component containing at least the modified styrene-butadiene copolymer rubber (a) and the styrene-butadiene copolymer rubber (b). It can be produced by blending an agent, kneading, heating, extruding and the like.

  The tire for passenger cars of the present invention is characterized by using the rubber composition described above for a tread. The tire of the present invention is not particularly limited except that the above rubber composition is applied to the tread, and can be produced by an ordinary method, and is excellent in low heat buildup, wet braking performance, fracture resistance, and wear resistance. In addition, as gas with which the tire of the present invention is filled, an inert gas such as nitrogen, argon, helium, etc. can be used in addition to air having normal or oxygen partial pressure adjusted.

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

  A rubber composition having a formulation shown in Table 1 was prepared. In addition to the rubber components, fillers, and oils shown in Table 1, compounding agents such as anti-aging agents, vulcanization accelerators, and sulfur were blended in the rubber composition at normal blending ratios. In Table 1, terminal-modified SBR-1 and terminal-modified SBR-2 were produced as follows.

(Method for producing terminal-modified SBR-1)
The method described in Production Example 1 of JP2001-131343A was followed. In a dry and nitrogen-substituted 800 mL pressure-resistant glass container, 300 g of cyclohexane, 40 g of 1,3-butadiene, 10 g of styrene and 0.16 mmol of ditetrahydrofurylpropane are added, and 0.55 mmol of n-butyllithium (BuLi) is further added. Polymerization was carried out at 2 ° C. for 2 hours. The polymerization system was uniform and transparent with no precipitation observed from the start to the end of the polymerization, and the polymerization conversion rate was almost 100%. After completion of the polymerization, 0.55 mmol of N- (1,3-dimethylbutylidene) -3- (triethoxysilyl) -1-propanamine was further added to the polymerization system as an endless modifier, and a modification reaction was performed for 30 minutes. Next, 0.5 mL of a 5% by mass solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol was further added to the polymerization system to stop the reaction, followed by drying by a conventional method and terminal-modified SBR-1 Got. When the microstructure of the terminal-modified SBR-1 was analyzed by an infrared method, the amount of bound styrene was 20.1% by mass and the amount of vinyl bond was 54%. The glass transition point was -42.0 ° C.

(Method for producing terminal-modified SBR-2)
It was produced in the same manner as polymer A in JP-B-5-87530. Nitrogen-substituted 5 L autoclave is charged with 2000 g of degassed cyclohexane, 400 g of 1,3-butadiene, 100 g of styrene and 20 g of tetrahydrofuran, and 6 mmol of tetramethylene-1,4-dilithium is added, and polymerization is carried out at 20 ° C. under heat insulation. went. After the completion of the polymerization, 4 mmol of dibutyldichlorotin was added as an endless modifier to carry out a modification reaction. Next, 2.5 g of di-t-butylcresol was added to stop the reaction, and the solvent was removed and dried by a conventional method to obtain terminal-modified SBR-2. The terminal-modified SBR-2 had a bound styrene content of 20% by mass, a vinyl bond content of 58%, and a tin content of 940 ppm.

  Next, with respect to the obtained rubber composition, elongation at break and tensile strength, tan δ (loss tangent) at 0 ° C. and 60 ° C., and wear resistance were measured by the following methods. The results are shown in Table 1.

(1) Elongation and tensile strength at break A tensile test was performed in accordance with JIS K 6251, and the elongation (Eb) and tensile strength (Tb) at the time of cutting of the vulcanized rubber composition were measured.

(2) Tanδ at 0 ℃ and 60 ℃
Using a viscoelasticity measuring device (manufactured by Rheometrics), tan δ (0 ° C.) and tan δ (60 ° C.) of a rubber composition vulcanized at a temperature of 0 ° C. or 60 ° C., a strain of 5%, and a frequency of 15 Hz were measured. The larger tan δ (0 ° C.), the better the wet braking performance of the rubber composition. In addition, the smaller the tan δ (60 ° C.), the lower the heat buildup of the rubber composition.

(3) Abrasion resistance (rubber composition)
The amount of wear at a slip rate of 60% was measured at room temperature using a Lambourn type wear tester, and the amount of wear of the rubber composition of Comparative Example 1 was shown as an index. It shows that abrasion resistance is so favorable that an index value is large.

  Next, a tire for a passenger car having a size of 175 / 65R15 using the rubber composition as a tread was manufactured. The obtained tire was assembled into a rim, the tire inner pressure was set to 196 kPa, and the low heat generation property, wet braking property, and wear resistance of the tire were evaluated by the following methods. The results are shown in Table 1.

(4) Low exothermic property After rotating the tire on the QC drum for a certain period of time, the temperature of the tire tread portion was measured, and the reciprocal of the temperature of the tread portion of the tire of Comparative Example 1 was displayed as an index. The larger the index value, the lower the temperature and the lower the exothermic property.

(5) Wet braking performance A vehicle equipped with 4 tires tested on a domestic FF vehicle, measuring the braking distance on a wet road surface at an initial speed of 80 km / h on the test course, and mounting the tire of Comparative Example 1 The reciprocal of the braking distance is expressed as an index. The larger the index value, the shorter the braking distance and the better the wet braking performance.

(6) Abrasion resistance (tire)
Four test tires were mounted on a domestic FF vehicle, and a running test was conducted for 50000km in a city area and a mountain slope under the load equivalent to two passengers, and the depth of the remaining tread after driving was measured. In the measurement of the remaining groove, the average value of 10 places on the circumference of the groove near the center was used, and the tire of Comparative Example 1 was set as 100 and displayed as an index. The larger the index value, the smaller the amount of wear and the better the wear resistance.

* 1 Terminal-modified styrene-butadiene copolymer rubber obtained by the method described in Production Example 1 of JP-A-2001-131343, modifier: N- (1,3-dimethylbutylidene) -3- (tri Ethoxysilyl) -1-propanamine [included in imino group-containing hydrocarbyloxysilane compounds of formula (I)].
* 2 End-modified styrene-butadiene copolymer rubber produced in the same manner as Polymer A in JP-B-5-87530, Modifier: Dibutyldichlorotin.
* 3 Oil-extended with 37.5 parts by mass of aroma oil based on 100 parts by mass of JSR, SBR1712, SBR, SBR glass transition point = -56.8 ° C.
* 4 JSR product, SBR0202, glass transition point = -28.5 ℃.
* 5 NIPSEAL AQ (trademark), manufactured by Nippon Silica Kogyo Co., Ltd.

  As is clear from Table 1, terminal-modified SBR-1 [modified styrene-butadiene copolymer rubber (a)], SBR-4 [styrene-butadiene copolymer rubber (b) having a high glass transition point] and silica are used. The blended rubber composition of the example is superior to the rubber composition of Comparative Example 1 in terms of elongation at break and tensile strength (breakage resistance), and has high tan δ at 0 ° C., so wet braking performance is improved. Excellent, tan δ at 60 ° C. was low, so it was excellent in low heat build-up, and was also excellent in wear resistance. In addition, the tire using the rubber composition of the example was superior to the tire of Comparative Example 1 in all of low heat build-up, wet braking properties and wear resistance.

  On the other hand, the rubber composition of Comparative Example 2 containing SBR-4 [styrene-butadiene copolymer rubber (b) having a high glass transition point] and silica but not containing the modified styrene-butadiene copolymer rubber (a) is The elongation at break and the tensile strength (breaking resistance) were inferior to those of Comparative Example 1, the tan δ at 60 ° C. was high, the heat generation was inferior, and the wear resistance was also low. Moreover, the tire using the rubber composition of Comparative Example 2 was inferior to the tire of Comparative Example 1 in low heat buildup and wear resistance. Furthermore, the wet braking performance was also inferior to the tires of the examples.

  Further, the rubber composition of Comparative Example 3 containing terminal-modified SBR-1 [modified styrene-butadiene copolymer rubber (a)] and silica but not containing a styrene-butadiene copolymer rubber (b) having a high glass transition point. The product had a lower tan δ at 0 ° C. than that of Comparative Example 1 and inferior wet braking properties. Further, the tire using the rubber composition of Comparative Example 3 was inferior in wet braking performance to the tire of Comparative Example 1. Furthermore, it was inferior to the tire of an Example also about low heat buildup and abrasion resistance.

Claims (6)

In the rubber composition formed by blending a filler containing at least silica with the rubber component,
The rubber component is
The styrene-butadiene copolymer having a hydrogen atom or a nitrogen-containing group at one end and the other end being a polymerization active end has the following general formula (I):

Wherein R ¹ and R ² are each independently a monovalent hydrocarbon group having 1 to 18 carbon atoms; A is a divalent hydrocarbon group having 1 to 20 carbon atoms; R ³ and R ⁴ Are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, provided that the monovalent hydrocarbon group has a substituted or unsubstituted amino group and / or ether group. And R ³ and R ⁴ may be bonded to each other to form a ring structure; n is an integer of 1 to 3) and is reacted with an imino group-containing hydrocarbyloxysilane compound. Modified styrene-butadiene copolymer rubber (a) 10% by mass or more,
A rubber composition comprising a styrene-butadiene copolymer rubber (b) having a glass transition point higher than -35 ° C (b) of 10% by mass or more.   The rubber composition according to claim 1, wherein the amount of silica is 10 to 100 parts by mass with respect to 100 parts by mass of the rubber component.   The rubber composition according to claim 1, wherein a content of the silica in the filler is 10 to 100% by mass.   The rubber composition according to claim 1, wherein the rubber component further contains natural rubber.   The rubber component comprises 10 to 90% by mass of the modified styrene-butadiene copolymer rubber (a), 10 to 90% by mass of the styrene-butadiene copolymer rubber (b), and 0 to 80% by mass of natural rubber. The rubber composition according to claim 1, comprising:   The tire for passenger cars which used the rubber composition in any one of Claims 1-5 for the tread.