JP2001139730A - Rubber composition for tire tread - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition for tire tread having low electric resistance and well-balanced rolling resistance, abrasion resistance and wet properties at high level. SOLUTION: This rubber composition for tire tread is obtained by compounding >=10 pts.wt. silica-treated carbon black based on 100 pts.wt. rubber component and 2-14 wt.% silane coupling agent based on the silica-treated carbon black wherein the rubber component comprises 70-95 wt.% diene-based rubber and 5-30 wt.% halogenated copolymer rubber obtained by halogenation of isobutylene-p-methylstyrene copolymer rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition for a tire tread. More specifically, the electric resistance is low,
The present invention relates to a rubber composition for a tire tread that can provide a tire having a well-balanced rolling resistance characteristic, abrasion resistance and wet performance.

[0002]

2. Description of the Related Art In recent years, there has been a demand for higher performance of passenger cars, and awareness of the environment has been increasing.

As one of the high-performance automobiles, it is desired to improve wet performance such as braking performance and steering stability performance on wet road surfaces, and to reduce rolling resistance as a result of increased environmental awareness. Rarely, it is desired to achieve both of these performances. In order to achieve both of these performances, a method of blending silica instead of carbon black is often used.

However, when a tread rubber composition using silica is used, the electric resistance becomes high and the flow of static electricity to a road surface becomes insufficient, and as a result, noise is generated from electronic equipment by discharge due to electrostatic breakdown. Or a malfunction may occur in some cases.

Recently, a method using carbon black whose surface is treated with silica has been developed as a method for solving the problem of increasing electric resistance and achieving a balance between wet performance and rolling resistance (Japanese Patent No. 2788212). ,
Japanese Patent Application Laid-Open No. 10-316800) shows that the wet performance is lower than that of silica and the workability is lower than that of silica.

On the other hand, as a technique using a copolymer rubber or the like obtained by halogenating an isomonoolefin-p-alkylstyrene copolymer in a rubber composition for tires, for example, an isomonoolefin-p-alkylstyrene copolymer is prepared by halogenation. By blending carbon black and / or silica with the rubber component blended with the copolymerized rubber,
A technique for improving wet performance without impairing low-temperature performance (Japanese Patent Application Laid-Open No. 9-324069), a rubber component containing a copolymer rubber obtained by halogenating an isomonoolefin-p-alkylstyrene copolymer is specified. By blending carbon black having a dibutyl phthalate oil absorption (DBP) of the above, it is possible to improve wet skid resistance and reduce rolling resistance without deteriorating fracture resistance and wear resistance (Japanese Patent Laid-Open No. 9-241426
JP-A No. 195/1989), a rubber component composed of halogenated butyl rubber, isoprene rubber and / or natural rubber and other diene rubbers, and carbon black and alkylphenol disulfide are blended, thereby deteriorating without deteriorating wear resistance. Technology for improving the properties and wet skid resistance and reducing the rolling resistance (Japanese Patent Application Laid-Open No. 9-241430), from a copolymer and a diene polymer containing an isobutylene unit, a paramethylstyrene unit and a parabromomethylstyrene unit. By blending carbon black with a specific hydrazide compound, a specific thiazole compound and a specific amine derivative,
Without affecting the tan δ value at 0 ° C.
Technology for lowering tan δ value at ° C.
83461, JP-A-8-283462, JP-A-8-283664), isoprene-butadiene copolymer rubber, cis 1,4-polyisoprene, natural rubber, and halogenated isobutylene-p-methylstyrene copolymer As a skeleton rubber component, and in some cases, cis 1,4
-Addition of other additional rubber components such as polybutadiene and styrene-butadiene rubber and reinforcement with silica to obtain a pneumatic rubber tire with excellent static friction characteristics, balanced rolling resistance and abrasion resistance A technique (Japanese Patent Application Laid-Open No. 7-304903) is known.

However, when a copolymer rubber or the like obtained by halogenating an isomonoolefin-p-alkyl ester copolymer is used as a rubber component, generally the wet grip performance and the like are improved, but the abrasion resistance is lowered and other properties are reduced. It is difficult to achieve a good balance with the performance of the above.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and has been made in order to solve the above-mentioned problems.
5% by weight (hereinafter referred to as%) and isobutylene-p-
10 parts or more of silica-treated carbon black and a silane coupling agent are mixed with 100 parts by weight (hereinafter referred to as "parts") of a rubber component composed of 5 to 30% of a halogenated copolymer rubber obtained by halogenating a methylstyrene copolymer rubber. A rubber composition for a tire tread compounded with 2 to 14% with respect to the treated carbon black (Claim 1), and a silica-treated carbon black obtained by treating a surface of carbon black with silica at a ratio of 0.1 to 50%. Certain claim 1
The present invention relates to a rubber composition for a tire tread as described in claim 2.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber component used in the present invention comprises:
It comprises 70 to 95%, preferably 80 to 90%, of a diene rubber and 5 to 30%, preferably 10 to 20% of a halogenated copolymer rubber obtained by halogenating an isobutylene-p-methylstyrene copolymer. If the ratio of the diene rubber in the rubber component is less than 70%, the processability is reduced, and the productivity is reduced. If it exceeds 95%, it is difficult to obtain sufficient wet performance.

As the diene rubber, any diene rubber generally used in rubber compositions for treads can be used. Specific examples thereof include, for example, natural rubber (NR), diene-based synthetic rubber such as isoprene rubber (IR), various styrene-butadiene copolymer rubbers (SBR), butadiene rubber (BR), acrylonitrile-butadiene copolymer rubber (NBR) ), Butyl rubber (I
IR) and the like. These may be used alone or in combination of two or more, for example, as a blend. Of these, NR, IR, SB
It is preferable to use at least one selected from R and BR,
More preferably, the SBR is 55 to 100% and the remaining rubber is 45 to 0%.

As the halogenated copolymer rubber obtained by halogenating the isobutylene-p-methylstyrene copolymer rubber, any of the halogenated copolymer rubbers generally used in rubber compositions for treads can be used. .
The ratio of the paramethylstyrene unit in the isobutylene-p-methylstyrene copolymer rubber is usually 1 to 20.
%, And the amount of halogen (chlorine, bromine, etc.) contained in the halogenated copolymer rubber is 0.7 to 10%, more preferably 1 to 10%.
10%.

The halogenated copolymer rubber is prepared by using, for example, isobutylene and p-methylstyrene in an amount of 0.001 to 0.2% of Lewis acid catalyst such as ethylaluminum dichloride with respect to the total amount of monomers, and methyl chloride or the like. It is produced by copolymerizing in a solvent of the above and then radically halogenating.

Specific examples of the halogenated copolymer rubber include, for example, EXXPRO 90-10 manufactured by Exxon.
(Isobutylene-p-methylstyrene copolymer rubber having a bromine content of about 2%), EXXXPRO 93-4 (bromine content of about 2%), and EXXXPRO 93-5 (bromine content of about 0.1%).
8%).

The silica-treated carbon black used in the present invention can reduce the hysteresis loss when the carbon black used in the tread rubber composition is replaced with silica in order to reduce the rolling resistance of the tire. Although it is possible, on the other hand, the amount of carbon black decreases, the electric resistance of the tire increases, the problem caused by the accumulation of static electricity in the car is reduced, and the problem of static electricity in silica formulation is not caused. It is used in order to make it possible to achieve both the same rolling resistance and wet performance as in the case of silica compounding, and to suppress a decrease in the abrasion resistance seen when a halogenated copolymer rubber is used. That is, by using the silica-treated carbon black in combination with the halogenated copolymer rubber, the problems of electric resistance and the problems of wet performance, rolling resistance, and abrasion resistance can all be improved. Further, since the halogenated copolymer rubber having a small number of double bonds is used, the amount of the antioxidant which causes poor appearance due to brown discoloration can be reduced.

The above silica-treated carbon black (hereinafter referred to as “carbon black”)
Silica-treated CB) may be obtained by treating the surface of carbon black with silica. Carbon black and silica are mixed three-dimensionally in one particle. May also be exposed on the particle surface.

The carbon black obtained by treating the surface of silica with silica is preferably a nitrogen adsorption specific surface area (N ₂ S).
A) is from 90 to 250 m ² / g, more preferably from 90 to 250 m ² / g.
200 m ² / g, CDBP oil absorption / DBP oil absorption is preferably 0.5 to 1.0, and more preferably 0.6 to 0.
92. The DBP oil absorption is 90-180ml /
About 100g, CDBP oil absorption 80-180ml / 1
It is about 00 g. Nitrogen adsorption specific surface area is 90m ² / g
In the case of less than, insufficient reinforcing property to rubber, breaking strength and abrasion resistance may be degraded, 250 meters conversely ²
If it exceeds / g, kneading into rubber becomes difficult, and dispersion may be poor. If the CDBP oil absorption / DBP oil absorption is too small, the specific surface area tends to be large, and the workability tends to decrease. If the CDBP oil absorption / DBP oil absorption is too large, the necessary reinforcing property tends not to be obtained.

The ratio of silica to carbon black contained in the surface of the carbon black treated with silica is such that the ratio of silica to carbon black is 0.1 to 50.
%, More preferably 0.5 to 20%, particularly 2 to 10%, from the viewpoint that the characteristics of carbon black and silica are exhibited in a well-balanced manner.

The carbon black and the silica are three-dimensionally mixed in one particle, and the silica and the carbon black both exposed on the particle surface have the structure as described above. The number of functional groups present in the carbon black is low, and the number of functional groups present on the surface is low, and the number of functional groups present on the surface is large. And a portion of silica that can be contained in one particle. By treating carbon black, which has excellent wear resistance, with silica and using silica-treated CB with increased chemical bonding ability with the polymer, the tread of truck / bus tires often used under severe conditions is used. It is possible to achieve both a reduction in rolling resistance (lower fuel consumption) and abrasion performance under severe conditions.

In the case of the silica-treated CB in which carbon black and silica are mixed three-dimensionally in one particle, both the carbon portion and the silica portion have portions that are exposed on the surface of the particle, Most of the carbon black portion is not covered with silica unlike the surface-treated carbon black. Therefore, abrasion resistance under severe conditions, which is a feature of using carbon black, is sufficiently improved. In addition, since silica is contained, the surface active points of the silica-treated CB are larger than those of ordinary carbon black, the number of bound rubbers is also larger, and the rolling resistance can be reduced.

The ratio of carbon black and silica in the silica-treated CB in which carbon black and silica are three-dimensionally mixed in one particle is 0.1 to 25% of silica with respect to carbon black. Is 0.5 ~
It is preferably 10%, particularly preferably 2 to 6%, from the viewpoint that the characteristics of carbon black and silica are well-balanced.

The carbon black surface treated with silica is prepared, for example, by preparing a carbon black slurry, heating the slurry to a predetermined temperature, and adding diluted JIS No. 3 sodium silicate to maintain the pH at 5-10. It can be produced by depositing silica on the surface of carbon, then setting the pH at 6, leaving the mixture to stand, filtering, washing with water, and drying.

The silica content can be adjusted by adjusting the amount of sodium silicate added and the pH of the system.

The method of producing the silica-treated CB in which the carbon black and silica are mixed three-dimensionally in one particle is not particularly limited, but is produced in one step by reacting an organic siloxane at the same time as the raw material oil. The method is preferred. The preferred production method is described in, for example, International Publication No. 96/96.
/ 37547 pamphlet.

The silica content in the silica-treated CB can be determined by the following formula after incineration of the silica-treated CB at 600 ° C. in an electric furnace, followed by the following treatment with hydrogen fluoride.

Hydrogen fluoride treatment: About 200 mg of a sample is weighed and placed in a polyethylene beaker, moistened with distilled water, and then excess hydrogen fluoride is added. This is stirred, left for 5 minutes, filtered by suction, washed well with distilled water and dried. Silica content (%) = [(weight of silica-treated CB−weight after hydrogen fluoride treatment) / (weight of silica-treated CB)] ×
The characteristics of the prepared silica-treated CB can be measured by the following measurement methods. Nitrogen adsorption specific surface area: ASTM D3037 DBP oil absorption: ASTM D2414 CDBP oil absorption: ASTM D3493

The mixing ratio of the silica-treated CB is at least 10 parts, preferably at least 25 parts, more preferably at least 40 parts, per 100 parts of the rubber component. Silica treatment C
When the compounding ratio of B is less than 10 parts, it becomes difficult to obtain sufficient wet performance. Note that the upper limit of the mixing ratio of the silica-treated CB is preferably 100 parts, and more preferably 70 parts, from the viewpoint that processing is not difficult.

The silane coupling agent is a component used to combine with the silica-treated CB to increase the dispersibility of the silica-treated CB in the rubber component and to further reduce the rolling resistance.

As the silane coupling agent, any one which has been conventionally compounded with silica in a rubber composition can be used without particular limitation. Specific examples thereof include, for example, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, β- (3,
4 epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ
-Glycidoxypropylmethyldiethoxysilane, γ-
Glycidoxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, N-β (amino Ethyl) γ-aminopropylmethyldimethoxysilane, N-
β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ- Examples thereof include aminopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, and bis- (3- [triethoxysilyl] -propyl) -tetrasulfen. These may be used alone or in combination of two or more. Of these, bis- (3
-Triethoxysilylpropyl) -tetrasulfide and the like are preferred.

The amount of the silane coupling agent is 2 to 14%, preferably 2 to 6%, based on the silica-treated CB. If the amount of the silane coupling agent is less than 2%, the performance such as abrasion resistance and rolling resistance deteriorates, and
Even if it is used in an amount of more than 4%, it is difficult to obtain a performance-improving effect corresponding to the compounding amount.

The composition of the present invention may contain, in addition to the above-mentioned components, components and additives generally used in the production of rubber compositions for tire treads, if necessary, in the amounts and amounts usually used. Good. Specific examples of the components and additives include, for example, process oils (paraffin-based process oils,
Naphthenic process oils, aromatic process oils), vulcanizing agents (sulfur, sulfur chloride compounds, organic sulfur compounds, etc.), vulcanization accelerators (guadinine, aldehyde-amine, aldehyde-ammonia, thiazole, sulfol) Phenamide, thiourea, thiuram, dithiocarbamate, and zandate compounds), crosslinking agents (radical generators such as organic peroxide compounds and azo compounds, oxime compounds, nitroso compounds, polyamine compounds, etc.), Reinforcing agents (high styrene resin, phenol-formaldehyde resin, etc.), antioxidants or anti-aging agents (diphenylamine-based, p-phenylenediamine-based amine derivatives, quinoline derivatives, hydroquinone derivatives, monophenols, diphenols, thiols Bisphenols Hindered phenols,
Phosphites), wax, stearic acid,
Examples include zinc oxide, softeners, other fillers, and plasticizers.

When silica is used as the other filler, a silane coupling agent may be used to increase the dispersibility of the silica in the rubber component. The amount of the silane coupling agent used for silica is usually 6 to 10%. When silica and silica-treated CB are used in an equal amount, it is considered that 60 to 80% of the silane coupling agent used is for silica and 20 to 40% is for silica-treated CB. When it is desired to clarify the amount of the silane coupling agent to be bonded to the silica-treated CB and the amount of the silane coupling agent to be bonded to the silica, they may be used after being mixed and bonded in advance.

[0032]

EXAMPLES Next, the composition of the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

The raw materials used in the examples and comparative examples and the evaluation methods are summarized below. SBR1502: Styrene-butadiene rubber manufactured by Sumitomo Chemical Co., Ltd. Halogenated copolymer rubber: EXXPRO manufactured by Exxon
90-10, isobutylene-p-methylstyrene copolymer rubber having a bromine content of about 2% Silica treatment CB: CRX2000, N manufactured by Cabot Corporation
-234 containing 4.7% silica in carbon black, N ₂ SA: 154.3 m ² / g, DBP oil absorption: 11
3cc / 100g, CDBP oil absorption: 102cc / 10
0 g Silica: Degussa, Ultrasil VN3 Carbon black: Tokai Carbon Co., Ltd., N220 Silane coupling agent: Degussa, Si69, bis (3-triethoxysilylpropyl) tetrasulfide Process oil: Idemitsu Kosan Co., Ltd. ), Diana Process PS32 Anti-aging agent: Seiko Chemical Co., Ltd., Ozone 6C, (N-1,
3-dimethylbutyl) -N-phenyl-p-phenylenediamine Wax: manufactured by Ouchi Shinko Chemical Co., Ltd., Sannoc wax Stearic acid: manufactured by NOF CORPORATION, Zinc Hana: manufactured by Toho Zinc Co., Ltd. Ginrei R Sulfur: Tsurumi Chemical Co., Ltd., sulfur Vulcanization accelerator: Ouchi Shinko Chemical Co., Ltd., Noxeller N
S, N-tert-butyl-2-benzothiazolylsulfenamide

(Wet Performance) After spraying water on a test course on which low resistance (μ) tiles are spread, the maximum speed at which a 2000 cc class passenger car equipped with four test tires makes a circular turn and slips is determined. measure.
The evaluation was indicated by an index with Comparative Example 1 or 5 being 100. The larger the index, the better the wet performance.

(Rolling Resistance) Using a testing machine manufactured by Kobe Machinery Co., Ltd., load 345 kg, internal pressure 200 kPa, speed 80
After running at km / h, the rolling resistance is measured. The evaluation was indicated by an index with Comparative Example 1 or 5 being 100. The higher the index, the lower the rolling resistance and the better.

(Abrasion resistance) Using a Lambourn abrasion tester manufactured by Iwamoto Seisakusho Co., Ltd., the surface rotation speed was 50 m / min, the applied load was 2.5 kg, the amount of falling sand was 15 g / min, and the slip ratio was 40%.
The wear of the test piece is measured with. The evaluation was indicated by an index with Comparative Example 1 or 5 being 100. The larger the index, the better the wear resistance.

(Volume specific resistance value)
A rubber sheet obtained by vulcanizing at 70 ° C. for 20 minutes was cut in a direction parallel to the roll axis to prepare a rubber test piece provided with a predetermined electrode, and the test piece was held at 23 ± 2 ° C. for 48 hours. Thereafter, the resistance value R between the electrodes was measured at the same temperature, and the volume specific resistance value Rv (Rv = (a × b × R) / L) was calculated.
Here, a and b represent the thickness and width of the rubber test piece, respectively, and L represents the distance between the measurement electrodes.

(Appearance) The degree of brown discoloration after outdoor exposure (left for 6 months in an outdoor day) was visually observed, and the degree of brown discoloration was 1 (discolored entirely brown) to 5 (discoloration was not observed). The evaluation was made in five steps.

Examples 1 to 3 and Comparative Examples 1 to 4 Among the components shown in Table 1, components other than sulfur and the vulcanization accelerator were as described in Table 1 at a ratio shown in Table 1, and 1.7 L manufactured by Kobe Steel Ltd. was used.
After kneading in a Banbury at about 150 ° C. for 4 minutes, 1.5 parts of the remaining sulfur and 1.0 part of the vulcanization accelerator were added to the obtained kneaded material. Thereafter, the mixture kneaded at 80 ° C. for about 4 minutes using a twin-screw roller was heated at 170 ° C. for 12 minutes.
After vulcanization for a minute, a vulcanized product of the rubber composition for a tire tread or a tire using the rubber composition for a tire tread was manufactured and evaluated. Table 1 shows the results.

In addition, 2.4 parts of 3.4 parts of the silane coupling agent of Example 3 were used for silica, and 1 part was used for silica-treated CB.

[0041]

[Table 1]

From Table 1, it can be seen that the composition of the present invention has almost the same abrasion resistance as compared with Comparative Example 1, and has excellent wet performance and rolling resistance. In addition, it is understood that the volume resistivity is lower than Comparative Examples 3 and 4 using silica as a filler.

Examples 4-6 and Comparative Examples 5-8 Evaluations were made in the same manner as in Example 1 except that the components shown in Table 2 were used in the amounts shown in Table 2. Table 2 shows the results.

[0044]

[Table 2]

[0045]

When the rubber composition for a tire tread of the present invention is used, the electric resistance is low, the rolling resistance characteristics, the abrasion resistance,
A well-balanced tire having a high level of wet performance can be provided.

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Claims (2)

[Claims] 1. A rubber component comprising 70 to 95% by weight of a diene rubber and 5 to 30% by weight of a halogenated copolymer rubber obtained by halogenating an isobutylene-p-methylstyrene copolymer rubber is used in an amount of 100 parts by weight of silica. A rubber composition for a tire tread, comprising 10 to 10 parts by weight of treated carbon black and 2 to 14% by weight of a silane coupling agent based on silica-treated carbon black. 2. The rubber composition for a tire tread according to claim 1, wherein the silica-treated carbon black is obtained by treating a surface of carbon black with silica at a ratio of 0.1 to 50% by weight.