JP2002338750A - Tread rubber composition and pneumatic tire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition which maintains low heat build-up without lowering processability and abrasion resistance and has excellent wet grip performance. SOLUTION: The tire tread rubber composition can be obtained by simultaneously mixing 100 pts.wt. rubber component, 5-150 powder of an inorganic compound such as aluminum hydroxide and clay, 5-150 pts.wt. carbon black having a specific area by nitrogen absorption of 70-300 m<2> /g, and a specific silane coupling agent having an average value of the number of sulfur atoms in the sulfide moiety of 2.1-3.5 at 120-200 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rubber composition for a tire tread and a pneumatic tire using the same. More specifically, the present invention relates to a rubber composition for a tire tread, which maintains fuel economy and significantly improves grip performance particularly on a wet road surface, and a pneumatic tire using the rubber composition for a tread rubber.

[0002]

2. Description of the Related Art In recent years, the characteristics required for automobile tires are various, such as driving stability, abrasion resistance, and riding comfort, in addition to low fuel consumption. Various improvements have been made to improve these performances. .

For example, in order to improve various performances such as braking performance and steering stability on a wet road surface at the time of high-speed running, a method of increasing a grip force with a road surface, a method of increasing a block rigidity of a tire tread pattern, and a method of cornering. A method of preventing block deformation at the time and improving cornering characteristics, and a method of preventing deformation of a groove formed in a tire tread so as to smoothly drain water and prevent hydroplaning are performed.

[0004] Recently, in response to such required characteristics, grip performance on wet road surfaces has been improved by blending silica with high styrene SBR (styrene-butadiene rubber).

[0005] However, the rubber composition for a tire tread as described above can enhance the grip force in a low temperature region where the road surface temperature is 15 ° C or less, but can be used on a wet road surface or a semi-wet surface in a high temperature region exceeding 15 ° C. It is said that a (semi-dry) road surface cannot exhibit sufficient grip.
Further, it has been found that the rubber composition containing silica decreases the rigidity of the rubber when the vehicle is repeatedly run, and the grip force is greatly reduced. In addition, in the rubber composition containing silica, if the dispersion of the silica particles in the rubber is insufficient, the Mooney viscosity of the rubber composition becomes high, and problems such as poor processability such as extrusion occur.

Various proposals have conventionally been made to solve these problems. For example, a method for improving grip performance and the like has been proposed by blending calcined clay with diene rubber and blending a vulcanized rubber powder composed of diene rubber and kaolinite with a specific diene rubber. I have.

Further, SB having a specific amount of styrene unit
By mixing an inorganic compound powder having a specific composition and carbon black into R, kaolinite is mainly added to a diene rubber having a 1,2-bond content in a butadiene portion within a specific range. A method of improving grip performance and the like by blending clay as a component has been proposed.

However, at present, there is no rubber composition which maintains low heat build-up without deteriorating workability and wear resistance and has excellent wet grip performance.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber composition which maintains low heat build-up without deteriorating workability and abrasion resistance and is excellent in wet grip performance.

[0010]

According to the present invention, there is provided a rubber component comprising:
0 parts by weight, 5 to 150 parts by weight of an inorganic compound powder represented by the following general formula (1), and a nitrogen adsorption specific surface area of 70 to 300 m
5 to 150 parts by weight of ² / g carbon black, and
A silane coupling agent represented by the following general formula (2)
The present invention relates to a rubber composition for a tire tread obtained by simultaneously mixing at 120 to 200 ° C. kM ¹ .xSiO _y .zH ₂ O (1) (In the formula (1), M ¹ is at least one metal selected from the group consisting of Al, Mg, Ti and Ca, or an oxide or water of the metal. K is an integer of 1 to 5, x is an integer of 0 to 10, y is an integer of 2 to 5, and z is an oxide.
Is an integer of 0 to 10. _{) (C n H 2n + 1} O) 3 -Si- (CH 2) m -S 1 - (CH 2) m -Si- (C n H 2n + 1 O) 3 (2) ( Equation (2) , N is an integer of 1 to 3, m is an integer of 1 to 4,
l is the number of sulfur atoms in the polysulfide portion, and the average value of 1 is a positive number of 2.1 to 3.5. )

Further, the present invention relates to a pneumatic tire using the above rubber composition for a tread rubber.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The rubber composition of the present invention contains a rubber component, an inorganic compound powder, carbon black and a silane coupling agent.

As the rubber component, a diene-based synthetic rubber or a mixture of a diene-based rubber component and a natural rubber can be used. As the diene-based synthetic rubber used in the present invention, styrene-butadiene rubber (SBR),
Butadiene rubber (BR), isoprene rubber (IR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), butyl rubber (IIR) and the like. These rubbers may be used alone or in combination of two or more.

The rubber component desirably contains SBR from the viewpoint of workability. The SBR content in the rubber component is preferably at least 20% by weight, more preferably 30% by weight.
% By weight or more. In addition, styrene butadiene rubber is
It may be produced by any polymerization method such as an emulsion polymerization method and a solution polymerization method.

The amount of styrene unit contained in the SBR is
It is preferably 20 to 50% by weight. If the styrene unit amount is less than 20% by weight, sufficient grip performance tends not to be obtained, and if it exceeds 50% by weight, abrasion resistance tends to decrease. More preferably, the styrene unit amount is 40% by weight at the upper limit and 25% by weight at the lower limit.

As the inorganic compound powder, an inorganic compound powder represented by the following general formula (1) is used. kM ¹ .xSiO _y .zH ₂ O (1) In the formula (1), M ¹ is at least one metal selected from the group consisting of Al, Mg, Ti and Ca, or an oxide or hydroxide of the metal. K is an integer of 1 to 5, x is an integer of 0 to 10, y is an integer of 2 to 5, and z
Is an integer of 0 to 10.

Examples of the inorganic compound represented by the general formula (1) include alumina, alumina hydrate, aluminum hydroxide, magnesium hydroxide, magnesium oxide, talc, titanium white, titanium black, calcium oxide, water Examples include calcium oxide, magnesium aluminum oxide, clay, kaolin, pyrophyllite, bentonite, aluminum silicate, magnesium silicate, calcium silicate, aluminum calcium silicate, calcium magnesium silicate, and the like. These inorganic compounds may be used alone or in combination of two or more. Among these inorganic compounds, aluminum hydroxide, alumina, clay and the like are preferable from the viewpoint of improving gripping power.

The average particle size of the inorganic compound powder is 0.01
It is preferably from 10 to 10 μm. If the average particle size of the inorganic compound powder is less than 0.01 μm, the workability tends to decrease, and if it exceeds 10 μm, the wear resistance tends to decrease. More preferably, the average particle diameter of the inorganic compound powder is 8 μm at the upper limit and 0.02 μm at the lower limit.

The compounding amount of the inorganic compound powder is 5 to 150 parts by weight based on 100 parts by weight of the rubber component. If the amount is less than 5 parts by weight, the effect of improving wet grip performance is small. If the amount is more than 150 parts by weight, sufficient wet grip performance cannot be obtained despite a decrease in wear resistance. Preferably, the compounding amount of the inorganic compound powder is 120 parts by weight at the upper limit and 10 parts by weight at the lower limit.

As the carbon black, those having a nitrogen adsorption specific surface area (N ₂ SA) of 70 to 300 m ² / g are used. If the N ₂ SA of the carbon black is less than 70 m ² / g, it is difficult to obtain sufficient reinforcement and abrasion resistance.
If it exceeds 00 m ² / g, dispersibility becomes poor and heat generation increases. Preferably, carbon black N ₂ SA
Is ^{90m 2 / g 250m 2 / g} , with the lower limit at the upper limit.
Examples of such carbon black include HAF, I
Examples include SAF and SAF, but are not particularly limited.

The compounding amount of carbon black is 5 to 150 parts by weight based on 100 parts by weight of the rubber component. If the compounding amount of carbon black is less than 5 parts by weight, the reinforcing property and abrasion resistance decrease, and if it exceeds 150 parts by weight, dispersibility decreases and there is no desired property. Preferably, the compounding amount of carbon black is 120 parts by weight at the upper limit, more preferably 10 parts by weight.
0 parts by weight, 10 parts by weight at the lower limit, and further 15 parts by weight.

As the silane coupling agent, those represented by the following general formula (2) are used. _{(C n H 2n + 1 O} ) 3 -Si- (CH 2) m -S 1 - (CH 2) m -Si- (C n H 2n + 1 O) ₃ (2) (2), n Is an integer of 1-3, m is an integer of 1-4, l
Is the number of sulfur atoms in the polysulfide moiety, and the average value of 1 is a positive number of 2.1 to 3.5, preferably 2.1 to 3. With a silane coupling agent having an average value of l larger than 3.5, the processability decreases as the kneading temperature increases.

Examples of such a silane coupling agent include bis (3-triethoxysilylpropyl) polysulfide, bis (2-triethoxysilylethyl) polysulfide, bis (3-trimethoxysilylpropyl) polysulfide, and bis (3-trimethoxysilylpropyl) polysulfide. Examples thereof include 2-trimethoxysilylethyl) polysulfide, bis (4-triethoxysilylbutyl) polysulfide, and bis (4-trimethoxysilylbutyl) polysulfide. These silane coupling agents can be used singly or in combination of two or more. Among these silane coupling agents, bis (3-tri) is selected from the viewpoint of the effect of adding the coupling agent and the cost. Ethoxysilylpropyl) polysulfide is preferably used.

The amount of the silane coupling agent is as follows:
The amount is preferably 1 to 20% by weight based on the total weight of the inorganic compound powder and silica described below. If the amount of the silane coupling agent is less than 1% by weight, the effect of adding the silane coupling agent tends not to be sufficiently obtained.
If the content is more than the weight%, the coupling effect cannot be obtained for the increased cost, and the reinforcing property and the wear resistance tend to be reduced. From the viewpoint of the dispersing effect and the coupling effect, the amount of the silane coupling agent is preferably 2 to 15% by weight.

[0026] The rubber composition of the present invention may further contain silica. Examples of the silica are not particularly limited, and may be appropriately selected from those conventionally used for reinforcing rubber, for example, dry silica and wet silica.

Nitrogen adsorption specific surface area of silica (N ₂ SA)
Is preferably 100 to 300 m ² / g. If the N ₂ SA of the silica is less than 100 m ² / g, the reinforcing effect tends to be small, and if it exceeds 300 m ² / g, the dispersibility tends to decrease, and the heat build-up of the rubber composition tends to increase. More preferably, the N ₂ SA of the silica is at most 280 m ² /
g, and the lower limit is 130 m ² / g.

The amount of the silica is preferably 5 to 100 parts by weight based on 100 parts by weight of the rubber component.
If the amount of silica is less than 5 parts by weight, sufficient wet grip performance tends not to be obtained, and if it exceeds 100 parts by weight, workability tends to decrease. More preferably, the amount of silica is 80 parts by weight at the upper limit and 10 parts by weight at the lower limit.

The rubber composition of the present invention contains, in addition to the rubber component, inorganic compound powder, carbon black, silane coupling agent, and silica, if necessary,
Compounding agents used in the ordinary rubber industry, such as an antioxidant, a vulcanizing agent, a vulcanization accelerator, and a vulcanization accelerator may be appropriately compounded.

The rubber composition of the present invention comprises a rubber component, an inorganic compound powder, carbon black, a silane coupling agent and, if necessary, a vulcanizing agent such as silica (vulcanizing agent and vulcanization accelerator). ) Excluding rubber kneading additives
In the mixing step, it is obtained by simultaneously kneading at a kneading temperature of 120 to 200 ° C. Kneading temperature is 1
If the temperature is lower than 20 ° C., the reactivity of the silane coupling agent is low, and sufficient performance cannot be obtained. More preferably, the kneading temperature is 180 ° C. at the upper limit and 140 ° C. at the lower limit.

In the mixing step, the kneading time is 4
~ 15 minutes is preferred. If the kneading time is less than 4 minutes, the dispersion of chemicals such as carbon black tends to be insufficient, and if the kneading time exceeds 15 minutes, the rubber component tends to have a low molecular weight and sufficient performance tends not to be obtained.

The tire of the present invention is produced by a usual method using the rubber composition of the present invention. That is, if necessary, the rubber composition of the present invention containing the above-mentioned various chemicals is extruded into a tread member in an unvulcanized stage, and is formed by sticking on a tire molding machine by a usual method. Form sulfur tires. The unvulcanized tire is heated and pressed in a vulcanizer to obtain a tire. The tire of the present invention thus obtained is excellent in wear resistance, low heat generation, wet grip performance, and the like.

[0033]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but this does not limit the purpose of the present invention.

Examples 1-4 and Comparative Examples 1-3 (1) Description of Various Chemicals SBR: SBR1502 manufactured by JSR Corporation
(Styrene unit content: 23.5 wt%) Carbon black; Showa Cabot Co. Ltd. SHOWBLACK ^{_{N220 (N 2 SA: 125m 2}} / g) of aluminum hydroxide: manufactured by Showa Denko Co., Ltd. Higilite H-43 (Average particle diameter: 0.5 to 2 μm) Clay: Crown clay manufactured by South Eastern (particle diameter: 2 μm or less) Silica: Ultrasil VN3 (N ₂ S manufactured by Degussa)
A: 210 m ² / g) Silane coupling agent A: Si69 (l, manufactured by Degussa)
Average value of about 3.8) (bis (3-triethoxysilylpropyl) tetrasulfide) Silane coupling agent B: Si266 manufactured by Degussa
(Average value of l: about 2.2) (bis (3-triethoxysilylpropyl) disulfide) Aroma oil: JOMO process X140 manufactured by Japan Energy Co., Ltd. Antioxidant; manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Nocrack 6
C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) Stearic acid: Stearic acid manufactured by NOF Corporation Zinc oxide: Zinc flower No. 1 manufactured by Mitsui Kinzoku Mining Co., Ltd. Sulfur: powder sulfur manufactured by Tsurumi Chemical Co., Ltd. Vulcanization accelerator TBBS: Noxeller NS (N-tert-butyl-2-benzothiazylsulfenamide) manufactured by Ouchi Shinko Chemical Co., Ltd. Vulcanization accelerator DPG A Noxeller D (N, N'-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

(2) Production method According to the composition shown in the following composition table 1, first, chemicals other than sulfur and the vulcanization accelerator are kneaded and mixed at 150 ° C. for 4 minutes. In addition, they were kneaded and compounded to obtain various test rubber compositions.

Each of these test rubber compositions was press-vulcanized at 170 ° C. for 20 minutes to obtain a vulcanized product, which was tested for the following properties.

(3) Test Method (Workability) Measured at 130 ° C. in accordance with the Mooney viscosity measurement method specified in JIS K6300. The Mooney viscosity (ML _{1 + 4} ) of Comparative Example 1 was set to 100 and expressed as an index by the following formula (Mooney viscosity index). The larger the index, the lower the Mooney viscosity and the better the workability. (Mooney viscosity index) = (ML _{1 + 4} of Comparative Example 1) ÷ (ML _{1 + 4 of} each formulation) × 100

(Abrasion test) Using a Lambourn abrasion tester,
The Lambourn abrasion amount was measured under the conditions of a temperature of 20 ° C., a slip ratio of 20%, and a test time of 5 minutes, and the volume loss of each composition was calculated. index). The larger the index, the better the wear resistance. (Abrasion index) = (Loss of Comparative Example 1) / (Loss of each compound) × 100

(Rolling resistance index) Using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho), a temperature of 70
T, initial strain 10%, dynamic strain 2%
an δ was measured, and tan δ of Comparative Example 1 was taken as 100.
An index was expressed by the following formula (rolling resistance index). The larger the index, the better the rolling resistance characteristics (low heat generation). (Rolling resistance index) = (tan δ of Comparative Example 1) ÷ (tan δ of each formulation) × 100

(Wet skid test) Using a portable skid tester manufactured by Stanley, ASTM E
It measured according to the method of 330-83, and set the measured value of the comparative example 1 to 100, and indicated it as an index by the following formula (wet skid index). The higher the index, the better the wet skid performance. (Wet skid index) = (numerical value of each formulation) / (numerical value of comparative example 1) × 100

The results are shown in Table 1.

[0042]

[Table 1]

[0043]

According to the present invention, it is possible to provide a rubber composition excellent in processability, abrasion resistance, rolling resistance and wet skid performance, and a pneumatic tire using the same. In the present invention, since the silane coupling agent having a small number of sulfur atoms in the sulfide portion is blended, there is no problem that the Mooney viscosity increases and the processability decreases even when kneading at a high temperature.

Continued on front page F-term (reference) 4J002 AC031 AC061 AC071 AC081 AC091 BB151 BB181 DA037 DE076 DE086 DE136 DE146 DJ006 DJ036 DJ046 EX038 FD016 FD017 FD208 GN01

Claims (2)

[Claims] 1. 100 parts by weight of a rubber component, 5 to 150 parts by weight of an inorganic compound powder represented by the following general formula (1), and 5 to 150 parts by weight of carbon black having a nitrogen adsorption specific surface area of 70 to 300 m ² / g. And a silane coupling agent represented by the following general formula (2) at a temperature of 120 to 200 ° C .: kM ¹ .xSiO _y .zH ₂ O (1) (In the formula (1), M ¹ is at least one metal selected from the group consisting of Al, Mg, Ti and Ca, or an oxide or water of the metal. K is an integer of 1 to 5, x is an integer of 0 to 10, y is an integer of 2 to 5, and z is an oxide.
Is an integer of 0 to 10. _{) (C n H 2n + 1} O) 3 -Si- (CH 2) m -S 1 - (CH 2) m -Si- (C n H 2n + 1 O) 3 (2) ( Equation (2) , N is an integer of 1 to 3, m is an integer of 1 to 4,
l is the number of sulfur atoms in the polysulfide portion, and the average value of 1 is a positive number of 2.1 to 3.5. ) 2. A pneumatic tire using the rubber composition according to claim 1 for a tread rubber.