JP2002003652A - Rubber composition and pneumatic tire using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition which includes silica and maintains a low Mooney viscosity and is excellent in rubber reinforcing property, dimensional stability, productivity, wear resistance and the like. SOLUTION: This rubber composition comprises a rubber component of 100 pts.wt. including at least one diene rubber, silica of 20-120 pts.wt. pretreated with a silane coupling agent of 2-15 wt.%, and alkoxysilane having 2-10 wt.% of the amount of silica before pretreatment with the silane coupling agent. It is preferable that the silane coupling agent includes a sulfur atom in the molecule and that the alkoxsilane includes a sulfur atom in the molecule and that the silica before pretreatment is a wet silica having a nitrogen adsorbing specific surface area of 70-300 m2/g measured by BET method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a composition containing silica,
The present invention relates to a rubber composition suitable for a pneumatic tire and the like, and a pneumatic tire using the rubber composition.

[0002]

2. Description of the Related Art In recent years, a full-scale response to a global warming problem, a problem of energy depletion in the future, and the like has been required, and it is particularly necessary in the automobile industry to realize low fuel consumption. Is coming. With respect to automobile tires, there are increasing examples in which a high proportion of silica is blended as a rubber reinforcing material in place of carbon black, which has been widely used in the past, to reduce rolling resistance and achieve the above-described fuel efficiency. However, when silica is added to the rubber composition at a high ratio in place of carbon black, there are the following problems. That is, since the rubber composition has a large shrinkage in the extrusion direction, if the rubber composition is allowed to stand after extrusion, the width difference and the gauge difference in the rubber composition become large.
For this reason, when a tire is molded using the rubber composition, there is a problem that the weight balance on the circumference of the tire is deteriorated and the uniformity of the tire during rotation is deteriorated.

In order to solve this problem and improve the reinforcing property and processability of the rubber composition, a silane coupling agent having an alkoxysilyl group chemically bondable to silica in the molecule has been conventionally used. Has been used. However, in this case, the silane coupling agent generates an alcohol upon reaction with silica, and the alcohol volatilizes and foams in the rubber composition to increase porosity. There is a problem that dimensional stability and productivity are reduced.

[0004] For this reason, it is difficult to pre-treat silica using the silane coupling agent instead of adding the silane coupling agent to the rubber composition.
Nos. 1751, EP0177674, JP-A-59-206469, JP-A-5-17705, JP-A-9-328631, and JP-A-9-12.
No. 922, for example. However, in this case, when the treatment amount of the silane coupling agent is increased, the silanol group on the silica surface reacts with the silane coupling agent, so that the water adsorbed on the silanol group decreases, and the dispersion of the silica decreases. There is a problem that the viscosity is hindered and the viscosity of the rubber composition increases.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, the present invention contains silica, maintains a low Mooney viscosity, rubber reinforcement, dimensional stability, productivity,
An object of the present invention is to provide a rubber composition having excellent wear resistance and the like, and a high-quality pneumatic tire having excellent wear resistance using the rubber composition.

[0006]

Means for solving the above problems are as follows. <1> 100 parts by weight of a rubber component containing at least one diene rubber, 20 to 120 parts by weight of silica pretreated with 2 to 15% by weight of a silane coupling agent, and And 2 to 10% by weight of the silica of the silica. <2> The rubber composition according to <1>, wherein the silane coupling agent has a sulfur atom in the molecule. <3> The rubber composition according to <1> or <2>, wherein the silane coupling agent is at least one kind represented by the following formula. In _{X m Y 3-m Si-} Z-S n -Z-SiX m Y 3-m Formula, X is an alkoxy group or a chlorine atom having 1 to 3 carbon atoms. Y represents an alkyl group having 1 to 3 carbon atoms. Z represents a saturated or unsaturated alkylene group having 1 to 12 carbon atoms, or an arylene group having 6 to 12 carbon atoms. m represents an integer of 1 to 3. n represents an integer of 1 or more and may have a distribution. <4> The rubber composition according to any one of <1> to <3>, wherein the alkoxysilane has a sulfur atom in the molecule. <5> The rubber composition according to any one of <1> to <4>, wherein the silica before the pretreatment is a wet silica having a nitrogen adsorption specific surface area measured by a BET method of 70 to 300 m ² / g. Things. <6> A pneumatic tire using the rubber composition according to any one of <1> to <5>.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION (Rubber Composition) The rubber composition of the present invention contains a rubber component, silica, and alkoxysilane, and further contains other components appropriately selected as necessary.

-Rubber component- The rubber component contains at least one type of diene rubber. Examples of the diene rubber include natural rubber, polyisoprene rubber, polybutadiene rubber, styrene / butadiene rubber, acrylonitrile / butadiene rubber, chloroprene rubber, and ethylene / propylene / diene copolymer rubber. These may be used alone or in combination of two or more.

-Silica- As the silica, those pretreated with a silane coupling agent are used. The treatment amount of the silane coupling agent needs to be 2 to 15% by weight, preferably 5 to 13% by weight, based on the silica. When the treatment amount of the silane coupling agent is less than 2% by weight, the reinforcing property may be poor.
This can lead to worse scoring. In the present invention, as the processing amount, a lower limit or an upper limit of any one of the numerical ranges or any one of the contents used in Examples described later is a lower limit, and any one of the numerical ranges is used. The range in which the upper limit is either the lower limit or upper limit of the above or any of the contents employed in Examples described later is also preferable.

The silane coupling agent is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include vinyl silane, acrylic silane, epoxy silane, amino silane and the like. Examples of the vinyl silane include vinyl triethoxy silane and vinyl trimethoxy silane. Examples of the acrylic silane include γ-methacryloxypropyltrimethoxysilane. Examples of the epoxy silane include β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and the like. Examples of the aminosilane include N-β (aminoethyl) γ-aminopropyltrimethoxysilane,
-Phenyl-γ-aminopropyltrimethoxysilane,
And the like.

In the present invention, among the silane coupling agents, those having a sulfur atom in the molecule are preferable, and those represented by any of the following formulas (I) to (III) are more preferable.

[0012] Formula _{(I) X m Y 3-} m Si-Z-S n -Z-SiX m Y 3-m In Formula (I), X is an alkoxy group or a chlorine atom number of 1 to 3 carbon atoms And an alkoxy group having 1 to 3 carbon atoms is preferable, and a methoxy group and an ethoxy group are more preferable.
Y represents an alkyl group having 1 to 3 carbon atoms. Z represents a saturated or unsaturated alkylene group having 1 to 12 carbon atoms, or an arylene group having 6 to 12 carbon atoms. m represents an integer of 1 to 3, and 3 is preferable. n represents an integer of 1 or more;
2-8 are preferable, and may have distribution.

Specific examples of the silane coupling agent represented by the above formula (I) include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (3- Methyldimethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylethyl) tetrasulfide,
Bis (3-triethoxysilylpropyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (3-triethoxysilylpropyl) trisulfide, and the like are preferred.

[0014] Formula _{(II) X m Y 3-} m Si-Z-SH wherein formula (II), X represents an alkyl group or a chlorine atom having 1 to 3 carbon atoms. Y represents a mercapto group. Z
Represents a saturated or unsaturated alkylene group having 1 to 12 carbon atoms, or an arylene group having 6 to 12 carbon atoms. m is
Represents an integer of 1 to 3, and 3 is preferred.

Preferred examples of the silane coupling agent represented by the formula (II) include 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane.

[0016] Formula _{(III) X m Y 3-} m Si-Z-S n -A wherein formula (III), X is an alkyl group or a chlorine atom having 1 to 3 carbon atoms. Y represents a mercapto group.
A represents a benzothiazyl group, an N, N-dimethylthiocarbamoyl group, or a methacryloyl group. Z represents a saturated or unsaturated alkylene group having 1 to 12 carbon atoms, or an arylene group having 6 to 12 carbon atoms. m represents an integer of 1 to 3, and 3 is preferable. n represents an integer of 1 or more;
2-8 are preferable, and may have distribution.

Specific examples of the silane coupling agent represented by the formula (III) include 3-trimethoxysilylpropyl-N, N-dimethylcarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazolyltetrasulfide. And 3-trimethoxysilylpropyl methacryloyl monosulfide.

The silane coupling agent may be appropriately prepared or may be a commercially available product. The silane coupling agent may be used alone or in combination of two or more.

The pretreatment method is not particularly limited and may be appropriately selected depending on the intended purpose. For example, the predetermined amount of the silane coupling agent may be adjusted with respect to the silica before the pretreatment. And heat-treating the mixture after vigorous stirring.

The silica before the pretreatment may be a dry silica or a wet silica. In the present invention, the wet silica is preferred.

The silica has a nitrogen adsorption specific surface area (N ₂ SA) before the pretreatment of 70 to 300 m ² /
g is preferable, and 100-280 m < ² > / g is more preferable. The nitrogen adsorption specific surface area (N ₂ SA) is 70 m ² / g
If less than 300 m ² , the abrasion resistance may be poor.
If it exceeds / g, workability may be poor.

The amount of the silica is preferably 20 to 120 parts by weight, more preferably 30 to 100 parts by weight, based on 100 parts by weight of the rubber component. If the content of the silica is less than 20 parts by weight, the fuel economy may be poor, and if it exceeds 120 parts by weight, the processability may be poor. In the present invention, the lower limit or upper limit of any of the numerical ranges or any of the contents employed in the examples described below as the lower limit of the amount of the silica, A range in which any of the lower limit or upper limit or any of the contents used in Examples described later is the upper limit is also preferable.

-Alkoxysilane- Examples of the alkoxysilane include the same as those described as the silane coupling agent.
Further, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, isopropyltrimethoxysilane, n-butyltrimethoxysilane, n-octyltrisilane Ethoxysilane, n-dodecyltrimethoxysilane, n
-Dodecyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, and the like. These may be used alone,
Two or more kinds may be used in combination. Among these, those having a sulfur atom in the molecule are preferable.

The compounding amount of the alkoxysilane is as follows:
It is necessary that the content is 2 to 10% by weight of the silica before the pretreatment, and 2 to 8% by weight is preferable. If the amount is less than 2% by weight, processability may be poor, and if it exceeds 10% by weight, porosity may be deteriorated. In the present invention, the lower limit or upper limit of any of the above numerical ranges or any of the contents employed in the examples described below is used as the lower limit of the above-mentioned numerical range. It is also preferable that the lower limit or the upper limit of any one of the above or the range in which the value of any one of the contents employed in Examples described later is the upper limit.

-Total Amount of Silane Coupling Agent and Alkoxysilane- In the rubber composition of the present invention, the total amount of the amount of the silane coupling agent used in the pretreatment and the blending amount of the alkoxysilane is 6 to the weight of silica
It is preferably 20% by weight, more preferably 8 to 16% by weight. If the total amount is less than 6% by weight, the improving effect may not be sufficient, and if it exceeds 20% by weight, porosity may be deteriorated.

-Other Components- The other components can be appropriately selected according to the purpose within a range that does not impair the effects of the present invention, and commercially available products can be suitably used. Examples of the other components include, for example, a reinforcing filler, a vulcanizing agent such as sulfur, a vulcanization accelerator, a vulcanization aid, an antioxidant, zinc oxide, stearic acid, a coloring agent, an antistatic agent, and a dispersant. In addition to additives such as lubricants, softeners, inorganic fillers, and the like, various compounding agents usually used in the rubber industry are exemplified.

The reinforcing filler is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include carbon black and short fibers.

There is no particular limitation on the carbon black, and commercial products can be suitably used. The content of the carbon black in the rubber composition is preferably 60 parts by weight or less based on 100 parts by weight of the rubber component.

The short fibers are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include organic fibers such as polyamide fibers, polyolefin fibers, polyester fibers, and polyaramid fibers, and inorganic fibers such as glass fibers. Is mentioned.

-Production of Rubber Composition- The rubber composition of the present invention is produced according to a known method, for example, as follows. That is, the rubber composition of the present invention is obtained by appropriately kneading the rubber component, the silica, the alkoxysilane, and the other components selected as necessary, heating, extruding, and extruding. It is manufactured by sulfur molding. The kneading device includes, for example, a Banbury mixer, an intermix, a kneader, and the like which are usually used for kneading a rubber composition.

-Applications- The rubber composition of the present invention can be suitably used in various fields, and can be particularly preferably used for the following pneumatic tires of the present invention.

(Pneumatic Tire) The pneumatic tire of the present invention comprises at least the rubber composition of the present invention, preferably at least a tread. The pneumatic tire of the present invention is not particularly limited except that the rubber composition of the present invention is used, and the configuration of a known pneumatic tire can be employed as it is.

An example of the pneumatic tire is a pneumatic tire having a pair of bead portions, a carcass connected to the bead portions in a toroidal shape, a belt for tightening a crown portion of the carcass, and a tread. Preferable examples include tires. The pneumatic tire of the present invention may have a radial structure or may have a bias structure. The pneumatic tire of the present invention can be manufactured according to a known manufacturing method.

The pneumatic tire of the present invention can be suitably applied not only to so-called passenger cars but also to various vehicles such as trucks and buses.

[0035]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

Examples 1 to 4 and Comparative Examples 1 to 8 Each rubber composition having the composition shown in Table 1 was produced. The test sample for abrasion resistance was obtained by vulcanizing at 150 ° C. for 30 minutes. The following evaluation was performed about each rubber composition. The results are shown in Table 1.

<Mooney viscosity> JIS K6300-1
The Mooney viscosity at 125 ° C. of each rubber composition was measured according to 994. 100 parts of the rubber composition of Comparative Example 1
Exponential notation.

<Wear Resistance> The wear loss was measured using a Lambourn abrasion tester under the conditions of a load of 4 kg and a slip ratio of 50%, and was calculated by the following equation. Abrasion resistance index = ｛(weight of the rubber composition of Comparative Example 1 after test)
/ (Weight before the test of the rubber composition of Comparative Example 1) １００ × 100 The rubber composition of Comparative Example 1 was expressed as an index with 100 as the index. That is, the larger the value, the better the wear resistance.

<Porosity (%)> The specific gravity of the unvulcanized rubber composition is measured using a hydrometer (FAD type, manufactured by Toyo Seiki Seisaku-sho, Ltd.), and the ratio to the true specific gravity is expressed as a percentage. did. As this value is smaller, the porosity is smaller, which means that the rubber has excellent reinforcing properties, dimensional stability, and productivity.

<Bound rubber (%)> About 0.5 g of the unvulcanized rubber composition was added to a tetrahydrofuran solution at room temperature.
After immersion for 8 hours, after filtration and drying, the weight was measured,
The ratio of the rubber component remaining without being dissolved in tetrahydrofuran was defined as the amount of bound rubber. The larger this value is, the larger the amount of the bound rubber is, which means that the reinforcing property is excellent.

[0041]

[Table 1]

In Table 1, numerical values (quantities) represent "parts by weight". “SBR1712” is an emulsion-polymerized styrene-butadiene rubber (manufactured by JSR Corporation, SBR171)
2 (TM), 37.5 parts by weight of aroma oil oil). "BR01" means polybutadiene rubber (manufactured by JSR Corporation). "ULTRASILV
N3 (A) "is silica (manufactured by Degussa AG, ULTRAS
IL VN3 ™, fumed silica).
“COUPSIL8108 (B)” is silica (COUPSIL8108 ™ manufactured by Degussa AG, silica pretreated with 8% by weight of Si69 (ULTRASIL V).
N3)). "COUPSIL 8113
(C) "is silica (COUPSIL8 manufactured by Degussa AG)
113 ™, meaning silica (ULTRASIL VN3) pretreated with 13% by weight of Si69.
“Si75 pre-treated silica (D)” is obtained by adding 8% by weight of bis-3-triethoxysilylpropyl disulfide (manufactured by Degussa AG, Si75 ™) to wet silica (manufactured by Degussa AG, ULTRASIL VN3 ™). After vigorous stirring, heat treatment was performed at 100 ° C. for 1 hour, and then cooled. "Si69" is a silane coupling agent, and is formed of bis-3-triethoxysilylpropyl-tetrasulfide (manufactured by Degussa AG, Si6
9 (trademark)). "Si75" is a silane coupling agent, and bis-3-triethoxysilylpropyl disulfide (manufactured by Degussa AG, Si75 (trademark))
Means “N-dodecyltriethoxysilane” is
It is manufactured by Tokyo Chemical Industry Co., Ltd. In addition, "COUPSIL
8108 (B) ”,“ COUPSIL8113 (C) ”
And the numerical values in the column of “Si75 pre-treated silica (D)” mean parts by weight of the silica after the treatment, and the parts by weight before these treatments are all “60 parts by weight”.

From the results in Table 1, the following is clear. That is, in comparison with Comparative Examples 1 to 3 and 6 to 7 which are conventional rubber compositions containing silica, Examples 1 to 4 which are rubber compositions of the present invention containing silica pretreated with a silane coupling agent. , The Mooney viscosity decreased, the abrasion resistance improved, the porosity (%) was low, the bound rubber (%) was high, and good properties were exhibited. On the other hand, in Comparative Examples 4 to 5 and 8 in which pretreated silica was used but no alkoxysilane was blended, although the porosity (%) was improved to some extent, the Mooney viscosity was high, and the abrasion resistance was high.
Bound rubber (%) was not enough.

[0044]

According to the present invention, the above-mentioned conventional problems can be solved, silica is contained, Mooney viscosity is kept low, and rubber reinforcement, dimensional stability, productivity, abrasion resistance and the like are improved. An excellent rubber composition, and a high-quality pneumatic tire having excellent wear resistance using the rubber composition can be provided.

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Claims (6)

[Claims] 1. 100 parts by weight of a rubber component containing at least one diene rubber, 20 to 120 parts by weight of silica pretreated with 2 to 15% by weight of a silane coupling agent,
And 2 to 10% by weight of silica before the pretreatment. 2. The rubber composition according to claim 1, wherein the silane coupling agent has a sulfur atom in the molecule. 3. The rubber composition according to claim 1, wherein the silane coupling agent is at least one kind represented by the following formula. In _{X m Y 3-m Si-} Z-S n -Z-SiX m Y 3-m Formula, X is an alkoxy group or a chlorine atom having 1 to 3 carbon atoms. Y represents an alkyl group having 1 to 3 carbon atoms. Z represents a saturated or unsaturated alkylene group having 1 to 12 carbon atoms, or an arylene group having 6 to 12 carbon atoms. m represents an integer of 1 to 3. n represents an integer of 1 or more and may have a distribution. 4. The rubber composition according to claim 1, wherein the alkoxysilane has a sulfur atom in the molecule. 5. The silica before the pretreatment is BE
The nitrogen adsorption specific surface area measured by the T method is 70 to 300 m ² /
The rubber composition according to any one of claims 1 to 4, which is a wet silica as g. 6. A pneumatic tire using the rubber composition according to any one of claims 1 to 5.