JP2000038477A - Tire tread rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition of white color with high abrasion resistance, exhibiting moderate Mooney viscosity by compounding a diene-based rubber with titanium oxide, silica and a silane coupling agent in specified proportxons. SOLUTION: This composition is obtained by compounding (A) 100 pts.wt. of a diene-based rubber (pref. natural rubber, butadiene rubber, or isoprene rubber) with (B) 10-50 pts.wt. of titanium oxide, (C) 30-90 pts.wt. of silica, and (D) a silane coupling agent at 5-15 wt.% of the component C [pref. bis(3- triethoxysilylpropyl) tetrasulfide or 3-mercaptopropyltrimethoxysilane]; wherein the component B is pref. of anatase type, with an average particle size of 0.2-0.8 μm, specific gravity of 3.9-4.3, coloring power of 1,200-1,850 and refractive index of 2.5-2.9 and the component C is pref. predominant in silicon dioxide with an average particle size of 0.01-0.05 μm, specific gravity of 2.0-2.2, and refractive index of 1.4-1.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire tread rubber composition colored white.

[0002]

2. Description of the Related Art Conventionally, as a working vehicle such as a forklift truck used in a food factory or a paper mill, a vehicle equipped with white or green color tires is used to prevent contamination of products. However, in recent years, white marking has been performed on sidewalls of tires of passenger cars. As described above, not only the body of the vehicle, but also the aesthetic sense of the tires is increased, and there is a demand that the tread of the passenger car be whitened.

[0003] However, titanium oxide used for whitening the sidewall has a low reinforcing property and has a problem that when it is blended with a tread which is in direct contact with the road surface, it is easily worn. Rubber composition used for tread production,
Generally, it must have a moderate Mooney viscosity. If this is too high, there is a problem that rubber scorching occurs and processing becomes difficult.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a tire tread rubber composition having an appropriate Mooney viscosity, which is used for producing a tire tread which is white and has excellent wear resistance. .

[0005]

Means for Solving the Problems The present inventor has made intensive studies to solve the above-mentioned problems. As a result, titanium oxide is indispensable for coloring in white. The idea was to increase the wear resistance. Then, it was considered that silica having a high reinforcing property was blended as another additive. Furthermore, in order to improve tire performance, we believe that it is necessary to increase the adhesion between titanium oxide and silica and the diene rubber, and in order to select a silane coupling agent for that purpose and optimize the blending amount of each. To
After various experiments, the present invention has been achieved.

That is, the tread rubber composition for a tire of the present invention is used in an amount of 10 to 5 parts by weight based on 100 parts by weight of the diene rubber.
A composition comprising 0 parts by weight of titanium oxide, 30 to 90 parts by weight of silica, and 5 to 15% by weight of the silica of a silane coupling agent.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION First, each component constituting the tread rubber composition for a tire of the present invention will be described in detail, and then the tread rubber composition for a tire will be described. (Diene rubber) Diene rubber used in the present invention,
It is a main component of the tread rubber composition for a tire tread rubber composition.

[0008] The diene rubber is not particularly limited.
For example, natural rubber; styrene-butadiene rubber (SB
R), butadiene rubber (BR), isoprene rubber (I
R), diene-based synthetic rubbers such as isoprene-isobutylene rubber (IIR) and halogenated butyl rubber (X-IIR), and one or more of them can be used. Among these, at least one selected from natural rubber, butadiene rubber and isoprene rubber is preferred, and natural rubber and / or butadiene rubber are more preferred. Natural rubber and isoprene rubber are used to maintain the durability of the rubber, and butadiene rubber is used to increase the wear resistance of a tire not filled with carbon black. Styrene / butadiene rubber generates a large amount of heat due to a large motion of a molecular chain, and a large increase in hardness due to running may cause chipping.

The diene rubber comprises natural rubber and / or isoprene rubber 60 to 80 parts by weight of 100 parts by weight.
It is more preferable that the rubber composition contains a weight part and 20 to 40 weight parts of a butadiene rubber. If the butadiene rubber is less than 20 parts by weight, the abrasion resistance may be reduced. On the other hand, when the butadiene rubber exceeds 40 parts by weight, the breaking strength and the elongation of the tread rubber decrease, and chipping may occur during running. [Titanium oxide] Titanium oxide used in the present invention is a component for coloring the tread rubber in white.

[0010] Titanium oxide is classified into an anatase type and a rutile type depending on the crystal state. In the present invention, the anatase type is preferable. The rutile type generally has a large refractive index and can be colored white in a small amount because of high whiteness.However, since the bulk specific gravity is large and the Mohs hardness is high, the Mooney viscosity of the tread rubber composition increases, It is difficult to handle.

As anatase type titanium oxide, average particle diameter: 0.2 to 0.8 μm, specific gravity: 3.9 to 4.3, coloring power: 1200 to 1850 (JIS K5116-73)
7.2 The value measured by the method according to the item 2), refractive index: 2.
Those of 5 to 2.9 are preferred. [Silica] The silica used in the present invention is a component that enhances the wear resistance of the tread rubber.

Silica contains silicon dioxide as a main component.
As silica, average particle diameter: 0.01 to 0.05 μ
m, specific gravity: 2.0 to 2.2, and refractive index: 1.4 to 1.5 are preferable. (Silane coupling agent) The silane coupling agent used in the present invention, by chemically bonding titanium oxide and silica with a diene rubber, supplementarily enhances the wear resistance of the tread rubber, and also has a Mooney viscosity. It is a component that is supplementarily adjusted.

The silane coupling agent is not particularly limited. Examples thereof include bis (3-triethoxysilylpropyl) tetrasulfide (Si69, manufactured by Shin-Etsu Chemical Co., Ltd.),
3-mercaptopropyltrimethoxysilane (A-18
9, Degussa Japan), 2-mercaptoethyltrimethoxysilane, and the like, and one or more kinds are used. Among these, bis (3-triethoxysilylpropyl) tetrasulfide has a long scorch and high processability. In addition, 3-mercaptopropyltrimethoxysilane is white and transparent, and can be used for a white tire whose non-staining property is preferable. [Tread rubber composition for tire] The compounding amounts of the respective components constituting the tread rubber composition for a tire of the present invention will be described.

The mixing ratio of titanium oxide is as follows.
The amount is 10 to 50 parts by weight, preferably 30 to 50 parts by weight, of titanium oxide with respect to 00 parts by weight. If the blending ratio of titanium oxide is less than 10 parts by weight with respect to 100 parts by weight of the diene rubber, the blending amount is too small and sufficient whiteness cannot be obtained. On the other hand, 5 parts per 100 parts by weight of diene rubber
If the amount exceeds 0 parts by weight, sufficient whiteness is already obtained at the time when 50 parts by weight is blended, and even if more than 50 parts by weight is blended, whiteness corresponding to the blending amount cannot be obtained only by increasing the cost. In addition, wear resistance and dispersibility decrease.

The mixing ratio of the silica is as follows.
The silica is used in an amount of 30 to 90 parts by weight, preferably 30 to 70 parts by weight, based on parts by weight. When the compounding ratio of silica is less than 30 parts by weight with respect to 100 parts by weight of the diene rubber, abrasion resistance decreases. On the other hand, if it exceeds 90 parts by weight with respect to 100 parts by weight of the diene rubber, the Mooney viscosity becomes high and rubber scorch may occur. Further, when a roll is used at the time of manufacturing the rubber composition, winding is poor and the adhesiveness at the time of molding is reduced. In a tire obtained by calendering, peeling may occur between rubber layers after vulcanization.

The compounding ratio of the silane coupling agent is 5 to 15% by weight of silica, preferably 5 to 10% by weight.
It is. If the compounding ratio of the silane coupling agent is less than 5% by weight, the abrasion resistance is reduced. On the other hand, when the compounding ratio of the silane coupling agent exceeds 15% by weight, the reinforcing effect reaches saturation, the Mooney viscosity increases, the processability deteriorates, and the compounding cost increases.

The tread rubber composition for a tire of the present invention may contain, if necessary, a reinforcing agent such as carbon black; a softening agent such as a naphthenic process oil; a vulcanizing agent such as sulfur, insoluble sulfur or a sulfur compound; Vulcanization aids such as zinc and stearic acid; mercaptobenzothiazole (MBT);
Benzothiazyl disulfide (MBTS), N-ter
Thiazole accelerators such as t-butyl-2-benzothiazolylsulfenamide (TBBS) and N-cyclohexyl-2-benzothiazylsulfenamide (CBS), and guanidine accelerators such as diphenylguanidine (DPG). Vulcanization accelerators such as polyethylene glycol and the like; organic fibers; foaming agents; antioxidants; vulcanization retardants; and additives such as waxes. The amounts of these additives in the tread rubber composition are not particularly limited, and can be appropriately used.

As a method for producing the tread rubber composition for a tire of the present invention, a known method can be applied.
The above-mentioned components are obtained by kneading under ordinary methods and conditions using, for example, a kneader such as a Banbury mixer or a twin-screw roller. The kneading temperature is 80 to
Preferably it is 150 ° C. The obtained kneaded material is vulcanized at, for example, 140 to 170 ° C. for 10 to 50 minutes to obtain the tread rubber composition for a tire of the present invention.

By molding and vulcanizing using the tread rubber composition for a tire of the present invention, a tire having a tread colored white can be obtained.

[0020]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. However, the present invention is not limited to the following Examples. In the following, "part" indicates "part by weight" and "%" indicates "% by weight". -Example 1-Natural rubber (trade name: RSS # 3, TECK BEE H
ANG) 60 parts, butadiene rubber (BR150B,
40 parts of Ube Industries, 40 parts of titanium oxide (KR-380, manufactured by Titanium Industries), silica (Ultrasil VN-)
3, 40 parts of Nippon Degussa Co., Ltd., 2 parts of bis (3-triethoxysilylpropyl) tetrasulfide (Si69, manufactured by Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent (5% by weight based on silica), an antioxidant Phenol (SP-P, manufactured by Kawaguchi Chemical Co., Ltd.) 3.08
Part, wax (trade name: Sunnock N, manufacturer: Ouchi Shinko Chemical Co., Ltd.), 1 part, stearic acid (tung, Nippon Oil & Fats Co., Ltd.), 1 part, zinc oxide (Ginrei, Toho Zinc Co., Ltd.), 1 part, processing 2.2 parts of polyethylene glycol as an auxiliary agent and 0.8 parts of phthalic anhydride (Sconok 5, manufactured by Ouchi Shinko Chemical Co., Ltd.) as a vulcanization retarder were prepared, and a 1.7-liter Banbury mixer ( Kobe Steel)
The mixture was kneaded at about 150 ° C. for 5 minutes. The titanium oxide used above was an anatase type and had a Mohs hardness of 5.5 to 5.5.
6.0, specific gravity: 3.9, refractive index: 2.52, coloring power: 1
300, hiding power: 100 to 135, average particle size: 0.3
０．４0.4 μm. In addition, coloring power is JIS K5
116-73 This is a value measured by a method according to 7.2, and a coloring pigment (1 part of ultramarine blue and 6 parts of sedimentable calcium carbonate) and purified linseed oil are added to the sample.
Knead with a spatula on a glass plate, process the standard product in the same way, compare the colors on the object glass, and if the colors do not match, increase or decrease the color pigment added to the sample to make it the same color The amount of the coloring pigment was determined and measured. The hiding power is a value measured by the method described in 8.1 of JIS K5101.

The kneaded product obtained above was mixed with 2.5 parts of sulfur (Seimi Sulfur, manufactured by Tsurumi Kagaku) and N-tert-butyl-2-benzothiazoyl-sulfenamide (NS) as a vulcanization accelerator. 0.94 parts), and kneaded at 80 ° C. for about 4 minutes using a biaxial roller.
It was vulcanized at 150 ° C. for 45 minutes to prepare a tread rubber composition (1) for a tire.

The Mooney viscosity of the tire tread rubber composition (1) and the tire tread rubber composition (1)
Whiteness of the vulcanized rubber (1) obtained by vulcanizing at 0 ° C. for 45 minutes,
With respect to wear resistance and mechanical properties, performance was evaluated by the following evaluation methods. Table 1 shows the results. <Evaluation method> L * a * using chromaticity measurement chromaticity / color difference meter (manufactured by MINOLTA)
b Color System Chromaticity Diagram-Measured based on CIE 1967 L * a * b color system (JIS Z8729- (1980)). The measurement result was calculated using an index with the result of Example 1 being 100. When there is a difference of 10 or more in the numerical values, it can be considered that there is a remarkable difference. Wear Test Lambourn abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.) using, JI
It was measured based on SK6264. The measurement result was calculated using an index with the result of Example 1 being 100. Mooney viscosity The Mooney viscosity at 130 ° C. (ML _{1 + 4} ) was measured based on JIS K6300. Tensile test Based on JIS K6251, using a dumbbell No. 3, breaking strength (unit: MPa) and elongation (unit:%)
Was measured.

Example 2 A tire tread rubber composition (2) was prepared in the same manner as in Example 1 except that titanium oxide was changed from anatase type to rutile type. The performance of the vulcanized rubber (2) obtained by vulcanizing the tread rubber composition for a tire (2) was evaluated in the same manner as in Example 1. Table 1 shows the results.

The rutile type titanium oxide has a Mohs hardness of 6.0 to 7.0, a specific gravity of 4.2, and a refractive index of 2.7.
1, coloring power: 1800, hiding power: 130 to 190, average particle diameter: 0.3 to 0.4 μm. The coloring power and the hiding power are values measured by the same method as in Example 1. -Examples 3 to 7 and Comparative Examples 1 to 6 Tread rubber compositions for tires in the same manner as in Example 1 except that the compounding amount is changed to the amounts shown in Tables 1 and 2, respectively. (3) to (7) and tread rubber compositions (1) to (6) for comparative tires were prepared.

Tread rubber composition (3) for tire
(7) and a tread rubber composition for comparative tires (1) to
Vulcanized rubber (3)-obtained by vulcanizing (6) respectively
The performance of (7) and the comparative vulcanized rubbers (1) to (6) were evaluated in the same manner as in Example 1. Table 1 shows the results.
And Table 2.

[0026]

[Table 1]

[0027]

[Table 2]

* 1 The weight in parentheses indicates% by weight based on silica. * 2 In Example 2, rutile type titanium oxide was used, and other than this, anatase type titanium oxide was used. <Evaluation Results> In Examples 1 to 7, the whiteness and abrasion resistance were high and the Mooney viscosity was moderate, whereas Comparative Examples 1 and 6 had low whiteness and Comparative Examples 2 to 3 And 5
, The abrasion resistance is low, and in Comparative Examples 4 and 6, the Mooney viscosity is too high.

From the comparison between Example 1 and Example 2, rutile-type titanium oxide has higher whiteness than anatase-type titanium oxide, but has a higher Mooney viscosity and slightly lower handleability. From comparison between Example 1 and Example 5, when the proportion of butadiene rubber is large, the abrasion resistance increases, but the breaking strength and elongation slightly decrease.

From the comparison between Example 1 and Example 6, when the mixing ratio of silica is large, the abrasion resistance is increased, but the Mooney viscosity is slightly lowered.

[0031]

The tire tread rubber composition of the present invention is used for producing a tire tread excellent in abrasion resistance which is white and has an appropriate Mooney viscosity.

Claims (1)

[Claims] 1 to 10 parts by weight of a diene rubber.
A tread rubber composition for a tire, comprising 50 parts by weight of titanium oxide, 30 to 90 parts by weight of silica, and 5 to 15% by weight of the silica of a silane coupling agent.