JP2007246640A - Rubber composition for tire and tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition exhibiting high ozone resistance, flex fatigue resistance, whiteness degree and processability by itself after vulcanization and useful for forming a white rubber part used in various members of a tire, especially a sidewall part of the tire. <P>SOLUTION: The rubber composition for the tire comprises a rubber component composed of an ethylene-propylene-diene terpolymer rubber, a halogenated butyl rubber and a diene-based rubber. The rubber composition for the tire is characterized by comprising ≥20 pts.wt. of the ethylene-propylene-diene terpolymer rubber and >60 pts.wt. of the halogenated butyl rubber based on 100 pts.wt. of the sum total of the ethylene-propylene-diene terpolymer rubber, the halogenated butyl rubber and the diene-based rubber. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rubber composition for tires, and more specifically, exhibits high ozone resistance, bending fatigue resistance, whiteness and workability by itself after vulcanization, and is applied to various members of tires, particularly tire sidewalls. The present invention relates to a tire rubber composition useful for forming a white rubber portion to be used.

  As a rubber material for tires, a diene rubber such as natural rubber is generally used because of characteristics such as wear resistance and durability. On the other hand, at least part of the outer surface of the tire, especially the sidewall, is generally called white line or white letter, such as characters such as manufacturer name and brand name, and various lines and patterns for decoration A white rubber part is formed. When the white rubber portion is provided on the sidewall portion of the tire, it is susceptible to deterioration due to ozone, ultraviolet rays, etc., and therefore, it is required to have high weather resistance, and ethylene-propylene butadiene having excellent weather resistance. It has been studied to blend terpolymer rubber (EPDM) and / or halogenated butyl rubber (X-IIR). However, although EPDM has excellent weather resistance, it has a slower vulcanization rate than diene rubber and is inferior in co-vulcanizability with diene rubber. When EPDM is blended with diene rubber, it is weather resistant. However, the mechanical properties such as bending fatigue resistance and the degree of vulcanization cannot be improved. On the other hand, it is conceivable to add an anti-aging agent to further improve the weather resistance, but the anti-aging agent impairs the decorative effect brought about by the use of the white rubber part due to its blooming, such as an amine anti-aging agent. Even if non-fouling anti-aging agents (such as phenolic anti-aging agents, hindered amine anti-aging agents, etc.) are used so as not to impair the decorative effect brought about by the white rubber part, ozone resistance is maintained. A compound selected from the group consisting of a specific thiuram compound and a specific dithiocarbamate compound with respect to 100 parts by weight of a rubber component consisting of EPDM, a halogenated butyl rubber and a diene rubber, and a benzothiazole vulcanization accelerator And non-contaminating rubber with excellent properties such as co-curability, weather resistance, and bending fatigue resistance. Compositions have been proposed (Patent Document 1).

  In Patent Document 2, a relatively small amount of halogenated butyl rubber is added to a blend of EPDM and highly unsaturated rubber, that is, 15 to 30% by weight based on the total amount of EPDM, highly unsaturated rubber and halogenated butyl rubber. By doing so, it is described that the dynamic ozone resistance and heat bending resistance of the blend of EPDM and highly unsaturated rubber are improved.

  Patent Document 3 describes that, in the polymer blend described in Patent Document 2, the cleanliness of the white sidewall is increased by increasing the EPDM content.

  In Patent Document 4, as a rubber composition for forming a pattern portion on a sidewall portion of a tire, 20 to 60 parts by weight of a diene rubber, 20 parts by weight or more of a halogenated butyl rubber in 100 parts by weight of a rubber component, and It has been proposed to use a bright colored rubber containing 20 parts by weight or more of EPDM to form a pattern that is rich in variety and durable.

  Patent Document 5 includes 10 to 60 parts by weight of an ethylene copolymer rubber, 10 to 70 parts by weight of a conjugated diene rubber, 10 to 60 parts by weight of a halogenated butyl rubber, and 10 to 150 parts by weight of a white filler. By compounding, the rubber composition for tires with excellent properties such as processing characteristics, weather resistance, ozone resistance, fatigue resistance, and low heat build-up without substantially impairing the damping properties inherent in conjugated diene rubbers It has been proposed to provide things.

  In Patent Document 6, a white filler selected from the group consisting of fibrous zonotlite and magnesium oxysulfate whisker is added as a white filler to 100 parts by weight of a rubber component containing 20 parts by weight or more of a halogenated butyl rubber. It has been proposed to provide a white rubber composition excellent in processability, whiteness and rubber properties.

  In Patent Document 7, non-contaminating or slightly contaminating rubber that does not contain a fouling anti-aging agent is used as a cover sheet for a coloring decoration part for a coloring decoration part formed from a white rubber composition containing EPDM. At the same time, it is possible to achieve both prevention of staining and prevention of bending fatigue by attaching decorative parts to side wall rubber via inner rubber with excellent resistance to bending fatigue to improve bending fatigue resistance. Proposed. However, the colored decorative portion described in this patent document requires a cover sheet and an inner layer rubber separately from the colored decorative portion in order to prevent contamination of the decorative portion and prevention of bending fatigue. Therefore, it is inferior to productivity and workability.

Japanese Patent No. 3202782 U.S. Pat. No. 3,630,974 JP-A-55-003478 Japanese Patent Laid-Open No. 7-164832 JP 2000-72939 A JP 2002-309053 A Japanese Patent No. 2971545

  Accordingly, the object of the present invention is to provide high ozone resistance, bending fatigue resistance, whiteness and workability by itself after vulcanization, and a white rubber portion used for various parts of tires, particularly tire sidewalls. It is an object to provide a rubber composition useful for forming.

  As a result of diligent research to solve the above problems, the present inventor has found that in a rubber composition containing a rubber component composed of EPDM, a halogenated butyl rubber and a diene rubber, EPDM per 100 parts by weight of the total amount of these rubber components. It has been found that when the amount of styrene is 20 parts by weight or more and the amount of halogenated butyl rubber is more than 60 parts by weight, the bending fatigue resistance, whiteness and workability are improved while maintaining good ozone resistance. The invention has been completed.

  According to the present invention, a tire rubber composition comprising a rubber component comprising EPDM, a halogenated butyl rubber, and a diene rubber, wherein the EPDM is 20 per 100 parts by weight in total of EPDM, the halogenated butyl rubber, and the diene rubber. There is provided a rubber composition for a tire characterized by containing at least part by weight and more than 60 parts by weight of the halogenated butyl rubber.

  In the tire rubber composition of the present invention, EPDM is a copolymer of ethylene and propylene, and further has a non-conjugated diene monomer as a third component. There is no particular condition for the composition of EPDM, and those generally used can be used. In the rubber composition of the present invention, EPDM is blended in an amount of 20 parts by weight or more per 100 parts by weight of a rubber component composed of EPDM, halogenated butyl rubber and diene rubber.

  The halogenated butyl rubber used in the tire rubber composition of the present invention is selected from chlorinated butyl rubber (Cl-IIR), brominated butyl rubber (Br-IIR), and combinations thereof. In the tire rubber composition of the present invention, the halogenated butyl rubber is blended in an amount of more than 60 parts by weight, preferably 65 parts by weight, per 100 parts by weight of the rubber component composed of EPDM, halogenated butyl rubber and diene rubber. When the amount of the halogenated butyl rubber in the rubber component is 60 parts by weight or less, the whiteness, bending fatigue resistance, and ozone resistance are not improved.

  Specific examples of the diene rubber used in the tire rubber composition of the present invention include natural rubber (NR), polyisoprene rubber (IR), polybutadiene rubber (BR), and styrene-butadiene copolymer rubber (SBR). Examples thereof include diene rubbers that have been generally blended in tire rubber compositions such as acrylonitrile-butadiene copolymer rubber (NBR) and chloroprene rubber (CR). In the rubber composition of the present invention, as described above, EPDM is blended in an amount of 20 parts by weight or more per 100 parts by weight of the rubber component composed of EPDM, halogenated butyl rubber and diene rubber, and the halogenated butyl rubber exceeds 60 parts by weight. Therefore, the diene rubber is blended in an amount of less than 20 parts by weight.

  When the rubber composition for tires of the present invention is used to form a white rubber layer used for a sidewall portion of a tire, white carbon generally used for making the rubber composition white White fillers such as calcium carbonate, aluminum oxide, titanium oxide, and clay can be used. When a white filler is added to the rubber composition of the present invention, the white filler is preferably added in an amount of 30 to 100 parts by weight per 100 parts by weight of the rubber component. A small amount of ultramarine blue may be further added to the rubber composition of the present invention in order to make the degree of whiteness seen by human eyes more vivid. Further, in order to color at least a part of the outer surface of the tire, in addition to the white filler as described above, other colorants may be added to the tire rubber composition of the present invention as necessary. .

  The tire rubber composition according to the present invention includes, in addition to the above components, a vulcanization acceleration aid such as zinc oxide, a vulcanization agent such as sulfur, a vulcanization accelerator, and talc, unless the object of the present invention is impaired. Such as non-reinforcing fillers, reinforcing fillers, process oils such as naphthenic oils, softeners, plasticizers, and other various additives that are commonly compounded for tires, and such compounds Can be produced by vulcanization by a general method. The blending amount of these additives can also be a general amount.

  The rubber composition according to the present invention can be obtained by kneading each of the above components according to a conventional method, for example, using a kneader such as a Banbury mixer, a kneader, or a roll. By vulcanizing the rubber composition according to a conventional method, as described above, a vulcanized rubber composition exhibiting excellent ozone resistance, bending fatigue resistance and whiteness is provided.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, it cannot be overemphasized that the scope of the present invention is not limited to these Examples.

Comparative Example and Examples 1-4
According to the formulation shown in Table 1 below, the vulcanization accelerator and the components excluding sulfur were mixed for 6 minutes with a 2 liter kneader. Thereafter, a vulcanization accelerator and sulfur were added and mixed for 3 minutes to obtain a rubber composition. The degree of vulcanization was evaluated using this rubber composition. Next, the obtained rubber composition was vulcanized at 160 ° C. for 15 minutes in a mold to prepare a sample, and the whiteness, bending fatigue resistance and ozone resistance were measured by the following test methods.

Test method 1. Whiteness According to JIS Z8722, the brightness index L ^* value in the CIE 1976 (L ^* , a ^* , b ^* ) color space was determined, and the L ^* value was expressed as whiteness.
2. Vulcanization degree Using a rheometer (DISK RHEOMETER manufactured by Toyo Seiki Seisakusho Co., Ltd.), the change with time in viscosity was tracked at 160 ° C., and the time T95 required to obtain 95% of the maximum torque value was determined. The degree of vulcanization for Examples 1 to 4 was expressed as a relative value when the value of T95 obtained for Comparative Example 1 was taken as 100. The smaller the value of T95, the faster the vulcanization speed, the better the workability, and the more preferable.
3. Flexural fatigue resistance Flexural fatigue resistance was determined in accordance with ASTM D430. It was expressed as a relative value when the number of flexing until the crack of Comparative Example 1 was set was 100. It shows that it is excellent in bending fatigue resistance, and it is more preferable, so that this relative value is large.
4). Ozone resistance Based on the ozone deterioration test method of JIS K6301, the ozone resistance was determined at an ozone concentration of 50 ppm and a temperature of 40 ° C. When the occurrence of cracks was not observed, “good” was shown in the table. Less cracking is preferable as the rubber used for the side portion of the tire.
The test results are shown in Table 2 below.

  From the results shown in Table 2, in the rubber composition composed of EPDM, halogenated butyl rubber and diene rubber as rubber components, the amount of EPDM is 20 parts by weight or more per 100 parts by weight of the total amount of these rubber components. It can be seen that, when the amount of A exceeds 60 parts by weight, the bending fatigue resistance, the whiteness, and the workability are improved while maintaining good ozone resistance.

Claims (4)

  A rubber composition for a tire comprising a rubber component comprising an ethylene-propylene-diene terpolymer rubber, a halogenated butyl rubber and a diene rubber, the ethylene-propylene-diene terpolymer rubber and the rubber A tire rubber comprising 20 parts by weight or more of the ethylene-propylene-diene terpolymer rubber and more than 60 parts by weight of the halogenated butyl rubber per 100 parts by weight in total of the halogenated butyl rubber and the diene rubber. Composition.   The tire rubber composition according to claim 1, wherein the tire rubber composition further contains a white filler.   The tire rubber composition according to claim 1 or 2, wherein the halogenated butyl rubber is selected from the group consisting of chlorinated butyl rubber, brominated butyl rubber, and combinations thereof.   A tire comprising the tire rubber composition according to any one of claims 1 to 3 disposed on at least a part of an outer surface.