JP2002212363A - Rubber composition for tire inner liner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a rubber composition for a tire inner liner having high preventing properties of air permeation and a high green strength without deteriorating processability. SOLUTION: This rubber composition for the tire inner liner is obtained by compounding 3-15 pts.wt. of an isobutylene polymer or a modified isobutylene polymer having 3,000-20,000 number-average molecular weight with 100 pts.wt. of a raw material rubber comprising >=70 pts.wt. of a butyl rubber or a halogenated butyl rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for an inner liner used for a pneumatic tire, and more particularly, to a rubber for a tire inner liner having high gas permeability and high green strength without impairing processability. Composition.

[0002]

2. Description of the Related Art An inner liner for a radial tire, particularly for a tubeless radial tire, has a function of retaining air inside the tire by being arranged on an inner inner surface of the tire. Therefore, the most important performance of the rubber composition used for the inner liner is gas permeation resistance. However, it is also an important requirement that the rubber composition can be easily processed into a sheet as thin as possible for the purpose of reducing the weight of the vehicle for fuel economy. It is useful to have low viscosity for workability, but on the other hand, it came into contact with a carcass (usually composed of yarn, wire and coated rubber that covers it) that is placed inside the inner liner and serves to support tire strength Occasionally hard to bite between yarn and wire (Usually, inner liner rubber uses butyl rubber or halogenated butyl rubber to increase gas permeation resistance, but these have poor adhesion to yarn or wire. ), Higher green strength is also required.

However, heretofore, a rubber composition for an inner liner having high green strength and high gas permeation resistance while maintaining low viscosity has not been obtained. It is well known that halogenated butyl rubber is used to obtain high gas permeation resistance.However, when halogenated butyl rubber is used, a softener such as oil is blended in order to lower the viscosity. The use of halogenated butyl rubber having a low viscosity has been proposed, but in these cases, there is a problem that the green strength of the rubber composition is reduced, and the desired rubber composition has not been obtained.

[0004]

SUMMARY OF THE INVENTION The present invention provides a rubber composition for an inner liner used for a pneumatic tire having both high gas permeability and high green strength without increasing the viscosity of the rubber composition. The purpose is to do.

[0005]

According to the present invention, a number average molecular weight of 3,000 to 2 is used for 100 parts by weight of a raw rubber containing 70 parts by weight or more of butyl rubber or halogenated butyl rubber.
The present invention provides a rubber composition for a tire inner liner, comprising 3 to 15 parts by weight of 0000 isobutylene-based polymer or modified isobutylene-based polymer.

[0006]

According to the present invention, the object of the present invention can be achieved by using a low molecular weight butyl-based polymer instead of a softening agent such as oil conventionally compounded in butyl rubber or halogenated butyl rubber. .

The raw rubber used in the rubber composition of the present invention contains 70 parts by weight or more, preferably 80 parts by weight or more of butyl rubber or halogenated butyl rubber with 100 parts by weight of the raw rubber. If the amount is too small, sufficient air permeation resistance required for the inner liner rubber cannot be obtained, which is not preferable. As the rubber other than butyl rubber or halogenated butyl rubber, any rubber conventionally used for tire inner liners, for example, natural rubber (NR), polyisoprene rubber (IR), various styrene-butadiene copolymer rubbers (SBR) ), Various polybutadiene rubbers (BR), acrylonitrile-butadiene copolymer rubbers (NBR), and diene rubbers such as butyl rubber (IIR) can be used alone or as an arbitrary blend.

The butyl rubber or halogenated butyl rubber (for example, brominated or chlorinated butyl rubber) blended as a main component in the rubber composition for a tire inner liner according to the present invention has been generally used in rubber compositions for a tire inner liner. Butyl rubber or halogenated butyl rubber. Butyl rubber is widely commercially available, and commercially available products such as butyl 301 from Bayer and JSR268 from Japan Synthetic Rubber Co., Ltd. can be used.

The halogenated butyl rubber is obtained by halogenating the butyl rubber with bromine, chlorine, or the like, and is also widely commercially available. it can.

In the present invention, as described above, the butyl rubber or the halogenated butyl rubber may have a number average molecular weight of 3000 to 20,000, preferably 4 instead of a conventional softener.
000 to 17000 isobutylene-based polymer or modified isobutylene-based polymer is blended. If the molecular weight is too low, the green strength becomes too low, so that yarns and wires of adjacent members are likely to penetrate, which is not preferable. Conversely, if the molecular weight is too high, the viscosity becomes high, and it becomes difficult to process as a thin sheet, which is not preferable. . Isobutylene-based polymer or modified isobutylene-based polymer is used as raw material rubber 1
3 to 15 parts by weight, preferably 3 to 10 parts by weight, per 100 parts by weight
Mix by weight. If the amount is too small, the rubber composition has a high viscosity, which is not preferable. On the other hand, if the amount is too large, only low green strength is obtained, which is not preferable.

In the present invention, the isobutylene-based polymer blended in the raw rubber containing butyl rubber or halogenated butyl rubber can be produced, for example, by cationic living polymerization capable of controlling the molecular weight and molecular weight distribution.
The isobutylene-based polymer may be modified by introducing a functional group such as an olefin group, an alkoxysilyl group, or an allyl group into the terminal or the like.

[0012] These isobutylene-based polymers are commercially available. For example, Epiion (both terminal-reactive polyisobutylene oligomer) available from Kaneka Chemical Industry Co., Ltd. can be used.

In the rubber composition for a tire inner liner according to the present invention, in addition to the above essential components, any compounding agent usually used in the rubber industry, for example, a reinforcing filler, sulfur, an organic peroxide, antiaging, Agents, vulcanization accelerators, fillers, plasticizers, etc., as necessary, as long as the object of the present invention is not impaired,
It can be appropriately blended within the usual range of the blending amount. Further, the rubber composition for an inner liner of the present invention can be produced using a conventional production method and apparatus.

[0014]

EXAMPLES The present invention will be further described with reference to the following examples, but it goes without saying that the scope of the present invention is not limited to these examples.

Examples 1 to 3 and Comparative Examples 1 to 4 In the formulations (parts by weight) shown in Table I, each component except for the vulcanization system and zinc oxide (zinc oxide) was mixed in a 1.8-liter closed mixer. The mixture was kneaded for 5 minutes and released when the temperature reached 160 ± 5 ° C. to obtain a master batch.

Next, zinc white, a vulcanization accelerator and sulfur were kneaded with this rubber composition using an 8-inch open roll to obtain a rubber composition. The unvulcanized physical properties of this rubber composition were measured by the following methods, and the results are shown in Table I. Further, this composition was press-vulcanized in a mold of 15 × 15 × 0.2 cm at 160 ° C. for 20 minutes to prepare a target test piece (rubber sheet), and the vulcanization properties were evaluated by the following methods. did. The results are shown in Table I.

Viscosity of unvulcanized rubber composition According to JIS K6300, Mooney viscosity (ML _{I + 4} , 1
00 ° C) at 100 ° C. It is shown by an index when Comparative Example 1 is set to 100.

Green strength of unvulcanized rubber An unvulcanized sheet having a thickness of 2 mm was prepared by a cold press, and JI
It was measured at room temperature according to SK6251. The 300% modulus was used as an index of strength, and the index was shown as an index when Comparative Example 1 was set to 100.

Gas Permeability of Vulcanized Rubber Gas Permeability described in "Rubber Test Method" published by The Rubber Association of Japan
The amount of permeation was determined based on the pressure method, and was indicated by an index when Comparative Example 1 was set to 100. The larger the value, the better the gas permeation resistance.

[0020]

[Table 1]

[0021]

As described above, according to the present invention, by blending a low molecular weight isobutylene-based polymer as a softener with butyl rubber or halogenated butyl rubber, the viscosity of the rubber composition before vulcanization can be increased. A rubber composition for a tire inner liner having high green strength and high air permeability can be obtained.

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Claims (1)

[Claims] 1. A tire comprising 100 parts by weight of raw rubber containing 70 parts by weight or more of butyl rubber or halogenated butyl rubber, and 3 to 15 parts by weight of an isobutylene-based polymer or a modified isobutylene-based polymer having a number average molecular weight of 3,000 to 20,000. Rubber composition for inner liner.