JP2002088208A - Rubber composition for inner liners - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for use in inner liners of pneumatic tires with excellent air permeation resistance and improved processability, and to provide, by using the composition, an pneumatic tire that allows its inner liner to reduce the gauge to a great extent, while preserving the inner pressure preserving characteristics. SOLUTION: A rubber component comprising 40-100 wt.% of a halogenated butyl rubber and <60 wt.% of a diene rubber is compounded with a layered or planar mineral such as kaolin or clay to form a rubber composition for use in inner liners of pneumatic tires. A pneumatic tire is prepared by using the composition.

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 of a pneumatic tire, and more particularly to a rubber composition having a halogenated butyl rubber containing a specific compounded rubber composition for an inner liner of a pneumatic tire. An object of the present invention is to provide a rubber composition for an inner liner having excellent air permeability and improved processability, and a pneumatic tire that can be reduced in weight using the same.

[0002]

2. Description of the Related Art Conventionally, an inner liner layer made of a low gas permeable rubber such as halogenated butyl rubber is provided on the inner surface of a pneumatic tire to prevent air leakage and keep the tire air pressure constant. However, if the content of butyl rubber is increased, the strength of the unvulcanized rubber is reduced, and it is easy to cause rubber breakage and sheet holes, etc.In particular, when thinning the inner liner, the inner surface Is easily exposed. On the other hand, with the social demands for energy saving in recent years, techniques for reducing the thickness of the inner liner layer have been proposed for the purpose of reducing the weight of automobile tires. For example, JP-A-7-4
No. 0702 and JP-A-7-81306 disclose a method in which a nylon film layer or a vinylidene chloride layer is used as an inner liner layer instead of conventional butyl rubber. Also, JP-A-10-26407 discloses that
It is disclosed that a film of a composition comprising a blend of a thermoplastic resin such as a polyamide resin or a polyester resin and an elastomer is used. However, in the method using these films, even though the weight of the tire can be reduced to some extent, the matrix material is a crystalline resin material. There is a disadvantage that the flex fatigue is inferior to that of the normally used butyl rubber compound composition layer,
Tire manufacturing is also complicated.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rubber composition for an inner liner which is excellent in air permeation resistance and has improved processability of an unvulcanized rubber under such circumstances. It is assumed that. In addition, the present invention makes it possible to significantly reduce the thickness of the inner liner while maintaining the internal pressure of the tire by using such a rubber composition, and also has good crack resistance and bending fatigue resistance even at low temperatures. It is an object of the present invention to provide a pneumatic tire having the property.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to develop a rubber composition for an inner liner having the above-mentioned preferable properties, and as a result, a specific rubber containing a layered or plate-like mineral has been obtained. It has been found that the purpose can be achieved by using the composition. The present invention has been completed based on such findings. That is, the present invention
An object of the present invention is to provide a rubber composition for an inner liner of a pneumatic tire, which is obtained by mixing a layered or plate-like mineral with a rubber component comprising 40 to 100% by weight of a halogenated butyl rubber and less than 60% by weight of a diene rubber. The present invention also provides a pneumatic tire using the rubber composition for an inner liner.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION As the rubber component used in the rubber composition of the present invention, a halogenated butyl rubber alone may be used as long as it contains 40% by weight or more of a halogenated butyl rubber. It may be a blend. If the content of the halogenated butyl rubber in this rubber component is less than 40% by weight, sufficient air permeation resistance cannot be exhibited.

[0006] The halogenated butyl rubber includes chlorinated butyl rubber, brominated butyl rubber, and modified rubber thereof. For example, as chlorinated butyl rubber, "Enja
"YButyl HT10-66" (trademark, manufactured by Enge Chemical Co., Ltd.), and "bromobutyl 2255" (trademark, manufactured by Exxon Corp.) as a brominated butyl rubber. Further, a chlorinated or brominated modified copolymer of a copolymer of isomonoolefin and paramethylstyrene can be used as the modified rubber, and is available as, for example, "Expro50" (trademark, manufactured by Exxon). . Examples of the diene rubber blended with the halogenated butyl rubber include natural rubber and isoprene synthetic rubber (I).
R), cis 1,4-polybutadiene (BR), syndiotactic-1,2-polybutadiene (1, BR),
Styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (C
R) and the like, and these may be used alone or in combination of two or more.

The layered or plate-like mineral to be blended in the rubber composition of the present invention may be any of natural products and synthetic products, and is not particularly limited. For example, kaolin, clay, mica, feldspar, silica and A water-containing complex of alumina and the like can be mentioned. Among these, kaolin clay and mica are preferred, and kaolin clay is particularly preferred. These layered or plate-like minerals usually have a particle size of 0.2 to 2 μm, and particularly preferably have an aspect ratio of 5 to 30, and more preferably 8 to 20. If the aspect ratio is less than 5, the effect of modifying the air permeability may not be sufficient, and if the aspect ratio is 30 or more, workability may be deteriorated. In the present invention, the compounding amount of the lamellar or plate-like mineral is preferably more than 200 parts by weight and not more than 320 parts by weight based on 100 parts by weight of the rubber component. When the amount is less than 200 parts by weight, the effect of improving the air permeation resistance is small.
If the amount exceeds the weight part, workability may be deteriorated.

[0008] The carbon black used in the rubber composition of the present invention is 0 to 100 parts by weight of the rubber component.
It is preferably 40 parts by weight, more preferably 5 to 35 parts by weight. The type of carbon black is not particularly limited, and any one can be appropriately selected and used from those conventionally used as reinforcing fillers for rubber.
For example, FEF, SRF, HAF, ISAF, SAF and the like can be mentioned. Among these, the nitrogen adsorption specific area (N ₂ S
A) is preferably 26 to 170 m ² / g. In addition,
N ₂ SA is measured according to ASTM D3037-88. Furthermore, when these carbon blacks are blended, the naphthenic oil or the paraffinic oil is used in an amount of 1 part by weight or more, especially 3 to 2 parts by weight, per 100 parts by weight of the rubber component.
It is preferable to add 0 parts by weight. Here, the naphthenic oil has a% _CN of 30 or more by ring analysis,
The paraffin oil has a% _CP of 60 or more.
The total amount of the layered or plate-like mineral and carbon black is preferably 60 to 360 parts by weight in consideration of air permeability, bending fatigue resistance and workability.

Further, in the rubber composition of the present invention, in order to improve the dispersibility of the layered or plate-like mineral in the rubber,
If desired, a dispersion improving agent such as a silane coupling agent, dimethylstearylamine or triethanolamine can be added. Further, when organic short fibers are blended, the inner cord exposure that occurs when a tire is manufactured by reducing the thickness of the inner liner can be suppressed. The organic short fibers preferably have an average diameter of 1 to 100 μm and an average length of about 0.1 to 0.5 mm. This organic short fiber is FRR (composite of short fiber and unvulcanized rubber)
May be blended. The amount of such organic short fibers is preferably 0.3 to 15 parts by weight. If the amount is less than 0.3 parts by weight, the effect of eliminating the inner surface cord exposure is small, and if it exceeds 15 parts by weight, workability may be adversely affected. The material of the organic short fiber is not particularly limited, and examples thereof include polyamides such as nylon 6, nylon 66, syndiotactic-1,2-polybutadiene, isotactic polypropylene, and polyethylene. And polyamide are preferred. Further, in order to increase the modulus of the rubber compounded with organic short fibers, an adhesion improver between the rubber and the fiber, such as hexamethylenetetramine or resorcinol, can be further compounded. In the rubber composition of the present invention, in addition to the above-mentioned compounding agents, as long as the object of the present invention is not impaired,
Various chemicals usually used in the rubber industry, such as vulcanizing agents,
Vulcanization accelerators, anti-aging agents, anti-scorch agents, zinc white, stearic acid and the like can be added.

[0010] The rubber composition of the present invention thus obtained is used as a rubber composition for an inner liner of a tire. Further, the pneumatic tire of the present invention is manufactured by a usual method using the rubber composition. That is, if necessary, the rubber composition of the present invention containing various chemicals as described above is extruded as an inner liner member at an unvulcanized stage, and the inner liner is thinned by a conventional manufacturing process. Tires can be easily manufactured.

[0011]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The physical properties of the vulcanized rubber were measured according to the following methods. (1) Air Permeability The air permeability was measured by the method A (differential pressure method) of JIS K7126 “Testing method for gas permeability of plastics films and sheets”. The larger this value is, the better the air permeation resistance is. (2) Flexural Fatigue Resistance The number of times until the sample was broken under a condition of room temperature and a stroke of 40 mm was measured by a dematcher test method. The larger this value is, the better the bending fatigue resistance is. (3) Unvulcanized rubber modulus JIS K6 using JIS No. 5 type (ring-shaped test piece)
Only pulling speed 100 ± 5 mm according to 301-1995
/ Min and the tensile stress at 50% elongation (M ₅₀ ) was measured,
The index value is shown as an index value with Comparative Example 1 being 100. The greater this value, the greater the modulus.

Examples 1 to 12 and Comparative Examples 1 to 3 Compounds of the kind and amount shown in Table 1 and 5.0 parts by weight of spindle oil, 1.0 part by weight of zinc white, vulcanization accelerator NS
[Ouchi Shinko Chemical Industry Co., Ltd. trademark (Nt-butyl-
2-benzothiazylsulfenamide)] and 0.5 parts by weight of sulfur to obtain a rubber composition. This composition was vulcanized at 180 ° C. for 10 minutes.
About each obtained test piece rubber, air permeation resistance (60
° C), flex fatigue resistance and unvulcanized rubber modulus. Table 1 shows the results.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

[Table 3]

[Notes] 1) Syndiotactic 1,2-polybutadiene (trade name: JSR RB81 manufactured by JSR Corporation)
0)) 2) “Enjay Butyl HT10-66” (trade name, manufactured by Enj Chemical Co., Ltd.) 3) Halide of isobutylene-paramethylstyrene copolymer (trade name: EXPRO50, manufactured by Exxon Corporation) 4) FRR [Ube Industries, Ltd.] Trademark: “HE010
0 ", natural rubber: nylon short fiber = 2: 1 (weight ratio) 5) Nylon 6 short fiber [short fiber manufactured by Unitika Ltd. (average diameter: 3.3 dtex, average length: 1 mm)] 6) Crown clay [Shiraishi Calcium Corporation Trademark:
"Crown Clay-S") 7) Flat clay [J. M. Huber trademark: "P
OLYFIL DL ”(aspect ratio: 10)] (flat clay is kaolin clay having a large aspect ratio) 8) Si69; trademark, manufactured by Dexa Corporation 9) Dispersion improver [dimethylstearylamine (trademark, manufactured by Kao Corporation) : "DM80") 10) Types and amounts of softener, zinc white, vulcanization accelerator and sulfur as other compounding agents are described above.

In Examples 1 to 12 according to the present invention,
Compared with Comparative Example 1 which is a conventional rubber composition for an inner liner, air permeability resistance is greatly improved while at least bending fatigue resistance is maintained, and at the same time, an increase in unvulcanized rubber modulus is large.

[0018]

EFFECTS OF THE INVENTION The rubber composition for an inner liner of the present invention has significantly improved air permeability and processability as compared with a conventional butyl rubber compounded composition, and has an unvulcanized sheet during tire production. Cutability and puncture properties are also improved. Further, in a pneumatic tire using this rubber composition as the rubber for the inner liner, it is possible to reduce the weight of the tire by reducing the thickness of the rubber for the inner liner while maintaining the tire internal pressure.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C08L 9/00 C08L 9/00 77/00 77/00 91/00 91/00 F term (reference) 4J002 AC01X AC03X AC04X AC05X AC07X AC08X AE053 BB24W CL004 DA036 DJ006 DJ016 DJ036 DJ056 FA044 FD014 FD016 FD023 GN01

Claims (8)

[Claims] 1. A rubber composition for an inner liner of a pneumatic tire comprising a rubber component comprising 40 to 100% by weight of a halogenated butyl rubber and less than 60% by weight of a diene rubber and a layered or plate-like mineral. 2. The layered or plate mineral has an aspect ratio of 5
that's all. The rubber composition for an inner liner according to claim 1, wherein the rubber composition is a kaolinous clay of less than 30. 3. The rubber composition for an inner liner according to claim 1, wherein the layered or plate-like mineral is a hydrous composite of silica and alumina. Wherein with respect to the rubber component 100 parts by weight, more nitrogen adsorption specific area (N ₂ SA) is 26~170m ² /
The rubber composition for an inner liner according to claim 1, wherein 0 to 40 parts by weight of carbon black and 1 part by weight or more of a naphthenic or paraffinic oil are blended. 5. The compounding amount of the lamellar or plate-like mineral is 60 to 320 parts by weight based on 100 parts by weight of the rubber component, and the total amount of the mineral and the carbon black is 60 to 36 parts.
The rubber composition for an inner liner according to any one of claims 1 to 3, which is 0 parts by weight. 6. The rubber composition for an inner liner according to claim 1, further comprising 0.3 to 15 parts by weight of an organic short fiber based on 100 parts by weight of the rubber component. 7. The rubber composition for an inner liner according to claim 6, wherein the organic short fibers are polyamide fibers. 8. A pneumatic tire using the rubber composition according to claim 1 for an inner liner.