JP2002088191A - Rubber composition for inner liner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition for inner liners of tires especially suitable for heavy-duty vehicles used at very low temperatures such as aircraft, trucks and buses, excellent in uncured rubber modules, workability, etc., causing no cracks and having low air permeability even at very low temperature, capable of thin gauge design while keeping tire pressure retainability to afford lightweight tires. SOLUTION: This rubber composition for inner liners is characterized by comprising a rubber component composed of 0-40 pt(s).wt. of a butyl-based rubber containing >=40 wt.% of a halogenated butyl rubber and 60-100 pts.wt. of a diene-based rubber and a platy mineral; wherein preferably embodiments include the following: the aspect ratio for the platy mineral is >=5 but <30; the platy mineral is a composite of hydrous silica and alumina, or at least one kind selected from kaolin-based clays, this composition comprises 100 pts.wt. of the rubber component and 60-320 pts.wt. of the platy mineral.

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 which is particularly suitable for an inner liner in a tire for a heavy-duty vehicle that can be used under cryogenic conditions such as an aircraft, a truck and a bus.

[0002]

2. Description of the Related Art Tires for heavy-duty vehicles such as aircraft, trucks and buses are often used under cryogenic conditions. For example, in the case of aircraft tires, it may be necessary to fly in the atmosphere of at least -65 ° C, and in the case of tires for trucks, buses, etc., it may be necessary to park in extreme cold at -50 ° C. Conventionally, as a rubber composition for an inner liner in such a heavy-duty vehicle tire, a rubber composition containing butyl rubber or the like in a high ratio has been generally used. However, under the extremely low temperature condition, a rubber composition containing a high ratio of a polymer having a high glass transition temperature (Tg) such as butyl rubber has a problem that cracks occur. On the other hand, for the purpose of reducing the weight of the inner liner, for example, Japanese Patent Application Laid-Open No. 8-216286 discloses a thin resin film for an inner liner. However, in the case of these thin resin films for an inner liner, since a crystalline material is used as a matrix material, the embrittlement temperature is clearly higher than a rubber composition in which an inorganic filler is blended with butyl rubber. However, if the thickness is too small, there is a problem that the inner surface cord is exposed during tire production. Also, in the case of a rubber composition in which an inorganic filler is blended with butyl rubber, cracks may occur when used at an extremely low temperature of -40 ° C or lower.

[0003]

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 is particularly suitable for an inner liner in a heavy-duty vehicle tire that can be used under cryogenic conditions, such as aircraft, trucks, and buses, and has excellent workability and the like, and even under cryogenic conditions, cracks are generated. It is an object of the present invention to provide a rubber composition for an inner liner which is excellent in air permeation resistance, can be reduced in gauge while maintaining internal pressure retention, and can reduce the weight of tires.

[0004]

Means for solving the above problems are as follows.

<1> A rubber component containing 0 to 40 parts by weight of a butyl rubber containing 40% by weight or more of a halogenated butyl rubber and 60 to 100 parts by weight of a diene rubber;
And a rubber composition for an inner liner. <2> The rubber composition for an inner liner according to <1>, wherein the aspect ratio of the plate-like mineral is 5 or more and less than 30. <3> The rubber composition for an inner liner according to <1> or <2>, wherein the plate-like mineral is a composite of hydrous silica and alumina. <4> The rubber composition for an inner liner according to <1> or <2>, wherein the plate-like mineral is at least one selected from kaolin clay. <5> Any of <1> to <4>, wherein the nitrogen adsorption specific surface area (N ₂ SA) is 26 to 170 m ² / g and the carbon black is 0 to 40 parts by weight based on 100 parts by weight of the rubber component. A rubber composition for an inner liner as described above. <6> 100 parts by weight of the rubber component, 60 parts of plate-like mineral
The rubber composition for an inner liner according to <5>, which contains the rubber composition in an amount of about 320 parts by weight. <7> The rubber composition for an inner liner according to any one of <1> to <6>, wherein the rubber composition contains at least 1 part by weight of either a naphthenic oil or a paraffinic oil based on 100 parts by weight of a rubber component. . <8> The rubber composition for an inner liner according to any one of <1> to <7>, containing 0.3 to 15 parts by weight of an organic short fiber with respect to 100 parts by weight of a rubber component. <9> The above <8, wherein the organic short fiber is a polyamide short fiber.
> The rubber composition for an inner liner according to the above item.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber composition for an inner liner of the present invention contains a rubber component and a plate-like mineral, and further contains other components appropriately selected as necessary.

(Rubber component) The rubber component contains 0 to 40 parts by weight of a butyl rubber and 60 to 100 parts by weight of a diene rubber.

-Butyl rubber- As the butyl rubber, halogenated butyl rubber is used.
There is no particular limitation as long as the content is 0% by weight or more, and it can be appropriately selected from known ones according to the purpose. For example, a halide of isobutylene / paramethylstyrene copolymer is preferably exemplified. These may be used alone or in combination of two or more.

If the content of the halogenated butyl rubber in the butyl rubber is less than 40% by weight, the air permeability may not be sufficient. Incidentally, the content of the halogenated butyl rubber is more preferably 60 to 100% by weight, and more preferably 80 to 100% by weight, from the viewpoint of excellent air permeation resistance.
% By weight is particularly preferred.

[0010] The content of the butyl rubber in the rubber component is 0 parts by weight or more and less than 40 parts by weight,
If the amount is more than 40 parts by weight, low-temperature cracks are likely to occur and the low-temperature characteristics are inferior, which is not preferable. Therefore, the amount is more preferably 0 to 35 parts by weight.

-Diene rubber- The diene rubber is not particularly limited and can be appropriately selected from known rubbers according to the purpose. Examples thereof include natural rubber, epoxidized natural rubber, and styrene-butadiene. Polymers, styrene-isoprene copolymers, polyisoprene, polybutadiene, and the like are included. These may be used alone or in combination of two or more. Among these diene rubbers, natural rubber and / or polybutadiene rubber are preferred because of their excellent low-temperature properties.

The content of the diene rubber in the rubber component is from 60 to 100 parts by weight, and if it is less than 60 parts by weight, low-temperature cracks are likely to occur and the low-temperature characteristics are inferior. It is preferably from 100 to 100 parts by weight. On the other hand, when the content of the diene rubber is within the above-mentioned numerical range, there is no such problem, and it is advantageous in that the low-temperature characteristics are excellent.

(Plate-like mineral) The plate-like mineral is not particularly limited as long as its shape or structure is plate-like and flat, and can be appropriately selected depending on the purpose. Includes layered minerals. Specific examples of the plate-like mineral include mica, clay, silica, alumina, and a composite thereof. Of these, at least one selected from kaolin clay or a composite of hydrous silica and alumina is preferred. These may be used alone or in combination of two or more, and commercially available products can be suitably used.

The aspect ratio of the plate mineral is 5
It is preferably at least 30 and less than 30, more preferably 8 to 20. In addition, the aspect ratio means the ratio of the major axis to the thickness of the plate-like mineral. When the aspect ratio is less than 5, the rubber composition for an inner liner is inferior in air permeation resistance, the internal pressure retention is not sufficient, and a thin gauge cannot be obtained. In some cases, unvulcanized sheet breaks and perforations may occur, and cord exposure on the inner surface of the tire may occur. On the other hand, when the aspect ratio is within the above numerical range, the above-mentioned problem does not occur, and the rubber composition for an inner liner has excellent air permeability resistance, sufficient internal pressure retention, can be reduced in gauge, and can be processed easily. Excellent and advantageous in that unvulcanized sheets are not cut or perforated.

The content of the plate-like mineral in the rubber composition for the inner liner is as follows.
60 to 320 parts by weight, preferably 100 parts by weight,
~ 300 parts by weight is more preferred. When the content of the plate-like mineral is less than 60 parts by weight, the rubber composition for an inner liner is inferior in air permeation resistance, has insufficient internal pressure retention, and may not be able to be reduced in gauge, and may have a thickness of 320 parts by weight. If it exceeds the part, the workability is poor, the unvulcanized sheet may be cut or perforated, and the cord on the inner surface of the tire may be exposed. On the other hand, when the content of the plate-like mineral is within the above numerical range, the above-mentioned problem does not occur, and the rubber composition for the inner liner has excellent air permeability resistance, sufficient internal pressure retention, and can be thinned. It is advantageous in that it has excellent workability and does not cause unvulcanized sheet cuts or holes.

(Other Components) The other components are not particularly limited and may be appropriately selected depending on the intended purpose. Preferred examples thereof include carbon black, organic short fibers, and a dispersion improver. Further, various additives used in ordinary rubber compositions are preferably exemplified.

-Carbon Black- The carbon black is not particularly limited and may be appropriately selected depending on the intended purpose. Carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 26 to 170 m ² / g is used. preferably, more preferably those which are 100~170m ² / g, it is particularly preferable in 100-150 ² / g. The carbon black may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) is 2
When it is less than 6 m ² / g, may wear resistance of the rubber composition for an inner liner is not sufficient, 170m ² /
If the amount exceeds g, the dispersibility of carbon black in the rubber composition for an inner liner may decrease, and conversely, the abrasion resistance of the rubber composition for an inner liner may decrease.
Incidentally, the nitrogen adsorption specific surface area (N ₂ SA) is determined by ASTM.
It is defined in D3037-88 and means a nitrogen adsorption specific surface area per unit weight (m ² / g).

The content of the carbon black in the rubber composition for the inner liner is preferably 0 to 40 parts by weight, and more preferably 5 to 40 parts by weight, based on 100 parts by weight of the rubber component.
-35 parts by weight is more preferred. When the content of the carbon black exceeds 40 parts by weight, the rubber composition becomes too hard, which may cause scorching of the rubber or difficulty in forming a rubber sheet.

-Organic short fiber-The organic short fiber is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include polyamide fiber such as nylon 6 fiber and nylon 66 fiber, polyethylene fiber, and polyethylene fiber. Polyolefin fibers such as polypropylene fibers,
Preferable examples include polyester fibers. Among these, polyamide fibers are particularly preferable in terms of durability and the like. These may be used alone or in combination of two or more, and commercially available products can be suitably used.

The average fiber length of the organic short fibers is preferably, for example, about 0.1 to 5 mm. If the average fiber length is less than 0.1 mm, the effect of eliminating the exposure of the inner surface cord may not be sufficient, and if it exceeds 5 mm, the workability may be adversely affected.

The average fiber diameter of the organic short fibers is preferably, for example, about 1 to 100 μm. If the average fiber diameter is less than 1 μm, the effect of eliminating the inner cord exposure may not be sufficient, and if it exceeds 100 μm, the workability may be adversely affected.

The content of the organic short fiber in the rubber composition for the inner liner is as follows.
0.3 to 15 parts by weight is preferable with respect to 0 parts by weight. When the content of the organic short fiber is less than 0.3 parts by weight, the effect of eliminating the inner surface cord exposure may not be sufficient,
Exceeding the weight part may adversely affect the processability.

-Dispersion improver-The dispersion improver is not particularly limited as long as it can improve the dispersibility of the plate-like mineral in the rubber composition for the inner liner. It can be appropriately selected according to, for example, a silane coupling agent,
Methylstearylamine, triethanolamine, and the like. The dispersion improver can be added to the rubber composition for an inner liner as long as the effects of the present invention are not impaired.

-Various additives-The various additives can be appropriately selected and used within a range that does not impair the object of the present invention. Examples of the additives include inorganic fillers, softeners, and vulcanizing agents such as sulfur. Accelerators such as dibenzothiazyl disulfide, vulcanization aids, anti-aging agents such as N-cyclohexyl-2-benzothiazyl-sulfenamide, N-oxydiethylene-benzothiazyl-sulfenamide, zinc oxide, stearic acid , Ozone deterioration inhibitor, colorant, antistatic agent, lubricant, antioxidant, softener,
In addition to additives such as a coupling agent, a foaming agent and a foaming aid, various compounding agents usually used in the rubber industry are exemplified. These can use a commercial item suitably.

-Production of rubber composition for inner liner- The rubber composition for inner liner of the present invention comprises a mixture of the rubber component, the plate-like mineral, and the other components appropriately selected as necessary. It can be manufactured by kneading, heating, extruding, vulcanizing and the like.

The conditions for the kneading are not particularly limited, and various conditions such as the volume to be charged into the kneading apparatus, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of the kneading apparatus, etc. Can be appropriately selected according to the purpose. Examples of the kneading device include a Banbury mixer, an intermix, and a kneader that are usually used for kneading a rubber composition.

The heating conditions are not particularly limited, and various conditions such as a heating temperature, a heating time, and a heating device can be appropriately selected according to the purpose. Examples of the warming device include, for example, a roll machine usually used for warming a rubber composition.

The conditions for the extrusion are not particularly limited, and various conditions such as an extrusion time, an extrusion speed, an extrusion apparatus, and an extrusion temperature can be appropriately selected according to the purpose. As the extruder, for example, an extruder usually used for extruding a rubber composition can be used. The extrusion temperature can be appropriately determined.

At the time of the extrusion, a processability improver can be appropriately added to the rubber composition for the inner liner for the purpose of controlling the fluidity of the rubber composition for the inner liner. When the processability improver is blended with the rubber composition for the inner liner, it is advantageous in that the viscosity before vulcanization can be reduced, the fluidity thereof can be increased, and extrusion can be performed extremely well. .

Examples of the processability improver include aroma oils, naphthene oils, paraffin oils,
Examples include plasticizers such as ester-based oils, and liquid polymers such as liquid polyisoprene rubber and liquid polybutadiene rubber. These may be used singly, or 2
More than one species may be used in combination. Among these, at least one selected from naphthenic oils and paraffinic oils is preferred.

The addition amount of the processability improver in the rubber composition for the inner liner is as follows:
1 part by weight or more, preferably 3 to 20 parts by weight, per 100 parts by weight
Parts by weight are more preferred. The content of the processability improver,
If the amount is less than 1 part by weight, the effect of addition may not be obtained.

The vulcanizing apparatus, system, conditions and the like are not particularly limited and can be appropriately selected depending on the purpose. As an apparatus for performing the vulcanization, for example, a molding vulcanizer using a mold usually used for vulcanizing a rubber composition may be mentioned. The temperature of the vulcanization is usually about 100 to 190 ° C.

The rubber composition for an inner liner of the present invention can be particularly suitably used for an inner liner in a tire for a heavy-duty vehicle that can be used under cryogenic conditions such as an aircraft, a truck, and a bus.

[0035]

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

(Examples 1 to 8 and Comparative Examples 1 and 2) With respect to the rubber composition for an inner liner having the composition shown in Table 1, the air permeation resistance, low-temperature embrittlement resistance and unvulcanized modulus were determined as follows. evaluated. The results are shown in Table 1.

<Air Permeation Resistance> JIS K 7126
It was measured by the A method (differential pressure method) of "Testing method for gas permeability of plastic films and sheets". The rubber composition for the inner liner of Comparative Example 1 was expressed as an index with 100 as the index. That is, the larger the numerical value, the better the air permeation resistance.

<Low-Temperature Embrittlement> The brittle temperature was measured by a low-temperature impact embrittlement test according to JIS K6301. The rubber composition for the inner liner of Comparative Example 1 was expressed as an index with 100 as the index. That is, the larger the value, the better the low-temperature embrittlement.

<Unvulcanized rubber modulus> JIS K6
JIS No. 5 (ring-shaped test piece) in accordance with No. 301 and a tensile speed of only 100 ± 5 mm / min.
Tensile stress (M50) at 0% elongation was measured. Comparative Example 1
The rubber composition for the inner liner was expressed as an index with 100 as the index. That is, the larger the numerical value, the better the unvulcanized rubber modulus.

[0040]

[Table 1]

In Table 1, the numerical values in each column represent "parts by weight". “NR” represents natural rubber, and RS
S♯1. "Syndiotactic 1,2-polybutadiene" is RB100 manufactured by JSR Corporation. "Br-butyl rubber" refers to brominated butyl rubber. “Isobutylene / paramethylstyrene copolymer halide” is EXXPR050 manufactured by Exxon. “FRR” is a fiber reinforced rubber (Fiber Rei)
nforced Rubber), HE0100 (NR: nylon 6 monofilament) manufactured by Ube Industries, Ltd.
2: 1). “Nylon 6 single fiber” is a nylon 6 single fiber (average fiber diameter = 3.3 dtex, average fiber length = 1 mm) manufactured by Unitika. "GPF" stands for Ge
Neural Purpose Furnace (AST
MD-1765-94a).
"SAF" stands for Super Abrasion Fur
No. (as defined in ASTM D-1765-94a). "Crown Clay" is CrownClay-S manufactured by Nisseki Calcium. "Flat clay" is described in J.A. M. Hubly, POLYFIL D
L (aspect ratio = 10). "Dispersion improver"
It is a product of Kao Corporation, DM80 (dimethyl stearylamine).

From the results in Table 1, the following is clear. That is, as in Comparative Example 1, when the plate-like mineral is not contained and the butyl rubber is contained in an amount of 40 parts by weight or more, none of the air permeability resistance, low-temperature embrittlement, and unvulcanized rubber modulus are sufficient. On the other hand, as in Comparative Example 2, it does not contain a plate-like mineral, but contains 40 parts by weight or less of a butyl rubber.
Although low-temperature embrittlement and unvulcanized rubber modulus are better than Comparative Example 1, air permeability resistance is inferior. On the other hand, in the case of the embodiment of the present invention, air permeability resistance, low-temperature embrittlement and unvulcanized rubber modulus can be improved in a well-balanced manner.

[0043]

According to the present invention, the above-mentioned conventional problems can be solved, such as aircraft, trucks, buses, etc.
Particularly suitable for inner liners in heavy duty vehicle tires that can be used under cryogenic conditions, has excellent unvulcanized rubber modulus, workability, etc. It is possible to provide a rubber composition for an inner liner, which is excellent in hardness, can be reduced in gauge while maintaining internal pressure retention, and can reduce the weight of a tire.

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Claims (9)

[Claims] 1 to 40 parts by weight of a butyl rubber containing 40% by weight or more of a halogenated butyl rubber, and a diene rubber 60
A rubber composition for an inner liner, comprising: a rubber component containing 100 to 100 parts by weight; and a plate mineral. 2. The rubber composition for an inner liner according to claim 1, wherein the plate-like mineral has an aspect ratio of 5 or more and less than 30. 3. The rubber composition for an inner liner according to claim 1, wherein the plate-like mineral is a composite of hydrated silica and alumina. 4. The rubber composition for an inner liner according to claim 1, wherein the plate-like mineral is at least one selected from kaolin clay. 5. The rubber composition according to claim 1, wherein the rubber component has a nitrogen adsorption specific surface area (N ₂ SA) of 26 to 170 m ² / g and carbon black of 0 to 40 parts by weight based on 100 parts by weight of the rubber component. Rubber composition for an inner liner. 6. The rubber composition for an inner liner according to claim 5, comprising 60 to 320 parts by weight of a plate-like mineral based on 100 parts by weight of the rubber component. 7. The rubber composition for an inner liner according to any one of claims 1 to 6, wherein at least one part by weight of a naphthenic oil or a paraffinic oil is contained based on 100 parts by weight of the rubber component. 8. The rubber composition for an inner liner according to claim 1, comprising 0.3 to 15 parts by weight of organic short fibers based on 100 parts by weight of the rubber component. 9. The rubber composition for an inner liner according to claim 8, wherein the organic short fiber is a polyamide short fiber.