JP2011153220A - Rubber composition for inner liner, and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for inner liner, satisfying both car-driving stability and blow resistance, and to provide pneumatic tires using the composition. <P>SOLUTION: The rubber composition for inner liner includes: a rubber component including at least one rubber selected from the group consisting of non-modified natural rubber, isoprene rubber, butadiene rubber and styrene-butadiene rubber; and zinc oxide with an average primary particle size of 200 nm or less. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a rubber composition for an inner liner and a pneumatic tire using the same.

Conventionally, in a pneumatic tire, particularly a tubeless tire, an inner liner rubber made of rubber having a low air permeability is formed on the tire lumen surface for the purpose of maintaining the tire internal pressure. As the inner liner rubber, butyl rubber, halogenated butyl rubber or the like having excellent air permeation resistance is generally used.

The inner liner portion of the pneumatic tire is likely to generate heat when the vehicle is running, and under high temperature conditions, the rigidity may decrease and the steering stability may deteriorate. Therefore, from the viewpoint of safety, there is a demand for an inner liner that can improve the handling stability, and this requirement is particularly strong in racing tires.

Steering stability can be improved by making the inner liner highly rigid. However, when traveling for a long distance, heat is accumulated, and blow may occur or breakage may occur on the tire surface (tread portion) and / or the inside (inner liner portion). This is particularly noticeable in competition tires that generate a large amount of heat.

Patent Document 1 discloses that excellent air permeation resistance and flex crack growth resistance can be obtained by a rubber composition for an inner liner containing epoxidized natural rubber, silica, and fine particle zinc oxide. . However, there has been no room for improvement since the compatibility between steering stability and blow resistance has not been studied.

JP 2008-297462 A

An object of the present invention is to solve the above-mentioned problems and to provide a rubber composition for an inner liner that can achieve both steering stability and blow resistance, and a pneumatic tire using the same.

A rubber for an inner liner comprising a rubber component containing at least one rubber selected from the group consisting of non-modified natural rubber, isoprene rubber, butadiene rubber, and styrene butadiene rubber, and zinc oxide having an average primary particle size of 200 nm or less. Relates to the composition.

The rubber composition preferably contains carbon black.

It is preferable that the content of the zinc oxide is 0.1 to 20 parts by mass and the content of the carbon black is 10 to 100 parts by mass with respect to 100 parts by mass of the rubber component.

The present invention also relates to a pneumatic tire having an inner liner produced using the rubber composition. The pneumatic tire is preferably a competition tire.

According to the present invention, a rubber component containing at least one rubber selected from the group consisting of non-modified natural rubber, isoprene rubber, butadiene rubber, and styrene butadiene rubber, and zinc oxide having a specific average primary particle size Since it is a rubber composition for an inner liner, it is possible to provide both a steering stability and a blow resistance and to provide a pneumatic tire excellent in a handling stability and a blow resistance.
Blowing refers to breakage in which rubber boils, becomes a blister, and rubber scatters. Such damage can be suppressed as the blow resistance is higher.

The rubber composition for an inner liner of the present invention includes a rubber component containing at least one rubber selected from the group consisting of non-modified natural rubber, isoprene rubber, butadiene rubber, and styrene butadiene rubber, and a specific average primary particle diameter. Zinc oxide.

In the present invention, at least one rubber selected from the group consisting of non-modified natural rubber (non-modified NR), isoprene rubber (IR), butadiene rubber (BR), and styrene butadiene rubber (SBR) is used as the rubber component. Including. Of these, SBR is preferable because of its high rigidity.

In this specification, non-modified natural rubber (non-modified NR) refers to natural rubber that has not been chemically modified. As the unmodified NR, for example, SIR20, RSS # 3, TSR20, etc., which are common in the tire industry can be used. Non-modified NR also includes deproteinized natural rubber (DPNR) and high-purity natural rubber (HPNR). The non-modified NR does not include chemically modified natural rubber such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), or grafted natural rubber. Moreover, as IR, what is common in the tire industry can be used. These may be used alone or in combination of two or more. By including non-modified NR and / or IR, low heat generation is achieved and fuel efficiency is improved.

When the rubber composition of the present invention contains non-modified NR and / or IR, the total content of non-modified NR and IR in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more. It is. If it is less than 10% by mass, the heat generation becomes high and the fuel economy may be deteriorated. Moreover, although the said total content may be 100 mass%, Preferably it is 90 mass% or less, More preferably, it is 50 mass% or less. If it exceeds 90% by mass, sufficient rigidity may not be obtained.

The BR is not particularly limited. For example, BR1220 manufactured by Nippon Zeon Co., Ltd., BR130B manufactured by Ube Industries, Ltd., BR150B having a high cis content such as BR150B, VCR412 manufactured by Ube Industries, Ltd. BR containing syndiotactic polybutadiene crystals can be used.

When the rubber composition of the present invention contains BR, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more. If it is less than 5% by mass, the heat generation becomes high and the fuel economy may be deteriorated. The BR content may be 100% by mass, but is preferably 90% by mass or less, more preferably 80% by mass or less. If it exceeds 90% by mass, sufficient rigidity may not be obtained.

The SBR is not particularly limited, and for example, emulsion polymerization styrene butadiene rubber (E-SBR), solution polymerization styrene butadiene rubber (S-SBR) and the like can be used.
By including SBR, the rigidity can be improved.

The styrene content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more. If it is less than 5% by mass, sufficient rigidity may not be obtained. The styrene content is preferably 90% by mass or less, more preferably 50% by mass or less. If it exceeds 90% by mass, the heat generation becomes high and the fuel efficiency may be deteriorated. Moreover, there exists a possibility that a low temperature characteristic may deteriorate (embrittlement).

When the rubber composition of the present invention contains SBR, the content of SBR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more. If it is less than 5% by mass, sufficient rigidity may not be obtained. The SBR content may be 100% by mass, preferably 90% by mass or less, more preferably 60% by mass or less, and still more preferably 50% by mass or less. If it exceeds 90% by mass, the heat generation becomes high and the fuel efficiency may be deteriorated. Moreover, there exists a possibility that a low temperature characteristic may deteriorate (embrittlement).

The total content of non-modified NR, IR, BR and SBR in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 50% by mass or more, and particularly preferably 80% by mass. % Or more, most preferably 100% by mass. When the total content is less than 20% by mass, it is difficult to obtain sufficient rigidity, and there is a risk that steering stability and blow resistance may not be compatible.

In addition to non-modified NR, IR, BR, and SBR, rubber components that can be used in the present invention include dienes such as acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and halogenated butyl rubber (X-IIR). System rubbers. These diene rubbers may be used alone or in combination of two or more.

In the present invention, butyl rubbers such as butyl rubber (IIR) and halogenated butyl rubber (X-IIR) may be used, but butyl rubber is substantially contained because high rigidity may not be obtained. Preferably not.

The total content of butyl rubber in 100% by mass of the rubber component is preferably 0.05% by mass or less, more preferably 0.01% by mass or less, still more preferably 0.001% by mass or less, and most preferably 0% by mass. % (Does not contain).

In the present invention, zinc oxide having a specific average primary particle size is used. By blending zinc oxide with a specific average primary particle size, dispersibility of zinc oxide is improved and crosslinking efficiency is improved, so it is estimated that blow resistance can be improved while maintaining rigidity and steering stability. The

The average primary particle diameter of zinc oxide is 200 nm or less, preferably 150 nm or less, more preferably 140 nm or less, still more preferably 130 nm or less, particularly preferably 100 nm or less, and most preferably 80 nm or less. When it exceeds 200 nm, there is a possibility that sufficient improvement effect cannot be obtained in the dispersibility of zinc oxide and the physical properties of rubber as compared with normal zinc oxide. The average primary particle diameter of zinc oxide is preferably 20 nm or more, more preferably 30 nm or more. If it is less than 20 nm, the average particle size of zinc oxide becomes smaller than the primary particle size of carbon black, and the dispersibility of zinc oxide cannot be sufficiently improved, and sufficient wear resistance and blow resistance may not be obtained. There is.
In addition, the average primary particle diameter of zinc oxide represents the average particle diameter (average primary particle diameter) converted from the specific surface area measured by the BET method by nitrogen adsorption.

The content of the zinc oxide is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, and further preferably 0.3 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 0.1 parts by mass, the crosslinking efficiency is not sufficiently improved, and sufficient wear resistance and blow resistance tend not to be obtained. The zinc oxide content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 12 parts by mass or less, particularly preferably 5 parts by mass or less, and most preferably 3 parts by mass or less. Most preferably, it is 2 parts by mass or less. When the amount exceeds 20 parts by mass, zinc oxide is not sufficiently dispersed and becomes a core of blow, which may deteriorate blow resistance.

In this invention, it is preferable that carbon black is included. Thereby, rigidity can be improved. Examples of carbon black that can be used include GPF, FEF, HAF, ISAF, and SAF, but are not particularly limited. Carbon black may be used alone or in combination of two or more.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 50 m ² / g or more, more preferably 70 m ² / g or more, and still more preferably 100 m ² / g or more. If it is less than 50 m ² / g, sufficient reinforcing properties cannot be obtained, and there is a possibility that the rigidity cannot be sufficiently improved. Further, the nitrogen adsorption specific surface area of the carbon black is preferably 200 meters ² / g or less, more preferably 190 m ² / g. When it exceeds 200 m ² / g, the heat generation is too high, and the blow resistance may be deteriorated.
In addition, the nitrogen adsorption specific surface area of carbon black is calculated | required by A method of JISK6217.

Carbon black has a dibutyl phthalate (DBP) oil absorption of preferably 5 ml / 100 g or more, more preferably 10 ml / 100 g or more, and even more preferably 80 ml / 100 g or more. If it is less than 5 ml / 100 g, the wear resistance may be deteriorated. The DBP oil absorption amount of carbon black is preferably 300 ml / 100 g or less, more preferably 290 ml / 100 g or less, still more preferably 150 ml / 100 g or less. If it exceeds 300 ml / 100 g, the heat generation is too high and blow resistance may be deteriorated.
In addition, the DBP oil absorption amount of carbon black is calculated | required by the measuring method of JISK6217-4.

The content of carbon black is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 40 parts by mass or more, and particularly preferably 50 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 10 parts by mass, sufficient rigidity cannot be obtained, and blow resistance may not be sufficiently improved. The carbon black content is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and still more preferably 80 parts by mass or less. If it exceeds 100 parts by mass, it may become too hard and the grip performance may be reduced.

In the present invention, silica may be blended. By blending silica, low heat build-up (low fuel consumption) and rigidity can be improved in a balanced manner.
The silica is not particularly limited, and examples thereof include dry process silica (anhydrous silicic acid), wet process silica (hydrous silicic acid), and the like, but wet process silica is preferable because of its large number of silanol groups.

The nitrogen adsorption specific surface area _(N 2 SA) of silica is preferably not less than ^{40 m} 2 / g, more preferably at least ^{75m 2 / g, 100m 2 /} g or more, and particularly preferably equal to or greater than 150m ² / g. If it is less than 40 m < ² > / g, there exists a possibility that abrasion resistance may deteriorate. Further, N ₂ SA of silica is preferably 220 m ² / g or less, and more preferably 200 m ² / g or less. If it exceeds 220 m ² / g, dispersibility may be deteriorated and mechanical fatigue may be increased.
The nitrogen adsorption specific surface area of silica is a value measured by the BET method according to ASTM D3037-81.

The content of silica is preferably 50 parts by mass or more, more preferably 60 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 50 parts by mass, sufficient rigidity may not be obtained. The content of the silica is preferably 150 parts by mass or less, more preferably 130 parts by mass or less. If it exceeds 150 parts by mass, the dispersion of silica becomes non-uniform, and the fracture characteristics may deteriorate.

When blending silica, it is preferable to blend a silane coupling agent with silica. Thereby, low exothermic property (low fuel consumption) and wear resistance can be improved in a balanced manner.
The silane coupling agent used in the present invention is not particularly limited. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-triethoxysilylethyl) tetrasulfide, bis (4-triethoxy) Silylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) ) Trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis ( 2-G Methoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide , Sulfide systems such as 3-triethoxysilylpropyl methacrylate monosulfide, mercapto systems such as 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane, vinyl systems such as vinyltriethoxysilane and vinyltrimethoxysilane, Amino compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane And the like, nitros such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane, and chloros such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. . These may be used alone or in combination of two or more. Of these, bis (3-triethoxysilylpropyl) tetrasulfide is preferable.

In the rubber composition of the present invention, in addition to the above components, compounding agents generally used in the production of rubber compositions, for example, reinforcing fillers such as clay, stearic acid, various anti-aging agents, oils, waxes, Vulcanizing agents, vulcanization accelerators and the like can be appropriately blended.

The rubber composition of the present invention may contain oil. By blending oil, processability can be improved. As the oil, for example, process oil, vegetable oil, or a mixture thereof can be used.
As the process oil, for example, a paraffin process oil, an aroma process oil, a naphthenic process oil, or the like can be used. Specific examples of the paraffinic process oil include PW-32, PW-90, PW-150, and PS-32 manufactured by Idemitsu Kosan Co., Ltd. In addition, as an aroma-based process oil, specifically, AC-12, AC-460, AH-16, AH-24, AH-58 made by Idemitsu Kosan Co., Ltd., Process X-260 made by Japan Energy, etc. Can be mentioned. As vegetable oils and fats, castor oil, cottonseed oil, sesame oil, rapeseed oil, soybean oil, palm oil, palm oil, peanut water, rosin, pine oil, pineapple, tall oil, corn oil, rice bran oil, beet flower oil, sesame oil, Examples include olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. Of these, an aroma-based process oil is preferably used.

When the rubber composition contains oil, the oil content is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 5 mass parts, workability will deteriorate. The oil content is preferably 200 parts by mass or less, more preferably 180 parts by mass or less, still more preferably 50 parts by mass or less, and particularly preferably 20 parts by mass or less. When it exceeds 200 parts by mass, blow resistance may be deteriorated.

Examples of the vulcanization accelerator include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamic acid, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate vulcanization accelerator. Agents. Of these, sulfenamide vulcanization accelerators are preferred.

Examples of the sulfenamide vulcanization accelerator include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N And '-dicyclohexyl-2-benzothiazolylsulfenamide (DZ). Of these, TBBS is preferable.

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing.

The pneumatic tire of the present invention is produced by a usual method using the rubber composition.
That is, by extruding the rubber composition blended with the above components in accordance with the shape of the inner liner at an unvulcanized stage, and molding it on a tire molding machine together with other tire members, Form an unvulcanized tire. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

The pneumatic tire of the present invention is suitably used as a tire for passenger cars, a tire for trucks and buses, a tire for motorcycles, a tire for competition, and the like, particularly as a tire for competition (particularly, a competition tire for long-distance running). Used for. The pneumatic tire obtained by the present invention can achieve both steering stability and blow resistance.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: RSS # 3 (non-denatured NR)
BR: BR150B manufactured by Ube Industries, Ltd. (cis content: 98% by mass)
SBR: Toughden 4350 manufactured by Asahi Kasei Co., Ltd. (styrene content: 39% by mass, 50 parts by mass of oil with respect to 100 parts by mass of rubber solid, Table 1 shows solids)
Carbon black: N550 (N ₂ SA: 143 m ² / g, DBP oil absorption: 113 ml / 100 g) manufactured by Cabot Japan
Silica: Ultrasil VN3 manufactured by Degussa (N ₂ SA: 175 m ² / g)
Silane coupling agent: Si69 (bis (3-triethoxysilylpropyl) tetrasulfide) manufactured by Degussa
Oil: Process P-200 manufactured by Japan Energy Co., Ltd.
Wax: Sannoc Wax anti-aging agent manufactured by Ouchi Shinsei Chemical Co., Ltd. Phenylenediamine)
Stearic acid: Zinc stearate oxide manufactured by NOF Corporation (1): Zinc Hana No. 1 manufactured by Mitsui Kinzoku Kogyo Co., Ltd. (average primary particle size: 400 nm)
Zinc oxide (2): Zincok Super F-2 (average primary particle size: 65 nm) manufactured by Hakusui Tech Co., Ltd.
Zinc oxide (3): Zinccock Super F-1 (average primary particle size: 100 nm) manufactured by Hakusui Tech Co., Ltd.
Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd .: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-11 and Comparative Examples 1-9
According to the blending contents shown in Table 1, materials other than sulfur and vulcanization accelerator were kneaded for 3 minutes at 150 ° C. using a BP Banbury mixer to obtain a kneaded product. Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 5 minutes under a condition of 80 ° C. using a biaxial open roll to obtain an unvulcanized rubber composition.
The obtained unvulcanized rubber composition was press vulcanized at 170 ° C. for 12 minutes to obtain a vulcanized rubber sheet.
Further, the obtained unvulcanized rubber composition is molded into an inner liner shape, bonded to another tire member, molded into a tire, and vulcanized at 150 ° C. and 25 kgf for 35 minutes for a test cart tire (tire) Size: 11 × 7.10-5) was produced.

The following evaluation was performed using the obtained vulcanized rubber sheet and test cart tire. Each test result is shown in Table 1.

(Tensile test)
In accordance with JIS K 6251 “Vulcanized Rubber and Thermoplastic Rubber-Determination of Tensile Properties”, using the test piece (dumbbell No. 3) obtained by cutting the vulcanized rubber sheet, the tensile strength at 100% elongation Stress M100 (MPa) was measured. The measurement conditions were a test temperature of 25 ° C. and a tensile speed of 500 mm / min. The results were expressed as an index using the following formula, with the result of Comparative Example 1 being 100. The larger the index, the better the rigidity.
Stiffness index: (M100 of each formulation) / (M100 of Comparative Example 1) × 100

(Maneuvering stability)
The test cart tire was attached to the test cart, and the test course of 1 km 2 km was run 8 times. The steering stability of the tire of Comparative Example 1 was 3 points, and the test driver made a sensory evaluation with 5 points. The larger the value, the better the steering stability.

(Blow resistance)
The test cart tire was mounted on the test cart, and the test course of 1 lap 2 km was run for 38 laps. After running, the tire was disassembled, the degree of blow in the tread cross section was observed, and Comparative Example 1 was rated 3 points, and was evaluated on a 5-point scale. Larger values indicate better blow resistance.

Examples comprising a rubber component comprising at least one rubber selected from the group consisting of unmodified NR, IR, BR, and SBR, and zinc oxide having a specific average primary particle size are provided with steering stability and resistance to blow. I was able to balance sex. On the other hand, the comparative example in which zinc oxide having a specific average primary particle size was not blended was inferior in blow resistance to the examples, and it was impossible to achieve both steering stability and blow resistance. Further, when corresponding examples and comparative examples (for example, Example 1 and Comparative Example 2) are compared, the amount of zinc oxide having a specific average primary particle size is smaller than that of ordinary zinc oxide (zinc oxide (1)). Despite not blended, the blow resistance could be improved, and further, the rigidity and steering stability were not lowered.

Claims (5)

A rubber for an inner liner comprising a rubber component containing at least one rubber selected from the group consisting of non-modified natural rubber, isoprene rubber, butadiene rubber, and styrene butadiene rubber, and zinc oxide having an average primary particle size of 200 nm or less. Composition. The rubber composition for an inner liner according to claim 1, comprising carbon black. The rubber composition for an inner liner according to claim 2, wherein the content of the zinc oxide is 0.1 to 20 parts by mass and the content of the carbon black is 10 to 100 parts by mass with respect to 100 parts by mass of the rubber component. . The pneumatic tire which has an inner liner produced using the rubber composition in any one of Claims 1-3. The pneumatic tire according to claim 4, which is a racing tire.