JP4567322B2 - Rubber composition for inner liner and pneumatic tire - Google Patents

Description

  The present invention relates to a rubber composition for an inner liner used for an inner liner of a pneumatic tire. More specifically, the present invention relates to a rubber composition having low air permeability, good tire internal pressure retention, excellent workability and adhesion, and non-halogenated. The present invention relates to a rubber composition for an inner liner and a pneumatic tire using the same.

  Conventionally, a tubeless type pneumatic tire has a thin layer of a non-breathable rubber composition on the inner surface of the tire in order to prevent the pressure air filled in the tire from permeating outside the tire and reducing the internal pressure. An inner liner is provided.

  In this inner liner rubber composition, butyl rubber having a low air permeability has been used, but in addition to the decrease in vulcanizability and processability, the adhesion to other tire members such as a carcass rubber layer is inferior. There's a problem. In order to improve this problem, a halogenated butyl rubber alone or a blend with a diene rubber is generally used as a rubber component of a rubber composition for an inner liner.

  However, although halogenated butyl rubber has improved the above problems of butyl rubber, it still has the disadvantages of insufficient stability during mixing, processability during extrusion and calendering, and adhesiveness when unvulcanized. In order to make up for this drawback, if the blending ratio of other diene rubbers such as natural rubber is increased, the processability and adhesiveness are improved, but an increase in air permeability is unavoidable.

  In order to eliminate the disadvantages of the above halogenated butyl rubber, the use of halogenated butyl rubber and polyisoprene rubber having a 3,4-bond amount of 40 to 80% as rubber components has low air permeability, processability and adhesiveness. An inner liner rubber composition that is excellent in the above is disclosed (Patent Document 1).

However, as the above-mentioned halogenated butyl rubber, chlorinated butyl rubber or brominated butyl rubber modified by addition reaction of chlorine or bromine with butyl rubber is generally used. There are problems such as generating harmful gases. With the recent increase in interest in environmental issues, there is a movement to suppress the use of halides that may be harmful to the environment. Non-halogenated materials that replace halogenated butyl rubber are also used in rubber compositions for inner liners. It has been demanded.
Japanese Patent Laid-Open No. 63-280750

  Therefore, the object of the present invention is to improve the workability of mixing, extrusion, calendering, vulcanization molding, etc., while maintaining low tire permeability with low air permeability and adhesion to other rubbers. Another object of the present invention is to provide a rubber composition for an inner liner which is a rubber composition suitable for an inner liner excellent in properties and which can realize non-halogenation, and a pneumatic tire using the same.

The rubber composition for an inner liner of the present invention, 100 parts by weight of the rubber component, a polyisoprene rubber 70 to 100 parts by weight containing 30% to 70% of 3,4-bond component as diene rubber other than the polyisoprene rubber It consists of 0 to 30 parts by weight of natural rubber .

  According to the rubber composition for an inner liner of the present invention, the vinyl component of the polyisoprene rubber containing a 3,4-bond component exhibits air impermeability and maintains a good tire internal pressure. It is possible to improve processability such as sulfur molding and adhesion with other diene rubbers, and to realize non-halogenation without using halogenated butyl rubber.

  If the 3,4-bond component of the polyisoprene rubber is less than 30%, the vinyl content of the polyisoprene rubber is insufficient and the air permeability of the rubber composition is increased. Sulfur formability deteriorates and processability also decreases.

  Further, when the blending amount in the rubber component is reduced to less than 70 parts by weight and the amount of other diene rubbers is increased, the mixing property, processability and adhesiveness are further improved. If it exceeds 1, the air permeability is remarkably increased, making it difficult to apply as an inner liner.

  And the pneumatic tire of the present invention is characterized in that the rubber composition for an inner liner is applied to an inner liner.

  The pneumatic tire of the present invention can maintain the tire production process satisfactorily by improving the mixing property and workability, and can improve the tire durability with excellent adhesion to the carcass layer. A pneumatic tire using a non-halogenated rubber composition that is maintained at the same level as the halogenated butyl rubber can be obtained.

  According to the present invention, air that maintains low air permeability, improves processability such as mixing, extrusion, calendering, and vulcanization molding, and realizes non-halogenation with excellent adhesion to other diene rubbers. It is possible to obtain a rubber composition for an inner liner suitable for an inner liner of a contained tire, and to provide a pneumatic tire that is excellent in production processability and internal pressure retention using the same and is compatible with environmental problems. .

  As the polyisoprene rubber containing 3,4-bond component used in the rubber composition of the present invention (hereinafter referred to as 3,4-polyisoprene rubber), 30-70% of 3,4-bond is added to the isoprene polymer. The other microstructures are composed mainly of 1,4-cis-bonded polyisoprene. The 3,4-bond component is preferably 40% or more from the viewpoint of reducing the air permeability.

  Such a 3,4-polyisoprene rubber contains a 3,4-bond component more than a normal polyisoprene rubber (the amount of 3,4-bond in the molecular chain is less than 10%), thereby making it a conventional halogenated product. It exhibits air impermeability at the same level as butyl rubber, and is a type of diene rubber, which improves the processability of rubber composition, extrudability, vulcanization, etc. compared to halogenated butyl rubber, and other diene rubbers. The compatibility with rubber can be increased to improve adhesion.

  The 3,4-polyisoprene rubber is considered to reduce the air permeability by reducing the double bond in the main chain to suppress the molecular motion of the main chain and introducing a large group into the side chain. If the 3,4-bond component is less than 30%, the air permeability becomes high, and if it exceeds 70%, the crosslinking rate is slow and co-crosslinking is difficult, and the viscosity during unvulcanization increases and the workability decreases. It shows a tendency and is not preferred.

As the diene rubber other than the 3,4-polyisoprene rubber , natural rubber (NR 2 ) is used from the viewpoint of processability and adhesiveness .

  In the present invention, when 3,4-polyisoprene rubber and diene rubber are blended to form a rubber composition for an inner liner, this 3,4-polyisoprene rubber is 70 to 100 weight in the rubber component. It mix | blends so that part may be contained. It is preferable to use 100% of this 3,4-polyisoprene rubber as a rubber component in terms of maintaining the lowest air permeability, but from the viewpoint of further improving the processability of the rubber composition and the adhesion to other rubbers. Other diene rubbers may be used in combination, and the content of other diene rubbers in that case is about 30 parts by weight. This is because if the other diene rubber exceeds 30 parts by weight, the air permeability of the rubber composition is remarkably increased, making it difficult to apply as an inner liner.

  The rubber composition for an inner liner of the present invention includes a vulcanizing agent such as carbon black, process oil, zinc white, sulfur, etc., a vulcanization accelerator (thiazole, Sulfenamides and the like), and chemicals such as anti-aging agents, waxes, stearic acid, calcium carbonate and the like are appropriately blended and used within a normal range.

  Here, as carbon black, since it is used for an inner liner, so-called soft carbon having good workability such as mixing and extrudability is preferable, and GPF, FEF, SRF grade carbon black is exemplified, and the blending amount is rubber. It is used in the range of about 50 to 100 parts by weight with respect to 100 parts by weight of the component.

  The rubber composition for an inner liner of the present invention is kneaded in accordance with a conventional method using a rubber kneader such as a normal Banbury mixer or kneader to obtain a rubber composition, and the sheet is obtained by a normal rubber extruder or a calender device. 1 is applied to and used for an inner liner 2 provided on the inner surface of a tire inside a carcass layer 3 of a pneumatic tire 1 as shown in FIG.

  The rubber composition for an inner liner of the present invention is not only for pneumatic radial tires for passenger cars shown in FIG. 1, but also for automobiles such as large tires for light trucks, trucks and buses, for industrial vehicles and construction vehicles. It can be used for an inner liner of a pneumatic tire for various uses such as agriculture, and can also be used as a rubber composition for a tube of a tube type pneumatic tire.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by this.

  The rubber compositions for the inner liners of the examples and comparative examples in which the rubber components and compounding chemicals listed in Table 1 were blended according to the blending amounts (parts by weight) listed in the table were kneaded using a normal 20 liter Banbury mixer. Each rubber composition was obtained.

  About each obtained rubber composition, air permeability, adhesiveness, and processability were evaluated by the following method. The results are shown in Table 1.

In addition, each rubber component and compounding chemicals are as follows.
[Rubber component]
Brominated butyl rubber (Br-IIR): Nippon Butyl Co., Ltd., Bromobutyl 2255
・ Natural rubber (NR): RSS # 3
3,4-polyisoprene rubber A (3,4-IR (A)): Goodyear Chemical Co., Ltd., TRAXSYN, 3,4-bond component = 54%
3,4-polyisoprene rubber B (3,4-IR (B)): 3,4-bond component = 22%
3,4-polyisoprene rubber C (3,4-IR (B)): 3,4-bond component = 76%
The 3,4-bond amount is measured using NMR.

[Combination chemicals]
-Carbon black GPF: Dia Black G manufactured by Mitsubishi Chemical Corporation
Aroma oil: JOMO Process X-140, manufactured by Japan Energy Co., Ltd.
・ Zinc flower: Mitsui Kinzoku Mining Co., Ltd., Zinc flower No. 3 ・ Sulfur (5% oil-treated powder sulfur): Hosoi Chemical Co., Ltd., powder sulfur 150 mesh ・ Vulcanization accelerator DM: Ouchi Shinsei Chemical Industrial Co., Ltd., Noxeller DM-P
・ Vulcanization accelerator CZ: Ouchi Shinsei Chemical Co., Ltd., Noxeller CZ-G

[Air permeability]
Using the rubber compositions of the examples and comparative examples, a rubber sheet having a thickness of 1 mm was prepared by press vulcanization at 160 ° C. for 20 minutes under a pressure of 50 kgf / cm ² , and the differential pressure method described in JIS K7126 ( The air permeability ratio was measured according to Method A). The comparative example 1 is indicated by an index indicating 100, and the smaller the value, the lower the air permeability and the better.

[Adhesion (adhesion to carcass rubber)]
The rubber compositions of each Example and Comparative Example and the rubber composition for NR / SBR-based carcass, each having a thickness of 3 mm, are bonded together when unvulcanized, and press vulcanized at 160 ° C. for 20 minutes under a pressure of 50 kgf / cm ^2. A sample for a peel test having a width of 10 mm was prepared, a peel test was performed at a peel rate of 50 mm / min, and the average peel force was obtained. Comparative example 1 is indicated by an index value of 100, and the larger the value, the higher the adhesive strength with carcass rubber and the better the adhesiveness.

[Machinability]
Based on the Mooney viscosity test method described in JIS K6300, the Mooney viscosity (ML1 + 4, 100 ° C.) of the rubber compositions of Examples and Comparative Examples was determined and evaluated as an index of workability. The results are shown on the basis of Comparative Example 1 as ◯: Good workability, Δ: Slightly inferior in workability, ×: Inferior in workability.

  As shown in Table 1, the rubber composition for an inner liner of the example blended with 3,4-polyisoprene rubber according to the present invention has an air permeability substantially equal to that of a rubber composition using a conventional halogenated butyl rubber. Level, improving adhesion to carcass rubber, maintaining Mooney viscosity, improving processability, and enabling non-halogenation of inner liners that do not use halogenated butyl rubber. .

  The rubber composition for an inner liner of the present invention can be used for an inner liner of a pneumatic tire used for various applications including automobiles such as passenger cars, light trucks, trucks and buses. Of course, it can also be used as a rubber composition for tubes.

It is a half sectional view of a pneumatic tire.

Explanation of symbols

1 …… Pneumatic tire 2 …… Inner liner 3 …… Carcass layer

Claims (2)

A rubber composition for an inner liner, characterized in that 100 parts by weight of a rubber component comprises 70 to 100 parts by weight of a polyisoprene rubber containing 30 to 70% of a 3,4-bond component and 0 to 30 parts by weight of natural rubber . A pneumatic tire characterized by applying the rubber composition for an inner liner to an inner liner.

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