JP5079236B2 - Rubber composition for inner liner - Google Patents

Description

  The present invention relates to a rubber composition for an inner liner, and more particularly to a rubber composition for an inner liner mainly composed of resources other than petroleum.

  Many tires currently on the market are made up of raw materials that comprise more than half of the total weight of petroleum resources. For example, a general radial tire contains about 20% synthetic rubber, about 20% carbon black, and other aroma oils and synthetic fibers with respect to the total weight of the tire. Contains raw materials.

In recent years, environmental issues have become more important, regulations on CO ₂ emission control have been strengthened, and petroleum feedstock is limited and the supply volume has been decreasing year by year. For this reason, it is necessary to actively replace tires from petroleum resources to non-oil resources.

  However, among inner tire members, an inner liner that is particularly required to have a gas barrier property needs to contain a large amount of a synthetic rubber having a small air permeation amount such as a halogenated butyl rubber (see Patent Document 1), and is still a raw material petroleum. It was highly dependent on resources. In addition, in the rubber composition for the inner liner, when the rubber component was replaced from synthetic rubber with natural rubber which is a resource other than petroleum, sufficient gas barrier properties were not obtained.

JP 2004-339288 A

  An object of the present invention is to provide a rubber composition for an inner liner which is mainly composed of resources other than petroleum and has a high gas barrier property.

  The present invention relates to a rubber composition for an inner liner containing 2 to 20 parts by weight of paper fibers with respect to 100 parts by weight of a rubber component containing natural rubber and / or epoxidized natural rubber.

  According to the present invention, the rubber component for the inner liner to which a rubber component containing natural rubber and / or epoxidized natural rubber and a specific amount of paper fiber is added is mainly composed of resources other than petroleum, Gas barrier properties are high, and the occurrence of cracks can be suppressed.

  Hereinafter, the present invention will be described in detail.

  The rubber composition for an inner liner of the present invention contains a rubber component and paper fibers.

  The rubber component includes natural rubber (NR) and / or epoxidized natural rubber (ENR).

  As the NR, those generally used in the rubber industry such as TSR20 and RSS # 3 may be used. Further, as ENR, commercially available ENR may be used, or NR may be epoxidized. The method for epoxidizing NR is not particularly limited, and can be carried out using a method such as a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, or a peracid method. Examples of the peracid method include a method of reacting NR with an organic peracid such as peracetic acid or performic acid.

  The epoxidation rate of ENR is preferably 5 to 85 mol%. If the epoxidation rate is less than 5 mol%, the modification effect of the rubber composition tends to be small. Moreover, when the epoxidation rate exceeds 85 mol%, the polymer in the rubber composition tends to gel.

  The content of NR and / or ENR in the rubber component is preferably 70% by weight or more, and more preferably 80% by weight or more. When the content of NR and / or ENR is less than 70% by weight, the petroleum resource ratio tends to increase. Further, the content of NR and / or ENR in the rubber component is most preferably set to 100% by weight because it actively uses non-petroleum resources.

  The ratio of the ENR content to the total content of NR and ENR is preferably 50% by weight or more, and more preferably 70% by weight or more. When the ratio of the ENR content is less than 50% by weight, the effect of dispersing paper fibers in the rubber composition tends to be small. The ratio of the ENR content is most preferably 100% by weight because it improves the gas barrier properties and further improves the dispersion of the paper fibers in the rubber composition.

  In addition to NR and ENR, the rubber component includes styrene butadiene rubber (SBR), butadiene rubber (BR), styrene isoprene copolymer rubber, butyl rubber (in the range not impairing the effects of the present invention). IIR), halogenated butyl rubber (X-IIR), and a synthetic rubber such as a halide of a copolymer of isobutylene and p-methylstyrene may be blended.

  In the present invention, the paper fiber is a pulp obtained by a pulping method such as kraft pulp, semi-chemical pulp, mechanical pulp, non-wood pulp derived from kenaf, bagasse, bamboo, cotton, seaweed, used copy paper, Although it can be prepared using one or a mixture of two or more raw papers obtained from waste paper pulp obtained by deinking waste paper such as newspaper and old corrugated paper, for example, kraft paper pulverization Paper fibers having a relatively high physical strength, such as products, are preferably used. Kraft paper refers to all paper obtained by making kraft pulp, and includes unbleached kraft paper and bleached kraft paper. Kraft pulp, which is classified as a chemical pulp, is the mainstream and generally has a relatively long fiber length. Therefore, kraft paper is widely used as packaging paper for excellent strength. As the kraft pulp, either softwood kraft pulp or hardwood kraft pulp can be used, but softwood kraft pulp is preferable because of its relatively long fiber length.

  Kraft pulp is generally produced by the following method. First, the impurities of the chip as a raw material are removed, and the thickness and length are made uniform within a certain range. Next, the chips are steamed with chemicals such as caustic soda and sodium sulfide at a high temperature of, for example, about 150 to 160 ° C. to elute mainly lignin in the chips and pulp. After passing through a washing step for separating the eluted lignin and chemicals from the pulp, the pulp is further treated with, for example, an enzyme and an alkali to further elute residual lignin in the pulp. Finally, foreign matter is removed and washed to obtain unbleached kraft pulp. Unbleached kraft pulp can be made bleached kraft pulp through a bleaching process. By making unbleached kraft pulp, unbleached kraft paper and by making bleached kraft pulp can be produced.

  The average fiber length (L) of the paper fibers is preferably 10 μm or more, and more preferably 50 μm or more. When the L of the paper fiber is less than 10 μm, the reinforcing effect of the rubber composition tends not to be obtained. The L of the paper fiber is preferably 1000 μm or less. When the L of the paper fiber exceeds 1000 μm, there is a tendency that poor dispersion of the paper fiber in the rubber composition and non-uniform physical properties of the rubber composition cannot be sufficiently prevented.

  The average fiber diameter (D) of the paper fibers is preferably 10 μm or more. If the D of the paper fiber is less than 10 μm, the reinforcing effect on the rubber composition tends to be insufficient. Further, D of the paper fiber is preferably 100 μm or less, and more preferably 50 μm or less. When the D of the paper fiber exceeds 100 μm, there is a tendency that poor dispersion of the paper fiber in the rubber composition and non-uniform physical properties of the rubber composition are poor.

  The ratio of the average fiber length to the average fiber diameter (average aspect ratio, L / D) of the paper fibers is preferably 10 or more, and more preferably 20 or more. When the L / D of the paper fiber is less than 10, there is a tendency that the reinforcing effect on the rubber composition cannot be sufficiently obtained. The L / D of the paper fiber is preferably 2000 or less, and more preferably 1000 or less. When the L / D of the paper fiber exceeds 2000, there is a tendency that poor dispersion of the paper fiber in the rubber composition and non-uniform physical properties of the rubber composition become poor.

  The content of the paper fiber is 2 parts by weight or more, preferably 5 parts by weight or more with respect to 100 parts by weight of the rubber component. When the content of the paper fiber is less than 2 parts by weight, the gas barrier effect by blending the paper fiber is small. The paper fiber content is 20 parts by weight or less, preferably 15 parts by weight or less. If the content of paper fiber exceeds 20 parts by weight, cracks may occur in the inner liner.

  The rubber composition for an inner liner of the present invention preferably further contains a white filler such as silica, calcium carbonate, alumina, clay and talc. As the white filler, any of those conventionally used in rubber compositions can be arbitrarily selected and used. In particular, silica is mainly preferred because a reinforcing property close to that of carbon black can be obtained. Silica is not particularly limited, and silica prepared by a wet method or a dry method can be used.

  The content of the white filler is preferably 20 parts by weight or more and more preferably 30 parts by weight or more with respect to 100 parts by weight of the rubber component. When the content of the white filler is less than 20 parts by weight, there is a tendency that sufficient rubber strength cannot be obtained in the rubber composition. Further, the content of the white filler is preferably 120 parts by weight or less, more preferably 100 parts by weight or less with respect to 100 parts by weight of the rubber component. When the content of the white filler exceeds 120 parts by weight, the processability of the rubber composition tends to decrease.

  The rubber composition for an inner liner of the present invention preferably further contains a lamellar natural ore.

  The average particle diameter of the lamellar natural ore is preferably 2 to 30 μm. If the average particle size is less than 2 μm, the cost for pulverization during particle preparation tends to be high. On the other hand, when the average particle diameter exceeds 30 μm, it becomes a starting point of destruction of the rubber composition, and the bending fatigue resistance tends to decrease. In addition, an average particle diameter says the major axis of a thin plate-like natural ore.

  The aspect ratio (flatness) of the thin plate-like natural ore is preferably 3-30. When the aspect ratio is less than 3, there is a tendency that sufficient rubber hardness cannot be obtained for the rubber composition. On the other hand, when the aspect ratio exceeds 30, the dispersion in the rubber composition is lowered and the breaking strength tends to be lowered. Here, the aspect ratio refers to the ratio of the major axis to the thickness in the lamellar natural ore.

  The content of the lamellar natural ore is preferably 5 to 120 parts by weight with respect to 100 parts by weight of the rubber component. When the content of the lamellar natural ore is less than 5 parts by weight, the reinforcing effect by blending the lamellar natural ore tends to be small. On the other hand, when the content of the lamellar natural ore exceeds 120 parts by weight, it is difficult to disperse in the rubber composition and heat tends to be easily generated.

  The rubber composition for an inner liner of the present invention preferably further contains a softener. Examples of the softening agent include oils derived from petroleum resources such as aroma oils, and oils derived from non-petroleum resources such as vegetable oils and fats, and oils derived from non-petroleum resources are particularly preferable.

  Examples of oils derived from non-petroleum resources include animal oils and vegetable oils.

  Specific examples of animal fats include beef tallow.

  As vegetable oils, castor oil, cottonseed oil, linseed oil, rapeseed oil, palm oil, palm oil, peanut oil, rosin, pine oil, pineapple oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower Oil, palm oil, coconut oil, jojoba oil, macadamia nut oil, safflower oil, tung oil and the like.

  As oil derived from non-petroleum resources, vegetable oils and fats are particularly preferable because the supply is stable and the price is low.

  The iodine value of the softening agent (grams of iodine that can be added to 100 g of oil) is preferably 130 or less. When the iodine value exceeds 130, the low exothermic property tends to deteriorate.

The content of the softening agent is preferably blended so that the rubber hardness after vulcanization is 40 to 90. If the rubber hardness is less than 40, necessary synthesis cannot be obtained. Moreover, when it exceeds 90, there exists a tendency for workability to fall. In addition to the rubber component, white filler, lamellar natural ore and softener, the rubber composition for the inner liner of the present invention includes a silane coupling agent, a wax, an anti-aging agent commonly used in the tire industry, Stearic acid, zinc oxide, a vulcanizing agent, a vulcanization accelerator, and the like can be appropriately blended.

  The rubber composition for an inner liner of the present invention is used for manufacturing a tire and can be made into a tire by a usual method. That is, if necessary, the rubber composition for an inner liner of the present invention blended with the additive is extruded in accordance with the shape of the inner liner of the tire at an unvulcanized stage, and is usually used on a tire molding machine. An unvulcanized tire is formed by molding by the method. The unvulcanized tire is heated and pressurized in a vulcanizer to produce a tire.

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

  Next, the chemicals used in the examples and comparative examples will be described together.

(Raw materials made from non-oil resources)
Natural rubber (NR): RSS # 3
Epoxidized natural rubber (ENR): ENR-25 manufactured by Guthrie (epoxidation rate: 25%)
Silica: Ultrazil VN3 manufactured by Degussa
Coupling agent: Degussa Si-69
Sericite: KM-S manufactured by Nippon Foram Co., Ltd. (average particle size: 17 μm, average aspect ratio: 15)
Vegetable oil: refined palm oil J (S) manufactured by Nissin Oil Co., Ltd. (iodine value: 100)
Stearic acid: Zinc stearate made by Nippon Oil & Fats Co., Ltd .: Zinc oxide made by Mitsui Kinzoku Mining Co., Ltd. Sulfur: Powdered sulfur paper fiber made by Tsurumi Chemical Industry Co., Ltd .: Made by Oji Bag Co., Ltd. Neofiber (type: used newspaper, average fiber diameter: 30 μm, average fiber length: 1000 μm, average aspect ratio: 33)

(Raw materials consisting of petroleum resources)
Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
Vulcanization accelerator: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-2 and Comparative Examples 1-2
Chemicals other than sulfur and a vulcanization accelerator were blended according to the blending recipe in Table 1, and kneaded for 5 minutes at 150 ° C. using a Banbury mixer to obtain a kneaded product. In the obtained kneaded product, sulfur and a vulcanization accelerator are blended according to the blending formulation of Table 1, and kneaded at about 80 ° C. for 5 minutes using a biaxial open roll to obtain a sheet-like unvulcanized rubber composition. Produced. Then, the unvulcanized tire obtained by molding the sheet-like unvulcanized rubber composition into an inner liner shape on a tire molding machine and pasting it with other tire members is used for 35 minutes at 150 ° C. and 25 kgf. The test tires of Examples 1-2 and Comparative Examples 1-2 were produced by press vulcanization (tire size: 195 / 65R15). The following tests were conducted using the produced test tires.

(Machine durability test)
A test tire placed in an oven at a temperature of 80 ° C. for one week was run for 30,000 km under the conditions of an internal pressure of 200 kPa, a load of 340 kgf (333.261 N) and a speed of 80 km / h, and then the inner liner of the tire was damaged. The presence or absence, that is, the presence or absence of cracks was evaluated visually.

(Air permeability test)
A rubber test piece (90 mm in diameter and 1 mm in thickness) was produced by cutting the inner liner and the insulation portion of the test tire, and the air permeability coefficient (cc · cm / cm ² · in accordance with ASTM D-1434-75M). sec / cmHg) was calculated. Then, the air permeability coefficient of Comparative Example 1 was indicated as an index (gas barrier index) using the following calculation formula as a reference (100). A larger index indicates less air permeation and better gas barrier properties.
(Gas barrier index) = (Air permeability coefficient of Comparative Example 1) / (Each air permeability coefficient) × 100

  Table 1 shows the evaluation results of the machine durability test and the air permeation test.

Claims (2)

A rubber composition for an inner liner containing 2 to 20 parts by weight of paper fiber with respect to 100 parts by weight of a rubber component composed of only natural rubber and / or epoxidized natural rubber,
A rubber composition for an inner liner, wherein the content ratio of the epoxidized natural rubber in the rubber component is 50% by weight or more. A tire having an inner liner manufactured using the rubber composition for an inner liner according to claim 1 .