JP2008260808A - Rubber composition and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silica-compounded rubber composition improved in silica dispersibility. <P>SOLUTION: The rubber composition is such that 100 pts.wt. of a rubber component is compounded with 20-120 pts.wt. of silica. In this composition, a ≥5C monohydric alcohol, preferably a 5-15C monohydric alcohol is also compounded. Preferably, the monohydric alcohol is compounded at 0.5-8 pts.wt. based on 100 pts.wt. of the rubber component. This rubber composition is preferably to be used as a rubber composition for a tire, and by compounding the above alcohol, tire rolling resistance of the tire can be reduced, which results in the high fuel economy of the tire. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition, and more particularly to a rubber composition suitable as a rubber composition for a tire, and a pneumatic tire using the same.

  In recent developments of pneumatic tires, silica is often blended with a rubber composition in order to reduce fuel consumption. That is, silica suppresses heat generation of the rubber composition, thereby reducing rolling resistance and contributing to improvement in fuel efficiency.

  However, since silica is hydrophilic, it is difficult to disperse in an oleophilic rubber polymer and it is easy to form an aggregate. Therefore, in order to make the most of the characteristics of silica, it is important to ensure dispersibility.

Therefore, in order to improve the dispersibility of silica, various silane coupling agents are used as an agent for linking hydrophilic silica and a lipophilic rubber polymer (for example, see Patent Documents 1 and 2 below).
JP 2005-281621 A JP 2005-226001 A

  Although the dispersibility of silica can be improved by blending a silane coupling agent as described above, further improvement is required. Then, an object of this invention is to provide the rubber composition which can further improve the dispersibility of a silica.

  The present inventor has intensively studied in view of the above problems, and has found that the dispersibility of silica is improved by adding a higher alcohol, and has completed the present invention.

  That is, the rubber composition according to the present invention contains 20 to 120 parts by weight of silica with respect to 100 parts by weight of the rubber component, and contains a monohydric alcohol having 5 or more carbon atoms.

  The rubber composition is preferably used as a tire rubber composition, that is, the present invention also provides a pneumatic tire using the rubber composition.

  Silanol groups on the surface of silica have a strong polarity, and silica is a factor for forming aggregates. On the other hand, by adding a higher alcohol having 5 or more carbon atoms, the silanol group of silica and the hydroxyl group of alcohol are physically bonded by hydrogen bonding, and an organic layer is formed on the silica surface by the hydrocarbon moiety of the alcohol. The Thereby, the cohesiveness of the silica is reduced, and the affinity with the rubber component by the organic layer is improved, so that the dispersibility of the silica in the rubber component can be improved. Therefore, for example, when used for tire rubber, it is possible to reduce rolling resistance and reduce fuel consumption.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  In the rubber composition according to the present invention, the rubber component is not particularly limited as long as it is a lipophilic (hydrophobic) polymer in which the dispersibility of hydrophilic silica is likely to be a problem. With such a lipophilic rubber component, the above-described effects can be achieved by improving the affinity with an organic layer formed of a higher alcohol. Specific examples of rubber components include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), styrene-isoprene copolymer rubber, and butadiene-isoprene copolymer. Examples include polymer rubber, styrene-isoprene-butadiene copolymer rubber, diene rubber such as nitrile rubber (NBR), butyl rubber (IIR), and ethylene-propylene copolymer rubber (EPR, EPDM). Each may be used alone or in combination of two or more.

  When used as a rubber composition for a tire, the rubber component is preferably a diene rubber such as natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene copolymer rubber, and more preferably styrene-butadiene copolymer. It is to use united rubber. More specifically, a rubber component composed of a styrene-butadiene copolymer rubber alone or a blend rubber of 50% by weight or more of styrene-butadiene copolymer rubber and 50% by weight or less of another diene rubber is preferable.

Although it does not specifically limit as a silica mix | blended with the said rubber composition, It is preferable to use the wet silica which has a hydrous silicic acid as a main component. The specific surface area of the silica (BET method measured according to ISO 5794/1) is not particularly limited, but is preferably 50 to 300 m ² / g.

  Silica is preferably blended in an amount of 20 to 120 parts by weight with respect to 100 parts by weight of the rubber component, more preferably 30 to 100 parts by weight, and even more preferably 50 to 100 parts by weight. If the blending amount of silica is too small, the wear resistance is insufficient, and conversely if too large, workability is impaired.

  The rubber composition of the present invention contains a monohydric alcohol having 5 or more carbon atoms. Conventionally, it has not been known to blend such a higher alcohol into a rubber composition, and the above-described unique excellent effect of improving the dispersibility of silica has been found for the first time by the present invention. If the alcohol has 4 or less carbon atoms, the effect of improving the dispersibility of silica cannot be obtained. In addition, in the case of a dihydric or higher polyhydric alcohol, it is difficult to form a hydrophobic organic layer on the silica surface, and the effect of improving the affinity with the rubber component by the organic layer cannot be obtained.

  The alcohol preferably has 5 to 15 carbon atoms. Even if alcohol having 16 or more carbon atoms is used, the effect of improving dispersibility can be obtained, but if the number of carbon atoms is too large, it is originally solid, which causes blooming after vulcanization. The alcohol moiety of the alcohol is an oleophilic moiety that contributes to improving the affinity with the oleophilic rubber component, which may or may not have an unsaturated bond, and has a branched chain. Or a straight chain. Further, it may be a primary alcohol, a secondary alcohol, or a tertiary alcohol. Acyclic saturated alcohol is preferable, and linear primary saturated alcohol is particularly preferable.

  Specific examples of the alcohol include 1-pentanol, 2-pentanol, 3-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, 1-heptanol, 1-octanol, 2-octanol, 2 Preferred examples include -ethyl-1-hexanol, 1-nonanol, 1-decanol, 2-decanol, 1-undecanol, 1-dodecanol, 1-tetradecanol, 3-hexen-1-ol and the like.

  The alcohol is preferably blended in an amount of 0.5 to 8 parts by weight, more preferably 1 to 7 parts by weight with respect to 100 parts by weight of the rubber component. When the amount of the alcohol is too large, other characteristics such as grip properties (wet property) and strength on a wet road surface tend to be impaired.

  In the rubber composition according to the present invention, various silane coupling agents can be blended in order to promote the bonding between silica and the rubber component. The silane coupling agent is not particularly limited, and examples thereof include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) tetrasulfide, 3 -Mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-nitropropyltrimethoxysilane, γ-aminopropyltriethoxysilane and the like. The silane coupling agent is usually blended in an amount of 5 to 20 parts by weight, more preferably 6 to 10 parts by weight with respect to 100 parts by weight of silica.

  In addition to the above components, the rubber composition according to the present invention includes other fillers such as carbon black, anti-aging agents, zinc oxide, stearic acid, softeners, vulcanizing agents such as sulfur, and vulcanization acceleration. Various additives that are usually blended in tires and other general rubber compositions such as vulcanizing agents and vulcanization retarders can be blended.

  The rubber composition according to the present invention can be obtained, for example, by kneading using a kneader such as a Banbury mixer, a kneader, or a roller, and various rubber products can be produced by vulcanization molding according to a conventional method. it can. The rubber composition of the present invention is preferably used for forming a rubber member (tread, sidewall, etc.) in a pneumatic tire, and particularly preferably used for a tread of a pneumatic tire.

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

(First embodiment)
Using a Banbury mixer, according to the formulation shown in Table 1 below, rubber compositions for tire treads of Examples and Comparative Examples were prepared. Each component in Table 1 is as follows.

SBR: styrene-butadiene copolymer rubber “Tuf3330” manufactured by Asahi Kasei Co., Ltd. (oil-extended polymer containing 37.5 parts by weight of oil with respect to 100 parts by weight of styrene content = 31 wt% rubber polymer, in the table) The parts in parentheses are rubber parts by weight)
・ Silica: “Nip Seal AQ” manufactured by Tosoh Silica, BET specific surface area = 215 m ² / g),
Silane coupling agent: “Si69” manufactured by Degussa.

  In each rubber composition, 3 parts by weight of zinc white ("Zinc Flower No. 1" manufactured by Mitsui Mining & Smelting Co., Ltd.) and stearic acid ("Lunac S-" manufactured by Kao Corporation) per 100 parts by weight of the rubber component as a common compound 20 ") 1 part by weight, anti-aging agent 6C (" Nocrack 6C "manufactured by Ouchi Shinsei Chemical Co., Ltd.) 2 parts by weight, wax (" Sunnock "manufactured by Ouchi Shinsei Chemical Co., Ltd.) 1 part by weight, sulfur (Hosoi 2 parts by weight of “Sulfur powder for rubber 150 mesh” manufactured by Chemical Industry Co., Ltd., 1.5 parts by weight of vulcanization accelerator CZ (“Noxeller CZ” manufactured by Ouchi Shinsei Chemical Co., Ltd.), and vulcanization accelerator DPG 1 part by weight (“Noxeller D” manufactured by Ouchi Shinsei Chemical Co., Ltd.) was blended.

  About each obtained rubber composition, the viscosity and the modulus were measured. Also, each rubber composition was applied to a cap tread of a tire having a tread having a cap / base structure, and a 205 / 65R15 94H pneumatic radial tire was manufactured in accordance with a conventional method, and rolling resistance and wet performance were evaluated. . Each evaluation method is as follows. All evaluations were expressed as an index with the value of Comparative Example 1 as 100.

Viscosity: Mooney viscosity was measured in accordance with JIS K6300 (L-shaped rotor), preheating for 1 minute, measurement for 4 minutes, and temperature of 100 ° C. The smaller the index, the lower the viscosity and the better the workability and dispersibility.

Modulus (M300): A test piece vulcanized at 160 ° C. for 15 minutes was measured with “Autograph SES1000” manufactured by Shimadzu Corporation in accordance with JIS K-6251.

・ Rolling resistance: When using a rim of 15 x 6.5 JJ and wearing tires, with a pneumatic pressure of 230 kPa and a load of 450 kgf, when running at 80 km / h at 23 ° C on a uniaxial drum tester for measuring rolling resistance The rolling resistance was measured. The smaller the index, the smaller the rolling resistance and thus the better the fuel efficiency.

-Wet performance: 2000cc domestic FF vehicle with 4 tires, running on asphalt road surface with water depth of 2-3mm, operating ABS at 90km / h, decelerating to 20km / h The braking distance was measured. A larger index indicates better wet performance.

  As shown in Table 1, in Examples 1 to 10 to which higher alcohol was added, the viscosity of the rubber composition was low, the processability was excellent, and the rolling resistance was improved. In particular, in Examples 1 to 6 and 8 to 10, workability and rolling resistance were improved without substantially impairing physical properties such as strength and wet properties. In Example 6 using stearyl alcohol, bloom occurred on the rubber surface after vulcanization molding. Further, in Example 7 in which the blending amount of the higher alcohol was too large, although the processability and rolling resistance were excellent, the physical properties and wet properties were lowered.

  On the other hand, in Comparative Example 2 in which isobutanol, which is a lower alcohol, was blended, no effect of improving rolling resistance was observed.

(Second embodiment)
As an example of increasing the amount of silica, rubber compositions for tire treads of Examples and Comparative Examples were prepared according to the formulation shown in Table 2 below. Each component and common component in Table 2 are the same as those in the first embodiment.

About each obtained rubber composition, the viscosity, the modulus, the rolling resistance, and the wet performance were evaluated in the same manner as in the first example. Evaluation was expressed as an index with the value of Comparative Example 3 as 100.

(Third embodiment)
As examples in which the diene rubber was changed, rubber compositions for tire treads of Examples and Comparative Examples were prepared according to the formulation shown in Table 3 below. “BR” in Table 3 is a high cis-butadiene rubber “BR01” manufactured by JSR Corporation, and “oil” is “JOMO Process X-140” manufactured by Japan Energy Corporation. The other components and common components in Table 3 are the same as in the first embodiment.

About each obtained rubber composition, the viscosity, the modulus, the rolling resistance, and the wet performance were evaluated in the same manner as in the first example. The evaluation was expressed as an index with the value of Comparative Example 4 as 100.

  According to the present invention, by adding a higher alcohol in the silica formulation, the cohesive force between the silicas can be reduced and the affinity with the rubber component can be improved, so that the dispersibility of the silica can be improved. Therefore, the characteristics of silica can be effectively exhibited. Therefore, for example, by using it for various pneumatic tires including passenger car radial tires, it is possible to reduce rolling resistance and improve fuel efficiency.

Claims (4)

  A rubber composition containing 20 to 120 parts by weight of silica with respect to 100 parts by weight of a rubber component and containing a monohydric alcohol having 5 or more carbon atoms.   The rubber composition according to claim 1, comprising 0.5 to 8 parts by weight of the monohydric alcohol with respect to 100 parts by weight of the rubber component.   The rubber composition according to claim 1 or 2, wherein the monohydric alcohol is a saturated alcohol having 5 to 15 carbon atoms.   A pneumatic tire using the rubber composition according to claim 1.