JP5358881B2 - Rubber composition for tire tread - Google Patents

Description

  The present invention relates to a rubber composition for a tire tread, and more particularly to a rubber composition for a tire tread that suppresses deterioration of physical properties due to traveling and suppresses changes in grip strength and controllability due to traveling.

  In recent years, in passenger car tires, consideration is given to safety as one of the required characteristics as well as high running performance. In general, tire tread rubber tends to deteriorate due to secular change, and grip strength and controllability tend to decrease due to changes in hardness and modulus. Improvement in this regard is desired.

In Patent Document 1 below, as a rubber composition for a tire tread having excellent on-ice performance and high wear resistance, a nitrogen adsorption ratio with respect to 100 parts by weight of a diene rubber containing 40 to 70 parts by weight of NR. A total amount of 15 to 40 parts by weight of carbon black having a surface area of 100 to 165 m ² / g and DBP oil absorption of 90 to 130 ml / 100 g and 20 to 60 parts by weight of precipitated silica having a BET specific surface area of 150 to 200 m ² / g. A rubber composition is proposed that is 40 to 90 parts by weight and is blended so that the ratio of carbon black / silica is 0.25 to 1.0. However, in the said rubber composition, there is no place indicated about the technique which suppresses the deterioration of the physical property by a secular change.

JP 2002-97304 A

  An object of the present invention is to provide a rubber composition for a tire tread that copes with a problem that the tire tread rubber deteriorates in physical properties due to traveling and suppresses a change in grip force and controllability due to aging.

  According to the present invention, a rubber composition for a tire tread comprising 30 parts by weight of a reinforcing filler containing 10 parts by weight or more of carbon black having an iodine adsorption amount of 100 mg / g or more per 100 parts by weight of a diene rubber. A rubber composition for tire treads, characterized in that 0.1 to 5.0 parts by weight of an alkali metal salt of an unsaturated fatty acid and 0.05 to 2.00 parts by weight of a thiuram vulcanization accelerator are blended. Is provided.

  Moreover, according to this invention, the rubber composition for tire treads which adds the said thiuram type vulcanization accelerator at the time of the mixing process of a masterbatch is provided.

  In the present invention, deterioration of physical properties (especially hardness and modulus) of the rubber composition for tire tread is caused by the combined use of an alkali metal salt of an unsaturated fatty acid and a thiuram vulcanization accelerator. It has been found that these deteriorations can be suppressed by using a rubber composition obtained by adding an agent during the mixing process of the masterbatch.

  Examples of the diene rubber used in the tire tread rubber composition of the present invention include natural rubber (NR), various butadiene rubbers (BR), various styrene-butadiene copolymer rubbers (SBR), and polyisoprene rubber (IR). ), Acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber, ethylene-propylene-diene copolymer rubber, styrene-isoprene copolymer rubber, styrene-isoprene-butadiene copolymer rubber, isoprene-butadiene copolymer For example, rubber. These diene rubbers may be used alone or as a blend rubber of two or more.

  As the reinforcing filler compounded and used in the tire tread rubber composition of the present invention, carbon black is used alone or in combination with silica and used in an amount of 30 to 100 parts by weight in total. . And as carbon black mix | blended and used for the rubber composition for tire treads of this invention, especially the iodine adsorption amount is 100 mg / g or more (measured according to JISK6217-1), and the fine of ASTM number N299 or less. Carbon black is used. Moreover, as the compounding amount of the carbon black, 10 to 100 parts by weight, preferably 20 to 100 parts by weight, of 30 to 100 parts by weight of the reinforcing filler amount with respect to 100 parts by weight of the diene rubber. Blended in quantity. When the blending amount of the carbon black is less than 10 parts by weight, the desired effect in the present invention is not exhibited. On the other hand, when it exceeds 100 parts by weight, the heat generation becomes high and the fuel efficiency becomes insufficient. Absent.

  Examples of the alkali metal salt of an unsaturated fatty acid used in the rubber composition for a tire tread of the present invention include acrylic acid, crotonic acid, isocrotonic acid, undecylenic acid, oleic acid, elaidic acid, cetreic acid, erucic acid, Examples include potassium salts and sodium salts of unsaturated fatty acids such as brassic acid, sorbic acid, linoleic acid, linolenic acid, and arachidonic acid. The amount of the alkali metal salt of the unsaturated fatty acid is 0.1 to 5.0 parts by weight, preferably 2.0 to 4.0 parts by weight, based on 100 parts by weight of the diene rubber. The If the blending amount is less than 0.1 parts by weight, the desired effect is not exhibited. Conversely, if the blending amount exceeds 5.0 parts by weight, the physical properties of the rubber composition are deteriorated (particularly, breaking strength), which is not preferable.

  Examples of the thiuram vulcanization accelerators that are used in combination with the alkali metal salt of the unsaturated fatty acid in the rubber composition for a tire tread of the present invention include, for example, tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide ( TMTD), tetraethyl thiuram disulfide (TETD), tetrabutyl thiuram disulfide (TBTD), pentamethylene thiuram tetrasulfide (PTT), dipentamethylene thiuram monosulfide (DPTM), dipentamethylene thiuram disulfide (DPTD), dipentamethylene thiuram Examples thereof include tetrasulfide (DPTT) and dipentamethylene thiuram hexasulfide (DPHT). The amount of the thiuram vulcanization accelerator is 0.05 to 2.00 parts by weight, preferably 0.3 to 0.6 parts by weight, based on 100 parts by weight of the diene rubber. . If the blending amount is less than 0.05 parts by weight, the desired effect is not exhibited. Conversely, if the blending amount exceeds 2.00 parts by weight, it is difficult to control the burning, which causes a problem in processing.

  In the rubber composition for a tire tread of the present invention, the above-mentioned thiuram vulcanization accelerator is separated from other vulcanization accelerators, and in the master batch mixing step in the rubber composition mixing step, the carbon black charging step When blended occasionally, a remarkable effect is exhibited, so that it is more desirable to use the rubber composition obtained in such an embodiment.

  The rubber composition for a tire tread according to the present invention is further blended for ordinary vulcanization or crosslinking agents, vulcanization or crosslinking accelerators, various oils, anti-aging agents, fillers, plasticizers, and other tire rubbers. Various compounding agents can be blended, and such compounding agents can be kneaded and vulcanized by a general method to obtain a rubber composition, which can be vulcanized or crosslinked. The compounding amounts of these compounding agents can be set to conventional general compounding amounts as long as the object of the present invention is not adversely affected.

  EXAMPLES Hereinafter, although this invention is further demonstrated by an Example and a comparative example, it cannot be overemphasized that the technical scope of this invention is not limited to these Examples.

Sample Preparation According to the formulation (parts by weight) shown in Table 1, in 1) embodiment (embodiments of Examples 1 and 2), rubber excluding sulfur and thiuram vulcanization accelerators and other vulcanization accelerators, carbon black In addition, in the embodiment of 2) (embodiments of Comparative Example 5, Examples 3 and 4), each compounding component such as rubber and carbon black excluding sulfur and other vulcanization accelerators is 1 A 7-liter closed Banbury mixer, mixed for 5 minutes, and the master batch which was discharged to the outside of the mixer and cooled to room temperature was charged again into the Banbury mixer, and the above excluded 1) or A rubber composition was obtained by blending and mixing the sulfur of the aspect 2) and a vulcanization accelerator. Next, this unvulcanized rubber composition was press vulcanized at 160 ° C. for 20 minutes in a predetermined mold to prepare a test sample (rubber sheet), which was subjected to the following hardness and modulus tests.

Test method 1) Rate of change in hardness: according to JIS K6253, the hardness Hs ₁ of each test sample at the time of production was measured, and each aging after storage in a sealed container maintained at 70 ° C. for 168 hours The hardness Hs _{2 of the} test sample was measured in the same manner. Next, (Hs ₁ −Hs ₂ / Hs ₁ ) was calculated from the hardnesses Hs ₁ and Hs _{2 of} each test sample obtained, and the hardness change rate of each test sample was determined. The index was expressed as an index with Comparative Example 1 as 100. The smaller the value, the less the change in hardness over time, and the better the grip strength over a long period of time.
2) Modulus change rate: According to JIS K6251, 300% modulus M ₁ 300 of each test sample at the time of production was measured and stored in a sealed container maintained at 70 ° C. for 168 hours. The 300% modulus M ₂ 300 of each aging test sample was measured similarly. Then calculated from M ₁ 300 and M ₂ 300 of each test sample obtained was _{(M 1 300-M 2 300} / M 1 300), it was determined modulus change rate of each test sample. The index was expressed as an index with Comparative Example 1 as 100. The smaller the value, the less the aging of the modulus and the better the controllability over a long period.

Examples 1-4 and Comparative Examples 1-5
The results are shown in Table 1 below.

  From the results of Table 1, in the rubber compositions of Examples 1 to 4 in which a carbon black compounded rubber composition was blended with a predetermined compounding amount of an alkali metal salt of an unsaturated fatty acid and a thiuram vulcanization accelerator, the secular change occurred. It can be seen that the decrease in grip force and controllability due to is suppressed satisfactorily. Furthermore, in Examples 3 and 4 in which the thiuram vulcanization accelerator was added during the masterbatch mixing process, it was shown that these suppressions were further improved.

  Therefore, the rubber composition of the present invention is extremely useful when used as a rubber composition for tire treads.

Claims (2)

Respect diene rubber 100 parts by weight, the iodine adsorption 100 mg / g or more carbon black blended 30 to 100 parts by weight reinforcing filler comprising 10 wt or more formed by a tire tread rubber composition, oleic acid A tire tread rubber composition comprising 0.1 to 5.0 parts by weight of an alkali metal salt and 0.05 to 2.00 parts by weight of a thiuram vulcanization accelerator.   The rubber composition for a tire tread according to claim 1, wherein the thiuram vulcanization accelerator is added during the masterbatch mixing step.