JP2007161792A - Pneumatic tire having rubber composition and tire tread using the same - Google Patents

Abstract

[PROBLEMS] To provide a rubber composition having improved rigidity and grip performance without deteriorating characteristics such as degree of crosslinking, wear resistance and hardness, and a pneumatic tire using the rubber composition for a tire tread.
SOLUTION: To 100 parts by weight of a diene rubber, 0.2 to 10 parts by weight of a carboxylic acid metal salt, 0.2 to 5 parts by weight of a basic vulcanization accelerator, and a thiazole vulcanization accelerator. A pneumatic tire having a rubber composition containing 0.2 to 5 parts by weight and a tire tread using the rubber composition.
[Selection figure] None

Description

  The present invention relates to a pneumatic tire having a rubber composition and a tire tread.

  The tread portion of the pneumatic tire generates heat as the vehicle travels, and there is a problem that grip performance deteriorates due to high temperature conditions. Therefore, in order to improve the grip performance during high speed running on a circuit or the like, it is necessary to increase the hysteresis loss at a high temperature (for example, 50 ° C.).

  Conventionally, in order to improve grip performance, as a method of increasing hysteresis loss, a method of increasing the content of carbon black or oil, a method of blending a resin, a method of blending imidazoles, and a metal carboxylate are used. Methods of blending are known. However, when the content of carbon black or oil is increased, the strength of the rubber is lowered. When a resin is blended, the hardness of the rubber increases, so that only a small amount can be blended, and a dramatic improvement in grip performance cannot be expected. In addition, when imidazoles are blended, the modulus at the time of high elongation such as M300 is remarkably lowered, and on the contrary, steering stability and wear resistance are lowered. In addition, when a carboxylic acid metal salt is added, the vulcanization speed is delayed, the degree of crosslinking decreases due to insufficient vulcanization, and the modulus at high elongation also decreases, resulting in abrasion resistance due to continuous running in circuit running etc. It will cause deterioration of wear.

  Patent Document 1 includes a predetermined amount of silica, a predetermined carboxylic acid metal salt, and N, N′-bis (2-methyl-2-nitropropyl) -1,6hexanediamine, thereby reducing wear resistance. A rubber composition with improved grip performance is disclosed. However, the improvement effect of the grip performance is not sufficient, and other characteristics are not improved in a well-balanced manner.

JP 2003-213045 A

  An object of the present invention is to provide a rubber composition having improved rigidity and grip performance without reducing properties such as the degree of crosslinking, wear resistance, and hardness, and a pneumatic tire using the rubber composition for a tire tread. To do.

  The present invention relates to 0.2 to 10 parts by weight of a carboxylic acid metal salt, 0.2 to 5 parts by weight of a basic vulcanization accelerator, and a thiazole vulcanization accelerator with respect to 100 parts by weight of a diene rubber. The present invention relates to a rubber composition containing 0.2 to 5 parts by weight.

  The present invention also relates to a pneumatic tire having a tire tread using the rubber composition.

  According to the present invention, the diene rubber contains a predetermined amount of each of a carboxylic acid metal salt, a basic vulcanization accelerator, and a thiazole vulcanization accelerator, so that characteristics such as a degree of crosslinking, wear resistance, and hardness can be obtained. Without lowering, it is possible to provide a rubber composition having improved rigidity and markedly improved grip performance, and a pneumatic tire using the rubber composition for a tire tread.

  The rubber composition of the present invention contains a diene rubber, a carboxylic acid metal salt and a vulcanization accelerator.

  Diene rubbers include natural rubber (NR), styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), butyl rubber (IIR), acrylonitrile butadiene rubber (NBR), ethylene propylene rubber (EPDM), Examples include chloroprene rubber (CR), and these diene rubbers may be used alone or in combination of two or more. Among these, at least one diene rubber selected from the group consisting of SBR, NR, and BR is preferable because it has sufficient strength and exhibits excellent wear resistance, and SBR is more preferable.

  SBR includes emulsion polymerization SBR (E-SBR) and solution polymerization SBR (S-SBR), and S-SBR is preferable because grip performance in continuous running can be maintained at a relatively high level.

  Examples of carboxylic acid metal salts include, for example, acetic acid metal salts, benzoic acid metal salts, acrylic acid metal salts, methacrylic acid metal salts, propionic acid metal salts, butyric acid metal salts, propylacetic acid metal salts, caproic acid metal salts, and enanthic acid metals. Examples thereof include monocarboxylic acid metal salts such as metal salts, caprylic acid metal salts, pelargonic acid metal salts and capric acid metal salts, and polycarboxylic acid metal salts such as oxalic acid metal salts, fumaric acid metal salts and maleic acid metal salts. Among these, a monocarboxylic acid metal salt is preferable, an acetic acid metal salt and a benzoic acid metal salt are more preferable, and an acetic acid metal salt or a benzoic acid metal salt is more preferable.

  Examples of the carboxylic acid metal salt satisfying the above conditions include alkali metal salts such as sodium acetate and potassium benzoate, and alkaline earth metal salts such as magnesium acetate, magnesium benzoate and calcium acetate. Alkaline earth metal salts are preferable, and magnesium acetate or magnesium benzoate is more preferable because it is high and easily ionically bonds with carboxylic acid.

  As the carboxylic acid metal salt, the above compounds may be used alone or in combination of two or more. However, when two or more carboxylic acid metal salts having an ionic bond are used in combination, the effect of the combination is obtained. Since it is difficult to obtain and the rubber strength tends to decrease, it is preferably used alone.

  The content of the carboxylic acid metal salt is 0.2 parts by weight or more, preferably 1 part by weight or more with respect to 100 parts by weight of the diene rubber. When the content of the carboxylic acid metal salt is less than 0.2 parts by weight, it is difficult to obtain the expected improvement in grip performance. The content of the carboxylic acid metal salt is 10 parts by weight or less, preferably 6 parts by weight or less. When the content of the carboxylic acid metal salt exceeds 10 parts by weight, the rubber strength is significantly reduced.

  By blending a carboxylic acid metal salt containing an ionic bond, it is possible to produce a hysteresis loss (increase tan δ) at a high temperature or a large strain, so that grip performance can be improved. Furthermore, when a carboxylic acid metal salt is blended, there is an advantage that the glass transition temperature (Tg) changes little and it is difficult to cause brittle fracture.

  The vulcanization accelerator includes a basic vulcanization accelerator and a thiazole vulcanization accelerator.

  A basic vulcanization accelerator is a vulcanization accelerator that exhibits basicity. For example, a guanidine vulcanization accelerator, an aldehyde / ammonia vulcanization accelerator, an aldehyde / amine vulcanization accelerator, or a thiourea vulcanization accelerator. And sulfur accelerators. Of these, guanidine vulcanization accelerators are preferred because they have a relatively moderate vulcanization acceleration effect.

  Examples of the guanidine vulcanization accelerator include 1,3-diphenyl guanidine, 1,3-diortolyl guanidine, triphenyl guanidine, 1-ortho-tolyl biguanide, and diphenyl guanidine phthalate. Of these, diphenylguanidine is preferable because it is cheaper.

  The content of the basic vulcanization accelerator is 0.2 parts by weight or more, preferably 0.5 parts by weight or more with respect to 100 parts by weight of the diene rubber. When the content of the basic vulcanization accelerator is less than 0.2 parts by weight, the effect of promoting the vulcanization rate is insufficient. The content of the basic vulcanization accelerator is 5 parts by weight or less, preferably 3 parts by weight or less. When the content of the basic vulcanization accelerator exceeds 5 parts by weight, it exceeds the solubility limit in the rubber and blooms (deposits) on the rubber surface.

  The thiazole vulcanization accelerator is one kind of vulcanization accelerator exhibiting acidity. For example, 2-mercaptobenzothiazole and its derivatives, di-2-benzothiazyl disulfide, 2- (2,4-dinitrophenyl) Thio) benzothiazole, N-cyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide, 2- (N, N-diethylthiocarbamoylthio) benzothiazole, 2- (4′-morpholinodithio) benzothiazole and the like. Of these, N-cyclohexyl-2-benzothiazolylsulfenamide and Nt-butyl-2-benzothiazole are preferable because N-cyclohexyl-2-benzothiazolylsulfenamide and N-cyclohexyl are preferred because of their relatively slow scorch and rapid vulcanization. 2-Benzothiazolylsulfenamide is more preferred.

  The content of the thiazole vulcanization accelerator is 0.2 parts by weight or more, preferably 0.5 parts by weight or more with respect to 100 parts by weight of the diene rubber. When the content of the thiazole vulcanization accelerator is less than 0.2 parts by weight, the vulcanization reaction cannot be performed. Further, the content of the thiazole vulcanization accelerator is 5 parts by weight or less, preferably 3 parts by weight or less. If the content of the thiazole vulcanization accelerator exceeds 5 parts by weight, a scorch problem occurs.

  In the present invention, the basic vulcanization acceleration of the rubber acidified with the carboxylic acid metal salt is achieved by blending the diene rubber with the carboxylic acid metal salt, the basic vulcanization accelerator and the thiazole vulcanization accelerator. The effect of maintaining the strength of the rubber is obtained because it can be neutralized by the agent and desired vulcanization can be achieved by the thiazole vulcanization accelerator.

  The rubber composition of the present invention preferably further contains a resin.

  The softening point of the resin is preferably 60 ° C. or higher, and more preferably 120 ° C. or higher. When the softening point of the resin is less than 60 ° C., the expected grip performance tends not to be obtained. The softening point of the resin is preferably 180 ° C. or lower, and more preferably 160 ° C. or lower. When the softening point of the resin exceeds 180 ° C., the rubber tends to be harder than necessary.

  When the resin is blended, the resin content is preferably 0.1 parts by weight or more, more preferably 2 parts by weight or more, and further preferably 3 parts by weight or more. If the resin content is less than 0.1 parts by weight, the expected improvement in grip performance tends to be difficult to obtain. The resin content is preferably 50 parts by weight or less, and more preferably 20 parts by weight or less. When the resin content exceeds 50 parts by weight, the hardness of the rubber tends to be harder than necessary.

  In the rubber composition of the present invention, in addition to the diene rubber, carboxylic acid metal salt, vulcanization accelerator, and, if necessary, a reinforcing filler such as carbon black, aroma oil, wax, etc. Additives generally used in the rubber industry, such as a vulcanizing agent such as an agent, stearic acid, zinc oxide and sulfur, can be appropriately blended.

  The rubber composition of the present invention is preferably a tire rubber composition, and since it has excellent wear resistance and grip performance, it is more preferable to use a tire tread rubber composition among tire members. .

  The pneumatic tire of the present invention is produced by a usual method using the rubber composition as a tire tread. That is, the rubber composition is extruded into the shape of a tread portion of a tire at an unvulcanized stage, and bonded together by a normal method on a tire molding machine to form an unvulcanized tire. The unvulcanized tire can be heated and pressurized in a vulcanizer to obtain the pneumatic tire of the present invention.

  The pneumatic tire of the present invention is used for, for example, passenger car tires, heavy duty tires such as buses and trucks, competition tires, etc. Among them, since high grip performance can be obtained, it is used for competition tires. Is preferred.

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

Solution polymerized styrene butadiene rubber (S-SBR): Toughden 4350 manufactured by Asahi Kasei Corporation (containing 50 parts by weight of oil with respect to 100 parts by weight of rubber solid)
Carbon black: Diamond Black A (N110) manufactured by Mitsubishi Chemical Corporation
Aroma oil: Process X-260 manufactured by Japan Energy Co., Ltd.
Wax: Ozoace 0355 manufactured by Nippon Seiki Co., Ltd.
Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
Stearic acid: Nippon Oil & Fats Co., Ltd. Zinc flower: Mitsui Metal Mining Co., Ltd. carboxylic acid metal salt A: Kishida Chemical Co., Ltd. magnesium acetate carboxylic acid metal salt B: Fushimi Pharmaceutical Co., Ltd. (benzoic acid) sodium)
Resin A: Softening point 151 ° C.
Resin B: Softening point 140 ° C
Imidazoles: NOCRACK MB (2-mercaptobenzimidazole) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Sulfur: Basic vulcanization accelerator (Accelerator D) manufactured by Tsurumi Chemical Industry Co., Ltd .: Noxeller D (1,3-diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Thiazole-based vulcanization accelerator (accelerator CZ): Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-6 and Comparative Examples 1-2
According to the formulation of Tables 1 and 2, using a Banbury mixer, chemicals other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 160 ° C. to obtain a kneaded product. Sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 3 minutes at 80 ° C. using an open roll to obtain an unvulcanized rubber composition. Furthermore, the vulcanized rubber compositions of Examples 1 to 6 and Comparative Examples 1 and 2 were obtained by press vulcanizing the obtained unvulcanized rubber composition for 25 minutes at 160 ° C. using a predetermined mold. A product was made.

(Degree of crosslinking (SWELL))
The vulcanized rubber composition was extracted with toluene, and the volume change rate (SWELL) before and after extraction was measured. The smaller the measured value, the more the variation in cross-linking is suppressed, which is preferable.

(Viscoelasticity test)
Measurement of viscoelasticity (complex elastic modulus E ′ and loss coefficient tan δ) when a 10% initial strain was applied using a viscoelastic spectrometer manufactured by Iwamoto Seisakusho and a dynamic strain of 2% was applied at 50 ° C. did. The larger E ′, the higher the rigidity and the better, and the larger the value of tan δ, the higher the grip force and the better the grip performance.

(Tensile test)
In accordance with JIS K6251 “Vulcanized rubber and thermoplastic rubber—Determination of tensile properties”, a tensile test was performed on a sample of dumbbell No. 3, and a stress at 300% elongation (M300) was measured. It shows that abrasion abrasion resistance is excellent, so that M300 is large.

(hardness)
The hardness of the vulcanized rubber composition of each blend was measured using a JIS-A hardness meter in accordance with the test method of “Hardness test method of vulcanized rubber and thermoplastic rubber” of JIS-K6253.

  The evaluation results of each test are shown in Tables 1 and 2.

Claims (2)

For 100 parts by weight of diene rubber,
0.2 to 10 parts by weight of carboxylic acid metal salt,
A rubber composition containing 0.2 to 5 parts by weight of a basic vulcanization accelerator and 0.2 to 5 parts by weight of a thiazole vulcanization accelerator. A pneumatic tire having a tire tread using the rubber composition according to claim 1.