JP5122088B2 - Rubber composition for tire and tire using the same - Google Patents

Description

  The present invention relates to a rubber composition for a tire and a tire using the same.

  In recent years, many efforts have been made to improve vehicle fuel efficiency and tire wear resistance. Furthermore, recently, environmental issues have become more important, and regulations for suppressing carbon dioxide emissions have been strengthened in order to suppress global warming. In addition, petroleum resources are limited, and in order to prepare for a decrease in the supply amount of petroleum resources, many materials derived from non-oil resources have been used. Among the rubber compositions for tires, in the rubber composition for treads, natural rubber is not sufficient in order to secure sufficient grip performance, so that a modified natural rubber has been used. Of these, epoxidized natural rubber has attracted attention.

  However, since the epoxidized natural rubber causes reversion during rubber vulcanization, the original performance has not been sufficiently exhibited. In addition, heat aging characteristics are poor, and there is a problem that performance deteriorates during use of the tire.

  Patent Document 1 discloses a vulcanization acceleration activator containing a predetermined carboxylic acid and an aromatic carboxylic acid zinc salt. However, it is not considered to apply it to a tire rubber composition.

Japanese Patent No. 2657245

  [Technical Field] The present invention provides a tire rubber composition that is environmentally friendly, prepares for a future reduction in the supply of oil, further remarkably suppresses reversion and improves heat aging characteristics, and a tire using the same. The purpose is to provide.

  The present invention relates to a tire rubber composition containing epoxidized natural rubber, sulfur, and a hydroxycarboxylic acid metal salt or a polybasic acid metal salt.

  The hydroxycarboxylic acid or polybasic acid in the metal salt is preferably a biological acid.

  The hydroxycarboxylic acid is preferably lactic acid.

  The tire rubber composition preferably further contains silica.

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

  According to the present invention, it contains an epoxidized natural rubber, sulfur, and a hydroxycarboxylic acid metal salt or polybasic acid metal salt. It is possible to provide a tire rubber composition capable of remarkably suppressing reversion and improving heat aging characteristics, and a tire using the same.

  The rubber composition for tires of the present invention contains a rubber component, sulfur, and a hydroxycarboxylic acid metal salt or polybasic acid metal salt.

  The rubber component contains epoxidized natural rubber (ENR).

  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 performed 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 mol% or more, and more preferably 10 mol% or more. When the epoxidation ratio of ENR is less than 5 mol%, the glass transition temperature (Tg) is not increased so that sufficient grip strength as a tire tends to be not obtained. The epoxidation rate of ENR is preferably 65 mol% or less, and more preferably 60 mol% or less. When the epoxidation rate of ENR exceeds 65 mol%, the hardness increases excessively, resulting in a decrease in grip performance, and at the same time, the bending fatigue resistance tends to be greatly decreased.

  The content of ENR in the rubber component is preferably 25% by weight or more, and more preferably 40% by weight or more. If the content of ENR is less than 25% by weight, it is not possible to consider the environment or prepare for a future reduction in the amount of oil supplied, and there is a tendency that sufficient grip strength as a tire cannot be obtained. The content of ENR is most preferably 100% by weight.

  As the rubber component, in addition to ENR, for example, natural rubber (NR), styrene butadiene rubber (SBR), butadiene rubber (BR), isoprene rubber (IR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR). Acrylonitrile butadiene rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (X-IIR) and the like. These rubber components may be used in combination with ENR, but they can be environmentally friendly and can be prepared for future reductions in oil supply, and these rubber components are relatively expensive compared to ENR. Therefore, it is preferable that no rubber component other than ENR is contained.

  As sulfur, sulfur generally used in the rubber industry during vulcanization can be used.

  The content of sulfur is preferably 0.5 parts by weight or more, more preferably 0.8 parts by weight or more with respect to 100 parts by weight of the rubber component. If the sulfur content is less than 0.5 parts by weight, the rubber tends to be too soft and the wear resistance tends to be greatly reduced. The sulfur content is preferably 4 parts by weight or less, and more preferably 3 parts by weight or less. When the sulfur content exceeds 4 parts by weight, the hardness of the rubber is excessively increased, and not only a sufficient grip performance cannot be obtained, but also the wear resistance tends to be lowered.

  The hydroxycarboxylic acid in the hydroxycarboxylic acid metal salt refers to a carboxylic acid having a hydroxyl group, for example, an aliphatic hydroxycarboxylic acid derived from a living organism such as gluconic acid, lactic acid, malic acid, tartaric acid, citric acid, and isocitric acid. And aromatic hydroxycarboxylic acids such as salicylic acid, mandelic acid and gallic acid. Of these, biologically-derived aliphatic hydroxycarboxylic acids are preferred because they can be environmentally friendly, can be prepared for future reductions in oil supply, and are relatively inexpensive. Is more preferable, and lactic acid is more preferable.

  Examples of the metal in the hydroxycarboxylic acid metal salt include sodium, calcium, potassium, magnesium, zinc and the like. Of these, calcium or zinc is preferable and calcium is more preferable because of its excellent effect of improving rubber properties.

  Examples of the hydroxycarboxylic acid metal salt that satisfies the above conditions include calcium gluconate, zinc gluconate, calcium lactate, and zinc lactate.

  The polybasic acid in the polybasic acid metal salt means an acid having two or more carboxyl groups in one molecule, for example, succinic acid, malic acid, fumaric acid, maleic acid, tartaric acid, etc. Bibasic acids derived from other organisms, other dibasic acids such as sulfuric acid, silicic acid and terephthalic acid, tribasic acids derived from organisms such as citric acid and isocitric acid, and other tribasic acids such as phosphoric acid . Among these, biologically-derived polybasic acids are preferred because they are environmentally friendly and can be prepared for future reductions in oil supply, and are excellent in reducing the rolling resistance of tires. The derived dibasic acid is more preferred, and succinic acid is more preferred.

  Examples of the metal in the polybasic acid metal salt include sodium, calcium, potassium, magnesium, zinc and the like. Of these, sodium is preferred because it is relatively inexpensive.

  An example of a polybasic acid metal salt that satisfies the above conditions is disodium succinate.

  The content of the hydroxycarboxylic acid metal salt or polybasic acid metal salt is preferably 0.5 parts by weight or more and more preferably 1 part by weight or more with respect to 100 parts by weight of the rubber component. If the content of the hydroxycarboxylic acid metal salt or polybasic acid metal salt is less than 0.5 parts by weight, the effect of improving the physical properties tends to be too small. Further, the content of the hydroxycarboxylic acid metal salt or polybasic acid metal salt is preferably 10 parts by weight or less, and more preferably 8 parts by weight or less. When the content of the hydroxycarboxylic acid metal salt or polybasic acid metal salt exceeds 10 parts by weight, the rolling resistance tends to increase.

  The tire rubber composition of the present invention preferably contains silica.

  Examples of silica include silica produced by a wet method, silica produced by a dry method, and the like, but there is no particular limitation, and those usually used in the rubber industry can be used.

  The content of silica 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. If the silica content is less than 20 parts by weight, it is not possible to consider the environment or prepare for a future reduction in oil supply, and the rolling resistance of the tire will increase, and sufficient wet grip will be achieved. There is a tendency that performance cannot be obtained. Further, the silica content is preferably 100 parts by weight or less, and more preferably 80 parts by weight or less. When the silica content exceeds 100 parts by weight, the hardness of the rubber is remarkably increased, and there is a tendency that sufficient grip force cannot be obtained.

  In the present invention, it is preferable to use a silane coupling agent in combination with silica.

  As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-tri Ethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilyl) Butyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) Trisulf Bis (2-trimethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis ( 4-triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N , N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 2-trimethoxy Silylethyl-N, N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazole tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxy Sulfide series such as silylpropyl methacrylate monosulfide, mercapto series such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, vinyltriethoxysilane , Vinyl type such as vinyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3- (2- Amino-based amino groups such as aminopropyl) aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycid Glycidoxy type such as xylpropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, nitro type such as 3-nitropropyltrimethoxysilane, 3-nitropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3 -Chloro series such as chloropropyltriethoxysilane, 2-chloroethyltrimethoxysilane, 2-chloroethyltriethoxysilane, and the like. These silane coupling agents may be used alone or in combination of two or more.

  The content of the silane coupling agent is preferably 3 parts by weight or more and more preferably 4 parts by weight or more with respect to 100 parts by weight of silica. When the content of the silane coupling agent is less than 3 parts by weight, silica cannot be sufficiently dispersed in the rubber, and the rolling resistance tends to increase. Further, the content of the silane coupling agent is preferably 15 parts by weight or less, and more preferably 12 parts by weight or less. When the content of the silane coupling agent exceeds 15 parts by weight, the rolling resistance tends to be deteriorated.

  In addition to the rubber component, sulfur, hydroxycarboxylic acid metal salt or polybasic acid metal salt, silica, and silane coupling agent, the rubber composition of the present invention includes a compounding agent conventionally used in the rubber industry, for example, You may contain a stearic acid, a zinc oxide, a vulcanization accelerator, etc.

  In consideration of the environment, the present invention aims to prepare for a future reduction in the amount of oil supplied, and preferably does not contain carbon black, aroma oil, or the like.

  The rubber composition for tires of the present invention is used for various tire members, and is particularly preferably used as a tread.

  The tire of the present invention is produced by a usual method using the rubber composition of the present invention. That is, using the rubber composition of the present invention appropriately blended with the above-described compounding agents as necessary, for example, extrusion processing is performed in accordance with the shape of the tread, bonding together with other members, and heating on a tire molding machine. It can be manufactured by pressing.

  The tire of the present invention can be an eco-tire that can be environmentally friendly or can be prepared for a future reduction in the supply of oil.

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

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
Epoxidized natural rubber (ENR): ENR-25 (epoxidation rate: 25 mol%) manufactured by Kumplan Guthrie Berhad (Malaysia)
Silica: Ultrazil VN3 manufactured by Degussa
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Polybasic acid metal salt: Disodium succinate hydroxycarboxylic acid metal salt manufactured by Fuso Chemical Industry Co., Ltd. (1): Calcium gluconate hydroxycarboxylic acid metal salt manufactured by Fuso Chemical Industry Co., Ltd. (2): Fuso Chemical Industry HEALTHOUS Zn (Zinc Gluconate) manufactured by
Hydroxycarboxylic acid metal salt (3): Calcium lactate polybasic acid manufactured by Fuso Chemical Industry: Succinic acid hydroxycarboxylic acid manufactured by Fuso Chemical Industry: Purified citric acid (anhydrous anhydrous) )
Stearic acid: Tsubaki zinc oxide manufactured by Nippon Oil & Fats Co., Ltd .: Zinc Hua No. 2 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powder sulfur vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Kogyo Co., Ltd.
Vulcanization accelerator (2): Noxeller D (diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

Examples 1-4 and Comparative Examples 1-3
According to the formulation shown in Table 1, using a Banbury mixer, chemicals other than sulfur and vulcanization accelerator were kneaded for 4 minutes at 130 ° C. to obtain a kneaded product. Next, using an open roll, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 4 minutes at 60 ° C. to obtain an unvulcanized rubber composition. Furthermore, the obtained unvulcanized rubber composition was press vulcanized for 10 minutes under the condition of 170 ° C. to obtain vulcanized rubber compositions of Examples 1 to 4 and Comparative Examples 1 to 3.

(Reversion rate)
Using a curast meter, the vulcanization curve of the unvulcanized rubber composition at 170 ° C. was measured. And the reversion rate of each compounding was computed with the following formula. In addition, it shows that reversion rate property is so small that reversion rate can be suppressed and it is excellent.
(Reversion rate (%)) = (F _max −F) / (F _max −F _min ) × 100
In the equation, F _max is the maximum value of torque, F _min is the minimum value of torque, and F is the torque 15 minutes after the start of measurement.

(Heat aging test)
In accordance with JIS K 6251 “Vulcanized Rubber and Thermoplastic Rubber-Determination of Tensile Properties”, using a No. 3 dumbbell-shaped test piece made of the vulcanized rubber composition, the breaking strength (T _B ) and elongation at break (E _B ) was measured. Further, using a No. 3 dumbbell-type test piece formed from the vulcanized rubber composition of the rubber composition obtained by 72 hours heat aging at conditions of 100 ° C., it was similarly measured T _B and E _B. Then, the measured value of the test piece after aging to the measured value of the test piece before aging from (after aging / before aging) was calculated T _B rate of change (%) and E _B rate of change (%), respectively. Incidentally, the larger the T _B and E _B, excellent tensile properties, higher T _B change rate and the E _B change rate is large, rubber properties change due to heat aging is small, the better the heat aging properties.

  Table 1 shows the evaluation results of the above tests.

  From Table 1, it can be seen that in Examples 1 to 4 containing a hydroxycarboxylic acid metal salt or a polybasic acid metal salt, reversion is suppressed and the tensile properties and heat aging characteristics are excellent.

  In Comparative Example 1, a hydroxycarboxylic acid metal salt or a polybasic acid metal salt is not contained, and reversion cannot be suppressed, and heat aging characteristics are deteriorated.

  In Comparative Example 2, since it contains not a hydroxycarboxylic acid metal salt or a polybasic acid metal salt but a polybasic acid, the effect of suppressing reversion is insufficient, and further, the tensile properties and heat aging characteristics are reduced. To do.

Claims (5)

The rubber component 100 parts by weight containing more than 25 wt% epoxidized natural rubber, sulfur 0.5-4 parts by weight, and a hydroxycarboxylic acid metal salt or a polybasic acid metal salt 0.5-10 parts by weight A tire rubber composition comprising:
The hydroxycarboxylic acid or polybasic acid in the hydroxycarboxylic acid metal salt or polybasic acid metal salt is gluconic acid, lactic acid or succinic acid, and the metal is calcium, zinc or sodium,
Rubber composition for tires. The tire rubber composition according to claim 1, wherein the hydroxycarboxylic acid or polybasic acid is lactic acid. The tire rubber composition according to claim 1, wherein the hydroxycarboxylic acid metal salt or polybasic acid metal salt is calcium gluconate, zinc gluconate, calcium lactate or disodium succinate. Furthermore, the rubber composition for tires of Claim 1, 2, or 3 containing a silica. A tire using the tire rubber composition according to claim 1, 2, 3 or 4.