JP2007321039A - Rubber composition for tire and tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for tire remarkably suppressing reversion, improving heat ageing resistance, and to provide a tire using the same. <P>SOLUTION: The invention relates to the rubber composition for tire comprising an epoxidized natural rubber, sulfur and a carboxylic acid represented by general formula; R-COOH (R is a 3-16C alkyl group, or a 3-22C unsaturated fatty acid with 1-3 of double bond). The invention relates to the tire using the same. <P>COPYRIGHT: (C)2008,JPO&INPIT

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. Epoxidized natural rubber has attracted attention as a material derived from resources other than petroleum.

  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

  An object of the present invention is to provide a tire rubber composition that can remarkably suppress reversion and improve heat aging characteristics, and a tire using the same.

The present invention relates to epoxidized natural rubber, sulfur, and the following general formula R-COOH
(R is an alkyl group having 3 to 16 carbon atoms, or an unsaturated aliphatic group having 1 to 3 double bonds and 3 to 22 carbon atoms). The present invention relates to a tire rubber composition.

  When R is an alkyl group, the carbon number of R is preferably 3-12.

  When R is an alkyl group, the carbon number of R is preferably 8-12.

  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, by containing a predetermined rubber component, sulfur and a predetermined carboxylic acid, a rubber composition for a tire capable of remarkably suppressing reversion and improving heat aging characteristics and the same are used. Tires can be provided.

  The rubber composition for tires of the present invention contains a rubber component, sulfur and a predetermined carboxylic acid.

  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 carboxylic acid used in the present invention has the following general formula: R-COOH
(R is an alkyl group having 3 to 16 carbon atoms, or an unsaturated aliphatic group having 1 to 3 double bonds and 3 to 22 carbon atoms).

  R is an alkyl group or an unsaturated aliphatic group. When used at low temperatures such as studless tires, unsaturated aliphatic groups are preferred because of their low melting points. Moreover, when using as a normal tire, an alkyl group is preferable from the reason that there is no double bond and it is excellent in heat resistance.

  When R is an alkyl group, the carbon number of R is 3 or more, preferably 8 or more. When the carbon number of R is less than 3, it shows strong acidity, which is dangerous for handling. Also, it has a little smell. The carbon number of R is 16 or less, preferably 12 or less. When the carbon number of R exceeds 16, the relative amount of carboxylic acid decreases, and the effect of improving physical properties decreases.

  When R is unsaturated aliphatic, the number of R double bonds is 1 to 3. When the number of R double bonds exceeds 3, the effect of improving physical properties decreases. The number of R double bonds is preferably 2.

  When R is unsaturated aliphatic, R has 3 to 22 carbon atoms.

  The content of carboxylic acid 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. When the carboxylic acid content is less than 0.5 parts by weight, the effect of improving physical properties tends to be remarkably reduced. Moreover, 10 weight part or less is preferable and, as for content of carboxylic acid, 8 weight part or less is more preferable. When the carboxylic acid content exceeds 10 parts by weight, the rolling resistance of the tire 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, carboxylic acid, silica and silane coupling agent, the rubber composition of the present invention includes compounding agents conventionally used in the rubber industry, such as anti-aging agent, zinc oxide, stearic acid, You may contain a vulcanization accelerator etc.

  In consideration of the environment, the present invention aims to prepare for a future reduction in the supply of petroleum, and preferably does not contain aromatic carboxylic acid, 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 compounding agent as necessary, it is extruded according to the shape of the tire member, bonded together with other members, and heated 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
Carboxylic acid: butyric acid (R carbon number: 3, R double bond: 0), valeric acid (R carbon number: 4, R double bond: 0), hexanoic acid (R carbon number: 5, R double bond: 0), octanoic acid (R carbon number: 7, R double bond: 0), decanoic acid (R carbon number: 9, R double bond: 0), dodecanoic acid ( R carbon number: 11, R double bond: 0), myristic acid (R carbon number: 13, R double bond: 0), palmitic acid (R carbon number: 15, R double bond) : 0), stearic acid (carbon number of R: 17, double bond of R: 0), hebenic acid (carbon number of R: 21, double bond of R: 0), oleic acid (carbon number of R: 17, R double bond: 1), linoleic acid (R carbon number: 17, R double bond: 2), linolenic acid (R carbon number: 17, R double bond: 3)
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 Industry Co., Ltd. (1): Ouchi Shinsei Chemical 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 1-11 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 11 and Comparative Examples 1 to 3. In addition, about carboxylic acid, what was shown in Table 2 was mix | blended.

(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 the smaller the reversion rate, the better the reversion can be suppressed.
(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 2 shows the evaluation results of the above tests.

  From Table 2, it can be seen that in Examples 1 to 11 containing a predetermined carboxylic acid, reversion is suppressed and the tensile properties and heat aging characteristics are excellent.

  In Comparative Example 1, no carboxylic acid is contained and reversion cannot be suppressed.

  In Comparative Examples 2 and 3, the saturated carboxylic acid has a large number of carbon atoms, and reversion cannot be suppressed.

Claims (5)

Epoxidized natural rubber, sulfur and the following general formula R-COOH
(R is an alkyl group having 3 to 16 carbon atoms, or an unsaturated aliphatic group having 1 to 3 double bonds and 3 to 22 carbon atoms.)
The rubber composition for tires containing the carboxylic acid represented by these. The tire rubber composition according to claim 1, wherein when R is an alkyl group, R has 3 to 12 carbon atoms. The rubber composition for tires according to claim 1 or 2, wherein when R is an alkyl group, R has 8 to 12 carbon atoms. 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.