JP5921605B2 - Rubber composition for tire and pneumatic tire using the same - Google Patents

Description

The present invention relates to a tire rubber composition that can produce a high-performance, environmentally friendly tire, and a pneumatic tire using the same.

Conventionally, as a reinforcing filler for tires, silica is often used in addition to carbon black, which is a black filler, and in addition to silica, calcium carbonate, magnesium carbonate, and calcium hydroxide have been studied.

Among these fillers, when white fillers, especially silica, are used, sufficient performance cannot be obtained due to low dispersibility of silica, and wear resistance performance decreases particularly when used in tread applications. There was a problem to do. Various silane coupling agents and silylating agents have been used to remedy this problem, but they are all expensive and are used as energy to synthesize them, or in some cases as part of the raw materials. There are concerns about the future supply of fossil fuels.

On the other hand, techniques using amino acids as vulcanization accelerators are known (Patent Documents 1 and 2). However, in these methods, carbon black is used as a filler, and white fillers such as silica are not described. Therefore, the problem of a white filler with low dispersibility is not presented.

Japanese Patent Laid-Open No. 61-212241 JP-A-61-2212242

An object of the present invention is to provide a rubber composition for a tire that can solve the problem of dispersibility of the white filler while considering the environment and can produce a higher performance tire, and a tire using the rubber composition. That is.

The present invention relates to a tire rubber composition containing a diene rubber, an amino acid, and a white filler.

It is preferable to contain stearic acid and / or zinc white.

It is preferable not to contain a silane coupling agent and a silylating agent.

The white filler is preferably 50% by weight or more of the total filler.

The natural rubber and / or modified natural rubber is preferably contained in an amount of 50% by weight or more based on the total diene rubber component.

The amino acid preferably has a mercapto group, a disulfide group, a monosulfide group, a nitrogen-containing heterocyclic ring, a benzene ring, a phenolic hydroxyl group, or three or more amino groups.

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

Since the rubber composition for tires of the present invention contains an amino acid and a white filler, it is environmentally friendly and does not use a silane coupling agent or silylating agent, and prepares for future reduction of petroleum resources. The rubber composition can provide a high-performance tire.

Hereinafter, the present invention will be described in detail.

The rubber composition for tires of the present invention contains a diene rubber, an amino acid, and a white filler.

Diene rubbers include natural rubber (NR), modified natural rubber, butadiene rubber (BR), syndiotactic-1,2-polybutadiene (1,2BR), styrene-butadiene copolymer rubber (SBR), and isoprene rubber. (IR), acrylonitrile-butadiene copolymer rubber (NBR), chloroprene rubber (CR), styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isoprene copolymer rubber, isoprene-butadiene copolymer rubber and the like. Among these, natural rubber or modified natural rubber is preferable from the viewpoints of consideration for the environment, wear resistance, low rolling resistance, handling stability, and tensile strength. As the modified rubber, epoxidized natural rubber is preferable because it can be synthesized relatively easily and has good performance.

As the epoxidized natural rubber, commercially available epoxidized natural rubber may be used, or natural rubber may be epoxidized. The method for epoxidizing natural rubber is not particularly limited, and can be carried out using a method such as a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, a peracid method, for example, Examples include a method of reacting natural rubber with an organic peracid such as peracetic acid or performic acid.

The epoxidation rate of the epoxidized natural rubber is preferably 5 mol% or more, and more preferably 10 mol% or more. If the epoxidation rate is less than 5 mol%, the modifying effect on the rubber composition tends to be small. The epoxidation rate is preferably 80 mol% or less, and more preferably 60 mol% or less. When the epoxidation rate exceeds 80 mol%, the polymer component is gelled, which is not preferable.

The content of the modified natural rubber and / or natural rubber is preferably 50% by weight or more, more preferably 60% by weight or more, further preferably 70% by weight or more, and most preferably 100% by weight in the diene rubber component. It is. Thereby, it can be set as the rubber composition for tires in consideration of the environment. Further, since the modified natural rubber and / or proteins and phospholipids contained in the natural rubber also interact, it becomes easier to disperse the white filler more highly than the synthetic rubber. In synthetic rubber, functional groups capable of interacting or chemically reacting with the white filler can be introduced into the terminal or main chain at the time of polymerization, whereas natural rubber and modified natural rubber already have rubber molecules. Therefore, it is difficult to introduce a functional group such as a synthetic rubber by modification. Therefore, there is a merit of using an amino acid which is a natural product rich in reactivity as a material for modifying natural rubber. In addition, an amino group contained in an amino acid is easily reacted with an epoxy group, and can be synthesized relatively easily as described above, and epoxidized natural rubber is used as a modified natural rubber in terms of good performance. It is preferable.

In the present invention, a white filler is used instead of carbon black as the filler. Examples of the white filler include silica, calcium carbonate, magnesium carbonate, calcium hydroxide, aluminum hydroxide, titanium oxide, and starch. Among these, silica, aluminum hydroxide, and starch are preferable because they are excellent in reinforcing properties and rolling resistance. Silica includes silica produced by a wet method or a dry method, but is not particularly limited.

The BET adsorption specific surface area of silica is preferably 20 m ² / g or more, more preferably 40 m ² / g or more, and still more preferably 50 m ² / g or more. When the BET adsorption specific surface area of silica is less than 20 m ² / g, the reinforcing effect is small. Further, the BET adsorption specific surface area of silica is preferably 600 m ² / g or less, more preferably 500 m ² / g or less, and further preferably 450 m ² / g or less. It is. If the N ₂ SA of silica exceeds 600 m ² / g, the viscosity of the unvulcanized rubber tends to increase and the processability tends to decrease.

The content of silica is 10 parts by weight or more, preferably 20 parts by weight or more, more preferably 30 parts by weight or more with respect to 100 parts by weight of the diene rubber. If the silica content is less than 10 parts by weight, the strength of the rubber will be insufficient. The silica content is 150 parts by weight or less, preferably 100 parts by weight or less, more preferably 80 parts by weight or less. When the silica content exceeds 150 parts by weight, the viscosity of the unvulcanized rubber increases and the processability decreases.

In the present invention, since an amino acid is used in combination with a white filler, it is not necessary to use a silane coupling agent or silylating agent used in combination with the white filler, but a silane coupling agent or silylating agent may be used in combination. it can.

An amino acid is a compound having an amino group and a carboxyl group in the molecule, and the amino group or the carboxyl group interacts or reacts with a silanol group of silica. In addition, amino groups, carboxyl groups, and other functional groups may react or interact with rubber. By these actions, the dispersibility of the white filler can be improved. Examples of amino acids include L-methionine, L-cystine, L-cysteine, L-arginine, L-histidine, L-tyrosine, glycine, L-alanine, L-phenylalanine, L-lysine, L-dopa, and L-asparagine. , L-aspartic acid, L-glutamic acid and the like. Amino acids have a mercapto group, a disulfide group, a monosulfide group, a nitrogen-containing heterocyclic ring, a benzene ring, a phenolic hydroxyl group, or three or more amino groups, and can easily interact with or react with the rubber component, thereby improving dispersibility. Is preferable from the viewpoint of high. Of these, a monosulfide group or an amino acid having 3 or more amino groups is preferable in terms of greatly improving the wear resistance. An amino acid having a nitrogen-containing heterocycle is preferred in that the rolling resistance can be greatly reduced. Furthermore, the L form of the amino acid as described above exists in nature and is synthesized in the living organism. For this reason, such L-form amino acids can be obtained by extraction from hydrolysis of natural proteins, or fermentation using microorganisms, and are environmentally friendly compared to silane coupling agents, and are generally obtained by an energy-saving process. . In particular, L-amino acids obtained by fermentation are preferable in terms of energy saving.

The amino acid content is 0.1 parts by weight or more, preferably 0.25 parts by weight or more, more preferably 0.5 parts by weight or more, and further preferably 2 parts by weight or more with respect to 100 parts by weight of the diene rubber. . When the amino acid content is less than 0.1 parts by weight, the dispersibility improving effect, the reinforcing effect, and the rolling resistance reducing effect of the white filler tend not to be obtained. The amino acid content is 20 parts by weight or less, preferably 10 parts by weight or less, more preferably 6 parts by weight or less, and still more preferably 5 parts by weight or less. If the amino acid content exceeds 20 parts by weight, it will be difficult to uniformly disperse in the rubber, resulting in precipitation or unnecessary increase in cost.

Amino acids can be mixed after previously reacting with rubber or white filler. By making it react beforehand, there exists a tendency for the effect which improves the dispersibility of a white filler, the improvement effect of abrasion resistance, and the rolling resistance reduction effect to become high.

The tire rubber composition of the present invention preferably contains stearic acid and / or zinc white from the viewpoint that the processability of the rubber composition can be improved and the vulcanization reaction can proceed well. The content of stearic acid is preferably 0.2 to 5 parts by weight with respect to 100 parts by weight of the rubber component. On the other hand, the content of zinc white is preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the rubber component.

The sulfur content is 0.2 parts by weight or more, preferably 0.5 parts by weight or more, more preferably 1 part by weight or more with respect to 100 parts by weight of the diene rubber. If the sulfur content is less than 0.2 parts by weight, the rubber becomes too soft and is not suitable as a tire rubber. The sulfur content is 8 parts by weight or less, preferably 4 parts by weight or less, and more preferably 2.5 parts by weight or less. When the amino acid content exceeds 8 parts by weight, rubber adhesion deteriorates during tire molding due to sulfur blooming.

In the tire rubber composition of the present invention, in addition to the diene rubber, white filler, amino acid, and the like, a reinforcing agent such as carbon black, an anti-aging agent, a wax, a vulcanization accelerator, and the like as necessary. A compounding agent used in the rubber industry can be appropriately blended.

Examples of the vulcanization accelerator include guanidine vulcanization accelerators and sulfenamide vulcanization accelerators. The compounding amount of the vulcanization accelerator is preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the rubber component.

The tire of the present invention is produced by a usual method using the tire rubber composition of the present invention. That is, if necessary, the rubber composition for tires of the present invention blended with the above compounding agent is extruded in accordance with the shape of each member of the tire at an unvulcanized stage, and is processed on a tire molding machine by a normal method. An unvulcanized tire is formed by molding with. The unvulcanized tire is heated and pressurized in a vulcanizer to obtain a tire.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this does not limit this invention.

Examples 1-30 and Comparative Examples 1-5
(1) Description of various chemicals SBR: Nippon NS116 manufactured by Nippon Zeon Co., Ltd. (solution polymerization SBR, 21% bound styrene, Tg-25 ° C.)
Natural rubber: RSS # 3
Epoxidized natural rubber: GUTHRIE POLYMER SDN. BHD ENR-25 (epoxidation rate: 25 mol%, glass transition point: -41 ° C)
Silica: Ultrasil VN3 manufactured by Degussa
Carbon Black: Diamond Black I (ISAF Carbon) manufactured by Mitsubishi Chemical Corporation
Wax: Ozoace 0355 made by Nippon Seiki
Anti-aging agent: NOCRACK 6C (N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Stearic acid: Tungsten zinc oxide manufactured by NOF Corporation: Zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Sulfur powder vulcanization accelerator manufactured by Tsurumi Chemical Co., Ltd. BBS: Ouchi Shinsei Chemical Industry ( Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by
Vulcanization accelerator DPG: Noxeller D (diphenylguanidine) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Amino acid 1: L-methionine (containing monosulfide bond) manufactured by Ajinomoto Co., Inc.
Amino acid 2: L-cystine (containing disulfide bond) manufactured by Ajinomoto Co., Inc.
Amino acid 3: L-cysteine (containing mercapto group) manufactured by Kishida Chemical Co., Ltd.
Amino acid 4: L-arginine (containing 3 or more amino groups) manufactured by Ajinomoto Co., Inc.
Amino acid 5: L-histidine manufactured by Ajinomoto Co., Inc. (containing a heterocyclic ring containing two N atoms)
Amino acid 6: L-tyrosine (hydroxyphenyl group-containing) manufactured by Ajinomoto Co., Inc.

Using a 1.7L Banbury mixer of Kobe Steel, Inc., the chemicals in the blending amounts shown in step 1 of Tables 1 and 2 were added so that the filling rate was 58%, and the conditions were 80 rpm. Then, the kneading was carried out for 3 to 8 minutes until the indicated temperature of the kneader reached 140 ° C. In Examples 25 to 30 and Comparative Example 5, silica was added in two portions in Step 1. Once discharged, the kneaded product obtained in step 1 is added with the amounts of sulfur and vulcanization accelerator shown in step 2 and kneaded at 50 ° C. for 3 minutes using an open roll and unvulcanized. A rubber composition was obtained. The unvulcanized rubber composition obtained in Step 2 was formed into a size necessary for each evaluation and subjected to press vulcanization at 150 ° C. for an optimum time, thereby preparing rubber compositions of Examples and Comparative Examples. The optimal vulcanization time was determined according to t100 obtained using a vulcanization tester such as a curast meter.

In each of the following measurements, Comparative Example 1 is shown in Table 1 (Examples 1 to 6, Comparative Example 1), Comparative Example 2 is shown in Table 2 (Examples 7 to 12 and Comparative Example 2), and Table 3 (Execution Example). Examples 13 to 18 and Comparative Example 3) are Comparative Examples 3, Table 4 (Examples 19 to 24 and Comparative Example 4) are Comparative Examples 4 and Table 5 (Examples 25 to 30 and Comparative Example 5) are Comparative Examples. 5 was used as a reference composition.

(Abrasion resistance test)
Vulcanized rubber specimens for lamborn abrasion test obtained from each vulcanized rubber composition under the conditions of load load of 2.5 kg, temperature of 20 ° C., slip rate of 40%, test time of 2 minutes with a lamborn abrasion tester. The wear loss was measured, the amount of Lambourn wear was measured, the amount of capacity loss of each formulation was calculated, and the wear resistance index of the reference formulation was set to 100, and the wear resistance was indicated by the following formula. The larger the wear resistance index, the better the wear resistance.

(Abrasion resistance index) = (capacity loss amount of reference blend) / (capacity loss amount of each blend) × 100

(Rolling resistance test)
A rubber slab sheet of 2 mm × 130 mm × 130 mm was prepared as a vulcanized rubber composition, a test piece for measurement was cut out from the rubber slab sheet, and a temperature of 70 ° C. was obtained using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho). Under the conditions of initial strain 10%, dynamic strain 2%, and frequency 10Hz, tan δ of each test rubber composition was measured, and the rolling resistance index of the reference blend was set to 100, and the rolling resistance characteristics were respectively displayed as an index by the following formula. did. The smaller the rolling resistance index, the lower the rolling resistance and the better the rolling resistance characteristics.

(Rolling resistance index) = (tan δ of each formulation) / (tan δ of reference formulation) × 100

(Evaluation of steering stability index)
Similarly to the above, each test rubber composition was tested under the conditions of a temperature of 70 ° C., an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz using a viscoelastic spectrometer VES (manufactured by Iwamoto Seisakusho Co., Ltd.). The complex elastic modulus E ^* was measured, the elastic modulus of the reference blend was set to 100, and the steering stability index was indicated as an index according to the following formula. The larger the steering stability index, the higher the steering stability and the better.

(Steering stability index) = (E ^{* of} each formulation) / (E ^{* of the} reference formulation) × 100

(Tensile strength test)
JIS K 6251 vulcanized rubber and thermoplastic rubber-Tensile strength was measured according to the method of obtaining tensile properties. With the tensile strength of the reference blend as 100, the tensile strength index was calculated according to the following formula and displayed as an index. The larger the tensile strength index, the higher the strength and the better.

(Tensile strength index) = (Tensile strength of each formulation) / (Tensile strength of standard formulation) × 100

As can be seen from Tables 1 to 4, in the examples, the wear resistance was equal to or significantly improved compared to the reference formulation. The rolling resistance index was also small at the reference blending ratio and could be reduced. While improving E ^* , the steering stability index also improved. In particular, an amino acid having a monosulfide bond or an amino acid having three or more amino groups can greatly improve wear resistance and steering stability, and can also reduce rolling resistance. Furthermore, the tensile strength was improved. In addition, in the amino acid having a heterocyclic ring containing two N, the wear resistance and the steering stability were almost the same as those of the reference blend, but the rolling resistance could be greatly reduced. Although other amino acids were large and small, the improvement effect could be confirmed.

In addition, although the effect was obtained by either the system used in combination with carbon black or the system of silica alone as the filler, the blending of silica alone was more excellent. Moreover, although it does not understand in the numerical value of a table | surface, when tan-delta at 70 degreeC of a reference | standard mixing | blending is compared, since the compound of a silica single combination is lower than a carbon black combination mixing | blending, the effect is high in the mixing | blending with a high silica compounding ratio.

Furthermore, as a rubber, the effect was higher when blended with only natural rubber and / or modified natural rubber than blended with synthetic rubber.

Claims (6)

Containing a diene rubber, an amino acid, and silica;
The rubber composition for tires, wherein the diene rubber contains 50% by weight or more of natural rubber and / or modified natural rubber in the total diene rubber component.
(However, it contains diene rubber, amino acid, and silica,
The diene rubber contains natural rubber and / or modified natural rubber in an amount of 50% by weight or more in the total diene rubber component,
Excluding tire rubber compositions that do not contain silane coupling agents and silylating agents. ) Containing a diene rubber, an amino acid, and silica;
A rubber composition for tires, wherein the diene rubber contains natural rubber and / or modified natural rubber and styrene-butadiene copolymer rubber. Furthermore, the rubber composition for tires of Claim 1 or 2 containing a stearic acid and / or zinc white. The rubber composition for tires according to any one of claims 1 to 3, wherein silica is 50% by weight or more in all fillers. The tire rubber composition according to any one of claims 1 to 4, wherein the amino acid has a mercapto group, a disulfide group, a monosulfide group, a nitrogen-containing heterocyclic ring, a benzene ring, a phenolic hydroxyl group, or three or more amino groups. object. A pneumatic tire using the tire rubber composition according to any one of claims 1 to 5.