阅读说明：本技术 橡胶组合物及使用了该橡胶组合物的充气轮胎 (Rubber composition and pneumatic tire using same ) 是由 三原谕 于 2019-02-06 设计创作，主要内容包括：在本发明中,为了提供同时提高滚动阻力性、湿路抓着性能和耐磨损性的橡胶组合物,相对于二烯系橡胶100质量份,配合了5～200质量份的二氧化硅、相对于上述二氧化硅的质量为1～20质量％的硅烷偶联剂、以及相对于上述二氧化硅的质量为1～20质量％的聚甘油脂肪酸酯,所述聚甘油脂肪酸酯源自碳原子数6～24的脂肪酸。(In order to provide a rubber composition having improved rolling resistance, wet grip performance and abrasion resistance, the present invention comprises 5 to 200 parts by mass of silica, 1 to 20% by mass of a silane coupling agent relative to the mass of the silica, and 1 to 20% by mass of a polyglycerin fatty acid ester derived from a fatty acid having 6 to 24 carbon atoms relative to the mass of the silica, relative to 100 parts by mass of a diene rubber.)

1. A rubber composition comprising 100 parts by mass of a diene rubber, 5 to 200 parts by mass of silica, 1 to 20% by mass of a silane coupling agent relative to the mass of the silica, and 1 to 20% by mass of a polyglycerin fatty acid ester derived from a fatty acid having 6 to 24 carbon atoms relative to the mass of the silica,

the polyglycerin fatty acid ester is represented by the following formula (1),

in the formula (1), R represents a carbon chain derived from the fatty acid, and n represents 0-8.

2. The rubber composition according to claim 1, wherein the silica has a CTAB specific surface area of 150m²More than g.

3. The rubber composition according to claim 2, wherein the silica has a CTAB specific surface area of 180m²More than g.

4. The rubber composition of claim 1, wherein the fatty acid is stearic acid, oleic acid, linoleic acid, or linolenic acid.

5. The rubber composition according to claim 1, wherein in the formula (1), n is 0 or 1.

6. The rubber composition according to claim 5, wherein in the formula (1), n is 0.

7. A pneumatic tire using the rubber composition according to claim 1 for a tread.

Technical Field

The present invention relates to a rubber composition and a pneumatic tire using the same, and more particularly, to a rubber composition which can improve the dispersibility of silica even when the silica having a high specific surface area is blended, and can improve the rolling resistance, wet grip performance and abrasion resistance, and a pneumatic tire using the same.

Background

The 3 performances of rolling resistance, wet grip performance (grip performance on a wet road surface), and abrasion resistance are called magic triangles, and it is required to balance the performance of the magic triangles at a high level when the tire is made to have high performance. However, increasing these 3 properties simultaneously is also understood in the industry to be a rather difficult item. For example, wet grip performance is contrary to wear resistance.

On the other hand, in recent years, with increasing demands for higher performance of tires, a technique of blending silica having a high specific surface area is known. Such silica can improve abrasion resistance, but has a problem that it is extremely difficult to disperse the silica in rubber. In the industry, attempts have been made to develop various silane coupling agents to disperse silica, but silica having a high specific surface area has not been well dispersed in rubber so far.

Patent document 1 below discloses an additive composition for a rubber composition containing silica, which comprises a glycerin fatty acid ester that is an ester of glycerin with 2 or more fatty acids, wherein the largest fatty acid component among the 2 or more fatty acids constituting the glycerin fatty acid ester is 10 to 90% by mass of the total fatty acids, and the glycerin fatty acid ester further contains 50 to 100% by mass of a monoester component.

Further, the following patent document 2 discloses a rubber composition for a sidewall or a base tread, which contains: the rubber component comprises 2 or more diene rubbers and a glycerin fatty acid triester derived from a petroleum external resource, wherein the rubber component comprises at least 1 diene rubber selected from a natural rubber, an epoxidized natural rubber and a butadiene rubber, the glycerin fatty acid triester has an oleic acid content of 45 mass% or more, the total content of the natural rubber and the butadiene rubber in 100 mass% of the rubber component is 50 mass% or more, or the total content of the natural rubber and the epoxidized natural rubber in 100 mass% of the rubber component is 50 mass% or more.

Further, patent document 3 below discloses a rubber composition containing a diene rubber, silica, a silane coupling agent, and a specific glyceride compound, wherein the melting point of the ester compound is 40 ℃ or lower, the content of the silica is 5 to 200 parts by mass per 100 parts by mass of the diene rubber, the content of the silane coupling agent is 1 to 20% by mass per the content of the silica, and the content of the ester compound is 1 to 20% by mass per the content of the silica.

However, the techniques disclosed in patent documents 1 to 3 do not achieve a high level of balance between the magic triangle performance, i.e., 3 performances of rolling resistance, wet grip performance, and abrasion resistance.

Disclosure of Invention

Problems to be solved by the invention

Accordingly, an object of the present invention is to provide a rubber composition which can improve the dispersibility thereof and also improve the rolling resistance, wet grip performance and abrasion resistance even when silica having a high specific surface area is blended, and a pneumatic tire using the rubber composition.

Means for solving the problems

The present inventors have made extensive studies and as a result, have found that the above problems can be solved by blending a specific amount of silica and a specific amount of a silane coupling agent with a diene rubber and further blending a specific amount of a polyglycerol fatty acid ester with the diene rubber, and have completed the present invention.

Namely, the present invention is as follows.

1. A rubber composition comprising 100 parts by mass of a diene rubber, 5 to 200 parts by mass of silica, 1 to 20% by mass of a silane coupling agent relative to the mass of the silica, and 1 to 20% by mass of a polyglycerin fatty acid ester derived from a fatty acid having 6 to 24 carbon atoms relative to the mass of the silica,

the polyglycerin fatty acid ester is represented by the following formula (1).

In the formula (1), R represents a carbon chain derived from the fatty acid, and n represents 0 to 8.

2. The rubber composition according to the above 1, wherein the silica has a CTAB specific surface area of 150m²More than g.

3. The rubber composition according to the above 2, wherein the silica has a CTAB specific surface area of 180m²More than g.

4. The rubber composition according to claim 1, wherein the fatty acid is stearic acid, oleic acid, linoleic acid, or linolenic acid.

5. The rubber composition according to 1, wherein n is 0 or 1 in the formula (1).

6. The rubber composition according to the above 5, wherein n is 0 in the above formula (1).

7. A pneumatic tire comprising a tread and the rubber composition as described in 1 above.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, since a specific amount of silica and a silane coupling agent is blended with a specific amount of a specific polyglycerin fatty acid ester relative to a diene rubber, even if a large amount of silica having a high specific surface area is blended, the dispersibility thereof can be improved, and the rolling resistance, wet grip performance and abrasion resistance can be improved.

Detailed Description

The present invention will be described in further detail below.

(diene rubber)

The diene rubber used in the present invention may be any diene rubber that can be generally blended in a rubber composition, and examples thereof include Natural Rubber (NR), Isoprene Rubber (IR), Butadiene Rubber (BR), styrene-butadiene copolymer rubber (SBR), acrylonitrile-butadiene copolymer rubber (NBR), and the like. These can be used alone, also can be used in combination of more than 2. The molecular weight and microstructure thereof are not particularly limited, and may be modified at the end by amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl or the like, or may be epoxidized.

Among these diene rubbers, SBR and BR are preferable from the viewpoint of the effect of the present invention.

(silica)

The silica used in the present invention preferably has a CTAB specific surface area of 150m²More than g. In the present invention, even when such silica having a high specific surface area is blended in a rubber, good dispersion can be achieved. In addition, in the present invention, even if it has a CTAB specific surface area of 180m²A ratio of more than g, in particular 200m²The silica having an ultrahigh specific surface area of the above-mentioned/g can be dispersed in the rubber well.

The CTAB specific surface area of the silica is furthermore determined in accordance with ISO 5794/1.

(silane coupling agent)

The silane coupling agent used in the present invention is not particularly limited, but is preferably a sulfur-containing silane coupling agent, and examples thereof include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) disulfide, 3-trimethoxysilylpropylbenzothiazoletetrasulfide, γ -mercaptopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, and the like. The silane coupling agent may be used in combination of 1 or 2 or more.

(polyglycerin fatty acid ester)

The polyglycerin fatty acid ester used in the present invention is an ester derived from a fatty acid having 6 to 24 carbon atoms.

Specific examples of the fatty acid include straight-chain fatty acids such as caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, oleic acid, arachic acid, behenic acid, and lignoceric acid.

The polyglycerin fatty acid ester may be used in 1 kind, or 2 or more kinds may be used in combination.

In addition, the fatty acid is preferably stearic acid, oleic acid, linoleic acid, or linolenic acid, from the viewpoint of further improving rolling resistance, wet grip performance, and abrasion resistance at the same time.

The polyglycerin fatty acid ester used in the present invention is such that — OH groups derived from glycerin are adsorbed on silanol groups on the surface of silica, and repeating units of glycerin enter pores of aggregates of silica having a particularly high specific surface area, and are liable to stay, thereby contributing to dispersibility of silica in rubber. This can improve rolling resistance, wet grip performance, and wear resistance at the same time. In addition, this effect is an effect that the monoglyceride cannot exert.

In addition, the polyglycerin fatty acid ester used in the present invention is preferably a monofatty acid ester represented by the following formula (1) from the viewpoint of further improving rolling resistance, wet grip performance and abrasion resistance at the same time.

In the formula (1), R represents a carbon chain derived from the fatty acid, and n represents 0 to 8, preferably 0 to 3, and particularly preferably 0 or 1.

In addition, the rubber composition described in patent document 3 uses a glyceride compound in which secondary hydroxyl groups of polyglycerin are selectively esterified. However, even when the glyceride compound described in patent document 3 is used in place of the monofatty acid ester represented by formula (1) of the present invention, the above-mentioned effects cannot be exhibited, and the dispersibility, rolling resistance, wet grip performance and abrasion resistance of the silica having a high specific surface area, which are the effects of the present invention, cannot be improved at the same time.

The polyglycerin fatty acid ester used in the present invention is commercially available, and examples of the monofatty acid ester represented by formula (1) include DS100A (diglycerin monostearate), DO100V (diglycerin monooleate), S71D (diglycerin stearate), ポエム J-4081V (tetraglycerol stearate), J-0021 (decaglycerol laurate), J-0081HV (decaglycerol stearate), J-0381V (decaglycerol oleate) manufactured by Rizhi ビタミン K.

(compounding ratio of rubber composition)

The rubber composition is characterized by comprising 5-200 parts by mass of silica, 1-20% by mass of a silane coupling agent and 1-20% by mass of a polyglycerin fatty acid ester, wherein the polyglycerin fatty acid ester is derived from a fatty acid having 6-24 carbon atoms, and the amount of the silane coupling agent is 1-20% by mass of the silica, based on 100 parts by mass of a diene rubber.

If the amount of silica is less than 5 parts by mass, the amount is too small to obtain the effects of the present invention. On the other hand, if it exceeds 200 parts by mass, the dispersibility and rolling resistance of the silica are deteriorated.

If the amount of the silane coupling agent blended is less than 1 mass% based on the mass of silica, the amount blended is too small to exhibit the effects of the present invention. Conversely, if it exceeds 20% by mass, the processability and elongation at break are deteriorated.

If the amount of the polyglycerin fatty acid ester blended is less than 1 mass% based on the mass of the silica, the effect of the present invention cannot be exerted because the blended amount is too small. On the other hand, if it exceeds 20 mass%, the wear resistance is deteriorated.

In the rubber composition of the present invention, the amount of silica is preferably 30 to 200 parts by mass per 100 parts by mass of the diene rubber.

The amount of the silane coupling agent is preferably 3 to 20% by mass based on the mass of the silica.

The amount of polyglycerol fatty acid ester is preferably 2 to 20% by mass based on the mass of silica.

(other Components)

In the rubber composition of the present invention, a vulcanizing agent or a crosslinking agent may be compounded in addition to the above components; a vulcanization accelerator or a crosslinking accelerator; various fillers such as zinc oxide, carbon black, clay, talc, and calcium carbonate; an anti-aging agent; plasticizers and other various additives generally incorporated in rubber compositions, and such additives can be kneaded by a general method to prepare a composition and used for vulcanization or crosslinking. The amount of these additives may be any conventional amount as long as the object of the present invention is not impaired.

The rubber composition of the present invention is suitable for producing a pneumatic tire according to a conventional method for producing a pneumatic tire, and is particularly suitable for a tread.