JP2009138094A - Rubber composition for tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition for a tire suppressing heat generation during travel while maintaining workability, hardness, and breaking elongation balanced in a high level. <P>SOLUTION: The rubber composition includes 100 pts.wt. of diene rubber, 1-20 pts.wt. of liquid rubber having a functional group, 10-70 pts.wt. of an inorganic filler, and 10-60 pts.wt. of carbon black. The total amount of the inorganic filler and the carbon black is 35-80 pts.wt. while a nitrogen adsorption specific surface area of the carbon black is 30-90 m<SP>2</SP>/g. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a tire rubber composition, and more particularly to a tire rubber composition capable of suppressing heat generation during running while maintaining processability, hardness, and elongation at break.

  In recent years, from the viewpoint of protecting the global environment, environmental considerations are also required for pneumatic tires, and specifically, a performance that improves fuel consumption is desired. In order to improve fuel economy, it is only necessary to produce a pneumatic tire using a rubber composition that can suppress heat generation during traveling, and in particular, by reducing the heat generation in the side tread portion where repeated deformation during traveling is large. It is thought that fuel economy can be improved.

  However, if the particle size of the carbon black compounded in the rubber composition is increased, the blending amount is reduced, or the vulcanizing compound is increased in order to suppress the heat generation, the heat generation is suppressed. There was a problem that hardness and elongation at break deteriorated. In addition, when an inorganic filler is added, heat generation is suppressed, but the Mooney viscosity of the rubber composition is increased, and there is a problem that workability and elongation at break are deteriorated (for example, see Patent Document 1).

Therefore, as a tire rubber composition, it is significant to achieve improved fuel efficiency by achieving low heat build-up without degrading performance such as processability, hardness, elongation at break and the like in a high level. It has become an issue.
JP-A-10-87895

  An object of the present invention is to provide a rubber composition for a tire that can suppress heat generation during running while maintaining workability, hardness, and elongation at break in a high dimension.

The rubber composition for a tire according to the present invention that achieves the above object comprises 1 to 20 parts by weight of a liquid rubber having a functional group, 10 to 70 parts by weight of an inorganic filler, and 10 to 60 parts of carbon black based on 100 parts by weight of a diene rubber. While containing a weight part, the total amount of the said inorganic filler and carbon black is 35-80 weight part, The nitrogen adsorption specific surface area of the said carbon black is 30-90 m < ² > / g, It is characterized by the above-mentioned.

  The inorganic filler may be clay or calcium carbonate, the liquid rubber having a functional group may be a liquid rubber having a carboxyl group, an acid anhydride group, or a hydroxyl group, and the diene rubber may be It is preferable to contain 50% by weight or more of butadiene rubber. This tire rubber composition is suitable for constituting a side tread portion of a pneumatic tire.

The rubber composition for tires of the present invention contains 10 to 70 parts by weight of an inorganic filler and 10 to 60 parts by weight of carbon black having a nitrogen adsorption specific surface area of 30 to 90 m ² / g with respect to 100 parts by weight of a diene rubber. In addition, since the total amount of the inorganic filler and carbon black is 35 to 80 parts by weight, the exothermic property of the rubber composition is reduced, and 1 to 20 parts by weight of a liquid rubber having a functional group is contained. Therefore, the exothermic property can be further reduced, and at the same time, the processability (Mooney viscosity), hardness, and elongation at break of the rubber composition can be balanced and maintained in a high dimension.

  In the tire rubber composition of the present invention, the diene rubber is not particularly limited, and natural rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, which are usually used in the tire rubber composition. And butyl rubber. These diene rubbers can be used alone or as any blend. In addition, the diene rubber preferably contains 50% by weight or more of butadiene rubber. Further, the diene rubber further reduces the heat buildup and at the same time improves the fatigue resistance, so that the rubber composition is suitable for the side tread.

  Examples of the liquid rubber serving as the base of the liquid rubber having a functional group include isoprene rubber, butadiene rubber, styrene-butadiene rubber, ethylene propylene rubber, nitrile rubber, chloroprene rubber, acrylic rubber, epichlorohydrin rubber, and the like. it can. Of these, isoprene rubber and butadiene rubber are preferable, and they are excellent in compatibility with the above-described diene rubber, and are suitable as a rubber composition for tires.

  The functional group is not particularly limited, but carboxyl group, acid anhydride group, carbonyl group, hydroxyl group, halogen group, epoxy group, amino group, aldehyde group, N-methylol group, chloromethyl group, isocyanate group. And thiol groups. Of these, a carboxyl group, an acid anhydride group, and a hydroxyl group are preferable. Since the liquid rubber having such a functional group is excellent in affinity for the inorganic filler, it is possible to reduce exothermic property and maintain and improve elongation at break.

  The number of functional groups per molecule of liquid rubber is preferably 2-10. If the number of functional groups is too small, affinity for the inorganic filler cannot be obtained, and conversely if too large, the workability during mixing may be deteriorated. The number average molecular weight of the liquid rubber having a functional group is preferably 1000 to 50000, and more preferably 5000 to 30000. If the number average molecular weight is less than 1000, the exothermic reduction effect is weakened. Conversely, if the number average molecular weight exceeds 50000, the Mooney viscosity of the rubber composition increases and the processability deteriorates.

  Examples of the liquid rubber having such a functional group include a liquid isoprene rubber having a carboxyl group (Kuraray LIR-410), an acid anhydride group having a liquid isoprene rubber (Kuraray LIR-403), and a liquid having a hydroxyl group. Butadiene rubber (poly-bd R-45HT manufactured by Idemitsu Chemical Co., Ltd.) or the like can be suitably used.

  In this invention, the compounding quantity of the liquid rubber which has a functional group is 1-20 weight part with respect to 100 weight part of diene rubbers, Preferably it is good to set it as 5-15 weight part. When the blending amount is less than 1 part by weight, sufficient affinity cannot be obtained when the inorganic filler is blended, and the elongation at break is lowered, and the Mooney viscosity of the rubber composition is increased and the processability is deteriorated. If it exceeds 20 parts by weight, the processability at the time of mixing deteriorates.

  As the inorganic filler used in the present invention, those usually used for tire rubber compositions can be used, and examples thereof include clay, calcium carbonate, magnesium carbonate, diatomaceous earth, talc, alumina, mica and the like. it can. Among these, clay and calcium carbonate are preferable, and clay is particularly preferable.

  The compounding amount of the inorganic filler is 10 to 70 parts by weight, preferably 20 to 50 parts by weight, with respect to 100 parts by weight of the diene rubber. When the inorganic filler is less than 10 parts by weight, the low exothermic property cannot be obtained sufficiently. If the inorganic filler exceeds 70 parts by weight, the processability at the time of mixing deteriorates.

The carbon black used in the present invention has a nitrogen adsorption specific surface area of 30 to 90 m ² / g, preferably 40 to 80 m ² / g. When the nitrogen adsorption specific surface area is less than 30 m ² / g, a sufficient reinforcing effect cannot be obtained, and the hardness of the rubber composition is lowered.
become. When the nitrogen adsorption specific surface area exceeds 90 m ² / g, the exothermic property deteriorates and the workability also decreases. The nitrogen adsorption specific surface area shall be measured according to JIS K6217.

  The compounding amount of carbon black is 10 to 60 parts by weight, preferably 20 to 40 parts by weight, based on 100 parts by weight of the diene rubber. When the amount of carbon black is less than 10 parts by weight, a large amount of inorganic filler is required, resulting in poor processability during mixing. When the carbon black exceeds 60 parts by weight, the exothermic property is deteriorated.

  The total amount of the inorganic filler and carbon black is 35 to 80 parts by weight, preferably 40 to 70 parts by weight, based on 100 parts by weight of the diene rubber. When the total amount is less than 35 parts by weight, sufficient strength cannot be obtained for the rubber. When the total amount exceeds 80 parts by weight, the workability during mixing deteriorates and the exothermic property deteriorates.

  Various additives commonly used in rubber compositions such as vulcanization or cross-linking agents, anti-aging agents, and plasticizers can be blended with the rubber composition for tires. And kneaded into a rubber composition which can be used for vulcanization or crosslinking. The blending amounts of these additives may be conventional conventional blending amounts as long as the object of the present invention is not adversely affected.

  The rubber composition for tires of the present invention can be applied to casing compounds such as tread parts, side tread parts and bead parts of pneumatic tires, various coated rubbers and the like. In particular, when used as a side tread portion, it is possible to obtain a pneumatic tire that exhibits the most excellent effects, suppresses heat generation during traveling, and has excellent fuel efficiency.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

  Of 21 types of rubber compositions (Examples 1 to 11, standard examples and Comparative Examples 1 to 9) prepared by the method shown below, a part thereof was subjected to the Mooney viscosity test, and the remainder was exothermic (tan δ). For the tests of rubber hardness and elongation at break, test pieces were prepared by vulcanization at 150 ° C. for 30 minutes in respective molds, and each test was performed.

Preparation of Rubber Composition 21 types of rubber compositions (Examples 1 to 11, Standard Examples and Comparative Examples 1 to 9) having the formulations shown in Tables 1 and 2 were weighed, except for sulfur and vulcanization accelerators, respectively. Then, it was mixed with a Banbury type mixer at a temperature of 60 ° C. and a rotation speed of 60 rpm, and kneaded to a temperature of 160 ° C. and discharged. Each rubber composition was obtained by using the obtained master batch for an open roll, adding sulfur and a vulcanization accelerator, and turning left and right 10 times.

Mooney viscosity (ML _{1 + 4} )
In accordance with JIS K6300, the obtained rubber composition was subjected to a Mooney viscometer using an L-shaped rotor (38.1 mm system, 5.5 mm thickness), preheating time 1 minute, rotor rotation time 4 minutes, 100 The measurement was performed under the conditions of 2 ° C. and ° C. The obtained results are shown in Tables 1 and 2 as an index with the value of the standard example as 100. A smaller index means a lower viscosity and better processability.

Exothermic (dynamic viscoelasticity, tan δ)
Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho, dynamic viscoelasticity was measured at an initial strain of 10%, an amplitude of ± 2%, and a frequency of 20 Hz, and tan δ at a temperature of 60 ° C. was calculated. The obtained results are shown in Tables 1 and 2 as an index with the value of the standard example as 100. The smaller the index, the smaller the exotherm and the better.

Rubber hardness Using the obtained test piece, it was measured at a temperature of 25 ° C. with a durometer type A according to JIS K6253. The obtained results are shown in Tables 1 and 2 as an index with the value of the standard example as 100. The larger this index, the higher the rubber hardness.

Elongation at break:
The obtained test piece was punched into a JIS No. 3 dumbbell according to JIS K6251 and subjected to a tensile test at a tensile speed of 500 mm / min to measure the elongation at break. The obtained results are shown in Table 1 as an index with the value of the standard example being 100. It means that it is excellent in elongation at break, so that this index | exponent is large.

The types of raw materials used in Tables 1 and 2 are shown below.
Natural rubber: TSR20
Butadiene rubber: Nippon BR 1220 manufactured by Nippon Zeon
CB-1: Carbon black, Niteron # 10IN (Nitrogen carbon specific surface area 40 m ² / g) manufactured by Nippon Kayaku Carbon
CB-2: Carbon black, Niteron # 200IN (Nitrogen adsorption specific surface area 74 m ² / g) manufactured by Nippon Kasei Carbon Co., Ltd.
CB-3: Carbon black, THAI CARBON BLACK Co. THAIBLACK N339 (nitrogen adsorption specific surface area 84m ² / g)
CB-4: Carbon black, Cabot Japan Show Black N234 (nitrogen adsorption specific surface area 110 m ² / g)
Clay: T clay made by Nippon Talc Co., Ltd .: Carbon dioxide made by Maruo Calcium Co., Ltd. MSK-V
Liquid rubber-1: liquid isoprene rubber having an acid anhydride group, LIR403 (number average molecular weight of about 34,000) manufactured by Kuraray Co., Ltd.
Liquid rubber-2: Liquid isoprene rubber having a carboxyl group, LIR410 manufactured by Kuraray Co., Ltd. (number average molecular weight of about 30000)
Liquid rubber-3: Liquid butadiene rubber having a hydroxyl group, poly-bd R-45H (number average molecular weight of about 3000) manufactured by Idemitsu Chemical Co., Ltd.
Oil: Diana Process Oil AH-20 manufactured by Idemitsu Kosan Co., Ltd.
Anti-aging agent: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd.
Zinc flower: Zinc oxide 3 types manufactured by Shodo Chemical Industry Co., Ltd. Stearic acid: Beads manufactured by Nippon Oil & Fats Co., Ltd.

Claims (5)

It contains 1 to 20 parts by weight of a liquid rubber having a functional group, 10 to 70 parts by weight of an inorganic filler, and 10 to 60 parts by weight of carbon black with respect to 100 parts by weight of a diene rubber, and the inorganic filler and carbon black The tire rubber composition wherein the total amount of is 35 to 80 parts by weight, and the nitrogen adsorption specific surface area of the carbon black is 30 to 90 m ² / g.   The tire rubber composition according to claim 1, wherein the inorganic filler is clay or calcium carbonate.   The tire rubber composition according to claim 1 or 2, wherein the liquid rubber having a functional group is a liquid rubber having a carboxyl group, an acid anhydride group or a hydroxyl group.   The tire rubber composition according to claim 1, 2 or 3, wherein the diene rubber contains 50% by weight or more of butadiene rubber.   The pneumatic tire which has a side tread part which consists of a rubber composition for tires in any one of Claims 1-4.