JP2005082620A - Rubber composition for tire tread - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition which has excellent productivity and excellent performance on ice and is suitable for the treads of studless tires. <P>SOLUTION: This rubber composition for the tire treads comprises (i) a master batch obtained by preliminarily kneading 100 pts. wt. of a rubber comprising 50 to 90 pts. wt. of natural rubber (NR) and/or polyisoprene rubber (IR) and 10 to 50 pts. wt. of polybutadiene rubber (BR) with 50 to 200 pts. wt. of thermally expanding microcapsules at a temperature of ≤90°C and (ii) a dienic rubber, wherein the master batch is compounded in such an amount that the amount of the thermally expanding microcapsules is 1 to 15 pts. wt. per 100 pts. wt. of the total rubber amount. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a rubber composition, and more particularly, to a rubber composition for a tire in which the on-ice performance of a rubber composition having high on-ice performance blended with thermally expandable microcapsules is further improved.

  It is known to mix thermally expandable microcapsules in a rubber composition for the purpose of improving the performance on ice of a studless tire (see, for example, Patent Document 1). However, according to the conventional proposal, there is a problem that it is difficult to quickly incorporate and disperse the heat-expandable microcapsules into the rubber, it takes time for mixing, and the productivity is inferior, and the heat expansion compounded during the mixing process. There is a problem that the expandable microcapsule is crushed and the performance of the target thermally expandable microcapsule is not exhibited 100%.

JP 11-35736 A

  Accordingly, an object of the present invention is to provide a rubber composition suitable for use as a tread for a studless tire that solves the above-described problems of the prior art and has excellent productivity and excellent performance on ice.

  According to the present invention, (i) 100 parts by weight of a rubber component consisting of 50 to 90 parts by weight of natural rubber (NR) and / or polyisoprene rubber (IR) and 10 to 50 parts by weight of polybutadiene rubber (BR), and thermal expansion A master batch obtained by kneading 50 to 200 parts by weight of a microcapsule in advance at a temperature of 90 ° C. or less and (ii) a diene rubber, and the blending amount of the master batch is a total rubber There is provided a rubber composition for a tire tread in which the amount of thermally expandable microcapsules is 1 to 15 parts by weight per 100 parts by weight.

  According to the present invention, the incorporation of the heat-expandable microcapsules into the rubber composition is remarkably improved, and sufficient dispersibility is obtained in a short time. As a result, the heat-expandable microcapsules at the time of mixing the rubber composition Can be prevented, and the performance on ice is remarkably improved.

  As described below, in the present invention, a large amount of thermally expandable microcapsules are kneaded in advance with a specific rubber to produce an integrated master batch rubber, and the thermally expandable microcapsules are blended using this master batch rubber. Since the manufactured tire tread rubber composition is produced, the above-mentioned problems of the prior art can be solved. Hereinafter, the present invention will be described in more detail.

  The rubber component blended in the master batch of the rubber composition according to the present invention includes various natural rubbers (NR) and / or various polyisoprene rubbers (IR) 50 to 90 that are conventionally used for tires. Parts by weight, preferably 60 to 80 parts by weight, and various polybutadiene rubbers (BR) 10 to 50 parts by weight, preferably 20 to 40 parts by weight (a total of 100 parts by weight of both). If the amount is too small (that is, if the amount of BR is too large), it is not preferable because mixing becomes difficult. Conversely, if the amount of BR is too small (that is, if the amount of NR and / or IR is too large), heat This is not preferable because the expandable microcapsules are easily broken.

According to the present invention, first, natural rubber (NR) and / or polyisoprene (IR) and polybutadiene rubber (BR) are mixed at a weight ratio of NR (and / or IR) / BR of 50 to 90 /, as described above. 10 to 50, preferably 60 to 80/20 to 40, mixed in an amount of 50 to 200 parts by weight, preferably 75 to 125 parts by weight, based on 100 parts by weight of the total rubber. Mix the parts to obtain a master batch. The blending conditions are 90 ° C. or lower, preferably 80 ° C. or lower in consideration of the expansion start temperature of the thermally expandable microcapsules, etc., for example, 130 sec ⁻¹ or lower, preferably 10 ° C. using a closed mixer or kneader. It is desirable to obtain a masterbatch by mixing at a shear rate of ˜100 sec ⁻¹ . If the mixing temperature is too high, the heat-expandable microcapsules will foam during the production of the masterbatch, which is not preferable, and if the shear rate is too high, the heat-expandable microcapsules may be destroyed. In addition, various oils, processing aids, etc. can be mix | blended suitably at the time of the mixing | blending of a masterbatch.

  In the production of a masterbatch, when a low molecular weight liquid polybutadiene, for example, a polybutadiene containing 20 to 45% by weight of a low molecular weight polybutadiene having a weight average molecular weight of 10,000 to 50,000 in the total polybutadiene (BR) is used, It is preferable because the uptake and dispersion are improved. As such a polybutadiene (BR), commercially available BRX5000 (manufactured by Nippon Zeon Co., Ltd., BR containing 30% by weight of a low molecular weight component of Mw20,000) can be used.

  The thermally expandable microcapsule used in the present invention is blended in an amount of 1 to 15 parts by weight, preferably 3 to 10 parts by weight, based on 100 parts by weight of the diene rubber in the final rubber composition. If the blending amount is too small, the desired effect of the present invention cannot be obtained. Conversely, if the blending amount is too large, the wear resistance of the rubber composition is remarkably lowered. The heat-expandable microcapsule used in the present invention is a heat-expandable thermoplastic resin particle in which a liquid or solid that generates a gas by vaporization, decomposition, or chemical reaction by heat is encapsulated in a thermoplastic resin, and the particle is expanded. By heating and expanding at a temperature equal to or higher than the starting temperature, usually 130 to 190 ° C., gas-encapsulated thermoplastic resin particles (hollow polymer) in which gas is encapsulated in the outer shell made of the thermoplastic resin are obtained.

Examples of liquids or solids that generate gas upon vaporization, decomposition, or chemical reaction by heat include hydrocarbons such as n-pentane, isopentane, neopentane, butane, isobutane, hexane, petroleum ether, and methyl chloride. , Liquids such as chlorinated hydrocarbons such as methylene chloride, dichloroethylene, trichloroethane, trichloroethylene, or azodicarbonamide, dinitrosopentamethylenetetramine, azobisisobutyronitrile, toluenesulfonylhydrazide derivatives, aromatic succinylhydrazide derivatives However, the present invention is not limited to these.
Examples of the thermoplastic resin in which a liquid or solid that generates a gas upon vaporization, decomposition, or chemical reaction is encapsulated include, for example, a polymer of acrylonitrile or methacrylonitrile, or acrylonitrile or methacrylonitrile and others. However, the present invention is not limited to these. Examples of the comonomers include, but are not limited to, vinyl halides, vinylidene halides, styrene monomers, acrylate monomers or methacrylate monomers, vinyl acetate, butadiene, vinyl pyridine, chloroprene, and other monomers. It is not something.

  The thermoplastic resin is preferably not crosslinked, but, for example, divinylbenzene, ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol diacrylate, as long as the properties as a thermoplastic resin are not impaired. Triethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, 1,3-butylene glycol diacrylate, 1,3-butylene glycol dimethacrylate, allyl acrylate, allyl methacrylate, triacryl formal, triallyl isocyanurate Such a comonomer may be introduced into the thermoplastic resin to partially crosslink the thermoplastic resin.

  The particle size of the thermally expandable microcapsule is not particularly limited, but is preferably 5 to 300 μm before expansion. As such a thermally expandable microcapsule, for example, the product name “Expancel 091DU-80” or “Expancel 092DU-120” is currently available from EXPANCEL, Sweden, or from Matsumoto Yushi Co., Ltd. The name “Matsumoto Microsphere F-85” or “Matsumoto Microsphere F-100” is available.

  In the rubber composition according to the present invention, a diene rubber is compounded as the second component. As such a diene rubber, a diene rubber generally used for tires and other rubbers has been conventionally used. Specifically, for example, various natural rubbers (NR), various polyisoprene rubbers (IR), various styrene-butadiene copolymer rubbers (SBR), various polybutadiene rubbers (BR), various acrylonitrile-butadiene copolymers. Examples include diene rubbers such as polymer rubber (NBR), various ethylene-propylene-diene copolymer rubbers (EPDM), various chloroprene rubbers (CR), various butyl rubbers (IIR), etc. Can be used as a blend.

  In addition to the above-described essential components, the rubber composition according to the present invention includes a reinforcing agent (filler) such as carbon black and silica, a vulcanization or crosslinking agent, a vulcanization or crosslinking accelerator, various oils, an anti-aging agent, General-purpose various additives compounded for tires such as plasticizers and other general rubbers can be blended, and these blends are kneaded and vulcanized by a general method to form a composition, vulcanized or Can be used to crosslink. As long as the amount of these additives is not contrary to the object of the present invention, the conventional general amounts can be used.

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

Examples 1-2 and Comparative Examples 1-2
1) Manufacture of masterbatch According to the blending weight part shown in Table I, natural rubber (NR) and polybutadiene rubber (BR) or low molecular weight component-containing polybutadiene (BRX5000) and thermally expandable microcapsules were used in a 1.8 l Banbury mixer. A master batch was manufactured by kneading under a kneading condition of a rotor rotational speed of 15-30 rpm, a filling rate of 65-75%, and a temperature of 60-80 ° C.

Table I footnote * 1: TSR20 (natural rubber)
* 2: BR1220 manufactured by Nippon Zeon Co., Ltd.
* 3: BRX5000 manufactured by Nippon Zeon Co., Ltd. (low molecular weight component: Mw 20,000, high molecular weight component: Mw 740,000, blend ratio 30%)
* 4: Microsphere F100 manufactured by Matsumoto Yushi Seiyaku Co., Ltd.

2) Manufacture of rubber composition sample According to the formulation (parts by weight) shown in Table II, the components except for sulfur and vulcanization accelerator, masterbatch, and thermally expandable microcapsule were mixed with a 1.8 liter closed mixer. Kneaded for 5 minutes and released when the temperature reached 165 ± 5 ° C. To this rubber mixture, sulfur and a vulcanization accelerator shown in Table II, a masterbatch, and a thermally expandable microcapsule were added and kneaded with an 8-inch open roll to obtain a rubber composition.

Table II footnote * 1: TSR20 (natural rubber)
* 2: BR1220 manufactured by Nippon Zeon Co., Ltd.
* 3: BRX5000 manufactured by Nippon Zeon Co., Ltd. (low molecular weight component: Mw 20,000, high molecular weight component: Mw 740,000, blend ratio 30%)
* 4: See Table I (all contain 10 parts by weight of thermally expandable microcapsules)
* 5: Microsphere F100 manufactured by Matsumoto Yushi Seiyaku Co., Ltd.
* 6: Show Black N234 manufactured by Showa Cabot Co., Ltd.
* 7: Aroma oil manufactured by Showa Shell Co., Ltd. * 8: Santoflex 6PPD manufactured by Flexis Co., Ltd.
* 9: Three types of zinc oxide manufactured by Shodo Chemical Industry Co., Ltd. * 10: Tungsten stearate manufactured by Nippon Oil & Fats Co., Ltd. * 11: Sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. * 12: CBS manufactured by Flexis Co., Ltd.

The behavior in the compounding process of the rubber composition and the properties of the obtained rubber composition were evaluated as follows.
Thermally expandable microcapsule dispersibility: The rubber sheet cross section after open roll mixing was visually observed. 1 to 5 is the worst and 5 is the best.
Mixing time: The time for which the thermally expandable microcapsules are taken into the rubber during open roll mixing.

Specific gravity: Measured according to JIS K0061.
On-ice braking: Test tires of size 185 / 65R14 were prepared using each formulation as a cap tread and subjected to a braking test. In the braking test method, four test tires were mounted on a 1800 cc passenger car, and the braking distance from an initial speed of 40 km / h was measured on an ice plate road surface at an outside temperature of -5 ° C. The value is shown as an index in Table 1 with Comparative Example 1 being 100, and the larger the value, the better the performance on ice.

  As described above, the rubber composition according to the present invention is suitable for use as a tire tread of a pneumatic tire, particularly as a tread of a studless tire because it has excellent productivity and significantly improves performance on ice.

Claims (1)

  (I) 100 parts by weight of rubber comprising 50 to 90 parts by weight of natural rubber (NR) and / or polyisoprene rubber (IR) and 10 to 50 parts by weight of polybutadiene rubber (BR), and thermally expandable microcapsules 50 to 200 A master batch obtained by kneading in advance at a temperature of 90 ° C. or less, and (ii) a diene rubber, and the blending amount of the master batch is 100 parts by weight of the total rubber content. The rubber composition for tire treads is such that the amount of thermally expandable microcapsules is 1 to 15 parts by weight.