JP2007217458A - Rubber composition for roll forming, and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition that gives a sheet-like cured product exhibiting markedly enhanced heat dissipation properties in the thickness direction without increasing the compounded amount of a fibrous filler when shaped into a sheet by roll forming, and a pneumatic tire comprised of the rubber composition as the constituent of the tire that exhibits enhanced heat dissipation properties in the direction rectangularly crossing the rotational circumferential direction of the tire and excellent durability without deteriorating mechanical properties such as strength or elongation as fundamentals of a rubber. <P>SOLUTION: The rubber composition for roll forming comprises a diene rubber, sulfur and a fibrous filler, where two kinds of fibrous fillers, one having a high aspect ratio and the other having a low aspect ratio, are jointly used as the fibrous filler. The pneumatic tire is obtained by roll-forming the rubber composition, arranging the thus-obtained formed product so that the rolling direction in the roll forming is the rotational circumferential direction of the pneumatic tire, and curing the formed product. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a roll-forming rubber composition capable of improving heat dissipation performance in a direction perpendicular to the circumferential direction of the tire in a pneumatic tire, and a pneumatic tire formed using the rubber composition.

  The heat radiation when using a pneumatic tire is required to be higher than the heat radiation in the circumferential direction of the rotating tire in terms of the heat radiation in the direction orthogonal to the tire circumferential direction (for example, the radial direction and width direction of the tire). In the case of a pneumatic tire, a tire is formed by laminating a rubber composition molded into a sheet shape by roll molding, but the fibrous filler blended to give the rubber heat dissipation characteristics is changed in the fiber length direction by the roll. The tire is formed by laminating the rubber composition so that it is oriented in the roll direction and the roll direction is the circumferential direction of the tire. For this reason, the heat dissipation of the tire is generally dominant in the rotational circumferential direction of the tire in which the fibrous filler is oriented, rather than the direction orthogonal to the rotational circumferential direction of the tire where higher characteristics are required.

  In this case, in order to give higher heat dissipation in a direction orthogonal to the circumferential direction of the tire, the amount of fibrous filler must be increased. However, the increase in the amount of fibrous filler constitutes the tire. There is a limit because other physical properties required for rubber, for example, mechanical properties related to the essence of the tire, such as strength and elongation, are reduced.

  The prior art document information related to the present invention includes the following.

JP 2004-203350 A

  The present invention has been made in view of the above circumstances, and improves the heat dissipation performance in the direction orthogonal to the rotational circumferential direction of the tire, which is important in a pneumatic tire, without reducing mechanical properties as rubber, such as strength and elongation. An object of the present invention is to provide a rubber composition for roll molding that can be used and a pneumatic tire formed using the rubber composition.

  As a result of diligent study to achieve the above-mentioned object, the present inventors have found that a rubber composition comprising a diene rubber, sulfur and a fibrous filler, the fibrous filler is a high aspect ratio filler and a low aspect ratio. When this rubber composition is roll-molded into, for example, a sheet-like molded body by blending two types together with a filler, the direction orthogonal to the roll direction in the roll molding of the cured product of the molded body The heat dissipation is improved without increasing the blending amount of the fibrous filler, and as a result, high heat dissipation can be obtained without degrading the basic mechanical properties as rubber such as strength and elongation. If the rubber composition is a rubber constituting the tire, the heat dissipation characteristics in the direction perpendicular to the rotation circumferential direction of the tire can be improved. Found that it is possible to obtain a pneumatic tire excellent in durability, the present invention has been accomplished.

Accordingly, the present invention provides the following rubber composition for roll molding and a pneumatic tire.
[Claim 1] A rubber composition comprising a diene rubber, sulfur and a fibrous filler, wherein the fibrous filler is a combination of a high aspect ratio filler and a low aspect ratio filler. A rubber composition for roll forming characterized by comprising:
[Claim 2] The roll molding according to claim 1, wherein the ratio of the aspect ratio of the high aspect ratio filler to the aspect ratio of the low aspect ratio filler is 1.5: 1 to 100: 1. Rubber composition.
[Claim 3] The rubber composition for roll molding according to claim 1 or 2, wherein 10 to 90 parts by mass of the low aspect ratio filler is used in combination with 100 parts by mass of the high aspect ratio filler.
[Claim 4] The roll molding according to any one of claims 1 to 3, wherein a blending ratio of the fibrous filler is 0.01 to 100 parts by mass with respect to 100 parts by mass of the diene rubber. Rubber composition.
[Claim 5] The rubber composition for roll forming according to any one of claims 1 to 4, wherein the fibrous filler is vapor grown carbon fiber.
[Claim 6] A pneumatic tire formed using the rubber composition according to any one of claims 1 to 5, wherein the rubber composition is molded by roll molding, and a molded body obtained is obtained. The pneumatic tire is characterized in that the roll direction in the roll forming is disposed as the rotational circumferential direction of the pneumatic tire and cured.

  In the cured product obtained by roll molding the rubber composition of the present invention, the heat dissipation in the direction perpendicular to the roll direction in the roll molding is improved without increasing the blending amount of the fibrous filler. As a result, high heat dissipation can be obtained without degrading the basic mechanical properties of rubber such as strength and elongation. Further, if this rubber composition is a rubber constituting a tire, the heat dissipation characteristics in the direction perpendicular to the rotational circumferential direction of the tire can be improved, and a pneumatic tire excellent in heat dissipation and consequently durability can be obtained. It is done.

Hereinafter, the present invention will be described in more detail.
The rubber composition for roll molding of the present invention is a rubber composition obtained by blending a diene rubber, sulfur and a fibrous filler. As the fibrous filler, 2 of a high aspect ratio filler and a low aspect ratio filler. It is a combination of seeds. The pneumatic tire of the present invention is a pneumatic tire formed using a rubber composition, the rubber composition is molded by roll molding, and the resulting molded body has a roll direction in the roll molding as air. It is arranged as the rotational circumferential direction of the entering tire and cured.

  When the rubber composition is molded by roll molding, the fibrous filler is oriented in the longitudinal direction (fiber length direction) of the fibrous filler along the roll direction in a sheet or the like obtained by roll molding. Therefore, the fibrous filler is oriented with a predetermined interval in the direction orthogonal to the roll direction. However, if the amount of the fibrous filler in the rubber composition is the same, two kinds of fibrous fillers having different aspect ratios. That is, when a high aspect ratio filler and a low aspect ratio filler are used in combination, adjacent to the direction perpendicular to the longitudinal direction (roll direction) of the fibrous filler, compared to the case where only the high aspect ratio filler is used. The distance of the fibrous filler to perform can be shortened. Further, the low aspect ratio filler is less likely to be oriented in the above-described direction than the high aspect ratio filler, and is relatively easily oriented at random. For this reason, the heat conduction channel in the direction orthogonal to the roll direction by the fibrous filler is efficiently formed, and the combination of the high aspect ratio filler and the low aspect ratio filler is higher in the direction orthogonal to the roll direction. Thermal conductivity can be obtained.

  Therefore, by arranging and curing the roll molded sheet or the like as the rotational circumferential direction of the pneumatic tire in the roll molding, the direction perpendicular to the rotational circumferential direction of the tire (the tire radial direction, The thermal conductivity in the width direction) can be improved.

  In the rubber composition for roll molding of the present invention, examples of the diene rubber include natural rubber, ethylene / propylene / diene rubber (EPDM), styrene / butadiene copolymer rubber (SBR), butadiene rubber, isoprene rubber, butyl rubber, and halogenated rubber. Examples include butyl rubber, a copolymer of isobutylene and p-halogenated methylstyrene, and acrylonitrile / butadiene copolymer rubber (NBR). These may be used alone or in combination of two or more. Also good. Moreover, as a compounding quantity of sulfur, it is 0.1-10 mass parts normally with respect to 100 mass parts of diene rubbers.

  On the other hand, as the fibrous filler, for example, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon fibers, and the like can be used. In particular, vapor-grown carbon fibers are preferably used. Commercially available products can be used as the vapor growth carbon fiber, and examples thereof include VGCF (manufactured by Showa Denko KK).

  In the present invention, two types of fibrous fillers having different aspect ratios (length / diameter), that is, a high aspect ratio filler and a low aspect ratio filler are used in combination as the fibrous filler. The ratio between the aspect ratio of the high aspect ratio filler and the aspect ratio of the low aspect ratio filler can be increased because the heat dissipation in the direction perpendicular to the tire's circumferential direction of the tire can be particularly improved without impairing the strength and elongation, which are mechanical properties. It is preferable to blend as 1.5: 1 to 100: 1, preferably 1.5: 1 to 20: 1.

  In the case of vapor grown carbon fiber, as such high aspect ratio filler and low aspect ratio filler, VGCF-R (manufactured by Showa Denko) as a high aspect ratio filler and VGCF-H (Showa Denko) as a low aspect ratio filler. (Electric Industries Co., Ltd.) is specifically exemplified.

  On the other hand, the blending amount of the fibrous filler is preferably 0.1 to 100 parts by mass, particularly 1 to 50 parts by mass with respect to 100 parts by mass of the diene rubber. If the blending amount of the fibrous filler is too large, the desired performance is difficult to be exhibited, and workability in mixing, molding, and the like may be deteriorated. If the amount is too small, the desired performance may not be sufficiently obtained.

  According to the conventional method, the rubber composition for roll molding according to the present invention further includes a vulcanizing agent other than sulfur such as an organic sulfur compound, a vulcanization accelerator, and a vulcanization accelerator according to the required physical properties. It is possible to add additives such as auxiliaries, fillers, anti-aging agents, softeners, dispersants and the like within the range of ordinary doses so as not to impair the effects of the present invention.

  Examples of the vulcanization accelerator include CBS (N-cyclohexyl-2-benzothiazylsulfenamide), TBBS (Nt-butyl-2-benzothiazylsulfenamide), TBSI (Nt-butyl- Sulfenamide vulcanization accelerators such as 2-benzothiazylsulfenimide), guanidine vulcanization accelerators such as DPG (diphenylguanidine), and thiuram additions such as tetraoctyl thiuram disulfide and tetrabenzyl thiuram disulfide. Examples thereof include vulcanization accelerators and vulcanization accelerators such as zinc dialkyldithiophosphate.

  Further, from the viewpoint of accelerating vulcanization with sulfur, vulcanization accelerating aids such as zinc white and fatty acids can be blended. The fatty acid may be saturated, unsaturated, linear or branched fatty acid, and is not particularly limited as the carbon number of the fatty acid. For example, the fatty acid has 1 to 30 carbon atoms, preferably 15 to 15 carbon atoms. 30 fatty acids, more specifically naphthenic acid such as cyclohexane acid (cyclohexanecarboxylic acid), alkylcyclopentane having a side chain, hexanoic acid, octanoic acid, decanoic acid (including branched carboxylic acid such as neodecanoic acid), Saturated fatty acids such as dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid (stearic acid), unsaturated fatty acids such as methacrylic acid, oleic acid, linoleic acid, linolenic acid, resin acids such as rosin, tall oil acid, abietic acid, etc. Is mentioned.

  Furthermore, examples of the filler include carbon black, and specific examples include carbon blacks such as SRF, GPF, FEF, HAF, ISAF, SAF, FT, and MT. In addition to carbon black as a filler, inorganic fillers such as white carbon, fine particle magnesium silicate, heavy calcium carbonate, magnesium carbonate, clay, talc, high styrene resin, coumarone indene resin, phenol resin, lignin, Organic fillers such as modified melamine resins and rosin derivatives can also be mentioned.

  When the roll molding rubber composition of the present invention is obtained, there is no particular limitation on the blending method of the above components, and all the component raw materials may be blended and kneaded at once, or divided into two or three stages. Each component may be blended and kneaded. For kneading, a known kneader such as a roll, an internal mixer or a Banbury rotor can be used.

  In addition, as conditions for vulcanizing the rubber composition for roll molding obtained by blending the respective components as described above, vulcanization conditions for 5 to 80 minutes can be generally employed at 130 to 180 ° C.

  The rubber composition for roll molding of the present invention is suitable as a rubber composition for forming a tire, and in particular, a tire tread, a base, a sidewall, an inner liner, a rubber chafer, a stiffener, and a bead filler. It is suitable as a rubber composition for forming a part such as.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Example 1, Comparative Examples 1 and 2]
Each raw material component was blended according to the blending shown in Table 1, and kneaded using a lab plast mill (manufactured by Toyo Seiki Co., Ltd.) to obtain an unvulcanized rubber composition. For the cured product obtained by molding and curing this rubber composition by roll molding, the thermal conductivity in the direction perpendicular to the roll direction (in this case, the thickness direction of the sheet formed by roll molding) is measured by Kyoto Electronics Industry. It evaluated by the rapid thermal conductivity meter by Corporation | KK, and also evaluated the breaking strength and breaking elongation based on JISK6251. The results are also shown in Table 1.

NR: Natural rubber VGCF-R: Vapor-grown carbon fiber (manufactured by Showa Denko KK, fiber length 10 μm, aspect ratio 67)
VGCF-H: Vapor growth carbon fiber (manufactured by Showa Denko KK, fiber length 5 μm, aspect ratio 33)
Anti-aging agent: N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine ZnO: zinc white CZ: N-cyclohexyl-2-benzothiazyl sulfenamide

When Example 1, Comparative Example 1 and Comparative Example 2 having the same amount of fibrous filler are compared, the rubber composition for rolls of the present invention (Example 1) uses only a high aspect ratio filler (Comparison) Compared to Example 1) and the one using only the low aspect ratio filler (Comparative Example 2), it gives high thermal conductivity in the direction perpendicular to the roll direction in roll forming without lowering strength or elongation. I understand.

Claims (6)

  A rubber composition comprising a diene rubber, sulfur and a fibrous filler, wherein the fibrous filler is a combination of a high aspect ratio filler and a low aspect ratio filler. A rubber composition for roll forming.   The rubber composition for roll forming according to claim 1, wherein the ratio of the aspect ratio of the high aspect ratio filler to the aspect ratio of the low aspect ratio filler is 1.5: 1 to 100: 1.   The rubber composition for roll forming according to claim 1 or 2, wherein 10 to 90 parts by mass of the low aspect ratio filler is used in combination with 100 parts by mass of the high aspect ratio filler.   The rubber composition for roll forming according to any one of claims 1 to 3, wherein a blending ratio of the fibrous filler is 0.01 to 100 parts by mass with respect to 100 parts by mass of the diene rubber.   The rubber composition for roll forming according to any one of claims 1 to 4, wherein the fibrous filler is vapor grown carbon fiber. A pneumatic tire formed using the rubber composition according to any one of claims 1 to 5, wherein the rubber composition is molded by roll molding, and the obtained molded body is a roll in the roll molding. A pneumatic tire characterized in that the direction is set as the rotational circumferential direction of the pneumatic tire and cured.