JP2007211194A - Rubber composition for carcass coating and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a rubber composition providing a cured material having high mechanical properties and high anisotropy as carcass coating and to provide a pneumatic tire having excellent durability and driveability by applying the cured material of the rubber composition to a carcass coating material. <P>SOLUTION: The rubber composition for carcass coating comprises a vapor-phase growth carbon fiber. The pneumatic tire is equipped with a coated carcass produced by coating carcass cords with the cured material of the rubber composition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a carcass coating rubber composition useful for forming a carcass coating material that requires high anisotropy as well as high mechanical properties in a pneumatic tire, and a cured product of the rubber composition as a carcass coating material. The present invention relates to a pneumatic tire having excellent durability and handling stability.

  Various rubbers are used for each part constituting the pneumatic tire, and among them, the rubber covering the carcass that is the skeleton of the tire is required to have high mechanical properties and high anisotropy.

  Conventionally, as a rubber composition which gives a rubber cured product having stress anisotropy having greatly different moduli in the vertical direction and the horizontal direction (for example, the roll direction during roll extrusion molding and the direction perpendicular to the roll direction), nylon and polyester Rubber compositions containing short fibers such as vinylon are known.

  For example, JP-A-59-43041 (Patent Document 1) describes a reinforced rubber composition in which a rubber and a nylon fiber embedded therein are graft-bonded via an initial condensate of a novolac type phenol formaldehyde resin. Has been. However, in this rubber composition, a resin curing agent is blended in a kneaded mixture of rubber and nylon fiber and cured in the rubber. Therefore, it is difficult to adjust the graft bond between the nylon fiber and the rubber. In addition, only rubber compositions with limited nylon fiber content could be obtained. Therefore, a rubber cured product having sufficient anisotropy cannot be obtained from this rubber composition.

  In order to solve this problem, Japanese Patent Publication No. 3-49932 (Patent Document 2) performs short fiber reinforcement and resin reinforcement by kneading aromatic polyamide pulp short fibers and phenolic resin into rubber. A rubber composition that can achieve high anisotropy as well as high elastic modulus is described. However, in this rubber composition, since the rubber molecules and the aromatic polyamide pulp short fibers are not directly bonded, the reinforcing efficiency is low, and the short fibers themselves act as fracture nuclei in the rubber, and the fatigue resistance of the rubber. In addition, since the pulp-like fibers are dispersed in the rubber using a kneader such as a Banbury mixer, the dispersion level is extremely low. The reinforcing effect on the blending amount is lowered, and if the amount is further increased, there is a drawback that kneading and extrusion become extremely difficult.

  Therefore, in order to obtain the desired elastic modulus in rubber having anisotropy, it was considered to add carbon black and novolac type phenol resin to short fiber compounded rubber, but carbon black and novolac type phenol resin were added. This greatly increases the viscosity of the rubber, making it difficult to work in each process such as kneading, sheeting, heating, and extruding, as well as making it difficult to arrange the short fibers in the desired direction. There is a drawback that the effect of blending the short fibers is greatly reduced.

  Furthermore, from the viewpoint of improving the workability and processability of rubber, it is conceivable to use a softening agent such as oil or resin as a conventional technique. Although it is easy to arrange the fibers in the desired method, it is impossible to avoid a decrease in elastic modulus and deterioration in heat generation due to the addition of a softening agent, as in the case of conventional rubber, and thus a rubber composition having desired physical properties can be obtained. There is no problem.

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

JP 59-43041 A Japanese Patent Publication No. 3-49932 JP-A-1-287151 Japanese Unexamined Patent Publication No. 1-289843 JP-A-1-289844 JP-A-2-302452 JP 2004-285294 A JP 7-309974 A JP-A-9-220911

  The present invention has been made in view of the above circumstances, and applied to a carcass coating material, a rubber composition that gives a cured product having high anisotropy as well as high mechanical properties for carcass coating, and the cured product of this rubber composition. An object of the present invention is to provide a pneumatic tire excellent in durability and handling stability.

  As a result of intensive studies to achieve the above object, the present inventors have found that a rubber composition containing a diene rubber and vapor grown carbon fiber is a cured product having high mechanical properties and high anisotropy. It is found that a pneumatic tire in which a cured product of this rubber composition is applied to a carcass covering material has excellent steering stability without sacrificing durability, and thus forms the present invention. It came.

Accordingly, the present invention provides the following carcass-covering rubber composition and pneumatic tire.
[Claim 1] A rubber composition for carcass coating, comprising a diene rubber and a vapor-grown carbon fiber.
[Claim 2] The rubber composition for carcass coating according to claim 1, wherein the compounding ratio of the vapor-grown carbon fiber is 1 to 80 parts by mass with respect to 100 parts by mass of the diene rubber.
[Claim 3] A pneumatic tire comprising a coated carcass in which a carcass cord is coated with a cured product of the rubber composition for covering a carcass according to claim 1 or 2.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for carcass coating useful for formation of the carcass coating | covering material with which high anisotropy is requested | required with a high mechanical characteristic in a pneumatic tire can be provided, and also this rubber composition By applying the cured product to the carcass covering material, it is possible to provide a pneumatic tire excellent in durability and handling stability.

Hereinafter, the present invention will be described in more detail.
The rubber composition of the present invention is obtained by blending a diene rubber and vapor grown carbon fiber. The pneumatic tire of the present invention includes a covered carcass in which a carcass cord is coated with a cured product of the rubber composition of the present invention.

  In a pneumatic tire, a rubber covering a carcass that is a skeleton of a tire is required to have high anisotropy as well as high mechanical properties. High anisotropy is required at the tire part because it is highly elastic only for selective input in order to improve the steering stability of the tire without sacrificing the tire performance such as riding comfort and durability. The cured product of the rubber composition of the present invention has high stress anisotropy while maintaining the rebound resilience required in these parts. Thus, by using the rubber composition of the present invention to form a carcass covering material for a pneumatic tire, a pneumatic tire excellent in high performance, particularly durability and steering stability can be obtained.

  As a pneumatic tire which applied the hardened | cured material of the rubber composition of this invention to the carcass coating | covering material, what is shown by FIG. 1 is mentioned, for example. FIG. 1 is a cross-sectional view in the width direction of a pneumatic radial tire. The tire 1 includes a covered carcass 2 including a carcass cord whose cord direction is the radial direction of the tire and a carcass covering material that covers the carcass cord. The covered carcass 2 is provided in the U-shaped cross section over the entire circumference in the tire rotation direction, and both end portions in the cross section of the covered carcass 2 are provided over the entire circumference in the tire rotation direction. The pair of bead wires 3 and 3 and the pair of left and right bead fillers 4 and 4 arranged over the entire circumference in the tire rotation direction adjacent to the tire outer side in the radial direction of the tire are folded back outward in the width direction of the tire. It is. Two layers of steel belts 5 and 5 are provided in the vicinity of the outer periphery of the coated carcass 2 over the entire circumference of the tire in the rotational direction, and a tread rubber 6 serving as a tire tread is provided on the outer side. Is provided over the entire circumference in the rotation direction. Further, side rubbers 7 and 7 are formed on both outer side surfaces in the width direction of the tire of the coated carcass 2, inner liner rubber 8 is formed on the inner surface (inner peripheral surface and inner side surface) of the coated carcass 2, and tires at both ends of the coated carcass 2. A pair of left and right chafer rubbers 9, 9 are provided in the vicinity of the rotation shaft side over the entire circumference of the tire in the rotation direction.

  And the hardened | cured material of the rubber composition of this invention is used as a carcass coating material which coat | covers the carcass cord of the said covering carcass 2. As shown in FIG. In addition, although the example of the radial tire was shown in FIG. 1, it is not limited to this, For example, a bias tire can also be made into object.

  In the rubber composition of the present invention that provides such a carcass covering material for a pneumatic tire, a diene rubber as a base material and a vapor growth carbon fiber are blended.

  Examples of the diene rubber include natural rubber, ethylene / propylene / diene rubber (EPDM), styrene / butadiene copolymer rubber (SBR), butadiene rubber, isoprene rubber, butyl rubber, halogenated butyl rubber, isobutylene and p-halogenated methylstyrene. And acrylonitrile / butadiene copolymer rubber (NBR). These may be used alone or in combination of two or more.

  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, the vapor-grown carbon fiber has a diameter of 1 μm or less, preferably 1 nm to 1 μm, more preferably 10 nm to 0.2 μm, and an aspect ratio (length / diameter) of 5 is preferable. It is preferable to use those of ˜1,000, particularly 10 to 500. In addition, it is preferable that the compounding quantity of vapor growth carbon fiber is 1-80 mass parts with respect to 100 mass parts of diene rubbers, especially 3-50 mass parts. If the amount of vapor-grown carbon fiber is too large, non-dispersion may occur and the fracture strength may decrease, and if it is too small, anisotropy of elastic modulus may not be exhibited.

  The rubber composition of the present invention is further provided with a vulcanizing agent such as sulfur or an organic sulfur compound according to a conventional method, in accordance with physical properties required for a carcass coating material used as a cured product, and vulcanization acceleration. It is possible to add additives such as an agent, a vulcanization acceleration aid, a filler, an anti-aging agent, a softening agent, and a dispersing agent within the range of normal 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, 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. The blending amount of the filler is preferably 100 parts by mass or less, more preferably 10 to 70 parts by mass with respect to 100 parts by mass of the diene rubber.

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

  As conditions for vulcanizing the rubber composition obtained by blending the components as described above, normal vulcanization conditions can be employed. The shape and structure of the coated carcass (that is, the shape and structure of the carcass cord, and the shape and structure of the coating material that covers the carcass cord), and the coating forming method of the coating material on the carcass cord are conventionally known shapes and structures. And methods can be employed.

  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.

[Comparative Example 1, Examples 1-3]
Each raw material component was blended in the blending shown in Table 1, and kneaded using a Banbury mixer to obtain an unvulcanized rubber composition. About the hardened | cured material obtained by hardening this rubber composition, the physical property was evaluated as follows. The results are also shown in Table 1.

For a rubber sheet formed by M50 anisotropic roll extrusion, the 50% modulus (A) in the roll extrusion direction of the sheet and the 50% modulus (B) in the direction perpendicular to the roll extrusion direction were measured, and the ratio ( A / B) was defined as M50 anisotropy.
The resilience was measured in accordance with JIS K 6301, and expressed as a ratio when the measured value of Comparative Example 1 was 100.

  Further, this unvulcanized rubber composition was coated on a polyethylene terephthalate (PET) cord having a twist of 1,500 denier to a thickness of about 1 mm, and this was applied as a coated carcass 2 shown in FIG. A pneumatic radial tire of size 205 / 65R15 was manufactured. The manufactured pneumatic radial tire was evaluated for steering stability, riding comfort and durability as follows. The results are also shown in Table 1.

Steering stability test tires were mounted on a vehicle (domestic FF2000cc), running at a speed of 40 to 120 km / hour, straight running, lane change, and driving stability was evaluated by the driver's feeling. The evaluation was performed with 10 points being a perfect score.

Ride comfort In the same vehicle as in the case of handling stability, the vehicle was run on good, joint and bad roads at a speed of 40 to 80 km / hour, and the ride comfort was evaluated by the driver's feeling. The evaluation was performed with 10 points being a perfect score.

A durability durability drum test was conducted. After adjusting the prototype tire to the maximum air pressure of JIS standard in a room at 25 ° C ± 2 ° C, letting it stand for 24 hours, readjust the air pressure, load the tire twice the maximum load of JIS standard, It was run at a speed of 60 km / hr on a drum of about 1.7 m. A vehicle that had traveled 50,000 km without any failure was considered a complete race.

Vapor growth carbon fiber: VGCF-R (diameter 150 nm, aspect ratio 10 to 500) manufactured by Showa Denko K.K.
Anti-aging agent: Nocrack 6C manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
Vulcanization accelerator: Nouchira DZ manufactured by Ouchi Shinsei Chemical Co., Ltd.

It is sectional drawing which shows an example of the pneumatic tire of this invention.

Explanation of symbols

1 Pneumatic tire 2 Covered carcass 3 Bead wire 4 Bead filler 5 Steel belt 6 Tread rubber 7 Side rubber 8 Inner liner rubber 9 Chafer rubber

Claims (3)

  A rubber composition for carcass coating, comprising a diene rubber and a vapor-grown carbon fiber.   The rubber composition for carcass coating according to claim 1, wherein the compounding ratio of the vapor-grown carbon fiber is 1 to 80 parts by mass with respect to 100 parts by mass of the diene rubber. A pneumatic tire comprising a covered carcass coated with a carcass cord with a cured product of the rubber composition for covering a carcass according to claim 1 or 2.

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