JP2010265363A - Rubber composition and tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition excellent in thermal conductivity without diminishing dynamic strength and pyrogenetic properties and a tire using the same. <P>SOLUTION: The rubber composition containing vapor-grown carbon fibers crushed in a vibration mill to a rubber component, and the tire using the same are provided. The vapor-grown carbon fibers are preferably crushed in the vibration mill for 1-300 minutes, and the content of the vapor-grown carbon fibers is preferably 1-30 pts.mass based on 100 pts.mass of the rubber component. Based on 100 pts.mass of the rubber component, 20-80 pts.mass of a filler other than the vapor-grown carbon fibers is preferably contained, and carbon black and/or an inorganic filler are preferably contained as the filler other than the vapor-grown carbon fibers. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rubber composition and a tire using the same, and more particularly to a rubber composition excellent in thermal conductivity without impairing mechanical strength and a tire using the same.

  In the rubber industry, conventionally, carbon fiber is generally blended with a rubber component for the purpose of obtaining predetermined rubber properties. In particular, various techniques for obtaining a rubber composition having desired physical properties by blending carbon fibers having a predetermined shape have been proposed so far, and vapor phase growth has been performed to impart conductivity and thermal conductivity to rubber. A technique for compounding with carbon fiber, carbon nanotube, or the like has attracted attention.

  In such a technology, some carbon nanofibers such as vapor-grown carbon fiber and carbon nanotube have excellent thermal and electrical conductivity, and outstanding thermal and electrical conductivity when mixed with rubber components. For example, when the rubber composition is used in a tire, the vulcanization time can be significantly shortened, and the resulting tire is a tire excellent in heat dissipation, maintained or improved in hysteresis loss, A tire having excellent durability can be obtained. Conversely, when a certain kind of carbon nano-nanofiber is used to increase the hysteresis loss of the rubber composition, a tire having excellent grip properties can be obtained.

  For example, in Patent Document 1, by adding a vapor-grown carbon fiber having a predetermined average diameter to the rubber component in addition to the siliceous filler, the conductivity can be improved without deteriorating the characteristics due to the silica compounding. The intended antistatic rubber composition is described. In this document, the vapor-grown carbon fiber has a mean diameter of 0.01 to 3 μm, particularly 0.05 to 0.5 μm. While not being crushed, the above-mentioned object can be satisfactorily achieved. On the other hand, when the average diameter of the vapor-grown carbon fiber is less than 0.01 μm, the vapor-grown carbon fiber is good in the rubber when the rubber is kneaded. If the average diameter of the vapor grown carbon fiber exceeds 3 μm, the vapor grown carbon fiber may tend to be crushed during kneading with rubber. The effect is also described.

  In addition, as a technique for combining vapor-grown carbon fibers and carbon nanotubes in order to impart conductivity and thermal conductivity to rubber, Patent Document 2 contains a diene rubber, sulfur and fibrous filler. A rubber composition for roll forming is described, wherein the fibrous filler is a combination of two types of fillers, a high aspect ratio filler and a low aspect ratio filler. .

  In the above technology, the thermal conductivity of the vapor-grown carbon fiber compounded rubber is excellent, so when used in tire treads, etc., it is expected that the heat inside the rubber product will be efficiently released to the outside of the product, Durability improvement is expected.

  On the other hand, Patent Document 3 discloses that a rubber composition capable of reliably realizing desired rubber properties can be obtained even when the kneading conditions are changed by eliminating the influence on the rubber properties due to kneading. As an object, a rubber composition containing a rubber component and vapor grown carbon fiber, the vapor grown carbon fiber after kneading has a length in the range of 0.5 to 1000 μm and a diameter. Describes a rubber composition in which is in the range of 0.01 to 50 μm.

Japanese Patent Laid-Open No. 8-127664 (claims, etc.) JP 2007-217458 A (Claims etc.) JP 2007-45942 A (Claims etc.)

  However, in the prior art described in Patent Documents 1 to 3, although effective for improving durability when used in a tire, as a result of mixing fiber-like nanocarbon such as vapor-grown carbon fiber and carbon nanotube into rubber, As physical properties of the vulcanizate, (1) the modulus at low strain (M10 to M50) is greatly increased and the rigidity as a tire is excessively increased. (2) As the compounding amount of the fibrous nanocarbon increases, Breaking strength (Tb), elongation (Eb) and wear resistance are reduced, (3) Loss tangent (Tan δ, hysteresis loss) is increased, and as a tire, rolling resistance is deteriorated, heat generation is increased, and durability is reduced. (4) Bulk specific gravity is generally low, especially in the case of vapor-grown carbon fibers, so that it takes a lot of time to be charged when blended or it is easily scattered lightly. Can not kneading precise amount, it appears phenomenon of poor) or the like in the environment, as a tire using the same, there is room for further improvement.

  In particular, when vapor-grown carbon fiber, which has been used in the industrial field, is blended with the rubber component, the main dispersion of the glass transition point in the temperature range of room temperature to 100 ° C. in the temperature dispersion behavior of loss tangent (Tan δ). Apart from that, shoulders (broad peaks) occur. This means that, in the case of a tire, the heat generation increases considerably at the use temperature. In other words, even when vapor-grown carbon fiber is introduced into a tire or other rubber product and the heat dissipation of the heat accumulated in the product is improved by improving thermal conductivity, the exothermic term is simultaneously generated by mixing the vapor-grown carbon fiber and the rubber component. However, there was room for further improvement since extra heat was generated.

  Accordingly, an object of the present invention is to provide a rubber composition excellent in thermal conductivity and a tire using the rubber composition without impairing mechanical strength and heat generation.

  As a result of intensive studies to solve the above problems, the present inventor has found that the above problems can be solved by crushing vapor-grown carbon fibers using a vibration mill, and has completed the present invention.

  That is, the rubber composition of the present invention is characterized by containing vapor-grown carbon fibers that have been pulverized by a vibration mill with respect to the rubber component.

  In the rubber composition of the present invention, the vapor-grown carbon fiber is preferably pulverized by vibration mill for 1 to 300 minutes, and the content of the vapor-grown carbon fiber is 100 parts by mass of the rubber component. On the other hand, it is preferable that it is 1-30 mass parts.

  Furthermore, the rubber composition of the present invention preferably contains 20 to 80 parts by mass of a filler other than the vapor-grown carbon fiber with respect to 100 parts by mass of the rubber component. It is preferable to contain carbon black and / or an inorganic filler as the filler.

  The tire of the present invention is characterized by using the rubber composition.

  According to the present invention, it is possible to provide a rubber composition excellent in thermal conductivity without impairing mechanical strength and heat buildup, and a tire using the rubber composition as a reinforcing material also impairs mechanical strength and heat buildup. And has excellent thermal conductivity.

It is a graph which shows the relationship between temperature and Tanδ.

Embodiments of the present invention will be specifically described below.
The vapor-grown carbon fiber in the present invention is not limited as long as it can be pulverized by a vibration mill to obtain a desired effect, and any one can be used. By pulverizing the vibration mill, the vapor-grown carbon fiber is crushed and shortened in length, but the decrease in the thermal conductivity of the vapor-grown carbon fiber is reduced (as compared with rubber not containing the vapor-grown carbon fiber). The overwhelmingly high thermal conductivity) and the loss tangent (Tanδ) of the vapor grown carbon fiber are greatly reduced (the shoulder generated around room temperature to 100 ° C is markedly reduced), and the vapor grown carbon fiber is further reduced. There is also an effect that the modulus of elasticity accompanying the introduction, particularly the modulus increase at low strain is small. Furthermore, the bulk specific gravity of the vapor grown carbon fiber can be significantly increased, and the blending workability can be improved.

  In the present invention, as the vapor-grown carbon fiber pulverized by vibration mill, for example, a known vapor-grown carbon fiber is fluidized only by vibration, a medium such as a ball for vibration mill is introduced, and the pressure is reduced under reduced pressure. In this method, drying is performed by indirect heating, and the vapor-grown carbon fiber in a dry state is recovered by simultaneous treatment of drying and crushing, drying by slurry feed, evaporation, or the like.

  In the present invention, the vapor-grown carbon fiber is preferably pulverized by vibration mill for 1 to 300 minutes under reduced pressure, more preferably pulverized by vibration mill for 5 to 150 minutes. By pulverizing the vibration mill within this range, a rubber composition having better thermal conductivity can be obtained without deteriorating the mechanical strength and heat generation.

  Further, as the vapor growth carbon fiber before pulverizing the vibration mill, the fiber diameter is preferably 0.04 to 0.5 μm, more preferably 0.05 to 0.4 μm, and particularly 0.07 to 0.3 μm. Use one. Further, the fiber length is not particularly limited, and those having an average fiber length of 0.5 to 50 μm, more preferably 1 to 40 μm, particularly 1.5 to 30 μm can be used.

Furthermore, as the vapor growth carbon fiber before vibration mill crushing, for example, vapor growth carbon fiber (trade name VGCF-S, diameter 100 nm, length 10 μm, bulk density 0.02 g / cm ³ manufactured by Showa Denko KK And the like.

  As the rubber component in the present invention, natural rubber, general-purpose synthetic rubber such as emulsion polymerization styrene-butadiene rubber, solution polymerization styrene-butadiene rubber, high cis-1,4 polybutadiene rubber, low cis-1,4 polybutadiene rubber, high Cis-1,4 polyisoprene rubber, etc., diene special rubber, for example, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, etc., olefin special rubber, for example, ethylene-propylene rubber, butyl rubber, halogenated butyl rubber, acrylic rubber, Other special rubbers such as chlorosulfonated polyethylene, for example, hydrin rubber, fluorine rubber, polysulfide rubber, urethane rubber and the like can be mentioned. From the balance between cost and performance, natural rubber or general-purpose synthetic rubber is preferable.

  The content of the vapor-grown carbon fiber pulverized by vibration mill according to the present invention is preferably 1 to 30 parts by mass, more preferably 2 to 25 parts by mass with respect to 100 parts by mass of the rubber component. . If the amount is less than 1 part by mass, the expected performance cannot be sufficiently obtained. On the other hand, even if the amount exceeds 30 parts by mass, the desired effect of further improvement is hardly exhibited. Neither is desirable because the properties are reduced.

  In the composition of the present invention, it is preferable to contain 20 to 80 parts by mass of various fillers other than the vapor-grown carbon fiber pulverized by vibration mill according to the present invention with respect to 100 parts by mass of the rubber component. . More preferably, carbon black and / or an inorganic filler is contained as the filler. When an appropriate amount of carbon black and / or inorganic filler is contained in the composition, a higher reinforcing effect can be obtained than when only the vapor-grown carbon fiber according to the present invention is added. As the carbon black, known ones such as those of HAF grade can be used. Examples of inorganic fillers include silica and calcium carbonate.

  Further, the vapor-grown carbon fiber pulverized by the vibration mill can be used after being blended with a rubber component and vulcanized in a form that partially replaces the above-mentioned filler having a normal rubber composition. A rubber composition having excellent conductivity and mechanical properties can be obtained.

  Moreover, in the rubber composition of the present invention, various additives usually used in the rubber industry, in addition to the rubber component and the vapor-grown carbon fiber, may be appropriately blended within a range not impairing the effects of the present invention. it can. For example, coupling agents such as silane coupling agents, softeners, vulcanizing agents such as sulfur, vulcanization accelerators such as dibenzothiazyl disulfide, N-cyclohexyl-2-benzothiazyl-sulfenamide, N-oxy Antiaging agents such as diethylene-benzothiazyl-sulfenamide, zinc oxide, stearic acid, antiozonants, foaming agents, foaming aids, etc. may be mentioned, and these may be used alone or as 2 More than one species may be used in combination. In addition, a commercial item can be used as these various additives.

  The rubber composition of the present invention is prepared by kneading, heating, extruding, etc. as appropriate according to conventional methods, equipment, conditions, techniques, etc., and can be suitably applied to various rubber products such as tires. It can be suitably used for a tire.

  The kneading is not particularly limited with respect to various conditions such as the input volume to the kneading apparatus, the rotational speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the kneading apparatus, etc., and should be appropriately selected as desired. Can do. Examples of the kneading apparatus include an open kneader such as a roll and a closed kneader such as a Banbury mixer, and commercially available products can be preferably used.

  Regarding the heating or extrusion, there are no particular limitations on the conditions such as the heating or extrusion time, the heating or extrusion apparatus, etc., and they can be appropriately selected as desired. Moreover, a commercial item can be used conveniently also about the apparatus of a hot-heating or extrusion.

  In addition, the tire of the present invention may be any member that uses the rubber composition of the present invention as a reinforcing material for members such as treads and belts, and its specific structure and other materials are particularly limited. It is not a thing. In addition, as gas with which the pneumatic tire of this invention is filled, inert gas, such as nitrogen, argon, helium other than the air which adjusted normal or oxygen partial pressure, can be used.

  By making a tire made of a member using the rubber composition of the present invention, heat conduction without significantly changing the rigidity of the tire and maintaining good wear resistance, fracture physical properties, and heat generation characteristics as a tire. A tire with greatly improved properties can be obtained.

  Next, the present invention will be described in more detail with reference to examples. The present invention is not limited by this example.

Preparation of vapor-grown carbon fiber pulverized by vibration mill Vapor-grown carbon fiber (trade name VGCF-S, diameter 100 nm, length 10 μm, bulk density 0.02 g / cm ³ ) manufactured by Showa Denko KK under reduced pressure. Then, the vibration mill was crushed at 60, 90, and 120 minutes to obtain vapor-grown carbon fiber (VGCF-S vibration mill pulverized product) that was pulverized by the vibration mill. In addition, the bulk density of the “VGCF-S vibration mill 90 cracked and cracked product”, which is a 90-minute treated product, was 0.154 g / cm ³ .

Examples 1 to 3 and Comparative Examples 1 and 2
Kneading conditions Natural rubber (NR) was kneaded at 70 ° C. and 50 rpm for 3 minutes in a lab plast mill (manufactured by Toyo Seiki Seisakusho) using various vapor-grown carbon fibers shown in Table 1. Each additive was added and further mixed at 70 rpm at 70 ° C. (non-pro blending). The obtained mixture was taken out, cooled and weighed, and then mixed again at 30 rpm at 50 ° C. using a plastic bender (professional formulation).

Rubber Sheet Preparation Conditions The kneaded mixture was vulcanized at 150 ° C. for 15 minutes using a high temperature press to prepare a 2 mm thick vulcanized rubber sheet.

  The following tests are performed on the obtained vulcanized rubber sheet, and the results are also shown in Table 1.

Measurement of thermal conductivity of rubber sheet Using a quick thermal conductivity meter QTM-500 manufactured by Kyoto Electronics Co., Ltd., the thermal conductivity of the rubber sheet was measured in the roll direction and in the anti-roll direction. 100 was evaluated. The higher the number, the better the result.

Measurement of elastic modulus (E ′) and loss tangent Using a viscoelasticity measurement system (Rheograph) manufactured by Toyo Seiki Seisakusho Co., Ltd., elastic modulus in the roll direction at a temperature of 60 ° C. under conditions of 50 Hz and 2% strain ( E ′) and loss tangent (tan δ) were measured.

Measurement of M100 and M300 The modulus (M100 and M300) at 100% elongation and 300% elongation was measured according to the tensile test of JIS K6301-1975 “Physical Test Method for Vulcanized Rubber”.

Measurement of tensile strength and elongation at break A tensile test was performed at room temperature in accordance with JIS K 6251 to measure the tensile strength (Tb) and the elongation at break (Eb) of the vulcanized rubber.

１）ＨＡＦ：カーボンブラック（シースト３、東海カーボン株式会社製）
２）老化防止剤：Ｎ−（１，３−ジメチルブチル）−Ｎ’−フェニル−ｐ−フェニレンジアミン

1) HAF: Carbon black (Seast 3, manufactured by Tokai Carbon Co., Ltd.)
2) Anti-aging agent: N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine

  FIG. 1 is a graph showing the relationship between temperature and Tan δ. As is clear from the results of FIG. 1 and Table 1, the rubber composition containing the vapor-grown carbon fiber pulverized by vibration mill is the rubber composition containing the normal vapor-grown carbon fiber not crushed in Comparative Example 2. Compared to the product, significantly improved Tan δ deteriorated, corrected heat generation to the level of Comparative Example 1 which is the control, the shoulder was almost disappeared in the temperature dispersion chart, and low hysteresis loss property over a wide temperature range Secured. In addition, increase in modulus of elasticity and low strain was suppressed, and the riding comfort as a tire could be improved, and the bulk specific gravity increased significantly, indicating the effectiveness in blending workability. Furthermore, the heat conductivity fall was small, and it was practically possible to provide a highly value-added heat-dissipating rubber composition.

Claims (6)

  A rubber composition comprising vapor-grown carbon fibers pulverized by vibration mill with respect to a rubber component.   The rubber composition according to claim 1, wherein the vapor grown carbon fiber is pulverized by vibration mill for 1 to 300 minutes.   The rubber composition according to claim 1 or 2, wherein the content of the vapor-grown carbon fiber is 1 to 30 parts by mass with respect to 100 parts by mass of the rubber component.   The rubber composition according to any one of claims 1 to 3, further comprising 20 to 80 parts by mass of a filler other than the vapor-grown carbon fiber with respect to 100 parts by mass of the rubber component.   The rubber composition according to claim 4, comprising carbon black and / or an inorganic filler as a filler other than the vapor-grown carbon fiber.   A tire using the rubber composition according to any one of claims 1 to 5.

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