JP2006298946A - Vulcanized rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vulcanized rubber composition that exhibits a good balance among various properties and, particularly, is excellent in mechanical properties and thermal conductivity by using a filler exhibiting high effects even with a relatively small added amount and exerting no bad influences on other performances such as dynamic properties. <P>SOLUTION: The vulcanized rubber composition comprises a rubber material as a base material and, incorporated as a filler therewith, a carbon fiber having a number-average grain size of at most 5 μm and a weight-average grain size of at most 20 μm in the size distribution as measured by a laser diffraction grain size distribution measuring apparatus. The content of the carbon fiber is preferably 0.01-100 pts.mass based on 100 pts.mass of the rubber material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a vulcanized rubber composition (hereinafter, also simply referred to as “composition”). Specifically, it has good thermal conductivity, electrical conductivity, mechanical properties and the like, and also has moldability such as kneadability. The present invention relates to an excellent vulcanized rubber composition.

  For various products such as electric and electronic parts, tires, and belts, rubber compositions based on various natural rubbers and various synthetic rubbers are used according to the characteristics. The performance and function of such products are greatly affected by sub-materials such as various fillers and vulcanization conditions as well as the rubber material as the base material.

  For example, carbon black and silica are widely known as fillers for obtaining the reinforcing effect of natural rubber. In order to enhance thermal conductivity, alumina, boron nitride, etc. are used, and in order to impart electrical conductivity. For example, a metal powder such as copper or nickel or a conductive carbon is mixed.

Further, Patent Document 1 reports that a rubber composition having a high elastic modulus, excellent crack growth resistance and rebound resilience, and a high thermal conductivity can be obtained by using vapor grown carbon fiber. . Furthermore, in Patent Document 2, in order to improve the conductivity without deteriorating the characteristics due to silica blending, rubber containing rubber, silica, and vapor-grown carbon fiber having an average diameter of 0.01 to 3 μm. Compositions have been reported.
JP-A-1-287151 (Claims etc.) Japanese Patent Laid-Open No. 8-127664 (claims, etc.)

  However, in the conventionally known fillers, in order to obtain a high effect, the blending amount must be increased. As a result, uniform dispersion of the fillers cannot be obtained, resulting in variations in performance and viscosity. As a result, the moldability deteriorates due to a large increase in the temperature and physical properties, or the mechanical properties of the resulting rubber article deteriorates, making it unusable.

  Moreover, even when vapor-grown carbon fibers are blended in a rubber composition as described in Patent Documents 1 and 2, higher performance in terms of thermal conductivity and electrical conductivity while still maintaining the elastic modulus. Today, there is a desire to achieve this.

  Therefore, the object of the present invention is to balance the physical properties by using a filler that exhibits a high effect even when added in a relatively small amount and does not adversely affect other properties such as mechanical properties. An object of the present invention is to provide a vulcanized rubber composition having improved thermal conductivity and electrical conductivity while maintaining mechanical properties.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors use carbon fibers having a specific size distribution as a filler, so that thermal conductivity, electrical conductivity, and mechanical properties are greatly increased even with a small amount of addition. The present invention has been completed by finding that it has been improved and sufficient effects can be obtained without adversely affecting other physical properties.

  That is, the vulcanized rubber composition of the present invention has a number average of 5 μm or less and a weight average of 20 μm or less of a size distribution measured with a laser diffraction particle size distribution measuring device, using a rubber material as a base material and a filler. It contains a certain carbon fiber.

  In this invention, it is preferable that content of the said carbon fiber is 0.01-100 mass parts with respect to 100 mass parts of said rubber materials, Moreover, suitably the said carbon fiber is a vapor growth carbon fiber. It is. Furthermore, the content of the filler other than the vapor-grown carbon fiber is preferably 0 to 120 parts by mass with respect to 100 parts by mass of the rubber material, and more preferably the filler other than the vapor-grown carbon fiber. As the agent, carbon black and / or an inorganic filler are contained.

  According to the vulcanized rubber composition of the present invention, by using a structure composed of carbon atoms of a specific shape as a filler, even if added in a small amount, without greatly changing other physical properties, A significant improvement effect of characteristics such as thermal conductivity and electrical conductivity can be obtained without impairing moldability. Therefore, the vulcanized rubber composition of the present invention can be widely used for electric and electronic parts, tires, belts and other various products.

Hereinafter, specific embodiments of the present invention will be described.
The vulcanized rubber composition of the present invention comprises a rubber material as a base material and contains predetermined carbon fibers as a filler. It is important that the carbon fiber has a number average of 5 μm or less and a weight average of 20 μm or less of the size distribution measured with a laser diffraction particle size distribution analyzer. In obtaining high thermal conductivity and high electrical conductivity, the number average of the same size distribution is preferably 4 μm or less, more preferably 3 μm or less. Furthermore, the weight average of the same size distribution is preferably 15 μm or less, more preferably 10 μm or less.

Moreover, as carbon fiber which can satisfy | fill this size distribution favorably, a vapor growth carbon fiber can be mentioned suitably. Vapor-grown carbon fiber is a fine fibrous (annular ring) structure on the order of 10 ⁻² to 10 ⁻¹ times that of ordinary carbon fiber (CF) (average diameter 5 μm to length 100 μm). There is an advantage that problems such as dispersibility are less likely to occur than when carbon fiber is added, and the same performance improvement effect can be obtained.

  By using the carbon fiber according to the invention, sufficient effects of improving thermal conductivity, electrical conductivity, etc. can be obtained even with a small amount of addition, and a large amount of addition is likely to occur when conventional fillers are used. There is no inconvenience such as deterioration of other characteristics and moldability.

  The carbon fiber according to the present invention is not particularly limited, and those having a fiber diameter, a fiber length, and an aspect ratio corresponding to required performance can be used as appropriate. Specifically, for example, a vapor grown carbon fiber VGCF (registered trademark) manufactured by Showa Denko KK can be used as a commercial product.

  Examples of the rubber material include 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, and high cis-1. , 4 Polyisoprene rubber, etc. Diene special rubber, such as nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, etc., Olefin special rubber, eg, ethylene-propylene rubber, butyl rubber, halogenated butyl rubber, acrylic rubber, chlorosulfonated Other special rubbers such as polyethylene, for example, hydrin rubber, fluororubber, 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 rubber material according to the present invention is used after being vulcanized, and as a crosslinking method, sulfur, peroxide, metal oxide or the like is added and crosslinked by heating, or a photopolymerization initiator is added. And a method of crosslinking by light irradiation, a method of crosslinking by irradiation with an electron beam or radiation, and the like.

  The content of the carbon fiber according to the present invention is preferably 0.01 to 100 parts by mass with respect to 100 parts by mass of the rubber material. If the amount is less than 0.01 parts by mass, the desired performance cannot be obtained sufficiently. Even if the amount exceeds 100 parts by weight, the desired performance cannot be further improved. Since the workability | operativity in etc. falls, neither is preferable.

  In the composition of the present invention, it is preferable to contain 0 to 120 parts by mass of various fillers other than the carbon fibers according to the present invention, particularly the vapor-grown carbon fibers, with respect to 100 parts by mass of the rubber material. 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 carbon fiber according to the present invention is added. As the carbon black, known ones such as those of HAF grade can be used. In addition, as a method for mixing and molding the vulcanized rubber composition, a known method used for mixing and molding a normal vulcanized rubber can be used, and there is no particular limitation. In addition, the vulcanized rubber composition of the present invention includes additives commonly used in the rubber industry, such as vulcanizing agents, vulcanization accelerators, reinforcing materials, anti-aging agents, softening agents, etc. Additives can be used as appropriate.

Hereinafter, based on an Example, this invention is demonstrated in detail.
Examples and Comparative Examples Natural rubber (NR) as a rubber material and various additives are mixed with the contents shown in Table 1 below, and a vulcanized rubber composition according to the following kneading conditions and sheet preparation conditions. A sheet of material was prepared. The compounding amounts in Table 1 below all represent parts by mass. In addition, a master sizer (Mastersizer) 2000 manufactured by Sysmex Corporation was used to measure the size distribution of the carbon fibers used. The measurement conditions at this time were as follows: measurement temperature: room temperature, dry measurement, supply rate: 10%, air pressure: 3 bar. The measurement results are also shown in Table 1.

１）昭和電工（株）製、気相法炭素繊維（ＶＧＣＦ（登録商標））
２）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
３）Ｎ−シクロヘキシル−２−ベンゾチアジル・スルフェンアミド

1) Vapor grown carbon fiber (VGCF (registered trademark)), manufactured by Showa Denko K.K.
2) N- (1,3-dimethylbutyl) -N′-phenyl-P-phenylenediamine 3) N-cyclohexyl-2-benzothiazyl sulfenamide

Kneading conditions Laboplast mill (manufactured by Toyo Seiki Co., Ltd.) was used for kneading at NR of 70 ° C. and 50 rpm for 3 minutes. Additives were added and further mixed at 70 rpm at 70 ° C. (non-pro blending). The obtained mixture was taken out, cooled and weighed, and then the remaining ZnO, vulcanization accelerator and sulfur were added and mixed again at 30 rpm at 50 ° C. using a lab plast mill (professional formulation).

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

Evaluation of Physical Properties The obtained sheet of each composition was evaluated as follows for each of elastic modulus G ′, breaking strength Tb, breaking elongation Eb, volume resistivity, and thermal conductivity.

  The elastic modulus G 'was measured using ARES manufactured by Rheometrics Co., Ltd. under the conditions of a strain of 1%, a frequency of 15 Hz, and a measurement temperature of 50C. The breaking strength Tb and breaking elongation Eb were measured in accordance with JIS K6251. The volume resistivity was measured using Loresta and Hiresta manufactured by Mitsubishi Chemical Corporation. Further, the thermal conductivity was measured using a rapid thermal conductivity meter QTM-500 manufactured by Kyoto Electronics Co., Ltd. The obtained results are shown in Table 2 below.

  As is clear from the results in Table 2 above, the vulcanized rubber compositions of the examples have better mechanical properties, volume resistivity, and thermal conductivity than the comparative examples.

  The vulcanized rubber composition of the present invention is blended with a small amount of the carbon fiber according to the present invention, so that the other physical properties are not greatly changed, and the molding processability is not impaired. Therefore, it can be widely used for electric and electronic parts, tires, belts, and other various products.

Claims (5)

  A carbon material having a rubber material as a base material and a carbon fiber having a number average of 5 μm or less and a weight average of 20 μm or less of a size distribution measured with a laser diffraction particle size distribution analyzer as a filler. Sulfur rubber composition.   The vulcanized rubber composition according to claim 1, wherein a content of the carbon fiber is 0.01 to 100 parts by mass with respect to 100 parts by mass of the rubber material.   The vulcanized rubber composition according to claim 1 or 2, wherein the carbon fibers are vapor grown carbon fibers.   The vulcanized rubber composition according to claim 3, wherein the content of the filler other than the vapor-grown carbon fiber is 0 to 120 parts by mass with respect to 100 parts by mass of the rubber material.   The vulcanized rubber composition according to claim 3 or 4, comprising carbon black and / or an inorganic filler as a filler other than the vapor-grown carbon fiber.