JP2008201829A - Rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of improving mechanical characteristics such as breaking strength in a rubber composition comprising vapor-grown carbon fibers compounded therein. <P>SOLUTION: The rubber composition comprises a rubber component and the vapor-grown carbon fibers. In the rubber composition, a liquid rubber having 1,000-100,000 number-average molecular weight is compounded. The amount of the compounded liquid rubber is preferably within the range of 1-20 pts.wt. based on 100 pts.wt. of the rubber component. Polyisoprene, polybutadiene, a styrene-butadiene copolymer, a styrene-isoprene copolymer and a styrene-butadiene-isoprene copolymer can suitably be used as the liquid rubber. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rubber composition, and more particularly to improvement of mechanical properties in a rubber composition containing vapor-grown carbon fibers.

  Various attempts have been made to improve the performance of rubber compositions, and recently, rubber compositions containing vapor-grown carbon fibers have also been proposed as fillers that can achieve a high effect with a relatively small amount of addition. Has been.

Regarding the rubber composition containing the vapor-grown carbon fiber, for example, in Patent Document 1, the vapor-grown carbon fiber having an average aspect ratio of less than 10 as a filler is blended with the rubber material as the base material. A rubber composition having an improved tan δ value at 40 ° C. or higher and a modulus at 80 ° C. or higher is disclosed. Further, in order to improve mechanical properties such as workability and fatigue resistance of vulcanized rubber containing vapor-grown carbon fiber, a softener (oil) is also added.
JP 2003-327753 A (Claims etc.)

  As described above, by blending oil with vulcanized rubber blended with vapor-grown carbon fiber, processability is improved, and the modulus increased by blending vapor-grown carbon fiber can be lowered to an appropriate range. It becomes possible. However, the improvement of fatigue resistance of the vapor growth carbon fiber compounded rubber composition is not sufficient, and there is a problem that the fracture strength, fracture life, and wear resistance are lowered.

  Therefore, an object of the present invention is to provide a technique for improving mechanical properties such as fracture strength in a rubber composition containing vapor-grown carbon fibers.

  As a result of intensive studies, the present inventors have found that the above problems can be solved by blending a liquid rubber having a specific molecular weight range with a vapor-grown carbon fiber-blended rubber composition, and the present invention has been completed. It came to do.

  That is, the rubber composition of the present invention is characterized in that a liquid rubber having a number average molecular weight of 1,000 to 100,000 is blended in a rubber composition containing a rubber component and vapor-grown carbon fibers. It is.

  In the present invention, the liquid rubber is preferably blended in an amount of 1 to 20 parts by weight with respect to 100 parts by weight of the rubber component. The liquid rubber is preferably one or more selected from the group consisting of polyisoprene, polybutadiene, styrene-butadiene copolymer, styrene-isoprene copolymer, and styrene-butadiene-isoprene copolymer. Can do. Furthermore, in this invention, the said vapor growth carbon fiber can be mixed in 2-30 weight part with respect to 100 weight part of said rubber components.

  According to the present invention, the above configuration makes it possible to realize a rubber composition with improved workability and fatigue resistance without sacrificing mechanical properties such as fracture strength and wear resistance. It was.

Hereinafter, preferred embodiments of the present invention will be described in detail.
The rubber composition of the present invention is characterized in that it contains a rubber component and vapor-grown carbon fibers and is blended with a liquid rubber having a number average molecular weight of 1,000 to 100,000. By adding a liquid rubber having a certain molecular weight range to a vapor-grown carbon fiber compounded rubber composition, the mechanical properties of the vulcanized rubber can be improved.

  The liquid rubber used in the present invention has a number average molecular weight of 1,000 to 100,000, preferably 5,000 to 70,000, more preferably 10,000 to 50,000. When the number average molecular weight is less than 1,000, the stress tends to be low and the strength is reduced. On the other hand, when it exceeds 100,000, the stress tends to be high and the fatigue property is reduced. The desired effect cannot be obtained.

  Specific examples of the liquid rubber include polyisoprene, polybutadiene, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-butadiene-isoprene copolymer (SIBR), and the like. It can be used by 1 type (s) or 2 or more types.

  The blending amount of the liquid rubber in the rubber composition of the present invention is preferably 1 to 20 parts by weight with respect to 100 parts by weight of the rubber component. If the blending amount of the liquid rubber is too much or too little, the desired effect of the present invention cannot be obtained sufficiently.

  The rubber component in the rubber composition of the present invention is not particularly limited, and natural rubber (NR), 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, diene special rubber, for example, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, olefin special rubber, for example, ethylene- Propylene rubber, butyl rubber, halogenated butyl rubber, acrylic rubber, chlorosulfonated polyethylene, and other special rubbers such as hydrin rubber, fluorine rubber, polysulfide rubber, and urethane rubber can be used. From the balance between cost and performance, natural rubber or general-purpose synthetic rubber is preferably used.

The vapor-grown carbon fiber is a fine fibrous structure on the order of 10 ⁻² to 10 ⁻¹ times that of normal carbon fiber (CF) (average diameter of 5 μm or more and length of about 100 μm). In the present invention, by using this vapor grown carbon fiber as a filler for the rubber composition, it is possible to obtain excellent effects of improving various properties with a small amount of addition.

In the present invention, any vapor growth carbon fiber may be used, but the fiber diameter is preferably 0.04 to 0.4 μm, more preferably 0.05 to 0.3 μm, particularly 0.07 to 0. Use a 2 μm 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, and particularly 1.5 to 25 μm can be used. Further, as the specific surface area, 5 to 50 m ² / g, and particularly preferably in the range of 8~30m ² / g. Such vapor-grown carbon fiber is easily available on the market, and for example, vapor-grown carbon fiber VGCF (registered trademark) manufactured by Showa Denko KK can be used.

  The vapor grown carbon fiber may be oxidized. Examples of the oxidation treatment method include chemical treatment using nitric acid, sulfuric acid, perchloric acid or a mixture of these acids, and physical treatment such as corona discharge treatment, plasma treatment, and ozone treatment. Furthermore, in addition to the oxidation treatment, vapor-grown carbon fibers treated with a coupling agent can also be used. Examples of such coupling agents include titanate-based, aluminum-based, and silane-based coupling agents, These coupling agents can be treated by a method such as dissolving in a solvent and impregnating the vapor growth carbon fiber.

  The compounding amount of the vapor growth carbon fiber is preferably 2 to 30 parts by weight, particularly 2 to 20 parts by weight with respect to 100 parts by weight of the rubber component. If the amount of vapor-grown carbon fiber is too small, the thermal conductivity is not sufficiently improved. On the other hand, if the amount is too large, some mechanical properties such as fatigue properties are lowered, which is not preferable.

  In addition to the above vapor-grown carbon fiber and liquid rubber, fillers such as carbon black and silica can be blended with the rubber composition of the present invention. As the carbon black, known ones such as those of HAF grade can be used, and the blending amount thereof can be in the range of 1 to 90 parts by weight with respect to 100 parts by weight of the rubber component. In addition, additives generally used in the rubber industry, for example, vulcanizing agents, vulcanization accelerators, reinforcing materials, anti-aging agents, softening agents, etc. can be appropriately blended. The product can be suitably used.

  The rubber composition of the present invention can be obtained by mixing and kneading vapor-grown carbon fibers and liquid rubber with rubber components and other compounding components as required. As a mixing method, a known method used for mixing ordinary rubber can be used, and there is no particular limitation. The rubber composition of the present invention is preferably used after being vulcanized. As a crosslinking method, sulfur, a peroxide, a metal oxide or the like is added and crosslinked by heating, or a photopolymerization initiator is used. Examples thereof include a method of adding and crosslinking by light irradiation, and a method of crosslinking by irradiation with an electron beam or radiation.

  The rubber composition of the present invention can improve workability and fatigue resistance without impairing the fracture life, fracture strength, etc. by blending liquid rubber with vapor-grown carbon fibers. It can be used in a wide range of electrical and electronic parts, tires, belts, and other various products.

Hereinafter, the present invention will be described in more detail with reference to examples.
The rubber compositions of Examples and Comparative Examples were prepared with the formulations shown in Table 1 below. First, using a lab plast mill (manufactured by Toyo Seiki Co., Ltd.), NR was masticated at 70 rpm at 60 rpm for 30 seconds, and then the vulcanization accelerators and additives except for sulfur shown in Table 1 below were added. The mixture was further mixed at 70 ° C. at 60 rpm (non-pro blending). Next, after the obtained mixture was taken out, cooled and weighed, a vulcanization accelerator and sulfur were added to the kneaded dough and mixed again at 50 ° C. at 70 ° C. using a lab plast mill (professional blending).

  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. The rupture life and tensile rupture strength of the obtained vulcanized rubber sheet were evaluated according to the following. These results are also shown in Table 1 below.

<Breaking life>
Repeated fatigue tests were performed to determine the number of breaks.

<Tensile breaking strength>
A tensile test was performed to measure the breaking strength (TB).

＊１）昭和電工（株）製 気相法炭素繊維ＶＧＣＦ（登録商標），繊維径０．１５μｍ、繊維長１０〜２０μｍ
＊２）液状ポリイソプレンゴム（ＬＩＲ），実施例１：ＬＩＲ５０（数平均分子量５０，０００），実施例２：ＬＩＲ３０（数平均分子量３０，０００）（いずれも（株）クラレ製）
＊３）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
＊４）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), Showa Denko Co., Ltd., fiber diameter 0.15 μm, fiber length 10-20 μm
* 2) Liquid polyisoprene rubber (LIR), Example 1: LIR50 (number average molecular weight 50,000), Example 2: LIR30 (number average molecular weight 30,000) (all manufactured by Kuraray Co., Ltd.)
* 3) N- (1,3-Dimethylbutyl) -N'-phenyl-P-phenylenediamine * 4) N-cyclohexyl-2-benzothiazyl sulfenamide

  As shown in Table 1 above, by blending a liquid rubber having a predetermined molecular weight with a vapor-grown carbon fiber-blended rubber composition, it is a drawback of the conventional vapor-grown carbon fiber-blended system, such as the fracture life. It was confirmed that the deterioration of mechanical properties can be suppressed.

Claims (4)

  A rubber composition comprising a rubber component and vapor-grown carbon fibers, wherein a liquid rubber having a number average molecular weight of 1,000 to 100,000 is blended.   The rubber composition according to claim 1, wherein the liquid rubber is blended in an amount of 1 to 20 parts by weight per 100 parts by weight of the rubber component.   3. The liquid rubber is at least one selected from the group consisting of polyisoprene, polybutadiene, styrene-butadiene copolymer, styrene-isoprene copolymer, and styrene-butadiene-isoprene copolymer. Rubber composition.   The rubber composition according to any one of claims 1 to 3, wherein the vapor-grown carbon fiber is mixed with 2 to 30 parts by weight with respect to 100 parts by weight of the rubber component.