JP2009091375A - Rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition that can be suitably used for forming a vulcanized rubber having a high modulus of elasticity and excellent ozone resistance without increasing amounts of wax and an anti-aging agent in a rubber composition comprising diene-based rubber as a main component. <P>SOLUTION: The rubber composition comprises 20-100 pts.wt. of epoxidized natural rubber as a rubber component in 100 pts.wt. of the rubber component and 10-120 pts.wt. of carbon black, has an epoxidation ratio of the epoxidized natural rubber of preferably 15-50 mol% and comprises 0.5-5 pts.wt. of sulfur and 0.5-5 pts.wt. of a vulcanization accelerator based on 100 pts.wt. of the rubber component. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a rubber composition containing epoxidized natural rubber and carbon black, and more particularly to a rubber composition from which a rubber having a high elastic modulus and excellent ozone resistance can be obtained by vulcanization. .

  In recent years, rubber products are often used under harsh conditions. In the market, for example, it is required to extend the life of rubber products while achieving functionalization such as high elastic modulus of rubber products. ing. For this reason, improvement in durability of the rubber material itself is strongly demanded. For example, in an anti-vibration rubber product used in an environment exposed to the atmosphere, such as an air suspension or a seismic isolation rubber, it is particularly necessary to improve ozone resistance as durability.

  As a method for improving the ozone resistance of a rubber product, for example, there is a method of adding a large amount of wax or an antioxidant to a rubber composition. However, according to such a method, a problem that the appearance of the rubber product is impaired due to excessive blooming of a part of the anti-aging agent and the wax often occurs. Here, if the amount of the antioxidant or the wax is decreased, the above bloom can be suppressed, but on the other hand, the ozone resistance of the rubber product tends to be lowered.

In the following Patent Document 1, as a rubber composition for tires, an inorganic anti-aging particle having an amine-based anti-aging agent and a specific surface area of 250 m ² / g or more is used with respect to 100 parts by weight of natural rubber and / or diene-based synthetic rubber. It is described that by adding 30 parts by weight, ozone resistance is improved while suppressing bloom of an anti-aging agent. Moreover, in the following patent document 2, it is described that the weather resistance is improved in a pneumatic tire containing an ethylene propylene diene rubber having an iodine value of 24 to 36 as a rubber component.

  Further, in Patent Documents 3 to 4 listed below, rubbers mainly using natural rubber, epoxidized natural rubber, and further non-petroleum resources such as silica are used as a rubber composition that suppresses a compound composed of petroleum resources such as carbon black as much as possible. It is described that, by vulcanizing the composition, a rubber capable of achieving both wet grip performance and low heat build-up can be obtained while maintaining excellent properties such as mechanical properties and abrasion resistance.

However, none of these patent documents suggests a method capable of achieving both high elastic modulus of natural rubber vulcanized rubber and improvement of ozone resistance.
JP 2002-37926 A JP-A-08-231772 JP 2006-70093 A JP 2006-219631 A

  An object of the present invention is to provide a rubber composition from which a vulcanized rubber having a high elastic modulus and excellent ozone resistance can be obtained.

  As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by the rubber composition shown below, and have completed the present invention.

  That is, the rubber composition according to the present invention is characterized by containing 20 to 100 parts by weight of epoxidized natural rubber and 10 to 120 parts by weight of carbon black in 100 parts by weight of the rubber component as rubber components.

  When the vulcanized rubber has a high elastic modulus, its ozone resistance usually tends to deteriorate. However, the rubber composition contains a predetermined amount of epoxidized natural rubber and carbon black, so that the rubber Without increasing the amount of wax or anti-aging agent in the composition, it is possible to achieve both high elastic modulus and improved ozone resistance of the vulcanized rubber.

  The content of the epoxidized natural rubber in the rubber component is 20 to 100 parts by weight, preferably 20 to 70 parts by weight, and more preferably 20 to 60 parts by weight in 100 parts by weight of the rubber component. When the content is less than 20 parts by weight, the vulcanized rubber cannot have a sufficiently high elastic modulus, and in addition, the ozone resistance of the vulcanized rubber is not improved.

  The content of carbon black in the rubber component is 10 to 120 parts by weight, preferably 20 to 80 parts by weight, more preferably 40 to 60 parts by weight with respect to 100 parts by weight of the total rubber components. . If the blending amount is less than 10 parts by weight, the reinforcing effect of carbon black cannot be sufficiently obtained. If the blending amount exceeds 120 parts by weight, exothermic property, rubber mixing property, workability during processing, and the like are deteriorated.

  The content of silica or white filler in the rubber composition according to the present invention is preferably small, and more preferably, silica or white filler is not contained in the rubber composition.

  In the rubber composition, the epoxidation rate of the epoxidized natural rubber is preferably 15 to 50 mol%. When the epoxidation rate of the epoxidized natural rubber is less than 15 mol%, the compatibility with the polymer tends to be reduced, and when it exceeds 50 mol%, the rubber composition tends to gel during kneading. .

  The rubber composition preferably contains 0.5 to 5 parts by weight of sulfur and 0.5 to 5 parts by weight of a vulcanization accelerator with respect to 100 parts by weight of the rubber component. In such a rubber composition, it is possible to further increase the elastic modulus while improving the ozone resistance of the vulcanized rubber.

  In the present invention, at least 20 parts by weight of epoxidized natural rubber is contained in the rubber component. Epoxidized natural rubber can be obtained by epoxidizing natural rubber by, for example, the chlorohydrin method, direct oxidation method, hydrogen peroxide method or the like. As the epoxidized natural rubber, use of a commercially available product is also suitable. Examples of the commercially available product include ENR25 and ENR50 (both manufactured by Mu-ang Mai Guthrie Public Company Limited (Thailand)).

  In addition, you may contain diene rubber as a rubber component in a rubber composition in the range which does not impair the effect which this invention show | plays. Examples of the diene rubber include natural rubber and diene synthetic rubber. Examples of the diene synthetic rubber include chloroprene rubber, isoprene rubber, butadiene rubber, styrene butadiene rubber, butyl rubber, and acrylonitrile butadiene rubber.

  As carbon black, for example, SAF, ISAF, HAF, FEF, GPF and the like are used. Carbon black can be used within a range in which rubber properties such as hardness, reinforcement and low heat build-up of the rubber after vulcanization can be adjusted.

  Sulfur can be used as long as it is normal sulfur for rubber, and its blending amount is 0.5 to 5 parts by weight, preferably 1 to 3 parts by weight with respect to 100 parts by weight of the rubber component. If the amount of sulfur is less than 0.5 parts by weight, the rubber after vulcanization cannot be sufficiently elastic. On the other hand, when the amount exceeds 5 parts by weight, the elastic modulus of the vulcanized rubber becomes too high, so that the ozone resistance is deteriorated. In addition, the scorch time of the rubber composition is accelerated, and the processing stability tends to be deteriorated.

  As the vulcanization accelerator, any ordinary rubber vulcanization accelerator can be used. For example, a sulfenamide vulcanization accelerator, a thiuram vulcanization accelerator, a thiazole vulcanization accelerator, a thiourea system. Vulcanization accelerators such as a vulcanization accelerator, a guanidine vulcanization accelerator, and a dithiocarbamate vulcanization accelerator may be used alone or in appropriate combination. The compounding quantity of a vulcanization accelerator is 0.5-5 weight part with respect to 100 weight part of rubber components, Preferably it is 1-3 weight part. If the blending amount of the vulcanization accelerator is less than 0.5 parts by weight, the rubber after vulcanization cannot sufficiently have a high elastic modulus. On the other hand, when the amount exceeds 5 parts by weight, the elastic modulus of the vulcanized rubber becomes too high, so that the ozone resistance is deteriorated. In addition, the scorch time of the rubber composition is accelerated, and the processing stability tends to be deteriorated.

  In addition, the rubber composition of the present invention, together with the rubber component, carbon black, sulfur and vulcanization accelerator, zinc oxide, magnesium oxide, stearic acid, vulcanization accelerator, vulcanization retarder, organic peroxide, Additives usually used in the rubber industry such as anti-aging agents, softeners such as waxes and oils, processing aids and the like can be appropriately mixed and used as long as the effects of the present invention are not impaired.

  For example, as an anti-aging agent, an aromatic amine-based anti-aging agent, an amine-ketone-based anti-aging agent, a monophenol-based anti-aging agent, a bisphenol-based anti-aging agent, a polyphenol-based anti-aging agent, which are usually used for rubber. Anti-aging agents such as dithiocarbamate-based anti-aging agents and thiourea-based anti-aging agents may be used alone or in admixture as appropriate.

  The rubber composition of the present invention comprises the above rubber component and carbon black, and optionally sulfur, vulcanization accelerator, aroma oil, zinc oxide, stearic acid, wax, anti-aging agent, etc., Banbury mixer, kneader, roll It can be obtained by kneading using a kneader used in the normal rubber industry.

  In addition, the blending method of each of the above components is not particularly limited, and a blending component other than vulcanizing components such as sulfur and a vulcanization accelerator is previously kneaded to obtain a master batch, and the remaining components are added and further kneaded. Any of a method of adding and kneading the components in an arbitrary order, a method of adding all the components simultaneously and kneading may be used.

  By kneading and molding each of the above components, followed by vulcanization, a rubber having a high elastic modulus and excellent ozone resistance can be obtained. Such rubber is suitable for, for example, anti-vibration rubber for automobiles, anti-vibration rubber for railway vehicles, anti-vibration rubber for industrial machinery, seismic isolation rubber for construction, seismic isolation rubber support, etc. Can be used.

  Hereinafter, the present invention will be described in more detail with reference to examples.

(Preparation of rubber composition)
According to the formulation of Table 1, the rubber compositions of Examples 1 to 3 and Comparative Examples 1 and 2 were blended and kneaded using a normal Banbury mixer to prepare a rubber composition. Each compounding agent described in Table 1 is shown below.
a) Natural rubber RSS # 3
b) Epoxidized natural rubber (A) ENR25 (“EPOXYPRENE25”, manufactured by Mu-ang Mai Guthrie Public Company Limit (Thailand))
(B) ENR50 (“EPOXYPRENE50”, manufactured by Mu-ang Mai Guthrie Public Company Limit (Thailand))

c) Butadiene rubber ("BR01", manufactured by JSR)
d) Carbon Black GPF ("Seast V", manufactured by Tokai Carbon Co., Ltd.)
e) Aroma oil ("Process X-140", manufactured by Japan Energy)
f) Zinc oxide ("Zinc Hua 3", manufactured by Mitsui Mining & Mining Co., Ltd.)
g) Stearic acid ("industrial stearic acid", manufactured by Kao Corporation)
h) Wax ("Microcrystalline wax", manufactured by Nippon Seiwa Co., Ltd.))
i) Anti-aging agent N-phenyl-N ′-(1,3-dimethylbutyl) -p-phenylenediamine (“NOCRACK 6C”, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
j) Sulfur ("5% oil-treated sulfur", manufactured by Hosoi Chemical Co., Ltd.)
k) Vulcanization accelerator N-Cyclohexyl 2-benzothiazolylsulfenamide ("Noxeller CZ-G (CZ)", manufactured by Ouchi Shinsei Chemical Co., Ltd.)

(Evaluation)
Evaluation was performed on rubber obtained by heating and vulcanizing each rubber at 150 ° C. for 20 minutes using a predetermined mold.

<Scorch property>
Based on JIS-K 6300-1, Mooney viscosity (ML1 + 4) and scorch time (Sco (t5)) at 125 ° C. were measured.

<Hardness>
Based on JIS-K 6253, the hardness was measured with a type A durometer.

<Tensile properties>
100% elongation modulus (M100 (MPa)), 300% elongation modulus (M300 (MPa)), tensile strength (TB ( MPa)) and elongation (EB (%)).

<Ozone resistance>
According to JIS K6259, the exposure was performed at an atmospheric temperature of 40 ° C., an ozone concentration of 50 pphm, an extension rate of 20%, and exposure for 500 hours. The degree of deterioration was classified and evaluated according to the standards defined by JIS by observing the number and size of cracks. The smaller the alphabet representing the number of cracks, the smaller the number representing the size. Those where no cracks were observed were indicated as “no cracks”. The results are shown in Table 1.

  From the results of Table 1, the vulcanized rubbers of the rubber compositions of Examples 1 to 3 are higher than the vulcanized rubber of the rubber composition of Comparative Example 1 in terms of rubber hardness and modulus. Furthermore, cracks occur after the ozone resistance test in the vulcanized rubber of the rubber composition of Comparative Example 1, but no cracks occur in the vulcanized rubbers of the rubber compositions of Examples 1 to 3. Thus, compared with the vulcanized rubber of the rubber composition of Comparative Example 1, the vulcanized rubbers of the rubber compositions of Examples 1 to 3 have a high elastic modulus and excellent ozone resistance. Recognize. On the other hand, since the rubber composition of Comparative Example 2 contains butadiene rubber instead of the epoxidized natural rubber, it is lower in rubber hardness and modulus than the vulcanized rubber of the rubber composition of Comparative Example 1, and further the rubber. It can be seen that cracks occur after the ozone resistance test despite the increased amount of wax and anti-aging agent in the composition.

Claims (3)

  A rubber composition comprising 20 to 100 parts by weight of epoxidized natural rubber and 10 to 120 parts by weight of carbon black in 100 parts by weight of a rubber component.   The rubber composition according to claim 1, wherein the epoxidized natural rubber has an epoxidation rate of 15 to 50 mol%.   The rubber composition according to claim 1 or 2, comprising 0.5 to 5 parts by weight of sulfur and 0.5 to 5 parts by weight of a vulcanization accelerator with respect to 100 parts by weight of the rubber component.