JP2006152058A - Rubber composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition containing a rubber component consisting of a natural rubber and/or a synthetic diene rubber, especially a rubber composition giving a vulcanized rubber having low density and light weight after vulcanization. <P>SOLUTION: The rubber composition having a density of 0.85-1.20 g/cm<SP>3</SP>after vulcanization is produced by compounding 100 pts.wt. of a rubber component consisting of a natural rubber and/or a synthetic diene rubber with 10-100 pts.wt. of a foamed ethylene-vinyl acetate copolymer having a density of 0.03-0.40 g/cm<SP>3</SP>and containing closed cells having a diameter of ≤5 mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rubber composition containing a rubber component composed of natural rubber and / or a diene synthetic rubber, and in particular, a rubber composition capable of obtaining a lightweight vulcanized rubber having a low density after vulcanization. It is about.

  In general, as a rubber composition capable of obtaining a lightweight vulcanized rubber, for example, a blending ratio of an inorganic filler such as calcium carbonate or a reinforcing agent such as carbon black or white carbon whose density is lower than that of a rubber component. Rubber compositions that reduce the weight of vulcanized rubber after vulcanization by reducing the amount of vulcanized rubber as much as possible are widely known. However, such rubber compositions have a hardness and tensile strength after vulcanization. Since weight reduction is achieved by reducing the blending ratio of inorganic fillers and reinforcing agents blended in order to improve the wear resistance, etc., physical properties, rollability and formability are reduced. In addition, there is a problem that the blending cost increases.

  Therefore, in order to solve such problems, weight reduction was attempted by newly adding a foaming agent to the rubber composition, rather than by reducing the weight by adjusting the blending ratio of inorganic fillers and reinforcing agents. For example, an ethylene / α-olefin / nonconjugated polyene copolymer rubber (A), a polyolefin resin (B), and a foaming agent (C) composed of ethylene, an α-olefin having 3 to 20 carbon atoms, and a nonconjugated polyene. A vulcanizable rubber composition comprising a polyolefin resin (B) microdispersed in a molten state in an ethylene / α-olefin / non-conjugated polyene copolymer rubber (A). The average dispersed particle diameter of (B) is 2 μm or less, and the blend weight ratio of the polyolefin resin (B) and the ethylene / α-olefin / non-conjugated polyene copolymer rubber (A) [(B) / (A )] Is 5/9 Thermal expansion in which a rubber composition (for example, see Patent Document 1) of 50/50 or 100 parts by weight of a diene rubber and a liquid or solid that generates gas by vaporization, decomposition, or chemical reaction by heat is enclosed. Rubber composition comprising 1 to 20 parts by weight of elastic gas-filled thermoplastic resin particles having a particle size of 5 to 300 μm, which is expanded by heat during rubber vulcanization to form a hollow shape. (For example, refer to Patent Document 2).

  However, although such a rubber composition can obtain a lightweight vulcanized rubber having innumerable bubbles after vulcanization by foaming a foaming agent such as thermally expandable thermoplastic resin particles during vulcanization, Since vulcanization and foaming are performed simultaneously when vulcanizing, there is a drawback that it is very difficult to balance vulcanization speed and foaming speed, and this balance is broken even slightly. If this happens, the bubbles may shrink after vulcanization or the size of the bubbles may vary, so the quality is not maintained at a constant level. There was a disadvantage that rubber could not be obtained.

JP 2003-192853 A JP 11-35736 A

  The present invention eliminates the above-mentioned disadvantages of the prior art, and is a rubber composition containing a rubber component made of natural rubber and / or diene-based synthetic rubber, which has a low density and a constant quality especially after vulcanization. It is an object of the present invention to provide a rubber composition from which a certain vulcanized rubber can be easily obtained.

As a result of intensive studies to solve the above problems, the present inventors have found that 100 parts by weight of a rubber component composed of natural rubber and / or a diene synthetic rubber and a foaming density of 0.03 to 0.40 g / cm ^3. In addition, if the rubber composition contains 10 to 100 parts by weight of an ethylene vinyl acetate copolymer-based foam containing closed cells having a particle size of 5 mm or less, the weight after vulcanization is low and the quality is constant. The present invention was completed by investigating that a vulcanized rubber can be easily obtained.

That is, the present invention comprises 100 parts by weight of a rubber component composed of natural rubber and / or diene synthetic rubber, and closed cells having a foaming density of 0.03 to 0.40 g / cm ³ and a particle size of 5 mm or less. A rubber composition comprising 10 to 100 parts by weight of a built-in ethylene-vinyl acetate copolymer foam and having a density after vulcanization of 0.85 to 1.20 g / cm ³ .

Since the rubber composition according to the present invention has the above-described structure, not only can a vulcanized rubber having a low density and a constant quality after vulcanization be obtained, but also the foaming density can be reduced. Vulcanizing a rubber composition containing 10 to 100 parts by weight of an ethylene vinyl acetate copolymer foam containing closed cells having a particle size of 0.03 to 0.40 g / cm ³ and having a particle size of 5 mm or less. Since a lightweight vulcanized rubber is obtained, the balance between the vulcanization speed and the foaming speed is adjusted during vulcanization as in the case of a rubber composition containing a foaming agent that foams conventional thermally expandable thermoplastic resin particles. Therefore, the workability during vulcanization is dramatically higher than that of a rubber composition containing a foaming agent that foams conventional thermally expandable thermoplastic resin particles. Can be improved In addition, a vulcanized rubber having a planned size and density can be easily obtained.

The rubber composition according to the present invention has a foaming density of 0.03 to 0.40 g / cm ³ and a particle size of 5 mm with respect to 100 parts by weight of a rubber component made of natural rubber and / or diene synthetic rubber. Since it contains 10 to 100 parts by weight of ethylene-vinyl acetate copolymer-based foam containing closed cells, the density is lowered without greatly changing the characteristics of general vulcanized rubber after vulcanization. In addition, the weather resistance, heat resistance, heat insulation and slip resistance can be improved as compared with conventional rubber compositions.

  The rubber composition according to the present invention having such excellent characteristics can be suitably used for general rubber products such as rubber plates, rubber sheets and fenders, and particularly its excellent lightness. It can be suitably used as a material for shoe soles, rubber shoe covers, trunks, and the like due to weather resistance, heat deterioration resistance, heat insulation and slip resistance.

Further, an ethylene vinyl acetate copolymer-based foam containing closed cells having a foaming density of 0.03 to 0.40 g / cm ³ and a particle size of 5 mm or less contained in the rubber composition according to the present invention. As for block packing and plate-like general ethylene vinyl acetate copolymer foam used for manufacturing cushion packing, concrete joint materials and shoe soles, etc., pulverized to a particle size of 5 mm or less Therefore, it is possible not only to obtain the ethylene vinyl acetate copolymer foam as a raw material relatively easily, but also, for example, a buffer packing made of ethylene vinyl acetate copolymer foam. , Ethylene vinyl acetate copolymer foams such as cutting scraps and buff powders generated when manufacturing joint joint materials and shoe soles for concrete, etc. If the pulverized product is used, not only can the manufacturing cost of the rubber composition according to the present invention be reduced, but also cutting scraps of these ethylene-vinyl acetate copolymer foams that have been disposed of as industrial waste in the past. Since buff powder etc. can be recycled, it is preferable.

  Hereinafter, each material used for the rubber composition according to the present invention will be described.

  The rubber component used in the present invention is composed of natural rubber (NR) and / or diene synthetic rubber. Examples of the diene synthetic rubber include isoprene rubber (IR), butadiene rubber (BR), and styrene-butadiene. Examples thereof include rubber (SBR), nitrile-butadiene rubber (NBR), chloroprene rubber (CR), and the like, and may be contained in the rubber component in the present invention.

  The rubber component used in the present invention is composed of a mixture of natural rubber and diene synthetic rubber, whether it is composed only of natural rubber or only the above-described diene synthetic rubber. The compounding ratio may be appropriately selected according to the rubber product in which the rubber composition according to the present invention is used.

The ethylene vinyl acetate copolymer foam used in the present invention (hereinafter abbreviated as “EVA foam”) has a foam density of 0.03 to 0.40 g / cm ³ and a particle size of 5 mm or less. In addition to having the function of reducing the weight of the rubber composition according to the present invention, the rubber composition according to the present invention has weather resistance, heat deterioration resistance, thermal insulation and anti-slip properties. Give.

  The EVA foam used in the present invention is contained in an amount of 10 to 100 parts by weight, particularly preferably 25 to 30 parts by weight, per 100 parts by weight of the rubber component. If the EVA foam is less than 10 parts by weight, the weight reduction rate of the rubber composition as a whole according to the present invention will be low. On the other hand, if the EVA foam exceeds 100 parts, it is contained in the EVA foam. This is not preferable because an abnormal foaming phenomenon due to a residual foaming agent that may occur may occur, the tensile strength and elongation decrease significantly, and the rollability and formation deteriorate.

The EVA foam used in the present invention has a foam density of 0.03 to 0.40 g / cm ³ , and the EVA foam having a foam density in such a range is used for cushioning packing and joint for concrete. It is commonly used as block or plate-like EVA foam used when manufacturing materials, shoe soles, etc., so it is relatively available as cutting scrap or buff powder generated when these are produced. It is easy to do. When the foaming density is less than 0.03 g / cm ³ , the bulk is large and the workability is significantly reduced. Also, when kneaded, the strength of the shell is weak and shell destruction occurs frequently, so that the filling efficiency is significantly reduced. It is not preferable, and if it exceeds 0.40 g / cm ³ , more EVA foam must be contained in order to reduce the weight by the amount of high foam density, and the content of EVA foam increases. And the rubber composition is not preferable because the formability of the rubber composition and the sheet rollability are significantly lowered.

  The EVA foam used in the present invention is required to have a particle size of 5 mm or less. As the EVA foam, an EVA foam such as a block shape or a plate shape may be used in advance. Even when using a material pulverized to 5 mm or less, or when kneading and kneading the rubber composition according to the present invention with a kneader or the like, only EVA type foam such as block or plate is used as a kneader. It may be obtained by pulverizing so that the particle size is 5 mm or less. Further, only EVA foam such as block or plate is introduced into the kneader and the particle size is 5 mm or less. In this way, an equal weight of a rubber component previously pulverized and then kneaded in a kneader and mixed and kneaded may be used as a master batch of an EVA foam and a rubber component.

  The EVA-based foam used in the present invention is basically formed by heating and foaming an ethylene vinyl acetate copolymer and a foaming agent. As the ethylene vinyl acetate copolymer, Are preferably used with a vinyl acetate content of about 10 to 70%, and as the blowing agent, for example, azo compounds such as azodicarboxylic acid amide (ADCA) and azobisisobutyronitrile (AIBN), P A sulfonylhydrazide compound such as P′-oxybisbenzenesulfonylhydrazide (OBSH), a nitroso compound such as dinitrosopentamethylenetetramine (DPT), or a mixture of two or more of them is preferably used.

  In addition to the ethylene vinyl acetate copolymer and the foaming agent, the EVA foam used in the present invention may be, for example, magnesium hydroxide, aluminum hydroxide, calcium hydroxide, hydrotalcite, carbonic acid as necessary. Inorganic fillers such as calcium and zinc borate, metal soaps, metal oxides, urea compounds, foam regulators such as acid anhydrides and organic acids, crosslinking agents, antioxidants, light stabilizers, antistatic agents, pigments , Flame retardants, anti-aging agents, processability improvers and the like may be added.

In addition to the rubber component and EVA foam, the rubber composition according to the present invention usually contains a crosslinking agent such as sulfur, and further, for example, zinc white or stearic acid. Vulcanization aids, vulcanization accelerators such as guanidine compounds and dithiocarbamate compounds, fillers such as carbon black, silica, clay, alumina, calcium carbonate, magnesium carbonate, aluminum hydroxide, aluminum silicate, magnesium oxide, Additives commonly used for rubber such as white fillers such as titanium oxide and white carbon (silicon dioxide), activators, processing aids, softeners, anti-aging agents, flame retardants, colorants, antistatic agents The agent may be appropriately contained to such an extent that the density after vulcanization is in the range of 0.85 to 1.20 g / cm ³ .

  EXAMPLES Hereinafter, although the rubber composition which concerns on this invention is demonstrated concretely based on an Example, this invention is not limited at all by these Examples.

In addition, the component used in each Example and / or Comparative example is as follows.
Natural rubber: RSS No. 1
Butadiene rubber: JSR BR01 made by JSR
Styrene butadiene rubber: JSR SBR1507 manufactured by JSR
EVA foam: EVA foam having a foam density of 0.15 g / cm ³ using an ethylene vinyl acetate copolymer having a vinyl acetate content of 15% and an MFR (melting index) of 1.4 as a main raw material Crosslinking agent: Hosoi Chemical 200 mesh powder sulfur Zinchua No. 3 manufactured by Kogyo Co., Ltd .: Zinc Hua No. 3 (Zinc Oxide) manufactured by Shodo Chemical Co., Ltd.
Transparent zinc white: Transparent zinc white (zinc carbonate) manufactured by Shodo Chemical Industry Co., Ltd.
Vulcanization accelerator (DM): Sunseller DM (dibenzothiazyl disulfide) manufactured by Sanshin Chemical Industry Co., Ltd.
Vulcanization accelerator (D): Sunseller D (N, N'-diphenyl guanidine) manufactured by Sanshin Chemical Industry Co., Ltd.
Vulcanization accelerator (TS): Sunseller TS (tetramethylthiuram monosulfide) manufactured by Sanshin Chemical Industry Co., Ltd.
Activator: Nippon Shokubai's DEG (diethylene glycol)
White filler (white carbon): Toku Seal GU manufactured by Tokuyama Corporation
White filler (heavy calcium carbonate): NS-100 manufactured by Nitto Flour Chemical Co., Ltd.
White filler (fatty acid-treated calcium carbonate): Shiroishi Hana CC manufactured by Shiroishi Chemical Co., Ltd.
White filler (aluminum silicate): Crown clay made by Southeastern Corporation White filler (baked aluminum silicate): Burgess Iceberg made by Burgess White filler (light calcium carbonate): Silver W made by Shiroishi Chemical Co., Ltd.
Anti-aging agent: BHT (2,6-di-tert-butyl-4-methylphenol) manufactured by Kawaguchi Chemical Industry Co., Ltd.
Processing aid: Quinton A100 (Synthetic polyterpene resin) manufactured by Nippon Zeon
Softener: Comorex H22 (naphthenic oil) manufactured by Nippon Oil Corporation
Stearic acid: Stearic acid manufactured by NOF Corporation Pigment: Bigotech Blue BS Pure (phthalo cyanine blue) manufactured by Sanyo Dye

Moreover, each measuring method in each Example and / or Comparative Example is as follows.
・ Measurement method of vulcanized rubber density According to “Method A” in JIS K6268 “vulcanized rubber-density measurement”, a 3 g test piece was punched out from the vulcanized rubber, and this test piece was chemically treated under an atmosphere of 23 ± 2 ° C. The density was measured with a balance (manufactured by Tsushima Seisakusho).
・ Measurement method of tensile strength and elongation at break of vulcanized rubber According to JISK6251 “Tensile test method of vulcanized rubber”, a tensile test was performed at a measurement temperature of 23 ± 2 ° C. and a tensile speed of 500 ± 50 mm / min. Strength (TB) and elongation at break (EB) were measured.
-Hardness measurement method of vulcanized rubber According to JISK6253 "Hardness test method of vulcanized rubber and thermoplastic rubber", hardness was measured with a type A durometer.
-Measurement method of vulcanized rubber wear amount According to JISK 6264 "Vulcanized rubber wear test method", it was rotated 500 times with an Akron abrasion tester, and the wear amount was measured. This measurement was performed only for Example 1 and Comparative Example 1.
・ Measurement method of tensile strength and aging residual ratio of elongation at break and hardness change of vulcanized rubber According to JISK6257 “Aging test method of vulcanized rubber”, temperature 70 ± 1 ° C., 96 hours (accuracy is 0 -2 hours) was subjected to an air heating aging test, and the tensile strength, the aging residual ratio of elongation at break, and the change in hardness were measured.

Example 1 and Comparative Example 1
In Example 1, a vulcanized rubber was prepared by the following procedure using the components of the rubber composition shown in Table 1 below. In addition, the unit in the component of the rubber composition shown in following Table 1 is a weight part.
First, the whole rubber component consisting of natural rubber and butadiene rubber previously masticated to a viscosity of 50 to 60 is put into a kneader and masticated at 80 to 85 ° C. for 1 minute, and then the particle size is 3 mm in advance. The whole amount of the EVA foam pulverized below was charged and mixed and kneaded at 85 to 90 ° C. for 3 minutes. Next, after adding all the pigment, vulcanization accelerator and transparent zinc white and mixing and kneading at 85 to 90 ° C. for 3 minutes, all the activator, white filler and processing aid are added and half of stearic acid is added. The mixture is kneaded at 85 to 90 ° C. for 3 minutes, and then discharged from the damper. Next, the entire amount of the crosslinking agent and the remainder of stearic acid were mixed with the components discharged using an open roll at 70 to 80 ° C. for 5 minutes, and then vulcanized by press vulcanization at 150 ° C. for 10 minutes. Obtained.
In Comparative Example 1, except that the EVA-based foam charging procedure in Example 1 was not performed using the components of the rubber composition shown in Table 1 below, and Zinc Hana 3 was added instead of transparent zinc white Prepared vulcanized rubber by the same procedure as in Example 1.
Then, the density, tensile strength and elongation at break, hardness, wear amount, tensile strength and aging residual ratio of elongation at break, and change in hardness of the manufactured Example 1 and Comparative Example 1 were changed by the above methods. The measurement results are also shown in Table 1 below.

Example 2 and Comparative Example 2
In Example 2, a vulcanized rubber was prepared by the following procedure using the components of the rubber composition shown in Table 2 below. In addition, the unit in the component of the rubber composition shown in following Table 2 is a weight part.
First, the whole rubber component made of natural rubber and styrene butadiene rubber previously masticated to a viscosity of 50 to 60 is put into a kneader and masticated at 80 to 85 ° C. for 1 minute. The whole EVA foam pulverized to 3 mm or less was added and mixed and kneaded at 85 to 90 ° C. for 3 minutes. Next, after adding all the pigment, vulcanization accelerator, and transparent zinc white, mixing and kneading at 85 to 90 ° C. for 3 minutes, all the active agent, white filler, processing aid, anti-aging agent and softening agent are added. At the same time, half of the stearic acid is added and mixed and kneaded at 85 to 90 ° C. for 3 minutes, and then discharged from the damper. Next, the entire amount of the crosslinking agent and the remainder of stearic acid were mixed with the components discharged using an open roll at 70 to 80 ° C. for 5 minutes, and then vulcanized by press vulcanization at 150 ° C. for 10 minutes. Obtained.
In Comparative Example 2, the procedure for introducing the EVA foam in Example 2 was not performed using the components of the rubber composition shown in Table 2 below, the activator and the processing aid were not added, and transparent zinc Vulcanized rubber was prepared in the same procedure as in Example 2, except that Zinc Hana 3 was added instead of Hana.
And as a result of measuring density change, tensile strength and elongation at break, hardness, tensile strength and aging residual ratio of elongation at break, and change of hardness for the manufactured Example 2 and Comparative Example 2 Are also shown in Table 2 below.

As is apparent from the results in Tables 1 and 2, ethylene-vinyl acetate copolymer foaming with closed cells having a foaming density of 0.03 to 0.40 g / cm ³ and a particle size of 5 mm or less. The rubber composition according to the present invention containing a body has a remarkably low density after vulcanization as compared with a conventional rubber composition and is greatly reduced in weight, and also has a tensile strength and elongation at break. Since the aging residual rate and the change in hardness are improved, its durability is also improved.

Claims (1)

Ethylene vinyl acetate containing 100 parts by weight of a rubber component made of natural rubber and / or diene synthetic rubber, and closed cells having a foaming density of 0.03 to 0.40 g / cm ³ and a particle size of 5 mm or less A rubber composition comprising 10 to 100 parts by weight of a copolymer-based foam and having a density after vulcanization of 0.85 to 1.20 g / cm ³ .