JP2022078429A - Production method of rubber composition - Google Patents

Abstract

To provide a production method of a rubber composition excellent in productivity, and capable of obtaining a rubber molded product remarkably reduced in failures such as bubbles caused by dispersion failures, scratches, and residues of a compounding agent.SOLUTION: A production method of a rubber composition includes: a wet pulverization step of obtaining a pasty mixture by performing wet pulverization treatment of adding a plasticizer to at least one kind of a powder material selected from the group consisting of a vulcanizer and a vulcanization accelerator; and a kneading step of obtaining a rubber composition by kneading at least rubber and the pasty mixture.SELECTED DRAWING: None

Description

The present invention relates to a method for producing a rubber composition. The present invention also relates to a method for producing a rubber molded product obtained by vulcanizing the rubber composition.

Among the compounding agents such as the vulcanization accelerator added to the rubber composition, those having high cohesiveness are known. When such a highly cohesive vulcanization accelerator is kneaded with rubber, there is a problem that dispersion is poor and defects such as residual compounding agent occur in the rubber molded product obtained by molding. Patent Document 1 describes a method for preparing a vulcanization accelerator in which a plasticizer is added to a guanidine compound to melt guanidine and then to make a paste, as a method for improving such dispersion defects. According to this, it is said that defects caused by poor dispersion of the vulcanization accelerator can be completely prevented in the kneading process, the molding process and the like.

JP-A-2002-309040

However, in Patent Document 1, since the guanidine compound is melted at a high temperature higher than the melting point, there is a problem in productivity, and it cannot be applied to a compounding agent which is difficult to melt, and a rubber composition that can solve the problem. There was a demand for a manufacturing method for.

The present invention has been made to solve the above problems, and is a rubber having excellent productivity, which can obtain a rubber molded product in which defects such as bubbles, scratches, and residue of compounding agent due to poor dispersion can be remarkably reduced. It is an object of the present invention to provide a method for producing a composition.

The above-mentioned problem is a method for producing a rubber composition, which is a paste-like mixture obtained by adding a plasticizer to at least one powder material selected from the group consisting of a vulcanizing agent and a vulcanization accelerator and performing a wet pulverization treatment. It is solved by providing a method for producing a rubber composition, which comprises a wet pulverization step for obtaining a rubber composition and a kneading step for kneading at least the rubber and the paste-like mixture to obtain a rubber composition.

At this time, it is preferable that the mixing ratio of the powder material and the plasticizer in the paste-like mixture is 1: 0.5 to 1:20. It is a preferable embodiment to mix 0.1 to 100 parts by mass of the paste-like mixture with 100 parts by mass of the rubber. The rubber is from chloroprene rubber (CR), nitrile rubber (NBR), vulcanized nitrile rubber (HNBR), ethylene propylene rubber (EPDM), acrylic rubber (ACM), ethylene acrylic rubber (AEM) and sulfur rubber (FKM). It is preferable that the vulcanizing agent is at least one selected from the group consisting of sulfur and amine-based vulcanizing agents, and it is preferable that the vulcanizing agent is at least one selected from the group consisting of sulfur and amine-based vulcanizing agents. It is preferable that the vulcanization accelerator is at least one selected from the group consisting of a thiuram-based vulcanization accelerator, a guanidine-based vulcanization accelerator, a dithiocarbamate-based vulcanization accelerator, and a thiazole-based vulcanization accelerator. .. The maximum particle size of the particles contained in the paste-like mixture is preferably 80 μm or less, and the average particle size of the particles contained in the paste-like mixture is preferably 0.1 to 30 μm.

In the kneading step, it is a preferable embodiment to further add a second plasticizer and knead, and a method for producing a rubber molded product having a vulcanization step of vulcanizing the rubber composition obtained in the kneading step. Is a preferred embodiment. It is also a preferred embodiment that the rubber molded product is a sealing member.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for producing a rubber composition having excellent productivity, which can obtain a rubber molded product in which defects such as bubbles, scratches and residue of a compounding agent due to poor dispersion can be remarkably reduced.

In the present invention, a plasticizer (hereinafter, may be referred to as "first plasticizer") is added to at least one powder material selected from the group consisting of a vulcanizing agent and a vulcanization accelerator, and a wet pulverization treatment is performed. A wet crushing step of obtaining a paste-like mixture (hereinafter, may be abbreviated as "wet crushing step") and a kneading step of kneading at least rubber and the paste-like mixture to obtain a rubber composition (hereinafter, referred to as "wet crushing step"). It is a method for producing a rubber composition having (sometimes abbreviated as "kneading step").

As can be seen from the comparison between Examples and Comparative Examples described later, in Comparative Examples in which rubber was kneaded with a vulcanizing agent or a powder of a vulcanization accelerator, the defect rate (%) due to poor dispersion was found. It became above a certain level, and defects such as air bubbles, scratches, and residue of the compounding agent were observed in the obtained rubber molded product. On the other hand, in the example in which the wet pulverization step was adopted, the defect rate (%) due to the dispersion defect was 0%, and defects such as bubbles, scratches, and compounding agent residue were not observed in the obtained rubber molded product. rice field. That is, by adopting a wet pulverization step of adding a plasticizer to at least one powder material selected from the group consisting of a vulcanizing agent and a vulcanization accelerator and performing a wet pulverization treatment to obtain a paste-like mixture, the rubber and rubber can be obtained. In the kneading step of kneading the paste-like mixture to obtain a rubber composition, dispersibility is improved, and it is possible to provide a rubber molded product in which defects such as bubbles, scratches, and residue of a compounding agent due to poor dispersion are significantly reduced. It became clear. As described above, by adopting the wet pulverization step, a paste-like mixture can be obtained with good productivity without melting the powder material even when the melting point of the powder material is very high, and thus the significance of the present invention is great. You can see that. In the present specification, "air bubbles, scratches, and residual compounding agent" are caused by at least one compounding agent selected from the group consisting of a vulcanizing agent and a vulcanization accelerator.

The powder material used in the present invention is at least one selected from the group consisting of vulcanizing agents and vulcanization accelerators. The vulcanizing agent used in the present invention is not particularly limited, but is preferably at least one selected from the group consisting of sulfur and amine-based vulcanizing agents such as hexamethylenediamine carbamate (HMDC). The vulcanization accelerator used in the present invention is not particularly limited, and is a sulfurum-based vulcanization accelerator such as tetramethylthium disulfide; a guanidine-based vulcanization accelerator such as 1,3-di-o-tolylguanidine; dibutyldithiocarbamine. Examples thereof include a dithiocarbamate-based vulcanization accelerator such as zinc acid acid; a thiazole-based vulcanization accelerator such as 2-mercaptobenzothiazole; and the like. The vulcanization accelerator is preferably at least one selected from the group consisting of a sulfur-based vulcanization accelerator, a guanidine-based vulcanization accelerator, a dithiocarbamate-based vulcanization accelerator, and a thiazole-based vulcanization accelerator. .. As the powder material for the wet pulverization treatment, it is a preferable embodiment to consist of only a vulcanizing agent, and among them, hexamethylenediamine carbide (HMDC) is preferably adopted.

The plasticizer used in the present invention is not particularly limited as long as it is blended in rubber, and is phthalic acid-based such as dioctylphthalate; adipic acid-based such as dioctyl adipate; sebasic acid-based such as dibutyl sebacate; tori. Trimeritic acid-based merit acid such as trimethyl acid; Polyester-based such as adipic acid-based polyester and phthalic acid-based polyester; Polyether ester-based such as phthalic acid ether ester and phthalic acid ether ester; Phosphic acid-based such as trioctyl phosphate; Petroleum Examples include system hydrocarbons. These plasticizers can be used alone or in combination of two or more. Among them, at least one plasticizer selected from the group consisting of phthalic acid type, adipic acid type, polyester type, polyether ester type and phosphoric acid type is preferably used.

In the wet pulverization step of the present invention, a paste-like mixture is obtained by adding the plasticizer to the powder material and performing a wet pulverization treatment. As an apparatus used for the wet pulverization treatment, a known wet pulverizer such as a ball mill, a bead mill, a raikai machine, or a jet mill can be used. The blending ratio (mass ratio) of the powder material and the plasticizer is preferably 1: 0.5 to 1:20. The compounding ratio is more preferably 1: 1 to 1:18, and even more preferably 1: 1.5 to 1:15.

In the present invention, it is a preferable embodiment that the maximum particle size of the particles contained in the paste-like mixture is 80 μm or less. When the maximum particle size exceeds 80 μm, defects such as bubbles, scratches, and residue of the compounding agent due to poor dispersion may occur in the obtained rubber molded product, and the maximum particle size is more preferably 70 μm or less. It is more preferably 40 μm or less, and particularly preferably 30 μm or less. The maximum particle size of the particles contained in the paste-like mixture is usually 3 μm or more. The maximum particle size in the present specification is a reading of a value indicating the maximum particle size in the volume-based particle size distribution.

In the present invention, it is a preferable embodiment that the average particle size of the particles contained in the paste-like mixture is 0.1 to 30 μm. When the average particle size is less than 0.1 μm, it may take time to prepare the paste-like mixture, and the average particle size is more preferably 0.5 μm or more, further preferably 1 μm or more. It is particularly preferably 5 μm or more. On the other hand, when the average particle size exceeds 30 μm, the obtained rubber molded product may have defects such as bubbles, scratches, and compounding agent residue due to poor dispersion, and the average particle size is more preferably 20 μm or less. It is more preferably 15 μm or less, and particularly preferably 12 μm or less. The average particle size in the present specification is the particle size when the volume-based integrated value determined based on the volume-based particle size distribution is 50%.

In the present invention, after the wet pulverization step, at least a kneading step of kneading the rubber and the paste-like mixture to obtain a rubber composition is performed. The rubber used in the kneading step is not particularly limited, and is limited to chloroprene rubber (CR); nitrile rubber of nitrile rubber (NBR) and hydride nitrile rubber (HNBR); ethylene propylene rubber (EPDM); acrylic rubber (ACM), ethylene. Acrylic rubber such as acrylic rubber (AEM); fluororubber (FKM); and the like can be mentioned. Among them, a group consisting of chloroprene rubber (CR), nitrile rubber (NBR), hydrided nitrile rubber (HNBR), ethylene propylene rubber (EPDM), acrylic rubber (ACM), ethylene acrylic rubber (AEM) and fluorine rubber (FKM). At least one selected from the group consisting of nitrile rubber (NBR), hydrided nitrile rubber (HNBR), acrylic rubber (ACM) and ethylene acrylic rubber (AEM). It is more preferable to have.

The chloroprene rubber (CR) is not particularly limited, and any rubber containing 2-chloro-1,3-butadiene as a main component may be used. 2-Chloro-1,3-butadiene may be polymerized alone, or 2-chloro-1,3-butadiene may be copolymerized with another monomer. As the other monomer, acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, and methoxyethyl acrylate are preferably used.

The nitrile rubber is not particularly limited, and a copolymer of acrylonitrile and 1,3-butadiene can be used. Addition of hydrogen to the double bond remaining in the 1,3-butadiene unit after polymerization is optional. Non-hydrogenated nitrile rubber (NBR) and hydrogenated nitrile rubber (HNBR) can be preferably used. The content of the acrylonitrile unit in the nitrile rubber is preferably 15 to 50% by mass. A structural unit derived from another copolymerizable monomer may be contained as long as the effect of the present invention is not impaired, but the content thereof is usually 10% by mass or less, preferably 5. It is less than mass%.

The ethylene propylene rubber (EPDM) is not particularly limited, and a copolymer of ethylene, propylene and a diene compound can be used. Examples of the diene compound contained in EPDM include ethylidene norbornene (ENB), 1,4-hexadiene, dicyclopentadiene and the like. A structural unit derived from another copolymerizable monomer may be contained as long as the effect of the present invention is not impaired, but the content thereof is usually 10% by mass or less, preferably 5. It is less than mass%.

The acrylic rubber is not particularly limited, and any rubber containing acrylic acid ester as a main component may be used. As the acrylic acid ester, methyl acrylate, ethyl acrylate, butyl acrylate, methoxyethyl acrylate and the like are preferably used. Examples of the monomer copolymerized with the acrylic acid ester include acrylonitrile and ethylene. Specifically, acrylic rubber (ACM) obtained by copolymerizing two or more kinds of acrylic acid esters selected from methyl acrylate, ethyl acrylate, butyl acrylate and methoxyethyl acrylate and a crosslinkable monomer, and acrylic. Acrylic rubber (AEM) obtained by copolymerizing methyl acrylate, ethylene and a crosslinkable monomer is preferably used. As AEM, "VAMAC" (registered trademark) of DuPont is available. A structural unit derived from another copolymerizable monomer may be contained as long as the gist of the present invention is not impaired, but the content thereof is usually 10% by mass or less, preferably 5. It is less than mass%.

The fluororubber (FKM) is not particularly limited, and is a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), a polymer of VDF and trichlorofluoroethylene (CTFE), VDF, HFP and tetra. Polymers with fluoroethylene (TFE), copolymers with TFE and propylene, copolymers with TFE and fluorovinyl ether, copolymers with hydrocarbon-based diene monomer and fluorine-containing monomer, etc. Is exemplified. Among them, a ternary fluororubber which is a copolymer of VDF, HFP and tetrafluoroethylene (TFE) is preferably used. A structural unit derived from another copolymerizable monomer may be contained as long as the effect of the present invention is not impaired, but the content thereof is usually 10% by mass or less, preferably 5. It is less than mass%.

In the kneading step, it is a preferable embodiment to mix 0.1 to 100 parts by mass of the paste-like mixture with 100 parts by mass of the rubber. If the blending amount is less than 0.1 parts by mass, the performance of the vulcanizing agent or the vulcanization accelerator may not be obtained, and it is more preferably 0.2 parts by mass or more, and 0.5 parts by mass or more. It is more preferably present, and particularly preferably 0.8 parts by mass or more. On the other hand, when the compounding amount exceeds 100 parts by mass, the progress of vulcanization may be accelerated, and it is more preferably 80 parts by mass or less, further preferably 60 parts by mass or less, and 40 parts by mass or less. Is particularly preferable.

In the kneading step, the method of kneading the rubber and the paste-like mixture is not particularly limited, but kneading can be performed using a roll, a kneader, a Banbury mixer, an intermix, an extruder or the like. The temperature of the rubber composition at the time of kneading is preferably 20 to 170 ° C.

In the kneading step, it is a preferable embodiment to add a filler such as a white filler and carbon black. The white filler used in the present invention is not particularly limited, and silica, clay, calcium carbonate, diatomaceous earth, wollastonite and the like can be used. The carbon black used in the present invention is not particularly limited, and FEF, SRF, SAF, ISAF, HAF, MAF, GPF, FT, MT and the like can be used. The blending amount of the white filler or carbon black is preferably 1 to 200 parts by mass, more preferably 10 to 90 parts by mass with respect to 100 parts by mass of the rubber.

In the kneading step, it is also a preferable embodiment to further add a second plasticizer and knead. The total blending amount of the first plasticizer and the second plasticizer is preferably 1 to 100 parts by mass with respect to 100 parts by mass of the rubber. The second plasticizer may be the same as or different from the first plasticizer used in the wet grinding step. Further, in the present embodiment, the required amount of the plasticizer for 100 parts by mass of the rubber is blended in two portions as the first plasticizer and the second plasticizer, but in the wet pulverization step, the powder material is blended. A paste-like mixture may be obtained by adding a required amount of a plasticizer and performing a wet pulverization treatment. In this case, it is not necessary to add the second plasticizer in the kneading step.

In the kneading step, various vulcanization aids, antiaging agents, processing aids, acid receiving agents, coloring agents, fillers and the like, which are usually used in rubber compositions, are used as long as the effects of the present invention are not impaired. Combination agents can be included.

A rubber molded product can be suitably obtained by performing a vulcanization step of vulcanizing the rubber composition obtained in the kneading step. In the vulcanization step, the rubber composition is formed into a desired shape, and the cross-linking reaction (vulcanization) proceeds by heating. Examples of the molding method of the rubber composition include injection molding and compression molding. The crosslinking temperature is usually 100 to 250 ° C. The cross-linking time is usually 0.5 minutes to 24 hours. Further heating may be performed for secondary cross-linking.

It is preferable that the rubber molded product obtained in the present invention is a sealing member. Suitable sealing members are packings, seals, gaskets, O-rings and diaphragms. Specifically, examples of the seal include a bearing seal and an oil seal, and examples of the gasket include a gasket for an intake manifold and a gasket for a head cover.

The raw materials used in Example 1 and Comparative Example 1 below are as follows.
[material]
-Nitrile rubber (NBR): "Nipol 1042" manufactured by Zeon Corporation
-Carbon black: "Seast 3 (HAF)" manufactured by Tokai Carbon Co., Ltd.
-Plasticizer: "DOP" manufactured by ADEKA CORPORATION
・ Processing aid: "Stearic acid" manufactured by J-PLUS Co., Ltd.
・ Zinc oxide: "ZINCA # 20" manufactured by Sakai Chemical Industry Co., Ltd.
-Vulcanizing agent: "Fine powder sulfur 500 Mesh" manufactured by Hosoi Chemical Industry Co., Ltd.
-Vulcanization accelerator: "ACCEL PZ" manufactured by Kawaguchi Chemical Industry Co., Ltd. Zinc dimethyldithiocarbamate

Example 1
By putting 0.5 parts by mass of plasticizer and 0.5 parts by mass of vulcanizing agent powder (average particle size: 50 μm, maximum particle size: 175 μm) into a wet crusher and performing wet crushing treatment at room temperature for 1 hour. A paste-like mixture was obtained. When the particle size of the particles contained in the paste-like mixture was measured using the particle size distribution measuring device of "LA-950" manufactured by HORIBA, Ltd., the average particle size was 15 μm and the maximum particle size was 70 μm. rice field. 1 part by mass of the paste-like mixture, 65 parts by mass of carbon black, 14.5 parts by mass of a plasticizer, 1 part by mass of a processing aid, and 5 parts by mass of zinc flower with respect to 100 parts by mass of nitrile rubber (NBR). Parts and a vulcanization accelerator were kneaded together with 0.3 parts by mass at 70 ° C. using an open roll to prepare an unvulcanized rubber dough. The obtained unvulcanized rubber dough was vulcanized at 170 ° C. for 10 minutes using an injection molding machine and molded to obtain a gasket as a molded product. The obtained gasket was observed with a magnifying glass, and the defect rate (%) due to poor dispersion was calculated. The defect rate (%) due to poor dispersion represents the ratio of the number of confirmed defects (air bubbles, scratches, residual compounding agent) to the number of molded products. The results are summarized in Table 1.

Comparative Example 1
In Example 1, instead of obtaining a paste-like mixture, 0.5 parts by mass of vulcanizing agent powder (average particle size: 50 μm, maximum particle size: 175 μm) was added to 100 parts by mass of nitrile rubber (NBR). Knead with 65 parts by mass of carbon black, 15 parts by mass of plasticizer, 1 part by mass of processing aid, 5 parts by mass of zinc flower, and 0.3 parts by mass of vulcanization accelerator at 70 ° C using an open roll. A gasket, which is a molded product, was obtained in the same manner as in Example 1. In the same manner as in Example 1, the obtained gasket was observed with a magnifying glass, and the defect rate (%) due to poor dispersion was calculated. The results are summarized in Table 1.

The raw materials used in Example 2 and Comparative Example 2 below are as follows.
[material]
-Acrylic rubber (ACM): "AR12" manufactured by Zeon Corporation
-Carbon black: "Seast 3 (HAF)" manufactured by Tokai Carbon Co., Ltd.
-Plasticizer: "ADEKA SIZER RS1000" manufactured by ADEKA CORPORATION
-Processing aid a: "Stearic acid" manufactured by NOF CORPORATION
-Processing aid b: "Greg G8205" manufactured by NI Chemitec Co., Ltd.
・ Anti-aging agent: "Nowguard 445" manufactured by Shiraishi Calcium Co., Ltd.
・ Vulcanization accelerator: “Noxeller DT” manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd. 1,3-di-o-tolylguanidine ・ Vulcanization agent: “Diak No. 1” manufactured by Chemours Co., Ltd. Hexamethylenediamine carbamate (HMDC)

Example 2
Put 2 parts by mass of plasticizer and 0.5 parts by mass of vulcanizing agent powder (average particle size: 50 μm, maximum particle size: 500 μm) into a wet crusher, and perform wet crushing treatment at room temperature for 1 hour to form a paste. A mixture was obtained. When the particle size of the particles contained in the paste-like mixture was measured using the particle size distribution measuring device of "LA-950" manufactured by HORIBA, Ltd., the average particle size was 3 μm and the maximum particle size was 25 μm. rice field. 2.5 parts by mass of the pasty mixture, 60 parts by mass of carbon black, 8 parts by mass of plasticizer, 1 part by mass of processing aids a and b, and aging with respect to 100 parts by mass of acrylic rubber (ACM). An unvulcanized rubber dough was prepared by kneading the inhibitor with 1 part by mass and the vulcanization accelerator with 2.0 parts by mass at 70 ° C. using an open roll. The obtained unvulcanized rubber dough was vulcanized at 170 ° C. for 10 minutes using an injection molding machine and molded to obtain a gasket as a molded product. In the same manner as in Example 1, the obtained gasket was observed with a magnifying glass, and the defect rate (%) due to poor dispersion was calculated. The results are summarized in Table 2.

Comparative Example 2
In Example 2, instead of obtaining the paste-like mixture, 0.5 parts by mass of the vulcanizing agent powder (average particle size: 50 μm, maximum particle size: 500 μm) was added to 100 parts by mass of acrylic rubber (ACM). 60 parts by mass of carbon black, 10 parts by mass of plasticizer, 1 part by mass of processing aids a and b, 1 part by mass of anti-aging agent, and 2.0 parts by mass of vulcanization accelerator open at 70 ° C. A gasket, which is a molded product, was obtained in the same manner as in Example 2 except that the mixture was kneaded using a roll. In the same manner as in Example 1, the obtained gasket was observed with a magnifying glass, and the defect rate (%) due to poor dispersion was calculated. The results are summarized in Table 2.

The raw materials used in Example 3 and Comparative Example 3 below are as follows.
[material]
-Acrylic rubber (ACM): "AR51" manufactured by Zeon Corporation
-Carbon black: "Seast 3 (HAF)" manufactured by Tokai Carbon Co., Ltd.
-Plasticizer: "ADEKA SIZER RS1000" manufactured by ADEKA CORPORATION
-Processing aid a: "Stearic acid" manufactured by NOF CORPORATION
-Processing aid b: "Greg G8205" manufactured by NI Chemitec Co., Ltd.
・ Anti-aging agent: "Nowguard 445" manufactured by Shiraishi Calcium Co., Ltd.
-Vulcanization accelerator a: "Noxeller PZ" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Zinc dimethyldithiocarbamate-Vulcanization accelerator b: "Noxeller TTFE" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanizer: "Bull Current E / C" manufactured by Rankses Co., Ltd. N-phenyl-N- (trichloromethylsulphenyl) benzenesulfonamide

Example 3
2.5 parts by mass of plasticizer and 2.5 parts by mass of powder of vulture accelerator a (average particle size: 40 μm, maximum particle size: 300 μm) are put into a wet crusher, and wet crushing treatment is performed at room temperature for 1 hour. This gave a paste-like mixture. When the particle size of the particles contained in the paste-like mixture was measured using the particle size distribution measuring device of "LA-950" manufactured by HORIBA, Ltd., the average particle size was 20 μm and the maximum particle size was 70 μm. rice field. For 100 parts by mass of acrylic rubber (ACM), 5 parts by mass of the paste-like mixture, 50 parts by mass of carbon black, 12.5 parts by mass of plasticizer, 1 part by mass of processing aids a and b, and aging. An unvulcanized rubber dough was prepared by kneading the inhibitor with 2 parts by mass, the vulcanization accelerator b with 0.5 parts by mass, and the vulcanizing agent with 0.5 parts by mass using an open roll at 70 ° C. The obtained unvulcanized rubber dough was vulcanized at 170 ° C. for 10 minutes using an injection molding machine and molded to obtain a gasket as a molded product. In the same manner as in Example 1, the obtained gasket was observed with a magnifying glass, and the defect rate (%) due to poor dispersion was calculated. The results are summarized in Table 3.

Comparative Example 3
In Example 3, instead of obtaining the paste-like mixture, 2.5 mass by mass of the powder of the vulcanization accelerator a (average particle size: 40 μm, maximum particle size: 300 μm) with respect to 100 parts by mass of acrylic rubber (ACM). 50 parts by mass of carbon black, 15 parts by mass of plasticizer, 1 part by mass of processing aids a and b, 2 parts by mass of anti-aging agent, 0.5 part by mass of vulcanization accelerator b, and addition. A gasket, which is a molded product, was obtained in the same manner as in Example 3 except that the vulcanizing agent was kneaded together with 0.5 parts by mass at 70 ° C. using an open roll. In the same manner as in Example 1, the obtained gasket was observed with a magnifying glass, and the defect rate (%) due to poor dispersion was calculated. The results are summarized in Table 3.

Claims (9)

A method for producing a rubber composition.
A wet pulverization step of adding a plasticizer to at least one powder material selected from the group consisting of a vulcanizing agent and a vulcanization accelerator and performing a wet pulverization treatment to obtain a paste-like mixture.
A method for producing a rubber composition, which comprises a kneading step of kneading at least rubber and the paste-like mixture to obtain a rubber composition. The method for producing a rubber composition according to claim 1, wherein the blending ratio of the powder material and the plasticizer in the paste-like mixture is 1: 0.5 to 1:20. The method for producing a rubber composition according to claim 1 or 2, wherein 0.1 to 100 parts by mass of the paste-like mixture is mixed with 100 parts by mass of the rubber. The rubber is from chloroprene rubber (CR), nitrile rubber (NBR), hydride nitrile rubber (HNBR), ethylene propylene rubber (EPDM), acrylic rubber (ACM), ethylene acrylic rubber (AEM) and fluororubber (FKM). At least one selected from the group of
The vulcanizing agent is at least one selected from the group consisting of sulfur and amine-based vulcanizing agents.
Claim 1 in which the vulcanization accelerator is at least one selected from the group consisting of a sulfur-based vulcanization accelerator, a guanidine-based vulcanization accelerator, a dithiocarbamate-based vulcanization accelerator, and a thiazole-based vulcanization accelerator. The method for producing a rubber composition according to any one of 3 to 3. The method for producing a rubber composition according to any one of claims 1 to 4, wherein the maximum particle size of the particles contained in the paste-like mixture is 80 μm or less. The method for producing a rubber composition according to any one of claims 1 to 5, wherein the average particle size of the particles contained in the paste-like mixture is 0.1 to 30 μm. The method for producing a rubber composition according to any one of claims 1 to 6, wherein in the kneading step, a second plasticizer is further added and kneaded. The method for producing a rubber molded product according to any one of claims 1 to 7, further comprising a vulcanization step of vulcanizing the rubber composition obtained in the kneading step. The method for manufacturing a rubber molded product according to claim 8, wherein the rubber molded product is a sealing member.