JPH04209645A - Acrylic rubber composition and its production - Google Patents

Abstract

PURPOSE:To efficiently prepare the title compsn. excellent in the resistance to oil, heat, and coldness by mixing an acrylic rubber with a specified amt. of a silicone rubber powder and a stabilizer. CONSTITUTION:100 pts.wt. acrylic rubber is compounded with 5-30 pts.wt. silicone rubber powder and a stabilizer which stabilizes the dispersion of the powder in the acrylic rubber (e.g. a silicon oil). The resulting mixture is molded and vulcanized to give the title compsn. wherein the silicon rubber is dispersed in the acrylic rubber. The compsn., excellent esp. in oil resistance at high temp., is suitably used as the material of a seal, a packing, a gasket, etc., to be used in the areas where the resistance to oil and heat is required.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an acrylic rubber composition used for forming sealing materials such as seals, packings, and gaskets, and a method for producing the same.

<Prior art and problems to be solved by the invention> Conventionally, acrylic rubber compositions have excellent heat resistance, oil resistance, etc.
It is known for its excellent oil resistance, especially at high temperatures.

Furthermore, by taking advantage of the above characteristics of acrylic rubber compositions, acrylic rubber compositions are used to form sealing materials such as seals, gaskets, and gaskets used in parts that require oil resistance and heat resistance.

On the other hand, acrylic rubber compositions have poor cold resistance and tend to become brittle and lose elasticity at low temperatures, so they have the disadvantage that they may not be usable in low-temperature environments.

In particular, acrylic rubber compositions with excellent oil resistance have a high brittle point and cannot be used in an environment of -40 to -20'C or lower.

For this reason, JP-A No. 60-152552 discloses that an acrylic rubber having a double bond in a crosslinking group is used as a raw material for an acrylic rubber base material, and a predetermined amount of polyorganosiloxane or siloxane-acrylic ester is added to the acrylic rubber. An acrylic rubber composition manufactured by mixing copolymers and heating and melting the mixture is disclosed.

However, when producing the above acrylic rubber composition, it is difficult to uniformly disperse polyorganosiloxane or siloxane-acrylic acid ester copolymer in the raw material of the acrylic rubber base material, and it is difficult to disperse the island structure in the compounded rubber. Therefore, there was a problem that physical properties, especially at low temperatures, were less effective.

The present invention has been made in view of the above problems, and provides an acrylic rubber composition for forming a sealing material that has excellent oil resistance, heat resistance, and cold resistance, and an efficient production of the acrylic rubber composition. The purpose of the present invention is to provide a method for producing an acrylic rubber composition.

Means for Solving Problems〉 The inventor of the present application has discovered the new fact that the cold resistance of acrylic rubber compositions can be improved by uniformly dispersing a predetermined amount of silicone rubber in an acrylic rubber base material, and powder powder. The present invention has been based on the discovery of a new fact that silicone rubber easily disperses in the raw material of acrylic rubber base material, and a new fact that silicone oil improves the compatibility between acrylic rubber base material and silicone rubber. I was able to complete it.

That is, the acrylic rubber composition according to the present invention is characterized in that silicone rubber is dispersed in the acrylic rubber base material at a ratio of 5 to 30 parts by weight per 100 parts by weight of the acrylic rubber base material. do.

Furthermore, the method for producing the acrylic rubber composition according to the present invention includes:
A method for producing an acrylic rubber composition by mixing raw materials for an acrylic rubber base material and vulcanizing the mixture, the method comprising: mixing powdered silicone rubber as a raw material for the acrylic rubber base material; It is characterized in that it is mixed at a ratio of 5 to 30 parts by weight per 100 parts by weight, and at the same time, a stabilizer for stably retaining the silicone rubber in the acrylic rubber base material is mixed and vulcanization molded.

<Function> In the above acrylic rubber composition, silicone rubber with excellent cold resistance is contained in the acrylic rubber base material 100% of the acrylic rubber base material.
Since it is dispersed at a ratio of 5 to 30 parts by weight, the cold resistance of the acrylic rubber base material can be improved. Furthermore, since silicone rubber has excellent heat resistance and oil resistance, the heat resistance and oil resistance of the acrylic rubber base material can be maintained.

The above silicone rubber is dispersed at a ratio of 5 to 30 parts by weight per 100 parts by weight of the acrylic rubber base material, but the reason why the ratio of silicone rubber is limited to the above range is that the ratio of silicone rubber is smaller than the above range. If so, the cold resistance of the acrylic rubber base material will not be improved, and if it exceeds the above range, it will be difficult to disperse in the acrylic rubber base material and the strength of the resulting acrylic rubber composition will decrease.

Furthermore, as the silicone rubber, one having an epoxy group is preferable from the viewpoint of compatibility with the acrylic rubber base material, and furthermore, a powdery one with a particle size of about 20 yen or a silicone rubber having an epoxy group is preferable because it can be dispersed in the acrylic rubber base material. It is preferable.

The acrylic rubber base material used is not particularly limited, and any material that has been conventionally used to form sealing materials can be used, but epoxy crosslinked acrylic rubber base materials are particularly suitable. Preferably.

On the other hand, when producing an acrylic rubber composition by the method of the present invention, the silicone rubber mixed into the raw material for the acrylic rubber base material is in powder form, so it can be uniformly mixed into the raw material for the acrylic rubber base material in a short time. It can be dispersed.

Furthermore, since the compatibility of silicone rubber with the acrylic rubber base material is increased by the stabilizer, it is stably retained in the acrylic base material.

Examples of the stabilizer include silicone oil.

The silicone oil mentioned above is not particularly limited, and various silicone oils can be used, but
It is preferable to have a substituent such as a carboxyl group or an alcohol group at the terminal in order to enhance the compatibility effect.

The silicone oil may be added in an amount of 1 to 7 parts by weight per 100 parts by weight of raw materials for the acrylic rubber base material.
It is preferable to disperse in parts by weight. This is because if the proportion of silicone oil is smaller than the above range, the compatibility between silicone rubber and acrylic rubber base material can be sufficiently increased, and if it exceeds the above range, blades will occur and the oil will seep out. It is.

Note that instead of silicone oil, soaps such as alkaline soap or metal soap that exhibit the same effect may be used.

In addition, when producing an acrylic rubber composition using this method, conventionally used additives such as stearic acid, anti-aging agents, reinforcing materials, and vulcanizing agents are appropriately added to the raw material of the acrylic rubber base material. You may.

Stearic acid is added as an aid during vulcanization and processing. The carboxyl group of stearic acid acts as an activator during vulcanization and improves flowability during processing. In addition, stearic acid is used for acrylic rubber base material 100
It is preferable to add it in a ratio of 1 to 3 parts by weight based on the weight part.

Further, as the above-mentioned anti-aging agent, Tsukrak CD is used.

Examples include diphenylamine compounds such as Naracard #445 (all trade names). As the reinforcing agent, carbon such as FEF carbon can be used. Examples of the vulcanizing agent include dithiocarbamates such as so-called PZ and TTFE.

<Example> Hereinafter, the present invention will be explained in more detail based on Examples.

Example 1 100 parts by weight of a cold-resistant grade acrylic rubber base material raw material (ACM) consisting of a ternary copolymer of ethyl acrylate, butyl acrylate, and methoxy acrylate, 15 parts by weight of silicone rubber powder with a particle size of 20 μm, and 3 parts by weight of silicone oil. 1.5 parts by weight of anti-aging agent, 50 parts by weight of reinforcing agent and 2 parts by weight of vulcanizing agent were kneaded using a 6-inch test roll machine, and then kneaded by 1.5 parts by weight of antioxidant using a hydraulic hot press machine.
A 11l10x120x2 sheet was vulcanized at 70°C for 20 minutes. The sheet was then subjected to secondary vulcanization at 170° C. for 2 hours using a gear oven to obtain an acrylic rubber composition of the present invention.

Examples 2 to 3 and Comparative Example An acrylic rubber composition was obtained in the same manner as in Example 1 using the materials shown in Table 1 in the proportions shown in Table 1.

Evaluation Test The acrylic rubber compositions obtained in Examples 1 to 3 and Comparative Examples were subjected to an air heat aging test, a cold resistance test, an oil resistance test, a hardness test, a tensile strength test, and an elongation test.

The results are shown in Table 1.

The hardness is JIS A hardness, and the tensile strength test and elongation test were conducted according to JIS K6301. The air heat aging test was conducted at 150"C for 70 hours, and the oil resistance test was conducted using JIS #1 oil at 150"C for 70 hours.
S K63011. : The hardness change, tensile strength change rate, and elongation change rate were investigated. Also,
In the cold resistance test, the temperature at which the torsion returns by 10% (TR) was investigated.

(The following is a blank space) From Table 1, it can be seen that the acrylic rubber compositions of Examples 1 to 3 have a TRa that is 4 to 12°C lower than those of the comparative examples, indicating that they have excellent cold resistance. Kawakaru also has excellent heat resistance and oil resistance. Furthermore, Examples 1-
It can be seen that the acrylic rubber composition of No. 3 has tensile strength, elongation, and hardness that pose no practical problem as a sealant.

Moreover, from Examples 1 to 3, it can be seen that acrylic rubber compositions having the above characteristics were obtained in a short time.

<Effects of the Invention> As described above, in the acrylic rubber composition according to the present invention, silicone rubber is dispersed in the acrylic rubber base material at a ratio of 5 to 30 parts by weight per 100 parts by weight of the acrylic rubber base material. It has excellent cold resistance, heat resistance, and oil resistance, so by using the acrylic rubber composition according to the present invention, a sealing material with excellent cold resistance, heat resistance, and oil resistance can be formed. .

Further, according to the method for producing an acrylic rubber composition according to the present invention, the silicone rubber mixed with the raw material of the acrylic rubber base material is in powder form, and is mixed together with a stabilizer, so that the acrylic rubber base material In addition to being able to efficiently disperse silicone rubber in the raw materials, it is also possible to obtain an acrylic rubber composition in which silicone rubber is stably retained in the acrylic rubber base material. Therefore, an acrylic rubber composition with excellent cold resistance, heat resistance, and oil resistance can be efficiently produced.

Patent applicant Koyo Seiko Co., Ltd. Representative Patent attorney Takashi Watanabe (and 2 others)

Claims (1)

[Claims] 1. An acrylic rubber composition for forming a sealing material, wherein the acrylic rubber base material contains 5 to 30 parts by weight of silicone rubber based on 100 parts by weight of the acrylic rubber base material. An acrylic rubber composition characterized in that it is dispersed in a proportion. 2. A method for producing an acrylic rubber composition by mixing raw materials for an acrylic rubber base material and vulcanizing the mixture, the method comprising adding powdered silicone rubber to the acrylic rubber base material and vulcanizing the mixture. The silicone rubber is mixed at a ratio of 5 to 30 parts by weight with respect to 100 parts by weight of the raw material, and at the same time, a stabilizer for stably retaining the silicone rubber in the acrylic rubber base material is mixed and vulcanization molded. A method for producing an acrylic rubber composition.