JPH07228746A - Acrylic rubber composition - Google Patents

Abstract

PURPOSE:To obtain a halogenated acrylic rubber compsn. which gives a molding depressed a metal rusting. CONSTITUTION:An acrylic rubber compsn., giving a molding with a vol. resistivity of 10<6>OMEGA.cm or higher, comprises 100 pts.wt. halogenated acrylic rubber, 20200 pts.wt. reinforcement mainly comprising silica with a specific surface area of 30m<2>/g or higher, 1-20 pts.wt. natural or synthetic hydrotalcite compd., and 0. 1-10 pts.wt. vulcanizing agent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a halogen-containing acrylic rubber composition. Since the molded article obtained from the composition of the present invention is significantly suppressed in the undesirable effect of generating metal rust, the composition of the present invention is used as a molding material such as hoses, seals and the like that are in contact with or in contact with a metal. It is useful.

[0002]

Acrylic rubber is mainly used for automobile parts as a synthetic rubber having excellent heat resistance, weather resistance and oil resistance. Due to the recent demand for improved productivity, halogen-containing acrylic rubber with a faster vulcanization rate than epoxy-containing acrylic rubber has come to be used more often, but the halogen group as a vulcanization site is extracted during vulcanization, It remains in the system as a halogen compound, and this is eluted as halogen ions by water, so that it rusts the metal at the time of contact with the metal, leading to corrosion. Therefore, the halogen-containing acrylic rubber is restricted in its application, and for the hoses, seals, etc. that come in contact with metal, the epoxy group-containing acrylic rubber that has a slow vulcanization rate but hardly causes metal rust is used. It is used a lot.

[0003]

From such a situation,
The present invention has been made to provide an acrylic rubber composition which is useful as a molding material for the purpose of suppressing metal rusting due to a halogen-containing acrylic rubber and for contacting with metals such as hoses and seals.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have compounded a halogen-containing acrylic rubber with a silica-based reinforcing filler and hydrotalcites, and molding the mixture. The volume resistivity of the product is 10 ⁶ Ω
It was found that the above-mentioned problems could be solved by setting the height to be cm or more, and further studies were conducted to complete the present invention.

That is, the present invention is: (1) 100 parts by weight of a halogen-containing acrylic rubber (2) 20 to 200 parts by weight of a reinforcing filler mainly composed of silica having a specific surface area of at least 30 m ² / g (3) Natural Or 1 to 20 parts by weight of a synthetic hydrotalcite compound (4) an acrylic rubber composition comprising 0.1 to 10 parts by weight of a vulcanizing agent, and the molded product having a volume resistivity value of 10 ⁶ Ω · cm or more. It is what The present invention will be described in detail below.

The halogen-containing acrylic rubber of the component (1) used in the present invention may be a commercially available product, and usually (a) the general formula CH ₂ = C (R ¹ ) COOR ² (where R ¹ is a hydrogen atom). Or a methyl group, and R ² represents an alkyl group or an alkoxy-substituted alkyl group having 1 to 18 carbon atoms), a monomer selected from acrylic acid ester and methacrylic acid ester (b) a halogen-containing ethylenically unsaturated monomer Monomer selected from monomers (C) A copolymer obtained by radical copolymerizing a monomer selected from other ethylenically unsaturated monomers.

As the acrylic acid ester or methacrylic acid ester of the above (a), methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth)
Acrylate, 2-ethylhexyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate and the like are exemplified.

Examples of the halogen-containing ethylenically unsaturated monomer (b) include vinyl chloroacetate and vinyl-2-
Chloropropionate, vinyl-3-chloropropionate, allyl chloroacetate, 2-chloroethyl (meth) acrylate, 2-chloroethyl vinyl ether,
Examples thereof include vinylbenzyl chloride, 5-chloromethyl-2-norbornene, and compounds containing a bromine atom in place of these chlorine atoms, but vinylchloroacetate is preferred. This halogen-containing ethylenically unsaturated monomer provides a crosslinking group in vulcanization, and the amount ratio thereof is preferably 0.1 to 10% by weight as a monomer unit in the halogen-containing acrylic rubber of the component (1). If it is less than 0.1% by weight, the vulcanization becomes insufficient, and if it exceeds 10% by weight, the crosslink density of the obtained vulcanized product becomes too high and it becomes hard and brittle, and desired physical properties cannot be obtained.

The other ethylenically unsaturated monomer (c) is used as necessary, and includes styrene, vinyltoluene, α-methylstyrene, vinylnaphthalene,
Acrylonitrile, methacrylonitrile, acrylamide, vinyl acetate, vinyl chloride, ethylene, propylene and the like are exemplified. The amount ratio of (c) is preferably 30% by weight or less because the original characteristics of the acrylic rubber are impaired if the monomer unit exceeds 30% by weight in the halogen-containing acrylic rubber of the component (1).

The component (2) is a component for reinforcing the molded product and realizing the volume resistivity value, and is a reinforcing filler mainly composed of silica and having a specific surface area of at least 30 m ² / g. It is essential to use a silica-based reinforcing filler in order to maintain the volume resistivity value of the molded product obtained from the composition comprising the components (1) to (4) at 10 ⁶ Ω · cm or more. It was also found, however, that this compound satisfies the above-mentioned volume resistivity value in the range of the amount usually blended as a reinforcing filler. Examples of the silica-based reinforcing filler include fumed silica by a dry method, precipitated silica synthesized by a wet method from alkyl silicate or sodium silicate, magnesium silicate, calcium silicate, or alkoxysilane or hexamethyl. Examples include organic silicon compounds such as disilazane and hydrophobic silica treated with higher fatty acids. This silica-based reinforcing filler may be used in combination with a non-silica-based reinforcing filler such as carbon black as long as the volume resistivity value of 10 ⁶ Ω · cm or more can be maintained.

The compounding amount of the component (2) is 20 to 200 parts by weight, preferably 40 to 100 parts by weight, based on 100 parts by weight of the halogen-containing acrylic rubber of the component (1). If it is less than 20 parts by weight, the reinforcing effect is insufficient, and if it exceeds 200 parts by weight, its blending becomes difficult and a good molded product cannot be obtained. From the volume resistivity value, when the compounding amount is small, the total amount is silica type, but when it is about 40 parts by weight or more, a non-silica type may be used together as a part thereof.

As the natural or synthetic hydrotalcite compound as the component (3), Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O or
An example is a water-containing basic carbonate of magnesium / aluminum having a composition such as Mg _4.5 Al ₂ (OH) ₁₃ CO ₃ · 3.5H ₂ O. This material has a property of adsorbing an acid, for example, in the case of hydrochloric acid, CO ₃ in the chemical structure of the hydrotalcite ^- is Cl
^It is easily replaced by-and the chloride ion is incorporated into the crystal structure. The chlorine ion-type hydrotalcite compound newly generated in this manner is far less water-soluble and oil-soluble than other acid-accepting agents, and is used as a useful acid-accepting agent.

However, the inventors of the present invention tried to blend the hydrotalcites with a halogen-containing acrylic rubber, and as a result, although the reason is not clear, the volume resistivity of a molded product obtained from this rubber composition is unknown. When the value is small, rust is observed in the metal that contacts the molded product, whereas when the volume resistivity of the molded product is 10 ⁶ Ωcm or more, the occurrence of rust in the metal can be significantly suppressed. I found it. The blending amount of component (3) is the halogen-containing acrylic rubber of component (1) 1
1 to 20 parts by weight, preferably 2 to 100 parts by weight
10 parts by weight. If it is less than 1 part by weight, the effect of capturing chlorine ions and the like is insufficient, and if it exceeds 20 parts by weight, heat resistance, mechanical strength, etc. are deteriorated and the performance as an acrylic rubber is impaired.

Examples of the vulcanizing agent as the component (4) include polyamine carbamates, ammonium organic carboxylic acids, combinations of organic carboxylic acid alkali metal salts with sulfur or a sulfur compound, and triazine compounds. When using a triazine compound, the following vulcanization aids or vulcanization accelerators can be used as desired. As the vulcanization aid or vulcanization accelerator, an alkali metal salt, an alkaline earth metal salt or an ammonium salt of an aromatic or aliphatic mono- or polybasic acid; an alkali metal salt of cyanuric acid; an alkali metal or an alkaline earth Examples thereof include oxides, hydroxides, carbonates, phosphates and thioates of group metals, and metal salts of dithiocarbamic acid.

The amount of the vulcanizing agent used is 0.1 to 10 parts by weight based on 100 parts by weight of the halogen-containing acrylic rubber of the component (1). If it is less than 0.1 part by weight, the rubber composition of the present invention cannot be vulcanized well, and if it exceeds 10 parts by weight, the obtained molded product becomes hard and brittle, and desired properties cannot be obtained. Further, in order to maintain the volume resistivity of the vulcanized product at 10 ⁶ Ω · cm or more, it is preferable to reduce the amount of the vulcanizing agent containing the metal salt or the vulcanization aid as much as possible.

In order to obtain a composition from the above-mentioned components (1) to (4), a predetermined amount of each component is a mixer such as a Banbury mixer, a kneader, an intermixer, or a two-roll machine used for general rubber kneading. The composition can be easily obtained by the method of kneading. Since the silica-based filler contains some water, it is necessary to add it during the kneading before adding the vulcanizing agent.
It is desirable to remove moisture by applying a temperature of 100 ° C or higher. In addition to the components described above, the rubber composition of the present invention contains a filler that is usually used in the rubber industry, if necessary, within a range in which the volume resistivity of the molded product can be maintained at 10 ⁶ Ω · cm or more. , A plasticizer, an antiaging agent, a flame retardant, a processing aid and the like can be appropriately added.

The rubber composition thus obtained is molded into a shape suitable for the purpose and vulcanized to obtain a molded product. A vulcanization temperature of 160 to 190 ° C is usually suitable.
Vulcanization is performed at this temperature for about 5 to 15 minutes. If necessary, post-vulcanization may be carried out at a temperature of about 150 to 180 ° C. for about 1 to 24 hours to improve the physical properties.

[0018]

EXAMPLES The present invention will be described in more detail with reference to the following examples. In addition, the part in an example shows a weight part. The measuring methods of the volume specific resistance value and the rust generation test are as follows. 1) Volume resistivity value According to HEWLETT-PACKARD manufactured by Yokogawa Electric Corporation,
The volume specific resistance value of the vulcanized sheet with a thickness of 1 mm described below is applied
Measured at 500V. 2) Rust generation test A vulcanized sheet with a thickness of 1 mm is sandwiched between steel plates SS-400, left at 60 ° C x 90% RH x 14 days in a 10% compressed state, and then the steel plate is removed. Was visually observed and judged according to the following criteria. 〇 No rust occurred. △ There is no rust at the center of the steel sheet, but rust occurs at the edges. × Rust occurred at the center and edges of the steel sheet.

Example 1 Halogen-containing acrylic rubber RV-1260 (trade name, manufactured by Nissin Chemical Industry Co., Ltd.) 100 parts, stearic acid 1 part, Naugard # 445 (antiaging agent; trade name, manufactured by Uniroyal Co., Ltd.) 2
Part, Nipsil LP (precipitating silica; trade name of Nippon Silica Industry Co., Ltd.) 67 parts, RS-735 (plasticizer; product name of Asahi Denka Co., Ltd.) 8 parts, Hydrotalcite DHT-4A (product of Kyowa Chemical Industry Co., Ltd.) After thoroughly kneading 5 parts (name) with a pressure kneader, the mixture was heated and mixed at 130 ° C. for 10 minutes to remove water. Then, with a two-roll mill, 1.9 parts of 2,4,6-trithiol-S-triazine and 4.1 parts of zinc dibutyldithiocarbamate were added and sufficiently kneaded to prepare a composition. This composition
Press vulcanization was performed at 180 ° C. for 10 minutes, and post-vulcanization was further performed at 180 ° C. for 4 hours to obtain vulcanized sheets having thicknesses of 1 mm and 2 mm. The physical properties of the vulcanized sheet with a thickness of 2 mm were measured according to JIS K-6301, the volume resistivity of the vulcanized sheet with a thickness of 1 mm was measured, and the degree of rust on the steel sheet was observed. Shown in 1. The composition is shown in Table 1 again.

Examples 2 to 3 According to Example 1, compositions were prepared with the compounding amounts shown in Table 1. The composition obtained was press-vulcanized at 180 ° C. for 10 minutes and then post-vulcanized at 180 ° C. for 4 hours to give a thickness of 1 mm and 2 mm.
A vulcanized sheet of mm was obtained. The general physical properties and volume resistivity of this sheet were measured in the same manner as in Example 1, and the rust generation state was observed. The results are shown in Table 1.

Comparative Examples 1 to 3 According to Example 1, compositions were prepared in the amounts shown in Table 1. However, in Comparative Example 1, removal of water by heating and mixing at 130 ° C. for 10 minutes was omitted. The resulting composition was heated at 180 ° C for 10
Press vulcanize for 1 minute, then post vulcanize at 180 ℃ for 4 hours,
Vulcanized sheets having a thickness of 1 mm and 2 mm were obtained. The general physical properties and volume resistivity of this sheet were measured in the same manner as in Example 1, and the rust generation state was observed. The results are shown in Table 1.

[0022]

[Table 1] Note 1) Halogen-containing acrylic rubber (trade name of Nissin Chemical Industry Co., Ltd.) Note 2) Acrylic rubber containing halogen (trade name of Nissin Chemical Industry Co., Ltd.) Note 3) Precipitable silica (trade name of Shionogi Pharmaceutical Co., Ltd.)

As is clear from the comparison between the examples and the comparative examples, the molded articles obtained from the composition of the present invention do not generate rust even when they are brought into pressure contact with a metal under high temperature and high humidity. In the comparative examples, not only the hydrotalcite-type compound was not used, but also the hydrotalcite-type compound blended product generated a large amount of rust when the volume resistivity value was small.

[0024]

INDUSTRIAL APPLICABILITY The acrylic rubber composition of the present invention has a remarkably high effect of suppressing the generation of metal rust by a molded product obtained from the acrylic rubber composition, which is difficult to use in conventional halogen-containing acrylic rubber molded products. It is extremely useful as a molding material for contact applications.

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Claims (1)

[Claims] (1) 100 parts by weight of a halogen-containing acrylic rubber (2) 20 to 200 parts by weight of a reinforcing filler mainly composed of silica having a specific surface area of at least 30 m ² / g (3) natural or synthetic hydro 1 to 20 parts by weight of talcite compound (4) An acrylic rubber composition comprising 0.1 to 10 parts by weight of a vulcanizing agent, and the molded product having a volume resistivity value of 10 ⁶ Ω · cm or more.