JP3331249B2 - Acrylic rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. 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 has an undesired effect of generating metal rust, the composition of the present invention is used as a molding material for hoses, seals, etc. which are in contact with metal or joints. Useful.

[0002]

2. Description of the Related Art Acrylic rubber is mainly used for automobile parts as a synthetic rubber having excellent heat resistance, weather resistance and oil resistance. Due to recent demands for productivity improvement, halogen-containing acrylic rubbers having a higher vulcanization rate than epoxy group-containing acrylic rubbers have come to be used more frequently, but halogen groups as vulcanization sites are pulled out during vulcanization, It remains in the system as a halogen compound, which elutes as halogen ions due to moisture, causing the metal to rust upon contact with the metal, leading to corrosion. For this reason, halogen-containing acrylic rubber is limited in application.Hose and seals that come into contact with metal have a low vulcanization rate, but an epoxy-containing acrylic rubber that hardly generates metal rust is used. It is heavily used.

[0003]

SUMMARY OF THE INVENTION Under such circumstances,
The present invention has been made to provide an acrylic rubber composition which is useful as a molding material for use in contact with metals such as hoses and seals by suppressing the generation of metal rust due to halogen-containing acrylic rubber.

[0004]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, compounded a silica-based reinforcing filler and a hydrotalcite with a halogen-containing acrylic rubber, and formed the molded product. Volume resistivity of 10 ⁶ Ω
It has been found that the above problem may be solved by setting the diameter to cm or more, and further studies have been made to complete the present invention.

That is, the present invention relates to (1) (a) a general formula CH ₂ CC (R ¹ ) COOR ² (where R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1 to 18 carbon atoms) or an alkoxy substituted alkyl group) monomer 60 to 99.9 by weight% selected from acrylic and methacrylic acid esters represented by the monomer 0.1 selected from (b) halogen-containing ethylenically unsaturated monomer 10 wt%, and (iii) other ethylenically unsaturated monomer 30 wt% halogen-containing acrylic rubber 100 parts by weight obtained by radical copolymerization of a monomer selected from the following (2) specific surface area of at least 30m ² / g 20-200 parts by weight of silica-based reinforcing filler (3) Natural or synthetic hydrotalcite compounds 1-20 parts by weight (4) Vulcanizing agent 0.1-10 parts by weight , The volume resistivity of the molded product is 10 ⁶ Ωcm or more And an acrylic rubber composition. Hereinafter, the present invention will be described in detail.

The halogen-containing acrylic rubber of the component (1) used in the present invention is represented by the following general formula : (a) General formula CH ₂ = C (R ¹ ) COOR ² (where R ¹ is a hydrogen atom or a methyl group, and R ² is Represents an alkyl group or an alkoxy-substituted alkyl group of 1 to 18), and a monomer selected from acrylates and methacrylates (b) a monomer selected from halogen-containing ethylenically unsaturated monomers ( C) A copolymer obtained by radical copolymerization of a monomer selected from other ethylenically unsaturated monomers.

The acrylate or methacrylate of (a) includes methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth)
Acrylate, 2-ethylhexyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate and the like are exemplified.

The halogen-containing ethylenically unsaturated monomers (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 those containing a bromine atom instead of a chlorine atom, and preferably vinyl chloroacetate. The halogen-containing ethylenically unsaturated monomer gives a crosslinking group in vulcanization, and its amount ratio 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 crosslinked density of the obtained vulcanizate becomes too high to be hard and brittle, and desired physical properties cannot be obtained.

The other ethylenically unsaturated monomers of (c) are used as needed, and include styrene, vinyltoluene, α-methylstyrene, vinylnaphthalene,
Acrylonitrile, methacrylonitrile, acrylamide, vinyl acetate, vinyl chloride, ethylene, propylene and the like are exemplified. If the amount ratio of this (c) exceeds 30% by weight as a monomer unit in the halogen-containing acrylic rubber of the component (1), the inherent properties of the acrylic rubber will be impaired.

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

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

As the natural or synthetic hydrotalcite compound (3), Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O or
Mg _4.5 Al ₂ (OH) ₁₃ CO ₃ · 3.5H ₂ O and the like. 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 chlorine ions incorporated into the crystal structure. The chlorine ion type hydrotalcite compounds newly formed in this manner are far less water-soluble and hardly oil-soluble than other acid acceptors, and are used as useful acid acceptors.

However, the present inventors have attempted to blend the hydrotalcites into the halogen-containing acrylic rubber, but as a result, for unknown reasons, the volume resistivity of the molded article obtained from the rubber composition has been unknown. If the value is small, rust is observed on the metal in contact with the molded product, whereas if the volume resistivity of the molded product is 10 ⁶ Ωcm or more, the rust can be significantly suppressed. I found it. Component (3) is compounded in the amount of halogen-containing acrylic rubber (1).
1 to 20 parts by weight with respect to 00 parts by weight, preferably 2 to 20 parts by weight.
10 parts by weight. If the amount is less than 1 part by weight, the effect of trapping chlorine ions and the like is insufficient. If the amount exceeds 20 parts by weight, heat resistance, mechanical strength and the like are lowered, and the performance as an acrylic rubber is unfavorably deteriorated.

Examples of the vulcanizing agent of the component (4) include polyamine carbamates, organic carboxylic acid ammoniums, a combination of an organic carboxylic acid alkali metal salt and sulfur or a sulfur compound, and a triazine compound. When a triazine compound is used, the following vulcanization aid or vulcanization accelerator can be used as desired. Examples of the vulcanization aid or vulcanization accelerator include: alkali metal salts, alkaline earth metal salts or ammonium salts of aromatic or aliphatic mono- or polybasic acids; alkali metal salts of cyanuric acid; alkali metals or alkaline earths Metal oxides, hydroxides, carbonates, phosphates, thioates; metal dithiocarbamates, and the like.

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 as the component (1). If the amount is less than 0.1 part by weight, the rubber composition of the present invention cannot be vulcanized satisfactorily. If the amount exceeds 10 parts by weight, the obtained molded product becomes hard and brittle, and desired characteristics cannot be obtained. 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 or vulcanizing aid containing a metal salt as much as possible.

In order to obtain a composition from the above components (1) to (4), a predetermined amount of each component is mixed with a mixer such as a Banbury mixer, a kneader, an intermixer, or a two-roll mixer used for general rubber kneading. And the composition can be easily obtained. Silica-based fillers contain some water, so during kneading before adding a vulcanizing agent
It is desirable to remove water by applying a temperature of 100 ° C. or higher. In addition to the above-mentioned components, the rubber composition of the present invention may contain, if necessary, a filler generally used in the rubber industry as long as the volume resistivity of the molded product can be maintained at 10 ⁶ Ωcm or more. , A plasticizer, an antioxidant, a flame retardant, a processing aid, and the like can be appropriately added.

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

[0018]

The present invention will be described more specifically with reference to the following examples. In addition, the part in an example shows a weight part. The measurement methods of the volume resistivity and the rust generation test are as follows. 1) Volume specific resistance value According to HEWLETT-PACKARD manufactured by Yokogawa Electric Corporation,
Apply the volume resistivity of the 1mm thick vulcanized sheet described below to the applied voltage.
Measured at 500V. 2) Rust generation test Both sides of a vulcanized sheet having a thickness of 1 mm are sandwiched between steel plates SS-400. After leaving for 10 days in a 10% compressed state at 60 ° C x 90% RH x 14 days, the steel plate is removed, and the degree of rust generation on the steel plate surface Was visually observed and judged according to the following criteria.な し No rust. △ There is no rust at the center of the steel sheet, but rust occurs at the end. × Rust occurred at the center and end of the steel plate.

Example 1 Halogen-containing acrylic rubber RV-1260 (trade name, manufactured by Nissin Chemical Industry Co., Ltd.) 100 parts, stearic acid 1 part, Nowgard # 445 (antiaging agent; trade name, manufactured by Uniroyal Co.) 2
Parts, Nipsil LP (precipitable silica; trade name, manufactured by Nippon Silica Industry Co., Ltd.) 67 parts, RS-735 (plasticizer; trade name, manufactured by Asahi Denka Co., Ltd.) 8 parts, hydrotalcite DHT-4A (manufactured by Kyowa Chemical Industry Co., Ltd.) Name) 5 parts were sufficiently kneaded with a pressure kneader, and heated and mixed at 130 ° C. for 10 minutes to remove water. Next, 1.9 parts of 2,4,6-trithiol-S-triazine and 4.1 parts of zinc dibutyldithiocarbamate were added and kneaded sufficiently with a two-roll mill to prepare a composition. This composition
Press vulcanization was performed at 180 ° C. for 10 minutes, followed by post-vulcanization at 180 ° C. for 4 hours to obtain vulcanized sheets having a thickness of 1 mm and 2 mm. Measure the general physical properties according to JIS K-6301 using a vulcanized sheet with a thickness of 2 mm, measure the volume resistivity value of a vulcanized sheet with a thickness of 1 mm, and observe the degree of rusting of the steel sheet. 1 is shown. The composition is shown in Table 1 again.

Examples 2 to 3 In accordance with Example 1, compositions were prepared in the amounts shown in Table 1. The obtained composition was press-vulcanized at 180 ° C. for 10 minutes and further post-vulcanized at 180 ° C. for 4 hours to obtain a 1 mm thick
mm vulcanized sheet was obtained. For this sheet, the general physical properties and the volume resistivity were measured in the same manner as in Example 1, the rust generation was observed, and the results are shown in Table 1.

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

[0022]

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

As is clear from the comparison between the examples and the comparative examples, the molded article obtained from the composition of the present invention has no rust even when it is brought into contact with metal under high temperature and high humidity under pressure. In the comparative examples, not only those in which the hydrotalcite compound was not used, but also those in which the hydrotalcite compound was used had a large volume of rust when the volume resistivity was small.

[0024]

The acrylic rubber composition of the present invention has a remarkably high effect of suppressing the formation of metal rust by the molded product obtained therefrom, and it has been difficult to use it with a halogen-containing acrylic rubber-based molded product. It is extremely useful as a molding material for contact applications.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08L 33/14-33/16 WPI (DIALOG)

Claims (1)

(57) [Claims] (1) (a) General formula CH ₂ = C (R ¹ ) COOR ² (where R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl or alkoxy substituted with 1 to 18 carbon atoms) monomer 60 to 99.9 by weight% selected from acrylic and methacrylic acid esters represented by an alkyl group), a monomer 0.1 to 10 wt selected from (b) halogen-containing ethylenically unsaturated monomer % And (c) 100 parts by weight of a halogen-containing acrylic rubber obtained by radical copolymerization of a monomer selected from 30% by weight or less of other ethylenically unsaturated monomers. (2) The specific surface area is at least 30 m ² / 20 to 200 parts by weight of a silica-based reinforcing filler as the main component (g) 1 to 20 parts by weight of a natural or synthetic hydrotalcite compound (4) 0.1 to 10 parts by weight of a vulcanizing agent Rubber with a volume resistivity of 10 ⁶ Ωcm or more Composition.