JPH07145291A - Acrylic rubber composition - Google Patents

Abstract

PURPOSE:To provide an acrylic rubber composition capable of giving molded products excellent in cold resistance and balanced in characteristics such as heat resistance and resistance to deterioration due to oil. CONSTITUTION:The objective composition comprising (A) 100 pts.wt. of an acrylic rubber polymer made up of (1) 80-90wt.% of butyl acrylate unit, (2) 3-15wt.% of at least one kind of monomer unit selected from alkoxyalkyl acrylates and acrylonitrile, (3) 0.1-5wt.% of halogen-contg. ethylenic unsaturated monomer unit and (4) 0-10wt.% of another ethylenic unsaturated monomer unit, (B) 10-200 pts.wt. of a reinforcing filler and (C) 0.1-10 pts.wt. of a curing agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic rubber composition for molding a molded article having excellent cold resistance and well-balanced properties such as heat resistance and deterioration oil resistance.

[0002]

Acrylic rubber is used as a material having a lubricating oil resistance in oil seals, O-rings, gaskets and oil hoses used in automobiles and hydraulic equipment. When the acrylic rubber composition used for these is composed of a multi-component composition containing ethyl acrylate, butyl acrylate, and methoxyethyl acrylate as main components in order to balance heat resistance, lubricating oil resistance, and cold resistance, in particular. There are many. However, the recent demand for improved resistance in deteriorated oil due to high temperatures around the engine has not been satisfied, particularly from the viewpoint of preventing cracking. Also,
Cold resistance is one of the drawbacks of acrylic rubber,
It is said that when the content of butyl acrylate is increased to improve the cold resistance, the heat resistance and the lubricating oil resistance (particularly the volume change rate in oil) are lowered. Therefore, it has been desired to provide excellent resistance to deterioration oil and improve cold resistance while balancing with other characteristics.

[0003]

From such a situation,
The present invention has been made to provide an acrylic rubber composition for molding which gives a molded article having excellent cold resistance and well-balanced properties such as heat resistance and deterioration oil resistance.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that one or more monomers selected from butyl acrylate units, alkoxyalkyl acrylates and acrylonitrile. Units, halogen-containing ethylenically unsaturated monomer units and other ethylenically unsaturated monomer units in the composition range, especially when using a rubber polymer having a high content of butyl acrylate units, heat resistance It was found that there is a possibility that not only cold resistance but also cold resistance as well as deterioration oil resistance may be significantly improved, and further studies were conducted to complete the present invention.

That is, the present invention includes (1) a) butyl acrylate unit 80 to 90% by weight, b) one or more monomer units selected from alkoxyalkyl acrylate and acrylonitrile, 3 to 15% by weight. ) Halogen-containing ethylenically unsaturated monomer unit 0.1 to 5% by weight d) Other ethylenically unsaturated monomer unit 0 to 10% by weight (however, the total of a) to d) is 100% by weight) An acrylic rubber composition comprising: 100 parts by weight of an acrylic rubber polymer (2) 10 to 200 parts by weight of a reinforcing filler (3) 0.1 to 10 parts by weight of a vulcanizing agent. To do.

The present invention will be described in detail below. The acrylic rubber polymer of the component (1) used in the present invention is
It can be obtained by copolymerizing a monomer corresponding to the units a) to d) by a known polymerization method such as emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization, etc., but emulsion polymerization is a particularly preferable method. .

The butyl acrylate unit of component (a) imparts the functions of cold resistance, heat resistance, and deterioration oil resistance. If the amount of this component in the rubber polymer is less than 80% by weight, deterioration oil resistance and cold resistance, which are the objects of the present invention, are impaired, and 90% by weight.
If it exceeds, the rate of volume increase in oil will increase, so 80
To 90% by weight.

The component (b), one or more monomer units selected from alkoxyalkyl acrylate and acrylonitrile, is a component that imparts the functions of preventing softening deterioration and lowering swelling of oil. Examples of alkoxyalkyl include methoxyethyl acrylate, ethoxyethyl acrylate, butoxyethyl acrylate, ethoxypropyl acrylate, and the like. If the amount of this component in the rubber polymer is less than 3% by weight, the volume increase rate in the oil will be large, and if it exceeds 15% by weight, the deterioration oil resistance and heat resistance which are the objects of the present invention will be insufficient. 3 to 15
It is set in the range of% by weight.

The halogen-containing ethylenically unsaturated monomer unit of the component (c) is a component which gives a crosslinking group in vulcanization,
Examples of the monomer corresponding to this unit include vinyl chloroacetate, 2-chloroethyl vinyl ether, allyl chloroacetate and the like, and among these, one kind or two or more kinds may be used as necessary. If the amount of this component in the rubber polymer is less than 0.1% by weight, the vulcanization will be insufficient, and if it exceeds 5% by weight, the crosslink density of the obtained vulcanizate will be too high, making it hard and brittle. Since the above physical properties cannot be obtained, the range is 0.1 to 5% by weight.

The other ethylenically unsaturated monomer units of the component (d) are used as required, and include methyl acrylate, ethyl acrylate, styrene, methyl methacrylate, methacrylonitrile, vinyl acetate. , Vinyl chloride, ethylene, propylene and the like are exemplified. When this component exceeds 10% by weight, the original properties of the acrylic rubber are impaired, which is not preferable.

Next, as the reinforcing filler of the component (2), carbon black, fumed silica by a dry method, precipitated silica synthesized from an alkyl silicate or sodium silicate by a wet method, magnesium silicate, and silica. Examples thereof include calcium acid, an organic silicon compound such as alkoxysilane and hexamethyldisilazane, or hydrophobic silica treated with a higher fatty acid.

The amount of the reinforcing filler compounded is 10 to 20 relative to 100 parts by weight of the acrylic rubber polymer of the component (1).
The amount is 0 parts by weight, preferably 20 to 100 parts by weight. If the blending amount is less than 10 parts by weight, the reinforcing effect is insufficient and practical mechanical strength cannot be obtained, and if it exceeds 200 parts by weight, the blending becomes difficult and good moldability cannot be obtained.

Examples of the vulcanizing agent (3) include polyamine carbamates, organic ammonium carboxylates, organic carboxylic acid alkali metal salts in combination with sulfur compounds, and triazine compounds.

When a triazine compound is used, the following crosslinking aids or crosslinking accelerators can be used as desired. As the cross-linking aid or cross-linking 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 metal Oxide,
Hydroxides, sulfides, carbonates, phosphates, thioates; dithioates; dithiocarbamic acid metal salts (metals are zinc, copper,
Cadmium, lead, bismuth, iron, cobalt, manganese,
Tellurium or selenium) may be used.

The vulcanizing agent is used in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the acrylic rubber polymer as 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 vulcanized product becomes hard and brittle, and desired properties cannot be obtained.

The composition comprising the above-mentioned components (1) to (3) is mixed with a predetermined amount of each component in a mixer such as a Banbury mixer, a kneader, an intermixer or a two-roll mill used for general rubber kneading. It can be easily obtained by kneading.

To the rubber composition of the present invention, if necessary, a filler, a plasticizer, an antiaging agent, a flame retardant, a processing aid and the like usually used in the rubber industry 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, and vulcanization is performed at this temperature for about 5 to 15 minutes. In addition, if necessary, at a temperature of about 150 to 180 ° C, 1
Post-vulcanization can be carried out for about 24 hours to improve the physical properties.

[0019]

EXAMPLES The present invention will be described in more detail with reference to synthesis examples of acrylic rubber polymers and examples using the same. In addition, part and% in an example show a weight part and weight%, respectively.

Synthesis Example 1 (Synthesis of Acrylic Rubber Polymer P-1) A closed reactor equipped with a stirrer, which had been purged with nitrogen, was charged with 200 parts of water and 2 parts of sodium lauryl sulfate to prepare 30 reactors.
After adjusting to ° C, 0.1 part of ammonium persulfate, 0.1 part of acidic sodium sulfite and 0.001 part of ferrous sulfate are added, and then 82 parts of butyl acrylate, 5 parts of methoxyethyl acrylate, 8 parts of acrylonitrile. Then, a monomer mixture of 2 parts of vinyl chloroacetate and 3 parts of ethyl acrylate was added dropwise over 3 hours. While maintaining the inside of the reactor at 30 ° C., stirring was continued for another hour to complete the reaction. The milky white emulsion obtained by the emulsion polymerization is salted out with an aqueous calcium chloride solution, washed with water and dried to 98.2.
Acrylic rubber polymer P-1 was obtained with a yield of%. The composition of this rubber polymer was analyzed, and the results are shown in Table 1.

Synthesis Examples 2 to 5 (acrylic rubber polymer P-
Synthesis of 2 to P-5) In the same manner as in Synthesis Example 1, acrylic rubber polymers P-2 to P-5 having the compositions shown in Table 1 were obtained.

[0022]

[Table 1]

Examples 1 and 2, Comparative Examples 1 to 3 Acrylic rubber polymers P-1 to 1 obtained in Synthesis Examples 1 to 5
A composition was prepared using P-5 in the blending amounts shown in Table 2. The obtained composition was vulcanized under the vulcanization conditions shown in Table 2, and J
Various physical properties of the vulcanized product were measured according to IS K6301, and the results are shown in Tables 3 and 4.

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

[Table 4]

As is clear from the comparison between the examples and the comparative examples, the vulcanized product of the composition of the present invention has the above-mentioned excellent properties and is well balanced in all properties including cold resistance. On the other hand, the vulcanized product of the composition of Comparative Example 1 was inferior in cold resistance and crack generation in the deterioration oil resistance test, and that of Comparative Example 2 was inferior in hardness change and volume change rate among oil resistance and deteriorated oil resistance. There is a problem in crack generation in the test, and the vulcanized product of Comparative Example 3 is inferior in heat resistance, deterioration oil resistance and compression set. In particular, crack generation may lead to crack growth, which may significantly reduce the sealability.

[0028]

EFFECTS OF THE INVENTION The acrylic rubber composition of the present invention is molded since the molded product obtained therefrom has excellent cold resistance, heat resistance, and deterioration oil resistance as compared with general acrylic rubber molded products. It is extremely useful as a material.

Claims (1)

[Claims] (1) a) butyl acrylate unit 80 to 90% by weight b) one or more monomer units selected from alkoxyalkyl acrylate and acrylonitrile 3 to 15% by weight c) halogen-containing 0.1 to 5% by weight of ethylenically unsaturated monomer unit d) Other ethylenically unsaturated monomer units 0 to 10% by weight (however, the total of a) to d) is 100% by weight) 100 parts by weight of a rubber-based polymer (2) 10 to 200 parts by weight of a reinforcing filler (3) 0.1 to 10 parts by weight of a vulcanizing agent, an acrylic rubber composition.