JPH09110940A - Production of acrylic elastomer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an acrylic elastomer vulcanizable with an organic peroxide by copolymerizing at least one specific acrylate, a polymerizable unsaturated compound having specific functional groups, and other monomer(s) copolymerizable therewith. SOLUTION: An acrylic elastomer vulcanizable with an organic peroxide which is produced by copolymerizing 30-99.5 pts.wt. at least one acrylate (a) selected from among alkyl acrylates having a 1-8C alkyl, 0.5-30 pts.wt. compound (b) having one polymerizable unsaturated group and a methylene or methine group having an oxygen atom at the α-position, and 0-60 pts.wt. at least one other monomer (c) copolymerizable with the components (a) and (b). The ingredient (b) is preferably a compound having both an alkoxyalkylene group comprising 1-8 carbon atoms and one polymerizable unsaturated group. A compound having a dioxymethylene or cyclic ether group and one polymerizable unsaturated group is also preferred as the component (b).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing an acrylic elastomer. More specifically, it relates to a method for producing a novel acrylic elastomer capable of being vulcanized with an organic peroxide.

[0002]

BACKGROUND OF THE INVENTION Acrylic elastomers are generally known as rubbers having excellent heat resistance and oil resistance, and are used for various sealing materials and the like which are required to have these properties.

[0003]

Since the acrylic elastomer does not have a double bond in the polymer main chain, a cross-linking site-donating monomer is copolymerized, and a cross-linking agent is selected according to the cross-linking site. And cross-linking. Active halogen groups, epoxy groups, vinyl groups, etc. are used as the cross-linking sites. An acrylic elastomer having an active halogen group is inferior in metal corrosion resistance and water resistance because it is a by-product produced in the vulcanization process. Acrylic elastomers having an epoxy group have a slow vulcanization rate and require secondary vulcanization for a long time in order to obtain optimum vulcanization properties. Methods of vulcanizing the acrylic elastomer copolymerized with a diene compound include sulfur vulcanization and peroxide vulcanization. In particular, peroxide vulcanization is fast, and in some cases secondary vulcanization can be omitted, and the resulting vulcanizate is satisfactory in heat resistance and compression set resistance.
However, it has a drawback that the processability of the obtained polymer is poor because side reactions specific to the diene compound such as chain transfer reaction and gelation reaction occur during the polymerization reaction.

As a result of intensive studies by the present inventors, they have a methylene group or a methine group having an oxygen atom at the α-position,
The acrylic elastomer obtained by copolymerizing a compound having one polymerizable unsaturated group is capable of peroxide vulcanization and has good processability, and the vulcanized product obtained has heat resistance and compression set resistance. I found it to be good.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
(A) 30 to 99.5 parts by weight of at least one acrylate selected from alkyl acrylates in which the alkyl group has 1 to 8 carbon atoms, and (b) a methylene group or a methine group having an oxygen atom in the α-position. 0.5 to 30 parts by weight of a compound having one polymerizable unsaturated group, and
(C) It is achieved by copolymerizing 0 to 60 parts by weight of at least one other monomer copolymerizable with the above-mentioned components (a) and (b).

Examples of the component (a) monomer used in the present invention include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate,
Examples thereof include alkyl acrylates having an alkyl group having 1 to 8 carbon atoms such as octyl acrylate and cyanoethyl acrylate. The amount of these acrylates used is 30 to 99.5 parts by weight.

The monomer of the component (b) used in the present invention is a compound having a methylene group or a methine group having an oxygen atom at the α-position and having one polymerizable unsaturated group,
Used as a crosslinking site donating monomer. Specifically, it is a compound having an alkoxyalkylene group having 1 to 8 carbon atoms, a dioxymethylene group, or a cyclic ether group, and having one polymerizable unsaturated group. For example, ethoxymethyl acrylate, methoxyethyl acrylate, 3-methoxybutyl acrylate, ethoxyethoxyethyl acrylate, 1,2- (methylenedioxy) -4-propenylbenzene, 3,4- (methylenedioxy) -styrene, tetrahydroflur Furyl acrylate, tetrahydrofurfuryl methacrylate and the like can be mentioned.

The amount of these used is 0.5 to 30 parts by weight, preferably 1 to 10 parts by weight. These monomers are
If the amount is less than 5 parts by weight, satisfactory values cannot be obtained in the physical properties of the vulcanizate obtained, especially in the mechanical properties. On the other hand, if it is 30 parts by weight or more, the heat resistance of the obtained vulcanizate decreases. Also,
Some of these monomers have not only an effect as a crosslinking site donor but also an effect of improving physical properties such as cold resistance and oil resistance.

The monomer of component (c) used in the present invention is the mechanical properties of the resulting acrylic elastomer,
It is optionally used to improve oil resistance, cold resistance and the like. Specific examples include acrylonitrile, styrene, vinyl acetate, vinylidene chloride, acrylic acid, ethyl methacrylate, butanediol diacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, divinylbenzene, diallyl phthalate, and the component (b Alkoxy acrylates other than) may be used. The amount of these monomers used is 0 to 60 parts by weight.

The acrylic elastomer in the present invention is
The monomer component can be polymerized by a well-known polymerization method such as emulsion polymerization, suspension polymerization, solution polymerization and bulk polymerization using a commonly used radical initiator. Polymerization temperature is -20 to 100
C., preferably 0 to 80.degree. Since the elastomer obtained by the polymerization does not use a diene compound as a crosslinking site monomer, the above-mentioned side reaction cannot occur during the polymerization. Therefore, there is no problem in processability such as roll processability and vulcanization moldability.

In the acrylic elastomer of the present invention, the active methylene group and methine group having an oxygen atom at the α-position described above act as a crosslinking site for peroxide vulcanization. Examples of the organic peroxide include di-t-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butoxyperoxy) hexane, 1,3-bis-
(T-Butylperoxy-isopropyl) benzene or the like is used.

Further, if necessary, a reinforcing agent, a filler, a plasticizer, a processing aid, an antiaging agent, a crosslinking aid, a pigment and the like can be optionally mixed. The method for preparing the rubber composition of the present invention is not particularly limited, and the rubber composition can be prepared by adding the above-mentioned components and mixing them with an ordinary kneader such as a kneader, a Banbury mixer or an open roll. The rubber composition of the present invention thus obtained has a temperature of 150 ° C to 2 ° C.
Vulcanization can be performed at a temperature of about 00 ° C. for about 2 to 20 minutes. Further, secondary vulcanization may be performed at the same temperature.

[0013]

EXAMPLES The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to these examples. Parts are by weight unless otherwise specified. Examples 1, 2, 3, 4 and Comparative Example 200 parts of water, 2 parts of polyoxyethylene dodecyl ether, 0.8 part of sodium dodecyl sulfate, and Table 1 in a separable flask equipped with a stirrer, a thermometer, and a reflux condenser. 100 parts of a mixture of each monomer having the composition described in 1 above was charged, and the internal temperature was kept at 50 ° C. and the atmosphere was sufficiently replaced with nitrogen. Then, 0.2 part of ammonium persulfate and 0.2 part of sodium hydrogen sulfite were added to initiate polymerization. The polymerization temperature is 60 ° C. and the reaction time is 1.5 hours. After the completion of the polymerization, the polymerization product was salted out, washed thoroughly with water, and dried to obtain the target acrylic elastomer. Polymerization rate is 97%
That was all.

Table 1

After mixing the acrylic elastomer and the compounding agent by the open roll in the compounding recipe shown in Table 2,
It was vulcanized to obtain a vulcanized product. Then, various physical properties of each vulcanized product were measured according to JIS K-6301, and the values are shown in Table 3.

Table 2

Table 3

[0018]

EFFECTS OF THE INVENTION According to the present invention, an acrylic elastomer having good workability can be obtained, and furthermore, molding in a short time by peroxide vulcanization is possible. The vulcanizate obtained is
Good heat resistance and compression set resistance.

Claims (4)

[Claims] 1. (a) 30 to 99.5 parts by weight of at least one acrylate selected from alkyl acrylates in which the alkyl group has 1 to 8 carbon atoms, and (b) methylene having an oxygen atom in the α-position. Group or methine group,
0.5 to 30 parts by weight of a compound having one polymerizable unsaturated group, and (c) 0 to 60 parts by weight of at least one other monomer copolymerizable with the above components (a) and (b). A method for producing an acrylic elastomer capable of being vulcanized by an organic peroxide, which comprises copolymerizing a part of a copolymer. 2. The above-mentioned (b) has an alkoxyalkylene group having 1 to 8 carbon atoms and has a polymerizable unsaturated group of 1
The acrylic elastomer according to claim 1, which has one piece. 3. The acrylic elastomer according to claim 1, wherein (b) has a dioxymethylene group and has one polymerizable unsaturated group. 4. The acrylic elastomer according to claim 1, wherein (b) has a cyclic ether group and one polymerizable unsaturated group.