JPH0118937B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing an acrylic elastomer. More specifically, the present invention relates to a vulcanizable acrylic elastomer that can provide excellent properties such as kneading processability, rapid vulcanization, metal corrosion resistance, and water resistance, and a method for vulcanizing the same. Acrylic elastomers are used as elastomers for various sealing materials (packing, O-rings, gaskets, ), hoses, electrical parts, coating materials, etc. Acrylic elastomers include acrylic copolymer elastomers obtained by copolymerizing acrylic esters as main monomers and ethylene-acrylate copolymer obtained by copolymerizing ethylene and acrylic esters or methacrylic esters as main monomers. Two types of polymer elastomers are currently in industrial use. These copolymer elastomers are all copolymerized with a small amount of crosslinking site donating monomer, and by selecting a vulcanization system according to the type of crosslinking site, the vulcanization reaction can be carried out efficiently. is being carried out. The following vulcanizing agent systems are used depending on the type of crosslinking site.

[Table] Ru group Mine or polyamine derivative-base Among these crosslinking sites, active halogen groups include, for example, 2-chloroethyl vinyl ether, vinyl chloroacetate, vinylbenzyl chloride, vinylcubenzyl chloroacetate, 2-chloroethyl acrylate, etc. It is obtained by copolymerizing and can be vulcanized using the above-mentioned vulcanizing agent system, but it has the disadvantage of poor metal corrosion resistance due to hydrogen halide or its salts generated during the vulcanization reaction. Alkaline soap - When sulfur or a sulfur-donating compound is used as a vulcanizing agent, a decrease in water resistance and electrical properties is unavoidable due to the inclusion of the highly hydrophilic alkali soap. In addition, when epoxy groups are introduced as crosslinking sites by copolymerizing glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, vinyl glycidyl ether, etc., metal corrosion is not observed during vulcanization or in the vulcanized product. , the balance between vulcanization rate and fabric scorchability is not sufficient. That is, when a fast vulcanization rate is obtained, the scorch property is significant, and the processing safety during kneading and the storage stability of the dough are unsatisfactory. vice versa,
If the scorch property is in a satisfactory state, the vulcanization rate will be slow, which will hinder the efficiency of the vulcanization molding process. When an alkali soap-sulfur or sulfur-donating compound is used as the vulcanizing agent system, the water resistance of the vulcanizate is reduced, as in the case of active halogen group crosslinking sites. Furthermore, in the case of carboxyl group crosslinking sites introduced by copolymerizing acrylic acid, methacrylic acid, maleic acid monoester, itaconic acid, etc., vulcanizates with less metal corrosion and low compression set can be obtained. However, since the vulcanization rate is not necessarily high, similar to the case of the epoxy group crosslinking site, a decrease in scorch property is often a problem when trying to increase the vulcanization rate. In addition, there is a problem that during kneading processing, there is a tendency to stick to the metal parts of the kneading parts of rolls, kneaders, Banbury mixers, etc., which requires extra labor. The present invention solves the problems encountered with the conventional acrylic elastomers described above, that is, a sufficiently fast vulcanization rate can be obtained, and at the same time, it has excellent scorch resistance (processing safety, storage stability of fabrics), and The purpose of this invention is to provide a method for producing a new vulcanizable acrylic elastomer with excellent kneading processability (adhesion during kneading), metal corrosion resistance, water resistance, etc. The purpose of the present invention is to copolymerize an oxazoline ring-containing monomer as a crosslinking site component into an ethylene-acrylate elastomer, and further utilize the reactivity of the oxazoline groups distributed in the side chains of the polymer to form polymercapto groups. It has been found that this can be achieved by vulcanization in the presence of the containing compounds. Therefore, the present invention provides novel vulcanizable ethylene-
Regarding the manufacturing method of acrylate elastomer, this ethylene-acrylate elastomer is manufactured by the following (a)
Component (b) and (c) are copolymerized to produce a compound from the group consisting of (a) 15 to 60% by weight of ethylene, and (b) alkyl acrylates and alkyl methacrylates in which the alkyl group has 1 to 4 carbon atoms. 80-30% by weight of at least one selected acrylate and (c)2
Oxazoline ring-containing monomer with an unsaturated group in position
It is manufactured as an ethylene-acrylate elastomer consisting of 15-0.1% by weight. The copolymerization reaction for obtaining an oxazoline group-containing ethylene-acrylate elastomer is, for example, the high-pressure polymerization method described in U.S. Pat. No. 2,599,123 and U.S. Pat. This is carried out in accordance with the low-pressure alternating polymerization method. Comonomer component (b) used as the main monomer together with ethylene includes methyl acrylate,
Mention may be made of alkyl acrylates or alkyl methacrylates in which the alkyl group has 1 to 4 carbon atoms, such as ethyl acrylate, n- or isopropyl acrylate, n- or isobutyl acrylate or the corresponding methacrylates. The reason why the number of carbon atoms in the alkyl group is limited to 1 to 4 is because if the number of carbon atoms increases more than this, the oil resistance becomes poor. Although the copolymers obtained by copolymerizing ethylene with alkyl acrylates and/or alkyl methacrylates can have any desired composition, for the purposes of the present invention,
Ethylene must be copolymerized and contained in a proportion of 15 to 60% and alkyl acrylate and/or alkyl methacrylate in a proportion of 80 to 30% based on the total comonomer weight. Examples of the oxazoline ring-containing monomer having an unsaturated group at the 2-position of the comonomer component (c) include 2-vinyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-iso propenyl-2-
Examples include oxazoline, and the total monomer weight is
It is used in a proportion of 15 to 0.1%, preferably 10 to 0.5%. If the usage ratio is less than this, a sufficient amount of crosslinking sites will not be introduced into the copolymer elastomer, and
On the other hand, if it is used in excess of this, the crosslinking density of the vulcanizate generally increases, the elongation rate decreases, the rubber-like elasticity becomes poor, and physical properties such as heat aging resistance and compression set are also adversely affected. Vulcanization of the oxazoline group-containing ethylene-acrylate elastomer can be easily carried out by heating in the presence of a polymercapto compound containing two or more mercapto groups such as a thiol group, thiocarboxyl group, or thiophenol group. . Examples of polymercapto compounds include 1,
6-dimercaptohexane, dimercapto diethyl ether, 1,5- or 2,7-dimercaptonaphthalene, 2,2-dimercapto diethyl sulfide, 2-dibutylamino-4,6-dithiol-s-triazine, 2-phenylamino-
4,6-dithiol-s-triazine, 1,4-
Dimercapto-2,3-butanediol, 2,5
-dimercapto-1,3,4-thiadiazole,
At least one such as 3,4-dimercaptotoluene
The seeds are used in a proportion of about 0.2 to 10 parts by weight, preferably about 0.5 to 5 parts by weight, per 100 parts by weight of elastomer. This usage ratio is selected as a preferable range from the viewpoint of various characteristics and properties such as vulcanization rate, scorch resistance, mechanical properties of the vulcanizate, heat aging resistance, and compression set. In other words, if the proportion is less than this, the vulcanization rate will drop considerably and the general physical properties of the vulcanizate will not be satisfactory, whereas if it is used above this, the vulcanization rate will generally increase. However, scorch resistance (processing safety,
Storage stability), general properties of the vulcanizate, etc. are often impaired, and it is inefficient, both of which are undesirable. In the vulcanization operation, this vulcanizing agent component is usually mixed with other ingredients such as reinforcing agents, fillers, vulcanization accelerators, anti-aging agents, stabilizers, plasticizers, etc.
The mixture is mixed with the elastomer together with a lubricant, a processing aid, etc. by a commonly used mixing method such as roll mixing, Banbury mixing, kneader mixing, solution mixing, etc., and then heated. The vulcanization temperature is generally about 120°C or higher, preferably about 150°C.
Temperatures of 0.degree. C. or higher are used. Next, the present invention will be explained with reference to examples. (Example of synthesis of ethylene-acrylate elastomer) After sufficiently purging the inside of the heat-resistant polymerization tube with nitrogen, 100 parts of methyl acrylate (weight, same hereinafter), 8 parts of 2-vinyl-5-methyl-2-oxazoline, and tertiary butanol were added. Charge 300 parts and 0.4 part of azobisisobutyronitrile, then raise the internal temperature to about 70°C, and then pressurize ethylene until the internal pressure reaches about 1000 kg/cm ² . During the reaction, ethylene was intermittently fed for 10 hours at a temperature of approximately 75°C and approximately
The pressure was maintained at 900-1000Kg/ ^cm2 . After the reaction is complete,
After exhausting unreacted monomers, steam cleaning, drying,
Ethylene-acrylate elastomer A was obtained. The obtained copolymer elastomer had a composition consisting of 42.5% by weight of ethylene, 54.3% by weight of methyl acrylate, and 3.2% by weight of 2-vinyl-5-methyl-2-oxazoline from the results of elemental analysis. The viscosity ηsp/c (85°C, 0.2% xylene solution) was 0.72 dl/g. (Comparative Example of Synthesis of Ethylene-Acrylate Elastomer) A copolymerization reaction was carried out in the same manner as in the above Example, using 16 parts of ethylhydrodiene malate in place of 8 parts of 2-vinyl-5-methyl-2-oxazoline, and -Acrylate elastomer B
I got it. The obtained copolymer elastomer has a composition consisting of 41.3% by weight of ethylene, 54.2% by weight of methyl acrylate, and 4.5% by weight of ethylhydrogen malate, and has a solution viscosity of η sp/c (85 °C, 0.2% xylene solution) is 0.68
It was dl/g. (Vulcanization) For each of the obtained elastomers, the compounding ingredients shown in the following Table 1 to () were kneaded using a 4-inch open roll to prepare each vulcanizable compounded composition. Note that all numbers with brackets are comparative examples.

【table】

[Table] Mooney viscosity and scorch time (time required for Mooney viscosity to reach minimum value + 5) for each vulcanizable compound composition prepared, and as a guideline for processing safety and storage stability. ) was measured at 121°C. Additionally, the composition may be added to 180%
Press vulcanization was carried out at 175°C for 6 minutes, followed by secondary vulcanization in an oven at 175°C for 4 hours. The physical properties of the obtained vulcanizate were measured according to JIS K-6301, and the results are shown in Table 2 below. In addition, in the metal corrosion test, a vulcanized rubber sheet (thickness 2 mm) was placed on a cold rolled steel plate (SPCC-SB), and after leaving it in an oven at 150°C for 72 hours, the vulcanized rubber sheet was removed. The steel plate was left in a constant temperature and humidity chamber at a relative humidity of 60% and a temperature of 25°C for 10 days, and the degree of corrosion was evaluated based on discoloration of the steel plate surface.

【table】

[Table] From the above results, the ethylene-acrylate elastomer according to the present invention has an oxazoline group that serves as a crosslinking site in its copolymer side chain, so it can be effectively vulcanized by a polymercapto compound, and its It can be seen that the vulcanizate exhibits excellent mechanical properties, heat aging resistance, metal corrosion resistance, and water resistance, and is also excellent in terms of kneading workability and the balance between vulcanization rate and scorch resistance.

Claims (1)

[Claims] 1. (a) 15 to 60% by weight of ethylene, characterized by copolymerizing the following components (a), (b) and (c);
(b) 80 to 30% by weight of at least one acrylate selected from the group consisting of alkyl acrylates and alkyl methacrylates in which the alkyl group has 1 to 4 carbon atoms; and (c) an unsaturated group at the 2-position. A method for producing a vulcanizable ethylene-acrylate elastomer comprising 15 to 0.1% by weight of an oxazoline ring-containing monomer.