JPH03152113A - Vulcanizable acrylic elastomer composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition, containing a specific acrylic copolymer elastomer and a vulcanizing system component, excellent in storage stability, prevulcanization safety and scorch resistance, capable of rapidly vulcanizing and having active hydrogen groups in the molecule. CONSTITUTION:The objective composition containing (A) an acrylic copolymer elastomer composed of (i) 50-98.0wt.% at least one acrylic acid ester selected from the group of alkyl acrylates having a 1-8C alkyl group and alkoxyalkyl acrylates having a 1-4C alkoxy and 1-4C alkylene, (ii) 20-2.0wt.% active hydrogen group-containing monomer and (iii) 30-0wt.% copolymerizable monomer copolymerizable with the components (i) and (ii) and (B) a vulcanizing system component composed of (iv) a blocked polyfunctional isocyanate and (v) at least one organotin compound selected from the group of alkyltin oxides, fatty acid salts of alkyltins and alkyltin halides.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to vulcanizable acrylic elastomer compositions. More specifically, the present invention relates to a vulcanizable acrylic elastomer composition having an active hydroxyl group in the molecule, which has excellent storage stability and processing safety, and is rapidly vulcanized.

[Issues to be solved by the prior art/invention 11i1 As a vulcanizable acrylic elastomer composition with relatively good storage stability and processing safety, an acrylic elastomer having an active hydroxyl group in the molecule and its vulcanization system are used. Japanese Unexamined Patent Publication No. 52-
It is disclosed in Japanese Patent No. 72748.

The vulcanization system consists of (a) nadic anhydride or methylnadic anhydride, sulfur, and <C) a vulcanization accelerator such as tetramethylthiuram sulfide, 2-mercaptobenzothiazole, etc.

When this vulcanization system is used, a composition exhibiting relatively excellent properties in terms of processing safety, storage stability, and scorch stability can be obtained, but the vulcanization speed and vulcanizate There are many points in which improvements are required in terms of physical properties of vulcanizates such as compression set resistance. This is due to a vulcanization reaction: ■ an esterification reaction between the hydroxyl groups of the elastomer and the vulcanized nadic anhydride or methyl nadic anhydride; and ■ carbon-carbon unsaturated groups of the nadic anhydride or methyl nadic anhydride bonded to the elastomer. This is thought to be due to the fact that the crosslinking reaction with sulfur is achieved in two stages.

In addition, a method is known in which polymers containing active hydroxyl groups are crosslinked using polyfunctional isocyanates, but since the curing reaction starts at a relatively low temperature in this method, it is difficult to perform final processing such as rubber processing. In the case of a processing method that involves cross-circuiting and heat history during preforming before the sulfurization process, it is difficult to apply it in practice from the viewpoint of processing safety.

[Means for Solving the Problem] As a result of repeated studies on various vulcanization systems for acrylic elastomers having active hydroxyl groups in the molecule, the present inventors have found that the scorch resistance shown by storage stability, processing safety, etc. We have discovered an effective vulcanization system that can provide a vulcanized product with good properties, extremely rapid vulcanization, and excellent physical properties, and have completed the present invention.

That is, the present invention provides (A) (a) an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, and an alkoxyalkyl acrylate having an alkoxy group having 1 to 4 carbon atoms and an alkylene group having 1 to 4 carbon atoms; At least one acrylic ester selected from the group consisting of 50 to 98.0
% (wt%, the same applies hereinafter), (b) 20 to 2.0% of an active hydroxyl group-containing monomer, and (c) copolymerizability that can be copolymerized with the monomers of components (a) and (0) above. an acrylic copolymer elastomer consisting of 30 to θ% monomer; and (B) a blocked polyfunctional isocyanate and a silica alkyl tin oxide, an alkyl tin fatty acid salt, and an alkyl tin halide. The invention relates to a vulcanizable acrylic elastomer composition containing a vulcanizable component comprising at least one organic tin compound.

[Example] The acrylic elastomer having an active hydroxyl group in the molecule used in the present invention (component (A)) is composed of at least one acrylic ester selected from the group consisting of specific alkyl acrylates and alkoxyalkyl acrylates (
The main component is (component (a)), and the active hydroxyl group-containing monomer ((
It is a copolymer obtained by copolymerizing component (b)). The acrylic elastomer contains other copolymerizable monomers (component (c)) that can be copolymerized with these monomers as a copolymerization component.
may be copolymerized.

The active hydroxyl group serves as a crosslinking point during vulcanization,
Its content is 3.0 to 0 in the acrylic elastomer.
．． 1% is preferred. Acrylic elastomer obtained when the proportion is less than 0.1%, the vulcanization rate becomes slow and the vulcanizate tends not to exhibit sufficient physical strength for practical use.
．． If it exceeds 0%, the crosslinking density of the vulcanizate becomes too high and tends to lose its rubber elasticity.

The acrylic elastomer used in the present invention having active hydroxyl groups as described above is a random copolymer in which the copolymerizable monomer is uniformly distributed in the molecule, and has a Mooney viscosity (ML% 100°C) 1+4 of 20 It is preferable that it is 60.

The alkyl acrylate is an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, preferably 1 to 4 carbon atoms. When the number of carbon atoms exceeds 8, the oil resistance, which is a characteristic of acrylic elastomers, tends to be impaired.

Specific examples of the alkyl acrylate include methyl acrylate, ethyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate.

The alkoxyalkyl acrylate has 1 carbon atom
It is an alkoxyalkyl acrylate having ~4 alkoxy groups and an alkylene group having 1 to 4 carbon atoms.

When the number of carbon atoms in the alkoxy group or alkylene group exceeds 4, oil resistance tends to be impaired.

Specific examples of the alkoxyalkyl acrylate include methoxymethyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, butoxyethyl acrylate, and the like.

The proportion of units derived from the alkyl acrylate or alkoxyalkyl acrylate in the acrylic copolymer elastomer is 50 to 98.0%, preferably 80 to 98.0%.
%. When the proportion is less than 50%, the rubber elasticity of the acrylic elastomer obtained tends to be impaired.
If it exceeds 0%, the crosslinking density of the vulcanizate will not be sufficiently high.1. The physical properties required for practical use will no longer be satisfied.

The active hydroxyl group-containing monomer is not particularly limited as long as it has an active hydroxyl group that serves as a crosslinking point and is a copolymerizable monomer, and specific examples thereof include allyl alcohol,
2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 1.4
-butanediol monoacrylate, ethylene glycol monoallyl ether, diethylene glycol monoallyl ether, etc. Among these, 2-hydroxyethyl acrylate and 2-hydroxypropyl acrylate are particularly preferred from the viewpoint of copolymerization reactivity and crosslinking reactivity.

The number of units derived from the active hydroxyl base monomer in the acrylic copolymer elastomer may be one, or may be 2FIi or more.

The proportion of units derived from active hydroxyl group-containing monomers in the acrylic copolymer elastomer is 20 to 2.0%, preferably 10 to 4.0%.

The comonomer used as the VXJ component is not particularly limited, and specific examples thereof include acrylonitrile, methyl methacrylate, styrene, vinyl acetate, vinyl chloride, vinylidene chloride, ethyl vinyl ether, butyl vinyl ether, divinylbenzene, and ethylene glycol. Examples include vinyl monomers such as diacrylate, polyethylene glycol diacrylate, and allyl methacrylate.

The number of units derived from the copolymerizable monomer of component (iii) in the acrylic copolymer elastomer may be one type, and 2N
It may be more than that.

The proportion of units derived from the (/9 component) in the acrylic copolymer is 30 to 0%, preferably 20 to 0%. If the proportion exceeds 30%, the rubber elasticity and cold resistance of the vulcanizate will deteriorate. There is a tendency to damage the

The acrylic copolymer elastomer consisting of the above-mentioned components can be synthesized by various known polymerization methods, but in order to adjust the molecular weight and achieve uniform intramolecular distribution of each copolymerizable monomer, an emulsifier, an emulsifier, It is preferable to synthesize the monomer mixture by polymerizing a monomer mixture in an emulsion aqueous solution in the presence of a polymerization initiator and a polymerization regulator. Of course, the polymerization may also be carried out in solution or in bulk, for example by using heat or actinic radiation, with or without the presence of peroxides known to induce polymerization. Next, in the case of emulsion polymerization, salts are added to the copolymerization product to coagulate it, followed by washing and drying, or in the case of solution polymerization, the copolymerization product is evaporated to dryness. An acrylic polymer elastomer can be obtained by removing the solvent.

As the acrylic copolymer elastomer, 18 may be used, or two or more types may be used in combination.

The blending ratio of the acrylic copolymer elastomer in the composition of the present invention is preferably 40 to 85%, more preferably 45 to 75%. If the ratio is less than 40%, the rubber elasticity of the vulcanizate tends to be impaired, and if it exceeds 85%, the vulcanizate tends to be unable to have sufficient physical strength for practical use.

The composition of the present invention contains a blocked polyfunctional isocyanate (component) as a vulcanization component (component (B)).
In addition, at least one organic tin compound (9 components) selected from the group consisting of alkyl tin oxides, alkyl tin fatty acid salts, and alkyl tin halides is blended.

By using such vulcanization components, the composition of the present invention is stable up to a certain temperature, and when the temperature exceeds the certain temperature, the blocking agent of the polyfunctional isocyanate is removed and vulcanization begins. Vulcanization is accelerated by the action of organic tin compounds.

Examples of the blocked polyfunctional isocyanate include monofunctional active hydrogen-containing compounds (blocking agents)
Examples include polyfunctional isocyanates blocked with . In addition, polyfunctionality refers to an isocyanate having 2 or more, preferably 2 to 8, more preferably 2 to 4 incyanate groups in one molecule.

When the blocked polyfunctional incyanate is heated in the presence of a polymer having active hydroxyl groups, it decomposes into a polyfunctional isocyanate and a blocking agent, and the polyfunctional isocyanate bonds with the active hydroxyl groups of the polymer. On the other hand,
The blocking agent has the property of being regenerated as a monofunctional active hydrogen-containing compound.

Typical examples of the polyfunctional isocyanate include aliphatic isocyanates such as hexylene diisocyanate, hexylene diisocyanate trimer, octylene diisocyanate, and decylene hexadiisocyanate; toluene diisocyanate, diphenylmethane-4
゜4°-Aromatic isocyanates such as diisocyanate, toluene isocyanate, diphenyltetraisocyanate, naphthyltetraisocyanate; reaction product of 1 mole of diol such as isophorone diisocyanate with 2 moles of diisocyanate, reaction of 1 mole of triol with 3 moles of diisocyanate Examples include products.

Compounds suitable as blocking agents for isocyanates include, for example, aliphatic alcohols such as methanol, ethanol, and n-butyl alcohol; cycloaliphatic alcohols such as cyclohexanol; and aromatic-aliphatic alcohols such as phenylcarbinol and methylphenylcarbinol. Alcohol; Phenolic compounds such as phenol, cresol, nitrophenol, and ethylphenol; Oximes such as methyl ethyl titoxime, acetone oxime, and cyclohexanone oxime; Compounds with hydroxyl groups such as lactams such as ε-caprolactam, etc. However, lactams, particularly caprolactam, are preferred because the dissociation temperature of the blocking agent is between that of the usual pretreatment process (up to 130°C) and the vulcanization process (180°C or higher) in the rubber industry. Furthermore, when long-term storage stability is required, phenol and naphthol are also preferred from the viewpoint of stability of the blocking agent.

Preferred specific examples of the blocked polyfunctional isocyanate include ε-caprolactam adducts of isophorone diisocyanate.

The blocked polyfunctional incyanate is prepared by reacting a polyfunctional isocyanate with at least a stoichiometric equivalent of a monofunctional active hydrogen-containing compound.

For example, when a lactam is used as a blocking agent, the formula: A polyfunctional incyanate blocked by a reaction represented by a divalent organic residue having or not having a group, n being an integer of 2 or more, preferably 2 to 8, more preferably 2 to 4. I can be hatched.

18i may be used as the blocked polyfunctional incyanate, or two or more types may be used in combination.

The blending ratio of blocked polyfunctional incyanate is
It is preferably 0.1 to 20 parts, and 2.0 to 1
0.0 part is more preferred. If the proportion is less than 0.1 part, sufficient crosslinking density cannot be achieved and a vulcanizate with low physical strength tends to be obtained, and if it exceeds 20 parts, it bleeds to the surface,
It tends to impair workability, such as contaminating the vulcanization mold.

ll of the organotin compound! Specific examples of alkyltin oxides or fatty acid salts include dibutyltin oxide, dioctyltin oxide, dibutyltin diacetate, dibutyltin dichloride, dibutyltin dilaurate, dibutyltin distearate, and dibutyltin simalate.

Specific examples of alkyltin halides include dibutyltin dichloride and di-n-octyltin dichloride.

Among such organic tin compounds, dibutyltin distearate and dibutyltin dilaurate are preferred from the viewpoint of miscibility in rubber compounds and crosslinking reaction promoting effect.

The blending ratio of the organic tin compound is preferably 0.01 to 10 parts, more preferably 0.05 to 2.0 parts, per 100 parts of the acrylic copolymer elastomer.

The ratio is 0. If it is less than 10 parts, the vulcanization rate decreases, and under normal vulcanization conditions, the vulcanizate tends to have poor compression set properties, and if it exceeds 10 parts, vulcanization is accelerated and early vulcanization stability is impaired. Tend.

In addition to the above-mentioned components, the composition of the present invention usually contains reinforcing agents, fillers, etc. within a range that does not impair the effects of the present invention, and if necessary, anti-aging agents, stabilizers, and plasticizers. , processing aids, etc. are added.

There are no particular limitations on the method for preparing the composition of the present invention, and for example, an acrylic copolymer elastomer, a vulcanization component, and other compounding agents are generally used in the rubber industry using an oven mill roll, intensive mixer, etc. It can be prepared by mixing according to a mixing method according to the present invention.

Vulcanization of the composition is usually carried out by heating at a temperature of 140°C or higher, preferably at a temperature of about 170 to 200°C for about 20 to 1 minute. Further, when post-vulcanization is performed, it is waited at a temperature of about 150 to 180°C for 5 to 1 hour.

The acrylic elastomer composition of the present invention exhibits excellent stability against storage and early vulcanization, and exhibits extremely favorable effects such as providing a vulcanized product with good heat aging resistance and compression set resistance. . With the acrylic elastomer composition of the present invention, it is possible to omit or shorten post-vulcanization, which has traditionally been a problem due to the delayed vulcanization of acrylic elastomers, and it also has particularly important required properties from the viewpoint of the use of acrylic elastomers. It has the remarkable effect of efficiently improving compression set resistance.

The vulcanizate obtained from the composition of the present invention has excellent properties such as heat aging resistance, compression set, oil resistance, weather resistance, and ozone resistance, so these properties can be effectively utilized. and various seals (gaskets, backings,
-rings, oil seals, etc.), various hoses, coating materials, and various belts and rolls.

Next, the present invention will be explained in more detail based on Examples.

Production Examples 1 and 2 (Synthesis of acrylic copolymer elastomer) Comonomer mixture (^) or (B) having the composition shown in Table 1
400 parts, polyoxyethylene dodecyl ether 4
parts, sodium dodecyl sulfate 1.5 parts and water 200 parts
Stir and emulsify the remaining portion using a homomixer, and add 4 ml of water in advance.
00 parts was charged into a reaction vessel containing 1,000 parts, and the solution was sufficiently nitrogen-substituted while stirring and maintaining the liquid temperature at 5°C. Next, 0.2 parts of cumene hydroperoxide, 0.0 part of ferrous sulfate
When 1 part of sodium formaldehyde sulfoxylate and 10.2 parts of sodium formaldehyde sulfoxylate were sequentially added, the polymerization reaction started and the temperature began to rise. When the temperature of the content liquid reached 30° C., the copolymerization reaction was completed by stirring for about 3 hours while maintaining the temperature.

The obtained copolymerization product was poured into 15% saline solution at about 80°C to coagulate the copolymer, washed with water, and dried to obtain an acrylic copolymer elastomer (A) using the monomer mixture (A). A
) and the monomer mixture (B) were used to obtain an acrylic copolymer elastomer (B).

Table 1 Examples 1 to 4 and Comparative Examples 1 to 5 The acrylic copolymer elastomer (A) or (B) and the compounding ingredients shown in Table 2 were kneaded with a 6-inch roll for 20 minutes, An acrylic elastomer composition was prepared.

JIS K 630 for prepared compositions that are subjected to rinsing for one day or left at room temperature for two weeks.
A Mooney scorch test was conducted in accordance with the 0r Unvulcanized Rubber Test Method.

In addition, a vulcanized product was produced by press-curing the composition aged for one day at 180°C for 10 minutes, and its properties were evaluated by JI
It was evaluated in accordance with the SK 6301r physical test method for vulcanized rubber. On the other hand, the obtained vulcanizate was allowed to deteriorate in air at 175° C. for 70 hours, and changes in properties were examined. The results are shown in Table 2.

A vulcanization curve for vulcanization curing of the composition aged for 10 more times at 180° C. was prepared based on the results of measurement using an oscillating disc rheometer (ASTM-100 model manufactured by Toyo Seiki Seisakusho ■). The vulcanization curve is shown in FIG.

By comparing the results of the example and the results of the comparative example shown in Table 2 and FIG. 1, the following can be found.

■A comparison between Examples 1 to 4 and Comparative Examples 1 to 2 shows that the vulcanization system of the present invention using a blocked polyfunctional isocyanate and an organic tin compound is better than the vulcanization system using an unblocked incyanate. It can be seen that the scorch resistance and storage stability are superior to vulcanized systems.

■From the results of Comparative Example 3, when unblocked isocyanate is used without the presence of organotin, the vulcanization rate immediately after cross-crossing and scorch resistance are well balanced, but it is not practical in terms of storage stability. It turns out that he lacks sex.

■A comparison between Examples 1 and 2 and Comparative Example 4 shows that the vulcanization system using blocked polyfunctional incyanate alone does not exhibit the effect of accelerating vulcanization, and vulcanization is accelerated by the accelerating effect of the organotin compound. It can be seen that the processing speed is increased, and the scorch resistance and storage stability are maintained.

(2) A comparison between Example 1 and Comparative Example 5 shows that melamine derivatives, which are often used as crosslinking agents for active hydroxyl group-containing polymers, cannot provide a vulcanizable composition that can be sufficiently vulcanized.

(2) It is clear from the vulcanization curve shown in FIG. 1 that the acrylic elastomer composition of the present invention has excellent early vulcanization stability and rapid vulcanization characteristics.

[Effect of the invention] The acrylic elastomer composition of the invention has storage stability,
The composition has excellent scorch resistance as seen in early vulcanization safety, as well as excellent vulcanization speed and physical properties of the vulcanizate.

[Brief explanation of the drawing]

FIG. 1 is a graph showing each vulcanization curve prepared in Examples 1 to 4 and Comparative Examples 1 to 5.

Claims (1)

[Scope of Claims] 1 (A) (a) Alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and alkoxyalkyl having an alkoxy group having 1 to 4 carbon atoms and an alkylene group having 1 to 4 carbon atoms At least one type of acrylic ester selected from the group consisting of acrylates 50 to 98
．． 0% by weight, (b) 20 to 2.0% by weight of an active hydroxyl group-containing monomer, and (c) 30% of a copolymerizable monomer that can be copolymerized with the monomers of components (a) and (b). ~0% by weight of an acrylic copolymer elastomer; (B) (d) blocked polyfunctional isocyanate and (e) alkyltin oxide, alkyltin fatty acid salt, and alkyltin halide selected from the group consisting of A vulcanizable acrylic elastomer composition comprising a vulcanizable component comprising at least one organic tin compound.