JPH03168208A - Production of vulcanizable acrylic rubber and vulcanized composition thereof - Google Patents

Abstract

PURPOSE:To obtain the subject rubber having excellent vulcanization rate, storage stability and heat-resistance and giving a vulcanized product having low compression set by polymerizing a cyanoalkyl (meth)acrylate, an acrylic acid ester and a comonomer in the presence of a radical initiator. CONSTITUTION:The objective vulcanizable acrylic rubber can be produced by polymerizing (A) 0.1-40wt.% of a cyanoalkyl (meth)acrylate of formula (R<1> is H or methyl; R<2> is cyano-substituted alkyl) (e.g. 2-cyanoethyl acrylate), (B) 60-99.9wt.% of an alkyl acrylate or an alkoxyalkyl acrylate (e.g. 2-methoxyethyl acrylate) and (C) 0-50wt.% of a monomer copolymerizable with the above monomers (e.g. acrylonitrile) in the presence of a radical initiator (e.g. t-butyl hydroperoxide).

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides a novel method for producing acrylic rubber having crosslinking points, and a method for producing an acrylic rubber having excellent vulcanization rate, storage stability, and heat resistance, and particularly excellent compression set. The present invention relates to a novel acrylic rubber vulcanizate which provides a vulcanizate.

[Prior Art] Acrylic rubber is known as a rubber with excellent heat resistance and oil resistance, and is widely used mainly in automobile parts. Acrylic rubber is a copolymer of an acrylic ester as a main component and a monomer having an active functional group that acts as a crosslinking point.

Typical monomers used as crosslinking points include active halogen-containing monomers such as 2-chlorovinyl ether, vinyl chloroacetate, allyl chloroacetate, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, etc. Eboxy group-containing monomers: Unsaturated carboxylic acids such as acrylic acid and methacrylic acid are conventionally known.

As vulcanizing agents for acrylic rubber, polyamines, metal soap/sulfur combination systems, ammonium salts such as ammonium benzoate, dithiocarbamates such as zinc dimethyldithiocarbamate, etc. are usually used, but the vulcanization rate is low and unsatisfactory. In order to obtain a vulcanizate with good vulcanizable properties, a long post-vulcanization process is required, and in the case of acrylic rubber that uses active halogen-containing monomers as crosslinking points, the mold may corrode during vulcanization. There was a problem with that.

[Problems to be Solved by the Invention] As a result of various studies to solve the above problems, the present inventors found that acrylic rubber containing two or more cyanoalkyl esters of acrylic acid or methacrylic acid in the molecule. a polyepoxy compound having an epoxy group, and a fourth
Vulcanization is possible by using grade ammonium salts or quaternary phosphonium salts as a vulcanizing agent, and the vulcanizate has a high vulcanization rate and has sufficiently satisfactory physical properties in a short vulcanization time. I found out.

[Means for Solving the Problems] The present invention is directed to the production of vulcanizable acrylic rubber, characterized in that the following monomers (A), CB) and (C) are polymerized in the presence of a radical initiator. Method, (A) Acrylic acid cyanoalkyl ester or methacrylic acid cyanoalkyl ester represented by the formula 0 1 (wherein R is hydrogen or a methyl group, and R2 is a cyano group-substituted alkyl group), 0.1 to 40% by weight, and (B) acrylic acid alkyl esters or acrylic acid alkoxyalkyl esters, 60 to 99.9% by weight (C) Monomers copolymerizable with these, 0 to 5'0% by weight, and [11 A) Acrylic acid cyanoalkyl ester or methacrylic acid cyanoalkyl ester represented by the formula (where R1 is hydrogen or a methyl group, and R2 is a cyanol ester group), 0.1 to 40% by weight, B ) Acrylic acid alkyl esters or acrylic acid alkoxyalkyl esters, 60 to 99.9tf
H amount % C) Monomer copolymerizable with these, 0 to 50
[0.1 to 10 parts by weight of a polyepoxy compound having at least two or more epoxy groups in two molecules; An acrylic rubber vulcanized composition containing 0.1 to 10 parts by weight of a quaternary phosphonium salt.

Acrylic rubbers containing cyanoalkyl esters of acrylic acid or methacrylic acid are already known. (For example, JP-A-43-24200, JP-A-50-1565
(No. 59, No. 60-203614, No. 60-203615, No. 60-203616, etc.) However, all of these acrylic rubbers contain unsaturated groups, active halogen-containing groups, epoxy groups, etc. in addition to cyanoalkyl esters of acrylic acid or methacrylic acid. The acrylic rubber containing structural units derived from a monomer having an active functional group as a crosslinking point, and the acrylic rubber having only a cyanoalkyl ester of acrylic acid or methacrylic acid as a crosslinking point, as in the present invention, is known. It wasn't.

The monomer component (A) is acrylic acid cyanoalkyl ester or methacrylic acid cyanoalkyl ester represented by formula (1), and examples of R2 in the formula include 2-cyanoethyl group, 2-cyanoprobyl group, -cyanoprobyl group, 3-cyanobutyl group, 2-cyanobutyl group, 3-
Examples include cyanobutyl group. The amount of the monomer (A) used in the present invention is 0.1 to 40% by weight, preferably 1 to 20% by weight. If the amount used is too small, vulcanization will not proceed sufficiently and If it is too high, a problem arises in that the compression set of the vulcanizate worsens.

Specific examples of acrylic acid cyanoalkyl ester or methacrylic acid cyanoalkyl ester include 2-cyanoethyl acrylate, 2-cyanoprobyl acrylate, 3-cyanopropyl acrylate, 2-cyanoptyl acrylate, and 2-cyanoethyl methacrylate. , 2-cyanobrovir methacrylate, 3-cyanoprovir methacrylate, and 2-cyanobutyl methacrylate.
Particularly preferred is cyanoethyl. These can be used alone or in combination of two or more.

The monomer component (B) is an acrylic acid alkyl ester or an acrylic acid alkoxyalkyl ester, and the amount used is 60 to 99.9% by weight. Specifically, methyl acrylate, ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, tert-butyl acrylate, probyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, and lauryl acrylate. , acrylic acid alkyl esters in which the alkyl group has 1 to 20 carbon atoms such as stearyl acrylate: methoxymethyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, butoxyethyl acrylate,
Examples include acrylic acid alkoxyalkyl esters having an alkoxyl group or an alkylene group having 1 to 4 carbon atoms, such as methoxyethoxyethyl acrylate. These can be used alone or in combination of two or more.

The monomer component (C) is a component that can be copolymerized with the monomer components (A) and (B). A certain amount of the monomer (C) may include the above monomer components (C) within a range that does not impair the effects of the present invention.
Can be used with A) and (B).

The amount of monomer (C) to be used within a range that does not impair the effects of the present invention varies depending on the monomer selected, but is usually 50% by weight or less, preferably 30% by weight or less. Specific examples of the monomer (C) include methyl methacrylate,
Methacrylic acid alkyl esters in which the alkyl group has 1 to 20 carbon atoms, such as ethyl methacrylate, butyl methacrylate, octyl methacrylate, lauryl methacrylate, and stearyl methacrylate: methoxymethyl methacrylate, methoxyethyl methacrylate, ethoxyethyl methacrylate , methacrylic acid alkoxyalkyl esters such as ptoxyethyl methacrylate and methoxyethoxyethyl methacrylate; acid or methacrylic acid hydroxyalkyl ester two general formulas, R3 1 10-1n-R4 (where R3 is hydrogen or methyl group, R4 has 1 carbon number
-8 alkyl group or alkoxyalkyl group having 3 to 8 carbon atoms, the number average value of n is 1 to 10) Vinyl esters such as vinyl acids: styrene,
Aromatic vinyl compounds such as α-methylstyrene Vinyl or vinylidene nitrile compounds such as acrylonitrile and methacrylonitrile: α- such as ethylene and brobylene
Conjugated olefins such as butadiene and isobrene: dimethyl maleate, diethyl maleate, di-n-butyl maleate, dimethyl fumarate, diethyl fumarate, di-n-butyl fumarate, etc., where the alkyl group has 1 to 20 carbon atoms
Dialkyl esters of unsaturated dicarboxylic acids: Dialkoxyalkyl esters of unsaturated carboxylic acids such as dimethoxyethyl maleate and dimethoxyethyl fumarate: Vinyl ketones such as methyl vinyl ketone and ethyl vinyl ketone; Particularly preferred are alkyl esters, alkoxy esters, and cyanoalkyl esters of methacrylic acid. These can be used alone or in combination of two or more.

The polymerization is carried out by commonly known radical initiator-based polymerization, such as emulsion polymerization, solution polymerization, bulk polymerization, and the like.

Among these, emulsion polymerization is particularly preferred.

As radical initiators, inorganic or organic peroxides,
Commonly known initiators such as persulfates, redox initiators, and azo initiators can be used.

Polymerization can be carried out at a temperature range of 0 to 100°C, preferably 5 to 80°C, and is usually carried out in the presence of a chain transfer agent such as an alkylmercabutane to control the molecular weight.

The copolymer obtained by polymerization can be easily isolated by using an aqueous solution of an inorganic salt such as calcium chloride or sodium chloride, or a copolymer-insoluble solvent, and then washed and dried to obtain the desired acrylic rubber. can.

The acrylic rubber obtained by the production method of the present invention can be vulcanized by using a polyepoxy compound having two or more epoxy groups in the molecule, and quaternary ammonium salts or quaternary phosphonium salts as a vulcanizing agent. is possible.

The acrylic rubber in the vulcanized composition of the present invention is A) acrylic acid cyanoalkyl ester or methacrylic acid represented by the formula O 1 (where R is hydrogen or methyl M, and R2 is a cyano ester group). Cyanoalkyl ester, 0.1-40ff
iffi%, B) Acrylic alkyl esters or acrylic acid alkoxyalkyl esters, 60-99.
9% by weight, C) Monomers copolymerizable with these, 0 to 50
% by weight. This acrylic rubber is not limited to the above manufacturing method.

Specific examples of the polyepoxy group-containing compound used in the vulcanized composition of the present invention include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, hydrogenated bisphenol A diglycidyl ether,
Diglycidyl ether of bisphenol A propylene oxide adduct, bisphenol PA diglycidyl ether, tetrakis 4-hydroxyphenyl)ethane diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether Ether, 1,4-butanediol diglycidyl ether, neobentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin diglycidyl ether, trimethylolbroban triglycidyl ether,
Phthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, 3゛ 4゜ monoepoxycyclohexylmethyl-3.4. Mono-Eboxycyclohexanecarboxylate, 3,4-Eboxycyclohexyloxirane, Bis(3,4-Eboxycyclohexylmethyl)Adibate, Bis(3,4-Eboxy-6-Methylcyclohexylmethyl)Adipate, 2-(3' ,4
Examples include 1-epoxycyclohexene-1,3-dioxane, triglycidyl aminophenol, triglycidyl isocyanurate, and the like. These may be used alone or in combination.

The amount of the polyepoxy group-containing compound used in the vulcanized composition of the present invention is 0.5 to 10 parts by weight, more preferably 1 to 5 parts by weight, based on 100 parts by weight of the acrylic rubber of the present invention. If the amount of the polyeboxy group-containing compound is less than 0.5 parts by weight, a vulcanizate with sufficient crosslink density cannot be obtained, and if it exceeds 10 parts by weight, the crosslink density becomes extremely high and the vulcanizate cannot be used for practical purposes. Unable to obtain sulfur.

The quaternary ammonium salt and quaternary phosphonium salt in the vulcanized composition of the present invention are compounds represented by the general formula. Y in the general formula is a nitrogen or phosphorus atom, R5 to R8
is a hydrocarbon group having about 1 to 25 carbon atoms such as an alkyl group, an alkoxyalkyl group, a polyoxyalkylene group, an aryl group, an alkylaryl group, and at least one of these contains an unsaturated bond or a hydroxyl group. May be replaced with 5. Furthermore, two or three of R - R8 may form a heterocyclic ring together with a nitrogen atom or a phosphorus atom.

X- is an anion derived from an inorganic or organic acid in which an acidic hydrogen ion is bonded to a halogen or oxygen; CI- Br- 1-CIO'-
BF'- BH4- RSO'- HSO'RO
SO'- RCOO- H2PO'-ROPO'-
Examples include anions such as (RO) 2P02H- (R in the formula represents an alkyl group, an aryl group, an alkylaryl group, or an alkoxyalkyl group having about 1 to 25 carbon atoms).

Examples of quaternary ammonium salts include tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, tetramethylammonium p-1 luenesulfonate, tetramethylammonium sulfate, tetraethylammonium chloride, tetraethylammonium bromide,
Tetraethylammonium iodide, tetra n-butylammonium chloride, tetra n-butylammonium bromide, tetra n-butylammonium hydrogen sulfite, tetra n-butylammonium perchlorate, tetra n-butylammonium phosphate, tetra n-butylammonium acetate , tetra n-butylammonium borohydride, decyltrimethylammonium bromide, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, stearyltrimethylammonium bromide, penzyltrimethylammonium chloride, penzyltriethylammonium iodide, penzylhexadecyldimethylammonium chloride , phenyltriethylammonium chloride, benzyldimethylenylammonium chloride, (2-methoxyethoxyethyl)ammonium chloride, choline chloride, dodecylpyridinium chloride, hexadecylpyridinium bromide, 2,4.6-trimethylpyridinium p- Toluene sulfonate, 1.8-
Examples include diazabicyclo(5.4.0)undecene-7-benzylammonium chloride, hexadecyltrimethylalkylphenoxypoly(ethyleneoxy)ethylammonium phosphate, and the like.

Examples of quaternary phosphonium salts include pendyltriphenylphosphonium chloride, methyltriphenylphosphonium bromide, methyltriphenylphosphonium sulfate, hexadecyltriphenylphosphonium bromide, ethyltriphenylphosphonium quaride, amyltriphenylphosphonium bromide, and tetraphenylphosphonium bromide. n-
Examples include butylphosphonium bromide, tetraphenylphosphonium bromide, trioctyl phenylphosphonium dimethyl phosphate, trioctyl phenylphosphonium acetate, bromomethyltriphenylphosphonium bromide, allyltriphenylphosphonium bromide, and the like.

These quaternary ammonium salts or quaternary phosphonium salts can be used alone or in combination of two or more.

The amount of quaternary ammonium salt or quaternary phosphonium salt used is 0.000 parts by weight per 100 parts by weight of the acrylic rubber of the present invention.
The amount is 5 to 10 parts by weight, preferably 1 to 5 parts by weight. If the amount used is less than 0.5 ffi parts, the vulcanization rate is low and a vulcanizate with satisfactory physical properties cannot be obtained, or it takes a long time to obtain a vulcanizate with satisfactory physical properties. If the weight part is exceeded, the vulcanization rate will be extremely high, and processing stability and
Storage stability is impaired.

The vulcanized composition of the present invention comprises the acrylic rubber of the present invention, a polyepoxy compound, a quaternary ammonium salt or a quaternary phosphonium salt, and ureas, as well as reinforcing agents, fillers, stabilizing agents, etc. commonly known in the rubber industry. It is prepared by adding additives, plasticizers, processing aids, etc., and mixing with a roll or a kneader such as a Banbury. The resulting product is molded into a desired shape and then vulcanized to become a final product. Vulcanization is usually carried out at temperatures above 120°C, preferably from 150 to 250°C, for 1 to 60 minutes. If necessary, further heat at a temperature of 150 to 200℃ for 1 to 24 hours.
time, post-vulcanization is performed.

The composition of the present invention has a high vulcanization rate, has no mold corrosion problem, and has a shorter vulcanization time than conventional acrylic rubbers using conventional vulcanizing agents. It is possible to obtain a vulcanizate with satisfactory mechanical strength and compression set, and it is possible to significantly shorten the vulcanization time.

The vulcanizate obtained from the composition of the present invention has excellent heat aging resistance, oil resistance, compression set, and weather resistance, and has excellent heat aging resistance, oil resistance, compression set, and weather resistance.
Various sealing materials such as rings, gaskets, oil seals, etc.
It can be widely and effectively used for various hoses, diaphragms, etc.

[Example] The present invention will be specifically explained below using examples.

In the following description, parts represent parts by weight, and % represents weight %.

Example 1 One-fifth of the mixture of the monomer mixture having the composition shown in Table 1 and n-dodecyl merbutane (varied to adjust the molecular weight) was mixed with 4 parts of sodium lauryl sulfate, 1 part of polyethylene glycol nonyl ether, Monosodium dihydrogen phosphate 0.3 parts, disodium monohydrogen phosphate 0.7 parts, water 2
It was mixed and stirred with an emulsifier solution consisting of a part of 0 to emulsify.

The temperature of this emulsified wave is 10℃, and 0.005% of ferrous sulfate is
parts, 0.02 parts of trisodium ethylenediaminetetraacetate,
Polymerization was started by adding 0.01 parts of tert-butyl hydroperoxide. Thereafter, the temperature was maintained at 10°C and the remaining monomers were added dropwise over about 5 hours, and at the same time the tert-
0.05 part of butyl hydroperoxide was added in portions. After the monomer had finished decreasing, the polymerization was continued for another 2 hours, and then hydroquinone was added to stop the polymerization. Monomer conversion was 96-99%. The obtained latex was poured into an aqueous sodium chloride solution at 80° C. to isolate the polymer, thoroughly washed with water, and then dried to obtain the desired acrylic rubber.

Comparative Example 1 An acrylic rubber (F ) Alternatively, an acrylic rubber (G-K) containing no cyanoalkyl ester of acrylic acid or methacrylic acid was obtained.

Examples 2 to 4 and Comparative Examples 2 to 4 Table 3 shows 100 parts of acrylic rubber, 1 part of stearic acid, MA
Fifty parts of F carbon black and a predetermined amount of the vulcanizing agent listed in Table 3 were kneaded using an 8-inch open roll to prepare a blend. The Mooney scorch time of the resulting formulation was measured according to JIS K300. The resulting compound was press-vulcanized at 170°C for 20 minutes, and further vulcanized in an oven at 150°C for 4 hours to obtain a vulcanized product. The physical properties of the obtained vulcanizate were determined according to JIS K-63.
Table 3 shows the results of the evaluation according to 01.

Examples 5 to 7 Crosstalk and vulcanization were carried out in the same manner as in Example 2, except that the vulcanizing agents shown in Table 4 were used. Table 4 shows the evaluation results of the Mooney scorch time of the blend and various physical properties of the vulcanizate.

Examples 8 to 11, Comparative Examples 5 to 7 Kneading and vulcanization were performed in the same manner as in Example 2, except that the acrylic rubber and vulcanizing agent shown in Table 5 were used.

Table 5 shows the evaluation results of the Mooney scorch time of the blend and various physical properties of the vulcanizate.

[Effects of the Invention] From the above results, it is clear that the production method and composition of the present invention provide an acrylic rubber vulcanizate with excellent vulcanization rate and compression set.

Claims (2)

[Claims] (1) 1) Cyanoalkyl acrylate represented by the formula ▲ Numerical formulas, chemical formulas, tables, etc.▼ (Here, R^1 is hydrogen or a methyl group, and R^2 is an alkyl group substituted with a cyano group.) Ester or methacrylic acid cyanoalkyl ester, 0.1 to 40% by weight, 2) Acrylic acid alkyl ester or acrylic acid alkoxyalkyl ester, 60 to 99.9% by weight, and 3) Monomer copolymerizable with these. body, 0-50
A process for producing vulcanizable acrylic rubber, characterized in that % by weight is polymerized in the presence of a radical initiator. (2) [1] 1) Acrylic acid represented by the formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (Here, R^1 is hydrogen or a methyl group, and R^2 is an alkyl group substituted with a cyano group.) Acid cyanoalkyl ester or methacrylic acid cyanoalkyl ester, 0.1-40% by weight, 2) Acrylic acid alkyl ester, 60-99.
9% by weight, and 3) monomers copolymerizable with these, 0
Acrylic rubber with a polymerization composition of ~50% by weight, 100
[2] Polyepoxy compound having at least two or more epoxy groups in the molecule, 0.1 to 10 parts by weight, [3] Quaternary ammonium salts or quaternary phosphonium salts, 0.1 -10 parts by weight of an acrylic rubber vulcanized composition.