JP4024219B2 - Carboxyl group-containing acrylic rubber composition - Google Patents

Description

  The present invention relates to an acrylic rubber composition having good vulcanization characteristics and excellent balance between processability and compression set.

  JP-A-50-45031 discloses an acrylate ester-butenedionic acid monoester binary copolymer or an ethylene-acrylate ester-butenedionic acid monoester terpolymer, hexamethylenediamine and hexamethylenediamine carbamate, An elastomer composition containing 4,4′-methylenedianiline or the like as a vulcanizing agent and a vulcanization accelerator is described. Japanese Patent Application Laid-Open No. 11-140264 discloses an acrylic elastomer composition containing a diamine compound, a guanidine compound and / or a benzolylsulfenamide compound as a vulcanization accelerator. It is described that the permanent set characteristics are excellent. Japanese Patent Application Laid-Open No. 11-269336 discloses an acrylic elastomer composition in which mercaptobenzimidazoles, guanidines and a diamine compound are blended, and describes that compression set is excellent. However, an elastomer composition containing a diamine compound such as hexamethylene diamine or hexamethylene diamine carbamate as a vulcanizing agent has a good compression set, but has a short scorch time and poor processing safety, and is a sufficient hose, packing, and gasket. It was not practical as a molding material. In addition, when 4,4'-methylenedianiline, 4,4'-diaminodiphenyl ether and di-o-tolylguanidine are used as vulcanizing agents, the roll processability is very poor, but the roll work is very poor. There was a problem that it could not be done.

  Japanese Patent Application Laid-Open No. 2002-317091 describes a composition in which an aliphatic monoamine is blended with an acrylic elastomer. This composition is added when an aliphatic monoamine is added in an amount exceeding 0.8 parts by mass. There was a problem that the sulfur reaction was not sufficiently performed and the compression set deteriorated.

JP 50-45031 A JP-A-11-140264 Japanese Patent Laid-Open No. 11-269336 JP 2002-317091 A

  The present invention provides an acrylic rubber composition that solves the above-described problems, has good vulcanization characteristics, and has an excellent balance between workability and compression set.

As a result of intensive studies to solve the above problems, the present inventors have (A) carboxyl group-containing acrylic elastomer, (B) primary amine acetate, (C) guanidine compound, and (D) diamine. It has been found that by combining with a compound, an acrylic rubber composition excellent in processability and compression set can be obtained, and the present invention has been completed.
That is, the present invention provides an acrylic rubber composition obtained by blending (A) a carboxyl group-containing acrylic rubber with (B) a primary amine acetate, (C) a guanidine compound and (D) a diamine compound, and vulcanization thereof. It is about things.

  The vulcanizate comprising the acrylic rubber and the composition thereof of the present invention has excellent rubber properties and is excellent in balance between processing safety and compression set.

The present invention is described in detail below.
The carboxyl group-containing acrylic rubber of the present invention is an unsaturated carboxylic acid such as acrylic acid or methacrylic acid, or an aliphatic unsaturated dicarboxylic acid such as maleic acid, fumaric acid, itaconic acid or citraconic acid. Or monomethylmalate, monoethylmalate, mono-n-propylmalate, monoisopropylmalate, mono-n-butylmalate, monoisobutylmalate, monomethylfumarate, monoethylfumarate, mono-n-propylfumarate , Monoisopropylmalate, mono-n-butyl fumarate, monomethyl itaconate, monoethyl itaconate, mono-n-propyl itaconate, mono-n-propyl citraconate, mono-n-butyl citraconate, mono Aliphatic unsaturated dithiols such as isobutylcitraconate An acrylic rubber characterized in that one or two or more monomers selected from the group of carboxylic acid monoesters are copolymerized at a ratio of about 1 to 12% by mass in the polymer.

As the carboxyl group-containing monomer, maleic acid monoalkyl ester represented by the following structural formula (3) and / or maleic acid monoalkoxyalkyl ester represented by the following structural formula (4) are preferable. Moreover, as a copolymerization amount, it is preferable that 1-12 mass% of carboxyl group-containing monomers are contained per all monomers.

Structural formula (3)
-HC-CH-
/ \
HOOC COOR2
(Wherein R2 is an alkyl group having 1 to 4 carbon atoms)

Structural formula (4)
-HC-CH-
/ \
HOOC COOR3OR4
(Wherein R3 is an alkylene group having 1 to 4 carbon atoms, and R4 is an alkyl group having 1 to 4 carbon atoms)

The carboxyl group-containing acrylic rubber of the present invention is obtained by copolymerizing the carboxyl group-containing monomer and an unsaturated monomer such as an alkyl acrylate ester.
Examples of the acrylic acid alkyl ester include methyl acrylate, ethyl acrylate, n-propyl acrylate, isobutyl acrylate, n-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-octyl acrylate, and 2-ethylhexyl acrylate. In particular, ethyl acrylate and n-butyl acrylate are preferable.

  Further, other copolymerizable acrylic acid alkyl esters include n-decyl acrylate, n-dodecyl acrylate, n-octadecyl acrylate, cyanomethyl acrylate, 1-cyanoethyl acrylate, 2-cyanoethyl acrylate, 1-cyanopropyl acrylate, 2- Examples include cyanopropyl acrylate, 3-cyanopropyl acrylate, 4-cyanobutyl acrylate, 6-cyanohexyl acrylate, 2-ethyl-6-cyanohexyl acrylate, and 8-cyanooctyl acrylate.

  Also, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2- (n-propoxy) ethyl acrylate, 2- (n-butoxy) ethyl acrylate, 3-methoxypropyl acrylate, 3-ethoxypropyl acrylate, 2- (n Examples thereof include alkoxyalkyl esters of acrylic acid such as -propoxy) propyl acrylate and 2- (n-butoxy) propyl acrylate.

  Further, 1,1-dihydroperfluoroethyl (meth) acrylate, 1,1-dihydroperfluoropropyl (meth) acrylate, 1,1,5-trihydroperfluorohexyl (meth) acrylate, 1,1,2,2-tetrahydro Fluorine-containing acrylics such as perfluoropropyl (meth) acrylate, 1,1,7-trihydroperfluoroheptyl (meth) acrylate, 1,1-dihydroperfluorooctyl (meth) acrylate, 1,1-dihydroperfluorodecyl (meth) acrylate Hydroxyl group-containing acrylic acid ester such as acid ester, 1-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, Tertiary amino group-containing acrylic acid esters such as butylaminoethyl (meth) acrylate, methacrylates such as methyl methacrylate, octyl methacrylate.

  As copolymerizable monomers, alkyl vinyl ketones such as methyl vinyl ketone, vinyl and allyl ethers such as vinyl ethyl ether and allyl methyl ether, vinyls such as styrene, α-methyl styrene, chlorostyrene, vinyl toluene and vinyl naphthalene. Aromatic compounds, vinyl nitriles such as acrylonitrile and methacrylonitrile, acrylamide, vinyl acetate, ethylene, propylene, butadiene, isoprene, pentadiene, vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, vinyl propionate, alkyl fumarate And ethylenically unsaturated compounds.

As an unsaturated monomer such as an alkyl acrylate ester, an alkyl acrylate ester represented by the following structural formula (2) is preferable. The copolymerization amount is preferably 98.9 to 83% by mass of an alkyl acrylate unit.
Structural formula (2)
-CH2-CH-
｜
COOR1
(Wherein R1 is an alkyl group having 1 to 8 carbon atoms)

  The acrylic rubber of the present invention can be obtained by copolymerizing the above monomers by a known method such as emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization and the like.

  For the (A) carboxyl group-containing acrylic rubber of the present invention, a vulcanization system combining (B) primary amine acetate, (C) guanidine compound and (D) diamine compound is used.

  Primary amine acetates include methylamine acetate, ethylamine acetate, propylamine acetate, butylamine acetate, pentylamine acetate, hexylamine acetate, heptylamine acetate, octylamine acetate, nonylamine acetate, Examples include decylamine acetate, undecylamine acetate, dodecylamine acetate, tetradecylamine acetate, hexadodecylamine acetate, stearylamine acetate, octadecylamine acetate, eicosylamine acetate, methanolamine acetic acid, etc. .

  The addition amount of the primary amine acetate is preferably 0.01 to 4 parts by mass, more preferably 0.05 to 2 parts by mass with respect to 100 parts by mass of the acrylic rubber. If it is less than 0.01 parts by mass, roll workability is remarkably deteriorated. On the other hand, if it exceeds 4 parts by mass, vulcanization is slowed and sufficient vulcanizate properties are not exhibited.

  Examples of the guanidine compound include guanidine, tetramethylguanidine, dibutylguanidine, diphenylguanidine, di-o-tolylguanidine, and di-o-tolylguanidine is preferably used.

  The addition amount of the guanidine compound is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the acrylic rubber. When the amount is less than 0.1 parts by mass, the vulcanization reaction is not sufficiently performed, and when the amount exceeds 10 parts by mass, overvulcanization occurs, and in this case, compression set at a high temperature is deteriorated.

As the diamine compound, a special diamine compound represented by the structural formula (1) is preferable, and at least one of these compounds is used.
Structural formula (1): H2N-Ph-M-Ph-NH2
However, M is 1 type in O, S, SO2, CONH or O-RO.
However, R of O-R-O is Ph, Ph-Ph, Ph-SO2-Ph, (CH2) m, where m = 3-5, Ph-C (CX3) 2-Ph ... X = H or F , (CH2) C (CH3) 2 (CH2). Ph represents a benzene ring.

  As the compound of the structural formula (1), 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-diaminodiphenyl sulfide, 1,3-bis (4-aminophenoxy) -2,2-dimethyl Propane, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) pentane, 2,2′-bis [4- (4-Aminophenoxy) phenyl] propane, 4,4′-diaminodiphenylsulfone, bis (4-3-aminophenoxy) phenylsulfone), 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoro Propane, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 4,4′-diaminobenzanilide, bi [4- (3-aminophenoxy) phenyl] sulfone, and the like.

  0.01-10 mass parts is preferable with respect to 100 mass parts of acrylic rubber, and, as for the addition amount of diamine, 0.05-5 mass parts is still more preferable. If it is 0.05 parts or less, the vulcanizability is insufficient, and if it exceeds 10 parts by weight, the processing stability is deteriorated.

  The acrylic rubber composition of the present invention can be molded and vulcanized by adding a filler, a plasticizer, an anti-aging agent, a stabilizer, a lubricant, a reinforcing agent, etc., depending on the purpose when put to practical use. .

Two or more kinds of fillers and reinforcing agents such as carbon black, anhydrous silicic acid, and surface-treated calcium carbonate can be used in combination of required rubber properties.
The total amount of these additives is preferably 30 to 100 parts by mass with respect to 100 parts by mass of the acrylic rubber.

  As the plasticizer, a plasticizer usually used for rubber can be added. Examples thereof include ester plasticizers and ether plasticizers such as polyoxyethylene ether, but are not limited to the above, and various plasticizers can be used. As addition amount of a plasticizer, it can add to about 50 mass parts with respect to 100 mass parts of acrylic rubber.

  Examples of the anti-aging agent include amine-based, imidazole-based, carbamic acid metal salt, phenol-based, wax, and the like, and about 0.5 to 10 parts by mass can be added to 100 parts by mass of acrylic rubber.

  The rubber component in the acrylic rubber composition used in the present invention is mainly composed of acrylic rubber. In addition to the acrylic rubber, natural rubber, synthetic rubber, for example, IIR, BR, NBR, HNBR, CR, EPDM, FKM, Q, CSM, CO, ECO, CM and the like can be contained.

In addition, as a machine for kneading, molding, and vulcanizing the acrylic rubber, acrylic rubber composition and vulcanized product of the present invention, those usually used in the rubber industry can be used.
Vulcanization can be made into a product only by primary vulcanization by press vulcanization or steam vulcanization. Furthermore, by performing secondary vulcanization with hot air or the like, characteristics such as compression set can be further improved.

The acrylic rubber, acrylic rubber composition and vulcanized product thereof according to the present invention are particularly used as seal parts such as rubber hoses, gaskets and packings and vibration-proof members. Specific examples of rubber hoses include transmission oil cooler hoses, engine oil cooler hoses, turbo intercooler hoses, turbo air duct hoses, power steering hoses, hot air hoses, radiator hoses, and other industrial machinery and construction machinery high pressure systems. Used for hoses used in oil systems, fuel systems hoses, drain hoses and the like.
Specific seal parts include engine head cover gaskets, oil pan gaskets, oil seals, lip seal packings, O-rings, transmission seal gaskets, crankshaft and camshaft seal gaskets, valve stems, and power steering seal belts. Cover seals, CVJ, R & P boot materials and the like.
In addition, examples of the vibration-proof rubber parts include a damper pulley, a center support cushion, a suspension bush, and the like.
In particular, the acrylic rubber, the acrylic rubber composition and the vulcanized product thereof according to the present invention are excellent in cold resistance, oil resistance and heat resistance in addition to excellent mechanical properties. It is very suitably used as a rubber hose and gasket for automobiles in which is severe.

As the structure of the rubber hose, a single hose obtained from the acrylic rubber composition of the present invention, or, depending on the use of the rubber hose, a synthetic rubber other than the acrylic rubber of the present invention in the layer made of the acrylic rubber of the present invention, for example, Also, it can be applied to a composite hose in which fluorine-based rubber, fluorine-modified acrylic rubber, hydrin rubber, CSM, CR, NBR, HNBR, ethylene / propylene rubber or the like is combined as an inner layer, an intermediate layer, or an outer layer.
Further, depending on the characteristics required for the rubber hose, it is possible to provide a reinforcing thread or a wire in the middle of the hose or in the outermost layer of the rubber hose as is generally done.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not particularly limited by these examples.

Acrylic rubber 1
In a pressure resistant reaction vessel with an internal volume of 40 liters, a mixture of 7.8 kg of ethyl acrylate, 3.4 kg of n-butyl acrylate and 0.6 kg of monobutyl maleate, 17 kg of an aqueous solution of 4% by weight of partially saponified polyvinyl alcohol, 22 g of sodium acetate Then, the mixture was thoroughly mixed with a stirrer to prepare a uniform suspension. After replacing the air in the upper part of the tank with nitrogen, ethylene was injected into the upper part of the tank and the pressure was adjusted to 20 kg / cm 2. Stirring was continued and the inside of the tank was maintained at 55 ° C., and then an aqueous t-butyl hydroperoxide solution was injected separately from the inlet to initiate polymerization.
During the reaction, the temperature in the tank was kept at 55 ° C., and the reaction was terminated after 6 hours. A sodium borate aqueous solution was added to the produced polymerization solution to solidify the polymer, followed by dehydration and drying to obtain a raw rubber. This polymer was designated as acrylic rubber 1.

Acrylic rubber 2
In a pressure-resistant reaction vessel with an internal volume of 40 liters, a mixture of 7.8 kg of ethyl acrylate, 3.4 kg of n-butyl acrylate and 0.5 kg of monobutyl maleate, 17 kg of an aqueous solution of 4% by weight of partially saponified polyvinyl alcohol, 22 g of sodium acetate Then, the mixture was thoroughly mixed with a stirrer to prepare a uniform suspension. After replacing the air in the upper part of the tank with nitrogen, the inside of the tank was maintained at 55 ° C., and then an aqueous t-butyl hydroperoxide solution was injected from the inlet separately to initiate polymerization.
During the reaction, the temperature in the tank was kept at 55 ° C., and the reaction was terminated in 6 hours. A sodium borate aqueous solution was added to the produced polymerization solution to solidify the polymer, followed by dehydration and drying to obtain a raw rubber. This polymer was designated as acrylic rubber 2.

Example and Comparative Example The acrylic rubber composition obtained by blending using an 8-inch roll was evaluated according to the blending formulation shown in Table 1.
The workability was judged from the roll workability when the acrylic rubber composition was wound around a roll. A case where the roll was not very sticky and was very good was marked as ◎, a case where the roll was not sticky and good, ◯, a case where the roll was slightly sticky, and a case where the roll was extremely sticky.
Subsequently, the physical property test result was done about the vulcanizate, and the result was shown in Table 1. A primary vulcanization test sheet is prepared by vulcanization at 170 ° C. for 10 minutes in an electric heating press, and this vulcanized product is heat-treated at 170 ° C. for 4 hours in a gear oven to obtain a secondary vulcanized product. A test piece was prepared.
Mechanical properties such as tensile strength and elongation were measured in accordance with JIS K6251 using secondary vulcanized specimens.
The hardness was measured using a durometer hardness meter according to JIS K6253.
The compression set test was performed in accordance with JIS K6262 (test conditions are 150 ° C. × 70 hours).

  In the Mooney scorch test, a scorch time (t5) at a test temperature of 125 ° C. was measured using an L-shaped rotor in accordance with JIS K6300.

Claims (9)

(A) 100 parts by mass of a carboxyl group-containing acrylic rubber;
(B) 0.01-4 parts by mass of primary amine acetate,
(C) 0.1 to 10 parts by mass of a guanidine compound ;
(D) An acrylic rubber composition comprising 0.01 to 10 parts by mass of a diamine compound. The acrylic rubber composition according to claim 1 , wherein the diamine compound (D) comprises at least one of the special diamine compounds represented by the following structural formula (1).
Formula _{(1): H 2 N-} Ph-M-Ph-NH 2
However, M is one of O, S, SO ₂ , CONH or O—R—O.
However O-R-O for _{R, Ph, Ph-Ph, Ph} -SO 2 -Ph, (CH 2) m ...... where _{m = 3~5, Ph-C (} CX 3) 2 -Ph ... X = One of H or F, (CH ₂ ) C (CH ₃ ) ₂ (CH ₂ ). Ph represents a benzene ring. The compound of structural formula (1) is 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-diaminodiphenyl sulfide, 1,3-bis (4-aminophenoxy) -2,2-dimethylpropane, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) pentane, 2,2-bis [4- (4- Aminophenoxy) phenyl] propane, 4,4′-diaminodiphenylsulfone, bis (4-3-aminophenoxy) phenylsulfone), 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 3 , 4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 4,4′-diaminobenzanilide, bis [4- (3-amino Phenoxy) phenyl] consists of one or more of the group of sulfonic claim 2 acrylic rubber composition. The acrylic rubber composition according to any one of claims 1 to 3, wherein the primary amine acetate is an aliphatic primary monoamine acetate. The carboxyl group-containing acrylic rubber (A) is less than 0.1 to 5% by mass of ethylene monomer units, 98.9 to 83% by mass of acrylic acid alkyl ester units represented by the following structural formula (2), The maleic acid monoalkyl ester represented by the following structural formula (3) and / or the maleic acid monoalkoxyalkyl ester unit represented by the following structural formula (4) is composed of 1 to 12% by mass. Item 5. The acrylic rubber composition according to any one of Items 1 to 4.
Structural formula (2)
—CH ₂ —CH—
｜
COOR1
(Wherein R1 is an alkyl group having 1 to 8 carbon atoms)

Structural formula (3)
-HC-CH-
/ \
HOOC COOR2
(Wherein R2 is an alkyl group having 1 to 4 carbon atoms)

Structural formula (4)
-HC-CH-
/ \
HOOC COOR3OR4
(Wherein R3 is an alkylene group having 1 to 4 carbon atoms, and R4 is an alkyl group having 1 to 4 carbon atoms) A vulcanized product obtained by vulcanizing the acrylic rubber composition according to any one of claims 1 to 5. A rubber hose comprising the vulcanized product according to claim 6. A seal part comprising the vulcanized product according to claim 6. Anti-vibration rubber parts comprising the vulcanizate according to claim 6.