JP2004269873A - Carboxyl group-containing acrylic rubber composition - Google Patents

Abstract

An acrylic rubber composition having good vulcanization characteristics and an excellent balance between processability and compression set is provided.
[Solution]
(A) Acrylic rubber containing a carboxyl group (B) Primary amine acetate (C) By combining with a guanidine compound and (D) a diamine compound, an acrylic rubber composition excellent in processability and compression set was found. Was.

Description

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

  JP-A-50-45031 discloses hexamethylene diamine and hexamethylene diamine carbamate in an acrylate-butenedionic acid monoester binary copolymer or an ethylene-acrylate-butenedionic acid monoester terpolymer. An elastomer composition containing 4,4'-methylenedianiline or the like as a vulcanizing agent and a vulcanization accelerator is described. JP-A-11-140264 describes an acrylic elastomer composition containing a diamine compound, a guanidine compound and / or a benzolylsulfenamide compound as a vulcanization accelerator, and provides scorch stability and compression. It is described that the permanent set characteristics are excellent. JP-A-11-269336 describes an acrylic elastomer composition containing a mercaptobenzimidazole compound, a guanidine compound and a diamine compound, and describes that the composition has excellent compression set. However, an elastomer composition containing a diamine compound such as hexamethylene diamine or hexamethylene diamine carbamate as a vulcanizing agent has good compression set, but has a short scorch time, is inferior in processing safety, and has a sufficient hose, packing and gasket. However, it was not practical as a molding material. When 4,4'-methylenedianiline or 4,4'-diaminodiphenyl ether and di-o-tolylguanidine are used as a vulcanizing agent, the scorch time is long but the roll processability is extremely poor. There was a problem that I could not do it.

  JP-A-2002-317091 discloses a composition in which an aliphatic monoamine is blended with an acrylic elastomer. However, when this composition is added in excess of 0.8 parts by mass of an aliphatic monoamine, it is added. There was a problem that the sulfuric acid reaction was not sufficiently performed and compression set was deteriorated.

JP-A-50-45031 JP-A-11-140264 JP-A-11-269336 JP 2002-317091 A

  The present invention solves the above-mentioned problems, and provides an acrylic rubber composition having good vulcanization properties and an excellent balance between processability and compression set.

The present inventors have conducted intensive studies to solve the above problems, and as a result, (A) a carboxyl group-containing acrylic elastomer, (B) a primary amine acetate, (C) a guanidine compound, and (D) a diamine It has been found that an acrylic rubber composition having excellent processability and compression set can be provided by combining the compound with the compound, and the present invention has been completed.
That is, the present invention provides an acrylic rubber composition comprising (A) a carboxyl group-containing acrylic rubber, (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 also has an excellent balance between processing safety and compression set.

Hereinafter, the present invention will be described in detail.
The carboxyl group-containing acrylic rubber of the present invention includes, as carboxyl group-containing unsaturated fatty acids, acrylic acid, unsaturated carboxylic acids such as methacrylic acid, maleic acid, fumaric acid, itaconic acid, and aliphatic unsaturated dicarboxylic acids such as citraconic acid. Or monomethyl malate, monoethyl malate, mono-n-propyl malate, monoisopropyl malate, mono-n-butyl malate, monoisobutyl malate, monomethyl fumarate, monoethyl fumarate, mono-n-propyl fumarate Monoisopropyl maleate, mono-n-butyl fumarate, monomethyl itaconate, monoethyl itaconate, mono-n-propyl itaconate, mono-n-propyl citrate, mono-n-butyl citrate, mono Aliphatic unsaturated diamines such as isobutyl citraconate 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, a monoalkyl maleate represented by the following structural formula (3) and / or a monoalkoxyalkyl maleate represented by the following structural formula (4) are preferable. The copolymerization amount is preferably such that the carboxyl group-containing monomer is contained in an amount of 1 to 12% by mass based on all the monomers.

Structural formula (3)
-HC-CH-
/ ＼
HOOC COOR2
(R2 in the formula 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 above carboxyl group-containing monomer with an unsaturated monomer such as an alkyl acrylate.
Examples of the alkyl acrylate 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. Particularly, ethyl acrylate and n-butyl acrylate are preferable.

  Further 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 And alkoxyalkyl acrylates such as -propoxy) propyl acrylate and 2- (n-butoxy) propyl acrylate.

  Furthermore, 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 Acid esters, 1-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, hydroxy-containing acrylates such as 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.

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

As the unsaturated monomer such as an alkyl acrylate, an alkyl acrylate represented by the following structural formula (2) is preferable. The copolymerization amount is preferably from 98.9 to 83% by mass of alkyl acrylate units.
Structural formula (2)
-CH2-CH-
|
COOR1
(R1 in the formula 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, or bulk polymerization.

  For the (A) carboxyl group-containing acrylic rubber of the present invention, a vulcanization system combining (B) a primary amine acetate, (C) a guanidine compound and (D) a 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, Decylamine acetate, undecylamine acetate, dodecylamine acetate, tetradecylamine acetate, hexadodecylamine acetate, stearylamine acetate, octadecylamine acetate, eicosylamine acetate, methanolamine acetic acid, and the like. .

  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, per 100 parts by mass of the acrylic rubber. If the amount is less than 0.01 part by mass, the roll processability is remarkably poor, while if it exceeds 4 parts by mass, vulcanization is slowed and sufficient vulcanizate properties are not exhibited.

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

  The amount of the guanidine compound added is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the acrylic rubber. When the amount is less than 0.1 part by mass, the vulcanization reaction is not sufficiently performed, and when the amount exceeds 10 parts by mass, overvulcanization occurs, and in this case also, the 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
Here, M is one of O, S, SO2, CONH and O-R-O.
Here, R of O—R—O is Ph, Ph—Ph, Ph—SO 2 —Ph, (CH 2) m... Where m = 3 to 5, Ph—C (CX 3) 2 -Ph... X = H or F , (CH2) C (CH3) 2 (CH2). Ph represents a benzene ring.

  Compounds of structural formula (1) include 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, [4- (3-aminophenoxy) phenyl] sulfone, and the like.

  The addition amount of the diamine is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, based on 100 parts by mass of the acrylic rubber. If the amount is less than 0.05 part, the vulcanizability is insufficient, and if it exceeds 10 parts by mass, the processing stability deteriorates.

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

Fillers and reinforcing agents such as carbon black, silicic anhydride, and surface-treated calcium carbonate can be used as a mixture of two or more types in view of required rubber properties.
The total amount of these additives is preferably 30 to 100 parts by mass based on 100 parts by mass of the acrylic rubber.

  As the plasticizer, a plasticizer usually used for rubber can be added. For example, ester plasticizers, ether plasticizers such as polyoxyethylene ether and the like can be mentioned, but not limited to the above, and various plasticizers can be used. The plasticizer can be added up to about 50 parts by mass based on 100 parts by mass of the acrylic rubber.

  Examples of the anti-aging agent include amine-based, imidazole-based, metal carbamate, phenol-based, and wax, and can be added in an amount of about 0.5 to 10 parts by mass based on 100 parts by mass of the acrylic rubber.

  The rubber component in the acrylic rubber composition used in the present invention has an acrylic rubber as a main component. In addition to the acrylic rubber, if necessary, natural rubber, synthetic rubber such as IIR, BR, It can contain NBR, HNBR, CR, EPDM, FKM, Q, CSM, CO, ECO, CM and the like.

As the machine for kneading, molding and vulcanizing the acrylic rubber, the acrylic rubber composition and the vulcanizate thereof of the present invention, those usually used in the rubber industry can be used.
The vulcanization can be completed only by primary vulcanization such as press vulcanization or steam vulcanization. Further, by performing secondary vulcanization with hot air or the like, properties such as compression set can be further improved.

The acrylic rubber, the acrylic rubber composition and the vulcanizate thereof of the present invention are used particularly as sealing parts such as rubber hoses, gaskets, packings and vibration damping members. In addition, 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 high-pressure systems for industrial machinery and construction machinery. It is used for hoses used for oil-based, fuel-based hoses, drain-based hoses, and the like.
Specific examples of the sealing parts include an engine head cover gasket, an oil pan gasket, an oil seal, a lip seal packing, an O-ring, a transmission seal gasket, a crankshaft and a camshaft seal gasket, a valve stem, a power steering seal belt. Cover seals, CVJ and R & P boot materials.
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 of the present invention, the acrylic rubber composition and the vulcanized product thereof have excellent mechanical properties, and also excellent cold resistance, oil resistance and heat resistance. Are very suitable for use as rubber hoses and gaskets for automobiles, which are severe.

As the configuration 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 layer made of the acrylic rubber of the present invention, a synthetic rubber other than the acrylic rubber of the present invention, for example, It can also be applied to a composite hose in which fluorinated rubber, fluorine-modified acrylic rubber, hydrin rubber, CSM, CR, NBR, HNBR, ethylene / propylene rubber, etc. are combined as an inner layer, an intermediate layer, or an outer layer.
Further, depending on the characteristics required of the rubber hose, it is also possible to provide a reinforcing thread or wire in the middle of the hose or on the outermost layer of the rubber hose, as is generally done.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not particularly limited by these Examples.

Acrylic rubber 1
In a pressure-resistant reaction vessel having an inner volume of 40 liters, a mixed solution 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 partially saponified polyvinyl alcohol, and 22 g of sodium acetate , And mixed well 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. After continuing stirring and maintaining the inside of the vessel at 55 ° C., an aqueous solution of t-butyl hydroperoxide was separately injected from the injection port to start polymerization.
During the reaction, the temperature in the vessel was maintained at 55 ° C., and the reaction was terminated after 6 hours. An aqueous sodium borate solution was added to the resulting polymerization solution to solidify the polymer, and the polymer was dehydrated and dried to obtain a raw rubber. This polymer was designated as acrylic rubber 1.

Acrylic rubber 2
In a pressure-resistant reaction vessel having an inner volume of 40 liters, a mixed solution 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, and 22 g of sodium acetate , And mixed well with a stirrer to prepare a uniform suspension. After the air in the upper part of the tank was replaced with nitrogen, the inside of the tank was maintained at 55 ° C., and then an aqueous solution of t-butyl hydroperoxide was separately injected from an injection port to start polymerization.
During the reaction, the temperature in the vessel was kept at 55 ° C., and the reaction was completed in 6 hours. An aqueous sodium borate solution was added to the resulting polymerization solution to solidify the polymer, and the polymer was dehydrated and dried to obtain a raw rubber. This polymer was designated as acrylic rubber 2.

Examples and Comparative Examples An acrylic rubber composition obtained by compounding using an 8-inch roll was evaluated according to the compounding recipe shown in Table 1.
The processability was determined from the roll workability when the acrylic rubber composition was wound around a roll. ◎: Very good without roll stickiness, ○: Good without roll stickiness, Δ: Slight roll stickiness, X: Bad roll stickiness.
Next, the vulcanized product was subjected to physical property test results, and the results are shown in Table 1. It is vulcanized at 170 ° C. for 10 minutes by an electric heating press to produce a primary vulcanized test sheet, and this vulcanized product is further heat-treated at 170 ° C. for 4 hours in a gear oven to obtain a secondary vulcanized product. Test pieces were prepared.
Using a test piece of the secondary vulcanized product, mechanical properties such as tensile strength and elongation were measured in accordance with JIS K6251.
The hardness was measured using a durometer according to JIS K6253.
The compression set test was performed in accordance with JIS K6262 (test conditions: 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) a carboxyl group-containing acrylic rubber,
(B) a primary amine acetate;
An acrylic rubber composition comprising (C) a guanidine compound and (D) a diamine compound. An acrylic rubber composition wherein the diamine compound (D) comprises at least one or more special diamine compounds represented by the following structural formula (1).
Structural formula (1): H2N-Ph-M-Ph-NH2
Here, M is one of O, S, SO2, CONH and O-R-O.
Here, R of O—R—O is Ph, Ph—Ph, Ph—SO 2 —Ph, (CH 2) m... Where m = 3 to 5, Ph—C (CX 3) 2 -Ph... X = H or F , (CH2) C (CH3) 2 (CH2). Ph represents a benzene ring.   When the compound of the structural formula (1) is 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-diaminodiphenylsulfide, 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, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 4,4'-diaminobenzanilide, bis [4- (3 Aminophenoxy) phenyl] claim 1 acrylic rubber composition according comprising one or more of the group of sulfone.   The acrylic rubber composition according to any one of claims 1 to 3, wherein the primary amine acetate is an aliphatic primary monoamine acetate. (A) a carboxyl group-containing acrylic rubber having an ethylene monomer unit of 0.1 to less than 5% by mass and an acrylic acid alkyl ester unit of 98.9 to 83% by mass represented by the following structural formula (2); It is characterized by comprising 1 to 12% by mass of a monoalkyl maleate ester represented by the following structural formula (3) and / or a monoalkoxyalkyl maleate unit represented by the following structural formula (4). Item 5. The acrylic rubber composition according to any one of Items 1 to 4.
Structural formula (2)
-CH2-CH-
|
COOR1
(R1 in the formula is an alkyl group having 1 to 8 carbon atoms)

Structural formula (3)
-HC-CH-
/ ＼
HOOC COOR2
(R2 in the formula 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 vulcanizate obtained by vulcanizing the acrylic rubber composition according to claim 1.   A rubber hose comprising the vulcanized product according to claim 6.   A seal component comprising the vulcanized product according to claim 6. An anti-vibration rubber part comprising the vulcanized product according to claim 6.