Acrylic rubber composition

Abstract: An acrylic rubber composition comprising a halogen-containing acrylic rubber, a vulcanizing agent and at least one unsaturated compound selected from the group consisting of (1) α-olefins having at least 4 carbon atoms, (2)carboxylic acid vinyl esters, (3) alkyl vinyl ethers, (4) lower alkyl cyclohexenes or cyclohexenecarboxylic acid caprolactone esters and (5) unsaturated dicarboxylic acid diesters can give vulcanization products having an improved compression set without any substantial deterioration of normal state physical properties and resistance to heat ageing of the vulcanization products, where the unsaturated compound gives off no unpleaseant odor without any skin irritation when vulcanized and without lowering the mold releasability.

Description: BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION The present invention relates to an acrylic rubber composition, and more particularly to an acrylic rubber composition capable of giving vulcanization products having an improved compression set. 2. RELATED PRIOR ART Known typical vulcanizable, halogen-containing acrylic rubber systems are those based on polyamine or its carbamate. The resulting vulcanization products still have such disadvantages as a poor compression set and a poor resistance to heat ageing. To improve these disadvantages, it was proposed to copolymerize acrylic rubber with a cross-linking site monomer containing an active halogen such as vinyl chloroacetate, etc. (JP-B-39-20515). Such known active halogen-containing acrylic rubber vulcanizable systems contain a vulcanizer system of fatty acid alkali metal salt / sulfur or a vulcanizer system of trithiocyanuric acid / alkyldithiocarbamic acid metal salt. The former vulcanizer system can give vulcanization products having good normal state physical properties and a good resistance to heat ageing, but a poor compression set. Thus, the latter vulcanizer system capable of giving vulcanization products having a good compression set has been practically used up to now as a leading vulcanizer system for use in the vulcanization molding of O-rings, gaskets, etc. requiring a good compression set. However, the vulcanizer system of trithiocyanuric acid / alkyldithiocarbamic acid metal salt still has the following problems, one of which is generation of unpleasant odor from alkyldithiocarbamic acid metal salt during the vulcanization. Furthermore, in the rubber molding and processing fields, a shift from the now leading press molding to the injection molding is under way to increase the productivity, but this vulcanizer system has a problem of poor injection moldability. To improve the poor compression set of the vulcanizer system of fatty acid alkali metal salt / sulfur capable of giving vulcanization products having good normal state physical properties, a good resistance to heat ageing and having a good injection moldability without generation of unpleasant odor, on the other hand, it was proposed to incorporate an N-substituted bismaleimide into the vulcanizer system (JP-B-48-24019). The proposed vulcanizer system has an improved compression set indeed, but has too high a vulcanization rate and a cross-linking density, resulting in deterioration of breaking strength, breaking elongation, etc. It was also proposed to add an unsaturated monocarboxylic acid ester such as acrylic acid esters to the vulcanizer system of fatty acid alkali metal salt / sulfur (JP-A-3-31351). However, the acrylic acid esters have problems not only of generation of unpleasant odor and skin irritation during the kneading or vulcanization, but also of considerably retarded vulcanization and lowered modulus or breaking strength, and derioration of mold releasability due to the retarded vulcanization. Furthermore, it was proposed to add a thioether compound to the vulcanizer system (JP-A-4-142356). Generally, the resistance to heat ageing of acrylic rubber is connected to a brittling tendency and only available effective antioxidants for relieving the brittling tendency are specific amine-based antioxidants. Thus, even use of a thioether compound in place of the amine-based antioxidant inevitably gives vulcanization products having a poor resistance to heat ageing. SUMMARY OF THE INVENTION An object of the present invention is to provide a halogen-containing acrylic rubber composition capable of giving vulcanization products having an improved compression set without substantial deterioration of normal state physical properties and a resistance to heat ageing . Another object of the present invention is to provide a halogen-containing acrylic rubber composition without generation of unpleasant odor or skin irritation and without lowering of mold releasability during the vulcanization or molding. According to the present invention, there is provided an acrylic rubber composition as defined in claim 1. DETAILED DESCRIPTION OF THE INVENTION Halogen-containing acrylic rubber for use in the present invention includes, for example, copolymers of at least one main component selected from the group consisting of alkyl acrylate, alkoxyalkyl acrylate, alkylthioalkyl acrylate and cyanoalkyl acrylate, preferably in an amount of 60 to 99.8% by weight on the basis of total copolymer, copolymerized with 0.1 to 10% by weight, preferably 1 to 5% by weight, of at least one cross-linking site, halogen-containing monomer selected from (1) 2-chloroethyl vinyl ether, 2-chloroethyl acrylate and vinyl benzyl chloride, (2) vinyl chloroacetate and allyl chloroacetate, (3) addition reaction products of a glycidyl compound such as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, etc. with monochloroacetic acid and (4) alkenyl esters of α- or β-halogen-substituted aliphatic monocarboxylic acids; haloalkyl esters, haloalkyl alkenyl esters, haloalkyl alkenyl ketones and haloacetoxyalkyl esters of (meth)acrylic acid; and haloacetyl-containing unsaturated compounds. The copolymers can contain not more than 30% by weight of other ordinary vinyl compounds as copolymerized therein. Acrylic copolymers containing lactone-modified acrylate (JP-A-63-264612) or terminal cyanolactone-modified acrylate (JP-A-1-123809), as copolymerized therein, can be also used in the present invention. The halogen-containing acrylic rubber may be a copolymer of alkyl acrylate as a main component, or of alkyl acrylate and alkoxyalkyl acrylate as main components, copolymerized with a cross-linking site, halogen-containing monomer. Furthermore, halogen- and carboxyl-containing acrylic rubber, for example, the above-mentioned halogen-containing acrylic rubber further containing 0.1 to 10% by weight, preferably 1 to 5% by weight, of an unsaturated monocarboxylic acid such as acrylic acid, methacrylic acid or maleic acid or an unsaturated dicarboxylic acid monoester such as mono lower alkyl maleate, as copolymerized therein, can be used in the present invention as the halogen-containing acrylic rubber. These halogen-containing acrylic rubbers can be vulcanized preferably with the following vulcanizer systems: (a) Vulcanizer system of aliphatic acid alkali metal salt / sulfur: Aliphatic acid alkali metal salts include lithium salts, potassium salts or sodium salts of saturated fatty acids having 1 to 18 carbon atoms, unsaturated fatty acids having 3 to 18 carbon atoms, aliphatic dicarboxylic acids, aromatic dicarboxy acids, and more specifically include, for example, potassium stearate, sodium stearate, potassium oleate, sodium oleate, sodium 2-ethylhexanoate, sodium potassium tartrate, sodium propionate or sodium acetate. Particularly preferable are sodium or potassium salts of fatty acids having 8 to 18 carbon atoms. Potassium salts generally have a tendency to accelerate the vulcanization rate. (b) Vulcanizer system of trithiocyanuric acid / aliphatic acid alkali metal salt: The same aliphatic acid alkali metal salts as mentioned in the above item (a) can be used in this vulcanizer system. (c) Vulcanizer system of diamine or its carbamate / dibasic lead phosphite: Hexamethylenediamine or its carbamate is preferably used as the diamine or its carbamate.Besides, the following vulcanizer systems can be also used: (d) Vulcanizer system of trithiocyanuric acid / dicyandiamide / dibasic lead phosphite (e) Vulcanizer system of trithiocyanuric acid / dicyandiamide / metal oxide (f) Vulcanizer system of trithiocyanuric acid / dicyandiamide / aluminum-containing compound (g) Vulcanizer system of trithiocyanuric acid / dicyandiamide / aliphatic acid alkaline earth metal salt or zinc salt (h) Vulcanizer system of trithiocyanuric acid / metal dithiocarbamate / thiuram sulfide (i) Vulcanizer system of trithiocyanuric acid / metal dithiocarbamate / quaternary ammonium or phosphonium salt (j) Vulcanizer system of trithiocyanuric acid / trimethylthiourea / metal oxide (k) Vulcanizer system of trithiocyanuric acid / aliphatic acid alkaline earth metal salt or zinc salt Usually 0.1 to 10 parts by weight, preferably 0.2 to 1 parts by weight or about 1 to 5 parts by weight, depending on vulcanizer components and their combination, of one of these vulcanizer systems is used per 100 parts by weight of the halogen-containing acrylic rubber. The present acrylic rubber composition comprising the above-mentioned halogen-containing acrylic rubber and vulcanizing agent contains at least one unsaturated compound selected from the group consisting of the following compounds (1) to (5): (1) α-olefins having at least 4 carbon atoms: α-olefins having at least 4 carbon atoms, usually 4 to 30 carbon atoms and preferably 6 to 20 carbon atoms, where the α-olefins are in a liquid state, are used. Generally, α -olefins having such carbon atoms are oligomers obtainable as low-molecular weight polymers of ethylene monomer and are mixtures of oligomers having various degree of polymerization.In the present invention, α-olefins are used as such, or are used as α-olefins having a narrow distribution of carbon atoms on purification. α-olefins having less than 4 carbon atoms have too low a boiling point and are dissipated during the vulcanization. That is, the effect is reduced by half. On the other hand, α-olefins having a longer carbon chain are in a wax state and are hard to handle. Sometimes, α-olefins contain branched olefins, internal olefins or saturated hydrocarbons, but can be used as such without any trouble. 0.1 to 30 parts by weight of at least one of these α-olefins is used per 100 parts by weight of halogen-containing acrylic rubber. In case of application to vulcanization products requiring a low compression set such as O-rings and gaskets, 1 to 3 parts by weight of the α-olefins is used per 100 parts by weight of the halogen-containing acrylic rubber. In case of application to hose materials, even 10 to 30 parts by weight of the α-olefins can be used together with various plasticizers whereby the compression set can be effectively improved. The use of α-olefins have no such problems of unpleasant odor or skin irritation during the vulcanization as encountered in the case of acrylic acid ester and also have no mold releasability problem. (2) Carboxylic acid vinyl esters: Carboxylic acid vinyl esters for use in the present invention can be represented by the general formula RCOOCH=CH 2 , where R is an alkyl group having 1 to 20 carbon atoms, preferably 3 to 13 carbon atoms or an aryl group, and the alkyl group or aryl group may take a substituent group such as cyano group or alkoxy group Such carboxylic acid vinyl esters include, for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl myristate,vinyl palmitate, vinyl stearate, vinyl cyanoacetate and vinyl benzoate. 0.1 to 30 parts by weight of at least one of these carboxylic acid vinyl esters is used per 100 parts by weight of halogen-containing acrylic rubber. In case of application to vulcanization products requiring a low compression set such as O-rings and gaskets, 1 to 3 parts by weight of the carboxylic acid vinyl esters is used per 100 parts by weight of the halogen-containing acrylic rubber. In case of application to hose materials, even 10 to 30 parts by weight of the carboxylic acid vinyl esters can be used together with various plasticizers, whereby the compression set can be effectively improved. The use of carboxylic acid vinyl esters have no such problems of unpleasant odor or skin irritation during the vulcanization as encountered in the case of acrylic acid ester and also have no mold releasability problem. (3) Alkyl vinyl ethers: Alkyl vinyl ethers for use in the present invention are those represented by the general formula ROCH=CH 2 where R is an alkyl group having 3 to 18 carbon atoms, preferably 5 to 18 carbon atoms. Alkyl vinyl ethers having an alkyl group having less than 3 carbon atoms have too low a boiling point and are dissipated during the vulcanization. That is, the effect is reduced by half. The alkyl group may further have such a substituent as e.g. alkoxy group. The alkyl vinyl ether for use in the present invention includes, for example, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl ether, n-amyl vinyl ether, isoamyl vinyl ether, 2-ethylhexyl vinyl ether, n-octadecyl and vinyl ether. 0.1 to 30 parts by weight of at least one of these alkyl vinyl ethers is used per 100 parts by weight of halogen-containing acrylic rubber. In case of application to vulcanization products requiring a low compression set such as O-rings and gaskets, 1 to 3 parts by weight of the alkyl vinyl ethers is used per 100 parts by weight of the halogen-containing acrylic rubber. In case of application to hose materials, even 10 to 30 parts by weight of the alkyl vinyl ethers can be used together with various plasticizers, whereby the compression set can be effectively improved. The use of alkyl vinyl ethers have no such problems of unpleasant odor or skin irritation during the vulcanization as encountered in the case of acrylic acid esters and also have no mold releasability problem. (4) C 1-5 alkyl cyclohexenes or cyclohexenecarboxylic acid caprolactone esters: C 1-5 alkyl cyclohexenes for use in the present invention are cyclohexenes, at least one of whose hydrogen atoms at the 3-, 4-, 5- or 6- positions excluding the unsaturated bond is replaced with a C 1-5 alkyl group. The alkyl group may further have a C 1-5 alkoxy group as substituent, that is, it may be a C 1-5 alkoxy- C 1-5 alkyl group . The C 1-5 alkyl cyclohexenes include, for example, methylcyclohexene, dimethylcyclohexene, ethylcyclohexene, n-propylcyclohexene, isopropylcyclohexene, n-butylcyclohexene, isobutylcyclohexene and t-butylcyclohexene. Position of substitution for the C 1-5 alkyl group can be any one of 3- to 6- positions. Cyclohexenecarboxylic acid caprolactone esters for use in the present invention include cyclohexenes having a caprolactone ester group represented by the following general formula at the 3- position: -COO[(CH 2 ) 5 COO]nCH 2 R where R is an alkyl group having 1 to 8 carbon atoms, an alkoxyl group, an alkoxyalkyl group or a cyclohexenyl group and n is an integer of 1 to 5. 0.1 to 30 parts by weight of at least one of these C 1-5 alkylcyclohexenes or cyclohexenecarboxylic acid caprolactone esters is used per 100 parts by weight of halogen-containing acrylic rubber. In case of application to vulcanization products requiring a low compression set such as O-rings and gaskets, 1 to 3 parts by weight of the C 1-5 alkylcyclohexenes or cyclohexenecarboxylic acid caprolactone esters is used per 100 parts by weight of the halogen-containing acrylic rubber. In case of application to hose materials, even 10 to 30 parts by weight of the C 1-5 alkyl cyclohexenes or cyclohexenecarboxylic acid caprolactone esters can be used together with various plasticizers, whereby the compression set can be effectively improved. The use of C 1-5 alkyl cyclohexenes or cyclohexenecarboxylic acid caprolactone esters have no such problems of unpleasant odor or skin irritation during the vulcanization as encountered in the case of acrylic acid esters and also have no mold releasability problem. (5) Unsaturated dicarboxylic acid diesters: Unsaturated dicarboxylic acid diesters for use in the present invention are diesters of unsaturated dicarboxylic acids such as maleic acid, fumaric acid or itaconic acid, with two alkyl groups or two alkenyl groups, each having up to 10 carbon atoms, that is, such as dialkyls or dialkenyls as dimethyl, diethyl, dipropyl, diisopropyl, di-n-butyl, diisobutyl, di-t-butyl, di-2-ethylhexyl, diocty or diallyl. The diesters usually have the same ester groups, but can have mutually different ester groups. The alkyl groups may be alkoxy-substituted alkyl groups, such as methoxymethyl group, ethoxymethyl group, methoxyethyl group and ethoxyethyl group. 0.1 to 30 parts by weight of at least one of these unsaturated dicarboxylic acid diesters is used per 100 parts by weight of halogen-containing acrylic rubber. In case of application to vulcanization products requiring a low compression set such as O-rings and gaskets, 1 to 3 parts by weight of the unsaturated dicarboxylic acid diesters is used per 100 parts by weight of the halogen-containing acrylic rubber. In case of application to hose materials, even 10 to 30 parts by weight of the unsaturated dicarboxylic acid diesters can be used together with various plasticizers, whereby the compression set can be effectively improved. Unsaturated dicarboxylic acid diesters have higher molecular weights and boiling points than those of acrylic acid esters and thus have no such problems of unpleasant odor or skin irritation during the vulcanization as encountered in the case of acrylic acid esters and also have no mold releasability problem. The halogen-containing acrylic rubber composition comprising the above-mentioned essential components can further contain other necessary additives such as a filler, a reinforcing agent, a vulcanization acid or a lubricant when desired. For example, in case of application to vulcanization-molding materials for various sealing materials, the composition can contain carbon black for the O-ring and packing purposes, and can contain diatomaceous earth or white carbon for the oil seal purpose. The present composition can be prepared in a closed type kneader such as a kneader and a Bambury mixer or in an open-type kneader such as an open roll, and its vulcanization can be carried out usually by press vulcanization or injection molding vulcanization at a temperature of 150 to 250°C for 1 to 30 minutes, and if required, secondary vulcanization can be carried out by oven vulcanization or steam vulcanization at a temperature of 150 to 200°C for 1 to 22 hours. Compression set of vulcanization products can be improved without any substantial deterioration of normal state physical properties or resistance to heat ageing by adding at least one unsaturated compound selected from the group consisting of (1) α-olefins having at least 4 carbon atoms, (2) carboxylic acid vinyl esters, (3) C 3-18 alkyl vinyl ethers, (4) C 1-5 alkyl cyclohexenes or cyclohexenecarboxylic acid caprolactone esters and (5) unsaturated dicarboxylic acid diesters to a composition comprising a halogen-containing acrylic rubber and a vulcanizing agent the amount of unsaturated compound added being as defined in claim 1. These specific unsaturated compounds, as added, give off no unpleasant odor without any skin irritability during the vulcanization and without lowering the mold releasability. PREFERRED EMBODIMENTS OF THE INVENTION The present invention will be described in detail below, referring to Examples. EXAMPLE 1 TO 12 Acrylic rubber compositions were prepared from polymers A to D having monomer compositions (% by weight) given in the following Table 1, according to formulations given in the following Table 2 by kneading in an 8-inch open roll. Comonomer \ Polymer A B C D E Ethyl acrylate 98 48 95 48 Butyl acrylate 25 25 50 2-methoxyethyl acrylate 25 25 48 Vinyl chloroacetate 2 2 2 2-chloroethyl vinyl ether 5 Chloromethylstyrene 2 Ex.1 Ex.2 Ex.3 Ex.4 Ex.5 Ex.6 Polymer A 100 Polymer B 100 100 Polymer C 100 100 Polymer D 100 HAF carbon black (N330) 50 60 50 50 60 FEF carbon black (N550) 65 Stearic acid 1 1 1 1 1 1 4,4'-(α,α-dimethylbenzyl)-diphenylamine 2 2 2 2 2 2 Plasticizer (Fatty acid metal salt) 10 Sodium stearate 2.5 3 2.5 3 3 Potassium stearate 0.25 0.25 0.5 Sulfur 0.3 0.3 0.3 Tricyanuric acid 0.6 0.6 Dibasic lead phosphite 3 Hexamethylenediamine carbamate 0.75 Hexene 2 2 2 2 2 2 The thus obtained compositions were subjected to measurement of Mooney viscosity and scorch time according to JIS K-6300. Furthermore, the compositions were subjected to press vulcanization at 180°C for 8 minutes and then to oven vulcanization at 175°C for 4 hours, and the resulting vulcanization products were subjected to determination of normal state physical properties, resistance to heat ageing and compression set according to JIS K-6301. Test conditions for the resistance to heat ageing were 175°C for 70 hours and those for the compression set were 150°C for 70 hours. Results of determination are shown in the following Table 3. Ex.1 Ex.2 Ex.3 Ex.4 Ex.5 Ex.6 〈Properties of unvulcanized compositions〉 Mooney viscosity (ML 1+4 , M) 56 54 37 52 44 45 Scorch time (min. ) 19.9 10.8 8.9 25.0 17.3 12.4 〈Vulcanization product properties〉 Normal state physical properties Hardness (JIS-A, pts) 72 69 58 72 70 70 100% Modulus (kg/cm 2 ) 49 52 37 47 41 48 Breaking strength (kg/cm 2 ) 160 148 110 130 154 150 Breaking elongation (%) 320 270 280 240 330 260 Resistance to heat ageing Hardness change (%) +9 +9 +5 +10 +6 +6 Modulus change (%) -11 +8 -6 +15 +14 +13 Breaking strength change (%) -11 -5 -6 -6 0 -2 Breaking elongation change (%) -6 +1 -8 -5 -8 -8 Compression set (%) 22 21 32 32 20 21 〈Other influences of unsaturated compounds〉 Unpleasant odor none none none none none none Skin irritation none none none none none none Deterioration of mold releasability none none none none none none Acrylic rubber compositions were prepared from polymers E given in the foregoing Table 1, according to formulations given in the following Table 4 by kneading in an 8-inch open roll. Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Polymer E 100 100 100 100 100 100 HAF carbon black (N330) 60 60 60 60 60 FEF carbon black (N550) 60 Stearic acid 1 1 1 1 1 1 4,4'-( α ,α-dimethylbenzyl)diphenylamine 2 2 2 2 2 2 Sodium stearate 3 3 3 3 3 3 Potassium stearate 0.25 0.25 0.25 0.25 0.25 0.25 Sulfur 0. 3 0.3 0.3 0.3 0.3 0.3 Octadecene 2 Hexene 2 0.5 5 2 α-Olefin 2 Properties of the thus obtained unvulcanized compositions and properties, resistance to heat ageing and compression set of the resulting vulcanization products were determined in the same manner as in Examples 1 to 6. Results of determination are given in the following Table 5. Ex.7 Ex.8 Ex.9 Ex. 10 Ex. 11 Ex.12 〈Properties of unvulcanized compositions〉 Mooney viscosity(ML 1+4 , M) 51 49 48 53 40 46 Scorch time (min. ) 20.0 18.9 19.9 18.8 19.7 20.0 〈Vulcanization product properties〉 Normal state physical properties Hardness (JIS-A, pts) 67 62 66 68 66 63 100% Modulus (kg/cm 2 ) 60 55 61 68 52 63 Breaking strength (kg/cm 2 ) 144 144 144 145 145 129 Breaking elongation (%) 220 220 210 190 240 180 Resistance to heat ageing Hardness change (%) +10 +15 +12 +10 +12 +7 Modulus change (%) +1 +2 +7 -12 +8 -10 Breaking strength change (%) -7 -9 -5 -5 -7 -8 Breaking elongation change (%) -5 -5 0 +11 -12 +6 Compression set (%) 19 20 20 24 21 16 〈Other influences of unsaturated compounds〉 Unpleasant odor none none none none none none Skin irritation none none none none none none Deterioration of mold releasability none none none none none none EXAMPLES 13 TO 24 Acrylic rubber compositions were prepared from the same polymers A to D according to the same formulations as in Example 1 to 6, except that the same amount of vinyl acetate was used in place of hexene, by kneading in an 8-inch open roll.Properties of unvulcanized compositions and properties, resistance to heat ageing and compression set of the resulting vulcanization products were determined in the same manner as in Examples 1 to 6. Results of determination are given in the following Table 6. Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex. 18 〈Properties of unvulcanized compositions〉 Mooney viscosity (ML 1+4 , M) 54 57 38 52 43 44 Scorch time (min. ) 19.0 10.4 8.9 23.4 17.2 12.3 〈Vulcanization product properties〉 Normal state physical properties Hardness (JIS-A, pts) 70 71 56 72 71 70 100% Modulus (kg/cm 2 ) 48 53 38 44 41 50 Breaking strength (kg/cm 2 ) 159 148 111 129 152 153 Breaking elongation(%) 320 280 270 240 330 270 Resistance to heat ageing Hardness change (%) +9 +9 +5 +7 +5 +6 Modulus change (%) -12 +2 -12 +8 +8 +7 Breaking strength change (%) -10 -6 -6 -5 -4 +1 Breaking elongation change (%) -5 +3 -8 -5 -7 -8 Compression set (%) 24 25 34 36 25 22 〈Other influences of unsaturated compounds〉 Deterioration of mold releasability none none none none none none Acrylic rubber compositions were prepared from the same polymer E according to the same formulations as in Examples 7 to 12, except that the octadecene was replaced with the same amount of vinyl laurate, the hexene with the same amount of vinyl acetate and the α-olefin with the same amount of vinyl pivalate, by kneading in an 8-inch open roll. Properties of the thus obtained unvulcanized compositions and properties, resistance to heat ageing and compression set of the resulting vulcanization products were determined in the same manner as in Examples 1 to 6. Results of determination are shown in the following Table 7. Ex. 19 Ex. 20 Ex. 21 Ex. 22 Ex. 23 Ex. 24 〈Properties of unvulcanized compositions〉 Mooney viscosity (ML 1+4 , M) 50 50 49 54 42 45 Scorch time (min. ) 20.3 19.2 18.9 19.4 20.8 19.4 〈Vulcanization product properties〉 Normal state physical properties Hardness (JIS-A, pts) 67 64 66 68 65 65 100% Modulus (kg/cm 2 ) 57 56 62 66 52 61 Breaking strength (kg/cm 2 ) 144 143 144 147 145 130 Breaking elongation(%) 220 220 210 170 230 180 Resistance to heat ageing Hardness change (%) +7 +13 +10 +8 +10 +5 Modulus change (%) -4 -4 +3 -16 +4 -16 Breaking strength change (%) -7 -8 -6 -3 -7 -8 Breaking elongation change (%) -2 -4 -1 +12 -10 +8 Compression set (%) 22 22 23 26 23 21 〈Other influences of unsaturated compounds〉 Deterioration of mold releasability none none none none none none EXAMPLES 25 TO 36 Acrylic rubber compositions were prepared from the same polymers A to D according to the same formulations as in Example 1 to 6, except that the hexene was replaced with the same amount of n-amyl vinyl ether, by kneading in an 8-inch open roll. Properties of the thus obtained unvulcanized compositions and properties, resistance to heat ageing and compression set of the resulting vulcanization products were determined in the same manner as in Examples 1 to 6. Results of determination are shown in the following Table 8. Ex. 25 Ex. 26 Ex. 27 Ex. 28 Ex. 29 Ex. 30 〈Properties of unvulcanized compositions〉 Mooney viscosity (ML 1+4 , M) 55 56 36 51 44 45 Scorch time (min. ) 18.7 10.3 9.0 23.0 16.0 13.2 〈Vulcanization product properties〉 Normal state physical properties Hardness (JIS-A, pts) 71 70 57 73 71 70 100% Modulus (kg/cm 2 ) 48 52 36 45 42 49 Breaking strength (kg/cm 2 ) 160 148 109 129 153 152 Breaking elongation(%) 330 280 270 250 320 270 Resistance to heat ageing Hardness change (%) +8 +9 +4 +7 +5 +4 Modulus change (%) -13 +2 -12 +9 +8 +7 Breaking strength change (%) -10 -6 -6 -6 -4 +1 Breaking elongation change (%) -5 +3 -9 -5 -7 -8 Compression set (%) 24 24 35 35 24 23 〈Other influences of unsaturated compounds〉 Skin irritation none none none none none none Deterioration of mold releasability none none none none none none Acrylic rubber compositions were prepared from the same polymer E according to the same formulations as in Examples 7 to 12, except that the octadecene was replaced with the same amount of n-octadecyl vinyl ether, the hexene with the same amount of n-amyl vinyl ether and the α-olefin with the same amount of n-isoamyl vinyl ether, by kneading in an 8-inch open roll. Properties of the thus obtained unvulcanized compositions and properties, resistance to heat ageing and compression set of the resulting vulcanization products were determined in the same manner as in Examples 1 to 6. Results of determination are given in the following Table 9. Ex.31 Ex.32 Ex.33 Ex.34 Ex.35 Ex.36 〈Properties of unvulcanized compositions〉 Mooney viscosity (ML 1+4 , M) 51 49 49 53 41 47 Scorch time (min ) 19.9 19.0 18.9 18.1 19.7 20.4 〈Vulcanization product properties〉 Normal state physical properties Hardness (JIS-A, pts) 68 63 66 67 65 64 100% Modulus (kg/cm 2 ) 58 56 61 67 53 62 Breaking strength (kg/cm 2 ) 143 143 145 147 145 132 Breaking elongation(%) 230 220 210 190 230 170 Resistance to heat ageing Hardness change (%) +8 +13 +10 +8 +11 +6 Modulus change (%) -5 -4 +3 -16 +3 -16 Breaking strength change (%) -7 -8 -5 -4 -7 -7 Breaking elongation change (%) -2 -5 0 +11 -10 +8 Compression set (%) 22 23 22 27 24 20 〈Other influences of unsaturated compounds〉 Skin irritation none none none none none none Deterioration of mold releasability none none none none none none EXAMPLES 37 TO 48 Acrylic rubber compositions were prepared from the same polymers A to D according to the same formulations as in Examples 1 to 6, except that the hexene was replaced with the same amount of 3,6-dimethylcyclohexene, by kneading in an 8inch open roll. Properties of the thus obtained unvulcanized compositions and properties, resistance to heat ageing and compression set of the resulting vulcanization products were determined in the same manner as in Examples 1 to 6. Results of determination are given in the following Table 10. Ex. 37 Ex. 38 Ex. 39 Ex. 40 Ex. 41 Ex. 42 〈Properties of unvulcanized compositions〉 Mooney viscosity (ML 1+4 , M) 57 56 40 53 46 46 Scorch time (min.) 19.9 9.8 8.7 23.7 18.2 12.2 〈Vulcanization product properties〉 Normal state physical properties Hardness (JIS-A, pts) 72 70 60 71 70 72 100% Modulus (kg/cm 2 ) 51 53 39 48 42 50 Breaking strength (kg/cm 2 ) 161 146 108 132 153 150 Breaking elongation(%) 330 270 290 230 330 250 Resistance to heat ageing Hardness change (%) +9 +10 +5 +9 +6 +7 Modulus change (%) -10 +8 -6 +15 +13 +14 Breaking strength change (%) -11 -5 -4 -4 0 -3 Breaking elongation change (%) -6 +1 -8 -4 -9 -8 Compression set (%) 28 28 36 37 36 27 〈Other influences of unsaturated compounds〉 Unpleasant odor none none none none none none Skin irritation none none none none none none Deterioration of mold releasability none none none none none none Acrylic rubber compositions were prepared from the same polymer E according to the same formulations as in Examples 7 to 12, except that the octadecene was replaced with the same amount of 3-methylcyclohexene, the hexene with the same amount of 3,6-dimethylcyclohexene and the α-olefin with the same amount of caprolactone-modified cyclohexene (CLM3, trademark of a product made by Daicel Kagaku K. K., Japan), by kneading in an 8-inch open roll. Properties of the thus prepared compositions and properties, resistance to heat ageing and compression set of the resulting vulcanization products were determined in the same manner as in Examples 1 to 6. Results of determination are given in the following Table 11. Ex. 43 Ex. 44 Ex. 45 Ex. 46 Ex. 47 Ex. 48 〈Properties of unvulcanized compositions〉 Mooney viscosity (ML 1+4 , M) 52 50 50 55 43 48 Scorch time (min.) 21.3 18.3 19.8 19.4 20.0 19.9 〈Vulcanization product properties〉 Normal state physical properties Hardness (JIS-A, pts) 68 63 66 69 68 63 100% Modulus (kg/cm 2 ) 62 55 61 68 53 63 Breaking strength (kg/cm 2 ) 145 144 144 146 145 129 Breaking elongation(%) 220 210 210 190 230 180 Resistance to heat ageing Hardness change (%) +9 +14 +12 +10 +11 +7 Modulus change (%) +2 +3 +5 -12 +9 -11 Breaking strength change (%) -8 -9 -4 -6 -7 -9 Breaking elongation change (%) -4 -3 +1 +12 -11 +6 Compression set (%) 25 26 26 29 27 20 〈Other influences of unsaturated compounds〉 Unpleasant odor none none none none none none Skin irritation none none none none none none Deterioration of mold releasability none none none none none none EXAMPLES 49 TO 60 Acrylic rubber compositions were prepared from the same polymers A to D according to the same formulations as in Example 1 to 6, except that the hexene was replaced with the same amount of dibutyl fumarate (DEs-2, trademark of a product made by Kurogane Kasei K. K., Japan), by kneading in an 8-inch open roll. Properties of the thus obtained unvulcanized compositions and properties, resistance to heat ageing and compression set of the resulting vulcanization products were determined in the same manner as in Examples 1 to 6. Results of determination are given in the following Table 12. Ex. 49 Ex. 50 Ex. 51 Ex. 52 Ex. 53 Ex. 54 〈Properties of unvulcanized compositions〉 Mooney viscosity (ML 1+4 , M) 51 48 32 45 38 40 Scorch time (min.) 19.9 11.2 9.4 24.1 17.8 12.2 〈Vulcanization product properties〉 Normal state physical properties Hardness (JIS-A, pts) 68 66 53 68 65 66 100% Modulus (kg/cm 2 ) 45 57 39 44 47 44 Breaking strength (kg/cm 2 ) 158 148 109 132 152 150 Breaking elongation(%) 340 280 300 250 330 270 Resistance to heat ageing Hardness change (%) +11 +12 +8 +13 +8 +9 Modulus change (%) 0 +16 +4 +21 +22 +21 Breaking strength change (%) -20 -15 -16 -17 -8 -12 Breaking elongation change (%) -9 -2 -11 -9 -10 -12 Compression set (%) 22 22 33 32 21 22 〈Other influences of unsaturated compounds〉 Unpleasant odor none none none none none none Acrylic rubber compositions were prepared from the same polymer E according to the same formulations as in Examples 7 to 12, except that the octadecene was replaced with the same amount of dibutyl maleate (DEs-1, trademark of a product made by Kurogane Kasei K. K., Japan), the hexene with the same amount of dibutyl fumarate (DEs-2) and the α-olefin with the same amount of dibutyl itaconate (DEs-3, trademark of a product made by Kurogane Kasei K. K., Japan), by kneading in an 8-inch open roll. Properties of the thus obtained unvulcanized compositions and properties, resistance to heat ageing and compression set of the resulting vulcanization products were determined in the same manner as in Examples 1 to 6. Results of determination are shown in the following Table 13. Ex. 55 Ex. 56 Ex. 57 Ex. 58 Ex. 59 Ex. 60 〈Properties of unvulcanized compositions〉 Mooney viscosity (ML 1+4 , M) 45 44 46 48 35 40 Scorch time (min.) 19.5 19.9 20.1 18.3 20.3 19.9 〈Vulcanization product properties〉 Normal state physical properties Hardness (JIS-A, pts) 63 62 62 64 62 58 100% Modulus (kg/cm 2 ) 55 56 54 63 48 58 Breaking strength (kg/cm 2 ) 144 145 144 144 145 130 Breaking elongation(%) 240 240 250 220 250 210 Resistance to heat ageing Hardness change (%) +13 +13 +12 +13 +15 +10 Modulus change (%) +10 +9 +10 -4 +16 -2 Breaking strength change (%) -13 -12 -13 -14 -16 -16 Breaking elongation change (%) -8 -5 -6 +7 -14 +1 Compression set (%) 20 20 21 24 20 16 〈Other influences of unsaturated compounds〉 Unpleasant odor none none none none none none COMPARATIVE EXAMPLES 1 TO 3 Acrylic rubber compositions were prepared from the polymer C or D, according to the following formulations given in the following Table 14 by kneading in an 8-inch open roll. Comp. Ex.1 Comp. Ex.2 Comp. Ex.3 Polymer C 100 100 Polymer D 100 HAF carbon black (N330) 50 50 60 Stearic acid 1 1 1 4,4'-(α,α-dimethylbenzyl)-diphenylamine 2 2 2 Sodium stearate 3 3 Trithiocyanuric acid 0.6 0.6 Dibasic lead phosphite 3 Hexamethylenediamine carbamate * 3 0.75 Properties of the thus obtained unvulcanized compositions and properties, resistance to heat ageing and compression set of the resulting vulcanization products were determined in the same manner as in Examples 1 to 6. Results of determination are given in the following Table 15. Comp. Ex.1 Comp. Ex.2 Comp. Ex.3 〈Properties of unvulcanized compositions〉 Mooney viscosity (ML 1+4 , M) 57 49 49 Scorch time (min.) 23.0 16.0 11.9 〈Vulcanization product properties〉 Normal state physical properties Hardness (JIS-A, pts) 75 70 69 100% Modulus (kg/cm 2 ) 52 46 52 Breaking strength (kg/cm 2 ) 125 155 150 Breaking elongation (%) 220 310 250 Resistance to heat ageing Hardness change (%) +7 +3 +7 Breaking strength change (%) -4 -2 -2 Breaking elongation change(%) +1 -4 -6 Compression set (%) 40 28 25 COMPARATIVE EXAMPLES 4 TO 9 Acrylic rubber compositions were prepared from the polymer E, according to formulations given in the following Table 16 by kneading in an 8-inch open roll. Comparative Examples 4 5 6 7 8 9 Polymer E 100 100 100 100 100 100 HAF carbon black (N330) 60 60 60 60 60 FEF carbon black (N550) 65 Stearic acid 1 1 1 1 1 1 4,4'-(α,α-dimethylbenzyl)-diphenylamine 2 2 2 2 2 2 Plasticizer (fatty acid metal salt) 10 Sodium stearate 3 3 3 3 2.5 Potassium stearate 0.25 0.25 0.25 0.25 0.5 Sulfur 0.3 0.3 0.3 0.3 0.3 Trithiocyanuric acid 0.5 Zinc di-n-butylthiocarbamate 1.5 Dodecyl acrylate 2 Tetradecadiene 2 Dodecane 2 Properties of the thus obtained unvulcanized compositions and properties, resistance to heat ageing and compression set of the resulting vulcanization products were determined in the same manner as in Examples 1 to 6. Results of determination are given in the following Table 17. Comparative Examples 4 5 6 7 8 9 〈Properties of unvulcanized compositions〉 Mooney viscosity (ML 1+4 , M) 56 41 49 54 38 48 Scorch time (min.) 17.4 19.6 15.0 18.1 8.6 8.3 〈Vulcanization product properties〉 Normal state physical properties Hardness (JIS-A, pts) 67 59 66 66 58 65 100% Modulus (kg/cm 2 ) 65 40 58 60 39 70 Breaking strength (kg/cm 2 ) 144 139 143 144 109 123 Breaking elongation (%) 180 250 220 200 272 170 Resistance to heat ageing Hardness change (%) +8 +13 +12 +8 +5 +12 Modulus change (%) -5 +17 +6 -4 -8 +14 Breaking strength change (%) -8 -15 -2 -7 -8 0 Breaking elongation change (%) +6 -8 -5 +2 -10 +6 Compression set (%) 35 21 23 39 45 16 〈Other influences of unsaturated compounds〉 Unpleasant odor observed none none Skin irritation observed none none Deterioration of mold releasability observed none none As injection moldability judging from mold dirt by attachment of tailings, the following results are obtained: Examples Attachment of tailings Example 1 ○ '' 4 ▵ '' 5 ○ '' 7 ○ '' 13 ○ '' 16 ▵ '' 17 ○ '' 19 ○ '' 25 ○ '' 28 ▵ '' 29 ○ '' 31 ○ '' 37 ○ '' 40 ▵ '' 41 ○ '' 43 ○ '' 49 ○ '' 52 ▵ '' 53 ○ '' 55 ○ Comp. Ex. 9 ×

Claims: An acrylic rubber composition, which comprises a halogen-containing acrylic rubber, a vulcanizing agent and at least one unsaturated compound selected' from the group consisting of (1) α-olefins having at least 4 carbon atoms, (2) carboxylic acid vinyl esters, (3) C 3-18 alkyl vinyl ethers, (4) C 1-5 alkyl cyclohexenes wherein the alkyl group may be substituted with a C 1-5 alkoxy group or cyclohexenecarboxylic acid caprolactone esters and (5) unsaturated dicarboxylic acid diesters, wherein 0.1 to 30 parts by weight of the unsaturated compound is contained per 100 parts by weight of the halogen-containing acrylic rubber. An acrylic rubber composition according to Claim 1, wherein the halogen-containing acrylic rubber is a copolymer of at least one monomer selected from the group consisting of alkyl acrylate, alkoxyalkyl acrylate, alkylthioalkyl acrylate and cyanoalkyl acrylate, as a main component, copolymerized with 0.1 to 10% by weight of a cross-linking site, halogen-containing monomer, based on the copolymer. An acrylic rubber composition according to Claim 2, wherein the halogen-containing acrylic rubber is a copolymer of the alkyl acrylate as a main component, copolymerized with the cross-linking site, halogen-containing monomer. An acrylic rubber composition according to Claim 2, wherein the halogen-containing acrylic rubber is a copolymer of the alkyl acrylate and the alkoxyalkyl acrylate as main components, copolymerized with the cross-linking site, halogen-containing monomer. An acrylic rubber composition according to Claim 1, wherein the halogen-containing acrylic rubber is a halogen- and carboxyl group-containing acrylic rubber. An acrylic rubber composition according to Claim 1, wherein the α-olefin is a low molecular weight polymer of ethylene monomer. An acrylic rubber composition according to Claim 1, wherein the carboxylic acid vinyl esters are unsaturated compounds represented by the general formula RCOOCH=CH 2 , where R is an alkyl group having 1 to 20 carbon atoms or an aryl group. An acrylic rubber composition according to Claim 1, wherein the C 3-18 alkyl vinyl ethers are unsaturated compounds represented by the general formula ROCH=CH 2 , where R is an alkyl group having 3 to 18 carbon atoms. An acrylic rubber composition according to Claim 1, wherein the C 1-5 alkyl cyclohexenes are cyclohexene derivatives, at least one of whose hydrogen atoms at 3-, 4-, 5-or 6-positions excluding the unsaturated bond is replaced with a C 1-5 alkyl group. An acrylic rubber composition according to Claim 9, wherein the at least one C 1-5 alkyl group is substituted with a C 1-5 alkoxy group. An acrylic rubber composition according to Claim 1, wherein the cyclohexenecarboxylic acid caprolactone esters are cyclohexene derivatives having a caprolactone ester group represented by the general formula -COO[(CH 2 ) 5 COO]nCH 2 R at the 3-position, where R is an alkyl group having 1 to 8 carbon atoms, an alkoxyl group, an alkoxyalkyl group or a cyclohexenyl group and n is an integer of 1 to 5. An acrylic rubber composition according to Claim 1, wherein the unsaturated dicarboxylic acid diesters are esters having two alkyl groups or two alkenyl groups, each group having up to 10 carbon atoms. An acrylic rubber composition according to Claim 1, wherein a plasticizer is further contained.

Inventors: OKABE JUN, YOSHIDA TAMOTSU, OKABE, JUN, YOSHIDA, TAMOTSU
Applicants: NIPPON MEKTRON KK, NIPPON MEKTRON, LTD.
Application year: 1996
Main classification: C08L33
IPC codes: C08F265