JP2013018936A - Crosslinking rubber composition, and crosslinked rubber product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crosslinking rubber composition capable of providing a crosslinked rubber product excellent in bleeding resistance, and excellent in fluidity when being used for injection molding.SOLUTION: The crosslinking rubber composition contains (i) 100 pts.wt of a carboxyl group-containing highly saturated nitrile rubber (A), (ii) 2 to 20 pts.wt of at least one compound (D) having a hydroxide group, selected from a 10-20C fatty acid (B) and a 10-20C alcohol (C), and (iii) 0.1 to 10 pts.wt of a polyamine crosslinking agent (E).

Description

  The present invention relates to a crosslinkable rubber composition that can provide a rubber cross-linked product excellent in bleed resistance and excellent in fluidity when used in injection molding.

  Conventionally, nitrile rubber (NBR) has been used as a material for automotive rubber parts such as hoses and tubes, taking advantage of oil resistance, mechanical properties, chemical resistance, etc. Also, nitrile rubber (NBR) Hydrogenated nitrile rubber (highly saturated nitrile rubber) obtained by hydrogenating a carbon-carbon double bond in a polymer chain is further excellent in heat resistance, and is therefore used in rubber parts such as hoses and seals.

  In such a hydrogenated nitrile rubber, in order to improve compression set resistance, Patent Document 1 discloses crosslinkability in which a carboxyl group-containing hydrogenated nitrile rubber, a polyvalent amine crosslinking agent and a basic crosslinking accelerator are added. A rubber composition is disclosed. However, since the crosslinkable rubber composition described in Patent Document 1 has a high Mooney viscosity, there is a problem in that the fluidity in a high shear region is not sufficient when molding by injection molding. When an amine compound such as stearylamine is added to improve the viscosity, the fluidity is improved, but there is a problem that the resulting crosslinked rubber has insufficient bleed resistance and compression set resistance.

JP 2001-55471 A

  The present invention relates to a crosslinkable rubber composition capable of providing a rubber cross-linked product having excellent fluidity and excellent bleeding resistance when used in injection molding, and a rubber cross-linked product obtained by cross-linking the cross-linkable rubber composition The purpose is to provide.

  As a result of intensive studies to achieve the above object, the present inventors have used a crosslinkable rubber composition containing a specific amount of a carboxyl group-containing highly saturated nitrile rubber, a specific compound having a hydroxyl group, and a polyamine crosslinking agent. Thus, the inventors have found that the above object can be achieved and have completed the present invention.

Thus, according to the present invention, (i) 100 parts by weight of a carboxyl group-containing highly saturated nitrile rubber (A), (ii) a fatty acid (B) having 10 to 20 carbon atoms and an alcohol (C) having 10 to 20 carbon atoms A crosslinkable rubber comprising 2 to 20 parts by weight of a compound (D) having at least one hydroxyl group selected from the group consisting of: and (iii) 0.1 to 10 parts by weight of a polyamine crosslinking agent (E). A composition is provided.
In addition, it is preferable that the said compound (D) which has a hydroxyl group is a C10-20 alcohol (C), and it is more preferable that it is a C10-20 saturated alcohol.

  Further, the carboxyl group-containing highly saturated nitrile rubber (A) used in the present invention comprises 5 to 60% by weight of α, β-ethylenically unsaturated nitrile monomer unit and 39.5 to 80% by weight of conjugated diene monomer unit. And a carboxyl group-containing monomer unit in an amount of 0.5 to 15% by weight, and the carboxyl group-containing monomer unit is an α, β-ethylenically unsaturated dicarboxylic acid monoalkyl ester. A monomer unit is more preferable.

  And it is preferable that said crosslinkable rubber composition is a crosslinkable rubber composition for injection molding.

  Moreover, according to this invention, the rubber crosslinked material formed by bridge | crosslinking the said crosslinkable rubber composition is provided.

  According to the present invention, a crosslinkable rubber composition capable of providing a rubber cross-linked product having excellent fluidity and excellent bleed resistance when used in injection molding, and a rubber cross-linked product obtained by cross-linking the cross-linkable rubber composition Is provided.

  The crosslinkable rubber composition of the present invention comprises (i) 100 parts by weight of a carboxyl group-containing highly saturated nitrile rubber (A), (ii) a fatty acid (B) having 10 to 20 carbon atoms and an alcohol having 10 to 20 carbon atoms ( It comprises 2 to 20 parts by weight of a compound (D) having at least one hydroxyl group selected from the group consisting of C), and (iii) 0.1 to 10 parts by weight of a polyamine crosslinking agent (E).

Carboxyl group-containing highly saturated nitrile rubber (A)
The carboxyl group-containing highly saturated nitrile rubber (A) used in the present invention is co-polymerized with the α, β-ethylenically unsaturated nitrile monomer, the carboxyl group-containing monomer, and each of the monomers added as necessary. A rubber having an iodine value of 120 or less, obtained by copolymerizing polymerizable monomers.

The α, β-ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an α, β-ethylenically unsaturated compound having a nitrile group. For example, acrylonitrile; α-chloroacrylonitrile, α-bromoacrylonitrile, etc. [Alpha] -halogenoacrylonitrile; [alpha] -alkylacrylonitrile such as methacrylonitrile. Among these, acrylonitrile and methacrylonitrile are preferable.
The α, β-ethylenically unsaturated nitrile monomer may be used alone or in combination of two or more.

  The content of the α, β-ethylenically unsaturated nitrile monomer unit is preferably 5 to 60% by weight, more preferably 10 to 10%, based on all monomer units constituting the highly saturated nitrile rubber (A). It is 55% by weight, more preferably 15 to 50% by weight. If the content of the α, β-ethylenically unsaturated nitrile monomer unit is too small, the oil resistance of the resulting rubber cross-linked product may be reduced, and conversely if too much, cold resistance may be reduced. is there.

  The carboxyl group-containing monomer is a monomer that can be copolymerized with an α, β-ethylenically unsaturated nitrile monomer and has at least one unsubstituted (free) carboxyl group that is not esterified. There is no particular limitation as long as it is a monomer. Examples of such carboxy group-containing monomers include α, β-ethylenically unsaturated monocarboxylic acid monomers, α, β-ethylenically unsaturated polyvalent carboxylic acid monomers, and α, β- And ethylenically unsaturated dicarboxylic acid monoester monomers. The carboxyl group-containing monomer also includes monomers in which the carboxyl group of these monomers forms a carboxylate. Furthermore, an anhydride of α, β-ethylenically unsaturated polyvalent carboxylic acid can also be used as a carboxyl group-containing monomer because it forms a carboxyl group by cleaving the acid anhydride group after copolymerization.

  Examples of the α, β-ethylenically unsaturated monocarboxylic acid monomer include acrylic acid, methacrylic acid, ethyl acrylic acid, crotonic acid, and cinnamic acid.

  Examples of the α, β-unsaturated polyvalent carboxylic acid monomer include butenedionic acid such as fumaric acid and maleic acid, itaconic acid, and citraconic acid. Examples of the anhydride of α, β-unsaturated polyvalent carboxylic acid include maleic anhydride and itaconic anhydride.

  As α, β-ethylenically unsaturated dicarboxylic acid monoester monomer, monomethyl maleate, monoethyl maleate, monopropyl maleate, mono n-butyl maleate, monomethyl fumarate, monoethyl fumarate, monopropyl fumarate , Mono n-butyl fumarate, monomethyl itaconate, monoethyl itaconate, monopropyl itaconate, mono n-butyl itaconate, monomethyl citraconic acid, monoethyl citraconic acid, monopropyl citraconic acid, mono n-butyl citraconic acid, etc. , Β-ethylenically unsaturated dicarboxylic acid monoalkyl ester monomer; monocyclopentyl maleate, monocyclohexyl maleate, monocycloheptyl maleate, monocyclopentyl fumarate, monocyclohexyl fumarate, monocylic fumarate Α, β-ethylenically unsaturated dicarboxylic acid monocycloalkyl esters such as loheptyl, monocyclopentyl itaconic acid, monocyclohexyl itaconic acid, monocycloheptyl itaconate, monocyclopentyl citraconic acid, monocyclohexyl citraconic acid, monocycloheptyl citraconic acid, etc. Α, such as monomethylcyclopentyl maleate, monoethylcyclohexyl maleate, monomethylcyclopentyl fumarate, monoethylcyclohexyl fumarate, monomethylcyclopentyl itaconate, monoethylcyclohexyl itaconate, monomethylcyclopentyl citraconic acid, monoethylcyclohexyl citraconic acid, β-ethylenically unsaturated dicarboxylic acid monoalkyl cycloalkyl ester monomer; mono-2-hydroxy maleate Ethyl, mono 3-hydroxypropyl maleate, mono 2-hydroxyethyl fumarate, mono 2-hydroxypropyl fumarate, mono 2-hydroxyethyl itaconate, mono 3-hydroxypropyl itaconate, mono 2-hydroxyethyl citraconic acid, etc. [Alpha], [beta] -ethylenically unsaturated dicarboxylic acid monohydroxyalkyl ester monomers; [alpha], [beta] -ethylenically unsaturated dicarboxylic acid monoesters having an alicyclic structure such as monocyclohexenyl maleate and monocyclohexenyl fumarate Monomer; and the like.

A carboxyl group-containing monomer may be used alone or in combination of two or more.
Among these, α, β-ethylenically unsaturated dicarboxylic acid monoester monomer is preferable because the effect of the present invention becomes more remarkable, and α, β-ethylenically unsaturated dicarboxylic acid monoalkyl ester monomer Is more preferable, maleic acid monoalkyl ester is more preferable, and mono n-butyl maleate is particularly preferable. In addition, as for carbon number of the alkyl group of the said alkylester, 2-8 are preferable.

  The content of the carboxyl group-containing monomer unit is preferably 0.5 to 15% by weight, more preferably 1 to 12% by weight, and still more preferably 2 to 10% by weight, based on all monomer units. . If the content of the carboxyl group-containing monomer unit is too small, the mechanical strength and compression set resistance of the resulting rubber cross-linked product may be reduced. Conversely, if the content is too large, the cross-linkable rubber composition There is a possibility that the stability of the scorch is deteriorated or the fatigue resistance of the obtained rubber cross-linked product is lowered.

  In the carboxyl group-containing highly saturated nitrile rubber (A) used in the present invention, the α, β-ethylenically unsaturated nitrile monomer and the carboxyl group-containing monomer together with the resulting crosslinked product exhibit rubber elasticity. More preferred is a copolymer of a conjugated diene monomer.

  The conjugated diene monomer is not particularly limited as long as it is copolymerizable with an α, β-ethylenically unsaturated nitrile monomer and a carboxyl group-containing monomer, but 1,3-butadiene, isoprene, C4-C6 conjugated diene monomers such as 2,3-dimethyl-1,3-butadiene and 1,3-pentadiene are preferred, 1,3-butadiene and isoprene are more preferred, and 1,3-butadiene is preferred. Particularly preferred. The conjugated diene monomer may be used alone or in combination of two or more.

  The content of the conjugated diene monomer unit is preferably 39.5 to 80% by weight, more preferably 44 to 78% by weight, and still more preferably 48 to 75% by weight, based on all monomer units. If the content of the conjugated diene monomer unit is too small, the rubber elasticity of the resulting rubber cross-linked product may be lowered. Conversely, if the content is too large, the heat resistance and chemical stability may be impaired. .

  The carboxyl group-containing highly saturated nitrile rubber (A) used in the present invention is copolymerized with an α, β-ethylenically unsaturated nitrile monomer, a carboxyl group-containing monomer, and a conjugated diene monomer. It may be a copolymer of other possible monomers. Such other monomers include ethylene, α-olefin monomers, aromatic vinyl monomers, α, β-ethylenically unsaturated carboxylic acid ester monomers (corresponding to carboxyl group-containing monomers) And a fluorine-containing vinyl monomer, a copolymerizable anti-aging agent, and the like.

  The α-olefin monomer preferably has 2 to 12 carbon atoms, and examples thereof include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene and 1-octene.

  Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, vinyl pyridine and the like.

  Examples of the α, β-ethylenically unsaturated carboxylic acid ester monomer (excluding those corresponding to carboxyl group-containing monomers) include, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, and n-acrylate. -(Meth) acrylic acid ester having an alkyl group having 1 to 18 carbon atoms such as dodecyl, methyl methacrylate and ethyl methacrylate (abbreviation of "methacrylic acid ester and acrylic acid ester"; the same shall apply hereinafter); methoxymethyl acrylate (Meth) acrylic acid ester having a C2-C12 alkoxyalkyl group such as methoxyethyl methacrylate; C2-C12 cyanoalkyl such as α-cyanoethyl acrylate, α-cyanoethyl methacrylate, cyanobutyl methacrylate, etc. (Meth) acrylic acid ester having a group; acrylic acid -(Meth) acrylic acid ester having a C1-C12 hydroxyalkyl group such as hydroxyethyl, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate; trifluoroethyl acrylate, tetrafluoropropyl methacrylate, etc. (Meth) acrylic acid ester having a fluoroalkyl group having 1 to 12 carbon atoms; α, β-ethylenically unsaturated dicarboxylic acid dialkyl ester such as dimethyl maleate, dimethyl fumarate, dimethyl itaconate, diethyl itaconate; dimethylamino And amino group-containing α, β-ethylenically unsaturated carboxylic acid esters such as methyl acrylate and diethylaminoethyl acrylate.

  Examples of the fluorine-containing vinyl monomer include fluoroethyl vinyl ether, fluoropropyl vinyl ether, o-trifluoromethyl styrene, vinyl pentafluorobenzoate, difluoroethylene, and tetrafluoroethylene.

  Examples of copolymerizable anti-aging agents include N- (4-anilinophenyl) acrylamide, N- (4-anilinophenyl) methacrylamide, N- (4-anilinophenyl) cinnamamide, N- (4- Anilinophenyl) crotonamide, N-phenyl-4- (3-vinylbenzyloxy) aniline, N-phenyl-4- (4-vinylbenzyloxy) aniline and the like.

These other copolymerizable monomers may be used alone or in combination of two or more.
The content of other monomer units is preferably 50% by weight or less, more preferably 30% by weight or less, and still more preferably 10% by weight or less based on the total monomer units.

  The iodine value of the carboxyl group-containing highly saturated nitrile rubber (A) is 120 or less, preferably 80 or less, more preferably 25 or less, and particularly preferably 15 or less. If the iodine value of the carboxyl group-containing highly saturated nitrile rubber (A) is too high, the heat resistance and ozone resistance of the resulting rubber cross-linked product may be lowered.

The polymer Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the carboxyl group-containing highly saturated nitrile rubber (A) is preferably 15 to 200, more preferably 20 to 150, and particularly preferably 30 to 120. If the polymer Mooney viscosity of the carboxyl group-containing highly saturated nitrile rubber (A) is too low, the mechanical strength of the resulting rubber cross-linked product may be reduced. Conversely, if it is too high, the fluidity of the cross-linkable rubber composition may be reduced. May be reduced.

The carboxyl group content in the carboxyl group-containing highly saturated nitrile rubber (A), that is, the number of moles of carboxyl groups per 100 g of the carboxyl group-containing highly saturated nitrile rubber (A) is preferably 5 × 10 ^{−4 to} 5. × 10 ⁻¹ ephr, more preferably 1 × 10 ⁻³ to 1 × 10 ⁻¹ ephr, and even more preferably 5 × 10 ^{−3 to} 6 × 10 ⁻² ephr. If the carboxyl group content of the carboxyl group-containing highly saturated nitrile rubber (A) is too small, the mechanical strength and compression set resistance of the resulting crosslinked rubber product may be lowered. There is a possibility that the stability of the scorch deteriorates and the fatigue resistance of the resulting rubber cross-linked product decreases.

  The method for producing the carboxyl group-containing highly saturated nitrile rubber (A) used in the present invention is not particularly limited, but a copolymer rubber latex is prepared by copolymerizing the above monomers by emulsion polymerization using an emulsifier. This is preferably produced by hydrogenation, followed by solidification and drying. In emulsion polymerization, commonly used polymerization auxiliary materials such as emulsifiers, polymerization initiators, molecular weight regulators and the like can be used.

  Although it does not specifically limit as an emulsifier, For example, nonionic emulsifiers, such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester; myristic acid, palmitic acid, oleic acid And anionic emulsifiers such as salts of fatty acids such as linolenic acid, alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate, higher alcohol sulfates, and alkyl sulfosuccinates; sulfoesters of α, β-unsaturated carboxylic acids, α , Β-unsaturated carboxylic acid sulfate esters, sulfoalkyl aryl ethers and other copolymerizable emulsifiers. The amount of the emulsifier used is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the total monomers.

  The polymerization initiator is not particularly limited as long as it is a radical initiator, but inorganic peroxides such as potassium persulfate, sodium persulfate, ammonium persulfate, potassium perphosphate, hydrogen peroxide; t-butyl peroxide, cumene Hydroperoxide, p-menthane hydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, dibenzoyl peroxide, 3, 5, 5 Organic peroxides such as trimethylhexanoyl peroxide and t-butylperoxyisobutyrate; azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate, etc. Azotization Ones; and the like. These polymerization initiators can be used alone or in combination of two or more. As the polymerization initiator, an inorganic or organic peroxide is preferable. When a peroxide is used as the polymerization initiator, it can be used as a redox polymerization initiator in combination with a reducing agent such as sodium bisulfite or ferrous sulfate. The amount of the polymerization initiator used is preferably 0.001 to 2 parts by weight, more preferably 0.01 to 2 parts by weight with respect to 100 parts by weight of the total monomers.

  The molecular weight modifier is not particularly limited, but mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, octyl mercaptan; halogenated hydrocarbons such as carbon tetrachloride, methylene chloride, methylene bromide; α-methylstyrene dimer And sulfur-containing compounds such as tetraethylthiuram disulfide, dipentamethylene thiuram disulfide, and diisopropylxanthogen disulfide. These can be used alone or in combination of two or more. Among these, mercaptans are preferable, and t-dodecyl mercaptan is more preferable. The amount of the molecular weight modifier used is preferably 0.1 to 1.5 parts by weight with respect to 100 parts by weight of all monomers.

  Usually, water is used as a medium for emulsion polymerization. The amount of water is preferably 80 to 500 parts by weight with respect to 100 parts by weight of the total monomers.

  In the emulsion polymerization, polymerization auxiliary materials such as a stabilizer, a dispersant, a pH adjuster, an oxygen scavenger, and a particle size adjuster can be used as necessary. In using these, neither the kind nor the usage-amount is specifically limited.

  And when the iodine value of the obtained copolymer exceeds 120, the carboxyl group-containing highly saturated nitrile rubber (A) is obtained by selectively hydrogenating the double bond of the conjugated diene monomer unit. Can be manufactured. In addition, what is necessary is just to determine according to a well-known method the kind and quantity of the hydrogenation catalyst used for hydrogenation, hydrogenation temperature, etc. The hydrogenation may be performed in a latex state, or may be performed in a solution after isolating the copolymer. After hydrogenation, the carboxyl group-containing highly saturated nitrile rubber (A) can be isolated by coagulation and drying.

Compound having hydroxyl group (D)
The crosslinkable rubber composition of the present invention comprises a fatty acid (B) having 10 to 20 carbon atoms and an alcohol (C) having 10 to 20 carbon atoms with respect to 100 parts by weight of the carboxyl group-containing highly saturated nitrile rubber (A). 2 to 20 parts by weight of a compound (D) having at least one hydroxyl group selected from the group is contained.

  The compound (D) having a hydroxyl group is not particularly limited as long as it is selected from the group consisting of a fatty acid (B) having 10 to 20 carbon atoms and an alcohol (C) having 10 to 20 carbon atoms. From the viewpoint of improving the bleed resistance and compression set resistance of the product, an alcohol (C) having 10 to 20 carbon atoms is preferred.

  The usage-amount of the compound (D) which has a hydroxyl group is 2-20 weight part with respect to 100 weight part of carboxyl group-containing highly saturated nitrile rubber (A), Preferably it is 2-15 weight part. When there is too little usage-amount of the compound (D) which has a hydroxyl group, there exists a possibility that the fluidity | liquidity of a crosslinkable rubber composition may deteriorate. Moreover, when there is too much usage-amount of the compound (D) which has a hydroxyl group, the bleed resistance and compression set resistance of the rubber crosslinked material obtained may deteriorate.

  Specific examples of the fatty acid (B) having 10 to 20 carbon atoms include saturated fatty acids having 10 to 20 carbon atoms such as lauric acid, myristic acid, palmitic acid and stearic acid; oleic acid, linoleic acid, linolenic acid and the like. The unsaturated fatty acid having 10 to 20 carbon atoms; and the like. However, since the effect of the present invention becomes more remarkable, the saturated fatty acid having 10 to 20 carbon atoms is preferable, and the saturated fatty acid having 15 to 20 carbon atoms. Fatty acids are more preferred and stearic acid is particularly preferred.

  Specific examples of the alcohol (C) having 10 to 20 carbon atoms include saturated alcohols having 10 to 20 carbon atoms such as lauryl alcohol, tridecanol, myristyl alcohol, palmityl alcohol, heptadecanol, stearyl alcohol, and eicosanol; 4-dodecadien-1-ol, 2-dodecenol, oleyl alcohol, linoleyl alcohol and other unsaturated alcohols having 10 to 20 carbon atoms; and the like. A saturated alcohol having 10 to 20 carbon atoms is preferable, a linear saturated alcohol having 10 to 20 carbon atoms having one hydroxyl group bonded to a terminal carbon atom is more preferable, and lauryl alcohol and stearyl alcohol are particularly preferable.

Polyamine crosslinking agent (E)
The crosslinkable rubber composition of the present invention has a polyamine crosslinking agent (E) of 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight, based on 100 parts by weight of the carboxyl group-containing highly saturated nitrile rubber (A). Particularly preferably, it contains 0.5 to 5 parts by weight. When there is too little content of a polyamine crosslinking agent (E), there exists a possibility that the mechanical characteristic and compression set resistance of a rubber crosslinked material obtained may deteriorate. On the other hand, if it is too much, the bending fatigue resistance of the resulting rubber cross-linked product may be deteriorated.

The polyamine crosslinking agent (E) used in the present invention is not particularly limited as long as it is a compound having two or more amino groups or a compound having two or more amino groups at the time of crosslinking. A compound in which a plurality of hydrogen atoms of an aliphatic hydrocarbon or aromatic hydrocarbon are substituted with an amino group or a hydrazide structure (a structure represented by —CONHNH ₂ , CO represents a carbonyl group) and Those in the form are preferred. Specific examples thereof include aliphatic polyamines such as hexamethylene diamine, hexamethylene diamine carbamate, tetramethylene pentamine, hexamethylene diamine cinnamaldehyde adduct, hexamethylene diamine dibenzoate salt; 2,2-bis {4- Aromatic polyamines such as (4-aminophenoxy) phenyl} propane, 4,4′-methylenedianiline, m-phenylenediamine, p-phenylenediamine, 4,4′-methylenebis (o-chloroaniline); And compounds having two or more hydrazide structures such as isophthalic acid dihydrazide, adipic acid dihydrazide, and sebacic acid dihydrazide. Among these, aliphatic polyvalent amines are preferable, and hexamethylenediamine carbamate is particularly preferable.

  Moreover, it is preferable that the crosslinkable rubber composition of the present invention further contains a basic crosslinking accelerator. By further containing a basic crosslinking accelerator, the effect of the present invention becomes more remarkable.

  Specific examples of the basic crosslinking accelerator include 1,8-diazabicyclo [5,4,0] undecene-7 (hereinafter sometimes abbreviated as “DBU”) and 1,5-diazabicyclo [4,3,0]. Nonene-5 (hereinafter sometimes abbreviated as “DBN”), 1-methylimidazole, 1-ethylimidazole, 1-phenylimidazole, 1-benzylimidazole, 1,2-dimethylimidazole, 1-ethyl-2-methylimidazole 1-methoxyethylimidazole, 1-phenyl-2-methylimidazole, 1-benzyl-2-methylimidazole, 1-methyl-2-phenylimidazole, 1-methyl-2-benzylimidazole, 1,4-dimethylimidazole, 1,5-dimethylimidazole, 1,2,4-trimethylimidazole, 1,4-dimethyl-2-ethyl ester Dazole, 1-methyl-2-methoxyimidazole, 1-methyl-2-ethoxyimidazole, 1-methyl-4-methoxyimidazole, 1-methyl-2-methoxyimidazole, 1-ethoxymethyl-2-methylimidazole, 1- Methyl-4-nitroimidazole, 1,2-dimethyl-5-nitroimidazole, 1,2-dimethyl-5-aminoimidazole, 1-methyl-4- (2-aminoethyl) imidazole, 1-methylbenzimidazole, 1 -Methyl-2-benzylbenzimidazole, 1-methyl-5-nitrobenzimidazole, 1-methylimidazoline, 1,2-dimethylimidazoline, 1,2,4-trimethylimidazoline, 1,4-dimethyl-2-ethylimidazoline 1-methyl-phenylimidazoline, 1-methyl-2 -Benzylimidazoline, 1-methyl-2-ethoxyimidazoline, 1-methyl-2-heptylimidazoline, 1-methyl-2-undecylimidazoline, 1-methyl-2-heptadecylimidazoline, 1-methyl-2-ethoxymethyl Basic crosslinking accelerators having a cyclic amidine structure such as imidazoline and 1-ethoxymethyl-2-methylimidazoline; such as tetramethylguanidine, tetraethylguanidine, diphenylguanidine, 1,3-di-ortho-tolylguanidine, orthotolylbiguanide And guanidine-based basic crosslinking accelerators; aldehyde amine-based basic crosslinking accelerators such as n-butyraldehyde aniline and acetaldehyde ammonia; Among these, guanidine-based basic crosslinking accelerators and basic crosslinking accelerators having a cyclic amidine structure are preferable, basic crosslinking accelerators having a cyclic amidine structure are more preferable, and 1,8-diazabicyclo [5,4, 0] undecene-7 and 1,5-diazabicyclo [4,3,0] nonene-5 are more preferred, and 1,8-diazabicyclo [5,4,0] undecene-7 is particularly preferred. The basic crosslinking accelerator having a cyclic amidine structure may form a salt with an organic carboxylic acid or an alkyl phosphoric acid.

  The amount of the basic crosslinking accelerator in the crosslinkable rubber composition of the present invention is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the carboxyl group-containing highly saturated nitrile rubber (A), More preferably, it is 0.2-15 weight part, More preferably, it is 0.5-10 weight part. If the blending amount of the basic crosslinking accelerator is too small, the crosslinking rate of the crosslinkable rubber composition may be too slow and the crosslinking density may be lowered. On the other hand, if the blending amount is too large, the crosslinking rate of the crosslinkable rubber composition may be too high to cause scorching, or the storage stability may be impaired.

In addition, you may mix | blend rubber other than the carboxyl group containing highly saturated nitrile rubber (A) mentioned above in the range which does not inhibit the effect of this invention in the crosslinkable rubber composition of this invention.
Such rubbers include styrene-butadiene copolymer rubber, polybutadiene rubber, ethylene-propylene copolymer rubber, ethylene-propylene-diene terpolymer rubber, urethane rubber, silicone rubber, natural rubber, polyisoprene rubber. Etc.
The amount of rubber other than the carboxyl group-containing highly saturated nitrile rubber (A) in the crosslinkable rubber composition is preferably 60 parts by weight or less with respect to 100 parts by weight of the carboxyl group-containing highly saturated nitrile rubber (A). More preferably, it is 30 weight part or less, More preferably, it is 10 weight part or less.

  Moreover, you may mix | blend a plasticizer with the crosslinkable rubber composition of this invention in the range which does not inhibit the effect of this invention. The plasticizer is not particularly limited, and a plasticizer usually used in the rubber processing field can also be used. The amount of the plasticizer is preferably 1 to 20 parts by weight, particularly preferably 1 to 10 parts by weight, based on 100 parts by weight of the carboxyl group-containing highly saturated nitrile rubber (A).

  In addition to the above-described components, the crosslinkable rubber composition of the present invention may contain other compounding agents that are usually used in the rubber processing field. Such compounding agents include, for example, reinforcing agents, fillers, antioxidants, light stabilizers, scorch inhibitors, processing aids, lubricants, adhesives, lubricants, flame retardants, antifungal agents, and antistatic agents. , Coloring agents, silane coupling agents, crosslinking aids, crosslinking retarders, foaming agents and the like. The compounding amounts of these compounding agents can be appropriately used in accordance with the compounding purpose.

  The crosslinkable rubber composition of the present invention is prepared by mixing the above components, preferably in a non-aqueous system. As a method for suitably preparing the crosslinkable rubber composition of the present invention, the components excluding heat-labile components such as a crosslinking agent are first kneaded with a mixer such as a Banbury mixer, an intermixer, or a kneader, and then opened. For example, it may be transferred to a roll or the like and added with a thermally unstable component such as a cross-linking agent, followed by secondary kneading. The primary kneading is usually performed at a temperature of 10 to 200 ° C., preferably 30 to 180 ° C., for 1 minute to 1 hour, preferably 1 minute to 30 minutes, and the secondary kneading is usually 10 to 100 ° C., Preferably, it is performed at a temperature of 20 to 60 ° C. for 1 minute to 1 hour, preferably 1 minute to 30 minutes.

The compound Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the crosslinkable rubber composition of the present invention is preferably 5 to 200, more preferably 10 to 150, still more preferably 20 to 100, and particularly preferably 40 to 90.

Examples of the molding method of the crosslinkable rubber composition of the present invention include injection molding, extrusion molding, compression molding, roll molding, and the like. However, since the crosslinkable rubber composition of the present invention is excellent in fluidity, injection molding can be performed. preferable. That is, the crosslinkable rubber composition of the present invention is suitably used as a crosslinkable rubber composition for injection molding.

The rubber cross-linked product of the present invention is obtained by cross-linking the cross-linkable rubber composition of the present invention described above.
The rubber cross-linked product of the present invention uses the cross-linkable rubber composition of the present invention, for example, is molded by a molding method corresponding to a desired shape, and undergoes a cross-linking reaction by heating to fix the shape as a cross-linked product Can be manufactured.

  In this case, crosslinking may be performed after molding in advance, or crosslinking may be performed simultaneously with molding. The molding temperature is usually 10 to 200 ° C, preferably 25 to 120 ° C. The crosslinking temperature is usually 100 to 250 ° C., preferably 110 to 220 ° C., more preferably 120 to 200 ° C., and the crosslinking time is usually 1 minute to 24 hours, preferably 2 minutes to 12 hours, particularly preferably. Is 3 minutes to 6 hours.

  Further, depending on the shape and size of the rubber cross-linked product, even if the surface is cross-linked, it may not be sufficiently cross-linked to the inside. Therefore, secondary cross-linking may be performed by heating.

  As a heating method, a general method used for crosslinking of rubber such as press heating, steam heating, oven heating, and hot air heating may be appropriately selected.

  The rubber cross-linked product of the present invention thus obtained has excellent bleed resistance in addition to the properties of a highly saturated nitrile rubber cross-linked product excellent in mechanical strength, heat resistance and oil resistance.

  For this reason, the rubber cross-linked product of the present invention is used for O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, well head seals, pneumatic equipment seals, air conditioner cooling devices and air conditioner refrigerators. Fluorocarbon or fluorohydrocarbon or carbon dioxide sealing seals used in compressors, supercritical carbon dioxide or subcritical carbon dioxide sealing seals used in precision cleaning media, rolling devices (rolling bearings, for automobiles) Various seals such as seals for hub units, automotive water pumps, linear guide devices, ball screws, etc.), valves and valve seats, BOP (Blow Out Preventar), platters, etc .; are attached to the connection between the intake manifold and cylinder head Intake Maniho Cylinder gasket, cylinder head gasket attached to the connecting part of the cylinder block and cylinder head, rocker cover gasket attached to the connecting part of the rocker cover and cylinder head, oil pan and cylinder block or transmission case Various gaskets such as an oil pan gasket to be mounted, a gasket for a fuel cell separator mounted between a pair of housings sandwiching a unit cell having a positive electrode, an electrolyte plate and a negative electrode, a top cover gasket for a hard disk drive, a printing roll, Various rolls such as steelmaking rolls, papermaking rolls, industrial rolls, and office machine rolls; flat belts (film core flat belts, cord flat belts, laminated flat belts, single flat belts, etc.), V belts (wrapped V) Belt, b Edge V belts, etc.), V-ribbed belts (single V-ribbed belt, double V-ribbed belt, wrapped V-ribbed belt, back rubber V-ribbed belt, upper cog V-ribbed belt, etc.), CVT belt, timing belt, toothed belt, conveyor belt, etc. Belt: Fuel hose, turbo air hose, oil hose, radiator hose, heater hose, water hose, vacuum brake hose, control hose, air conditioner hose, brake hose, power steering hose, air hose, marine hose, riser, flow line, etc. Various hoses; Various boots such as CVJ boots, propeller shaft boots, constant velocity joint boots, rack and pinion boots; cushion materials, dynamic dampers, rubber couplings, empty Attenuating rubber parts such as air springs and anti-vibration materials; dust covers, automotive interior parts, tires, coated cables, shoe soles, electromagnetic shielding, adhesives for flexible printed circuit boards, fuel cell separators, and other electronics fields It can be used for a wide range of applications.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples. In the following, “part” is based on weight unless otherwise specified. The test and evaluation were as follows.

The iodine value of the highly saturated nitrile rubber containing iodine value carboxyl group was measured according to JIS K6235.

Carboxyl group content The carboxyl group content of the carboxyl group-containing highly saturated nitrile rubber was measured by the following method. That is, 100 ml of 2-butanone was added to 0.2 g of a 2 mm square carboxyl group-containing highly saturated nitrile rubber and stirred for 16 hours to dissolve, and then 20 ml of ethanol and 10 ml of water were added, and while stirring, 0 ml of potassium hydroxide was added. Using a 0.02N aqueous ethanol solution, titration with thymolphthalein as an indicator at 25 ° C. was performed to determine the number of moles of carboxyl groups relative to 100 g of carboxyl group-containing highly saturated nitrile rubber (unit: ephr).

Mooney viscosity The Mooney viscosity (polymer Mooney) of the highly saturated nitrile rubber containing carboxyl group and the Mooney viscosity (compound Mooney) of the crosslinkable rubber composition were measured according to JIS K6300 (unit: (ML _{1 + 4} , 100 ° C.)).

Normal physical properties (tensile strength, elongation, hardness)
The crosslinkable rubber composition was placed in a mold having a length of 15 cm, a width of 15 cm, and a depth of 0.2 cm, and subjected to primary crosslinking by pressing at 170 ° C. for 20 minutes while pressing at a press pressure of 10 MPa, and then the obtained primary was obtained. The crosslinked product was further subjected to secondary crosslinking by heating at 170 ° C. for 4 hours in a gear oven to obtain a sheet-like rubber crosslinked product. The obtained sheet-like rubber cross-linked product was punched out with a No. 3 dumbbell to prepare a test piece. Next, using this test piece, tensile strength and elongation were measured according to JIS K6251, and hardness was measured using a durometer hardness tester (type A) according to JIS K6253.

Using a mold having a compression set of 30 mm inner diameter and a ring diameter of 3 mm, the crosslinkable rubber composition was crosslinked at 170 ° C. for 20 minutes at a press pressure of 10 MPa, and then subjected to secondary crosslinking at 170 ° C. for 4 hours. An O-ring test piece was obtained. Then, using the obtained O-ring-shaped test piece, the distance between two planes sandwiching the O-ring-shaped test piece is held at 150 ° C. for 168 hours in a state compressed by 25% in the ring thickness direction. The O-ring compression set was measured in accordance with JIS K6262. The smaller this value, the better the compression set resistance.

Oil-resistant immersion test An oil-resistant immersion test was performed according to JIS K6258.
That is, in the same manner as in the case of the above-described normal physical properties, a sheet-like rubber cross-linked product is obtained, and the obtained sheet-like rubber cross-linked product is punched into a shape of 25 mm in length and 20 mm in width, for oil resistance immersion test. A test piece was prepared. Next, this test piece was immersed in the test lubricating oil IRM901 under conditions of a temperature of 150 ° C. and 168 hours. And about the rubber crosslinked material immersed in oil, oil resistance was evaluated by measuring the volume change rate (unit:%) before and behind immersion. The smaller the absolute value of the volume change rate before and after immersion, the better the oil resistance.

Cross-linked sheet storage (bleed resistance)
In the same manner as the evaluation of the normal physical properties described above, a sheet-like rubber cross-linked product was obtained, and the obtained sheet-like rubber cross-linked product was punched into a shape of 40 mm in length and 30 mm in width to obtain a cross-linked sheet (sheet-like rubber). A test piece for a storage property test of (crosslinked product) was prepared. Next, this test piece was placed in a thermostatic oven at a temperature of 40 ° C. and a humidity of 80% and left for 168 hours. Next, the surface state of the taken-out test piece was observed, and the storability of the crosslinked sheet was evaluated. Evaluation was performed according to the following criteria.
○: White turbidity is not observed on the cross-linked sheet surface, and no bleed material is observed. ×: The cross-linked sheet surface is turbid white and bleed material is observed. The presence or absence of the bleed material is determined with a metal spatula. It was judged by whether or not the bleed product (solid matter that separated from the crosslinked sheet and floated on the surface) was peeled off.

Synthesis Example 1 (Production of carboxyl group-containing highly saturated nitrile rubber (a))
In a metal bottle, 180 parts of ion-exchanged water, 25 parts of an aqueous solution of sodium dodecylbenzenesulfonate having a concentration of 10% by weight, 37 parts of acrylonitrile, 6 parts of mono-n-butyl maleate, t-dodecyl mercaptan (molecular weight regulator) 0.75 In order of parts, the internal gas was replaced with nitrogen three times, and then 57 parts of 1,3-butadiene was charged. The metal bottle was kept at 5 ° C., 0.1 part of cumene hydroperoxide (polymerization initiator) was charged, and the polymerization reaction was carried out for 16 hours while rotating the metal bottle. Thereafter, 0.1 part of a 10% by weight hydroquinone aqueous solution (polymerization terminator) was added to stop the polymerization reaction, and the contents of the metal bottle were transferred to a glass flask. Subsequently, a rotary evaporator with a water temperature of 60 ° C. was used. The residual monomer was removed under reduced pressure to obtain a latex (solid content concentration of about 30% by weight) of acrylonitrile-butadiene-mono-n-butyl maleate copolymer rubber.
Next, a palladium catalyst (a solution in which 1 wt% palladium acetate / acetone solution and equal weight of ion exchange water are mixed) is added to the autoclave so that the palladium content becomes 1000 ppm with respect to the rubber weight contained in the latex. Then, a hydrogenation reaction was performed at a hydrogen pressure of 3 MPa and a temperature of 50 ° C. for 6 hours to obtain a latex of carboxyl group-containing highly saturated nitrile rubber (a).
The resulting latex of carboxyl group-containing highly saturated nitrile rubber (a) was solidified by adding twice the volume of methanol, and then vacuum-dried at 60 ° C. for 12 hours to obtain a carboxyl group-containing highly saturated nitrile rubber (a ) The obtained carboxyl group-containing highly saturated nitrile rubber (a) had an iodine value of 10, a carboxyl group content of 3.2 × 10 ⁻² ephr, and a polymer Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 45.
In addition, the acrylonitrile unit content was calculated | required by the Kjeldahl method, the mono n-butyl maleate unit content was calculated | required from carboxyl group content, and the carboxyl group-containing highly saturated nitrile rubber | gum which calculated | required the remainder as a 1, 3- butadiene unit ( The composition of a) was 36% by weight of acrylonitrile units, 58.5% by weight of butadiene units (including those which were hydrogenated), and 5.5% by weight of mono n-butyl maleate units.

Example 1
Using a Banbury mixer, 100 parts of the carboxyl group-containing highly saturated nitrile rubber (a) obtained in Synthesis Example 1, 40 parts of FEF carbon black (trade name “SEAST SO”, manufactured by Tokai Carbon Co., Ltd.), trimellitic acid tri 2-ethylhexyl (trade name “Adekasizer C-8”, manufactured by ADEKA, plasticizer), 5 parts, 4,4′-di- (α, α-dimethylbenzyl) diphenylamine (trade name “NOCLACK CD”, large Inner Shinsei Chemical Co., Ltd., anti-aging agent) 1.5 parts, stearic acid 1 part, and stearyl alcohol (Wako Pure Chemical Industries, Ltd., C18 saturated alcohol) 4 parts are added and at 50 ° C. for 5 minutes. Mixed. Subsequently, the obtained mixture was transferred to a roll at 50 ° C., and 2.6 parts of hexamethylenediamine carbamate (trade name “Diak # 1”, manufactured by DuPont Dow Elastomer Co., Ltd., polyamine crosslinking agent belonging to aliphatic polyamines). , And 1,8-diazabicyclo [5,4,0] -undecene-7 (DBU) (trade name “RHENOGRAN XLA-60 (GE2014)”, manufactured by RheinChemie, DBU 60% (becomes zinc dialkyldiphosphate salt) 4 parts of a basic crosslinking accelerator) were mixed and kneaded to obtain a crosslinkable rubber composition.

  Then, using the obtained crosslinkable rubber composition, each of the compound Mooney viscosity, normal physical properties, oil immersion test, compression set test, and storability (bleed resistance) of the cross-linked sheet was performed by the methods described above. It was. The results are shown in Table 1.

Example 2
In Example 1, a crosslinkable rubber composition was obtained in the same manner as in Example 1 except that 8 parts of stearyl alcohol was used instead of 4 parts of stearyl alcohol, and evaluation was performed in the same manner. The results are shown in Table 1.

Example 3
In Example 1, a crosslinkable rubber composition was obtained in the same manner as in Example 1 except that 12 parts of stearyl alcohol was used instead of 4 parts of stearyl alcohol, and evaluation was performed in the same manner. The results are shown in Table 1.

Example 4
In Example 1, instead of using 4 parts of stearyl alcohol and 1 part of stearic acid, a crosslinkable rubber composition was used in the same manner as in Example 1 except that 6 parts of stearic acid (saturated fatty acid having 18 carbon atoms) was used. Things were obtained and evaluated in the same manner. The results are shown in Table 1.

Example 5
In Example 1, a crosslinkable rubber composition was used in the same manner as in Example 1 except that 6 parts of lauryl alcohol (Wako Pure Chemical Industries, Ltd., saturated carbon number 12) was used instead of 4 parts of stearyl alcohol. Were similarly evaluated. The results are shown in Table 1.

Comparative Example 1
In Example 1, except that 1 part of stearic acid and 4 parts of stearyl alcohol were not used, a crosslinkable rubber composition was obtained in the same manner as in Example 1 and evaluated in the same manner. The results are shown in Table 1.

Comparative Example 2
In Example 1, a crosslinkable rubber composition was obtained in the same manner as in Example 1 except that 4 parts of stearyl alcohol was not used, and evaluated in the same manner. The results are shown in Table 1.

Comparative Example 3
In Example 1, instead of 4 parts of stearyl alcohol, 8 parts of stearylamine (trade name “Farmin 80” manufactured by Kao Corporation, 18-carbon amine compound) was used in the same manner as in Example 1 to perform crosslinking. The rubber composition was obtained and evaluated in the same manner. The results are shown in Table 1.

Comparative Example 4
In Example 1, 4 parts of stearyl alcohol was not used, but the amount of trimellitic acid tri-2-ethylhexyl (trade name “Adekasizer C-8”, manufactured by ADEKA, plasticizer) was increased to 15 parts. In the same manner as in Example 1, a crosslinkable rubber composition was obtained and evaluated in the same manner. The results are shown in Table 1.

  From Table 1, the carboxyl group-containing highly saturated nitrile rubber (a) has at least one hydroxyl group selected from the group consisting of fatty acids having 10 to 20 carbon atoms and alcohols having 10 to 20 carbon atoms in an amount specified in the present application. When the compound having the formula is further blended and the polyamine crosslinking agent in the amount specified in the present application is further blended, the resulting rubber cross-linked product is excellent in the storage stability (bleed resistance) of the cross-linked sheet, and also has good strength and oil resistance. In addition, since the compound Mooney viscosity of the crosslinkable rubber composition was low, the flowability of the crosslinkable rubber composition at the time of injection molding could be improved (Examples 1 to 5). In addition, when a C10-20 alcohol was used as the compound having a hydroxyl group, the obtained rubber cross-linked product was excellent in compression set resistance (Examples 1-3 and Examples). Example 5).

On the other hand, when neither a fatty acid having 10 to 20 carbon atoms nor an alcohol having 10 to 20 carbon atoms is used (Comparative Example 1), and a fatty acid having 10 to 20 carbon atoms is used, its use When the amount was less than the amount specified in this application (Comparative Example 2), the compound Mooney viscosity of the crosslinkable rubber composition was high, resulting in poor fluidity during injection molding.
In addition, when stearylamine (amine compound) was used instead of a fatty acid having 10 to 20 carbon atoms or an alcohol having 10 to 20 carbon atoms, the compound Mooney viscosity of the crosslinkable rubber composition could be lowered. However, it was inferior in the storage property (bleed resistance) and compression set resistance of the crosslinked sheet of the obtained rubber crosslinked product (Comparative Example 3).
Further, when the compound Mooney viscosity of the crosslinkable rubber composition is lowered by increasing the amount of the plasticizer without using a C10-20 fatty acid or a C10-20 alcohol, It became a result inferior to property (comparative example 4).

Claims (7)

(I) Carboxyl group-containing highly saturated nitrile rubber (A) 100 parts by weight,
(Ii) 2-20 parts by weight of a compound (D) having at least one hydroxyl group selected from the group consisting of a fatty acid (B) having 10 to 20 carbon atoms and an alcohol (C) having 10 to 20 carbon atoms, and (Iii) 0.1 to 10 parts by weight of a polyamine crosslinking agent (E),
A crosslinkable rubber composition comprising:   The crosslinkable rubber composition according to claim 1, wherein the hydroxyl group-containing compound (D) is an alcohol (C) having 10 to 20 carbon atoms.   The crosslinkable rubber composition according to claim 2, wherein the alcohol (C) is a saturated alcohol having 10 to 20 carbon atoms.   The carboxyl group-containing highly saturated nitrile rubber (A) comprises 5 to 60% by weight of α, β-ethylenically unsaturated nitrile monomer unit, 39.5 to 80% by weight of conjugated diene monomer unit, and carboxyl The crosslinkable rubber composition according to any one of claims 1 to 3, wherein the group-containing monomer unit is contained in a proportion of 0.5 to 15% by weight.   The crosslinkable rubber composition according to claim 4, wherein the carboxyl group-containing monomer unit is an α, β-ethylenically unsaturated dicarboxylic acid monoalkyl ester monomer unit.   A crosslinkable rubber composition for injection molding comprising the crosslinkable rubber composition according to any one of claims 1 to 5.   A rubber cross-linked product obtained by cross-linking the cross-linkable rubber composition according to claim 1.