JP5531729B2 - Rubber composition and cross-linked product - Google Patents

Description

  The present invention relates to a rubber composition capable of providing a crosslinked product excellent in mechanical properties, oil resistance, and compression set resistance, and a crosslinked product obtained using the rubber composition.

  Nitrile rubber (acrylonitrile-butadiene copolymer rubber) 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. Hydrogenated nitrile rubber (hydrogenated acrylonitrile-butadiene copolymer rubber) in which the carbon-carbon double bond in the polymer chain of the rubber is hydrogenated is superior in heat resistance, so it is used for rubber parts such as belts, hoses, diaphragms, etc. Has been.

  For this situation, Patent Document 1 discloses a crosslinkable rubber containing a hydrogenated nitrile rubber having an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit, a polyamine-based crosslinking agent, and a basic crosslinking accelerator. A composition is proposed. Although a crosslinked product having moderately improved heat resistance and compression set can be obtained with the composition, there has been a demand for further improvement of oil resistance while maintaining good compression set resistance.

JP 2001-55471 A

  An object of the present invention is to provide a rubber composition capable of providing a crosslinked product excellent in mechanical properties, oil resistance, and compression set resistance, and a crosslinked product obtained using the rubber composition. To do.

  As a result of diligent research to achieve the above object, the present inventors have obtained a rubber composition obtained by blending a specific vinyl alcohol copolymer with a carboxyl group-containing nitrile rubber having an iodine value of 120 or less. The inventors have found that the object can be achieved and have completed the present invention.

That is, according to the present invention, the α, β-ethylenically unsaturated nitrile monomer unit is 5 to 60% by weight, the carboxyl group-containing monomer unit is 0.1 to 20% by weight, and the conjugated diene monomer unit is 15 to An ethylene-vinyl alcohol copolymer (B) having an ethylene content of 10 to 60 mol% with respect to 100 parts by weight of the carboxyl group-containing nitrile rubber (A) having 89.9% by weight and an iodine value of 120 or less. ) A rubber composition comprising 5 to 100 parts by weight is provided.

The carboxyl group-containing nitrile rubber (A) is an α, β-ethylenically unsaturated nitrile monomer unit of 5 to 60% by weight, a carboxyl group-containing monomer unit of 0.1 to 20% by weight, a conjugated diene monomer. It contains 15 to 89.9% by weight of units and 5 to 60% by weight of α, β-ethylenically unsaturated monocarboxylic acid ester monomer units , and preferably has an iodine value of 120 or less .

According to the present invention, there is also provided a crosslinkable rubber composition comprising any of the above rubber compositions and a polyamine crosslinking agent.
Furthermore, according to the present invention, a cross-linked product obtained by cross-linking the cross-linkable rubber composition is provided, and the cross-linked product is preferably a rubber member for sealing, a belt, a hose or a gasket.
In the method for producing a rubber composition of the present invention, the carboxyl group-containing nitrile rubber (A) and the ethylene-vinyl alcohol copolymer (B) are equal to or higher than the melting point of the ethylene-vinyl alcohol copolymer (B). Kneading at a temperature of

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition which can give the crosslinked material excellent in mechanical characteristics, oil resistance, and compression set resistance can be provided. Further, according to the present invention, it is possible to provide a crosslinked product obtained by crosslinking the rubber composition and having excellent mechanical properties, oil resistance, and compression set resistance.

Rubber composition The rubber composition of the present invention comprises a carboxyl group-containing nitrile rubber (A) having an iodine value of 120 or less, an ethylene-vinyl alcohol copolymer (B) having an ethylene content of 10 to 60 mol%, and , Containing.

Carboxyl group-containing nitrile rubber (A)
First, the carboxyl group-containing nitrile rubber (A) having an iodine value of 120 or less used in the present invention will be described. The carboxyl group-containing nitrile rubber (A) having an iodine value of 120 or less used in the present invention (hereinafter simply referred to as “carboxyl group-containing nitrile rubber (A)”) is an α, β-ethylenically unsaturated nitrile monomer. A rubber having an iodine value of 120 or less, obtained by copolymerizing a carboxyl group-containing monomer and other copolymerizable monomers added as necessary.

  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; and the like. Among these, acrylonitrile and methacrylonitrile are preferable, and acrylonitrile is more 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 55% by weight, and still more preferably 15 to 50% based on the total monomer units. % By weight. If the content of the α, β-ethylenically unsaturated nitrile monomer unit is too small, the oil resistance of the resulting cross-linked product may be lowered, and conversely if too much, cold resistance may be lowered. .

  The carboxyl group-containing monomer can be copolymerized with an α, β-ethylenically unsaturated nitrile monomer and has at least one unsubstituted (free) carboxyl group that is not esterified. If it is a monomer, it will not specifically limit. By using a carboxyl group-containing monomer, a carboxyl group can be introduced into the nitrile rubber. And thereby, the dispersibility of the ethylene-vinyl alcohol copolymer (B) in the rubber composition can be increased, and as a result, it is possible to improve the compression set resistance in the case of a crosslinked product. Become.

  Examples of the carboxy group-containing monomer used in the present invention include α, β-ethylenically unsaturated monocarboxylic acid monomers, α, β-ethylenically unsaturated polycarboxylic acid monomers, and α, β -Ethylenically unsaturated dicarboxylic acid monoester monomer and the like. 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-ethylenically unsaturated polyvalent carboxylic acid monomer include butenedionic acid such as fumaric acid and maleic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, allylmalonic acid, and teraconic acid. Examples of the anhydride of α, β-unsaturated polyvalent carboxylic acid include maleic anhydride, itaconic anhydride, and citraconic anhydride.

  As the α, β-ethylenically unsaturated dicarboxylic acid monoester monomer, maleic acid monoalkyl esters such as monomethyl maleate, monoethyl maleate, monopropyl maleate, mono n-butyl maleate; monocyclopentyl maleate, Maleic acid monocycloalkyl esters such as monocyclohexyl maleate and monocycloheptyl maleate; Monoalkyl cycloalkyl esters of maleic acid such as monomethylcyclopentyl maleate and monoethylcyclohexyl maleate; Monomethyl fumarate, monoethyl fumarate and monofumarate Monoalkyl esters of fumaric acid such as propyl and mono-n-butyl fumarate; mono-fumaric acid such as monocyclopentyl fumarate, monocyclohexyl fumarate and monocycloheptyl fumarate Cycloalkyl esters; fumaric acid monoalkyl cycloalkyl esters such as monomethylcyclopentyl fumarate and monoethylcyclohexyl fumarate; citraconic acid monoalkyl esters such as monomethyl citraconic acid, monoethyl citraconic acid, monopropyl citraconic acid and mono n-butyl citraconic acid Citraconic acid monocycloalkyl ester such as citraconic acid monocyclopentyl, citraconic acid monocyclohexyl, citraconic acid monocycloheptyl, etc .; citraconic acid monomethylcyclopentyl, citraconic acid monoethylcyclohexyl citraconic acid monoalkyl cycloalkyl ester; itaconic acid monomethyl itacon Monoalkyl itaconate such as monoethyl acrylate, monopropyl itaconate, mono n-butyl itaconate Esters; itaconic acid monocyclopentyl, itaconic acid monocyclohexyl, itaconic acid monocycloheptyl, etc. itaconic acid monocycloalkyl ester; itaconic acid monomethylcyclopentyl, itaconic acid monoethylcyclohexyl, etc. .

  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, maleic acid monoalkyl ester is more preferable, and mono n-butyl maleate is preferable because the effects of the present invention become more remarkable. Is particularly preferred. 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 from 0.1 to 20% by weight, more preferably from 0.2 to 15% by weight, and even more preferably from 0.5 to 10%, based on all monomer units. % By weight. If the content of the carboxyl group-containing monomer unit is too small, the dispersibility of the ethylene-vinyl alcohol copolymer (B) in the rubber composition is lowered, and the compression set of the resulting crosslinked product is compression set. May decrease. On the other hand, if the amount is too large, the scorch stability of the rubber composition may deteriorate, or the fatigue resistance of the resulting crosslinked product may decrease.

  Moreover, it is preferable that the carboxyl group-containing nitrile rubber (A) used in the present invention also contains a conjugated diene monomer unit so that the resulting crosslinked product has rubber elasticity.

  Examples of the conjugated diene monomer that forms the conjugated diene monomer unit include 4-carbon atoms such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and chloroprene. 6 conjugated diene monomers are preferred, 1,3-butadiene and isoprene are more preferred, and 1,3-butadiene is 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 (including the hydrogenated portion) is preferably 15 to 89.9% by weight, more preferably 20 to 79.8% by weight, based on the total monomer units. More preferably, it is 25 to 69.5% by weight. If the content of the conjugated diene monomer unit is too small, the rubber elasticity of the resulting crosslinked product may be lowered. Conversely, if the content is too large, heat resistance and chemical stability may be impaired.

  Moreover, since the carboxyl group-containing nitrile rubber (A) used in the present invention has the effects of the present invention more remarkably, the above α, β-ethylenically unsaturated nitrile monomer unit, carboxyl group-containing monomer In addition to the unit and the conjugated diene monomer unit, it is preferable to further contain an α, β-ethylenically unsaturated monocarboxylic acid ester monomer unit.

  The α, β-ethylenically unsaturated monocarboxylic acid ester monomer forming the α, β-ethylenically unsaturated monocarboxylic acid ester monomer includes methyl acrylate, ethyl acrylate, n-butyl acrylate, (Meth) acrylic acid esters having 1 to 18 carbon atoms such as isobutyl acrylate, n-dodecyl acrylate, methyl methacrylate, ethyl methacrylate, etc. (abbreviations for “methacrylic acid esters and acrylic acid esters”; .); (Meth) acrylic acid ester having a C2-C12 alkoxyalkyl group such as methoxymethyl acrylate, methoxyethyl methacrylate; carbon such as α-cyanoethyl acrylate, α-cyanoethyl methacrylate, cyanobutyl methacrylate, etc. (Meth) having a cyanoalkyl group of 2 to 12 (Meth) acrylic acid ester having a C1-C12 hydroxyalkyl group such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl acrylate, etc .; trifluoroethyl acrylate, (Meth) acrylic acid ester having a C1-C12 fluoroalkyl group such as tetrafluoropropyl methacrylate; and the like. However, since the effect of the present invention becomes more prominent, C1-C18 alkyl (Meth) acrylic acid ester having a group is preferred, (meth) acrylic acid ester having an alkyl group having 1 to 10 carbon atoms is more preferred, and n-butyl acrylate is particularly preferred. These may be used alone or in combination.

  The content of the α, β-ethylenically unsaturated monocarboxylic acid ester monomer unit is preferably 5 to 60% by weight, more preferably 10 to 55% by weight, and still more preferably based on the total monomer units. 15 to 45% by weight. When the content of the α, β-ethylenically unsaturated monocarboxylic acid ester monomer unit is in the above range, the effect of the present invention becomes more remarkable.

  Further, the carboxyl group-containing nitrile rubber (A) used in the present invention is an α, β-ethylenically unsaturated nitrile monomer, a carboxyl group-containing monomer, a single amount of α, β-ethylenically unsaturated monocarboxylic acid ester. In addition to the monomer and the conjugated diene monomer, other monomers copolymerizable therewith may be copolymerized. Examples of such other monomers include ethylene, α-olefin monomers, aromatic vinyl monomers, and fluorine-containing vinyl monomers.

  The α-olefin monomer preferably has 3 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 fluorine-containing vinyl monomer include fluoroethyl vinyl ether, fluoropropyl vinyl ether, o-trifluoromethyl styrene, vinyl pentafluorobenzoate, difluoroethylene, and tetrafluoroethylene.

  These other copolymerizable monomers may be used in combination. 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 nitrile rubber (A) is 120 or less, preferably 60 or less, more preferably 40 or less, and particularly preferably 30 or less. If the iodine value of the carboxyl group-containing nitrile rubber (A) is too high, the heat resistance and ozone resistance of the resulting crosslinked product may be reduced.

The polymer Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the carboxyl group-containing nitrile rubber (A) is preferably 10 to 200, more preferably 15 to 150, still more preferably 15 to 100, and particularly preferably 30 to 70. If the polymer Mooney viscosity of the carboxyl group-containing nitrile rubber (A) is too low, the mechanical properties of the resulting crosslinked product may be reduced. Conversely, if it is too high, the processability of the rubber composition may be reduced. is there.

The carboxyl group content in the carboxyl group-containing nitrile rubber (A), that is, the number of moles of carboxyl groups per 100 g of the carboxyl group-containing nitrile rubber (A) is preferably 5 × 10 ^{−4 to} 5 × 10 ^−1. ephr, more preferably 1 × 10 ⁻³ to 1 × 10 ⁻¹ ephr, and particularly preferably 5 × 10 ^{−3 to} 6 × 10 ⁻² ephr. If the carboxyl group content of the carboxyl group-containing nitrile rubber (A) is too low, the mechanical strength of the resulting crosslinked product may be reduced, and if it is too high, cold resistance may be reduced.

  The method for producing the carboxyl group-containing nitrile rubber (A) of the present invention is not particularly limited, but a copolymer rubber latex is prepared by copolymerizing the above-mentioned monomers by emulsion polymerization using an emulsifier. It is preferable to produce by hydrogenation. 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 0.01 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 0.8 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 the carboxyl group containing nitrile rubber (A) can be manufactured by selectively hydrogenating the double bond of a conjugated diene monomer unit with respect to the obtained copolymer. 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.

Ethylene-vinyl alcohol copolymer (B)
In addition to the carboxyl group-containing nitrile rubber (A) described above, the rubber composition of the present invention comprises an ethylene-vinyl alcohol copolymer (B) (hereinafter simply referred to as “ethylene-”) having an ethylene content of 10 to 60 mol%. Vinyl alcohol copolymer (B) ").

  The ethylene-vinyl alcohol copolymer (B) used in the present invention is a copolymer having ethylene and vinyl alcohol as main structural units due to its structure, but is usually a copolymer of ethylene and a fatty acid vinyl ester. Is a copolymer obtained by partially or completely saponifying with an alkali catalyst or the like.

The ethylene content (molar ratio of ethylene units) of the ethylene-vinyl alcohol copolymer (B) is 10 to 60 mol%, preferably 15 to 55 mol%, more preferably 20 to 50 mol%. If the ethylene content is too small, the dispersibility of the ethylene-vinyl alcohol copolymer (B) in the carboxyl group-containing nitrile rubber (A) may be deteriorated. May decrease. The ethylene content in the ethylene-vinyl alcohol copolymer (B) can be determined by, for example, a nuclear magnetic resonance (H ¹ -NMR) method.

  The melting point of the ethylene-vinyl alcohol copolymer (B) is preferably 130 to 250 ° C, more preferably 140 to 240 ° C, and further preferably 150 to 230 ° C. If the melting point is too low, the heat resistance of the crosslinked product may be reduced. On the other hand, if the melting point is too high, the dispersibility of the ethylene-vinyl alcohol copolymer (B) in the carboxyl group-containing nitrile rubber (A) is deteriorated. There is a fear.

  The melt index (210 ° C., load 2.16 kg) of the ethylene-vinyl alcohol copolymer (B) is preferably 0.1 to 40 g / 10 min, more preferably 0.5 to 35 g / 10 min, and still more preferably. 1 to 30 g / 10 min. If the melt index is too low, the dispersibility of the ethylene-vinyl alcohol copolymer (B) in the carboxyl group-containing nitrile rubber (A) may be deteriorated. On the other hand, if the melt index is too high, the mechanical properties of the crosslinked product may be reduced. May decrease.

  Further, the degree of saponification of the vinyl ester portion of the ethylene-vinyl alcohol copolymer (B) (having a vinyl alcohol structure relative to the total of the monomer unit portion having a vinyl alcohol structure and the monomer unit portion having a vinyl ester structure) The ratio of the monomer unit portion) is preferably 90 mol% or more, more preferably 95 mol% or more, and still more preferably 97% or more. If the degree of saponification is too low, the oil resistance of the crosslinked product tends to decrease.

  The content of the ethylene-vinyl alcohol copolymer (B) with respect to 100 parts by weight of the carboxyl group-containing nitrile rubber (A) in the rubber composition of the present invention is preferably 5 to 100 parts by weight, more preferably 5 to 85 parts. Part by weight, particularly preferably 5 to 70 parts by weight. If the content ratio of the ethylene-vinyl alcohol copolymer (B) in the rubber composition is too small, the oil resistance and mechanical properties of the resulting cross-linked product may be deteriorated. There exists a possibility that the compression set resistance and cold resistance of a crosslinked material may fall.

The rubber composition of the present invention can be prepared by kneading the carboxyl group-containing nitrile rubber (A) and the ethylene-vinyl alcohol copolymer (B), preferably in the above weight ratio. it can. In addition, when kneading the carboxyl group-containing nitrile rubber (A) and the ethylene-vinyl alcohol copolymer (B), the kneading may be performed at a temperature equal to or higher than the melting point of the ethylene-vinyl alcohol copolymer (B). Preferably, it is more preferable to knead at a temperature in the range of 5 ° C. or more higher than the melting point of the ethylene-vinyl alcohol copolymer (B), and in the range of 10 to 100 ° C. higher than the melting point of the ethylene-vinyl alcohol copolymer (B). It is particularly preferable to knead at a temperature.
By kneading at a temperature equal to or higher than the melting point of the ethylene-vinyl alcohol copolymer (B), the dispersibility of the carboxyl group-containing nitrile rubber (A) and the ethylene-vinyl alcohol copolymer (B) is improved, and a crosslinked product is obtained. Improved mechanical properties.

Crosslinkable rubber composition The crosslinkable rubber composition of the present invention comprises a rubber composition containing the carboxyl group-containing nitrile rubber (A) and the ethylene-vinyl alcohol copolymer (B) described above, and a polyamine-based crosslinking agent. It contains. By using a polyamine-based crosslinking agent as the crosslinking agent, the compression set resistance of the resulting crosslinked product can be further increased.

The polyamine-based crosslinking agent 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 aromatic 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 the form of the compound at the time of crosslinking Is 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. Of these, hexamethylenediamine carbamate is particularly preferable.

  The compounding amount of the polyamine-based crosslinking agent in the crosslinkable rubber composition of the present invention is preferably 0.1 to 20 parts by weight, more preferably 100 parts by weight of the carboxyl group-containing nitrile rubber (A). The amount is 0.2 to 15 parts by weight, more preferably 0.5 to 10 parts by weight. If the blending amount of the polyamine-based crosslinking agent is too small, the mechanical properties and compression set resistance of the resulting crosslinked product may be deteriorated. On the other hand, if the amount is too large, the fatigue resistance of the resulting crosslinked product may be deteriorated.

  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-ethylimi Sol, 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-heptyluimidazoline, 1-methyl-2-undecylimidazoline, 1-methyl-2-heptadecylimidazoline, 1-methyl-2-ethoxymethylimidazoline , Basic crosslinking accelerators having a cyclic amidine structure such as 1-ethoxymethyl-2-methylimidazoline; guanidines such as tetramethylguanidine, tetraethylguanidine, diphenylguanidine, 1,3-di-ortho-tolylguanidine, orthotolylbiguanide And basic crosslinking accelerators; aldehyde amine basic crosslinking accelerators such as n-butyraldehyde aniline and acetaldehyde ammonia; Of these, basic crosslinking accelerators having a cyclic amidine structure are preferred, and 1,8-diazabicyclo [5,4,0] undecene-7 and 1,5-diazabicyclo [4,3,0] nonene-5 are preferred. More preferred is 1,8-diazabicyclo [5,4,0] undecene-7. 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 and more preferably 100 parts by weight of the carboxyl group-containing nitrile rubber (A). Is 0.2 to 15 parts by weight, more preferably 0.5 to 10 parts by weight. 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 to the above, the crosslinkable rubber composition of the present invention includes compounding agents usually used in the rubber field, for example, reinforcing fillers such as carbon black and silica, and non-reinforcing fillers such as calcium carbonate and clay. Materials, crosslinking accelerators other than basic crosslinking accelerators, crosslinking assistants, crosslinking retarders, antioxidants, antioxidants, light stabilizers, scorch inhibitors such as primary amines, silane coupling agents, plasticizers, processing Auxiliaries, lubricants, adhesives, lubricants, flame retardants, antifungal agents, acid acceptors, antistatic agents, pigments and the like can be blended. The compounding amount of these compounding agents is not particularly limited as long as it does not impair the object and effect of the present invention, and an amount corresponding to the compounding purpose can be blended.

  The crosslinkable rubber composition of the present invention is blended with a polymer other than the carboxyl group-containing nitrile rubber (A) and the ethylene-vinyl alcohol copolymer (B) as long as the effects of the present invention are not impaired. May be. Other polymers include acrylic rubber, ethylene-acrylic acid copolymer rubber, fluorine rubber, styrene-butadiene copolymer rubber, ethylene-propylene copolymer rubber, ethylene-propylene-diene terpolymer rubber, Examples thereof include natural rubber and polyisoprene rubber. The blending amount in the crosslinkable rubber composition when blending other polymers is preferably 30 parts by weight or less, more preferably 20 parts by weight with respect to 100 parts by weight of the carboxyl group-containing nitrile rubber (A). Part or less, more preferably 10 parts by weight or less.

Preparation of Rubber Composition and Crosslinkable Rubber Composition The method for adjusting the rubber composition of the present invention is not particularly limited, but the carboxyl group-containing nitrile rubber (A) and the ethylene-vinyl alcohol copolymer (B) are mixed.

  The mixing method is not particularly limited, but may be mixed (dry blended) in a non-aqueous system, a solution system (a state dissolved or dispersed in a solution) or an aqueous system (a state dispersed in water). It may be mixed in a latex state). When mixed in a solution system and an aqueous system, the rubber composition can be obtained in the form of crumb by coagulation by a conventionally known method, followed by filtration and drying.

  Further, when the carboxyl group-containing nitrile rubber (A) and the ethylene-vinyl alcohol copolymer (B) are mixed, various compounding agents such as an anti-aging agent and other rubbers may be mixed simultaneously.

  In order to improve the dispersibility of the ethylene-vinyl alcohol copolymer (B) in the carboxyl group-containing nitrile rubber (A), the rubber composition obtained by mixing is an ethylene-vinyl alcohol copolymer as described above. It is preferable to knead at a temperature equal to or higher than the melting point of (B).

  The kneading method is not particularly limited, but extruders such as single screw extruders and twin screw extruders; closed kneaders such as kneaders, Banbury mixers, Brabender mixers, internal mixers, kneaders; kneading rolls; It is preferable to heat while kneading with a machine.

  The method for preparing the crosslinkable rubber composition of the present invention is not particularly limited, but each component except the crosslinker and the heat-labile crosslinking aid is added to the rubber composition of the present invention obtained as described above. Is preferably 10 to 200 ° C, more preferably 20 to 170 ° C, and kneaded with a mixer such as a Banbury mixer, Brabender mixer, intermixer, kneader, etc., and transferred to a roll or the like to be unstable to a crosslinking agent or heat. It is possible to prepare the mixture by secondary kneading, preferably at a temperature of 10 to 80 ° C. with the addition of a crosslinking aid.

The crosslinkable rubber composition of the present invention thus obtained has a compound Mooney viscosity [ML _{1 + 4} , 100 ° C.], preferably 10 to 200, more preferably 15 to 180, still more preferably 20 to 150, Excellent workability.

Cross-linked product The cross-linked product of the present invention is obtained by cross-linking the cross-linkable rubber composition of the present invention described above.
The cross-linked product of the present invention uses the cross-linkable rubber composition of the present invention, for example, is molded by a molding machine corresponding to a desired shape, such as an extruder, an injection molding machine, a compressor, a roll, and heated. Can be produced by carrying out a crosslinking reaction and fixing the shape as a crosslinked product. 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 200 ° C., preferably 130 to 190 ° C., and the crosslinking time is usually 1 minute to 24 hours, preferably 2 minutes to 6 hours.

  Depending on the shape and size of the 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 cross-linked product of the present invention thus obtained is obtained by cross-linking the cross-linkable rubber composition of the present invention described above, and therefore has excellent mechanical properties, oil resistance, and compression set resistance. It is.

  For this reason, the cross-linked product of the present invention includes O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, well head seals, pneumatic equipment seals, air conditioner cooling devices, and air conditioner refrigerator compressors. Seals for fluorocarbons or fluorohydrocarbons or carbon dioxide used for cleaning, supercritical or subcritical carbon dioxide sealing seals used for precision cleaning media, rolling devices (rolling bearings, automotive hubs) Various sealants such as seals for units, water pumps for automobiles, linear guide devices and ball screws, valves and valve seats, BOP (Blow Out Preventar), platters, etc .; are attached to the connecting part of intake manifold and cylinder head Intake manifold , Cylinder head gasket attached to the connecting part between the cylinder block and cylinder head, rocker cover gasket attached to the connecting part between the rocker cover and cylinder head, attached to the connecting part between the oil pan and the cylinder block or transmission case Various types of gaskets, such as a fuel cell separator gasket, a hard disk drive top cover gasket, and the like, which are mounted between a pair of housings sandwiching a unit cell having an oil pan gasket, a positive electrode, an electrolyte plate and a negative electrode; Rolls, paper rolls, industrial rolls, office machine rolls, flat belts (film core flat belts, cord flat belts, laminated flat belts, single flat belts, etc.), V belts (wrapped V belts) , Low edge V Belt) (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, oil-in-belt, etc. Various belts; 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; 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, automobile interior parts, tires, coated cables, shoe soles, electromagnetic shielding, adhesives for flexible printed circuit boards, fuel cell separators, cosmetics, In addition, it can be used in a wide range of applications such as pharmaceutical fields, food contact fields, and electronics fields. Among these, the crosslinked product of the present invention can be suitably used as a belt, a hose or a sealing material, and is particularly suitable as a sealing material.

  The present invention will be specifically described below with reference to examples and comparative examples. In the following, “parts” are based on weight unless otherwise specified. The test and evaluation were as follows.

By adding 20 ml of ethanol and 10 ml of water to 0.2 g of nitrile rubber having a carboxyl group content of 2 mm square, and using a 0.02N aqueous ethanol solution of potassium hydroxide with stirring, titration with thymolphthalein as an indicator at room temperature It was determined as the number of moles of carboxyl groups relative to 100 g of nitrile rubber (unit: ephr).

The iodine value of the highly saturated copolymer rubber containing the iodine value nitrile group was measured according to JIS K 6235.

Mooney viscosity (Polymer Mooney)
The Mooney viscosity (polymer Mooney) of the nitrile group-containing highly saturated copolymer rubber was measured according to JIS K6300-1 (unit: [ML _{1 + 4} , 100 ° C.]).

Normal physical properties (tensile strength, elongation, hardness)
The crosslinkable rubber composition was put into a mold having a length of 15 cm, a width of 15 cm, and a depth of 0.2 cm, and press-molded at 170 ° C. for 20 minutes while being pressed at a press pressure of 10 MPa to obtain a sheet-like cross-linked product. Next, the obtained cross-linked product was transferred to a gear-type oven and subjected to secondary cross-linking at 170 ° C. for 4 hours, and the obtained sheet-like cross-linked product was punched with a No. 3 dumbbell to prepare a test piece. And using this obtained test piece, according to JIS K6251, the tensile strength and elongation of the cross-linked product, and according to JIS K6253, the hardness of the cross-linked product using a durometer hardness tester (type A). Were measured respectively.

Oil-resistant immersion test A cross-linked product similar to the cross-linked product used in the evaluation of the above-mentioned normal physical properties was prepared. It was immersed in oil (Fuel-C). And about the crosslinked material immersed in fuel oil, oil resistance was evaluated by measuring the rate of change (unit:%) of the volume before and behind immersion. It can be judged that the smaller the value of the volume change rate before and after the immersion, the smaller the degree of swelling by the fuel oil and the better the oil resistance.

Cold resistance test (TR test)
A cross-linked product similar to the cross-linked product used in the evaluation of the normal physical properties was prepared, and the cold resistance of the cross-linked product was measured by a TR test (low temperature elastic recovery test) according to JIS K6261. It can be judged that the lower the TR10 (unit: ° C), the better the cold resistance.

Compression set (O-ring compression set)
Using a mold having an inner diameter of 30 mm 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 to form an O-ring shape. The 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 compression set (O-ring compression set) was measured in accordance with JIS K6262. The smaller this value, the better the compression set resistance.

Example 1
In a reactor, 180 parts of ion-exchanged water, 25 parts of a 10% strength sodium dodecylbenzenesulfonate aqueous solution, 20 parts of acrylonitrile, 34 parts of n-butyl acrylate, 6 parts of mono-n-butyl maleate, t-dodecyl mercaptan (molecular weight) Adjuster) In the order of 0.5 parts, the internal gas was replaced with nitrogen three times, and then 40 parts of 1,3-butadiene was charged. The reactor 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 stirring in the reactor. After the polymerization reaction, 0.1 part of a 10% by weight hydroquinone aqueous solution (polymerization terminator) is added to stop the polymerization reaction, and then the residual monomer is removed using a rotary evaporator at a water temperature of 60 ° C. Thus, a polymer latex (solid content concentration of 30% by weight) having 20% by weight of acrylonitrile units, 40% by weight of butadiene units, 35% by weight of n-butyl acrylate units, and 5% by weight of mono-n-butyl maleate units was obtained. The polymer composition was measured by ¹ H-NMR.

  Next, the latex prepared above and the palladium catalyst (1 wt% palladium acetate acetone) were placed in an autoclave so that the palladium content relative to the dry weight of the rubber contained in the latex obtained above was 1,000 ppm. Then, a hydrogenation reaction was performed at a hydrogen pressure of 3 MPa and a temperature of 50 ° C. for 6 hours.

The obtained latex was coagulated by adding 2 volumes of methanol, and then vacuum-dried at 60 ° C. for 12 hours to obtain a carboxyl group-containing nitrile rubber (A1). The obtained carboxyl group-containing nitrile rubber (A1) had a carboxyl group content of 2.9 × 10 ⁻² ephr, an iodine value of 7, and a polymer Mooney viscosity [ML _{1 + 4} , 100 ° C.] of 45. The resulting carboxyl group-containing nitrile rubber (A1) was composed of 20% by weight of acrylonitrile units, 40% by weight of butadiene units (including hydrogenated portions), 35% by weight of n-butyl acrylate units, and mono-maleic acid monon. -It was 5 weight% of butyl units.

Then, using a Brabender mixer, 90 parts of the carboxyl group-containing nitrile rubber (A1) obtained above was added to an ethylene-vinyl alcohol copolymer (B1) (product name: Soarnol DC3203, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.). 10 parts of ethylene content: 32 mol%, melt index: 3.8 g / 10 min, melting point: 183 ° C.) were kneaded at a temperature of 210 ° C. for 10 minutes to obtain a rubber composition.
Subsequently, 100 parts of the obtained rubber composition, MT carbon (trade name: Thermax MT, manufactured by Engineer Carbons, carbon black) 40 parts, trimellitic acid tri-2-ethylhexyl (trade name: ADK Cizer C-8, 5 parts by ADEKA, plasticizer, 1 part stearic acid (processing aid), and 4,4′-di- (α, α′-dimethylbenzyl) diphenylamine (trade name: Naugard 445, manufactured by Chemtura, 1.5 parts of an anti-aging agent) was added and kneaded at a temperature of 110 ° C. Next, the obtained mixture was transferred to a roll having a temperature of 40 ° C., and DBU (trade name: RHENOGRAN XLA-60 (GE2014), manufactured by Rhein Chemie, DBU 60% (zinc dialkyl diphosphate salt portion). And 4 parts of a basic cross-linking accelerator) and a hexamethylenediamine carbamate (trade name: Diak # 1, manufactured by DuPont Dow Elastomer Co., Ltd., polyamine-based cross-linking agent) ) 1.7 parts was added and kneaded to prepare a crosslinkable rubber composition.

  And by the above-mentioned method, a crosslinked product was obtained using the crosslinkable rubber composition prepared above, and the obtained crosslinked product was subjected to evaluation and testing of normal physical properties, oil resistance immersion test, and compression set. went. The results are shown in Table 1.

Example 2
The blending amount of the carboxyl group-containing nitrile rubber (A1) is from 90 parts to 80 parts, the blending amount of the ethylene-vinyl alcohol copolymer (B1) is from 10 parts to 20 parts, and the blending amount of hexamethylenediamine carbamate is 1. A crosslinkable rubber composition was obtained and evaluated in the same manner as in Example 1, except that the amount was changed from 7 parts to 1.5 parts. The results are shown in Table 1.

Example 3
The blending amount of the carboxyl group-containing nitrile rubber (A1) is changed from 90 parts to 70 parts, the blending amount of the ethylene-vinyl alcohol copolymer (B1) is changed from 10 parts to 30 parts, and the blending quantity of hexamethylenediamine carbamate is 1. A crosslinkable rubber composition was obtained and evaluated in the same manner as in Example 1 except that the content was changed from 7 parts to 1.3 parts. The results are shown in Table 1.

Example 4
Ethylene-vinyl alcohol copolymer (B1) is converted to ethylene-vinyl alcohol copolymer (B2) (trade name: EVAL G156B, manufactured by Kuraray Co., Ltd., ethylene content: 48 mol%, melt index: 15 g / 10 min, melting point: 160 The crosslinkable rubber composition was obtained and evaluated in the same manner as in Example 1 except that the kneading temperature of (A1) and (B2) was changed to 185 ° C. The results are shown in Table 1.

Example 5
The blending amount of the carboxyl group-containing nitrile rubber (A1) is from 90 parts to 70 parts, the blending amount of the ethylene-vinyl alcohol copolymer (B2) is from 10 parts to 30 parts, and the blending amount of hexamethylenediamine carbamate is 1. A crosslinkable rubber composition was obtained and evaluated in the same manner as in Example 4 except that the amount was changed from 7 parts to 1.3 parts. The results are shown in Table 1.

Example 6
In the production of the carboxyl group-containing nitrile rubber (A1), Example 1 was used except that the acrylonitrile charge was changed to 37 parts, the mono-n-butyl maleate charge was changed to 6 parts, and the 1,3-butadiene charge was changed to 57 parts. Similarly, a carboxyl group-containing nitrile rubber (A2) was obtained. The obtained carboxyl group-containing nitrile rubber (A2) had a carboxyl group content of 3.1 × 10 ⁻² ephr, an iodine value of 7, and a polymer Mooney viscosity [ML _{1 + 4} , 100 ° C.] of 45. Further, the obtained carboxyl group-containing nitrile rubber (A2) was 36% by weight of acrylonitrile units, 59% by weight of butadiene units (including hydrogenated portions), and 5% by weight of mono n-butyl maleate units.
The same procedure as in Example 1 except that the carboxyl group-containing nitrile rubber (A1) was changed to the carboxyl group-containing nitrile rubber (A2) and the amount of hexamethylenediamine carbamate was changed from 1.7 parts to 2.4 parts. Thus, a crosslinkable rubber composition was obtained and evaluated in the same manner. The results are shown in Table 1.

Example 7
The same procedure as in Example 5 except that the carboxyl group-containing nitrile rubber (A1) was changed to the carboxyl group-containing nitrile rubber (A2), and the amount of hexamethylenediamine carbamate was changed from 1.3 parts to 1.8 parts. Thus, a crosslinkable rubber composition was obtained and evaluated in the same manner. The results are shown in Table 1.

Comparative Example 1
While not containing an ethylene-vinyl alcohol copolymer, the amount of carboxyl group-containing nitrile rubber (A1) is changed from 90 parts to 100 parts, and the amount of hexamethylenediamine carbamate is changed from 1.7 parts to 1.9 parts. Except for each change, 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
A nitrile rubber containing no carboxyl group (A3) in the same manner as in Example 1 except that the monomer used for polymerization was changed to 20 parts of acrylonitrile, 34 parts of n-butyl acrylate, and 46 parts of 1,3-butadiene. ) The resulting nitrile rubber (A3) had an iodine value of 8 and a polymer Mooney viscosity [ML _{1 + 4} , 100 ° C.] of 54. Further, the obtained nitrile rubber (A3) was 20% by weight of acrylonitrile units, 47% by weight of butadiene units (including hydrogenated portions), and 33% by weight of n-butyl acrylate units.

  Then, 90 parts of the nitrile rubber (A3) obtained above is used in place of 90 parts of the carboxyl group-containing nitrile rubber (A1), and 1,3-bis is substituted in place of 1.7 parts of hexamethylenediamine carbamate. Example 1 except that 9 parts of (t-butylperoxyisopropyl) benzene (organic peroxide crosslinking agent) 40% product (trade name: Vul Cup 40KE, manufactured by GEO Specialty Chemicals Inc) was used and DBU was not used. Similarly, a crosslinkable rubber composition was obtained and evaluated in the same manner. The results are shown in Table 1.

Comparative Example 3
The amount of nitrile rubber (A3) is changed from 90 parts to 70 parts, the amount of ethylene-vinyl alcohol copolymer (B1) is changed from 10 parts to 30 parts, and 1,3-bis (t-butylperoxyisopropyl) benzene. A crosslinkable rubber composition was obtained and evaluated in the same manner as in Comparative Example 2 except that the blending amount of was changed from 9 parts to 7 parts. The results are shown in Table 1.

Comparative Example 4
A nitrile rubber (A4) containing no carboxyl group was obtained in the same manner as in Example 1 except that the monomer used for the polymerization was changed to 37 parts of acrylonitrile and 63 parts of 1,3-butadiene. The obtained nitrile rubber (A4) had an iodine value of 7, and a polymer Mooney viscosity [ML _{1 + 4} , 100 ° C.] of 55. The obtained nitrile rubber (A4) was 36% acrylonitrile units and 64% butadiene units (including hydrogenated portions).
A crosslinkable rubber composition was obtained in the same manner as in Comparative Example 2 except that 90 parts of the nitrile rubber (A4) obtained above was used instead of 90 parts of the carboxyl group-containing nitrile rubber (A3). In the same manner, the evaluation was performed. The results are shown in Table 1.

Comparative Example 5
The amount of nitrile rubber (A4) is changed from 90 parts to 70 parts, the amount of ethylene-vinyl alcohol copolymer (B1) is changed from 10 parts to 30 parts, and 1,3-bis (t-butylperoxyisopropyl) benzene. A crosslinkable rubber composition was obtained and evaluated in the same manner as in Comparative Example 4 except that the blending amount was changed from 9 parts to 7 parts. The results are shown in Table 1.

  From Table 1, crosslinking obtained by using a rubber composition obtained by blending an ethylene-vinyl alcohol copolymer having an ethylene content of 10 to 60 mol% with the carboxyl group-containing nitrile rubber (A1) or (A2). The product was excellent in mechanical properties, oil resistance, cold resistance and compression set resistance (Examples 1 to 7).

On the other hand, when an ethylene-vinyl alcohol copolymer having an ethylene content of 10 to 60 mol% was not blended, the tensile strength and the oil resistance were inferior (Comparative Example 1).
Furthermore, when the nitrile rubber (A3) containing no carboxyl group was used as the nitrile rubber, the tensile strength and the compression set resistance were inferior (Comparative Example 2). Moreover, when the nitrile rubber (A4) which does not contain a carboxyl group was used as a nitrile rubber, it resulted in inferior compression set resistance (Comparative Example 4).
When the nitrile rubber (A3) or (A4) not containing a carboxyl group is used and the same amount of ethylene-vinyl alcohol copolymer is blended as in Example 3, the foamed crosslinked product is severely foamed and cannot be evaluated. (Comparative Examples 3 and 5).

Claims (6)

It contains 5 to 60% by weight of α, β-ethylenically unsaturated nitrile monomer unit, 0.1 to 20% by weight of carboxyl group-containing monomer unit and 15 to 89.9% by weight of conjugated diene monomer unit. , For 100 parts by weight of the carboxyl group-containing nitrile rubber (A) having an iodine value of 120 or less,
A rubber composition comprising 5 to 100 parts by weight of an ethylene-vinyl alcohol copolymer (B) having an ethylene content of 10 to 60 mol%. The carboxyl group-containing nitrile rubber (A) is an α, β-ethylenically unsaturated nitrile monomer unit of 5 to 60% by weight, a carboxyl group-containing monomer unit of 0.1 to 20% by weight, a conjugated diene monomer. The unit according to claim 1, comprising 15 to 89.9% by weight of units and 5 to 60% by weight of α, β-ethylenically unsaturated monocarboxylic acid ester monomer units, and having an iodine value of 120 or less. The rubber composition as described.   A crosslinkable rubber composition comprising the rubber composition according to claim 1 or 2 and a polyamine crosslinking agent.   A crosslinked product obtained by crosslinking the crosslinkable rubber composition according to claim 3.   The cross-linked product according to claim 4, which is a rubber member for sealing, a belt, a hose or a gasket.   The carboxyl group-containing nitrile rubber (A) and the ethylene-vinyl alcohol copolymer (B) are kneaded at a temperature equal to or higher than the melting point of the ethylene-vinyl alcohol copolymer (B). Item 2. A method for producing a rubber composition according to Item 1.