JPWO2009051102A1 - Crosslinkable nitrile rubber composition and rubber cross-linked product - Google Patents

Abstract

a highly saturated nitrile rubber (a) having an α, β-ethylenically unsaturated nitrile monomer unit and an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit and having an iodine value of 120 or less; A crosslinkable nitrile rubber composition comprising a metal compound (b) selected from CaO, Ca (OH) 2 and Al (OH) 3 and a polyamine crosslinking agent (c) is provided. According to the present invention, a crosslinkable nitrile rubber composition that gives a rubber cross-linked product having a small compression set and excellent heat resistance (heat aging resistance), and a rubber cross-linked product obtained using the cross-linkable nitrile rubber composition Can be provided.

Description

  The present invention relates to a crosslinkable nitrile rubber composition that gives a rubber cross-linked product having a small compression set and excellent heat resistance.

  Conventionally, a nitrile group-containing highly saturated copolymer rubber (also referred to as “highly saturated nitrile rubber”, which includes hydrogenated nitrile rubber) is known as a rubber excellent in oil resistance, heat resistance and ozone resistance. The rubber cross-linked product is used for various automotive rubber products such as belts, hoses, gaskets, packings and oil seals. However, with the miniaturization and higher output of automobile engines, rubber materials with even better heat resistance have been demanded. Further, when highly saturated nitrile rubber is used for sealing, further reduction in compression set is necessary.

For this situation, Patent Document 1 discloses a crosslinkable rubber composition containing a highly saturated nitrile rubber having an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit, a polyamine crosslinking agent, and a basic crosslinking accelerator. Proposing things. Although a rubber cross-linked product having improved heat resistance and compression set can be obtained by the composition, it has been required to further improve heat resistance while maintaining the compression set in a good state.
Japanese Patent Laid-Open No. 2001-55471 (US6657014B1)

  An object of the present invention is to provide a crosslinkable nitrile rubber composition which gives a rubber cross-linked product having a small compression set and excellent heat resistance (heat aging resistance), and a rubber cross-linked product obtained using the cross-linkable nitrile rubber composition Is to provide.

  As a result of diligent research to solve the above-mentioned problems, the present inventors have found that the above object can be achieved by blending a specific metal compound with a specific highly saturated nitrile rubber and crosslinking with a specific cross-linking agent. The headline and the present invention have been completed.

Thus, according to the present invention,
(1) A highly saturated nitrile rubber having an α, β-ethylenically unsaturated nitrile monomer unit and an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit and having an iodine value of 120 or less (a ), A metal compound (b) selected from CaO, Ca (OH) ₂ and Al (OH) _3, and a polyamine crosslinking agent (c),
(2) The crosslinkable nitrile rubber composition as described above, wherein the metal compound (b) is a calcium compound (e) selected from CaO and Ca (OH) ₂ .
(3) The crosslinkable nitrile rubber composition as described above, wherein the content ratio of the metal compound (b) is 0.1 to 200 parts by weight with respect to 100 parts by weight of the highly saturated nitrile rubber (a),
(4) The crosslinkable nitrile rubber composition as described above, wherein the polyamine crosslinking agent (c) is hexamethylenediamine carbamate.
(5) the high amount of the carboxyl groups of the saturated nitrile rubber (a) is, 5 × ¹⁰ -4 ~5 × above cross-linkable nitrile rubber composition wherein the ¹⁰ -1 ephr,
(6) The crosslinkable nitrile rubber composition as described above, further comprising a basic crosslinking accelerator (d),
(7) The crosslinkable nitrile rubber composition as described above, further comprising carbon black and / or silica,
(8) A crosslinked rubber product obtained by crosslinking the crosslinkable nitrile rubber composition described above,
(9) The rubber cross-linked product as described above, which is a belt or a sealing material,
Is provided.

  According to the present invention, there is provided a crosslinkable nitrile rubber composition which gives a rubber cross-linked product having a small compression set and excellent heat resistance.

The crosslinkable nitrile rubber composition of the present invention has an α, β-ethylenically unsaturated nitrile monomer unit and an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit, and an iodine value of 120 or less. A highly saturated nitrile rubber (a), a metal compound (b) selected from CaO, Ca (OH) ₂ and Al (OH) _3, and a polyamine crosslinking agent (c). .

  Α, β-ethylenically unsaturated nitrile monomer forming the α, β-ethylenically unsaturated nitrile monomer unit of the highly saturated nitrile rubber (a) (hereinafter referred to as “α, β-ethylenically unsaturated nitrile”) Is not limited as long as it is an α, β-ethylenically unsaturated compound having a nitrile group. Acrylonitrile; α-halogenoacrylonitrile such as α-chloroacrylonitrile and α-bromoacrylonitrile; methacrylonitrile Α-alkyl acrylonitrile such as; Among these, acrylonitrile and methacrylonitrile are preferable. These α, β-ethylenically unsaturated nitriles may be used in combination.

  The content of the α, β-ethylenically unsaturated nitrile monomer unit in the highly saturated nitrile rubber (a) is preferably 10 to 60% by weight, more preferably 15 to 55% by weight, particularly preferably 20 to 50% by weight. %. If the content of the α, β-ethylenically unsaturated nitrile monomer unit is too small, the oil resistance of the rubber cross-linked product may be lowered. Conversely, if the content is too large, the cold resistance may be lowered.

  The α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit forming the α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit of the highly saturated nitrile rubber (a) is free of crosslinking. It has one carboxyl group. By having an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit, the resulting rubber cross-linked product has excellent tensile stress.

  The organic group bonded to the carbonyl group through an oxygen atom in the ester part of the α, β-ethylenically unsaturated dicarboxylic acid monoester monomer is preferably an alkyl group, a cycloalkyl group or an alkylcycloalkyl group, The group is particularly preferred. In this case, the alkyl group preferably has 1 to 10 carbon atoms, more preferably 2 to 6 carbon atoms, and the cycloalkyl group preferably has 5 to 12 carbon atoms, more preferably 6 to 10 carbon atoms. The number of carbon atoms in the group is preferably 6-12, more preferably 7-10. If the carbon number of the organic group is too small, the processing stability of the crosslinkable nitrile rubber composition may be reduced. Conversely, if the carbon number is too large, the crosslinking speed may be slowed down or the mechanical properties of the rubber crosslinked product may be reduced. May be reduced.

Examples of α, β-ethylenically unsaturated dicarboxylic acid monoester monomers include monoalkyl maleates such as monomethyl maleate, monoethyl maleate, monopropyl maleate, mono n-butyl maleate; Maleic acid monocycloalkyl esters such as cyclopentyl, monocyclohexyl maleate and monocycloheptyl maleate; monoalkyl cyclomaleates such as monomethylcyclopentyl maleate and monoethylcyclohexyl maleate; monomethyl fumarate, monoethyl fumarate, fumarate Fumaric acid monoalkyl esters such as monopropyl acid and mono-n-butyl fumarate; fumaric acid such as monocyclopentyl fumarate, monocyclohexyl fumarate and monocycloheptyl fumarate Monocycloalkyl esters; monoalkyl cycloalkyl esters of fumaric acid such as monomethylcyclopentyl fumarate and monoethylcyclohexyl fumarate; monoalkyl citraconic acids such as monomethyl citraconic acid, monoethyl citraconic acid, monopropyl citraconic acid and mono n-butyl citraconic acid Ester; citraconic acid monocycloalkyl ester such as citraconic acid monocyclopentyl, citraconic acid monocyclohexyl, citraconic acid monocycloheptyl; citraconic acid monomethylcyclopentyl, citraconic acid monoethylcyclohexyl citraconic acid monoalkyl cycloalkyl ester; Monoethyl itaconate such as monoethyl itaconate, monopropyl itaconate, mono-n-butyl itaconate Kill ester; itaconic acid monocyclopentyl, itaconic acid monocyclohexyl, itaconic acid monocycloheptyl, etc. itaconic acid monocycloalkyl ester; itaconic acid monomethylcyclopentyl, itaconic acid monoethylcyclohexyl etc., etc. It is done.
Among these, monopropyl maleate, mono n-butyl maleate, monopropyl fumarate, mono n-butyl fumarate, monopropyl citraconic acid, mono n citraconic acid in that the effect of the present invention appears more remarkably. -Monoesters of dicarboxylic acids having a carboxyl group at each of the two carbon atoms forming an α, β-ethylenically unsaturated bond such as butyl are preferred, such as mono n-butyl maleate, monopropyl citraconic acid, etc. A monoester of a dicarboxylic acid having two carboxyl groups in the cis position (cis configuration) is more preferred, and mono-n-butyl maleate is particularly preferred.

  The content of the α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit in the highly saturated nitrile rubber (a) is preferably 0.1 to 20% by weight, more preferably 0.2 to 15% by weight, Particularly preferred is 0.5 to 10% by weight. If the content of the α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit is too small, the tensile stress of the rubber cross-linked product may be reduced. On the other hand, if the content is too high, the scorch of the cross-linkable nitrile rubber composition may be reduced. There is a possibility that the stability deteriorates and the bending fatigue resistance of the rubber cross-linked product decreases.

  The highly saturated nitrile rubber (a) includes a rubber cross-linked product other than the above α, β-ethylenically unsaturated nitrile monomer unit and α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit. In order to retain elasticity, it usually has a diene monomer unit and / or an α-olefin monomer unit.

  Examples of the diene monomer forming the diene monomer unit include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and the like having 4 or more carbon atoms. Conjugated diene monomers: Non-conjugated diene monomers having preferably 5 to 12 carbon atoms such as 1,4-pentadiene and 1,4-hexadiene are exemplified. Among these, a conjugated diene monomer is preferable, and 1,3-butadiene is more preferable.

  The α-olefin monomer forming the α-olefin monomer unit is preferably one having 2 to 12 carbon atoms, ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1- Examples include hexene and 1-octene.

  The content of the diene monomer unit and / or α-olefin monomer unit in the highly saturated nitrile rubber (a) is preferably 20 to 89.9% by weight, more preferably 30 to 84.8% by weight, particularly Preferably it is 40-79.5 weight%. If the content is too small, the rubber elasticity of the rubber cross-linked product may be reduced. Conversely, if the content is too high, the heat resistance and chemical stability of the rubber cross-linked product may be impaired.

  The highly saturated nitrile rubber (a) also contains α, β-ethylenically unsaturated nitrile monomer, α, β-ethylenically unsaturated dicarboxylic acid monoester monomer, and diene monomer and / or α. -It may contain units of other monomers copolymerizable with olefin monomers. Such other copolymerizable monomers include α, β-ethylenically unsaturated carboxylic acid ester monomers other than α, β-ethylenically unsaturated dicarboxylic acid monoester monomers, α, β -Ethylenically unsaturated monocarboxylic acid monomer, α, β-ethylenically unsaturated polycarboxylic acid monomer, α, β-ethylenically unsaturated polycarboxylic acid anhydride, aromatic vinyl monomer, Illustrative examples include fluorine-containing vinyl monomers and copolymerizable antioxidants.

  Examples of the α, β-ethylenically unsaturated carboxylic acid ester monomer other than the α, β-ethylenically unsaturated dicarboxylic acid monoester monomer include, for example, methyl acrylate, ethyl acrylate, propyl acrylate, acrylic acid (Meth) acrylic acid alkyl esters such as n-butyl, n-pentyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, and propyl methacrylate (meaning alkyl acrylate and alkyl methacrylate, the same applies hereinafter) A monomer having an alkyl group with 1 to 18 carbon atoms; (meth) acrylic acid alkoxyalkyl ester monomers such as methoxymethyl acrylate and ethoxymethyl methacrylate, wherein the alkoxyalkyl group has 1 carbon atom. 18 to 18 and alkoxy group having 1 to 12 carbon atoms; acrylic Amino group-containing (meth) acrylic acid alkyl ester monomers such as 2-aminoethyl and aminomethyl methacrylate having an alkyl group with 1 to 16 carbon atoms; 2-hydroxyethyl acrylate, 3-methacrylic acid 3- (Meth) acrylic acid hydroxyalkyl ester monomers such as hydroxypropyl having an alkyl group with 1 to 16 carbon atoms; fluoroalkyl group-containing (meth) acrylic such as trifluoroethyl acrylate and difluoromethyl methacrylate An alkyl ester monomer having an alkyl group with 1 to 16 carbon atoms; a maleic acid dialkyl ester such as dimethyl maleate or di-n-butyl maleate with an alkyl group having 1 to 18 carbon atoms Dialkyl fumarate such as dimethyl fumarate and di-n-butyl fumarate A dialkyl ester of maleic acid such as dicyclopentyl maleate and dicyclohexyl maleate having a cycloalkyl group of 4 to 16 carbon atoms; fumaric acid Dicycloalkyl esters of fumaric acid such as dicyclopentyl and dicyclohexyl fumarate having 4 to 16 carbon atoms in the cycloalkyl group; dialkyl esters of itaconic acid such as dimethyl itaconate and di-n-butyl itaconate and alkyl Group having 1 to 18 carbon atoms: itaconic acid dicycloalkyl ester such as dicyclohexyl itaconic acid and cycloalkyl group having 4 to 16 carbon atoms; and the like.

Examples of the α, β-ethylenically unsaturated monocarboxylic acid monomer include acrylic acid, methacrylic acid, and crotonic acid.
Examples of the α, β-ethylenically unsaturated polyvalent carboxylic acid monomer include itaconic acid, fumaric acid and maleic acid.
Examples of the α, β-ethylenically unsaturated polyvalent carboxylic acid anhydride include maleic anhydride.

  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-trifluoromethylstyrene, 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-anilino). Examples include phenyl) crotonamide, N-phenyl-4- (3-vinylbenzyloxy) aniline, N-phenyl-4- (4-vinylbenzyloxy) aniline and the like.

  These other copolymerizable monomers may be used in combination. The content of other monomer units in the highly saturated nitrile rubber (a) is preferably 50% by weight or less, more preferably 40% by weight or less, and particularly preferably 10% by weight or less.

The content of carboxyl groups in the highly saturated nitrile rubber (a) used in the present invention, that is, the number of moles of carboxyl groups per 100 g of the 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, particularly preferably 5 × 10 ^{−3 to} 6 × 10 ⁻² ephr. If the carboxyl group content of the highly saturated nitrile rubber (a) is too small, the crosslinkable nitrile rubber composition may not be sufficiently crosslinked, and the tensile stress of the rubber crosslinked product may be lowered. There is a possibility that the scorch stability of the nitrile rubber composition is deteriorated and the bending fatigue resistance of the rubber cross-linked product is lowered.

  Α, β-ethylenically unsaturated nitrile monomer unit, α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit, diene monomer and / or α-olefin monomer, and other The monomer unit may have a substituent. There are no limitations on such substituents, and alkyl groups, cycloalkyl groups, alkylcycloalkyl groups, alkoxy groups, aryloxy groups, nitro groups, cyano groups, sulfonic acid groups, sulfonic acid ester groups, carboxyl groups, halogens, acetyl groups, An amino group, a hydroxyl group, etc. are mentioned. Further, the bonding position of the substituent may be any of α-carbon or β-carbon at the polymerization reaction site of the monomer forming each monomer unit. Furthermore, when an alkyl group, a cycloalkyl group or an alkylcycloalkyl group is bonded to these α-carbon or β-carbon, they may be bonded to these groups.

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

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

The method for producing the highly saturated nitrile rubber (a) is not particularly limited. In general, α, β-ethylenically unsaturated nitrile monomer, α, β-ethylenically unsaturated dicarboxylic acid monoester monomer, diene monomer and / or α-olefin monomer, and A method of copolymerizing other monomers copolymerizable with these which are added as necessary is convenient and preferable. As the polymerization method, any of the known emulsion polymerization method, suspension polymerization method, bulk polymerization method and solution polymerization method can be used, but the emulsion polymerization method is preferable because the polymerization reaction can be easily controlled.
When the iodine value of the copolymer obtained by copolymerization is higher than 120, the copolymer may be hydrogenated (hydrogenation reaction). The method for hydrogenation is not particularly limited, and a known method may be employed.

Cross-linkable nitrile rubber composition of the present invention, CaO, Ca _{(OH) 2} and Al _(OH) a metal compound selected from ₃ (b) (hereinafter, sometimes simply referred to as "the metal compound (b)".) Containing. Here, CaO, Ca (OH) ₂ and Al (OH) ₃ may be used singly or in combination of two or more, but since the effect of the present invention becomes more remarkable, the metal compound (B) preferably contains 50% by weight or more in total of calcium compounds (e) selected from CaO and Ca (OH) ₂ , more preferably 70% by weight or more, and 100% by weight. It is particularly preferred that the metal compound (b) is a calcium compound (e). The calcium compound (e) is most preferably Ca (OH) ₂ . The amount of the metal compound (b) used is preferably 0.1 to 200 parts by weight, more preferably 1 to 100 parts by weight, still more preferably 1 to 50 parts by weight with respect to 100 parts by weight of the highly saturated nitrile rubber (a). Parts, particularly preferably 1 to 10 parts by weight. Moreover, a commercially available thing can be obtained and used for a metal compound (b).
In the present invention, by combining the highly saturated nitrile rubber (a) having an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit with the metal compound (b), the compression set of the crosslinked product and The heat resistance can be improved. On the other hand, when the metal compound (b) is added to a highly saturated nitrile rubber not having an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit, the compression set and heat resistance are improved. Tends to be difficult to obtain.

The polyamine crosslinking agent (c) contained in the crosslinkable nitrile rubber composition of the present invention is a compound having two or more amino groups or a compound having two or more amino groups at the time of crosslinking. Although there is no particular limitation as long as it is, a plurality of hydrogen atoms of the 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). Compounds are preferred. Specific examples thereof include aliphatic polyvalent amines 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 content of the polyamine crosslinking agent (c) in the crosslinkable nitrile rubber composition of the present invention is preferably 0.1 to 20 parts by weight, more preferably 0.2 parts per 100 parts by weight of the highly saturated nitrile rubber (a). -15 parts by weight, particularly preferably 0.5-10 parts by weight. If the content of the polyamine crosslinking agent (c) is too small, there is a possibility that a rubber crosslinked product having excellent heat resistance and a small compression set may not be obtained. May be reduced.

  The crosslinkable nitrile rubber composition of the present invention may further contain a basic crosslinking accelerator (d) in addition to the highly saturated nitrile rubber (a), the metal compound (b) and the polyamine crosslinking agent (c). preferable. By including the basic crosslinking accelerator (d), the effect of the present invention becomes more remarkable.

  The basic crosslinking accelerator (d) includes tetramethylguanidine, tetraethylguanidine, diphenylguanidine, tolylguanidine such as 1,3-di-o-diortolylguanidine, orthotolylbiguanide, diorthotolylgua of dicatecholboric acid. Guanidine-based crosslinking accelerators such as dizine salts; aldehyde amine-based crosslinking accelerators such as n-butyraldehyde aniline and acetaldehyde ammonia; Of these, guanidine-based crosslinking accelerators are preferable.

  The lower limit of the amount of the basic crosslinking accelerator (d) to 100 parts by weight of the highly saturated nitrile rubber (a) is preferably 0.1 parts by weight, more preferably 0.5 parts by weight, particularly preferably 1 part by weight. The upper limit is preferably 20 parts by weight, more preferably 10 parts by weight, and particularly preferably 5 parts by weight. If the blending amount of the basic crosslinking accelerator (d) is too small, the crosslinking rate may be too slow, and the crosslinking density of the crosslinked product may be reduced. If the blending amount is too large, the crosslinking rate is too fast and scorch may be reduced. May occur or storage stability may be impaired.

  The crosslinkable nitrile rubber composition of the present invention preferably contains carbon black and / or silica as a reinforcing filler. The lower limit of the total amount of carbon black and silica based on 100 parts by weight of the highly saturated nitrile rubber (a) is preferably 0.1 parts by weight, more preferably 0.5 parts by weight, still more preferably 1 part by weight, particularly preferably. The upper limit is preferably 300 parts by weight, more preferably 200 parts by weight, and particularly preferably 120 parts by weight. If the total blending amount of carbon black and silica is too small, the strength of the rubber may be lowered. If the total blending amount is too large, the viscosity increases and the moldability may be impaired. Further, the ratio of the carbon black blending amount to the total blending amount of carbon black and silica is preferably 50% by weight or more, more preferably 80% by weight or more, and 100% by weight (100% by weight) because the effect of the present invention becomes more remarkable. That is, only carbon black) is particularly preferable.

  The carbon black is not particularly limited and may be any carbon black that is usually used for blending rubbers. For example, furnace black, acetylene black, thermal black, channel black, graphite and the like can be used. Among these, furnace black is preferable because the effects of the present invention become more remarkable. Preferred examples of furnace black include SAF, ISAF, ISAF-HS, ISAF-LS, IISAF-HS, HAF, HAF-HS, HAF-LS, MAF, FEF, FEF-LS, GPF, GPF-HS, GPF-LS, SRF, SRF-HS and SRF-LM are mentioned.

Moreover, the particle diameter of carbon black is preferably 15 to 200 nm, more preferably 18 to 100 nm, and the nitrogen adsorption specific surface area is preferably 10 to 260 m ² / g, more preferably 20 to 240 m ² / g. The DBP oil absorption is preferably 50 to 200 ml / 100 g, more preferably 70 to 180 ml / 100 g.

The silica is not particularly limited, and may be any compound containing (SiO ₂ ) in the composition formula, specifically, natural silica such as quartz powder and silica powder; silicic anhydride (Silica gel, aerosil, etc.), synthetic silica such as hydrous silicic acid; silicate metal salts; and the like. Among these, synthetic silica or metal silicate is preferable.

In addition, said natural silica and synthetic silica have a composition formula represented by (SiO ₂ ) or (SiO ₂ .nH ₂ O). As the synthetic silica, anhydrous synthetic silica is preferably used. Anhydrous synthetic silica is preferably used as a so-called white filler (white carbon) that is generally used for synthetic rubber fillers.

  The crosslinkable nitrile rubber composition of the present invention is usually used in the rubber processing field in addition to the above highly saturated nitrile rubber (a), metal compound (b), polyamine crosslinking agent (c) and basic crosslinking accelerator (d). For example, crosslinking accelerators other than basic crosslinking accelerators, crosslinking assistants, crosslinking retarders, non-reinforcing fillers (clay, talc, diatomaceous earth, etc.), anti-aging agents, antioxidants, light stability Agents, anti-scorch agents such as primary amines, plasticizers, processing aids, lubricants, adhesives, lubricants, flame retardants, antifungal agents, acid acceptors, antistatic agents, pigments and the like can be blended. The compounding amounts of these compounding agents are not particularly limited as long as they do not impair the effects of the present invention, and the amount according to the purpose can be appropriately compounded.

  The crosslinkable nitrile rubber composition of the present invention may be blended with a rubber other than the above highly saturated nitrile rubber (a) as long as the effects of the present invention are not impaired. When a rubber other than the highly saturated nitrile rubber (a) is blended, it is preferably 30 parts by weight or less, more preferably 20 parts by weight or less, and particularly preferably 10 parts by weight or less per 100 parts by weight of the highly saturated nitrile rubber (a).

  The crosslinkable nitrile rubber composition of the present invention is prepared by mixing the above components, preferably in a non-aqueous system. The method for preparing the crosslinkable nitrile rubber composition of the present invention is not limited. Usually, the components excluding the polyamine crosslinking agent (c) and the heat labile crosslinking aid are used as Banbury mixer, intermixer, kneader. After first kneading with a mixer such as the above, it can be prepared by transferring to a roll or the like and adding a polyamine cross-linking agent (c), a heat-labile cross-linking aid or the like, and then secondary kneading.

  The water content of the crosslinkable nitrile rubber composition of the present invention is preferably 3% by weight or less, more preferably 1% by weight or less.

The Mooney viscosity (ML _{1 + 4} , 100 ° C.) (compound Mooney) of the crosslinkable nitrile rubber composition of the present invention is preferably 15 to 150, more preferably 50 to 120. When the crosslinkable nitrile rubber composition of the present invention has the above compound Mooney, it is excellent in moldability.

In order to obtain a crosslinked rubber product by crosslinking the crosslinkable nitrile rubber composition of the present invention, molding is performed with a molding machine corresponding to a desired shape, such as an extruder, an injection molding machine, a compressor, a roll, etc., and a crosslinking reaction is performed. To fix the shape as a cross-linked product. Crosslinking may be performed after molding in advance, or 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 1 hour.
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.

The rubber cross-linked product of the present invention has the characteristics that the compression set is small in addition to the characteristics of the highly saturated nitrile rubber excellent in oil resistance and ozone resistance, and particularly the heat resistance is greatly improved.
For this reason, the rubber 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 seal materials 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 .; attached to the connecting part of intake manifold and cylinder head Intake manifold hall Gasket, cylinder head gasket attached to the connection between the cylinder block and cylinder head, rocker cover gasket attached to the connection between 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, lohe V-ribbed 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, 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, air Attenuating rubber parts such as anti-vibration materials, dust covers, automobile interior parts, tires, coated cables, shoe soles, electromagnetic wave shields, adhesives for flexible printed circuit boards, fuel cell separators, cosmetics, and Although it can be used in a wide range of applications such as pharmaceutical fields, food contact fields, and electronics fields, it can be particularly suitably used as a belt and a sealing material.

The present invention will be specifically described below with reference to production examples, examples and comparative examples. However, the present invention is not limited to these examples. In the following formulations, “parts” are based on weight unless otherwise specified.
The test and evaluation were as follows.

(1) Carboxyl group content The carboxyl group content of the highly saturated nitrile rubber is determined by titration with thymolphthalein as an indicator at room temperature using a 0.02N aqueous ethanol solution of potassium hydroxide. It was determined as the number of moles of carboxyl group relative to The unit is ephr.

(2) Mooney viscosity (Polymer Mooney, Compound Mooney)
Mooney viscosity was measured in accordance with JIS K6300-1. The unit is (ML _{1 + 4} , 100 ° C.).

(3) Normal physical properties (tensile strength, 100% tensile stress, elongation)
The crosslinkable nitrile 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 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. This was transferred to a gear type oven and subjected to secondary crosslinking at 170 ° C. for 4 hours to obtain a sheet-like crosslinked product, and the obtained sheet-like crosslinked product was punched with a No. 3 dumbbell to prepare a test piece. Using this test piece, the tensile strength, 100% tensile stress and elongation of the rubber cross-linked product were measured according to JIS K6251.

(4) O-ring compression set Using a mold having an inner diameter of 30 mm and a ring diameter of 3 mm, the crosslinkable nitrile rubber composition was crosslinked at 170 ° C. for 20 minutes at a press pressure of 10 MPa, and then secondary at 170 ° C. for 4 hours. Cross-linking was performed to obtain an O-ring test piece. The compression set was measured according to JIS K6262 under the condition that the test piece was held at 150 ° C. for 168 hours in a 25% compressed state.

(5) Thermal aging test (elongation, elongation change rate)
Using test pieces prepared by primary crosslinking and secondary crosslinking in the same manner as in (3) above, the elongation after 168 hours at 170 ° C. and the rate of change due to thermal aging according to JIS K6257 (normal oven method) ( %).

Production Example 1
In a metal bottle, 180 parts of ion-exchanged water, 25 parts of a 10% strength by weight aqueous sodium dodecylbenzenesulfonate solution, 37 parts of acrylonitrile, 6 parts of mono-n-butyl maleate, and t-dodecyl mercaptan (molecular weight regulator) 0 .75 parts were charged in this order, and after replacing the internal gas with nitrogen three times, 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. Next, 0.1 part of a 10 wt% aqueous hydride quinone solution (polymerization terminator) was added to stop the polymerization reaction, and then the residual monomer was removed using a rotary evaporator at a water temperature of 60 ° C. to obtain 34 wt% of acrylonitrile units. Latex of acrylonitrile-butadiene-mono n-butyl maleate copolymer rubber (composition ratio is determined by H ¹ -NMR analysis) having a butadiene unit of 60% by weight and a mono n-butyl maleate unit of 6% by weight (solid content concentration of about 30% by weight).

  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, A hydrogenation reaction was carried out at a hydrogen pressure of 3 MPa and a temperature of 50 ° C. for 6 hours to obtain a nitrile group-containing highly saturated copolymer rubber latex.

The resulting nitrile group-containing highly saturated copolymer rubber latex is added with twice the volume of methanol to solidify the nitrile group-containing highly saturated copolymer rubber, and then vacuum dried at 60 ° C. for 12 hours to obtain a highly saturated nitrile rubber. (A1) was obtained. The iodine value of the highly saturated nitrile rubber (a1) was 10, the carboxyl group content was 3.2 × 10 ⁻² ephr, and the polymer Mooney viscosity (ML _{1 + 4} , 100 ° C.) was 45. The composition ratio by H ¹ -NMR analysis was 34% by weight of acrylonitrile units, 60% by weight of butadiene units (including hydrogenated parts), and 6% by weight of mono n-butyl maleate units.

Example 1
Using a Banbury mixer, 100 parts of highly saturated nitrile rubber (a1), 40 parts of FEF carbon black (trade name “SEAST SO”, manufactured by Tokai Carbon Co., Ltd.), 5 parts of CaO, trimellitic acid ester (trade name “ADK Cizer”) C-8 ", 5 parts by ADEKA, plasticizer), 1 part of stearic acid (crosslinking accelerator), 4,4'-di- (α, α'-dimethylbenzyl) diphenylamine (trade name" Naugard 445 " , 1.5 parts of Crompton, anti-aging agent), and 1.5 parts of 2-mercaptobenzimidazole (trade name “NOCRACK MB”, manufactured by Ouchi Shinsei Co., Ltd., anti-aging agent), and then mixed. Then, the mixture was transferred to a roll, 2 parts of 1,3-di-o-tolylguanidine (trade name “Noxeller DT”, manufactured by Ouchi Shinsei Co., Ltd., basic crosslinking accelerator), and Sa diamine carbamate (trade name "Diak # 1", DuPont Dow Elastomers Co., polyamine crosslinking agent) 3.4 parts were kneaded was added to prepare a cross-linkable nitrile rubber composition.
The obtained crosslinkable nitrile rubber composition was tested and evaluated for compound Mooney viscosity, normal properties, O-ring compression set, and heat aging resistance. The results are shown in Table 1.

Example 2
A crosslinkable nitrile rubber composition was prepared in the same manner as in Example 1 except that CaO was changed to Ca (OH) ₂ , and in the same manner as in Example 1, compound Mooney viscosity, normal state properties, O-ring compression Permanent strain and heat aging resistance were tested and evaluated. The results are shown in Table 1.

Example 3
A crosslinkable nitrile rubber composition was prepared in the same manner as in Example 1 except that CaO was changed to Al (OH) ₃ , and in the same manner as in Example 1, compound Mooney viscosity, normal physical properties, O-ring compression Permanent strain and heat aging resistance were tested and evaluated. The results are shown in Table 1.

Comparative Example 1
A crosslinkable nitrile rubber composition was prepared in the same manner as in Example 1 except that CaO was not added, and in the same manner as in Example 1, compound Mooney viscosity, normal physical properties, O-ring compression set, and heat resistance Aging was tested and evaluated. The results are shown in Table 1.

Comparative Example 2
A cross-linkable nitrile rubber composition was prepared in the same manner as in Example 1 except that CaO was changed to Na ₂ CO ₃ , and in the same manner as in Example 1, compound Mooney viscosity, normal properties, O-ring compression set And heat aging resistance were tested and evaluated. The results are shown in Table 1.

As Table 1 shows, the crosslinkable nitrile rubber composition of the present invention example had a small O-ring compression set and was excellent in heat resistance (thermal aging test). On the other hand, in Comparative Example 1 that does not satisfy the requirements of the present invention because it does not contain a metal compound (b) selected from CaO, Ca (OH) ₂ and Al (OH) ₃ , O-ring compression set Was small, but the heat resistance (heat aging test) deteriorated. Furthermore, instead of the metal compound (b) selected from CaO, Ca (OH) ₂ and Al (OH) ₃ , in Comparative Example 2 using Na ₂ CO ₃ which is a salt of a strong base and a weak acid, compression set Has increased.

Claims (9)

a highly saturated nitrile rubber (a) having an α, β-ethylenically unsaturated nitrile monomer unit and an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit and having an iodine value of 120 or less; A crosslinkable nitrile rubber composition comprising a metal compound (b) selected from CaO, Ca (OH) ₂ and Al (OH) ₃ and a polyamine crosslinking agent (c). The crosslinkable nitrile rubber composition according to claim 1, wherein the metal compound (b) is a calcium compound (e) selected from CaO and Ca (OH) ₂ .   The crosslinkable nitrile rubber composition according to claim 1 or 2, wherein a content ratio of the metal compound (b) is 0.1 to 200 parts by weight with respect to 100 parts by weight of the highly saturated nitrile rubber (a).   The crosslinkable nitrile rubber composition according to any one of claims 1 to 3, wherein the polyamine crosslinking agent (c) is hexamethylenediamine carbamate. The crosslinkable nitrile rubber composition according to any one of claims 1 to 4, wherein the amount of carboxyl groups of the highly saturated nitrile rubber (a) is 5 x 10 ^{-4 to} 5 x 10 ^-1 ephr.   The crosslinkable nitrile rubber composition according to any one of claims 1 to 5, further comprising a basic crosslinking accelerator (d).   The crosslinkable nitrile rubber composition according to any one of claims 1 to 6, further comprising carbon black and / or silica.   A rubber cross-linked product obtained by cross-linking the cross-linkable nitrile rubber composition according to claim 1.   The rubber cross-linked product according to claim 8, which is a belt or a seal material.