JP2008179663A - Cross-linkable nitrile rubber composition and cross-linked rubber product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cross-linkable nitrile rubber composition giving cross-linked rubber products which are small in compression set and are excellent in abrasion resistance. <P>SOLUTION: The cross-linkable nitrile rubber composition comprises a highly saturated nitrile (a) havingα,β-ethylenic unsaturated nitrile monomer units and α,β-ethylenic unsaturated dicarboxylate monoester monomer units and having an iodine value of ≤120, calcium carbonate (b) having a BET specific surface area of ≥10 m<SP>2</SP>/g, and a polyamine-based cross-linking agent (c). The calcium carbonate (b) having a BET specific area of ≥10 m<SP>2</SP>/g is preferably prepared by subjecting at least one organic acid selected from the group consisting of fatty acids, fatty acid salts, fatty acid esters, resin acids, resin acid salts, and fatty acid esters to a surface treatment. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

Nitrile group-containing highly saturated copolymer rubber (“highly saturated nitrile rubber”) obtained by hydrogenating a rubber containing an α, β-ethylenically unsaturated nitrile monomer unit represented by acrylonitrile-butadiene copolymer rubber Is also known as a rubber excellent in oil resistance, heat resistance and ozone resistance. Highly saturated nitrile rubber cross-linked products are mainly used for rubber products for automobiles in various applications such as gaskets, packings, oil seals, belts and hoses. Recently, quality requirements in the market have become higher, and long life has been required especially for sealing applications around engines, and in addition, a light-colored rubber cross-linked product close to white has been required. For this reason, a carbon black which is a rubber cross-linked product having a smaller compression set and superior wear resistance as compared with conventional ones and, if possible, for lightening the color, the rubber cross-linked product is a reinforcing filler. It has become desirable to realize without the blending of.
Patent Document 1 crosslinks a crosslinkable rubber composition containing a highly saturated nitrile rubber containing an α, β-ethylenically unsaturated dicarboxylic acid monoalkyl ester monomer unit, a polyamine-based crosslinking agent and a basic crosslinking accelerator. It is reported that the rubber cross-linked product obtained in this way is excellent in heat resistance, bending fatigue resistance and the like, and has a small compression set. However, the crosslinked rubber has excellent bending fatigue resistance without the addition of carbon black, and there is a limit to reducing the compression set, so it is difficult to meet the needs for lightening. It was.

JP 2001-55471 A

  An object of the present invention is to provide a crosslinkable nitrile rubber composition that provides a rubber cross-linked product having a small compression set and excellent wear resistance.

As a result of earnest research, the present inventor blends a specific calcium carbonate with a highly saturated nitrile rubber containing an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit and crosslinks with a specific crosslinker. Thus, the inventors have found that the above object can be achieved, and have completed the present invention.
Thus, according to the present invention, an α, β-ethylenically unsaturated nitrile monomer unit and an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit having an iodine value of 120 or less are highly saturated. There is provided a crosslinkable nitrile rubber composition comprising a nitrile rubber (a), calcium carbonate (b) having a BET specific surface area of 10 m ² / g or more, and a polyamine-based crosslinking agent (c).
In the crosslinkable nitrile rubber composition of the present invention, preferably the calcium carbonate (b) having a BET specific surface area of 10 m ² / g or more is a fatty acid, a fatty acid salt, a fatty acid ester, a resin acid, a resin acid salt, and a resin acid ester. The surface is treated with at least one organic material selected from the group consisting of:
Preferably, the crosslinkable nitrile rubber composition of the present invention has a carbon black content of 2% by weight or less.
Further, according to another aspect of the present invention, there is provided a rubber cross-linked product obtained by cross-linking any of the above cross-linkable nitrile rubber compositions. Preferably, the rubber cross-linked product is worn by a pico abrasion test according to JIS K6264-2. The volume is 10 × 10 ⁻² cm ³ or less, and preferably, the rubber cross-linked product is a rubber member for sealing or a gasket.

  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 wear 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), calcium carbonate (b) having a BET specific surface area of 10 m ² / g or more, and a polyamine-based crosslinking agent (c).

  The monomer forming the α, β-ethylenically unsaturated nitrile monomer unit of the highly saturated nitrile rubber (a) (hereinafter sometimes referred to as “α, β-ethylenically unsaturated nitrile”) is It is not limited as long as it is an α, β-ethylenically unsaturated compound having a nitrile group, and includes acrylonitrile; α-halogenoacrylonitrile such as α-chloroacrylonitrile and α-bromoacrylonitrile; and α-alkylacrylonitrile such as methacrylonitrile. Of these, acrylonitrile and methacrylonitrile are preferred. 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 low, the rubber cross-linked product may have low oil resistance, and conversely if too high, cold resistance may be reduced.

  The monomer forming the α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit of the highly saturated nitrile rubber (a) has one free carboxyl group for crosslinking. 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. The carbon number of the alkyl group is preferably 1-10, more preferably 2-6, the carbon number of the cycloalkyl group is preferably 5-12, more preferably 6-10, and the carbon number of the alkylcycloalkyl 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 large, the scorch of the cross-linkable nitrile rubber composition may be reduced. Deterioration of stability and deterioration of fatigue resistance of the rubber cross-linked product may occur.

  In addition to the above α, β-ethylenically unsaturated nitrile monomer unit and α, β-ethylenic dicarboxylic acid monoester monomer unit, the highly saturated nitrile rubber (a) is a rubber cross-linked product having rubber elasticity. For possession, it usually has diene monomer units and / or α-olefin monomer units.

  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 large, the heat resistance and chemical stability 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 monomers include α, β-ethylenically unsaturated dicarboxylic acid monoester monomers other than α, β-ethylenically unsaturated dicarboxylic acid monoester monomers, α, β-ethylenically unsaturated monomers. Saturated monocarboxylic acid monomer, α, β-ethylenically unsaturated polyvalent carboxylic acid monomer, α, β-ethylenically unsaturated polyvalent carboxylic acid anhydride, aromatic vinyl monomer, fluorine-containing vinyl monomer Examples thereof include a monomer and a copolymerizable anti-aging agent.

  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 below. ] Monomers having alkyl groups of 1 to 18 carbon atoms; (meth) acrylic acid alkoxyalkyl ester monomers such as methoxymethyl acrylate and ethoxymethyl methacrylate, and having carbon number of alkoxyalkyl groups Having 1 to 18 carbon atoms and an alkoxy group having 1 to 12 carbon atoms; an amino group-containing (meth) acrylic acid alkyl ester monomer such as 2-aminoethyl acrylate and aminomethyl methacrylate, and carbon having an alkyl group Those having a number of 1 to 16; (meth) acrylic acid hydroxyalkyl ester monomers such as 2-hydroxyethyl acrylate and 3-hydroxypropyl methacrylate having an alkyl group having 1 to 16 carbon atoms; acrylic Fluoroalkyl group-containing (meth) acrylic such as trifluoroethyl acid and difluoromethyl methacrylate Those carbon atoms in the alkyl group of 1 to 16 and an alkyl ester monomer;

  Dialkyl maleates such as dimethyl maleate and di-n-butyl maleate having an alkyl group having 1 to 18 carbon atoms; Dialkyl esters of fumarate such as dimethyl fumarate and di-n-butyl fumarate Alkyl groups having 1 to 18 carbon atoms; maleic acid dicycloalkyl esters such as dicyclopentyl maleate and dicyclohexyl maleate having 4 to 16 carbon atoms in the cycloalkyl group; dicyclopentyl fumarate and fumarate Dicycloalkyl esters of fumaric acid, such as dicyclohexyl acid, and having a cycloalkyl group having 4 to 16 carbon atoms; Dialkyl esters of itaconic acid, such as dimethyl itaconate, di-n-butyl itaconate, etc. 1 to 18: dicyclohexyl itaconate, etc. Carbon number of the cycloalkyl group of 4 to 16 A itaconic acid dicycloalkyl esters; 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 contained 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 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.

The crosslinkable nitrile rubber composition of the present invention contains calcium carbonate (b) having a BET specific surface area of 10 m ² / g or more. The calcium carbonate (b) is a natural calcium carbonate such as heavy calcium carbonate, cucumber, chalk, etc., having a BET specific surface area of 10 m ² / g or more; light calcium carbonate (also referred to as precipitated calcium carbonate). Either calcium carbonate having a BET specific surface area of 10 m ² / g or more can be used, but synthetic calcium carbonate is preferred from the viewpoint of easy procurement of a BET specific surface area of 10 m ² / g or more.
Heavy calcium carbonate is produced by pulverizing coarse crystalline limestone, hum powder is produced by pulverizing weathered shells, and chalk is produced by pulverizing weathered microbial shells. The shape is irregular and the primary particle size is 4 μm as a standard. Light calcium carbonate is produced by calcining dense limestone into quick lime and carbon dioxide, and blowing the carbon dioxide into slaked lime obtained by adding water to quick lime. The particle size and particle shape are adjusted by this blowing condition. Light calcium carbonate can also be obtained by reacting sodium chloride with calcium chloride or slaked lime. The particle shape and primary particle size of light calcium carbonate are 1-5 μm (minor) in the form of spindle (calcite) or rod (aragonite), and 0.02-0.1 μm in the cubic (orthorhombic) type. (Colloid) and 0.1-1 μm (hemi).

Calcium carbonate (b), the gas (nitrogen) BET specific surface area by the measurement based on the adsorption method ^{10 m} 2 / g or more, preferably 15~200m ² / g, more preferably 20 to 100 m ² / g. If the BET specific surface area of calcium carbonate (b) is too small, the wear resistance is inferior. Conversely, if the BET specific surface area is too large, the compression set tends to increase.

As calcium carbonate (b) having a BET specific surface area of 10 m ² / g or more, the particle surface is at least one selected from the group consisting of fatty acids, fatty acid salts, fatty acid esters, resin acids, resin acid salts and resin acid esters. Those treated with an organic material are preferred, and those treated with a fatty acid or resin acid are particularly preferred.
Preferred examples of the fatty acid include saturated or unsaturated fatty acids having 6 to 24 carbon atoms, particularly 10 to 20 carbon atoms. Examples of the saturated or unsaturated fatty acid having 6 to 24 carbon atoms include stearic acid, palmitic acid, lauric acid, behenic acid, oleic acid, erucic acid, linoleic acid and the like. In particular, stearic acid, palmitic acid, lauric acid, and oleic acid are preferable. You may use these in mixture of 2 or more types.
As the fatty acid salt, an alkali metal salt such as a sodium salt or potassium salt of a saturated or unsaturated fatty acid having 6 to 24 carbon atoms, particularly 10 to 20 carbon atoms is preferable.
Examples of the fatty acid ester include esters of the above-described saturated or unsaturated fatty acid having 6 to 24 carbon atoms, particularly 10 to 20 carbon atoms, and alcohol having 6 to 18 carbon atoms, particularly saturated aliphatic alcohol having 10 to 18 carbon atoms. Preferably mentioned.
Examples of the resin acid include abietic acids such as abietic acid, dehydroabietic acid, dihydroabietic acid or polymers thereof, disproportionated rosin, hydrogenated rosin, polymerized rosin, etc., and rosin (particularly contained in rosin) Rosin acid) is preferred.
The resin acid salt is preferably an alkali metal salt or alkaline earth metal salt of the resin acid.
Resin acid esters include rosin pentaerythritol ester, rosin glycerol ester, hydrogenated rosin methyl ester, hydrogenated rosin triethylene glycol ester, hydrogenated rosin pentaerythritol ester, and the like.
The surface-treated calcium carbonate (b) has an affinity for the highly saturated nitrile rubber (a) in addition to the aggregation of the calcium carbonate itself not becoming hard, so that the effect of the present invention becomes even more remarkable. .

The content of calcium carbonate (b) having a BET specific surface area of 10 m ² / g or more in the crosslinkable nitrile rubber composition of the present invention is preferably 5 to 150 parts by weight with respect to 100 parts by weight of the highly saturated nitrile rubber (a). More preferably, it is 10-120 weight part, Most preferably, it is 20-100 weight part. If the calcium carbonate (b) content is too small, the resulting rubber cross-linked product may have insufficient wear resistance, and conversely if too high, the workability may be poor.

The polyamine-based 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 if not particularly limited in a plurality of hydrogen atoms of the aliphatic hydrocarbons and aromatic hydrocarbons, (structure represented by -CONHNH _2, CO represents. a carbonyl group) amino group or hydrazide structures substituted with The compounds are preferred. Specific examples thereof include aliphatic polyamines such as hexamethylene diamine, hexamethylene diamine carbamate, tetramethylene pentamine, hexamethylene diamine cinnamaldehyde adduct, hexamethylene diamine dibenzoate salt; 2,2-bis {4- Aromatic polyamines such as (4-aminophenoxy) phenyl} propane, 4,4′-methylenedianiline, m-phenylenediamine, p-phenylenediamine, 4,4′-methylenebis (o-chloroaniline); Compounds having two or more hydrazide structures such as isophthalic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, and the like are mentioned, and hexamethylenediamine carbamate is particularly preferable.

  The content of the polyamine-based crosslinking agent (c) in the crosslinkable nitrile rubber composition of the present invention is preferably 0.1 to 20 parts by weight, more preferably 0.1 parts by weight with respect to 100 parts by weight of the highly saturated nitrile rubber (a). 2 to 15 parts by weight, particularly preferably 0.5 to 10 parts by weight. If the content of the polyamine-based crosslinking agent (b) is too small, there is a possibility that a rubber cross-linked product having excellent wear resistance and a small compression set may not be obtained. Fatigue may be reduced.

The crosslinkable nitrile rubber composition of the present invention includes, in addition to the highly saturated nitrile rubber (a), calcium carbonate (b) having a BET specific surface area of 10 m ² / g or more, and a polyamine-based crosslinking agent (c). Ingredients commonly used in, such as crosslinking accelerators, crosslinking aids, crosslinking retarders, reinforcing fillers (carbon black, silica, etc.), non-reinforcing fillers (clay, talc, diatomaceous earth, etc.), anti-aging Agents, antioxidants, light stabilizers, scorch inhibitors such as primary amines, plasticizers, processing aids, lubricants, adhesives, lubricants, flame retardants, antifungal agents, acid acceptors, antistatic agents, pigments, etc. 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 rubber cross-linked product obtained by cross-linking the cross-linkable nitrile rubber composition of the present invention has a small compression set and wear resistance without containing carbon black which is a filler having a very strong reinforcing effect. Excellent in properties. Therefore, by crosslinking a crosslinkable nitrile rubber composition having a carbon black content of preferably 2% by weight or less, more preferably 1% by weight or less, and particularly preferably 0.5% by weight or less, compression set is reduced. A light-colored rubber cross-linked product having a small size and excellent wear resistance can be obtained.
In addition, it can be easily colored into a predetermined color by blending a colorant such as a pigment.

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-based crosslinking agent (c) and the heat-labile crosslinking aid are used as a Banbury mixer, an intermixer, After primary kneading with a mixer such as a kneader, the mixture is transferred to a roll or the like, and a polyamine-based crosslinking agent (c) or the like is added and secondarily kneaded.
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.

  The crosslinkable nitrile rubber composition of the present invention has excellent scorch stability, and the time tc (10) corresponding to 10% vulcanization (crosslinking) as defined in JIS K6300-2 measured at 170 ° C. is preferably 0.1. -10 minutes, more preferably 0.3-5 minutes, particularly preferably 0.5-3 minutes. The time tc (90) corresponding to 90% vulcanization (crosslinking) is preferably 3 to 60 minutes, more preferably 5 to 30 minutes, and particularly preferably 7 to 25 minutes.

In order to crosslink this crosslinkable nitrile rubber composition to obtain the rubber cross-linked product of the present invention, the crosslinkable nitrile rubber composition is molded by a molding machine corresponding to a desired shape, for example, an extruder, an injection molding machine, a compressor, a roll, etc. The shape is fixed as a crosslinked product by reaction. 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, heat resistance and ozone resistance, and particularly the wear resistance is greatly improved. The wear volume of the crosslinked rubber of the present invention as measured based on the JIS K6264-2 pico abrasion test is preferably 10 × 10 ⁻² cm ³ or less, more preferably 8 × 10 ⁻² cm ³ or less, and particularly preferably 6 × 10 ⁻² cm ³ or less

The rubber cross-linked product of the present invention having these characteristics includes O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, well head seals, pneumatic equipment seals, air conditioner cooling devices and air conditioner refrigeration products. Seal for sealing of fluorocarbons or fluorohydrocarbons or carbon dioxide used for compressors for machinery, sealing seal for supercritical carbon dioxide or subcritical carbon dioxide used for cleaning media for precision cleaning, rolling devices (rolling bearings, Seals for automobile hub units, automobile water pumps, linear guide devices, ball screws, etc.), valves and valve seats, various rubber members for sealing such as BOP (Blow Out Preventar), platters; and intake manifolds and cylinder heads At the connection with Intake manifold gasket to be attached, cylinder head gasket to be attached to the connecting portion between the cylinder block and the cylinder head, rocker cover gasket to be attached to the connecting portion between the rocker cover and the cylinder head, oil pan and cylinder block or transmission case Various types of gaskets, such as an oil pan gasket attached to a connecting portion of the fuel cell, a gasket for a fuel cell separator attached between a pair of housings sandwiching a unit cell having a positive electrode, an electrolyte plate and a negative electrode, and a top cover gasket for a hard disk drive; Is preferably used.
Further, the rubber cross-linked product of the present invention includes various rolls such as a printing roll, a steelmaking roll, a papermaking roll, an industrial roll, and an office machine roll; a flat belt (film core flat belt, cord flat belt, laminated flat belt). Belts, single unit flat belts, etc.), V belts (wrapped V belts, low edge V belts, etc.), V ribbed belts (single V ribbed belt, double V ribbed belt, wrapped V ribbed belt, back rubber V ribbed belt, upper cog V ribbed belt, etc.), CVT Belts such as belts, timing belts, toothed belts, conveyor belts, etc .; fuel hoses, turbo air hoses, oil hoses, radiator hoses, heater hoses, water hoses, vacuum brake hoses, control hoses, air conditioning hoses, brake hoses, Power steering ho Various hoses such as springs, air hoses, marine hoses, risers, flow lines; various boots such as CVJ boots, propeller shaft boots, constant velocity joint boots, rack and pinion boots; cushion materials, dynamic dampers, rubber couplings, air springs Damping material rubber parts such as anti-vibration materials; dust covers, automotive interior parts, tires, coated cables, shoe soles, electromagnetic shielding, adhesives for flexible printed circuit boards, fuel cell separators, cosmetics, and pharmaceuticals It can also be used for a wide range of applications, such as the field of contact with food, the field of contact with food, and the field of electronics.

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 rubber is the number of moles of carboxyl groups per 100 grams of rubber by titration with 0.02N aqueous ethanol solution of potassium hydroxide and using thymolphthalein as an indicator at room temperature. As sought. The unit is ephr.
(2) Mooney viscosity (Polymer Mooney, Compound Mooney)
It measured according to JIS K6300-1. The unit is (ML _{1 + 4} , 100 ° C.).

(3) Crosslinking characteristics [measurement of tc (10), tc (90)]
According to JIS K6300-2, a time tc (10) corresponding to 10% vulcanization (crosslinking) and a time tc (90) corresponding to 90% vulcanization (crosslinking) were measured. The measurement temperature is 170 ° C., and the unit is min (minutes). Large values of tc (10) and tc (90) indicate excellent scorch stability.

(4) 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 a sheet-like cross-linked product obtained by secondary cross-linking at 170 ° C. for 4 hours 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.
(5) Normal physical properties (hardness)
The hardness of the rubber cross-linked product was measured using a durometer hardness tester, type A, according to JIS K6253 for the sheet-like rubber cross-linked product obtained by primary and secondary cross-linking in the same manner as in (4) above.

(6) 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 secondary crosslinked at 170 ° C. for 4 hours. 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.

(7) Pico abrasion test The sheet-like rubber cross-linked product obtained by primary and secondary crosslinking in the same manner as in (4) above, in accordance with the method of the pico abrasion test specified in JIS K6264-2, was rotated 20 times in the normal direction. The wear volume was measured after repeating 20 times twice and rotating a total of 80 times. The smaller the wear volume value, the smaller the degree of wear and the better the wear resistance.

(Production Example 1)
In a metal bottle, 180 parts of ion-exchanged water, 25 parts of a 10% strength by weight aqueous solution of sodium dodecylbenzenesulfonate, 37 parts of acrylonitrile, 6 parts of mono-n-butyl maleate, t-dodecyl mercaptan (molecular weight regulator) 0.5 In order of parts, the internal gas was replaced with nitrogen three times, and then 57 parts of 1,3-butadiene was charged. The metal bottle was kept at 5 ° C., 0.1 part of cumene hydroperoxide (polymerization initiator) was charged, and the polymerization reaction was carried out for 16 hours while rotating the metal bottle. The polymerization reaction was stopped by adding 0.1 part of a 10% by weight aqueous solution of hydridoquinone (polymerization terminator), then the residual monomer was removed using a rotary evaporator at a water temperature of 60 ° C., and 34% by weight of acrylonitrile unit, butadiene A latex of acrylonitrile-butadiene-mono n-butyl maleate copolymer rubber having a unit of 60% by weight and a mono n-butyl maleate unit of 6% by weight (solid content concentration of about 30% by weight) was obtained.

A palladium catalyst (a solution obtained by mixing 1 wt% palladium acetate / acetone solution and equal weight of ion exchange water) was added to an autoclave so that the palladium content was 1000 ppm with respect to the rubber weight contained in the latex, and hydrogen was added. A hydrogenation reaction was performed at a 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 60.

(Example 1)
Using a Banbury mixer, 100 parts of highly saturated nitrile rubber (a1), 80 parts of light and light calcium carbonate (trade name “Hakuenka CC”, manufactured by Shiraishi Kogyo Co., Ltd., see Table 1 for characteristics), trimellitic acid ester (trade name) “ADK Cizer C-8”, manufactured by ADEKA, 5 parts plasticizer, 1 part stearic acid (crosslinking accelerator), 4,4′-di- (α, α′-dimethylbenzyl) diphenylamine (trade name “ Naugard 445 ", manufactured by Crompton, anti-aging agent 1.5 parts, 2-mercaptobenzimidazole (trade name" NOCRACK MB ", manufactured by Ouchi Shinsei Co., anti-aging agent) 1.5 parts, and polyoxyethylene alkyl ether Phosphate ester (Product name “Phosphanol RL-210”, manufactured by Toho Chemical Industry Co., Ltd., processing aid; monoester 41.6% by weight, diester 38 4 parts by weight, mixed with about 20% by weight polyoxyethylene alkyl ether) was added and mixed, then the mixture was transferred to a roll and 1,3-di-o-tolylguanidine (trade name “Noxeller DT”) 2 parts of Ouchi Shinsei Co., Ltd., crosslinking accelerator) and 2.6 parts of hexamethylenediamine carbamate (trade name “Diak # 1”, manufactured by DuPont Dow Elastomer Co., Ltd., polyamine crosslinking agent) The mixture was kneaded to prepare a crosslinkable nitrile rubber composition.
Table 2 shows the results of testing and evaluating compound Mooney viscosity, crosslinking properties, normal properties, O-ring compression set and wear resistance using the obtained crosslinkable nitrile rubber composition. The wear volume is shown in Table 2 as a value 100 times the measured value.

(Example 2)
In Example 1, instead of light and light calcium carbonate (trade name “Shiraka Hana CC”), an equivalent number of light and light calcium carbonate (trade name “ACTIFORT 700”, manufactured by Shiraishi Kogyo Co., Ltd., characteristics shown in Table 1) were used. Prepared a crosslinkable nitrile rubber composition in the same manner as in Example 1. About the obtained crosslinkable nitrile rubber composition, the result of having tested and evaluated similarly to Example 1 is described in Table 2.

(Example 3)
In Example 1, in place of the light and light calcium carbonate (trade name “Shiratsuka CC”), an equal number of light and light calcium carbonate (trade name “Shiratsuka O”, manufactured by Shiraishi Kogyo Co., Ltd., for characteristics, see Table 1) was used. Prepared a crosslinkable nitrile rubber composition in the same manner as in Example 1. About the obtained crosslinkable nitrile rubber composition, the result of having tested and evaluated similarly to Example 1 is described in Table 2.

(Comparative Example 1)
In Example 1, in place of the light and light calcium carbonate (trade name “Shiraka Hana CC”), an equal number of light and light calcium carbonate (trade name “Silver W”, manufactured by Shiraishi Kogyo Co., Ltd., for characteristics, see Table 1) was used. Prepared a crosslinkable nitrile rubber composition in the same manner as in Example 1. About the obtained crosslinkable nitrile rubber composition, the result of having tested and evaluated similarly to Example 1 is described in Table 2.

(Comparative Example 2)
In Example 1, 40 parts of precipitated silica (trade name “Carplex 1120”, manufactured by Shionogi & Co., Ltd., characteristics are shown in Table 1) were used in place of 80 parts of light and light calcium carbonate (trade name “Shirotsuka CC”). Otherwise, a crosslinkable nitrile rubber composition was prepared in the same manner as in Example 1. About the obtained crosslinkable nitrile rubber composition, the result of having tested and evaluated similarly to Example 1 is described in Table 2.

As Table 1 shows, the crosslinkable nitrile rubber composition of the present invention examples had large tc (10) and tc (90) and excellent scorch stability. In addition, the rubber cross-linked products by these have large and well-balanced tensile strength, tensile stress, and elongation, and the O-ring compression set is small and the wear volume is small (Examples 1 to 1). 3).
On the other hand, when calcium carbonate having a BET specific surface area of less than 10 m ² / g was used, the obtained rubber cross-linked product had reduced tensile strength and tensile stress, and had a large wear volume (Comparative Example 1). When the BET specific surface area BET specific surface area in place of the calcium carbonate or 10 m 2 / ^g is used precipitated silica is 10 m 2 / ^g or more, the obtained rubber cross-linked product, but the wear resistance was not deteriorated, The compression set was extremely inferior (Comparative Example 2).

Claims (6)

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 an iodine value of 120 or less, BET A crosslinkable nitrile rubber composition comprising calcium carbonate (b) having a specific surface area of 10 m ² / g or more and a polyamine-based crosslinking agent (c). The calcium carbonate (b) having a BET specific surface area of 10 m ² / g or more is surface-treated with at least one organic material selected from the group consisting of fatty acids, fatty acid salts, fatty acid esters, resin acids, resin acid salts and resin acid esters. The crosslinkable nitrile rubber composition according to claim 1, which has been prepared.   The crosslinkable nitrile rubber composition according to claim 1 or 2, wherein the carbon black content is 2% by weight or less.   A crosslinked rubber product obtained by crosslinking the crosslinkable nitrile rubber composition according to any one of claims 1 to 3. The rubber cross-linked product according to claim 4, wherein a wear volume by a pico wear test of JIS K6264-2 is 10 x 10 ^-2 cm ³ or less.   The rubber cross-linked product according to claim 4 or 5, which is a rubber member or gasket for sealing.