JP7259423B2 - Nitrile rubber composition and cross-linked rubber - Google Patents

Description

TECHNICAL FIELD The present invention relates to a nitrile rubber composition and a crosslinked rubber product, and more particularly, a nitrile rubber composition capable of providing a crosslinked rubber product excellent in long-life coolant resistance and compression set resistance, and such a nitrile rubber composition. The present invention relates to a rubber cross-linked product obtained using a rubber composition.

Nitrile rubber (acrylonitrile-butadiene copolymer rubber) has traditionally been used as a material for automotive rubber parts such as hoses, tubes, and seals, taking advantage of its oil resistance, mechanical properties, and chemical resistance. , Hydrogenated nitrile rubber (hydrogenated acrylonitrile-butadiene copolymer rubber) obtained by hydrogenating the carbon-carbon double bond in the polymer main chain of nitrile rubber (hydrogenated acrylonitrile-butadiene copolymer rubber) has excellent heat resistance, so it can be used for seals, belts, hoses, diaphragms, etc. Used for rubber parts. On the other hand, in applications such as seals and belts, a smaller compression set is required.

For example, as an attempt to reduce such compression set, Patent Document 1 proposes a technique for a carboxyl group-containing nitrile rubber obtained by introducing a carboxyl group into a nitrile rubber.

WO2007/049651

According to the technique of Patent Document 1, although a cross-linked rubber product having a compression set reduced to a certain extent can be obtained, it cannot be said that the water resistance is sufficient. In particular, there are cases where it is not suitable for use as a sealing material for sealing water-based refrigerants in cold regions.

As the water-based refrigerant, LLC (Long Life Coolant) or the like may be used as a refrigerant capable of cooling at a lower temperature. Excellent quality is required. In particular, even if it has sufficient water resistance to water, it may not necessarily exhibit sufficient resistance to LLC. It is required to exhibit sufficient resistance to such LLC.

The present invention has been made in view of such circumstances, and provides a nitrile rubber composition capable of providing a rubber cross-linked product having excellent long-life coolant resistance (LLC resistance) and compression set resistance, and such a nitrile rubber composition. An object of the present invention is to provide a cross-linked rubber product using a rubber composition.

As a result of intensive studies to achieve the above object, the present inventors have found that α,β-ethylenically unsaturated dicarboxylic acid monoester monomer units are contained in a specific ratio and the iodine value is a specific value or less. and the total content of sodium, calcium, and magnesium, and the content of sodium alone are controlled within a specific range. The inventors have found that a rubber composition can achieve the above objects, and have completed the present invention.

That is, according to the present invention, the α,β-ethylenically unsaturated dicarboxylic acid monoester monomer unit is contained in a proportion of 0.1 to 20% by weight, the iodine value is 120 or less, sodium, calcium, and a carboxyl group-containing nitrile rubber having a total magnesium content of 130 to 1000 ppm by weight and a sodium content of 600 ppm by weight or less, and a filler containing silicon. .

The nitrile rubber composition of the present invention preferably further contains modified silicone oil.
In the nitrile rubber composition of the present invention, the modified silicone oil preferably has an amino group as a modifying group.
In the nitrile rubber composition of the present invention, the carboxyl group-containing nitrile rubber preferably contains 11 to 50% by weight of α,β-ethylenically unsaturated monocarboxylic acid ester monomer units.

Further, according to the present invention, there is provided a crosslinkable rubber composition obtained by blending the above nitrile rubber composition with a polyvalent amine compound.
Furthermore, according to the present invention, there is provided a rubber cross-linked product obtained by cross-linking the above nitrile rubber composition.

According to the present invention, it is possible to provide a nitrile rubber composition capable of giving a rubber crosslinked product excellent in LLC resistance and compression set resistance, and a rubber crosslinked product using such a nitrile rubber composition. can.

<Nitrile rubber composition>
The nitrile rubber composition of the present invention contains an α,β-ethylenically unsaturated dicarboxylic acid monoester monomer unit in a proportion of 0.1 to 20% by weight, has an iodine value of 120 or less, and contains sodium and calcium. , and a carboxyl group-containing nitrile rubber having a total magnesium content of 130 to 1000 ppm by weight and a sodium content of 600 ppm by weight or less, and a filler containing silicon.

Although the carboxyl group-containing nitrile rubber used in the present invention is not particularly limited, examples include an α,β-ethylenically unsaturated nitrile monomer, an α,β-ethylenically unsaturated dicarboxylic acid monoester monomer, and , and those obtained by copolymerizing other copolymerizable monomers that are 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. Examples include acrylonitrile; α-chloroacrylonitrile, α-bromoacrylonitrile, etc. α-halogenoacrylonitrile of; α-alkylacrylonitrile such as methacrylonitrile; Among these, acrylonitrile and methacrylonitrile are preferred, and acrylonitrile is more preferred. The α,β-ethylenically unsaturated nitrile monomers may be used singly or in combination.

The content of α,β-ethylenically unsaturated nitrile monomer units in the carboxyl group-containing nitrile rubber used in the present invention is preferably 7 to 60% by weight, more preferably 7 to 60% by weight, based on the total monomer units. 10 to 40% by weight, more preferably 12 to 25% by weight. By setting the content of the α,β-ethylenically unsaturated nitrile monomer unit within the above range, the resulting crosslinked rubber can be made excellent in oil resistance and cold resistance. When carboxyl group-containing nitrile rubbers with different monomer compositions are used in combination, α,β-ethylenically unsaturated nitrile monomer units in the entire mixture of carboxyl group-containing nitrile rubbers with different monomer compositions should be within the above range (the same applies to units of each monomer described later).

The α,β-ethylenically unsaturated dicarboxylic acid monoester monomer is an α,β-ethylenically unsaturated dicarboxylic acid monoester having one unsubstituted (free) carboxyl group that is not esterified. It is not particularly limited as long as it is a monomer. Unsubstituted carboxyl groups are mainly used for cross-linking.

Examples of such α,β-ethylenically unsaturated dicarboxylic acid monoester monomers include maleic acid monoalkyl esters such as monomethyl maleate, monoethyl maleate, monopropyl maleate, and mono-n-butyl maleate; maleic acid monocycloalkyl esters such as monocyclopentyl, monocyclohexyl maleate, monocycloheptyl maleate; maleic acid monoalkylcycloalkyl esters such as monomethylcyclopentyl maleate, monoethylcyclohexyl maleate; monomethyl fumarate, monoethyl fumarate, Fumaric acid monoalkyl esters such as monopropyl fumarate and mono-n-butyl fumarate; Fumaric acid monocycloalkyl esters such as monocyclopentyl fumarate, monocyclohexyl fumarate and monocycloheptyl fumarate; Monomethylcyclopentyl fumarate, fumaric acid monoalkyl cycloalkyl fumarate such as monoethylcyclohexyl; monoalkyl citraconic acid esters such as monomethyl citraconate, monoethyl citraconate, monopropyl citraconate, mono-n-butyl citraconate; monocyclopentyl citraconate, monocyclohexyl citraconate, citraconic acid monocycloalkyl esters such as monocycloheptyl citraconic acid; citraconic acid monoalkylcycloalkyl esters such as monomethylcyclopentyl citraconic acid, monoethylcyclohexyl citraconic acid; monomethyl itaconate, monoethyl itaconate, monopropyl itaconate, mono itaconate Itaconic acid monoalkyl esters such as n-butyl; Itaconic acid monocycloalkyl esters such as monocyclopentyl itaconate, monocyclohexyl itaconate and monocycloheptyl itaconate; Mono itaconic acid such as monomethylcyclopentyl itaconate and monoethylcyclohexyl itaconate Alkyl cycloalkyl ester; and the like.

The α,β-ethylenically unsaturated dicarboxylic acid monoester monomers may be used singly or in combination. Among these, α,β-ethylenically unsaturated dicarboxylic acid monoalkyl ester monomers are more preferred, and maleic acid monoalkyl esters and fumaric acid monoalkyl esters are more preferred, and mono-n-butyl maleate and mono-n fumarate are more preferred. -Butyl is particularly preferred. The number of carbon atoms in the alkyl group of the alkyl ester is preferably 2 to 8.

The content of α,β-ethylenically unsaturated dicarboxylic acid monoester monomer units is 0.1 to 20% by weight, preferably 0.5 to 15% by weight, based on the total monomer units. More preferably 1 to 10% by weight. If the content of the α,β-ethylenically unsaturated dicarboxylic acid monoester monomer units is too low, the compression set resistance of the obtained crosslinked rubber deteriorates. On the other hand, if it is too large, the rubber elasticity becomes inferior.

Further, the carboxyl group-containing nitrile rubber used in the present invention preferably further contains a conjugated diene monomer unit so that the resulting crosslinked rubber has rubber elasticity.

The conjugated diene monomer forming the conjugated diene monomer unit includes 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, chloroprene, and the like having 4 to 4 carbon atoms. 6 conjugated diene monomers are preferred, 1,3-butadiene and isoprene are more preferred, and 1,3-butadiene is particularly preferred. Conjugated diene monomers may be used singly or in combination.

The content of conjugated diene monomer units (including hydrogenated portions) is preferably 15 to 70% by weight, more preferably 26 to 60% by weight, and still more preferably 35 to 50% by weight. By setting the content of the conjugated diene monomer unit within the above range, the resulting crosslinked rubber can have excellent rubber elasticity while maintaining good heat resistance and chemical resistance stability.

In addition, the carboxyl group-containing nitrile rubber used in the present invention further contains α,β-ethylenically unsaturated monocarboxylic acid ester monomer units from the viewpoint of further increasing the cold resistance of the resulting rubber crosslinked product. is preferred.

The α,β-ethylenically unsaturated monocarboxylic acid ester monomer is not particularly limited, but examples include α,β-ethylenically unsaturated monocarboxylic acid alkyl ester monomers, α,β-ethylenically unsaturated monocarboxylic acid alkoxyalkyl ester monomer, α,β-ethylenically unsaturated monocarboxylic acid aminoalkyl ester monomer, α,β-ethylenically unsaturated monocarboxylic acid hydroxyalkyl ester monomer, α,β- and ethylenically unsaturated monocarboxylic acid fluoroalkyl ester monomers.
Among these, α,β-ethylenically unsaturated monocarboxylic acid alkyl ester monomers or α,β-ethylenically unsaturated monocarboxylic acid alkoxyalkyl ester monomers are preferable.

The alkyl ester monomer of the α,β-ethylenically unsaturated monocarboxylic acid preferably has an alkyl group having 3 to 10 carbon atoms, and an alkyl group having 3 to 8 carbon atoms is preferable. Those having an alkyl group having 4 to 6 carbon atoms are more preferable.

Specific examples of α,β-ethylenically unsaturated monocarboxylic acid alkyl ester monomers include alkyl acrylate monomers such as propyl acrylate, n-butyl acrylate, n-pentyl acrylate, and 2-ethylhexyl acrylate. monomers; cycloalkyl acrylate monomers such as cyclopentyl acrylate and cyclohexyl acrylate; alkyl cycloalkyl acrylate monomers such as methylcyclopentyl acrylate, ethylcyclopentyl acrylate and methylcyclohexyl acrylate; propyl methacrylate , n-butyl methacrylate, n-pentyl methacrylate, n-octyl methacrylate and other methacrylic acid alkyl ester monomers; cyclopentyl methacrylate, cyclohexyl methacrylate and other methacrylic acid cycloalkyl ester monomers; methylcyclopentyl methacrylate , ethylcyclopentyl methacrylate, methylcyclohexyl methacrylate and other methacrylic acid alkyl cycloalkyl ester monomers; propyl crotonate, n-butyl crotonate, 2-ethylhexyl crotonate and other croton acid alkyl ester monomers; cyclopentyl crotonate , cyclohexyl crotonate, cyclooctyl crotonate, and other cycloalkyl ester monomers of crotonate; alkylcycloalkyl crotonate monomers, such as methylcyclopentyl crotonate and methylcyclohexyl crotonate; and the like.

The α,β-ethylenically unsaturated monocarboxylic acid alkoxyalkyl ester monomer preferably has an alkoxyalkyl group having 2 to 8 carbon atoms as an alkoxyalkyl group, and has 2 to 6 carbon atoms. Those having a certain alkoxyalkyl group are more preferred, and those having an alkoxyalkyl group having 2 to 4 carbon atoms are even more preferred.

Specific examples of α,β-ethylenically unsaturated monocarboxylic acid alkoxyalkyl ester monomers include methoxymethyl acrylate, methoxyethyl acrylate, ethoxymethyl acrylate, ethoxyethyl acrylate, n-propoxyethyl acrylate, alkoxyalkyl ester monomers such as i-propoxyethyl acrylate, n-butoxyethyl acrylate, i-butoxyethyl acrylate, t-butoxyethyl acrylate, methoxypropyl acrylate, methoxybutyl acrylate; methacrylic acid Methoxymethyl, methoxyethyl methacrylate, ethoxymethyl methacrylate, ethoxyethyl methacrylate, n-propoxyethyl methacrylate, i-propoxyethyl methacrylate, n-butoxyethyl methacrylate, i-butoxyethyl methacrylate, t-methacrylate methacrylic acid alkoxyalkyl ester monomers such as butoxyethyl, methoxypropyl methacrylate, and methoxybutyl methacrylate;

Among these α,β-ethylenically unsaturated monocarboxylic acid ester monomers, acrylic acid alkyl ester monomers and acrylic acid alkoxyalkyl ester monomers are preferred because they can further enhance the effect of improving cold resistance. is preferred, n-butyl acrylate and methoxyethyl acrylate are more preferred, and n-butyl acrylate is particularly preferred.

The content of α,β-ethylenically unsaturated monocarboxylic acid ester monomer units in the carboxyl group-containing nitrile rubber used in the present invention is preferably 10 to 50% by weight based on the total monomer units. Yes, more preferably 15 to 54% by weight, more preferably 20 to 42% by weight. By setting the content of the α,β-ethylenically unsaturated monocarboxylic acid ester monomer unit within the above range, the cross-linked rubber obtained can have good water resistance and can be further enhanced in cold resistance. .

Further, the carboxyl group-containing nitrile rubber used in the present invention includes α,β-ethylenically unsaturated nitrile monomer units, α,β-ethylenically unsaturated dicarboxylic acid monoester monomer units, and, if necessary, In addition to the conjugated diene monomer units and the α,β-ethylenically unsaturated monocarboxylic acid ester monomer units to be copolymerized, other monomers copolymerizable with the monomers forming them It may contain units. Such other monomers include α,β-ethylenically unsaturated monocarboxylic acid monomers, α,β-ethylenically unsaturated polycarboxylic acid monomers (α,β-ethylenically unsaturated excluding those corresponding to dicarboxylic acid monoester monomers), ethylene, α-olefin monomers, aromatic vinyl monomers, fluorine-containing vinyl monomers, copolymerizable anti-aging agents, etc. .

The α,β-ethylenically unsaturated monocarboxylic acid monomers include acrylic acid, methacrylic acid, ethylacrylic acid, crotonic acid, cinnamic acid and the like.

Examples of α,β-ethylenically unsaturated polycarboxylic acid monomers include butenedioic acids such as fumaric acid and maleic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, allylmalonic acid, and teraconic acid. Examples of anhydrides of α,β-unsaturated polycarboxylic acids include maleic anhydride, itaconic anhydride, and citraconic anhydride.

The α-olefin monomer preferably has 3 to 12 carbon atoms, such as propylene, 1-butene, 4-methyl-1-pentene, 1-hexene and 1-octene.

Examples of aromatic vinyl monomers include styrene, α-methylstyrene, vinylpyridine and the like.

Fluorine-containing vinyl monomers include fluoroethyl vinyl ether, fluoropropyl vinyl ether, o-trifluoromethylstyrene, vinyl pentafluorobenzoate, difluoroethylene and tetrafluoroethylene.

Copolymerizable antioxidants include N-(4-anilinophenyl) acrylamide, N-(4-anilinophenyl) methacrylamide, N-(4-anilinophenyl) cinnamamide, N-(4-anilino 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 of multiple types. The content of other monomer units is preferably 50% by weight or less, more preferably 40% by weight or less, still more preferably 10% by weight, based on the total monomer units constituting the carboxyl group-containing nitrile rubber. It is below.

The iodine value of the carboxyl group-containing nitrile rubber used in the present invention is preferably 120 or less, more preferably 60 or less, even more preferably 40 or less, and particularly preferably 30 or less. By setting the iodine value to 120 or less, it is possible to improve the compression set resistance, heat resistance and ozone resistance of the resulting crosslinked rubber.

The carboxyl group-containing nitrile rubber used in the present invention has a Mooney viscosity [ML1+4, 100° C.] of preferably 15-200, more preferably 30-100, still more preferably 45-90.

The carboxyl group content in the carboxyl group-containing nitrile rubber used in the present invention, that is, the number of moles of carboxyl groups per 100 g of the carboxyl group-containing nitrile rubber is preferably 5×10 ⁻⁴ to 5×10 ⁻¹ ephr, more preferably is 1×10 ⁻³ to 1×10 ⁻¹ ephr, particularly preferably 5×10 ⁻³ to 6×10 ⁻² ephr. By setting the carboxyl group content within the above range, the compression set resistance of the obtained rubber crosslinked product is appropriately suppressed while appropriately suppressing deterioration of processability when a polyvalent amine compound is blended as a crosslinker. can be enhanced.

Further, the carboxyl group-containing nitrile rubber used in the present invention has a total content of sodium, calcium and magnesium in the carboxyl group-containing nitrile rubber of 130 to 1000 ppm by weight, and a sodium content of 600 ppm by weight or less. is controlled by

The total content of sodium, calcium and magnesium in the carboxyl group-containing nitrile rubber used in the present invention is 130 to 1000 ppm by weight, preferably 180 to 800 ppm by weight, more preferably 230 to 650 ppm by weight. be. If the total content of sodium, calcium and magnesium is too low, the resulting cross-linked rubber will be inferior in compression set resistance, and if the total content of sodium, calcium and magnesium is too high. However, the resulting cross-linked rubber product is inferior in resistance to compression set.

The total content of sodium, calcium, and magnesium in the carboxyl group-containing nitrile rubber can be determined, for example, by adding sulfuric acid or nitric acid to the carboxyl group-containing nitrile rubber, heating it, decomposing it in a wet process, and then diluting it appropriately. can be measured by high frequency inductively coupled plasma atomic emission spectrometry (ICP/AES) using an internal standard calibration curve method. Specifically, the weight of each of sodium, calcium, and magnesium contained in the carboxyl group-containing nitrile rubber is measured, the total weight of these sodium, calcium, and magnesium is calculated, and the calculated total weight and carboxyl It can be determined from the weight of the group-containing nitrile rubber. Furthermore, at this time, the respective contents of sodium, calcium, and magnesium contained in the carboxyl group-containing nitrile rubber and the total content of calcium and magnesium can also be determined at the same time.

Further, in the present invention, as the carboxyl group-containing nitrile rubber, the total content of sodium, calcium, and magnesium in the carboxyl group-containing nitrile rubber is within the above range, and the sodium content is 600 ppm by weight or less. A controlled one is used, and the content of sodium is preferably 300 ppm by weight or less, more preferably 130 ppm by weight or less. If the sodium content is too high, the resulting crosslinked rubber will be inferior in LLC resistance. Although the lower limit of the sodium content is not particularly limited, it is preferably 10 ppm by weight or more, more preferably 25 ppm by weight or more, and still more preferably 40 ppm by weight or more.

The content of calcium and magnesium in the carboxyl group-containing nitrile rubber used in the present invention is not particularly limited, but the total content of calcium and magnesium is preferably 100 to 1000 ppm by weight, and more preferably. is 110 to 650 ppm by weight, more preferably 120 to 450 ppm by weight. The calcium content in the carboxyl group-containing nitrile rubber is preferably 700 ppm by weight or less, more preferably 550 ppm by weight or less, and even more preferably 400 ppm by weight or less, and the lower limit of the calcium content is preferably 50 ppm by weight or more. The content of magnesium in the carboxyl group-containing nitrile rubber is preferably 700 ppm by weight or less, more preferably 350 ppm by weight or less, and even more preferably 100 ppm by weight or less, and the lower limit of the magnesium content is preferably 5 ppm by weight or more. By setting the contents of calcium and magnesium within the above ranges, the resulting crosslinked rubber can be made more excellent in compression set resistance and LLC resistance.

Since the carboxyl group-containing nitrile rubber used in the present invention contains sodium, calcium, and magnesium in the above-described contents, it can also be said that it is a composition containing these in the above-described contents.

The contents of sodium, calcium, and magnesium contained in the carboxyl group-containing nitrile rubber are determined, for example, when the carboxyl group-containing nitrile rubber is obtained by emulsion polymerization, when the obtained carboxyl group-containing nitrile rubber latex is coagulated. It can be adjusted by selecting the type of coagulating salt used for or adjusting the amount of coagulating salt. Alternatively, it can be adjusted by a method of adjusting water washing conditions after coagulation, or a method of adjusting the amounts of sodium, calcium, and magnesium that are unavoidably mixed in the manufacturing process. When carboxyl group-containing nitrile rubbers having different monomer compositions are used in combination, the contents of sodium, calcium, and magnesium in the entire mixture of carboxyl group-containing nitrile rubbers having different monomer compositions should be within the above ranges. (The same applies to the chloride ion content described later.).

The chloride ion content in the carboxyl group-containing nitrile rubber used in the present invention is preferably 50 to 600 ppm by weight, more preferably 100 to 400 ppm by weight, still more preferably 150 to 250 ppm by weight. That is, the present invention may be a composition containing a carboxyl group-containing nitrile rubber and a chloride. Compression set resistance can be made more excellent. The chloride ion content in the carboxyl group-containing nitrile rubber can be determined, for example, by immersing the carboxyl group-containing nitrile rubber in a solvent capable of dissolving the carboxyl group-containing nitrile rubber, such as methyl ethyl ketone, and completely dissolving the rubber. It can be measured by performing potentiometric titration.

The chloride ion content contained in the carboxyl group-containing nitrile rubber used in the present invention is, for example, when the carboxyl group-containing nitrile rubber is obtained by emulsion polymerization, when the latex of the obtained carboxyl group-containing nitrile rubber is coagulated. It can be adjusted by selecting the type of coagulating salt used for or adjusting the amount of coagulating salt. Alternatively, it can be adjusted by a method of adjusting water washing conditions after coagulation, or a method of adjusting the amount of chloride ions that are unavoidably mixed in the manufacturing process.

The method for producing the carboxyl group-containing nitrile rubber used in the present invention is not particularly limited. It can be produced by hydrogenating the bond. In emulsion polymerization, in addition to emulsifiers, polymerization initiators and molecular weight modifiers, commonly used auxiliary materials for polymerization can be used.

Examples of emulsifiers include, but are not limited to, nonionic emulsifiers such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenol ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan alkyl esters; myristic acid, palmitic acid, and oleic acid. and salts of fatty acids such as linolenic acid, alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate, polycondensates of naphthalenesulfonates and formalin, higher alcohol sulfate salts, anionic emulsifiers such as alkylsulfosuccinates; , β-unsaturated carboxylic acid sulfoesters, α,β-unsaturated carboxylic acid sulfate esters, and copolymerizable emulsifiers such as sulfoalkylaryl ethers. The amount of the emulsifier to be added is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, per 100 parts by weight of the monomer used for polymerization.

The polymerization initiator is not particularly limited as long as it is a radical initiator. Potassium persulfate, sodium persulfate, ammonium persulfate, potassium perphosphate, inorganic peroxides such as hydrogen peroxide; cumene hydroperoxide, p- Menthane hydroperoxide, di-t-butyl peroxide, t-butyl cumyl peroxide, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, dibenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide , organic peroxides such as t-butyl peroxyisobutyrate; azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, and methyl azobisisobutyrate; be able to. These polymerization initiators can be used alone or in combination of two or more. Inorganic or organic peroxides are preferred as polymerization initiators. 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. Furthermore, a chelating agent such as sodium ethylenediaminetetraacetate iron sodium tetrahydrate and a builder such as sodium carbonate and sodium sulfate can be used in combination. The amount of the polymerization initiator to be added is preferably 0.01 to 2 parts by weight per 100 parts by weight of the monomer used for polymerization.

Water is usually used as a medium for emulsion polymerization. The amount of water is preferably 80 to 500 parts by weight, more preferably 80 to 300 parts by weight, per 100 parts by weight of the monomer used for polymerization.

In the emulsion polymerization, additional polymerization materials such as a stabilizer, a dispersant, a pH adjuster, an oxygen absorber, and a particle size adjuster can be used as necessary. When these are used, the type and amount used are not particularly limited.

In addition, hydrogenation (hydrogenation reaction) of the obtained copolymer is carried out, if necessary. Hydrogenation may be carried out by a known method, but the aqueous layer hydrogenation method is preferred because the total content of sodium, calcium, and magnesium and the chloride ion content in the carboxyl group-containing nitrile rubber obtained can be suitably controlled. is preferred. In addition, as the water layer hydrogenation method, there is a direct water layer hydrogenation method in which hydrogen is supplied to a reaction system in the presence of a hydrogenation catalyst to hydrogenate, and a method in which reduction is performed in the presence of an oxidizing agent, a reducing agent and an activator. Among these, the direct aqueous hydrogenation method is preferred.

In the aqueous layer direct hydrogenation method, the concentration of the copolymer in the aqueous layer (concentration in the latex state) is preferably 40% by weight or less in order to prevent aggregation. The hydrogenation catalyst is not particularly limited as long as it is a compound that is difficult to decompose with water. Specific examples of palladium catalysts include palladium metal; palladium oxide; palladium hydroxide; palladium salts of carboxylic acids such as formic acid, acetic acid, propionic acid, lauric acid, succinic acid, oleic acid and phthalic acid; palladium chlorides such as cyclooctadiene)palladium, dichloro(norbornadiene)palladium and ammonium hexachloropalladium(IV); iodides such as palladium iodide; and palladium sulfate dihydrate. Among these, palladium metal, palladium salts of carboxylic acids, palladium chloride, dichloro(norbornadiene)palladium and ammonium hexachloropalladium(IV) are particularly preferred. The amount of the hydrogenation catalyst used may be appropriately determined, but is preferably 5 to 6000 ppm by weight, more preferably 10 to 4000 ppm by weight, relative to the copolymer obtained by polymerization.

In the aqueous layer direct hydrogenation method, the hydrogenation catalyst in the latex is removed after the completion of the hydrogenation reaction. As a method, for example, a method of adding an adsorbent such as activated carbon or an ion exchange resin to adsorb the hydrogenation catalyst under stirring, and then filtering or centrifuging the latex can be adopted. Alternatively, a method of adding an oxidizing agent or reducing agent and a complexing agent to complex the hydrogenation catalyst and then filtering or centrifuging the latex can be adopted. It is also possible to leave the hydrogenation catalyst in the latex without removing it.

In the present invention, a coagulant is added to the hydrogenated latex thus obtained to coagulate the latex, thereby obtaining water-containing crumbs of carboxyl group-containing nitrile rubber. The coagulant used for coagulation is not particularly limited, but includes sodium chloride, potassium chloride, calcium chloride, magnesium chloride, sodium sulfate, magnesium sulfate, aluminum sulfate, sodium nitrate, barium chloride and the like. The amount of the coagulant used may be appropriately selected according to the type of coagulant used and the amount of sodium, calcium, magnesium, and chloride ions to be contained in the finally obtained carboxyl group-containing nitrile rubber. is preferably 0.5 to 200 parts by weight, more preferably 1 to 100 parts by weight, still more preferably 2 to 50 parts by weight, and particularly preferably 3 to 35 parts by weight. The coagulant is preferably a chloride, more preferably a metal chloride such as sodium chloride, potassium chloride, calcium chloride and magnesium chloride. When chloride is used as a coagulant, chloride alone may be used, or chloride and a coagulant other than chloride may be used in combination. Furthermore, chlorides may be used singly or in combination of multiple kinds. The amount of chloride used may be appropriately selected according to the type of chloride used and the amounts of sodium, calcium, magnesium and chloride ions to be contained in the finally obtained carboxyl group-containing nitrile rubber. is preferably 0.5 to 200 parts by weight, more preferably 1 to 100 parts by weight, still more preferably 2 to 50 parts by weight, and particularly preferably 3 to 35 parts by weight. When adding a coagulant, it may be dissolved in water and added in the form of an aqueous coagulant solution. And an acid such as sulfuric acid (aqueous solution) may be added to adjust the pH to preferably 1-4, more preferably 2-3.

Then, the water-containing crumb obtained by coagulation is washed with water and dried to obtain the carboxyl group-containing nitrile rubber of the present invention. The carboxyl group-containing nitrile rubber of the present invention is preferably different from the carboxyl group-containing nitrile rubber contained in the latex. That is, the carboxyl group-containing nitrile rubber of the present invention is preferably dry rubber, more preferably rubber having a water content of 1% by weight or less. Washing conditions such as the number of times of washing can be appropriately selected according to the amount of sodium, calcium, magnesium, and chloride ions to be contained in the finally obtained carboxyl group-containing nitrile rubber. It is preferable to wash 1 to 6 times, preferably with 500 to 2000 parts by weight of water, per 100 parts by weight of crumbs.

An antiaging agent can also be added to the oil layer or water layer before solidification. The antioxidant is not particularly limited, but 2,6-di-t-butyl-4-cresol (Antage BHT, manufactured by Kawaguchi Chemical Industry Co., Ltd.), 2,2'-methylenebis(4-methyl-6-tert- Butylphenol) (Sundant 2246, manufactured by Sanshin Chemical Industry Co., Ltd.), bis(3,5-di-tert-butyl-4-hydroxybenzyl) sulfide (Sandant 103, manufactured by Sanshin Chemical Industry Co., Ltd.), pentaerythritol tetrakis [ 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (Irganox 1010, manufactured by BASF Japan), octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (Irganox 1076, manufactured by BASF Japan), isooctyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (Irganox 1135, manufactured by BASF Japan), hexamethylene bis [3-(3, 5-di-tert-butyl-4-hydroxyphenyl) propionate] (Irganox 259, manufactured by BASF Japan), 4,6-bis(octylthiomethyl)-o-cresol (Irganox 1520L, manufactured by BASF Japan), etc. can be used.

The nitrile rubber composition of the present invention further contains a silicon-containing filler in addition to the carboxyl group-containing nitrile rubber described above. According to the present invention, when a rubber crosslinked product is obtained by blending a silicon-containing filler into the above-described carboxyl group-containing nitrile rubber, the obtained rubber crosslinked product is improved in LLC resistance and compression set resistance. It is possible to make it excellent in nature.

The filler containing silicon is not particularly limited as long as it contains a silicon atom, and examples thereof include silica and silicates.

Examples of silica include natural silica such as quartz powder and silica powder; synthetic silica such as silicic anhydride (silica gel, aerosil, etc.) and hydrous silicic acid; Synthetic silica is preferred from the viewpoint of higher effects. The specific surface area of silica as determined by the BET method is not particularly limited, but is preferably 10 to 600 m ² /g, more preferably 50 to 350 m ² /g, still more preferably 100 to 200 m ² /g.

Although the silicate is not particularly limited, it is preferably a silicate of an element of Group 2 or Group 13 of the periodic table, and more preferably a compound represented by the following general formula (1).
_{MO.xSiO2.mH2O (} 1)
(In the above general formula (1), M represents an element of Group 2 of the periodic table or an element of Group 13 of the periodic table, x is a positive real number of 8 or less, and m is 0 or a positive real number of 12 or less. is.)

In the above general formula (1), elements of Group 2 of the periodic table that constitute M include magnesium, calcium, strontium, barium, etc. Among these, magnesium is preferable. Further, in the general formula (1), examples of elements belonging to Group 13 of the periodic table that constitute M include boron and aluminum, and among these, aluminum is preferable.

Specific examples of the compound represented by the general formula (1) include magnesium silicate, magnesium silicate hydrate, calcium silicate, calcium silicate hydrate, boron silicate, boron silicate hydrate, aluminum silicate, and aluminum silicate water. Among them, magnesium silicate and aluminum silicate are more preferable, and aluminum silicate is particularly preferable.

Moreover, as the silicate, it is preferable to use a silicate having a surface-treated surface because the dispersibility in the nitrile rubber composition can be further enhanced, thereby further enhancing the effect of adding the silicate. A surface treatment agent for surface treatment is not particularly limited, but a silane coupling agent is preferably used.

Specific examples of silane coupling agents include γ-mercaptopropyltrimethoxysilane, γ-mercaptomethyltrimethoxysilane, γ-mercaptomethyltriethoxysilane, γ-mercaptohexamethyldisilazane, bis(3-triethoxysilylpropyl ) tetrasulfane, bis(3-triethoxysilylpropyl)disulfane and other sulfur-containing silane coupling agents; γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, β-(3 Epoxy group-containing silane coupling agents such as ,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane; N-(β-aminoethyl)-γ- aminopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3- amino group-containing silane coupling agents such as aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane; γ-methacrylic roxypropyltrimethoxysilane, γ-methacryloxypropyltris(β-methoxyethoxy)silane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, 3- (Meth)acryloxy group-containing silane coupling agents such as acryloxypropyltrimethoxysilane; vinyl groups such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, vinyltrichlorosilane, vinyltriacetoxysilane, etc. Containing silane coupling agent; chloropropyl group-containing silane coupling agent such as 3-chloropropyltrimethoxysilane; isocyanate group-containing silane coupling agent such as 3-isocyanatopropyltriethoxysilane; styryl such as p-styryltrimethoxysilane group-containing silane coupling agents; ureido group-containing silane coupling agents such as 3-ureidopropyltriethoxysilane; allyl group-containing silane coupling agents such as diallyldimethylsilane; alkoxy group-containing silane coupling agents such as tetraethoxysilane; phenyl group-containing silane coupling agents such as diphenyldimethoxysilane; fluoro group-containing silane coupling agents such as trifluoropropyltrimethoxysilane; alkyl group-containing silane coupling agents such as isobutyltrimethoxysilane and cyclohexylmethyldimethoxysilane; mentioned. These can be used singly or in combination. Among these, a vinyl group-containing silane coupling agent is preferable from the viewpoint of a high effect of improving dispersibility.

Although the average particle size of the silicate is not particularly limited, it is preferably 0.01 to 100 μm, more preferably 0.05 to 50 μm.

The content of the silicon-containing filler in the nitrile rubber composition of the present invention is preferably 10 to 100 parts by weight, more preferably 15 to 80 parts by weight, per 100 parts by weight of the carboxyl group-containing nitrile rubber. More preferably 20 to 60 parts by weight. By setting the content of the silicon-containing filler within the above range, the effect of improving LLC resistance and compression set resistance can be further enhanced.

In addition, the nitrile rubber composition of the present invention further enhances the dispersibility of the silicon-containing filler, thereby further enhancing the LLC resistance of the resulting rubber crosslinked product. Further, it is preferable to contain.

The modified silicone oil may be any silicone oil having a modifying group, and the modifying group is not particularly limited, but it is preferably a modifying group capable of reacting with the carboxyl group constituting the carboxyl group-containing nitrile rubber described above. Examples of such reactive groups include hydroxyl group, amino group, mercapto group, epoxy group, carboxyl group, acrylic group (-OOC-CH=CH ₂ , where -OOC- represents an oxycarbonyl group), and methacrylic group ( -OOC-C(CH ₃ )=CH ₂ , where -OOC- represents an oxycarbonyl group), and among these, amino group, epoxy group, A mercapto group is more preferred, an amino group and an epoxy group are more preferred, and an amino group is particularly preferred. The epoxy group is not particularly limited as long as it is a group having an oxirane ring. For example, in addition to those having an oxirane ring in a linear hydrocarbon group, those having an oxirane ring in a cyclic hydrocarbon group etc. can also be used.

As the modified silicone oil, for example, those represented by the following general formula (2), the following general formula (3), the following general formula (4), the following general formula (5), or the following general formula (6) are suitable. can be used for Among these, those represented by the following general formula (2) are preferable, and from the viewpoint of their high blending effect, among those represented by the following general formula (2), those represented by the following general formula (7) is particularly preferred.

（上記一般式（２）中、Ｒ^１は、炭素数１～３０、好ましくは炭素数１～１０の主鎖中および／または側鎖中にヘテロ原子を有していてもよい炭化水素基、Ｘ^１は、上述したいずれかの反応性基、ｍは、１～１０，０００の整数、ｎは、１～１０，０００の整数である。）

(In general formula (2) above, R ¹ is a hydrocarbon group having 1 to 30 carbon atoms, preferably 1 to 10 carbon atoms and optionally having a hetero atom in the main chain and/or side chain, X ¹ is any reactive group described above, m is an integer of 1 to 10,000, and n is an integer of 1 to 10,000.)

（上記一般式（３）中、Ｒ^２、Ｒ^３は、それぞれ独立して、炭素数１～３０、好ましくは炭素数１～１０の主鎖中および／または側鎖中にヘテロ原子を有していてもよい炭化水素基、Ｘ^２、Ｘ^３は、それぞれ独立して、上述したいずれかの反応性基、ｐは、１～１０，０００の整数である。Ｒ^２、Ｒ^３は同一でもよいし、互いに異なっていてもよい。また、Ｘ^２、Ｘ^３は同一でもよいし、互いに異なっていてもよい。）

(In general formula (3) above, R ² and R ³ each independently have a heteroatom in the main chain and/or side chain having 1 to 30 carbon atoms, preferably 1 to 10 carbon atoms. X ² and X ³ are each independently any of the reactive groups described above, p is an integer of 1 to 10,000, and R ² and R ³ may be the same. X ² and X ³ may be the same or different.)

（上記一般式（４）中、Ｒ^４、Ｒ^５、Ｒ^６は、それぞれ独立して、炭素数１～３０、好ましくは炭素数１～１０の主鎖中および／または側鎖中にヘテロ原子を有していてもよい炭化水素基、Ｘ^４、Ｘ^５、Ｘ^６は、それぞれ独立して、上述したいずれかの反応性基、ｑは、１～１０，０００の整数、ｒは、１～１０，０００の整数である。Ｒ^４、Ｒ^５、Ｒ^６は同一でもよいし、互いに異なっていてもよい。また、Ｘ^４、Ｘ^５、Ｘ^６は同一でもよいし、互いに異なっていてもよい。）

(In general formula (4) above, each of R ⁴ , R ⁵ and R ⁶ independently has 1 to 30 carbon atoms, preferably 1 to 10 carbon atoms in the main chain and/or in the side chain. X ⁴ , X ⁵ and X ⁶ are each independently any of the reactive groups described above, q is an integer of 1 to 10,000, r is 1 is an integer of up to 10,000, R ⁴ , R ⁵ and R ⁶ may be the same or different, and X ⁴ , X ⁵ and X ⁶ may be the same or different; is also good.)

（上記一般式（５）中、Ｒ^７は、炭素数１～３０、好ましくは炭素数１～１０の主鎖中および／または側鎖中にヘテロ原子を有していてもよい炭化水素基、Ｘ^７は、上述したいずれかの反応性基、ｓは、１～１０，０００の整数である。）

(In general formula (5) above, R ⁷ is a hydrocarbon group having 1 to 30 carbon atoms, preferably 1 to 10 carbon atoms and optionally having a heteroatom in the main chain and/or side chain, X ⁷ is any of the reactive groups described above, and s is an integer from 1 to 10,000.)

（上記一般式（６）中、Ｒ^８、Ｒ^９は、それぞれ独立して、炭素数１～３０、好ましくは炭素数１～１０の主鎖中および／または側鎖中にヘテロ原子を有していてもよい炭化水素基、Ｘ^８、Ｘ^９は、それぞれ独立して、上述したいずれかの反応性基、ｔは、１～１０，０００の整数、ｕは、１～１０，０００の整数である。Ｒ^８、Ｒ^９は同一でもよいし、互いに異なっていてもよい。また、Ｘ^８、Ｘ^９は同一でもよいし、互いに異なっていてもよい。）

(In the above general formula (6), R ⁸ and R ⁹ each independently have a heteroatom in the main chain and/or side chain having 1 to 30 carbon atoms, preferably 1 to 10 carbon atoms. each of the optionally-substituted hydrocarbon groups X ⁸ and X ⁹ is independently any of the reactive groups described above, t is an integer of 1 to 10,000, u is an integer of 1 to 10,000 (R ⁸ and R ⁹ may be the same or different, and X ⁸ and X ⁹ may be the same or different.)

（上記一般式（７）中、Ｒ^１、ｍ、ｎは、それぞれ上記一般式（１）と同じ。）

(In general formula (7) above, R ¹ , m, and n are the same as in general formula (1) above.)

The weight average molecular weight of the modified silicone oil is preferably 200 to 100,000, more preferably 200 to 50,000, still more preferably 200 to 20,000. When the weight-average molecular weight of the modified silicone oil is within the above range, the effect of adding the modified silicone oil can be further enhanced while keeping the viscosity within a range in which handling is good. The dynamic viscosity (20° C., unit: mm ² /s) of the modified silicone oil is preferably from 10 to 10,000, more preferably from 20 to 1,000, and particularly preferably from 20 to 500.

The content of the modified silicone oil in the nitrile rubber composition of the present invention is preferably 0.5 to 10 parts by weight, more preferably 1 to 8 parts by weight, based on 100 parts by weight of the carboxyl group-containing nitrile rubber. It is preferably 2 to 6 parts by weight. By setting the content of the modified silicone oil within the above range, the LLC resistance of the resulting crosslinked rubber can be further enhanced.

Moreover, the nitrile rubber composition of the present invention preferably further contains a polyvalent amine compound. A polyvalent amine compound is a compound that acts as a cross-linking agent. Therefore, by blending a polyvalent amine compound, the nitrile rubber composition of the present invention can be made into a cross-linkable rubber composition.

The polyvalent amine compound is not particularly limited as long as it is in the form of a compound having two or more amino groups, or a compound having two or more amino groups upon cross-linking. A compound in which a plurality of hydrogen atoms of a group hydrocarbon is substituted with an amino group or a hydrazide structure (a structure represented by —CONHNH ₂ , CO represents a carbonyl group), and a compound in the form of that compound during crosslinking are preferred. .

Specific examples of polyvalent amine compounds include aliphatic polyvalent compounds such as hexamethylenediamine, hexamethylenediamine carbamate, N,N-dicinnamylidene-1,6-hexanediamine, tetramethylenepentamine, and hexamethylenediamine cinnamaldehyde adducts. Amines; 4,4-methylenedianiline, m-phenylenediamine, 4,4-diaminodiphenyl ether, 3,4-diaminodiphenyl ether, 4,4-(m-phenylenediisopropylidene)dianiline, 4,4-(p -phenylenediisopropylidene)dianiline, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4-diaminobenzanilide, 4,4-bis(4-aminophenoxy)biphenyl, m-xyl Aromatic polyvalent amines such as diamine, p-xylylenediamine and 1,3,5-benzenetriamine; , oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutamic acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, suberic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, brassylic acid dihydrazide, dodecanedioic acid dihydrazide, acetone dicarboxylic acid dihydrazide, polyvalent hydrazides such as fumaric acid dihydrazide, maleic acid dihydrazide, itaconic acid dihydrazide, trimellitic acid dihydrazide, 1,3,5-benzenetricarboxylic acid dihydrazide, aconitic acid dihydrazide, and pyromellitic acid dihydrazide; Among these, aliphatic polyamines and aromatic polyamines are preferred, and hexamethylenediamine carbamate and 2,2-bis[ 4-(4-Aminophenoxy)phenyl]propane is more preferred, and hexamethylenediamine carbamate is particularly preferred.

Although the content of the polyvalent amine compound in the nitrile rubber composition of the present invention is not particularly limited, it is preferably 0.1 to 10 parts by weight, more preferably 0.1 to 10 parts by weight, per 100 parts by weight of the carboxyl group-containing nitrile rubber. 2 to 5 parts by weight.

When the nitrile rubber composition of the present invention contains a polyvalent amine compound, it preferably further contains a basic cross-linking accelerator.
Specific examples of basic cross-linking accelerators include 1,8-diazabicyclo[5,4,0]undecene-7 (hereinafter sometimes abbreviated as “DBU”), 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-ethylimidazole, 1-methyl-2-methoxyimidazole, 1-methyl-2-ethoxyimidazole, 1-methyl-4 -methoxyimidazole, 1-methyl-2-methoxyimidazole, 1-ethoxymethyl-2-methylimidazole, 1-methyl-4-nitroimidazole, 1,2-dimethyl-5-nitroimidazole, 1,2-dimethyl-5 -aminoimidazole, 1-methyl-4-(2-aminoethyl)imidazole, 1-methylbenzimidazole, 1-methyl-2-benzylbenzimidazole, 1-methyl-5-nitrobenzimidazole, 1-methylimidazoline, 1 ,2-dimethylimidazoline, 1,2,4-trimethylimidazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-phenylimidazoline, 1-methyl-2-benzylimidazoline, 1-methyl-2-ethoxyimidazoline , 1-methyl-2-heptylimidazoline, 1-methyl-2-undecylimidazoline, 1-methyl-2-heptadecylimidazoline, 1-methyl-2-ethoxymethylimidazoline, 1-ethoxymethyl-2-methylimidazoline, etc. guanidine-based basic cross-linking accelerators such as tetramethylguanidine, tetraethylguanidine, diphenylguanidine, 1,3-di-ortho-tolylguanidine and orthotolylbiguanide; n-butyraldehyde Aldehydeamine-based basic cross-linking accelerators such as aniline and acetaldehyde ammonia; dicycloalkylamines such as dicyclopentylamine, dicyclohexylamine and dicycloheptylamine; N-methylcyclopentylamine, N-butylcyclopentylamine, N-heptylcyclopentylamine , N-octylcyclopentylamine, N-ethylcyclohexylamine, N-butylcyclohexylamine, N-heptylcyclohexylamine, N-octylcyclooctylamine, N-hydroxymethylcyclopentylamine, N-hydroxybutylcyclohexylamine, N-methoxyethyl Cyclopentylamine, N-ethoxybutylcyclohexylamine, N-methoxycarbonylbutylcyclopentylamine, N-methoxycarbonylheptylcyclohexylamine, N-aminopropylcyclopentylamine, N-aminoheptylcyclohexylamine, di(2-chlorocyclopentyl)amine, di secondary amine-based basic cross-linking accelerators such as (3-chlorocyclopentyl)amine; Among these, guanidine-based basic cross-linking accelerators, secondary amine-based basic cross-linking accelerators and basic cross-linking accelerators having a cyclic amidine structure are preferred, and basic cross-linking accelerators having a cyclic amidine structure are more preferred. 1,8-diazabicyclo[5,4,0]undecene-7 and 1,5-diazabicyclo[4,3,0]nonene-5 are more preferred, and 1,8-diazabicyclo[5,4,0]undecene-7 is particularly preferred. The basic cross-linking accelerator having a cyclic amidine structure may form a salt with an organic carboxylic acid, an alkylphosphoric acid, or the like. In addition, the secondary amine-based basic cross-linking accelerator may be a mixture of alcohols such as alkylene glycol and alkyl alcohol having 5 to 20 carbon atoms, and further contains an inorganic acid and / or an organic acid. You can stay. The secondary amine-based basic cross-linking accelerator and the inorganic acid and/or the organic acid may form a salt and form a complex with the alkylene glycol.

When the basic cross-linking accelerator is blended, the amount in the nitrile rubber composition of the present invention is preferably 0.1 to 20 parts by weight, more preferably 0.1 to 20 parts by weight, per 100 parts by weight of the carboxyl group-containing nitrile rubber. is 0.2 to 15 parts by weight, more preferably 0.5 to 10 parts by weight.

In addition, the nitrile rubber composition of the present invention may contain fillers other than silicon-containing fillers as long as the effects of the present invention are not impaired. Such fillers include carbon black etc. Examples of carbon black include, but are not limited to, furnace black, acetylene black, thermal black, channel black and graphite. The content of the filler other than the silicon-containing filler may be within a range that does not impair the effects of the present invention, and may be 30 parts by weight or less with respect to 100 parts by weight of the silicon-containing filler. preferable.

In addition, the nitrile rubber composition of the present invention may be blended with other compounding agents commonly used in the field of rubber processing. Examples of such compounding agents include reinforcing agents, light stabilizers, scorch inhibitors, plasticizers, processing aids, lubricants, adhesives, lubricants, flame retardants, acid acceptors, antifungal agents, and antistatic agents. , a coloring agent, a silane coupling agent, a cross-linking aid, a co-cross-linking agent, a cross-linking accelerator, a cross-linking retarder, a foaming agent, and the like. The amount of these compounding agents to be blended can be appropriately selected depending on the purpose of blending.

Although the plasticizer is not particularly limited, a trimellitic acid-based plasticizer, an ether ester-based plasticizer, or the like can be used. Specific examples include tri-2-ethylhexyl trimellitate, isononyl trimellitate, bis[2-(2-butoxyethoxy)ethyl]adipate, diheptanoate, di-2-ethylhexanoate, didecanoate, and the like. mentioned. These can be used individually by 1 type or in combination of 2 or more types.

Furthermore, the nitrile rubber composition of the present invention may contain rubbers other than the above-mentioned carboxyl group-containing nitrile rubber within a range that does not impair the effects of the present invention.
Examples of such rubber include acrylic rubber, ethylene-acrylic acid copolymer rubber, fluororubber, styrene-butadiene copolymer rubber, polybutadiene rubber, ethylene-propylene copolymer rubber, ethylene-propylene-diene terpolymer rubber. Coalescing rubber, epichlorohydrin rubber, urethane rubber, chloroprene rubber, silicone rubber, fluorosilicone rubber, chlorosulfonated polyethylene rubber, natural rubber and polyisoprene rubber.

When a rubber other than the carboxyl group-containing nitrile rubber is blended, the amount in the nitrile rubber composition is preferably 30 parts by weight or less, more preferably 20 parts by weight or less per 100 parts by weight of the carboxyl group-containing nitrile rubber. , more preferably 10 parts by weight or less.

Also, the nitrile rubber composition of the present invention is prepared by mixing the above components preferably in a non-aqueous system. Although the method for preparing the nitrile rubber composition of the present invention is not limited, usually, components other than the polyvalent amine compound and the heat-labile basic cross-linking accelerator are mixed in a Banbury mixer, an intermixer, a kneader, or the like. After primary kneading in a mixer, it can be prepared by transferring to an open roll or the like, adding a polyvalent amine compound, a heat-labile basic cross-linking accelerator, and the like, and then kneading it secondary. The primary kneading is usually carried out at a temperature of 10 to 200° C., preferably 30 to 180° C., for 1 minute to 1 hour, preferably 1 minute to 30 minutes. It is preferably carried out at a temperature of 20 to 60° C. for 1 minute to 1 hour, preferably 1 minute to 30 minutes.

<Rubber cross-linked product>
The rubber cross-linked product of the present invention is obtained by cross-linking the above-described nitrile rubber composition (cross-linkable rubber composition) of the present invention.
The rubber cross-linked product of the present invention is obtained by molding the nitrile rubber composition of the present invention into a desired shape using a molding machine such as an extruder, an injection molding machine, a compressor, a roll, etc., followed by heating. It can be produced by carrying out a cross-linking reaction and fixing the shape as a cross-linked product. In this case, the cross-linking may be performed after pre-molding, or the cross-linking may be performed at the same time as the molding. The molding temperature is usually 10-200°C, preferably 25-120°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.

Depending on the shape, size, etc. of the cross-linked rubber product, even if the surface is cross-linked, the interior may not be sufficiently cross-linked.
As a heating method, a general method used for cross-linking rubber such as press heating, steam heating, oven heating, and hot air heating may be appropriately selected.

The rubber crosslinked product of the present invention thus obtained is obtained by crosslinking the crosslinkable nitrile rubber composition of the present invention described above, and is excellent in LLC resistance and compression set resistance.
Therefore, the rubber cross-linked product of the present invention utilizes such properties and is used for O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, well head seals, shock absorber seals, long-life coolant (LLC), etc. Coolant seals and oil coolant seals that are seals for cooling liquids, seals for pneumatic equipment, and seals for sealing CFCs, fluorohydrocarbons, or carbon dioxide used in air conditioner coolers and air conditioner refrigerator compressors , sealing seals for supercritical carbon dioxide or subcritical carbon dioxide used as cleaning media for precision cleaning, rolling devices (rolling bearings, automobile hub units, automobile water pumps, linear guide devices, ball screws, etc.) seals, valves and valve seats, BOP (Blow Out Preventer), platters, and other sealing materials; cylinder head gasket, rocker cover gasket attached to the connection between the rocker cover and cylinder head, oil pan gasket attached to the connection between the oil pan and cylinder block or transmission case, positive electrode, electrolyte plate and negative electrode. Various gaskets such as gaskets for fuel cell separators and gaskets for top covers of hard disk drives; printing rolls, steel manufacturing rolls, paper manufacturing rolls, industrial rolls, office machines Various rolls such as rolls; flat belts (film core flat belts, cord flat belts, laminated flat belts, single flat belts, etc.), V belts (wrapped V belts, raw edge V belts, etc.), V-ribbed belts (single V-ribbed belts , double V-ribbed belt, wrapped V-ribbed belt, back rubber V-ribbed belt, upper cog V-ribbed belt, etc.), CVT belts, timing belts, toothed belts, conveyor belts, various belts; fuel hoses, turbo air hoses, oil hoses, Various hoses such as radiator hoses, heater hoses, water hoses, vacuum brake hoses, control hoses, air conditioner hoses, brake hoses, power steering hoses, air hoses, marine hoses, risers, flow lines; CVJ boots, propeller shaft boots, constant velocity Various boots such as joint boots and rack and pinion boots; damping rubber parts such as cushion materials, dynamic dampers, rubber couplings, air springs, anti-vibration materials, and clutch facing materials; dust covers, automotive interior materials, friction materials, tires , coated cables, shoe soles, electromagnetic wave shields, adhesives such as adhesives for flexible printed circuit boards, fuel cell separators, and a wide range of other applications such as the electronics field. In particular, the cross-linked rubber product of the present invention is excellent in LLC resistance and compression set resistance, and is therefore suitable for water-based refrigerants such as cooling liquids and antifreeze liquids used in the cooling system of internal combustion engines such as automobiles (especially LLC ) can be preferably used as a sealing material for sealing. In particular, according to the rubber crosslinked product of the present invention, in addition to being excellent in LLC resistance and compression set resistance, it is also excellent in sealing performance in a state of contact with water-based refrigerants such as cooling liquids and antifreeze liquids (especially LLC). Since it is excellent, it can be particularly preferably used as a sealing material for sealing these from this point of view as well.

The present invention will be described below based on more detailed examples, but the present invention is not limited to these examples. In the following, "parts" are by weight unless otherwise specified. Also, tests and evaluations were carried out according to the following.

[Iodine value]
The iodine value of the carboxyl group-containing nitrile rubber was measured according to JIS K6235.

[Composition of carboxyl group-containing nitrile rubber]
The content ratio of each monomer unit constituting the carboxyl group-containing nitrile rubber was measured by the following method.
That is, the content ratio of mono-n-butyl maleate units and methacrylic acid units was determined by adding 100 mL of pyridine to 0.2 g of a 2 mm square carboxyl group-containing nitrile rubber, stirring for 16 hours, and then adding potassium hydroxide to 0.5 with stirring. Using 02N alcoholic potassium hydroxide solution, the number of moles of carboxyl groups per 100 g of carboxyl group-containing nitrile rubber was obtained by titration using thymolphthalein as an indicator at room temperature, and the obtained number of moles was added to mono-n-butyl maleate. It was calculated by converting to the amount of units or methacrylic acid units.
The content ratio of 1,3-butadiene units and saturated butadiene units was calculated by measuring the iodine value (according to JIS K 6235) before and after the hydrogenation reaction using the carboxyl group-containing nitrile rubber. .
The acrylonitrile unit content was calculated by measuring the nitrogen content in the carboxyl group-containing nitrile rubber by the semi-micro Kjeldahl method according to JIS K6384.
The content ratios of n-butyl acrylate units and methoxyethyl acrylate units are the mono-n-butyl maleate units, methacrylic acid units, 1,3-butadiene units, saturated butadiene units, and acrylonitrile units obtained above. It was obtained by calculation from the content ratio.

[Contents of sodium, calcium, and magnesium in carboxyl group-containing nitrile rubber]
The respective contents of sodium, calcium, and magnesium in the carboxyl group-containing nitrile rubber and the total content thereof are determined by adding sulfuric acid and nitric acid to the carboxyl group-containing nitrile rubber, heating, wet decomposition, and then was diluted appropriately and measured by the internal standard calibration curve method using ICP-AES (SPS-5000: manufactured by Seiko Instruments Inc.). In addition, when it was below the detection limit, it was regarded as the content with the detection limit value.

[Chloride ion content in carboxyl group-containing nitrile rubber]
A carboxyl group-containing nitrile rubber was rolled out to form a sheet, which was cut into a size of about 2×10 mm to obtain a measurement sample, and about 0.5 g of the measurement sample was placed in a 200 mm beaker. Then, 70 ml of methyl ethyl ketone was added to the beaker containing the measurement sample and stirred to completely dissolve the measurement sample, then 30 ml of isopropyl alcohol was added, and further methyl ethyl ketone was added to bring the total volume to 150 ml. Then, 1 ml of a 2% sulfuric acid solution was added to this solution with a Komagome pipette, an N/200 silver nitrate solution was added dropwise, and the chloride ion content was determined by potentiometric titration. As a titrator, COMITE-101 manufactured by Hiranuma Sangyo Co., Ltd. was used, and silver support electrode AG-68/silver reference electrode AM-44 was used.

[LLC resistance]
The crosslinkable rubber composition was placed in a mold of 15 cm long, 15 cm wide and 0.2 cm deep, and press-molded at 170° C. for 20 minutes while applying a press pressure of 10 MPa, followed by secondary crosslinking at 170° C. for 4 hours. A sheet-shaped rubber cross-linked product was obtained by carrying out. The resulting sheet-like crosslinked rubber product was immersed in LLC (Long Life Coolant) at a temperature of 125° C. for 168 hours. A 50% aqueous solution of "Dex-Cool" manufactured by AcDelco was used as LLC. Then, the degree of swelling after immersion in LLC was determined according to the following formula. It can be said that the lower the swelling ratio after immersion in LLC, the better the LLC resistance.
Degree of swelling after immersion in LLC (%) = (volume of crosslinked rubber after immersion in LLC - volume of crosslinked rubber before immersion in LLC) / volume of crosslinked rubber before immersion in LLC x 100

[Compression set (O-ring compression set)]
Using a mold with an inner diameter of 30 mm and a ring diameter of 3 mm, the cross-linkable rubber composition is cross-linked at 170 ° C. for 20 minutes at a press pressure of 10 MPa, and then subjected to secondary cross-linking at 170 ° C. for 4 hours to obtain an O-ring shape. of test pieces were obtained. Then, using the obtained O-ring-shaped test piece, the distance between the two planes sandwiching the O-ring-shaped test piece is compressed by 25% in the ring thickness direction, and held at 150 ° C. for 168 hours. The compression set was measured according to JIS K6262 under the conditions of The smaller this value, the better the compression set resistance.
In this example, the compression set was measured using an O-ring-shaped test piece, but according to the findings of the present inventors, even if the compression set in the disc shape is low, the O-ring In the case of an O-shaped test piece, the compression set may be high, so in this example, based on this knowledge, the compression set was measured with an O-ring-shaped test piece. It is something to do.

[Production Example 1]
(Production of carboxyl group-containing nitrile rubber (A-1))
In a metal bottle, 180 parts of ion-exchanged water, 25 parts of an aqueous sodium dodecylbenzenesulfonate solution with a concentration of 10% by weight, 5 parts of a sodium salt of a naphthalenesulfonic acid formalin condensate with a concentration of 10%, 20 parts of acrylonitrile, maleic monon- 5 parts of butyl, 35 parts of n-butyl acrylate, and 0.75 parts of t-dodecyl mercaptan (molecular weight modifier) were charged in this order, and after replacing the internal gas with nitrogen three times, 40 parts of 1,3-butadiene was charged. is. A metal bottle was kept at 10° C., 0.1 part of cumene hydroperoxide (polymerization initiator), a reducing agent, a chelating agent, and an appropriate amount of builder were charged, and the polymerization reaction was continued while stirring until the polymerization conversion rate was 80%. 4 parts of a 2.5% by weight aqueous solution of 2,2,6,6-tetramethylpiperidine-1-oxyl (polymerization terminator) was added to stop the polymerization reaction. Subsequently, residual monomers were removed at a water temperature of 60° C. to obtain a latex of copolymer rubber (solid concentration: 25% by weight).

Next, in an autoclave, the latex obtained above and a palladium catalyst (1% by weight of acetic acid A solution obtained by mixing a palladium acetone solution and an equal weight of ion-exchanged water) is added, hydrogenation is performed at a hydrogen pressure of 3 MPa, a temperature of 50 ° C., and a solid content concentration of 15% by weight for 6 hours. Per 100 parts of coalesced rubber, 0.1 part of 4,6-bis(octylthiomethyl)-o-cresol (Irganox 1520L, manufactured by BASF Japan, anti-aging agent) and 0.3 parts of preservative (product name "Acticide MBS", manufactured by Thor Japan, preservative) was added. An appropriate amount of an aqueous sulfuric acid solution was added thereto to obtain latex (X-1) of carboxyl group-containing nitrile rubber (solid concentration: 12.5% by weight, pH 4.0).

Then, with respect to the obtained carboxyl group-containing nitrile rubber latex (X-1), calcium chloride aqueous solution (1% by weight aqueous solution, pH = 2.5) is added to 100 parts of carboxyl group-containing nitrile rubber, converted to calcium chloride. The carboxyl group-containing nitrile rubber was coagulated to obtain a crumb slurry containing crumb-like carboxyl group-containing nitrile rubber. Next, 100 parts of the obtained crumb slurry was washed three times with 2000 parts of water, filtered, and vacuum-dried at 60° C. for 12 hours to obtain a carboxyl group-containing nitrile rubber (A-1). got

Composition, iodine value and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-1), respective contents of sodium, calcium and magnesium in the obtained carboxyl group-containing nitrile rubber (A-1) and total content, and chloride ion content are shown in Table 1.

[Production Example 2]
(Production of carboxyl group-containing nitrile rubber (A-2))
A carboxyl group-containing nitrile rubber latex (X-1) was obtained in the same manner as in Production Example 1, and when the carboxyl group-containing nitrile rubber latex (X-1) was coagulated, calcium chloride was used as a coagulating salt solution. An aqueous solution (1% by weight aqueous solution, pH = 2.5) and an aqueous sodium chloride solution (10% by weight aqueous solution, pH = 2.5) are added to 100 parts of carboxyl group-containing nitrile rubber, and 1 part in terms of calcium chloride and sodium chloride Coagulation, washing and drying were carried out in the same manner as in Production Example 1, except that the amount used was 40 parts in terms of conversion, and the number of washings using 2000 parts of water was 6 times. , to obtain a carboxyl group-containing nitrile rubber (A-2). Composition, iodine value and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-2), respective contents of sodium, calcium and magnesium in the obtained carboxyl group-containing nitrile rubber (A-2) and total content, and chloride ion content are shown in Table 1.

[Production Example 3]
(Production of carboxyl group-containing nitrile rubber (A-3))
A carboxyl group-containing nitrile rubber latex (X-1) was obtained in the same manner as in Production Example 1, and when the carboxyl group-containing nitrile rubber latex (X-1) was coagulated, calcium chloride was used as a coagulating salt solution. An aqueous solution (10% by weight aqueous solution, pH = 2.5) and an aqueous magnesium sulfate solution (20% by weight aqueous solution, pH = 2.5) were added to 100 parts of carboxyl group-containing nitrile rubber in terms of calcium chloride and magnesium sulfate. Coagulation, washing and drying were performed in the same manner as in Production Example 1, except that the amount used was 70 parts in terms of conversion, and the number of washings using 2000 parts of water was 2 times. , to obtain a carboxyl group-containing nitrile rubber (A-3). Composition, iodine value and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-3), respective contents of sodium, calcium and magnesium in the obtained carboxyl group-containing nitrile rubber (A-3) and total content, and chloride ion content are shown in Table 1.

[Production Example 4]
(Production of carboxyl group-containing nitrile rubber (A-4))
A carboxyl group-containing nitrile rubber latex (X-1) was obtained in the same manner as in Production Example 1, and sodium chloride was used as a coagulating salt solution when coagulating the carboxyl group-containing nitrile rubber latex (X-1). An aqueous solution (20 wt% aqueous solution, pH = 2.5) was used in an amount of 80 parts in terms of sodium chloride per 100 parts of carboxyl group-containing nitrile rubber, and washing with water using 2000 parts A carboxyl group-containing nitrile rubber (A-4) was obtained by performing coagulation, washing and drying in the same manner as in Production Example 1 except that the number of times was changed to 5. Composition, iodine value and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-4), respective contents of sodium, calcium and magnesium in the obtained carboxyl group-containing nitrile rubber (A-4) and total content, and chloride ion content are shown in Table 1.

[Production Example 5]
(Production of carboxyl group-containing nitrile rubber (A-5))
A carboxyl group-containing nitrile rubber latex (X-5) was obtained in the same manner as in Production Example 1, except that the amount of acrylonitrile used was changed to 15 parts and the amount of n-butyl acrylate used was changed to 40 parts. Then, the obtained carboxyl group-containing nitrile rubber latex (X-5) was coagulated, washed and dried under the same conditions as in Production Example 1 to obtain a carboxyl group-containing nitrile rubber (A-5). Obtained. Composition, iodine value and carboxyl group content of obtained carboxyl group-containing nitrile rubber (A-5), total content of sodium, calcium and magnesium in obtained carboxyl group-containing nitrile rubber (A-5) , as well as the chloride ion content are shown in Table 1.

[Production Example 6]
(Production of carboxyl group-containing nitrile rubber (A-6))
The amount of acrylonitrile used was changed to 25 parts, the amount of mono-n-butyl maleate used was changed to 7 parts, and 28 parts of methoxyethyl acrylate was used instead of n-butyl acrylate. A carboxyl group-containing nitrile rubber latex (X-6) was obtained in the same manner as in Example 1, and the obtained carboxyl group-containing nitrile rubber latex (X-6) was subjected to the same conditions as in Production Example 1. By performing coagulation, washing and drying, a carboxyl group-containing nitrile rubber (A-6) was obtained. Composition, iodine value and carboxyl group content of obtained carboxyl group-containing nitrile rubber (A-6), total content of sodium, calcium and magnesium in obtained carboxyl group-containing nitrile rubber (A-6) , as well as the chloride ion content are shown in Table 1.

[Production Example 7]
(Production of carboxyl group-containing nitrile rubber (A-7))
Carboxyl group A nitrile rubber-containing latex (X-7) is obtained, and the obtained carboxyl group-containing nitrile rubber latex (X-7) is coagulated, washed and dried under the same conditions as in Production Example 1. , to obtain a carboxyl group-containing nitrile rubber (A-7). Composition, iodine value and carboxyl group content of obtained carboxyl group-containing nitrile rubber (A-7), total content of sodium, calcium and magnesium in obtained carboxyl group-containing nitrile rubber (A-7) , as well as the chloride ion content are shown in Table 1.

[Production Example 8]
(Production of carboxyl group-containing nitrile rubber (A-8))
A carboxyl group-containing nitrile rubber latex (X-1) obtained in the same manner as in Production Example 1 and a carboxyl group-containing nitrile rubber latex (X-6) obtained in the same manner as in Production Example 6 were mixed with carboxyl Mixed latex (X-8) was obtained by mixing at a weight ratio of 20:80 in terms of group-containing nitrile rubber. Then, the obtained mixed latex (X-8) was coagulated, washed and dried under the same conditions as in Production Example 1 to obtain a carboxyl group-containing nitrile rubber (A-8). Composition, iodine value and carboxyl group content of obtained carboxyl group-containing nitrile rubber (A-8), total content of sodium, calcium and magnesium in obtained carboxyl group-containing nitrile rubber (A-8) , as well as the chloride ion content are shown in Table 1.

[Production Example 9]
(Production of carboxyl group-containing nitrile rubber (A-9))
A carboxyl group-containing nitrile rubber latex (X-1) obtained in the same manner as in Production Example 1 and a carboxyl group-containing nitrile rubber latex (X-6) obtained in the same manner as in Production Example 6 were mixed with carboxyl Mixed latex (X-9) was obtained by mixing at a weight ratio of 80:20 in terms of group-containing nitrile rubber. Then, the obtained mixed latex (X-9) was coagulated, washed and dried under the same conditions as in Production Example 1 to obtain a carboxyl group-containing nitrile rubber (A-9). Composition, iodine value and carboxyl group content of obtained carboxyl group-containing nitrile rubber (A-9), total content of sodium, calcium and magnesium in obtained carboxyl group-containing nitrile rubber (A-9) , as well as the chloride ion content are shown in Table 1.

[Production Example 10]
(Production of carboxyl group-containing nitrile rubber (A-10))
A carboxyl group-containing nitrile rubber latex (X-1) was obtained in the same manner as in Production Example 1, and when the carboxyl group-containing nitrile rubber latex (X-1) was coagulated, calcium chloride was used as a coagulating salt solution. An aqueous solution (10% by weight aqueous solution, pH = 2.5) and an aqueous sodium chloride solution (20% by weight aqueous solution, pH = 2.5) were added to 100 parts of carboxyl group-containing nitrile rubber in terms of 5 parts of calcium chloride and sodium chloride. A carboxyl group-containing nitrile rubber (A-10) was obtained in the same manner as in Production Example 1 by performing coagulation, washing and drying, except that the amount used was 100 parts in terms of conversion. Composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-10), respective contents of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A-10) and total content, and chloride ion content are shown in Table 2.

[Production Example 11]
(Production of carboxyl group-containing nitrile rubber (A-11))
A carboxyl group-containing nitrile rubber latex (X-1) was obtained in the same manner as in Production Example 1, and when the carboxyl group-containing nitrile rubber latex (X-1) was coagulated, instead of the coagulating salt solution, Solidification, washing and drying were carried out in the same manner as in Production Example 1, except that methanol was used in an amount of 1600 parts per 100 parts of the carboxyl group-containing nitrile rubber ( A-11) was obtained. Composition, iodine value and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-11), respective contents of sodium, calcium and magnesium in the obtained carboxyl group-containing nitrile rubber (A-11) and total content, and chloride ion content are shown in Table 2.

[Production Example 12]
(Production of carboxyl group-containing nitrile rubber (A-12))
In the same manner as in Production Example 1, a carboxyl group-containing nitrile rubber latex (X-1) was obtained. An aqueous solution (30% by weight aqueous solution, pH = 2.5) and an aqueous sodium chloride solution (20% by weight aqueous solution, pH = 2.5) were added to 100 parts of carboxyl group-containing nitrile rubber in terms of magnesium sulfate and sodium chloride. Coagulation, washing and drying were carried out in the same manner as in Production Example 1, except that the amount used was 100 parts in terms of conversion, and the number of washings using 2000 parts of water was 2 times. , to obtain a carboxyl group-containing nitrile rubber (A-12). Composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-12), respective contents of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A-12) and total content, and chloride ion content are shown in Table 2.

[Production Example 13]
(Production of carboxyl group-containing nitrile rubber (A-13))
A carboxyl group-containing nitrile rubber latex (X-1) was obtained in the same manner as in Production Example 1, and sodium chloride was used as a coagulating salt solution when coagulating the carboxyl group-containing nitrile rubber latex (X-1). An aqueous solution (20 wt% aqueous solution, pH = 2.5) was used in an amount of 80 parts in terms of sodium chloride per 100 parts of carboxyl group-containing nitrile rubber, and washing with water using 2000 parts A carboxyl group-containing nitrile rubber (A-13) was obtained by performing coagulation, washing and drying in the same manner as in Production Example 1 except that the number of times was changed to 7. Composition, iodine value and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-13), respective contents of sodium, calcium and magnesium in the obtained carboxyl group-containing nitrile rubber (A-13) and total content, and chloride ion content are shown in Table 2.

[Production Example 14]
(Production of carboxyl group-containing nitrile rubber (A-14))
A carboxyl group-containing nitrile rubber latex (X-14) was obtained in the same manner as in Production Example 1, except that 5 parts of methacrylic acid was used instead of mono-n-butyl maleate. The nitrile rubber latex (X-14) was coagulated, washed and dried under the same conditions as in Production Example 1 to obtain a carboxyl group-containing nitrile rubber (A-14). Composition, iodine value and carboxyl group content of obtained carboxyl group-containing nitrile rubber (A-14), total content of sodium, calcium and magnesium in obtained carboxyl group-containing nitrile rubber (A-14) , as well as the chloride ion content are shown in Table 2.

[Production Example 15]
(Production of nitrile rubber (A-15))
A nitrile rubber latex (X-15) was obtained in the same manner as in Production Example 1, except that the amount of n-butyl acrylate used was changed to 40 parts and mono-n-butyl maleate was not used. The obtained nitrile rubber latex (X-15) was coagulated, washed and dried under the same conditions as in Production Example 1 to obtain nitrile rubber (A-15). Composition, iodine value and carboxyl group content of the obtained nitrile rubber (A-15), total content of sodium, calcium and magnesium in the obtained nitrile rubber (A-15), and chloride ion content The amounts are shown in Table 2.

[Production Example 16]
(Production of carboxyl group-containing nitrile rubber (A-16))
A carboxyl group-containing nitrile rubber latex (X-16) was obtained in the same manner as in Production Example 1, except that the hydrogenation reaction conditions were changed so that the palladium content was 500 ppm by weight. The group-containing nitrile rubber latex (X-16) was coagulated, washed and dried under the same conditions as in Production Example 1 to obtain a carboxyl group-containing nitrile rubber (A-16). Composition, iodine value and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-16), total content of sodium, calcium and magnesium in the obtained carboxyl group-containing nitrile rubber (A-16) , as well as the chloride ion content are shown in Table 2.

[Example 1]
Using a Banbury mixer, 100 parts of the carboxyl group-containing nitrile rubber (A-1) obtained in Production Example 1, 55 parts of silica (trade name "Ultrasil VN2", manufactured by EVONIK), amino group-modified silicone oil ( Trade name "KF-868", manufactured by Shin-Etsu Silicone Co., Ltd., compound represented by the above general formula (7)) 4 parts, tri-2-ethylhexyl trimellitate (trade name "ADEKA CIZER C-8", manufactured by ADEKA) , plasticizer) 5 parts, 4,4′-di-(α,α-dimethylbenzyl)diphenylamine (trade name “Nocrac CD”, manufactured by Ouchi Shinko Kagaku Co., Ltd., anti-aging agent) 1.5 parts, stearic acid 1 and 1 part of polyoxyethylene alkyl ether phosphate (trade name “Phosphanol RL210” manufactured by Toho Chemical Industry Co., Ltd., processing aid) were added and mixed at 50° C. for 5 minutes. Next, the resulting mixture was transferred to a roll at 50° C., and 1.9 parts of hexamethylenediamine carbamate (manufactured by DuPont Dow Elastomers, trade name “Diak #1”, polyamine cross-linking agent belonging to aliphatic polyamines) , and 1,8-diazabicyclo[5,4,0]-undecene-7 (DBU) (trade name “RHENOGRAN XLA-60 (GE2014)”, manufactured by Rhein Chemie, DBU 60% (zinc dialkyl diphosphate salt and 4 parts of basic cross-linking accelerator) were blended and kneaded to obtain a cross-linkable rubber composition.

Then, using the obtained crosslinkable rubber composition, water resistance and compression set were measured by the methods described above. Table 1 shows the results.

[Examples 2 to 4]
The carboxyl group-containing nitrile rubber (A-1) obtained in Production Example 1 was replaced with the carboxyl group-containing nitrile rubbers (A-2) to (A-4) obtained in Production Examples 2 to 4, respectively. Except for this, a crosslinkable rubber composition was obtained in the same manner as in Example 1 and evaluated in the same manner. Table 1 shows the results.

[Example 5]
The procedure of Example 1 was repeated except that 90 parts of vinyl group-containing silane coupling agent-treated aluminum silicate (trade name "Burgess KE", manufactured by Burgess Pigment Co., Ltd., surface-treated silicate) was used instead of 55 parts of silica. Thus, a crosslinkable rubber composition was obtained and evaluated in the same manner. Table 1 shows the results.

[Example 6]
Example 1 except that 4 parts of amino group-modified silicone oil (trade name "Structol HT740", manufactured by S&S Japan) were used instead of 4 parts of amino group-modified silicone oil (trade name "KF-868"). In the same manner as above, a crosslinkable rubber composition was obtained and evaluated in the same manner. Table 1 shows the results.

[Example 7]
A crosslinkable rubber composition was obtained in the same manner as in Example 1, except that the amount of the amino group-modified silicone oil (trade name “KF-868”) was changed to 1 part, and evaluated in the same manner. Table 1 shows the results.

[Examples 8 to 12]
The carboxyl group-containing nitrile rubber (A-1) obtained in Production Example 1 was replaced with the carboxyl group-containing nitrile rubbers (A-5) to (A-9) obtained in Production Examples 5 to 9, respectively. , Except that the amount of hexamethylenediamine carbamate used was changed to 1.9 parts, 2.7 parts, 1.9 parts, 2.5 parts, and 2.1 parts, respectively, in the same manner as in Example 1, crosslinkable A rubber composition was obtained and similarly evaluated. Table 1 shows the results.

[Example 13]
Using rolls, 20 parts of the carboxyl group-containing nitrile rubber (A-1) obtained in Production Example 1 and 80 parts of the carboxyl group-containing nitrile rubber (A-6) obtained in Production Example 6 are masticated. Thus, a blended rubber was obtained. The content and total content of sodium, calcium and magnesium and the chloride ion content of the obtained blend rubber were measured according to the above method. Table 1 shows the measurement results. Then, a crosslinkable rubber composition was obtained in the same manner as in Example 1, except that 100 parts of the obtained blend rubber was used and the amount of hexamethylenediamine carbamate used was 2.5 parts. Evaluation was performed in the same manner. Table 1 shows the results.

[Comparative Examples 1 to 3]
The carboxyl group-containing nitrile rubber (A-1) obtained in Production Example 1 was replaced with the carboxyl group-containing nitrile rubbers (A-10) to (A-12) obtained in Production Examples 10 to 12, respectively. Except for this, a crosslinkable rubber composition was obtained in the same manner as in Example 1 and evaluated in the same manner. Table 2 shows the results.

[Comparative Example 4]
A crosslinkable rubber composition was obtained in the same manner as in Example 1, except that 50 parts of FEF carbon (trade name "SEAST SO", manufactured by Tokai Carbon Co., Ltd.) was used instead of 55 parts of silica, and evaluated in the same manner. did Table 2 shows the results.

[Comparative Example 5]
The procedure of Comparative Example 4 was repeated except that the carboxyl group-containing nitrile rubber (A-1) obtained in Production Example 1 was replaced with the carboxyl group-containing nitrile rubber (A-13) obtained in Production Example 13. Thus, a crosslinkable rubber composition was obtained and evaluated in the same manner. Table 2 shows the results.

[Comparative Example 6]
The procedure of Example 1 was repeated except that the carboxyl group-containing nitrile rubber (A-1) obtained in Production Example 1 was replaced with the carboxyl group-containing nitrile rubber (A-14) obtained in Production Example 14. Thus, a crosslinkable rubber composition was obtained and evaluated in the same manner. Table 2 shows the results.

[Comparative Example 7]
The carboxyl group-containing nitrile rubber (A-1) obtained in Production Example 1 was replaced with the carboxyl group-containing nitrile rubber (A-15) obtained in Production Example 15, and hexamethylenediamine carbamate, And instead of 1,8-diazabicyclo[5,4,0]-undecene-7 (DBU), 1,3-bis(t-butylperoxyisopropyl)benzene 40% product (trade name “Vul Cup 40KE”, Arkema A crosslinkable rubber composition was obtained in the same manner as in Example 1, except that 8 parts of Organic Peroxide Crosslinking Agent (manufactured by Co., Ltd.) was used, and the evaluation was performed in the same manner. Table 2 shows the results.

[Comparative Example 8]
The procedure of Example 1 was repeated except that the carboxyl group-containing nitrile rubber (A-1) obtained in Production Example 1 was replaced with the carboxyl group-containing nitrile rubber (A-16) obtained in Production Example 16. Thus, a crosslinkable rubber composition was obtained and evaluated in the same manner. Table 2 shows the results.

As shown in Tables 1 and 2, the α,β-ethylenically unsaturated dicarboxylic acid monoester monomer unit is contained in a proportion of 0.1 to 20% by weight, the iodine value is 120 or less, sodium, A nitrile rubber composition containing a carboxyl group-containing nitrile rubber having a total calcium and magnesium content of 130 to 1000 ppm by weight and a sodium content of 600 ppm by weight or less, and a filler containing silicon For example, the rubber cross-linked products obtained using this were excellent in LLC resistance and compression set resistance (Examples 1 to 13).

On the other hand, when the sodium content exceeded 600 ppm by weight, the obtained cross-linked rubber was inferior in LLC resistance (Comparative Example 1).
Also, when the total content of sodium, calcium and magnesium is less than 130 ppm by weight, or conversely, when the total content of sodium, calcium and magnesium is more than 1000 ppm by weight, the resulting crosslinked rubber The products were inferior in compression set resistance (Comparative Examples 2 and 3).
Furthermore, when carbon is blended instead of a filler containing silicon, a relatively low sodium content results in inferior compression set resistance, and a relatively high sodium content results in The result was inferior LLC resistance (Comparative Examples 4 and 5).
Also, when a nitrile rubber containing no α,β-ethylenically unsaturated dicarboxylic acid monoester monomer unit is used, or when a nitrile rubber having an iodine value exceeding 120 is used, the resulting crosslinked rubber is , resulting in inferior compression set resistance (Comparative Examples 6 to 8).

Claims (6)

Containing α,β-ethylenically unsaturated dicarboxylic acid monoester monomer units in a proportion of 0.1 to 20% by weight, having an iodine value of 60 or less, and a total content of sodium, calcium and magnesium of 130 a carboxyl group-containing nitrile rubber having a sodium content of up to 1000 ppm by weight and 600 ppm by weight or less;
A nitrile rubber composition containing a silicon-containing filler. The nitrile rubber composition according to claim 1, further containing modified silicone oil. 3. The nitrile rubber composition according to claim 2, wherein said modified silicone oil has an amino group as a modifying group. The nitrile rubber composition according to any one of claims 1 to 3, wherein the carboxyl group-containing nitrile rubber contains 11 to 50% by weight of α,β-ethylenically unsaturated monocarboxylic acid ester monomer units. . A crosslinkable rubber composition obtained by blending the nitrile rubber composition according to any one of claims 1 to 4 with a polyvalent amine compound. A rubber cross-linked product obtained by cross-linking the cross-linkable rubber composition according to claim 5 .