JPWO2019049855A1 - Carboxylic group-containing nitrile rubber, crosslinkable nitrile rubber composition and crosslinked rubber - Google Patents

Abstract

It contains α, β-ethylenically unsaturated monocarboxylic acid ester monomer units in a proportion of 26 to 50% by weight, has an iodine value of 120 or less, and has a total content of sodium, calcium, and magnesium of 1000 parts by weight ppm. Hereinafter, a carboxyl group-containing nitrile rubber having a chloride ion content of 50 to 500 ppm by weight is provided.

Description

The present invention relates to a carboxyl group-containing nitrile rubber, a crosslinkable nitrile rubber composition, and a crosslinked rubber product. More specifically, the present invention provides a rubber crosslinked product having excellent cold resistance, long life coolant resistance, and compression set resistance. The present invention relates to a nitrile rubber containing a carboxyl group and a crosslinkable nitrile rubber composition.

Traditionally, nitrile rubber (acrylonitrile-butadiene copolymer rubber) has been used as a material for rubber parts for automobiles such as hoses, tubes, and seals, taking advantage of its oil resistance, mechanical properties, and chemical resistance. Nitrile hydride rubber (hydrogenated acrylonitrile-butadiene copolymer rubber), which is a hydrogenated carbon-carbon double bond in the polymer main chain of nitrile rubber, has even better heat resistance, so seals, belts, hoses, diaphragms, etc. Used for rubber parts. On the other hand, in applications such as seals and belts, it is required that the compression set is even smaller.

For example, as an attempt to reduce such compressive permanent strain, Patent Document 1 proposes a technique for a carboxyl group-containing nitrile rubber in which a carboxyl group is introduced into the nitrile rubber.

International Publication No. 2007/049651

According to the technique of Patent Document 1, although a rubber crosslinked product in which the compression set is reduced to a certain extent can be obtained, it cannot be said that the cold resistance and the water resistance are sufficient. Therefore, it may not be suitable for applications requiring water resistance in an environment with a relatively low temperature, for example, as a sealing material for sealing an aqueous refrigerant in a cold region.

In particular, 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, and the sealing material for sealing such LLC has more LLC resistance. It is required to be excellent in quality, and even if it has sufficient water resistance to water, it may not necessarily show sufficient resistance to LLC, whereas it is used to seal LLC. The sealing material is required to exhibit sufficient resistance to such LLC. In addition, it is also required to have better cold resistance from the viewpoint of being able to seal well even in winter in cold regions.

The present invention has been made in view of such circumstances, and a carboxyl group-containing nitrile rubber capable of providing a rubber crosslinked product having excellent cold resistance, long life coolant resistance (LLC resistance) and compression permanent strain resistance, and An object of the present invention is to provide a crosslinkable nitrile rubber composition using such a carboxyl group-containing nitrile rubber.

As a result of diligent studies to achieve the above object, the present inventors have contained α, β-ethylenically unsaturated monocarboxylic acid ester monomer unit in a specific ratio, and sodium, calcium, and magnesium. It was found that the above object can be achieved by the carboxyl group-containing nitrile rubber in which the total content and the chloride ion content are controlled in a specific range, and the present invention has been completed.

That is, according to the present invention, α, β-ethylenically unsaturated monocarboxylic acid ester monomer unit is contained in a proportion of 26 to 50% by weight, the iodine value is 120 or less, and sodium, calcium, and magnesium are used. Provided are carboxyl group-containing nitrile rubbers having a total content of 1000 ppm by weight or less and a chloride ion content of 50 to 500 ppm by weight.
The carboxyl group-containing nitrile rubber of the present invention preferably contains a carboxyl group-containing monomer unit in a proportion of 1 to 10% by weight.
The carboxyl group-containing nitrile rubber of the present invention preferably contains α, β-ethylenically unsaturated nitrile monomer units in a proportion of 7 to 42% by weight.
The carboxyl group-containing nitrile rubber of the present invention preferably contains a conjugated diene monomer unit in a proportion of 10 to 66% by weight.
The carboxyl group-containing nitrile rubber of the present invention preferably contains an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit.

According to the present invention, a crosslinkable nitrile rubber composition containing the above-mentioned carboxyl group-containing nitrile rubber and a polyvalent amine compound is provided.
Further, according to the present invention, there is provided a rubber crosslinked product obtained by crosslinking the above crosslinkable nitrile rubber composition.
Further, according to the present invention, a seal made of the above-mentioned rubber crosslinked product is provided.

According to the present invention, the above method for producing a carboxyl group-containing nitrile rubber includes a step of adding a coagulant to the latex of the carboxyl group-containing nitrile rubber to coagulate the latex, and the coagulant is a chloride. Alternatively, a method for producing a carboxyl group-containing nitrile rubber using chloride and a coagulant other than chloride is provided.
In the production method of the present invention, the amount of the coagulant used is preferably 0.5 to 35 parts by weight with respect to 100 parts by weight of the carboxyl group-containing nitrile rubber contained in the latex.

According to the present invention, a carboxyl group-containing nitrile rubber capable of providing a rubber crosslinked product having excellent cold resistance, LLC resistance and compression permanent strain resistance, and a crosslinkable property containing such a carboxyl group-containing nitrile rubber. It is possible to provide a rubber crosslinked product obtained by using a nitrile rubber composition and having excellent cold resistance, LLC resistance and compression set resistance.

<Carboxylic group-containing nitrile rubber>
The carboxyl group-containing nitrile rubber of the present invention contains an α, β-ethylenically unsaturated monocarboxylic acid ester monomer unit in a proportion of 26 to 50% by weight, and contains a carboxyl group having an iodine value of 120 or less. Nitrile rubber. Further, the carboxyl group-containing nitrile rubber of the present invention has a total content of sodium, calcium and magnesium controlled in the range of 1000 ppm by weight or less and a chloride ion content controlled in the range of 50 to 500 ppm by weight.

The carboxyl group-containing nitrile rubber of the present invention is not particularly limited, but for example, α, β-ethylenically unsaturated nitrile monomer, carboxyl group-containing monomer, and α, β-ethylenically unsaturated monocarboxylic acid. Examples thereof include those obtained by copolymerizing an ester monomer and other copolymerizable monomers added as needed.

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, and for example, acrylonitrile; α-chloroacrylonitrile, α-bromoacrylonitrile, etc. Α-halogenoacrylonitrile; α-alkylacrylonitrile such as methacrylonitrile; and the like. Among these, acrylonitrile and methacrylonitrile are preferable, and acrylonitrile is more preferable. The α, β-ethylenically unsaturated nitrile monomer may be used alone or in combination of two or more.

The content of the α, β-ethylenically unsaturated nitrile monomer unit in the carboxyl group-containing nitrile rubber of the present invention is preferably 7 to 42% by weight, more preferably 10 with respect to all the monomer units. It is ~ 33% by weight, more preferably 13-25% by weight. By setting the content of the α, β-ethylenically unsaturated nitrile monomer unit in the above range, the obtained rubber crosslinked product can be made excellent in oil resistance and cold resistance.

The carboxyl group-containing monomer has at least one unsubstituted (free) carboxyl group that is copolymerizable with an α, β-ethylenically unsaturated nitrile monomer and has not been esterified. If it is a monomer, it is not particularly limited. By using a carboxyl group-containing monomer, a carboxyl group can be introduced into the nitrile rubber. As a result, the obtained rubber crosslinked product can be made to have excellent compression-resistant permanent strain resistance while having good mechanical properties such as elongation.

Examples of the carboxyl group-containing monomer include α, β-ethylenically unsaturated monocarboxylic acid monomer, α, β-ethylenically unsaturated polyvalent carboxylic acid monomer, and α, β-ethylenically unsaturated. Examples thereof include saturated dicarboxylic acid monoester monomers. In addition, the carboxyl group-containing monomer also includes a monomer in which the carboxyl group of these monomers forms a carboxylate. Further, an anhydride of an α, β-ethylenically unsaturated polycarboxylic acid can also be used as a carboxyl group-containing monomer because the acid anhydride group is cleaved to form a carboxyl group after copolymerization.

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

Examples of the α, β-ethylenic unsaturated polyvalent carboxylic acid monomer include butendioic acid such as fumaric acid and maleic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, allylmalonic acid, and terraconic acid. Examples of the anhydride of α, β-unsaturated polyvalent carboxylic acid include maleic anhydride, itaconic anhydride, and citraconic anhydride.

Examples of the α, β-ethylenic unsaturated dicarboxylic acid monoester monomer include maleic acid monoalkyl esters such as monomethyl maleate, monoethyl maleate, monopropyl maleate, and mono n-butyl maleate; monocyclopentyl maleate, Monocycloalkyl maleate such as monocyclohexyl maleate and monocycloheptyl maleate; monoalkylcycloalkyl maleate such as monomethylcyclopentyl maleate and monoethylcyclohexyl maleate; monomethyl fumarate, monoethyl fumarate, mono fumarate Monoalkyl fumarate such as propyl and mono-butyl fumarate; monocyclopentyl fumarate, monocyclohexyl fumarate, monocycloalkyl ester fumarate such as monocycloheptyl fumarate; monomethylcyclopentyl fumarate, monoethylcyclohexyl fumarate Monoalkylcycloalkyl humalate such as monomethyl citrate, monoethyl citraconate, monopropyl citraconate, monoalkyl citraconic acid such as monon-butyl citraconate; monocyclopentyl citraconic acid, monocyclohexyl citraconic acid, mono citraconic acid Monocycloalkyl ester of citraconic acid such as cycloheptyl; Monomethylcyclopentyl citraconic acid, Monoalkylcycloalkyl ester of citraconic acid such as monoethylcyclohexyl citraconic acid; Monomethyl itaconate, monoethyl itaconate, monopropyl itaconate, mono n-butyl itaconate Monoalkyl ester of itaconic acid such as monocyclopentyl itaconic acid, monocyclohexyl itaconic acid, monocycloalkyl ester of itaconic acid such as monocycloheptyl itaconic acid; monomethylcyclopentyl itaconic acid, monoalkylcycloalkyl itaconic acid such as monoethylcyclohexyl itacone Esther; etc.

The carboxyl group-containing monomer may be used alone or in combination of two or more. Among these, the α, β-ethylenically unsaturated dicarboxylic acid monoester monomer is preferable, and the maleic acid monoalkyl ester and the fumaric acid monoalkyl ester are preferable from the viewpoint that the compression set resistance can be further improved. More preferably, maleic acid monoalkyl ester is further preferable, and maleic acid monon-butyl is particularly preferable. The alkyl group of the alkyl ester preferably has 2 to 8 carbon atoms.

The content of the carboxyl group-containing monomer unit in the carboxyl group-containing nitrile rubber of the present invention is preferably 1 to 10% by weight, more preferably 1.5 to 8% by weight, based on all the monomer units. , More preferably 2 to 6% by weight. By setting the content of the carboxyl group-containing monomer unit in the above range, it is possible to appropriately suppress the decrease in processability when the cross-linking agent is blended, and to appropriately obtain the compression-resistant permanent strain resistance of the obtained rubber cross-linked product. Can be enhanced.

The α, β-ethylenically unsaturated monocarboxylic acid ester monomer is not particularly limited, and for example, α, β-ethylenically unsaturated monocarboxylic acid alkyl ester monomer, α, β-ethylenically unsaturated Monocarboxylic acid alkoxyalkyl ester monomer, α, β-ethylenic unsaturated monocarboxylic acid aminoalkyl ester monomer, α, β-ethylenically unsaturated monocarboxylic acid hydroxyalkyl ester monomer, α, β- Examples thereof include ethylenically unsaturated monocarboxylic acid fluoroalkyl ester monomers.
Among these, α, β-ethylenically unsaturated monocarboxylic acid alkyl ester monomer or α, β-ethylenically unsaturated monocarboxylic acid alkoxyalkyl ester monomer is preferable.

As the alkyl ester monomer of the α, β-ethylenically unsaturated monocarboxylic acid, an alkyl group preferably having an alkyl group having 3 to 10 carbon atoms and having 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, and those having an alkyl group having 4 to 6 carbon atoms are further preferable.

Specific examples of the α, β-ethylenically unsaturated monocarboxylic acid alkyl ester monomer include acrylic acid alkyl esters such as propyl acrylate, n-butyl acrylate, n-pentyl acrylate, and 2-ethylhexyl acrylate. Quantities; Cycloalkyl acrylate monomers such as cyclopentyl acrylate and cyclohexyl acrylate; Alkylcycloalkyl acrylate monomers such as methyl cyclopentyl acrylate, ethyl cyclopentyl acrylate, and methyl cyclohexyl acrylate; propyl methacrylate , N-butyl methacrylate, n-pentyl methacrylate, n-octyl methacrylate and the like; cyclopentyl methacrylate, cyclohexyl methacrylate and the like; cycloalkyl methacrylate ester monomer; methylcyclopentyl methacrylate , Acrylic acid alkylcycloalkyl methacrylate monomers such as ethylcyclopentyl methacrylate and methylcyclohexyl methacrylate; alkyl chromonic acid esters such as propyl crotonate, n-butyl crotonate and 2-ethylhexyl crotonate; cyclopentyl crotonate. , Crotonic acid cycloalkyl ester monomers such as cyclohexyl crotonate and cyclooctyl 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 and having an alkoxyalkyl group, and has 2 to 6 carbon atoms. Those having a certain alkoxyalkyl group are more preferable, and those having an alkoxyalkyl group having 2 to 4 carbon atoms are further preferable.

Specific examples of the α, β-ethylenic unsaturated monocarboxylic acid alkoxyalkyl ester monomer include methoxymethyl acrylate, methoxyethyl acrylate, ethoxymethyl acrylate, ethoxyethyl acrylate, n-propoxyethyl acrylate, and Acrylic acid 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 Examples thereof include methacrylate alkoxyalkyl ester monomers such as butoxyethyl, methoxypropyl methacrylate, and methoxybutyl methacrylate;

Among these α, β-ethylenic unsaturated monocarboxylic acid ester monomers, the acrylic acid alkyl ester monomer and acrylic acid alkoxy can make the effect of the present invention even more remarkable. Alkyl ester monomers are preferable, n-butyl acrylate and methoxyethyl acrylate are more preferable, and n-butyl acrylate is particularly preferable.

The content of the α, β-ethylenically unsaturated monocarboxylic acid ester monomer unit in the carboxyl group-containing nitrile rubber of the present invention is preferably 26 to 50% by weight, based on the total monomer unit. Is 27 to 44% by weight, more preferably 28 to 37% by weight. If the content of the α, β-ethylenically unsaturated monocarboxylic acid ester monomer unit is too small, the obtained rubber crosslinked product will be inferior in cold resistance, while if it is too large, the obtained rubber crosslinked product will be inferior. The thing becomes inferior in water resistance.

Further, in the carboxyl group-containing nitrile rubber of the present invention, α, β-ethylenically unsaturated nitrile monomer, carboxyl group-containing monomer, and α are used so that the obtained rubber crosslinked product has rubber elasticity. , It is preferable that the conjugated diene monomer is copolymerized in addition to the β-ethylenically unsaturated monocarboxylic acid ester monomer.

As the conjugated diene monomer, a conjugated diene monomer having 4 to 6 carbon atoms such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and chloroprene is preferable. , 1,3-butadiene and isoprene are more preferred, and 1,3-butadiene is particularly preferred. The conjugated diene monomer may be used alone or in combination of two or more.

The content of the conjugated diene monomer unit (including the hydrogenated portion) in the carboxyl group-containing nitrile rubber of the present invention is preferably 10 to 66% by weight, based on the total monomer unit. It is preferably 22 to 61.5% by weight, more preferably 25 to 57% by weight. By setting the content of the conjugated diene monomer unit in the above range, the obtained rubber crosslinked product has good heat resistance and chemical stability, and the rubber elasticity is more appropriately enhanced. can do.

Further, the carboxyl group-containing nitrile rubber of the present invention may be obtained by copolymerizing each of the above-mentioned monomers with other monomers copolymerizable with the above-mentioned monomers. Examples of such other monomers include ethylene, α-olefin monomer, aromatic vinyl monomer, fluorine-containing vinyl monomer, and copolymerizable antiaging agent.

The α-olefin monomer preferably has 3 to 12 carbon atoms, and examples thereof include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene.
Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, vinylpyridine and the like.
Examples of the fluorine-containing vinyl monomer include fluoroethyl vinyl ether, fluoropropyl vinyl ether, o-trifluoromethylstyrene, vinyl pentafluorobenzoate, difluoroethylene, tetrafluoroethylene and the like.
Examples of the copolymerizable antiaging agent include N- (4-anilinophenyl) acrylamide, N- (4-anilinophenyl) methacrylicamide, N- (4-anilinenophenyl) cinnamamide, and N- (4-anilinophenyl). Examples thereof include anilinephenyl) crotonamide, N-phenyl-4- (3-vinylbenzyloxy) aniline, and N-phenyl-4- (4-vinylbenzyloxy) aniline.

A plurality of types of these other copolymerizable monomers may be used in combination. The content of the other monomer units is preferably 50% by weight or less, more preferably 30% by weight or less, still more preferably 10% by weight or less, based on all the monomer units.

The iodine value of the carboxyl group-containing nitrile rubber of the present invention is preferably 120 or less, more preferably 60 or less, still more preferably 40 or less, and particularly preferably 30 or less. By setting the iodine value to 120 or less, the heat resistance and ozone resistance of the obtained rubber crosslinked product can be improved.

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

The content of carboxyl groups in the carboxyl group-containing nitrile rubber of the present invention, that is, the number of moles of carboxyl groups per 100 g of carboxyl group-containing nitrile rubber is preferably 5 × 10 ^{-4 to} 5 × 10 ^-1 ephr, more preferably. It 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 in the above range, it is possible to appropriately enhance the compression-resistant permanent strain resistance of the obtained rubber crosslinked product while appropriately suppressing the decrease in processability when the cross-linking agent is blended.

The carboxyl group-containing nitrile rubber of the present invention has a total content of sodium, calcium, and magnesium in the carboxyl group-containing nitrile rubber of 1000 ppm by weight or less and a chloride ion content of 50 to 500 ppm by weight. It is controlled within the range of.

The total content of sodium, calcium, and magnesium in the carboxyl group-containing nitrile rubber of the present invention is 1000 ppm by weight or less, preferably 750 ppm by weight or less, and more preferably 500 ppm by weight or less. If the total content of sodium, calcium, and magnesium is too high, the resulting rubber crosslinked product will have poor compression set resistance. The total content of sodium, calcium, and magnesium in the carboxyl group-containing nitrile rubber is, for example, added sulfuric acid and nitric acid to the carboxyl group-containing nitrile rubber, heated, wet-decomposed, and then appropriately diluted. Therefore, it can be measured by high frequency inductively coupled plasma emission spectrometry (ICP / AES) using the internal standard calibration curve method. Specifically, the weights of sodium, calcium, and magnesium contained in the carboxyl group-containing nitrile rubber can be measured, and can be determined from the total weight of these and the weight of the carboxyl group-containing nitrile rubber. The lower limit of the total content of sodium, calcium, and magnesium is not particularly limited, but is usually 6 ppm by weight or more.

The total weight of sodium, calcium, and magnesium contained in the carboxyl group-containing nitrile rubber is, for example, when the carboxyl group-containing nitrile rubber is obtained by emulsification polymerization, when the latex of the obtained carboxyl group-containing nitrile rubber is solidified. It can be adjusted by selecting the type of coagulated salt used in the above and adjusting the amount of coagulated salt. Alternatively, it can be adjusted by a method of adjusting the washing conditions after solidification or a method of adjusting the amounts of sodium, calcium, and magnesium that are inevitably mixed in the manufacturing process.

The chloride ion content in the carboxyl group-containing nitrile rubber of the present invention is 50 to 500 wt ppm, preferably 100 to 300 ppm by weight, and more preferably 150 to 250 wt ppm. That is, the present invention may be a composition containing a carboxyl group-containing nitrile rubber and a chloride. If the chloride ion content is too low, the resulting rubber crosslinked product will be inferior in compression set resistance. On the other hand, if the chloride ion content is too high, the obtained rubber crosslinked product will be inferior in LLC resistance. The chloride ion content in the carboxyl group-containing nitrile rubber is such that the carboxyl group-containing nitrile rubber is completely dissolved by immersing the carboxyl group-containing nitrile rubber in a soluble solvent such as methyl ethyl ketone. , It can be measured by performing potential differential titration.

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

Since the total content of sodium, calcium, and magnesium and the chloride ion content are in the above range, the carboxyl group-containing nitrile rubber of the present invention is a composition containing these in the above content. You can also say that.

The method for producing the carboxyl group-containing nitrile rubber of the present invention is not particularly limited, but the above-mentioned monomer is copolymerized by an emulsion polymerization method, and if necessary, a carbon-carbon double bond in the obtained copolymer is obtained. Can be produced by hydrogenating. In emulsion polymerization, in addition to an emulsifier, a polymerization initiator, and a molecular weight modifier, commonly used polymerization auxiliary materials can be used.

The emulsifier is not particularly limited, and is, for example, a nonionic emulsifier such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester; myristic acid, palmitic acid, oleic acid. And salts of fatty acids such as linolenic acid, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, polycondensates of naphthalene sulfonate and formalin, higher alcohol sulfates, anionic emulsifiers such as alkylsulfosuccinate; α , Sulphonic acid ester of β-unsaturated carboxylic acid, sulfate ester of α, β-unsaturated carboxylic acid, copolymerizable emulsifier such as sulfoalkylaryl ether; and the like. The amount of the emulsifier added is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the monomer used for the polymerization.

The polymerization initiator is not particularly limited as long as it is a radical initiator, but is an inorganic peroxide such as potassium persulfate, sodium persulfate, ammonium persulfate, potassium perphosphate, hydrogen peroxide, etc .; cumenehydroperoxide, p- Mentan hydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, dibenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide , T-Organic peroxides such as t-butylperoxyisobutyrate; azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate; etc. be able to. These polymerization initiators can be used alone or in combination of two or more. Inorganic or organic peroxides are preferred as the polymerization initiator. When a peroxide is used as the polymerization initiator, it can also be used as a redox-based polymerization initiator in combination with a reducing agent such as sodium bisulfite or ferrous sulfate. Further, a chelating agent such as ethylenediaminetetraacetate sodium tetrahydrate and a builder such as sodium carbonate and sodium sulfate can be used in combination. The amount of the polymerization initiator added is preferably 0.01 to 2 parts by weight with respect to 100 parts by weight of the monomer used for the polymerization.

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

In the emulsion polymerization, further, if necessary, polymerization auxiliary materials such as stabilizers, dispersants, pH adjusters, oxygen scavengers, and particle size adjusters can be used. When these are used, the type and amount used are not particularly limited.

Further, the obtained copolymer is hydrogenated (hydrogenation reaction) of the copolymer, if necessary. Hydrogenation may be carried out by a known method, but since the total content of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber and the chloride ion content can be preferably controlled, the aqueous hydrogenation method can be used. Is preferable. The aqueous layer hydrogenation method includes a direct hydrogenation method of an aqueous layer in which hydrogen is supplied to a reaction system in the presence of a hydrogenation catalyst to hydrogenate it, and a method of reducing hydrogenation in the presence of an oxidizing agent, a reducing agent and an activator. An aqueous layer indirect hydrogenation method for hydrogenation can be mentioned, and among these, the aqueous layer direct hydrogenation method is preferable.

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 not easily decomposed by water. As a specific example, in the palladium catalyst, 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 chloride, dichloro ( Palladium chlorinated products such as cyclooctadiene) palladium, dichloro (norbornadien) palladium, and ammonium hexachloropalladium (IV); iodides such as palladium iodide; palladium sulfate and dihydrates can be mentioned. Among these, palladium metal, palladium salt of carboxylic acid, palladium chloride, dichloro (norbornadien) palladium and ammonium hexachloropalladium (IV) acid are particularly preferable. 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, based on the copolymer obtained by the polymerization.

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

Then, in the present invention, a water-containing crumb of a carboxyl group-containing nitrile rubber is obtained by adding a coagulant to the latex after the hydrogenation reaction thus obtained and coagulating it. The coagulant used for coagulation is not particularly limited, and examples thereof include sodium chloride, potassium chloride, calcium chloride, magnesium chloride, sodium sulfate, magnesium sulfate, aluminum sulfate, sodium nitrate, and barium chloride. The amount of the coagulant to be used may be appropriately selected according to the type of the coagulant to be used and the amount of sodium, calcium, magnesium, and chloride ions contained in the finally obtained carboxyl group-containing nitrile rubber. However, with respect to 100 parts by weight of the carboxyl group-containing nitrile rubber contained in the latex, it is preferably 0.5 to 200 parts by weight, more preferably 1 to 100 parts by weight, still more preferably 3 to 50 parts by weight, and particularly preferably. 5 to 35 parts by weight. As the coagulant, chloride is preferable, and metal chloride is more preferable, and examples thereof include sodium chloride, potassium chloride, calcium chloride, magnesium chloride and the like. When chloride is used as the coagulant, only chloride may be used, or chloride and a coagulant other than chloride may be used in combination. Further, the chloride may be used alone or in combination of two or more. The amount of chloride used may be appropriately selected according to the type of chloride used and the amount of sodium, calcium, magnesium, and chloride ions contained in the finally obtained carboxyl group-containing nitrile rubber. However, with respect to 100 parts by weight of the carboxyl group-containing nitrile rubber contained in the latex, preferably 0.5 to 200 parts by weight, more preferably 1 to 100 parts by weight, still more preferably 3 to 50 parts by weight, particularly preferably. It is 5 to 35 parts by weight, most preferably 5 to 15 parts by weight. Further, when the coagulant is added, it may be dissolved in water and added in the state of an aqueous coagulant solution. In this case, hydrochloric acid (aqueous solution) and nitric acid (aqueous solution) are used to further enhance the coagulability. And an acid such as nitric acid (aqueous solution) may be added to adjust the pH to preferably 1 to 4, more preferably 2 to 3.

Next, the hydrous crumb obtained by solidification 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 latex. That is, the carboxyl group-containing nitrile rubber of the present invention is preferably a dry rubber, and more preferably a rubber having a water content of 1% by weight or less. When washing with water, the washing conditions such as the number of washings with water can be appropriately selected according to the amounts of sodium, calcium, magnesium, and chloride ions contained in the finally obtained carboxyl group-containing nitrile rubber.
It is also possible to add an anti-aging agent to the oil layer or water layer before solidification. The anti-aging agent is not particularly limited, but is 2,6-di-t-butyl-4-cresol (Antage BHT, manufactured by Kawaguchi Chemical Industry Co., Ltd.), 2,2'-methylenebis (4-methyl-6-tert-). Butylphenol) (Sandant 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), hexamethylenebis [3- (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.

Since the carboxyl group-containing nitrile rubber of the present invention has the above-mentioned structure, it is possible to provide a rubber crosslinked product having excellent cold resistance, LLC resistance and compression permanent strain resistance, for example, to form a sealing material. Can be suitably used for.

<Crosslinkable nitrile rubber composition>
The crosslinkable nitrile rubber composition of the present invention is obtained by blending a polyvalent amine compound with the above-mentioned carboxyl group-containing nitrile rubber. In the crosslinkable nitrile rubber composition of the present invention, the polyvalent amine compound acts as a crosslinker.

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 at the time of cross-linking, but is not particularly limited, but is an aliphatic hydrocarbon or aroma. 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 -CONNHN ₂ , CO represents a carbonyl group) and a compound in the form of the compound at the time of cross-linking are preferable. ..

Specific examples of the polyhydric amine compound include aliphatic polyhydrics such as hexamethylene dihydric acid, hexamethylene dihydric carbamate, N, N-dicinnamylidene-1,6-hexanediamine, tetramethylene pentamine, and hexamethylene dihydric acid dihydroxide Aminates; 4,4-methylenedianiline, m-phenylenediamine, 4,4-diaminodiphenyl ether, 3,4-diaminodiphenyl ether, 4,4- (m-phenylenediisopropyridene) dianiline, 4,4- (p) -Phenylenediisopropylidene) dianiline, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 4,4-diaminobenzanilide, 4,4-bis (4-aminophenoxy) biphenyl, m-xyli Aromatic polyhydric amines such as rangeamine, p-xylylene diamine, 1,3,5-benzenetriamine; isophthalic acid dihydrazide, terephthalic acid dihydrazide, phthalic acid dihydrazide, 2,6-naphthalenedicarboxylic acid dihydrazide, naphthalene acid dihydrazide , Adipic acid dihydrazide, dihydrazide malonic acid, dihydrazide succinic acid, dihydrazide glutamate, dihydrazide adipic acid, dihydrazide pymeric acid, dihydrazide siberic acid, dihydrazide hydrazide, dihydrazide sebacic acid, dihydrazide brasilic acid Examples thereof include polyhydric hydrazides such as fumaric acid dihydrazide, maleic acid dihydrazide, itaconic acid dihydrazide, trimellitic acid dihydrazide, 1,3,5-benzenetricarboxylic acid dihydrazide, aconit acid dihydrazide, and pyromellitic acid dihydrazide. Among these, aliphatic polyvalent amines and aromatic polyvalent amines are preferable from the viewpoint that the effect of the present invention can be further enhanced, and hexamethylenediamine carbamate and 2,2-bis [ 4- (4-Aminophenoxy) phenyl] propane is more preferred, and hexamethylenediamine carbamate is particularly preferred.

The content of the polyvalent amine compound in the crosslinkable nitrile rubber composition of the present invention is not particularly limited, but is preferably 0.1 to 10 parts by weight, more preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the carboxyl group-containing nitrile rubber. It is 0.2 to 5 parts by weight.

Moreover, it is preferable that the crosslinkable nitrile rubber composition of the present invention further contains a basic crosslinking accelerator.
Specific examples of the basic cross-linking accelerator include 1,8-diazabicyclo [5,4,0] undecene-7 (hereinafter sometimes abbreviated as "DBU"), 1,5-diazabicyclo [4,3,0]. Nonen-5 (hereinafter sometimes abbreviated as "DBN"), 1-methylimidazole, 1-ethyl imidazole, 1-phenyl imidazole, 1-benzyl imidazole, 1,2-dimethyl imidazole, 1-ethyl-2-methyl imidazole , 1-methoxyethyl imidazole, 1-phenyl-2-methyl imidazole, 1-benzyl-2-methyl imidazole, 1-methyl-2-phenyl imidazole, 1-methyl-2-benzyl imidazole, 1,4-dimethyl imidazole, 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-methylbenzoimidazole, 1-methyl-2-benzylbenzoimidazole, 1-methyl-5-nitrobenzoimidazole, 1-methylimidazoline, 1 , 2-Dimethylimidazolin, 1,2,4-trimethylimidazolin, 1,4-dimethyl-2-ethylimidazolin, 1-methyl-phenylimidazolin, 1-methyl-2-benzylimidazolin, 1-methyl-2-ethoxyimidazolin , 1-Methyl-2-heptyl imidazoline, 1-methyl-2-undecyl imidazoline, 1-methyl-2-heptadecyl imidazoline, 1-methyl-2-ethoxymethyl imidazoline, 1-ethoxymethyl-2-methyl imidazoline, etc. Basic cross-linking accelerator having a cyclic amidin structure; a guanidine-based basic cross-linking accelerator such as tetramethylguanidine, tetraethylguanidine, diphenylguanidine, 1,3-di-ortho-tolylguanidine, orthotrilbiguanide; n-butylaldehyde. Aldamine amine-based basic cross-linking accelerators such as aniline and acetaldehyde ammonia; dicyclopentylamine, dicyclohexylamine, dicycloheptylami Dicycloalkylamines such as N-methylcyclopentylamine, N-butylcyclopentylamine, N-heptylcyclopentylamine, N-octylcyclopentylamine, N-ethylcyclohexylamine, N-butylcyclohexylamine, N-heptylcyclohexylamine, N-octylcyclooctylamine, N-hydroxymethylcyclopentylamine, N-hydroxybutylcyclohexylamine, N-methoxyethylcyclopentylamine, N-ethoxybutylcyclohexylamine, N-methoxycarbonylbutylcyclopentylamine, N-methoxycarbonylheptylcyclohexylamine , N-Aminopropylcyclopentylamine, N-aminoheptylcyclohexylamine, di (2-chlorocyclopentyl) amine, di (3-chlorocyclopentyl) amine and other secondary amine-based basic cross-linking accelerators; and the like. Among these, a guanidine-based basic cross-linking promoter, a secondary amine-based basic cross-linking promoter, and a basic cross-linking promoter having a cyclic amidine structure are preferable, and a basic cross-linking promoter having a cyclic amidine structure is more preferable. 1,8-Diazabicyclo [5,4,0] undecene-7 and 1,5-diazabicyclo [4,5,0] nonen-5 are more preferred, 1,8-diazabicyclo [5,4,0] undecene-7. Is particularly preferable. The basic cross-linking accelerator having a cyclic amidine structure may form a salt with an organic carboxylic acid, an alkyl phosphoric acid, or the like. Further, 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 may be. Then, the secondary amine-based basic cross-linking accelerator and the inorganic acid and / or organic acid may form a salt and further form a complex with the alkylene glycol.

When the basic crosslinking accelerator is blended, the blending amount in the crosslinkable nitrile rubber composition of the present invention is preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the carboxyl group-containing nitrile rubber. It is more preferably 0.2 to 15 parts by weight, still more preferably 0.5 to 10 parts by weight.

Further, the crosslinkable nitrile rubber composition of the present invention may contain other compounding agents usually used in the rubber processing field. Examples of such compounding agents include reinforcing agents, fillers, light stabilizers, scorch inhibitors, plasticizers, processing aids, lubricants, pressure-sensitive adhesives, lubricants, flame retardants, acid-receiving agents, fungicides, and the like. Examples thereof include antistatic agents, colorants, silane coupling agents, cross-linking aids, co-crosslinking agents, cross-linking accelerators, cross-linking retarders, foaming agents and the like. As the blending amount of these blending agents, an amount suitable for the blending purpose can be appropriately adopted.

The plasticizer is not particularly limited, but a trimellitic acid-based plasticizer, an ether ester-based plasticizer, or the like can be used. Specific examples include tri-2-ethylhexyl trimellitic acid, isononyl ester of trimellitic acid, bis [2- (2-butoxyethoxy) ethyl] adipate, diheptanoate, di-2-ethylhexanoate, and didecanoate. Can be mentioned. These can be used alone or in combination of two or more.

Further, the crosslinkable nitrile rubber composition of the present invention may contain a rubber other than the above-mentioned carboxyl group-containing nitrile rubber of the present invention as long as the effects of the present invention are not impaired.
Examples of such rubber include acrylic rubber, ethylene-acrylic acid copolymer rubber, fluororubber, styrene-butadiene copolymer rubber, polybutadiene rubber, ethylene-propylene copolymer rubber, and ethylene-propylene-diene ternary weight. Examples thereof include coalesced rubber, epichlorohydrin rubber, urethane rubber, chloroprene rubber, silicone rubber, fluorosilicone rubber, chlorosulphonized polyethylene rubber, natural rubber and polyisoprene rubber.

When a rubber other than the carboxyl group-containing nitrile rubber of the present invention is blended, the blending amount in the crosslinkable nitrile rubber composition is preferably 30 parts by weight or less with respect to 100 parts by weight of the carboxyl group-containing nitrile rubber of the present invention. , More preferably 20 parts by weight or less, still more preferably 10 parts by weight or less.

Further, the crosslinkable nitrile rubber composition of the present invention is prepared by mixing each of the above components preferably in a non-aqueous system. The method for preparing the crosslinkable nitrile rubber composition of the present invention is not limited, but usually, the components excluding the polyvalent amine compound and the heat-unstable basic crosslink accelerator are added to the Banbury mixer, intermixer, and kneader. It can be prepared by primary kneading with a mixer such as the above, then transferring to an open roll or the like, adding a polyvalent amine compound, a heat-unstable basic cross-linking accelerator, or the like, and secondary kneading. 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, and the secondary kneading is usually carried out at 10 to 90 ° C. 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.

Since the crosslinkable nitrile rubber composition of the present invention has the above-mentioned structure, it is possible to provide a rubber crosslinked product having excellent cold resistance, LLC resistance and compression permanent strain resistance, for example, forming a sealing material. Therefore, it can be preferably used.

<Rubber crosslinked product>
The rubber crosslinked product of the present invention is obtained by cross-linking the above-mentioned crosslinkable nitrile rubber composition of the present invention.
The rubber crosslinked product of the present invention is formed by using the crosslinkable nitrile rubber composition of the present invention with a molding machine corresponding to a desired shape, for example, an extruder, an injection molding machine, a compressor, a roll or the like, and is heated. This can be produced by carrying out a cross-linking reaction and fixing the shape as a cross-linked product. In this case, cross-linking may be performed after molding in advance, or cross-linking may be performed at the same time as molding. The molding temperature is usually 10 to 200 ° C, preferably 25 to 120 ° C. The crosslinking temperature is usually 100 to 200 ° C., preferably 130 to 190 ° C., and the crosslinking time is usually 1 minute to 24 hours, preferably 2 minutes to 1 hour.

Further, depending on the shape and size of the crosslinked product, even if the surface is crosslinked, it may not be sufficiently crosslinked to the inside, so that the secondary crosslinking may be performed by further heating.
As the 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 cross-linking the above-mentioned crosslinkable nitrile rubber composition of the present invention, and is excellent in cold resistance, LLC resistance and compression set resistance. Is.
Therefore, the rubber crosslinked product of the present invention makes use of such characteristics, such as O-ring, packing, diaphragm, oil seal, shaft seal, bearing seal, well head seal, shock absorber seal, long life coolant (LLC), etc. Coolant seals and oil coolant seals that seal the coolant, seals for pneumatic equipment, seals for sealing freon or fluorocarbohydrate or carbon dioxide used in air conditioner cooling devices and air conditioner refrigerator compressors. , Seals for sealing supercritical carbon dioxide or subcritical carbon dioxide used in cleaning media for precision cleaning, for rolling devices (rolling bearings, automobile hub units, automobile water pumps, linear guide devices, ball screws, etc.) Various sealing materials such as seals, valves and valve seats, BOP (Blow Out Presenter), platters; Intake manifold gaskets attached to the joints between the intake manifold and the cylinder head, and the joints between the cylinder block and the cylinder head. The cylinder head gasket, the rocker cover gasket attached to the joint between the rocker cover and the cylinder head, the oil pan gasket attached to the joint between the oil pan and the cylinder block or the transmission case, the positive electrode, the electrolyte plate and the negative electrode. Various gaskets such as fuel cell separator gaskets and hard disk drive top cover gaskets that are mounted between a pair of housings that sandwich the unit cells provided; printing rolls, iron making rolls, paper making rolls, industrial rolls, office machines Various rolls such as rolls for use; flat belts (film core flat belts, cord flat belts, laminated flat belts, stand-alone flat belts, etc.), V belts (wrapped V belts, low edge V belts, etc.), V ribbed belts (single V ribbed belts, etc.) , Double V ribbed belt, wrapped V ribbed belt, back rubber V ribbed belt, upper cog V ribbed belt, etc.), CVT belt, timing belt, toothed belt, conveyor belt, etc.; fuel hose, turbo air hose, oil hose, etc. Various hoses such as radiator hose, heater hose, water hose, vacuum brake hose, control hose, air conditioner hose, brake hose, power steering hose, air hose, marine hose, riser, flow line, etc. Various boots such as CVJ boots, propeller shaft boots, constant velocity joint boots, rack and pinion boots; cushioning materials, dynamic dampers, rubber couplings, air springs, vibration isolators, clutch facing materials and other damping materials rubber parts; dust covers It can be used in a wide range of applications such as automobile interior members, friction materials, tires, coated cables, shoe soles, electromagnetic wave shields, adhesives for flexible printed substrates, fuel cell separators, and the electronics field. Among these, the rubber crosslinked product of the present invention is excellent in cold resistance, LLC resistance, and compression set resistance, and therefore, it is used as a coolant, antifreeze, etc. used in the cooling system of an internal combustion engine of an automobile or the like. It is particularly suitable as a sealing material for sealing an aqueous refrigerant (particularly LLC). Since the crosslinked rubber product of the present invention does not easily swell even when it comes into contact with a high temperature LCC, it is particularly suitable as a sealing material for sealing a high temperature (for example, 100 to 150 ° C.) LCC.

Hereinafter, the present invention will be described based on more detailed examples, but the present invention is not limited to these examples. In the following, "part" is based on weight unless otherwise specified. The tests and evaluations were as follows.

[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 is such that 100 mL of pyridine is added to 0.2 g of 2 mm square carboxyl group-containing nitrile rubber and stirred for 16 hours, and then 0.02N alcoholic potassium hydroxide is added while stirring. Using a potassium hydroxide solution, the number of moles of carboxyl groups per 100 g of carboxyl group-containing nitrile rubber was determined by titration using timolephthalene as an indicator at room temperature, and the determined number of moles was converted to the amount of mono-n-butyl maleate. Calculated by conversion.
The content ratios of 1,3-butadiene units and saturated butadiene units were calculated by measuring the iodine value (according to JIS K 6235) before and after the hydrogenation reaction using a carboxyl group-containing nitrile rubber. ..
The content ratio of the acrylonitrile unit 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 ratio of n-butyl acrylate units was calculated from the content ratios of mono n-butyl maleate, 1,3-butadiene units, saturated butadiene units, and acrylonitrile units obtained above.

[Total content of sodium, calcium, and magnesium in carboxyl group-containing nitrile rubber]
The total content of sodium, calcium, and magnesium in the carboxyl group-containing nitrile rubber is determined by adding sulfuric acid and nitric acid to the carboxyl group-containing nitrile rubber, heating the rubber, wet-decomposing the rubber, and then appropriately diluting the ICP-. AES (SPS-5000: manufactured by Seiko Instruments Co., Ltd.) was used, and the measurement was performed by the internal standard calibration curve method.

[Chloride ion content in carboxyl group-containing nitrile rubber]
The carboxyl group-containing nitrile rubber was stretched with a roll to form a sheet, which was cut to 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 the mixture was stirred to completely dissolve the measurement sample, then 30 ml of isopropyl alcohol was added, and further, methyl ethyl ketone was added to make the total volume 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 the titrator, COMITE-101 manufactured by Hiranuma Sangyo Co., Ltd. was used, and the silver support electrode AG-68 / silver comparison electrode AM-44 was used.

[Cold resistance test]
The crosslinkable rubber composition was placed in a mold having a length of 15 cm, a width of 15 cm, and a depth of 0.2 cm, press-molded at 170 ° C. for 20 minutes while pressurizing at a press pressure of 10 MPa, and then secondarily crosslinked at 170 ° C. for 4 hours. By doing so, a sheet-shaped rubber crosslinked product was obtained. Then, using the obtained sheet-shaped rubber crosslinked product, the cold resistance of the rubber crosslinked product was measured by a TR test (low temperature elastic recovery test) according to JIS K6261. Specifically, the stretched test piece is frozen and the recoverability of the stretched test piece is measured by continuously raising the temperature, and the length of the test piece shrinks (recovers) by 10% due to the temperature rise. ), The temperature TR10 was measured. It can be judged that the lower the TR10, the better the cold resistance.

[LLC resistance]
In the same manner as in the above cold resistance test, a sheet-shaped rubber crosslinked product was obtained, and the obtained sheet-shaped rubber crosslinked product was immersed in LLC (Long Life Coolant) at a temperature of 125 ° C. for 168 hours. As the LLC, a 50% aqueous solution of "Dex-Cool" manufactured by AcDelco was used. 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 rate after immersion in LLC, the better the LLC resistance.
Swelling degree after LLC immersion (%) = (Weight of rubber crosslinked product after LLC immersion-Weight of rubber crosslinked product before LLC immersion) ÷ Weight of rubber crosslinked product before LLC immersion × 100

[Compressive permanent strain (O-ring compression permanent strain)]
The crosslinkable rubber composition was crosslinked at 170 ° C. for 20 minutes at a press pressure of 10 MPa using a die having an inner diameter of 30 mm and a ring diameter of 3 mm, and then secondary crosslinked at 170 ° C. for 4 hours to form an O-ring. Specimen was 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. The smaller this value, the better the compression set resistance.
In this embodiment, the compression set is measured with an O-ring-shaped test piece, but according to the knowledge of the present inventors, the O-ring is obtained even when the compression set in the disk shape is low. In the case of a test piece in the shape of a shape, the compression set may be high. Therefore, in this embodiment, the compression set is measured with an O-ring-shaped test piece based on such knowledge. Is what you do.

[Manufacturing Example 1]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A-1))
In a metal bottle, 180 parts of ion-exchanged water, 25 parts of an aqueous solution of sodium dodecylbenzenesulfonate having a concentration of 10% by weight, 5 parts of a sodium salt of a sodium sodium sodium carbonate condensate having a concentration of 10%, 20 parts of acrylonitrile, mono n-maleate 5 parts of butyl, 31 parts of n-butyl acrylate, 0.75 parts of t-dodecyl mercaptan (molecular weight adjuster) were charged in this order, and after replacing the internal gas with nitrogen 3 times, 44 parts of 1,3-butadiene was charged. It is. Keep the metal bottle at 10 ° C, add 0.1 part of TEMPO hydroperoxide (polymerization initiator), reducing agent, chelating agent, and appropriate amount of builder, continue the polymerization reaction with stirring, and the polymerization conversion rate is 80%. At that time, 4 parts of an aqueous solution of 2,2,6,6-tetramethylpiperidine-1-oxyl (polymerization terminator) having a concentration of 2.5% by weight was added to terminate the polymerization reaction. Next, the residual monomer was removed at a water temperature of 60 ° C. to obtain a latex (solid content concentration: 25% by weight) of the copolymer rubber.

Next, the latex and palladium catalyst (1 wt% acetic acid) obtained above were placed in the autoclave so that the palladium content with respect to the dry weight of the rubber contained in the latex obtained above was 3000 wt ppm. A solution obtained by mixing a palladium-acetone solution and an equal weight of ion-exchanged water) was added, and a hydrogenation reaction was carried out at a hydrogen pressure of 3 MPa and a temperature of 50 ° C. for 6 hours. . Add 0.3 parts of 4,6-bis (octylthiomethyl) -o-cresol (Irganox 1520L, BASF Japan, anti-aging agent) and Actiside MBS (So Japan, preservative) in 1 part. did. By adding an appropriate amount of an aqueous sulfuric acid solution to this, a latex of a carboxyl group-containing nitrile rubber (solid content concentration: 12.5% by weight, pH 4.0) was obtained.

Then, 10 parts of a calcium chloride aqueous solution (0.8 wt% aqueous solution, pH = 2.5) was added to the obtained latex of the carboxyl group-containing nitrile rubber, and 10 parts in terms of calcium chloride was added to 100 parts of the carboxyl group-containing nitrile rubber. The carboxyl group-containing nitrile rubber was solidified by adding the amount to be, and a crumb slurry containing a crumb-shaped carboxyl group-containing nitrile rubber was obtained. Next, 100 parts of the obtained crumb slurry was washed once with 2000 parts of water, and the water-containing crumb after washing was washed once with water, filtered, and then vacuum dried at 60 ° C. for 12 hours. By doing so, a carboxyl group-containing nitrile rubber (A-1) was obtained.

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

[Manufacturing Example 2]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A-2))
Carboxylic group-containing nitrile rubber (A-2) in the same manner as in Production Example 1 except that the amount of n-butyl acrylate used was changed to 32 parts and the amount of 1,3-butadiene used was changed to 43 parts. Got The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-2), and the total content of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A-2). , And the chloride ion content are shown in Table 1.

[Manufacturing Example 3]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A-3))
Carboxylic group-containing nitrile rubber (A-3) in the same manner as in Production Example 1, except that the amount of n-butyl acrylate used was changed to 35 parts and the amount of 1,3-butadiene used was changed to 40 parts. Got The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-3), and the total content of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A-3). , And the chloride ion content are shown in Table 1.

[Manufacturing Example 4]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A-4))
Carboxylic group-containing nitrile rubber (A-4) in the same manner as in Production Example 1, except that the amount of n-butyl acrylate used was changed to 40 parts and the amount of 1,3-butadiene used was changed to 35 parts. Got The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-4), and the total content of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A-4). , And the chloride ion content are shown in Table 1.

[Manufacturing Example 5]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A-5))
Carboxylic group-containing nitrile rubber (A-5) in the same manner as in Production Example 1, except that the amount of n-butyl acrylate used was changed to 48 parts and the amount of 1,3-butadiene used was changed to 27 parts. Got The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-5), and the total content of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A-5). , And the chloride ion content are shown in Table 1.

[Manufacturing Example 6]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A-6))
Carboxylic group-containing nitrile rubber (A-6) in the same manner as in Production Example 1, except that the amount of n-butyl acrylate used was changed to 54 parts and the amount of 1,3-butadiene used was changed to 21 parts. Got The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-6), and the total content of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A-6). , And the chloride ion content are shown in Table 1.

[Manufacturing Example 7]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A-7))
When coagulating the latex of carboxyl group-containing nitrile rubber, instead of calcium chloride aqueous solution, magnesium sulfate aqueous solution (3.3 wt% aqueous solution, pH = 2.5) and sodium chloride aqueous solution (0.8 wt% aqueous solution, In the same manner as in Production Example 3, carboxyl (pH = 2.5) was used in an amount of 20 parts in terms of magnesium sulfate and 5 parts in terms of sodium chloride with respect to 100 parts of carboxyl group-containing nitrile rubber. A group-containing nitrile rubber (A-7) was obtained. The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-7), and the total content of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A-7). , And the chloride ion content are shown in Table 1.

[Manufacturing Example 8]
(Manufacture of Carboxylic Acid Group-Containing Nitrile Rubber (A-8))
When coagulating the latex of a carboxyl group-containing nitrile rubber, instead of magnesium sulfate (3.3 wt% aqueous solution, pH = 2.5), magnesium sulfate aqueous solution (5.0 wt% aqueous solution, pH = 2.5) ) Was used in an amount of 30 parts in terms of magnesium sulfate with respect to 100 parts of the carboxyl group-containing nitrile rubber, and the carboxyl group-containing nitrile rubber (A-8) was obtained in the same manner as in Production Example 7. .. The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-8), and the total content of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A-8). , And the chloride ion content are shown in Table 1.

[Manufacturing Example 9]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A-9))
When coagulating the latex of the carboxyl group-containing nitrile rubber, instead of the sodium chloride aqueous solution (0.8 wt% aqueous solution, pH = 2.5), the sodium chloride aqueous solution (0.2 wt% aqueous solution, pH = 2. The carboxyl group-containing nitrile rubber (A-9) was obtained in the same manner as in Production Example 7, except that 5) was used in an amount of 1 part in terms of sodium chloride with respect to 100 parts of the carboxyl group-containing nitrile rubber. It was. The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-9), and the total content of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A-9). , And the chloride ion content are shown in Table 1.

[Manufacturing Example 10]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A-10))
When coagulating the latex of carboxyl group-containing nitrile rubber, calcium chloride aqueous solution (0.8 wt% aqueous solution, pH = 2.5) and magnesium sulfate aqueous solution (1.7 wt% aqueous solution, pH =) are used as the coagulating salt aqueous solution. 2.5) was used in an amount of 5 parts in terms of calcium chloride and 10 parts in terms of magnesium sulfate with respect to 100 parts of carboxyl group-containing nitrile rubber, and contained carboxyl groups in the same manner as in Production Example 3. A nitrile rubber (A-10) was obtained. The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-10), and the total content of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A-10). , And the chloride ion content are shown in Table 1.

[Manufacturing Example 11]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A-11))
When coagulating the latex of carboxyl group-containing nitrile rubber, calcium chloride aqueous solution (0.8 wt% aqueous solution, pH = 2.5) and sodium chloride aqueous solution (0.8 wt% aqueous solution, pH =) are used as the coagulating salt aqueous solution. 2.5) was used in an amount of 5 parts in terms of calcium chloride and 5 parts in terms of sodium chloride with respect to 100 parts of carboxyl group-containing nitrile rubber, and contained a carboxyl group in the same manner as in Production Example 3. A nitrile rubber (A-11) was obtained. The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-11), and the total content of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A-11). , And the chloride ion content are shown in Table 1.

[Manufacturing Example 12]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A-12))
When coagulating the latex of the carboxyl group-containing nitrile rubber, instead of the sodium chloride aqueous solution (0.8 wt% aqueous solution, pH = 2.5), the sodium chloride aqueous solution (1.7 wt% aqueous solution, pH = 2. The carboxyl group-containing nitrile rubber (A-12) was obtained in the same manner as in Production Example 11 except that 5) was used in an amount of 10 parts in terms of sodium chloride with respect to 100 parts of the carboxyl group-containing nitrile rubber. It was. The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A-12), and the total content of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A-12). , And the chloride ion content are shown in Table 1.

[Manufacturing Example 13]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A'-13))
Carboxylic group-containing nitrile rubber (A'-13) in the same manner as in Production Example 1 except that the amount of n-butyl acrylate used was changed to 29 parts and the amount of 1,3-butadiene used was changed to 46 parts. ) Was obtained. The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A'-13), and the total of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A'-13). The content and chloride ion content are shown in Table 1.

[Manufacturing Example 14]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A'-14))
Carboxylic group-containing nitrile rubber (A'-14) was obtained in the same manner as in Production Example 1 except that the amount of n-butyl acrylate used was changed to 60 parts and the amount of 1,3-butadiene used was changed to 15 parts. ) Was obtained. The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A'-14), and the total of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A'-14). The content and chloride ion content are shown in Table 1.

[Manufacturing Example 15]
(Manufacture of Carboxylic Acid-Free Nitrile Rubber (A'-15))
Carboxylic acid-free nitrile rubber (A'-15) in the same manner as in Production Example 3, except that the amount of 1,3-butadiene used was changed to 45 parts without blending mono-n-butyl maleate. Got The composition, iodine value, and carboxyl group content of the obtained carboxyl group-free nitrile rubber (A'-15), sodium, calcium, and magnesium in the obtained carboxyl group-free nitrile rubber (A'-15). The total content of and the chloride ion content are shown in Table 1.

[Manufacturing Example 16]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A'-16))
When coagulating the latex of the carboxyl group-containing nitrile rubber, instead of the magnesium sulfate aqueous solution (3.3 wt% aqueous solution, pH = 2.5), the magnesium sulfate aqueous solution (6.7 wt% aqueous solution, pH = 2. The carboxyl group-containing nitrile rubber (A'-16) was used in the same manner as in Production Example 7, except that 5) was used in an amount of 40 parts in terms of magnesium sulfate with respect to 100 parts of the carboxyl group-containing nitrile rubber. Obtained. The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A'-16), and the total of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A'-16). The content and chloride ion content are shown in Table 1.

[Manufacturing Example 17]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A'-17))
When coagulating the latex of the carboxyl group-containing nitrile rubber, instead of the magnesium sulfate aqueous solution (3.3 wt% aqueous solution, pH = 2.5), the magnesium sulfate aqueous solution (1.7 wt% aqueous solution, pH = 2. 5) was used in an amount of 20 parts in terms of magnesium sulfate with respect to 100 parts of carboxyl group-containing nitrile rubber, and contained a carboxyl group in the same manner as in Production Example 7, except that an aqueous sodium chloride solution was not used. Nitrile rubber (A'-17) was obtained. The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A'-17), and the total of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A'-17). The content and chloride ion content are shown in Table 1.

[Manufacturing Example 18]
(Manufacture of Carboxylic Group-Containing Nitrile Rubber (A'-18))
When coagulating the latex of the carboxyl group-containing nitrile rubber, instead of the sodium chloride aqueous solution (0.8 wt% aqueous solution, pH = 2.5), the sodium chloride aqueous solution (2.5 wt% aqueous solution, pH = 2. The carboxyl group-containing nitrile rubber (A'-18) was used in the same manner as in Production Example 11 except that 5) was used in an amount of 15 parts in terms of sodium chloride with respect to 100 parts of the carboxyl group-containing nitrile rubber. Obtained. The composition, iodine value, and carboxyl group content of the obtained carboxyl group-containing nitrile rubber (A'-18), and the total of sodium, calcium, and magnesium in the obtained carboxyl group-containing nitrile rubber (A'-18). The content and chloride ion content are shown in Table 1.

[Example 1]
Using a Banbury mixer, 100 parts of the carboxyl group-containing nitrile rubber (A-1) obtained in Production Example 1, 40 parts of FEF carbon black (trade name "Seast SO", manufactured by Tokai Carbon Co., Ltd.), and trimellitic acid. Tri-2-ethylhexyl (trade name "Adecassizer C-8", manufactured by ADEKA, plasticizer) 5 parts, 4,4'-di- (α, α-dimethylbenzyl) diphenylamine (trade name "Nocrack CD", Ouchi Shinko Kagaku Co., Ltd., anti-aging agent) 1.5 parts, stearic acid 1 part, polyoxyethylene alkyl ether phosphoric acid ester (trade name "Phosphanol RL210", Toho Chemical Industry Co., Ltd., processing aid) 1 Parts were added and mixed at 50 ° C. for 5 minutes. Next, the obtained mixture was transferred to a roll at 50 ° C., and 1.9 parts of hexamethylenediamine carbamate (manufactured by Dupondau Elastomer, trade name “Diak # 1”, polyamine cross-linking agent belonging to aliphatic polyvalent amines) was transferred. , And 1,8-diazabicyclo [5,4,0] -undesen-7 (DBU) (trade name "RHENOGRAN XLA-60 (GE2014)", manufactured by Rhein Chemie, DBU 60% (zincdialkyldiphosphate salt) A crosslinkable rubber composition was obtained by blending 4 parts of the basic crosslinking accelerator) and kneading the mixture.

Then, using the obtained crosslinkable rubber composition, cold resistance, water resistance and compression set (O-ring compression set) were measured by the above-mentioned method. The results are shown in Table 1.

[Examples 2 to 12]
The carboxyl group-containing nitrile rubbers (A-2) to (A-12) obtained in Production Examples 2 to 12 were used instead of the carboxyl group-containing nitrile rubbers (A-1) obtained in Production Example 1. A crosslinkable rubber composition was obtained in the same manner as in Example 1 except for the above, and the evaluation was carried out in the same manner. The results are shown in Table 1.

[Comparative Examples 1, 2, 4 to 6]
Instead of the carboxyl group-containing nitrile rubber (A-1) obtained in Production Example 1, the carboxyl group-containing nitrile rubbers (A'-13), (A'-) obtained in Production Examples 13, 14, 16 to 18. A crosslinkable rubber composition was obtained in the same manner as in Example 1 except that 14) and (A'-16) to (A'-18) were used, respectively, and evaluated in the same manner. The results are shown in Table 1.

[Comparative Example 3]
Using a Banbury mixer, 100 parts of the carboxyl group-free nitrile rubber (A'-15) obtained in Production Example 15, 40 parts of FEF carbon black (trade name "Seast SO", manufactured by Tokai Carbon Co., Ltd.), Trimellitic acid Tri-2-ethylhexyl acid acid (trade name "Adecasizer C-8", manufactured by ADEKA, plasticizer) 5 parts, 4,4'-di- (α, α-dimethylbenzyl) diphenylamine (trade name "Nocrack CD" , Ouchi Shinko Kagaku Co., Ltd., anti-aging agent) 1.5 parts, 2-mercaptobenzimidazole zinc oxide (trade name "Nocrack MBZ", Ouchi Shinko Kagaku Co., Ltd., anti-aging agent) 1.5 parts, stear 1 part of acid and 5 parts of zinc oxide (Zinchua No. 1, manufactured by Shodo Chemical Co., Ltd.) were added and mixed at 50 ° C. for 5 minutes. Then, the obtained mixture was transferred to a roll at 50 ° C., and a 1,3-bis (t-butylperoxyisopropyl) benzene 40% product (trade name "Vul Cup 40KE", manufactured by Alchema, an organic peroxide cross-linking agent) was transferred. ) 8 parts were added and kneaded to obtain a crosslinkable rubber composition.

As shown in Table 1, it contains α, β-ethylenically unsaturated monocarboxylic acid ester monomer units in a proportion of 26 to 50% by weight, has an iodine value of 120 or less, and contains sodium, calcium, and magnesium. Rubber cross-linking obtained by using a crosslinkable nitrile rubber composition containing a carboxyl group-containing nitrile rubber having a total content of 1000 wt ppm or less and a chloride ion content of 50 to 500 wt ppm and a polyvalent amine compound. The product was excellent in cold resistance, LLC resistance and compression set resistance (Examples 1 to 12).
On the other hand, when the content of the α, β-ethylenically unsaturated monocarboxylic acid ester monomer unit is too small, the obtained crosslinked rubber product becomes inferior in cold resistance and also has α, β-ethylene property. When the content of the unsaturated monocarboxylic acid ester monomer unit was too large, the obtained crosslinked rubber product was inferior in LLC resistance (Comparative Examples 1 and 2).
When a nitrile rubber containing no carboxyl group was used, the obtained crosslinked rubber product was inferior in compression resistance to permanent strain (Comparative Example 3).
Further, when a carboxyl group-containing nitrile rubber having a total content of sodium, calcium, and magnesium of more than 1000 ppm by weight was used, and a carboxyl group-containing nitrile rubber having a chloride ion content of less than 50 ppm by weight was used. In some cases, the obtained rubber crosslinked product was inferior in compression resistance to permanent strain (Comparative Examples 4 and 5).
Further, when a carboxyl group-containing nitrile rubber having a chloride ion content of more than 500 ppm by weight was used, the obtained crosslinked rubber was inferior in LLC resistance (Comparative Example 6).

Claims (10)

It contains α, β-ethylenically unsaturated monocarboxylic acid ester monomer units in a proportion of 26 to 50% by weight, has an iodine value of 120 or less, and has a total content of sodium, calcium, and magnesium of 1000 parts by weight ppm. Hereinafter, a carboxyl group-containing nitrile rubber having a chloride ion content of 50 to 500 ppm by weight. The carboxyl group-containing nitrile rubber according to claim 1, which contains a carboxyl group-containing monomer unit in a proportion of 1 to 10% by weight. The carboxyl group-containing nitrile rubber according to claim 1 or 2, which contains an α, β-ethylenically unsaturated nitrile monomer unit in a proportion of 7 to 42% by weight. The carboxyl group-containing nitrile rubber according to any one of claims 1 to 3, which contains a conjugated diene monomer unit in a proportion of 10 to 66% by weight. The carboxyl group-containing nitrile rubber according to any one of claims 1 to 4, which contains an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit. A crosslinkable nitrile rubber composition containing the carboxyl group-containing nitrile rubber according to any one of claims 1 to 5 and a polyvalent amine compound. A rubber crosslinked product obtained by crosslinking the crosslinkable nitrile rubber composition according to claim 6. A seal made of a crosslinked rubber product according to claim 7. The method for producing a carboxyl group-containing nitrile rubber according to any one of claims 1 to 5.
A step of adding a coagulant to coagulate the latex of a carboxyl group-containing nitrile rubber is included.
A method for producing a carboxyl group-containing nitrile rubber using chloride or a chloride and a coagulant other than chloride as the coagulant. The method for producing a carboxyl group-containing nitrile rubber according to claim 9, wherein the amount of the coagulant used is 0.5 to 35 parts by weight with respect to 100 parts by weight of the carboxyl group-containing nitrile rubber contained in the latex.