JP6708316B2 - Acrylic rubber manufacturing method and acrylic rubber obtained by the manufacturing method - Google Patents

Description

The present invention relates to a method for producing an acrylic rubber, an acrylic rubber obtained by the production method, a rubber composition containing the same, and a rubber crosslinked product obtained by crosslinking the rubber composition, and more specifically, storage stability. The present invention relates to a method for producing an excellent acrylic rubber, an acrylic rubber obtained by the production method, a rubber composition containing the same, and a rubber crosslinked product obtained by crosslinking the rubber composition.

Acrylic rubber is a polymer containing acrylic acid ester as a main component, and is generally known as a rubber having excellent heat resistance, oil resistance and ozone resistance, and is widely used in fields related to automobiles.

Such an acrylic rubber is usually obtained by emulsion-polymerizing a monomer mixture constituting the acrylic rubber, adding a coagulant to the obtained emulsion-polymerized solution to coagulate, and drying the hydrous crumb obtained by coagulation. It is manufactured by doing (see, for example, Patent Document 1). From the viewpoint of productivity, a drying device such as a belt conveyor type band dryer or an extruder capable of drying in a continuous process is used for drying the water-containing crumb. On the other hand, the acrylic rubber produced in this manner has a problem that problems such as Mooney scorch and burns occur during long-term storage.

JP-A-7-145291

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for producing an acrylic rubber capable of realizing excellent storage stability while maintaining good normal physical properties.

The present inventors have conducted extensive studies to achieve the above object, and as a result, in the method for producing an acrylic rubber, two specific emulsifiers are combined for emulsion polymerization, and the resulting emulsion polymerization liquid is prepared by using a metal sulfate. It was found that by washing and drying the water-containing crumb obtained by coagulation, it is possible to produce an acrylic rubber capable of achieving excellent storage stability while maintaining good normal physical properties.

The present inventors have also found that the acrylic rubber has a crosslinkable functional group, uses a specific proportion of two emulsifiers and a redox polymerization catalyst as a polymerization initiator, and particularly combines two specific reducing agents. At least one mode of using a monovalent or divalent metal sulfate as a coagulant, and performing washing including acid washing by contacting the emulsion polymerization liquid with the metal sulfate while heating It was found that the object of the present invention can be achieved to a higher degree by adopting it, and the present invention has been completed.

Thus, according to the present invention, (meth)acrylic acid ester and at least one crosslinkable monomer selected from the group consisting of a carboxyl group-containing monomer, an epoxy group-containing monomer and a halogen group-containing monomer. An emulsion polymerization step in which a monomer containing and a nonionic emulsifier and an anionic emulsifier in the presence of a polymerization initiator are used for emulsion polymerization to obtain an emulsion polymerization solution, and the emulsion polymerization solution is contacted with a metal sulfate. Provided is a method for producing an acrylic rubber, comprising a coagulation step of coagulating to obtain a hydrous crumb, a washing step of washing the hydrous crumb, and a drying step of drying the washed hydrous crumb.
In the method for producing an acrylic rubber of the present invention, the use ratio of the nonionic emulsifier and the anionic emulsifier is preferably in the range of 1/99 to 99/1 in terms of the weight ratio of nonionic emulsifier/anionic emulsifier. ..
In the method for producing an acrylic rubber of the present invention, the use ratio of the nonionic emulsifier and the anionic emulsifier is in the range of 50/50 to 75/25 in terms of the weight ratio of nonionic emulsifier/anionic emulsifier. preferable.

In the method for producing an acrylic rubber of the present invention, it is preferable that the polymerization initiator is combined with a reducing agent.
In the method for producing an acrylic rubber of the present invention, it is preferable to use at least two compounds as the reducing agent.
In the method for producing an acrylic rubber of the present invention, it is preferable to use, as the reducing agent, a combination of a metal ion-containing compound in a reduced state and a reducing agent other than the metal ion-containing compound in the reduced state.
In the method for producing an acrylic rubber of the present invention, the metal ion-containing compound in the reduced state is preferably ferrous sulfate.
In the method for producing an acrylic rubber of the present invention, the reducing agent other than the metal ion-containing compound in the reduced state is preferably sodium formaldehyde sulfoxylate, ascorbic acid or ascorbate.
In the method for producing an acrylic rubber of the present invention, the reducing agent other than the metal ion-containing compound in the reduced state is preferably ascorbate.

In the method for producing an acrylic rubber of the present invention, the polymerization initiator is preferably an organic peroxide or an inorganic peroxide.
In the method for producing an acrylic rubber of the present invention, the emulsion polymerization liquid and the metal sulfate are contacted with each other, or the metal sulfate is added to the emulsion polymerization liquid, or the emulsion polymerization liquid is made of the metal sulfate of gold. It is preferable to carry out either method of adding the solution or dispersion.
In the method for producing an acrylic rubber of the present invention, the temperature at which the emulsion polymerization liquid and the metal sulfate are brought into contact with each other is preferably 60°C or higher.
In the method for producing an acrylic rubber of the present invention, it is preferable that the metal sulfate is a monovalent or divalent metal sulfuric acid solution.
In the method for producing an acrylic rubber of the present invention, the anionic emulsifier is preferably a phosphate ester salt.
In the method for producing an acrylic rubber of the present invention, it is preferable that the cleaning includes acid cleaning.

Further, according to the present invention, there is provided an acrylic rubber manufactured by the above manufacturing method.
In the acrylic rubber of the present invention, the monomer composition has a (meth)acrylic acid ester monomer unit of 50 to 99.9% by weight, a crosslinkable monomer unit of 0.01 to 20% by weight, and copolymerizable. Other monomer units are preferably 0 to 49.99% by weight.
In the acrylic rubber of the present invention, the Mooney viscosity (ML1+4, 100° C.) is preferably in the range of 10 to 150.

Further, according to the present invention, there is provided a rubber composition containing a rubber component containing the acrylic rubber and a crosslinking agent.
In the rubber composition of the present invention, the crosslinking agent is a polyvalent amine compound, a polyvalent epoxy compound, a polyvalent carboxylic acid, an organic carboxylic acid ammonium salt, an organic carboxylic acid metal salt, an isocyanuric acid compound, a triazine compound, and a metal. It is preferably at least one selected from the group consisting of soap/sulfur.
The rubber composition of the present invention preferably further comprises a crosslinking accelerator.
In the rubber composition of the present invention, the crosslinking accelerator is a guanidine-based crosslinking accelerator, a diazabicycloalkene-based crosslinking accelerator, an aliphatic secondary amine-based crosslinking accelerator, an aliphatic tertiary amine-based crosslinking accelerator and It is at least one selected from the group consisting of dithiocarbomate vulcanization accelerators.
The rubber composition of the present invention preferably further comprises a scorch inhibitor.
The rubber composition of the present invention preferably further contains an antioxidant.
The rubber composition of the present invention preferably further contains a filler.
Further, according to the present invention, a rubber cross-linked product obtained by cross-linking the above rubber composition is provided.

According to the present invention, it is possible to provide an acrylic rubber capable of achieving excellent storage stability while maintaining good normal physical properties, a rubber composition containing the acrylic rubber, and a rubber cross-linked product thereof.

[Production method]
The method for producing an acrylic rubber of the present invention is (meth)acrylic acid ester [meaning acrylic acid ester and/or methacrylic acid ester. Hereinafter, the same applies to methyl (meth)acrylate and the like. ] And a monomer containing at least one crosslinkable monomer selected from the group consisting of a carboxyl group-containing monomer, an epoxy group-containing monomer and a halogen group-containing monomer, and a nonionic emulsifier and an anion. Emulsion polymerization step using an initiator in the presence of a water-soluble emulsifier to obtain an emulsion polymerization solution, a coagulation step of contacting the emulsion polymerization solution with a metal sulfate to obtain a water-containing crumb, and a water-containing crumb. A washing step of performing washing on the other hand and a drying step of drying the washed hydrous crumb are provided.

<Monomer>
The monomer used in the emulsion polymerization step of the present invention is characterized by having a (meth)acrylic acid ester as a main component. The (meth)acrylic acid ester as the main component is not particularly limited, but examples thereof include (meth)acrylic acid alkyl ester and (meth)acrylic acid alkoxyalkyl ester.

As the (meth)acrylic acid alkyl ester, for example, an ester of an alkanol having 1 to 12 carbon atoms and (meth)acrylic acid is used, and an ester of an alkanol having 1 to 8 carbon atoms and (meth)acrylic acid is preferable. , And esters of (meth)acrylic acid with an alkanol having 2 to 6 carbon atoms are more preferable. Specifically, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate , N-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, and the like. Among these, ethyl (meth)acrylate and n-butyl (meth)acrylate are included. Ethyl acrylate and n-butyl acrylate are particularly preferable.

As the (meth)acrylic acid alkoxyalkyl ester, for example, an ester of an alkoxyalkyl alcohol having 2 to 12 carbon atoms and (meth)acrylic acid is preferable, and specifically, methoxymethyl (meth)acrylic acid, (meth) Ethoxymethyl acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, (meth)acrylic acid Examples thereof include 3-methoxypropyl and 4-methoxybutyl (meth)acrylate. Among these, 2-ethoxyethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate and the like are preferable, 2-ethoxyethyl acrylate and 2-methoxyethyl acrylate are more preferable, and 2-methoxyethyl acrylate is preferable. Is more preferable.

These (meth)acrylic acid esters can be used alone or in combination of two or more. The content of the (meth)acrylic acid ester in the monomer used for polymerization is preferably the main component in the monomer, and is usually 50 to 99.9% by weight, preferably 60 to 99.7% by weight. , And more preferably 70 to 99.5% by weight. If the content of (meth)acrylic acid ester is excessively low, the weather resistance, heat resistance, and oil resistance of the obtained rubber cross-linked product may decrease, while if it is excessively high, the obtained rubber cross-linked product may be reduced. The heat resistance may decrease. Further, as the (meth)acrylic acid ester, it is preferable to use one consisting of 30 to 100% by weight of (meth)acrylic acid alkyl ester and 70 to 0% by weight of (meth)acrylic acid alkoxyalkyl ester.

As the monomer used for polymerization in the emulsion polymerization step of the present invention, a crosslinkable monomer and another copolymerizable monomer can be contained in addition to the (meth)acrylic acid ester.

The crosslinkable monomer is not particularly limited, and examples thereof include a carboxyl group-containing monomer, an epoxy group-containing monomer, a halogen atom-containing monomer, and a diene monomer, and preferably a carboxyl group. It is a containing monomer, an epoxy group containing monomer, or a halogen atom containing monomer, more preferably a halogen atom containing monomer.

The carboxyl group-containing monomer is not particularly limited, but, for example, α,β-ethylenically unsaturated carboxylic acid can be preferably used. Examples of the α,β-ethylenically unsaturated carboxylic acid include α,β-ethylenically unsaturated monocarboxylic acid having 3 to 12 carbon atoms, α,β-ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms, Examples thereof include monoesters of an α,β-ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms and an alkanol having 1 to 8 carbon atoms. The use of α,β-ethylenically unsaturated carboxylic acid is preferable because the compression set resistance when the obtained acrylic rubber is a rubber crosslinked product can be further enhanced.

Examples of the α,β-ethylenically unsaturated monocarboxylic acid having 3 to 12 carbon atoms include acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid and cinnamic acid. Examples of the α,β-ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms include butenedioic acid such as fumaric acid and maleic acid, itaconic acid, citraconic acid, and chloromaleic acid. Examples of monoesters of α,β-ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms and alkanol having 1 to 8 carbon atoms include monomethyl fumarate, monoethyl fumarate, mono n-butyl fumarate, and maleic acid. Butenedioic acid mono-chain alkyl ester such as monomethyl, monoethyl maleate, mono-n-butyl maleate; monocyclopentyl fumarate, monocyclohexyl fumarate, monocyclohexenyl fumarate, monocyclopentyl maleate, monocyclohexyl maleate, maleic acid Butenedioic acid monoesters having an alicyclic structure such as monocyclohexenyl; itaconic acid monoesters such as monomethyl itaconate, monoethyl itaconate, mono-n-butyl itaconate and monocyclohexyl itaconate; and the like.

As the carboxyl group-containing monomer, α,β-ethylenically unsaturated carboxylic acid is preferable, and a monoester of α,β-ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms and alkanol having 1 to 8 carbon atoms is used. Are more preferable, and butenedionic acid mono-chain alkyl ester and butenedionic acid monoester having an alicyclic structure are particularly preferable. Specific preferred examples include mono-n-butyl fumarate, mono-n-butyl maleate, monocyclohexyl fumarate, monocyclohexyl maleate and the like, with mono-n-butyl fumarate being particularly preferred. Incidentally, among the above-mentioned monomers, the dicarboxylic acid includes those existing as an anhydride.

The epoxy group-containing monomer is not particularly limited, but examples thereof include epoxy group-containing (meth)acrylic acid ester such as glycidyl (meth)acrylate; epoxy group-containing styrene such as p-vinylbenzyl glycidyl ether; allyl. Glycidyl ether and vinyl glycidyl ether, 3,4-epoxy-1-pentene, 3,4-epoxy-1-butene, 4,5-epoxy-2-pentene, 4-vinylcyclohexyl glycidyl ether, cyclohexenyl methyl glycidyl ether, Epoxy group-containing ethers such as 3,4-epoxy-1-vinylcyclohexene and allylphenyl glycidyl ether; and the like.

The halogen atom-containing monomer is not particularly limited, and examples thereof include unsaturated alcohol ester of halogen-containing saturated carboxylic acid, (meth)acrylic acid haloalkyl ester, (meth)acrylic acid haloacyloxyalkyl ester, (meth) Examples thereof include acrylic acid (haloacetylcarbamoyloxy) alkyl ester, halogen-containing unsaturated ether, halogen-containing unsaturated ketone, halomethyl group-containing aromatic vinyl compound, halogen-containing unsaturated amide, and haloacetyl group-containing unsaturated monomer.

Examples of unsaturated alcohol esters of halogen-containing saturated carboxylic acids include vinyl chloroacetate, vinyl 2-chloropropionate, allyl chloroacetate and the like. Examples of the haloalkyl ester of (meth)acrylic acid include chloromethyl (meth)acrylate, 1-chloroethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 1,2-dichloroethyl (meth)acrylate, Examples include 2-chloropropyl (meth)acrylate, 3-chloropropyl (meth)acrylate, and 2,3-dichloropropyl (meth)acrylate. Examples of the haloacyloxyalkyl (meth)acrylate include 2-(chloroacetoxy)ethyl (meth)acrylate, 2-(chloroacetoxy)propyl (meth)acrylate, and 3-(chloroacetoxy)(meth)acrylate. ) Propyl, 3-(hydroxychloroacetoxy)propyl (meth)acrylate and the like. Examples of (meth)acrylic acid (haloacetylcarbamoyloxy)alkyl ester include 2-(chloroacetylcarbamoyloxy)ethyl (meth)acrylate and 3-(chloroacetylcarbamoyloxy)propyl (meth)acrylate. Be done. Examples of the halogen-containing unsaturated ether include chloromethyl vinyl ether, 2-chloroethyl vinyl ether, 3-chloropropyl vinyl ether, 2-chloroethyl allyl ether, 3-chloropropyl allyl ether and the like. Examples of halogen-containing unsaturated ketones include 2-chloroethyl vinyl ketone, 3-chloropropyl vinyl ketone, and 2-chloroethyl allyl ketone. Examples of the halomethyl group-containing aromatic vinyl compound include p-chloromethylstyrene, m-chloromethylstyrene, o-chloromethylstyrene, p-chloromethyl-α-methylstyrene and the like. Examples of the halogen-containing unsaturated amide include N-chloromethyl(meth)acrylamide. Examples of the haloacetyl group-containing unsaturated monomer include 3-(hydroxychloroacetoxy)propyl allyl ether and p-vinylbenzyl chloroacetic acid ester. Among these, unsaturated alcohol esters of halogen-containing saturated carboxylic acids are preferable, and vinyl chloroacetate (vinyl monochloroacetate) is more preferable.

These crosslinkable monomers can be used alone or in combination of two or more kinds. The content of the crosslinkable monomer in the monomer is usually 0.01 to 20% by weight, preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight. By setting the content of the crosslinkable monomer in the above range, it is possible to highly balance the mechanical properties and the compression set resistance when the obtained acrylic rubber is used as a crosslinked product.

The other copolymerizable monomer is not particularly limited as long as it is copolymerizable, and examples thereof include an aromatic vinyl monomer, an α,β-ethylenically unsaturated nitrile monomer, and an acrylamide monomer. Examples include monomers and other olefinic monomers. Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, divinylbenzene and the like. Examples of the α,β-ethylenically unsaturated nitrile monomer include acrylonitrile and methacrylonitrile. Examples of the acrylamide monomer include acrylamide and methacrylamide. Examples of other olefin-based monomers include ethylene, propylene, vinyl chloride, vinylidene chloride, vinyl acetate, ethyl vinyl ether, and butyl vinyl ether. Among these other copolymerizable monomers, styrene, acrylonitrile, methacrylonitrile, ethylene and vinyl acetate are preferable, and acrylonitrile, methacrylonitrile and ethylene are more preferable.

These other copolymerizable monomers may be used alone or in combination of two or more. The content of these other copolymerizable monomers in the monomer is usually 49.99% by weight or less, preferably 39.9% by weight or less, more preferably 29.5% by weight or less.

<Emulsion polymerization step>
In the emulsion polymerization step of the present invention, the above-mentioned (meth)acrylic acid ester-based monomer is emulsion-polymerized by using a polymerization initiator in the presence of a nonionic emulsifier and an anionic emulsifier to obtain an emulsion polymerization liquid. It is characterized by

The nonionic emulsifier is not particularly limited, and examples thereof include polyoxyalkylene alkyl ethers such as polyoxyethylene dodecyl ether; polyoxyalkylene alkyl phenyl ethers such as polyoxyethylene nonylphenyl ether; and polyoxyethylene stearic acid ester. Oxyalkylene fatty acid ester; polyoxyethylene sorbitan alkyl ester; polyoxyethylene/polyoxypropylene copolymer; and the like. Among these, polyoxyalkylene alkyl ethers, polyoxyalkylene alkylphenyl ethers, polyoxyethylene/polyoxypropylene copolymers and the like are preferable, and particularly polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene/polyoxyethylene/polyoxyethylene Oxypropylene copolymers are preferred. The weight average molecular weight of the nonionic emulsifier is not particularly limited, but is usually 300 to 50,000, preferably 500 to 30,000, more preferably 1,000 to 15,000. These nonionic emulsifiers can be used alone or in combination of two or more kinds.

The anionic emulsifier is not particularly limited, and examples thereof include salts of fatty acids such as myristic acid, palmitic acid, oleic acid, and linolenic acid; alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate; higher alcohols such as sodium lauryl sulfate. Examples thereof include phosphoric acid ester salts such as sulfuric acid ester salts and sodium alkyl phosphoric acid esters, preferably higher alcohol phosphoric acid ester salts such as sodium phosphoric acid ester salts of alcohols having a hydrophobic group with 6 or more carbon atoms; alkyl sulfosuccinate salts, and the like. it can. Among these anionic emulsifiers, phosphate ester salts and higher alcohol sulfate ester salts are preferred, higher alcohol phosphate ester salts and higher alcohol sulfate ester salts are more preferred, and higher alcohol phosphate ester salts are even more preferred. These anionic emulsifiers can be used alone or in combination of two or more.

The nonionic emulsifier and the anionic emulsifier are used in a weight ratio of nonionic emulsifier/anionic emulsifier, usually 1/99 to 99/1, preferably 10/90 to 80/20, more preferably 25/75. To 75/25, more preferably 50/50 to 75/25, and most preferably 65/35 to 75/25. By setting the ratio of the nonionic emulsifier to the anionic emulsifier within this range, it is possible to suppress the generation of stains due to the adhesion of the polymer or the like to the polymerization apparatus (for example, the polymerization tank) during the emulsion polymerization, and the metal as the coagulant. It is possible to reduce the amount of sulfate used, and as a result, it is possible to reduce the amount of coagulant in the finally obtained acrylic rubber, and thus to improve the water resistance of the rubber cross-linked product obtained. it can. Further, by setting the ratio of the nonionic emulsifier to the anionic emulsifier within this range, the emulsifying action can be enhanced, so that the amount of the emulsifier itself used can be reduced, and as a result, finally obtained. It is possible to reduce the residual amount of the emulsifier contained in the acrylic rubber, which makes it possible to further enhance the water resistance of the resulting acrylic rubber, which is preferable.

The amount of the emulsifier used is usually 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, more preferably 1 to 3 parts by weight, based on 100 parts by weight of the monomer used for the polymerization. The range is.

In the present invention, other emulsifiers can be used as the emulsifier, if necessary. Other emulsifiers include, for example, cationic emulsifiers, and specific examples thereof include alkyltrimethylammonium chloride, dialkylammonium chloride, benzylammonium chloride and the like. These other emulsifiers can be used alone or in combination of two or more, and the amount used is appropriately selected within the range not impairing the object of the present invention.

As the polymerization initiator, azo compounds such as azobisisobutyronitrile; organic peroxides such as diisopropylbenzene hydroperoxide, cumene hydroperoxide, paramenthane hydroperoxide, benzoyl peroxide; sodium persulfate, persulfate Inorganic peroxides such as potassium, hydrogen peroxide and ammonium persulfate; and the like can be used. These polymerization initiators can be used alone or in combination of two or more kinds. The amount of the polymerization initiator used is preferably 0.001 to 1.0 part by weight with respect to 100 parts by weight of the monomer used for the polymerization.

When an organic peroxide and/or an inorganic peroxide is used as the polymerization initiator, it is preferably used as a redox polymerization initiator in combination with a reducing agent. The reducing agent to be combined is not particularly limited, but for example, ferrous sulfate, sodium hexamethylenediaminetetraacetate, cuprous naphthenate and the like metal ion-containing compounds in a reduced state; ascorbic acid, sodium ascorbate, ascorbine Ascorbic acid (salt) such as potassium acidate; Erythorbic acid (salt) such as erythorbic acid, sodium erysorbate, and potassium erysorbate; Saccharide; Sulfinate salt such as sodium hydroxymethanesulfinate; Sodium sulfite, potassium sulfite, sodium hydrogen sulfite , Aldehyde sodium bisulfite, potassium bisulfite sulfite; sodium pyrosulfite, potassium pyrosulfite, sodium pyrobisulfite, potassium pyrosulfite, etc. pyrosulfite; sodium thiosulfate, potassium thiosulfate, etc. thiosulfate; Phosphorous acid, sodium phosphite, potassium phosphite, sodium hydrogen phosphite, potassium phosphite (phosphorous acid) (salt); pyrophosphorous acid, sodium pyrophosphite, potassium pyrophosphite, sodium pyrophosphite, hydrogen pyrophosphite Pyrophosphorous acid (salt) such as potassium; sodium formaldehyde sulfoxylate and the like can be mentioned.

These reducing agents can be used alone or in combination of two or more, but it is preferable to use two or more kinds in combination, and more preferably, a metal ion-containing metal in a reduced state as the first reducing agent. Combining a compound with a reducing agent other than a metal ion-containing compound in a reduced state as a second reducing agent, and more preferably combining ferrous sulfate with ascorbic acid (salt) and/or sodium formaldehyde sulfoxylate That is, particularly preferably, the combination of ferrous sulfate and ascorbate is preferable because the object of the present application can be achieved to a higher degree. The amount of the reducing agent used is preferably in the range of 0.0001 to 0.5 part by weight, based on 100 parts by weight of the monomer used for the polymerization.

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

At the time of emulsion polymerization, a polymerization auxiliary material such as a molecular weight adjusting agent, a particle size adjusting agent, a chelating agent and an oxygen scavenger can be used, if necessary.

The emulsion polymerization may be carried out by any of batch method, semi-batch method and continuous method, but the semi-batch method is preferred. Specifically, in a reaction system containing a polymerization initiator and a reducing agent, a monomer used for the polymerization is continuously dropped into the polymerization reaction system from the start of the polymerization reaction to an arbitrary time, and the polymerization reaction is performed. At least one of the monomers used for the polymerization, the polymerization initiator, and the reducing agent is preferably subjected to the polymerization reaction while being continuously added dropwise to the polymerization reaction system from the initiation of the polymerization reaction to an arbitrary time, It is more preferable to carry out the polymerization reaction while continuously dropping all of the monomers, the polymerization initiator and the reducing agent used for the polymerization from the start of the polymerization reaction to an arbitrary time. By carrying out the polymerization reaction while continuously dropping these, emulsion polymerization can be stably carried out, whereby the polymerization reaction rate can be improved. The polymerization is usually carried out in the temperature range of 0 to 70°C, preferably 5 to 50°C.

Further, when carrying out the polymerization reaction while continuously dropping the monomer used for the polymerization, the monomer used for the polymerization is mixed with an emulsifier and water to obtain a monomer emulsion (emulsion preparation). Step), it is preferable to continuously drop the monomer emulsion. The method for preparing the monomer emulsion is not particularly limited, and a method in which the total amount of the monomers used in the polymerization, the total amount of the emulsifier, and water are stirred using a stirrer such as a homomixer or a disk turbine can be used. Can be mentioned. The amount of water used in the monomer emulsion is preferably 10 to 70 parts by weight, more preferably 20 to 50 parts by weight, based on 100 parts by weight of the monomer used for the polymerization.

When the polymerization reaction is continuously carried out while continuously dropping into the polymerization reaction system from the initiation of the polymerization reaction to an arbitrary time for all of the monomers used for the polymerization, the polymerization initiator, and the reducing agent, these are separated from each other. May be added dropwise to the polymerization system by using the dropping device, or at least the polymerization initiator and the reducing agent are mixed in advance and, if necessary, added to the polymerization system from the same dropping device as an aqueous solution state. May be. After completion of the dropping, the reaction may be continued for an arbitrary time in order to further improve the polymerization reaction rate.

The termination of emulsion polymerization can be performed by adding a polymerization terminator, if necessary. Examples of the polymerization terminator include hydroxylamine, hydroxyamine sulfate, diethylhydroxyamine, hydroxyaminesulfonic acid and its alkali metal salts, sodium dimethyldithiocarbamate, hydroquinone and the like. The amount of the polymerization terminator used is not particularly limited, but is preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of the monomer used for the polymerization.

<Addition of compounding agent to emulsion polymerization liquid>
In the emulsion polymerization step of the present invention, various compounding agents can be added to the emulsion polymerization liquid before solidification, which is obtained by emulsion polymerization, if necessary, and uniformly dispersed in the produced acrylic rubber polymer. The compounding agent to be added is not particularly limited as long as it is a compounding agent for rubber, but, for example, an antioxidant, a lubricant, an alkylene oxide polymer, etc. can be effectively compounded and suitable.

For example, by preliminarily containing an antioxidant in the emulsion polymerization liquid before coagulation, it is possible to effectively suppress the deterioration of the acrylic rubber due to the heat during drying in the drying step described later. Specifically, it is possible to effectively suppress a decrease in Mooney viscosity due to deterioration due to heating during drying, and thus, in the case of a rubber crosslinked product, effective tensile strength and elongation at break etc. It can be raised to. In addition, in the state of the emulsion polymerization liquid before performing the coagulation, by adding an antioxidant, since it is possible to appropriately disperse the antioxidant, even when the amount of the antioxidant is reduced, The effect of addition can be sufficiently exhibited. Specifically, the amount of the antioxidant added is preferably 0.1 to 2 parts by weight, more preferably 0.2 to 1.2 parts by weight, based on 100 parts by weight of the acrylic rubber component in the emulsion polymerization liquid. Even with a relatively small blending amount, the effect of addition can be sufficiently exhibited. Incidentally, even when the anti-aging agent is contained in the emulsion polymerization liquid before coagulation, in the subsequent coagulation and washing, drying, etc., the added anti-aging agent is not substantially removed. The addition effect can be sufficiently exhibited. Further, as a method of containing an anti-aging agent in the emulsion polymerization liquid, after the emulsion polymerization, and a method of adding to the emulsion polymerization liquid before performing the coagulation, or a method of adding to the solution before performing the emulsion polymerization However, when added to the solution before carrying out the emulsion polymerization, aggregates are generated during the emulsion polymerization, which may cause fouling of the polymerization apparatus. In addition, the method of adding to the emulsion polymerization liquid before coagulation is more preferable.

The antiaging agent is not particularly limited, and examples thereof include 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butylphenol, butylhydroxyanisole and 2,6-di-t-. Butyl-α-dimethylamino-p-cresol, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, mono(or di or tri)(α-methylbenzyl)phenol, etc. Styrenated phenol, 2,2'-methylene-bis(6-α-methylbenzyl-p-cresol), 4,4'-methylenebis(2,6-di-t-butylfunol), 2,2'-methylene- Butylation reaction of bis(4-methyl-6-t-butylphenol), stearyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, alkylated bisphenol, p-cresol and dicyclopentadiene Phenol-based antioxidants containing no sulfur atom such as products; 2,4-bis[(octylthio)methyl]-6-methylphenol, 2,2'-thiobis-(4-methyl-6-t-butylphenol) , 4,4'-thiobis-(6-t-butyl-o-cresol), 2,6-di-t-butyl-4-(4,6-bis(octylthio)-1,3,5-triazine- 2-ylamino)phenol and other thiophenol antioxidants; tris(nonylphenyl)phosphite, diphenylisodecyl phosphite, tetraphenyldipropylene glycol diphosphite and other phosphite antioxidants; dilauryl thiodipropionate Sulfur ester-based antioxidants such as phenyl-α-naphthylamine, phenyl-β-naphthylamine, p-(p-toluenesulfonylamide)-diphenylamine, 4,4′-(α,α-dimethylbenzyl)diphenylamine, N, N-diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, butyraldehyde-aniline condensate, and other amine-based antioxidants; 2-mercaptobenzimidazole and other imidazole-based antioxidants; A quinoline antiaging agent such as 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; a hydroquinone antiaging agent such as 2,5-di-(t-amyl)hydroquinone; and the like. . These anti-aging agents can be used alone or in combination of two or more kinds.

The lubricant is not particularly limited, and examples thereof include hydrocarbon lubricants such as liquid paraffin, paraffin wax, and synthetic polyethylene wax; fatty acid ester lubricants such as stearic acid alkyl ester; theearic acid amide, oleic acid amide, and erucic acid amide. Fatty acid amide lubricants such as; Metal soap lubricants such as calcium stearate, magnesium stearate, zinc stearate; Polyoxyethylene stearyl ether phosphoric acid, polyoxyethylene lauryl ether phosphoric acid, polyoxyethylene oleyl ether phosphoric acid, polyoxy And phosphoric acid ester-based lubricants such as polyoxyethylene higher alcohol phosphoric acid such as ethylene tridecyl ether phosphoric acid; higher fatty acid-based lubricants such as fatty acids having 10 to 30 carbon atoms, preferably 12 to 20 carbon atoms; and the like.

Among these, fatty acid ester-based, fatty acid amide-based, phosphoric acid ester-based, and higher fatty acid-based lubricants, preferably phosphoric acid ester-based lubricants and higher fatty acid-based lubricants, and more preferably when polyoxyethylene stearyl ether phosphoric acid is used. The acrylic rubber produced is highly suitable because it is highly improved in handleability and roll processability during drying.

These lubricants can be used alone or in combination of two or more, and the addition amount thereof is appropriately selected according to the purpose of use, but 100 parts by weight of the acrylic rubber component contained in the emulsion polymerization liquid is added. On the other hand, it is usually in the range of 0.0001 to 10 parts by weight, preferably 0.001 to 5 parts by weight, and more preferably 0.01 to 1 part by weight.

By preliminarily containing the lubricant in the emulsion polymerization liquid before the coagulation, the lubricant can be well dispersed in the emulsion polymerization liquid before the coagulation, whereby the acrylic rubber after the coagulation can be obtained. The lubricant can be contained therein in a well-dispersed state. Then, as a result, the obtained acrylic rubber can appropriately contain a lubricant (preferably, it can be contained in a state of being uniformly dispersed), whereby the obtained acrylic rubber is It can be made excellent in handleability during drying and roll processability. Even when the lubricant is contained in the emulsion polymerization liquid before coagulation, the lubricant added in the subsequent coagulation, washing, and drying is not substantially removed, so that the effect of the addition is obtained. It can be fully demonstrated. On the other hand, when the lubricant is added after the solidification, it becomes difficult to disperse the lubricant in the acrylic rubber, and therefore, the lubricant cannot be contained in the acrylic rubber (particularly, it was uniformly dispersed). However, it is difficult to obtain the effect of adding a lubricant, for example, the effect of suppressing the adhesion during drying during the production of acrylic rubber.

The alkylene oxide polymer is not particularly limited as long as it is an alkylene oxide polymer, but a lower alkylene oxide polymer is usually used. Specific examples include polyethylene oxide, polypropylene oxide, and ethylene oxide/propylene oxide copolymers, and among these, polyethylene oxide is preferable. The weight average molecular weight of the alkylene oxide polymer is selected according to the purpose of use, but is usually 10,000 to 6,000,000, preferably 30,000 to 1,000,000, and more preferably 50,000. ˜500,000, particularly preferably 50,000 to 300,000, most preferably 80,000 to 200,000. When the weight average molecular weight of the alkylene oxide polymer is in this range, the object of the present invention can be achieved to a high degree, which is preferable.

These alkylene oxide-based polymers can be used alone or in combination of two or more, and the blending amount is preferably 0.01 part with respect to 100 parts by weight of the acrylic rubber component in the emulsion polymerization liquid. To 1 part by weight, more preferably 0.01 to 0.6 part by weight, still more preferably 0.02 to 0.5 part by weight. By previously containing the alkylene oxide polymer in the emulsion polymerization liquid before solidification, it is possible to improve the solidification property of the emulsion polymerization liquid, thereby reducing the amount of the coagulant in the solidification step. This is preferable because the residual amount in the finally obtained acrylic rubber can be reduced and the compression set resistance and water resistance in the case of a rubber crosslinked product can be improved.

<Coagulation process>
The coagulation step of the present invention is characterized in that the above-mentioned, if necessary, an emulsion polymerization solution to which an antioxidant, a lubricant and/or an alkylene oxide polymer is added is contacted with a metal sulfate to coagulate to obtain a hydrous crumb. To do.

The metal sulfate used as the coagulant is not particularly limited, but for example, a sulfate salt of a monovalent to trivalent metal can be preferably used, and a sulfate salt of a monovalent or divalent metal is more preferable. Specifically, sodium sulfate, potassium sulfate, lithium sulfate, magnesium sulfate, calcium sulfate, zinc sulfate, titanium sulfate, manganese sulfate, iron sulfate, cobalt sulfate, nickel sulfate, aluminum sulfate, tin sulfate and the like, Preferred are sodium sulfate, magnesium sulfate and aluminum sulfate, and more preferred are sodium sulfate and magnesium sulfate.

These metal sulfates may be used alone or in combination of two or more. The amount of the metal sulfate used is usually 0.01 to 100 parts by weight, preferably 0.1 to 50 parts by weight, more preferably 1 to 30 parts by weight, based on 100 parts by weight of the acrylic rubber component in the emulsion polymerization liquid. The range is. When the metal sulfate is in this range, the compression set resistance, water resistance and storage stability when acrylic rubber is crosslinked can be highly balanced while the acrylic rubber is sufficiently solidified. Is.

In the coagulation step of the present invention, other coagulant may be used in combination with the metal sulfate as required. Examples of other coagulants include metals such as sodium chloride, potassium chloride, lithium chloride, magnesium chloride, calcium chloride, zinc chloride, titanium chloride, manganese chloride, iron chloride, cobalt chloride, nickel chloride, aluminum chloride and tin chloride. Chlorides; metal nitrates such as sodium nitrate, potassium nitrate, lithium nitrate, magnesium nitrate, calcium nitrate, zinc nitrate, titanium nitrate, manganese nitrate, iron nitrate, cobalt nitrate, nickel nitrate, aluminum nitrate and tin nitrate; and the like. These other coagulants can be used alone or in combination of two or more, and the blending amount thereof is appropriately selected within a range not impairing the object of the present invention.

The method of contacting the emulsion polymerization liquid and the metal sulfate may be according to a conventional method, such as adding a metal sulfate or a solution or dispersion of the metal sulfate to the emulsion polymerization liquid, or the emulsion polymerization liquid of the metal sulfate. It can be performed by adding it to a solution or a dispersion. An aqueous solution is usually used as the solution or dispersion of the metal sulfate when the emulsion polymerization liquid is added, and the concentration of the metal sulfate in the aqueous solution is appropriately selected according to the purpose of use, and is usually 1 to 50% by weight. , Preferably 5 to 40% by weight, more preferably 10 to 30% by weight.

The contact (coagulation) temperature of the emulsion polymerization liquid and the metal sulfate is not particularly limited, but is usually 60° C. or higher, preferably 65 to 100° C., more preferably 70 to 95° C., further preferably 78 to 95°C, most preferably 83-95°C.

<Washing process>
The washing step of the present invention is to wash the hydrous crumb obtained in the coagulation step.

The washing method is not particularly limited, but a method in which water is used as a washing liquid and the added water is mixed with the water-containing crumb to perform washing with water can be mentioned. The temperature at the time of washing with water is not particularly limited, but is preferably 5 to 60°C, more preferably 10 to 50°C, and the mixing time is 1 to 60 minutes, more preferably 2 to 30 minutes.

Further, at the time of washing with water, the amount of water added to the hydrous crumb is not particularly limited, but from the viewpoint that the residual amount of the coagulant in the finally obtained acrylic rubber can be effectively reduced, The amount of water per wash is preferably 50 to 9,800 parts by weight, more preferably 300 to 1,800, relative to 100 parts by weight of the solid content (mainly the acrylic rubber component) contained in the water-containing crumb. Parts by weight.

The number of times of washing with water is not particularly limited, and may be once, but from the viewpoint of reducing the residual amount of the coagulant in the finally obtained acrylic rubber, it is preferably performed plural times, preferably 2 to 10 times. , More preferably 3 to 8 times. From the viewpoint of reducing the residual amount of the coagulant in the finally obtained acrylic rubber, it is desirable that the number of times of washing with water is large, but even if the washing is performed beyond the above range, the effect of removing the coagulant is still high. On the other hand, although the number of steps is small, the number of steps is increased, and the decrease in productivity is greatly affected.

Moreover, in the present invention, after washing with water, acid washing using an acid as a washing liquid may be further performed. By carrying out acid washing, the storage stability of the acrylic rubber can be highly enhanced, and the compression set resistance in the case of forming a rubber cross-linked product can be enhanced, which is preferable.

The acid used for acid washing is not particularly limited, and sulfuric acid, hydrochloric acid, phosphoric acid, etc. can be used without limitation. In addition, in the acid washing, when the acid is added to the hydrous crumb, it is preferably added in the state of an aqueous solution, preferably pH=6 or less, more preferably pH=5 or less, further preferably pH=4 or less. It is preferable to add it in the form of an aqueous solution. Further, the method of acid washing is not particularly limited, and examples thereof include a method of mixing an aqueous solution of the added acid with the hydrous crumb.

The temperature at the time of acid washing is not particularly limited, but is preferably 5 to 60°C, more preferably 10 to 50°C, and the mixing time is 1 to 60 minutes, more preferably 2 to 30 minutes. The pH of the washing water for acid washing is not particularly limited, but is preferably pH=6 or less, more preferably pH=5 or less, still more preferably pH=4 or less. The pH of the cleaning water for acid cleaning can be determined by, for example, measuring the pH of water contained in the hydrous crumb after acid cleaning.

It is preferable to further wash with water after performing the acid washing, and the conditions of washing with water may be the same as the above-mentioned conditions.

<Drying process>
In the drying step of the present invention, the water-containing crumbs washed in the washing step are dried.

The drying method in the drying step is not particularly limited, but for example, it can be dried using a dryer such as a screw type extruder, a kneader type dryer, an expander dryer, a hot air dryer or a reduced pressure dryer. .. Moreover, you may use the drying method which combined these. Further, if necessary, the water-containing crumb may be filtered using a sieve such as a rotary screen or a vibrating screen; a centrifugal dehydrator;

For example, the drying temperature in the drying step is not particularly limited and varies depending on the dryer used for drying. For example, when a hot air dryer is used, the drying temperature is preferably 80 to 200° C., and 100 It is more preferable to set the temperature to ˜170° C.

[Acrylic rubber]
According to the present invention, the acrylic rubber of the present invention can be obtained by the above manufacturing method. The acrylic rubber of the present invention thus obtained has excellent storage stability while maintaining good normal physical properties.

The acrylic rubber of the present invention is not particularly limited except that it contains a (meth)acrylic acid ester monomer unit as a main component, but when it further contains a crosslinkable monomer unit, the effect of the present invention is highly enhanced. It is preferable.

The monomer composition in the acrylic rubber of the present invention is appropriately selected according to the purpose of use, but the (meth)acrylic acid ester monomer unit is usually 50 to 99.9% by weight, preferably 60 to 99. 0.7 wt%, more preferably 70 to 99.5 wt%, the content of the crosslinkable monomer unit is usually 0.01 to 20 wt%, preferably 0.1 to 10 wt%, more preferably Is 0.5 to 5% by weight, and the content of the other copolymerizable monomer unit is usually 0 to 49.99% by weight, preferably 0 to 39.9% by weight, and more preferably 0. ˜29.5% by weight. Examples of the (meth)acrylic acid ester monomer, the crosslinkable monomer, and the other copolymerizable monomer are the same as those exemplified in the above <monomer>. Examples of the crosslinkable monomer unit include a carboxyl group-containing monomer unit, a halogen group-containing monomer unit, an epoxy group-containing monomer unit, and the like, and a halogen group-containing monomer unit is preferable.

The Mooney viscosity (ML1+4, 100° C.) of the acrylic rubber of the present invention is selected according to the purpose of use, but is usually 10 to 150, preferably 20 to 100, more preferably 25 to 60.

The glass transition temperature (Tg) of the acrylic rubber of the present invention is selected according to the purpose of use, but is usually 15°C or lower, preferably 0°C or lower.

Then, according to the present invention, there is provided a method for producing such an acrylic rubber, and an acrylic rubber obtained by the production method.
In particular, the acrylic rubber of the present invention obtained by the above-mentioned production method has excellent storage stability while maintaining good normal physical properties. Here, in the field of rubber such as acrylic rubber, it is usual to coagulate when a solid rubber is obtained from a solution or dispersion of the rubber obtained by polymerization, and according to the findings of the present inventors. Then, the characteristics of the obtained acrylic rubber greatly change depending on the state of solidification.

On the other hand, the acrylic rubber of the present invention performs such coagulation by using a metal sulfate as a coagulant. Further, since emulsion polymerization is carried out in the presence of a nonionic emulsifier and an anionic emulsifier, the nonionic emulsifier and the anionic emulsifier are also contained during coagulation. Here, the acrylic rubber obtained by such coagulation contains a metal sulfate, a nonionic emulsifier and an anionic emulsifier as a coagulant, but according to the findings of the present inventors, the acrylic rubber is , Simply by containing a metal sulfate, a nonionic emulsifier and an anionic emulsifier, while maintaining the normal state physical properties, the effect of being able to improve the storage stability is not exhibited, emulsion polymerization It has been found that it is necessary to use a nonionic emulsifier and an anionic emulsifier at the same time, and a metal sulfate as a coagulant at the time of coagulation. Then, the acrylic rubber of the present invention is obtained only through such a step, and can be unconditionally specified by the wording such as simply containing a metal sulfate, a nonionic emulsifier and an anionic emulsifier. It cannot be done.

Further, if the acrylic rubber of the present invention, the internal state and the like, even if analyzed by various analyzers, both acrylic rubber, anionic emulsifier and nonionic emulsifier, carbon atoms and oxygen atoms as the main component However, it is extremely difficult to specify the dispersed state and the like, and therefore, it can be said that there is sufficient rationality to specify the acrylic rubber of the present invention by the manufacturing method.

[Rubber composition]
The rubber composition of the present invention is characterized by containing a rubber component containing the above acrylic rubber and a crosslinking agent. The content of the acrylic rubber of the present invention in the rubber component may be selected according to the purpose of use, and is typically 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more. And particularly preferably 100% by weight.

As the rubber component, the acrylic rubber may be used alone or in combination with the acrylic rubber and other rubbers.
As other rubber, acrylic rubber other than the acrylic rubber of the present invention, natural rubber, polybutadiene rubber, polyisoprene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, silicone rubber, fluororubber, olefin elastomer, styrene elastomer, Examples thereof include vinyl chloride elastomers, polyester elastomers, polyamide elastomers, polyurethane elastomers and polysiloxane elastomers.

These other rubbers may be used alone or in combination of two or more. The content of the other rubber in the rubber component is appropriately selected within a range that does not impair the effects of the present invention, and is usually 70% by weight or less, preferably 50% by weight or less, more preferably 30% by weight or less.

The cross-linking agent used in the rubber composition of the present invention is not particularly limited, and examples thereof include diamine compounds, polyvalent amine compounds such as dithiocarbamic acid, and carbonates thereof; sulfur compounds; sulfur donors; polyvalent epoxies. A conventionally known cross-linking agent such as a compound; an organic carboxylic acid ammonium salt; a polyvalent carboxylic acid; an isocyanuric acid compound; an organic peroxide; a triazine compound; Among these, polyvalent amine compounds and triazine compounds are preferable, and triazine compounds are particularly preferable.

Examples of the polyvalent amine compound include aliphatic polyvalent amine compounds such as hexamethylenediamine, hexamethylenediamine carbamate, and N,N′-dicinnamylidene-1,6-hexanediamine; 4,4′-methylenedianiline, p -Phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-(m-phenylenediisopropylidene)dianiline, 4,4'-(p-phenylenediamine) Isopropylidene)dianiline, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminobenzanilide, 4,4'-bis(4-aminophenoxy)biphenyl, m-xylyl Aromatic polyvalent amine compounds such as diamine, p-xylylenediamine and 1,3,5-benzenetriamine; and the like. Among these, hexamethylenediamine carbamate and 2,2'-bis[4-(4-aminophenoxy)phenyl]propane are preferable. These polyvalent amine compounds are particularly preferably used in combination with a carboxyl group-containing acrylic rubber (acrylic rubber containing a carboxyl group-containing monomer unit as a crosslinkable monomer unit).

Examples of the triazine compound include 6-trimercapto-s-triazine, 2-anilino-4,6-dithiol-s-triazine, 1-dibutylamino-3,5-dimercaptotriazine, 2-dibutylamino-4, 6-dithiol-s-triazine, 1-phenylamino-3,5-dimercaptotriazine, 2,4,6-trimercapto-1,3,5-triazine, 1-hexylamino-3,5-dimercaptotriazine And so on. These triazine compounds are particularly preferably used in combination with an acrylic rubber containing a halogen group (an acrylic rubber containing a halogen group-containing monomer unit as a crosslinkable monomer unit).

Examples of the organic carboxylic acid ammonium salt include ammonium benzoate and ammonium adipate; examples of the dithiocarbamic acid compound include dimethyldithiocarbamic acid and zinc dimethyldithiocarbamate; examples of the polyvalent carboxylic acid include tetradecanenic acid and isocyanuric acid. Examples of the compound include isocyanuric acid and ammonium isocyanurate: Among these, ammonium benzoate, dimethyldithiocarbamic acid, and isocyanuric acid are particularly preferable in combination with an epoxy group-containing acrylic rubber (acrylic rubber containing an epoxy group-containing monomer unit as a crosslinkable monomer unit). Used for.

These cross-linking agents may be used alone or in combination of two or more, and the compounding amount thereof is usually 0.001 to 20 parts by weight, preferably 0.1 to 20 parts by weight with respect to 100 parts by weight of the rubber component. 10 parts by weight, more preferably 0.1 to 5 parts by weight. By setting the amount of the cross-linking agent to be within this range, it is preferable that the rubber elasticity is sufficient and the mechanical strength of the cross-linked rubber is excellent.

The rubber composition of the present invention is suitable for further improving the effect of the present invention by further adding a crosslinking accelerator. The crosslinking accelerator is not particularly limited, and examples thereof include guanidine-based crosslinking accelerator, diazabicycloalkene-based crosslinking accelerator, aliphatic secondary amine-based crosslinking accelerator, aliphatic tertiary amine-based crosslinking accelerator, dithiocarbamic acid. Suitable examples include salt vulcanization accelerators. Among these, guanidine-based crosslinking accelerators and dithiocarbamate-based crosslinking accelerators are particularly preferable, and dithiocarbamate-based crosslinking accelerators are more preferable.

Specific examples of the guanidine-based vulcanization accelerator include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, and dicatecholborate di-o-tolylguanidine. Examples include salts, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, and 1,3-diphenylguanidine. 1,3-Di-o-tolylguanidine and 1-o-tolylbiguanide are preferred because of their high reactivity, and 1,3-diphenylguanidine (DPG) is particularly preferred because of its higher reactivity.

Specific examples of the diazabicycloalkene vulcanization accelerator include 1,8-diazabicyclo[5.4.0]unde-7-cene and 1,5-diazabicyclo[4.3.0]no-5-nene. And so on.

Examples of the aliphatic secondary amine vulcanization accelerator include dimethylamine, diethylamine, dipropylamine, diallylamine, diisopropylamine, di-n-butylamine, di-t-butylamine, di-sec-butylamine, dihexylamine, Examples include diheptylamine, dioctylamine, dinonylamine, didecylamine, diundecylamine, didodecylamine, ditridecylamine, ditetradecylamine, dipentadecylamine, dicetylamine, di-2-ethylhexylamine and dioctadecylamine. it can.

Examples of the aliphatic tertiary amine-based vulcanization accelerator include trimethylamine, triethylamine, tripropylamine, triallylamine, triisopropylamine, tri-n-butylamine, tri-t-butylamine, tri-sec-butylamine, trihexyl. Examples thereof include amine, triheptylamine, trioctylamine, trinonylamine, tridecylamine, triundecylamine and tridodecylamine.

Specific examples of the dithiocarbamate vulcanization accelerator include zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc dipentyldithiocarbamate, zinc dihexyldithiocarbamate, zinc N-pentamethylenedithiocarbamate, N-ethyl. Zinc-N-phenyldithiocarbamate, zinc dibenzyldithiocarbamate, copper dipropyldithiocarbamate, copper diisopropyldithiocarbamate, copper dibutyldithiocarbamate, sodium diethyldithiocarbamate, sodium diisopropyldithiocarbamate, sodium dibutyldithiocarbamate, dimethyldithiocarbamate secondary Examples thereof include iron and ferric diethyldithiocarbamate. Of these, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, zinc dibenzyldithiocarbamate, and zinc N-ethyl-N-phenyldithiocarbamate are preferable.

As the crosslinking accelerator used in the present invention, other crosslinking accelerators other than the above may be used. Other crosslinking accelerators include, for example, N-cyclohexyl-2-benzothiazylsulfenamide, N-tert-butyl-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N.V. N-diisopropyl-2-benzothiazole sulfenamide and other sulfenamide vulcanization accelerators; diethylthiourea and other thiourea vulcanization accelerators; 2-mercaptobenzothiazole, dibenzothiazyl disulfide, 2-mercaptobenzothiazole zinc Thiazole vulcanization accelerators such as salts; Xanthogenic acid vulcanization accelerators such as sodium isopropylxanthate, zinc isopropylxanthate, zinc butylxanthate; Thiuram vulcanizations such as tetramethylthiuram monosulfide and tetramethylthiuram disulfide Accelerators; imidazole-based vulcanization accelerators such as 2-methylimidazole and 2-phenylimidazole; quaternary onium salt-based vulcanization accelerators such as tetra-n-butylammonium bromide, octadecyltri-n-butylammonium bromide; triphenyl Examples thereof include tertiary phosphine-based vulcanization accelerators such as phosphine and tri-p-tolylphosphine.

These cross-linking accelerators can be used alone or in combination of two or more, and the compounding amount thereof is usually 0.01 to 20 parts by weight, preferably 0.1 part by weight with respect to 100 parts by weight of the rubber component. It is 1 to 10 parts by weight, more preferably 1 to 5 parts by weight. When the content of the crosslinking accelerator is within this range, the obtained rubber crosslinked product can further improve the tensile strength and compression set resistance, which is preferable.

It is preferable that the rubber composition of the present invention further comprises a scorch inhibitor so that the rubber composition has good cross-linking physical properties. The scorch inhibitor is not particularly limited, and examples thereof include imide compounds such as N-cyclohexylthiophthalimide, alkylamine alkylphenol compounds, hydroquinone/quinone compounds, 2,4-di(3-isopropylphenyl)-4-methyl. Examples thereof include -1-pentene, and the imide compound is preferable.

These scorch inhibitors can be used alone or in combination of two or more, and the compounding amount thereof is 0.01 to 5 parts by weight, preferably 0.05 to 100 parts by weight of the rubber component. ˜1 part by weight, more preferably 0.1 to 0.5 part by weight.

The rubber composition of the present invention preferably further contains a filler. The filler is not particularly limited, but examples thereof include a reinforcing filler and a non-reinforcing filler, and the reinforcing filler is preferable.

Examples of the reinforcing filler include carbon black such as furnace black, acetylene black, thermal black, channel black and graphite; silica such as wet silica, dry silica and colloidal silica; and the like. Examples of non-reinforcing fillers include quartz powder, diatomaceous earth, zinc white, basic magnesium carbonate, activated calcium carbonate, magnesium silicate, aluminum silicate, titanium dioxide, talc, aluminum sulfate, calcium sulfate and barium sulfate. be able to.

These fillers can be used alone or in combination of two or more, and the compounding amount thereof is appropriately selected within a range that does not impair the effects of the present invention, and is usually relative to 100 parts by weight of the rubber component. The amount is in the range of 1 to 200 parts by weight, preferably 10 to 150 parts by weight, more preferably 20 to 100 parts by weight.

The rubber composition of the present invention may further contain a silane coupling agent. The silane coupling agent that can be used is not particularly limited, and examples thereof include 3-methacryloxypropyltrimethoxysilane, bis(3-(triethoxysilyl)propyl)disulfide, and bis(3-triethoxysilylpropyl)tri. Sulfide, bis(3-(triethoxysilyl)propyl)tetrasulfide, γ-mercaptopropyltriethoxysilane, 3-[ethoxybis(3,6,9,12,15-pentaoxaoctacosano-1-yloxy)silyl] -1-propanethiol, 3-octanoylthio-1-propyl-triethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, γ-trimethoxysilylpropylbenzothiazyltetrasulfide, 3-tri Methoxysilylpropylbenzothiazole tetrasulfide, 3-thiocyanatopropyltriethoxysilane, vinyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, 3-trimethoxysilylpropylmethacrylate monosulfide, γ- Examples thereof include glycidoxypropyltriethoxysilane, 3-nitropropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 3-chloropropyltrimethoxysilane.

These silane coupling agents can be used alone or in combination of two or more, and the compounding amount thereof is appropriately selected according to the purpose of use and is usually 0.1% with respect to 100 parts by weight of the rubber component. The amount is in the range of 01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, more preferably 0.5 to 3 parts by weight.

The rubber composition of the present invention may contain the above-mentioned cross-linking agent and, if necessary, other compounding agents other than the cross-linking accelerator, the scorch inhibitor, the filler and the silane coupling agent. Other compounding agents include, for example, dispersants such as higher fatty acids and their metal amine salt agents, plasticizers such as phthalic acid derivatives, adipic acid derivatives, sebacic acid derivatives, lubricating oils, process oils, coal tar, castor oil, Softeners such as calcium stearate, anti-aging agents, light stabilizers, processing aids, adhesives, lubricants, flame retardants, mildew-proofing agents, antistatic agents, colorants, crosslinking retardants, polyolefin resins, polystyrene resins, Examples thereof include resins such as polyacrylic resins, polyphenylene ether resins, polyester resins, polycarbonate resins, polyamide resins, vinyl chloride resins, and fluororesins. These other compounding agents may be used alone or in combination of two or more, and the compounding amount thereof is appropriately selected within a range that does not impair the effects of the present invention.

As the method for compounding the rubber composition of the present invention, conventional means conventionally used in the field of polymer processing, for example, an open roll, a Banbury mixer, various kneaders and the like can be used.

The compounding procedure may be carried out by an ordinary procedure performed in the field of polymer processing, for example, a component that is easily reacted or decomposed by heat after sufficiently mixing components that are difficult to react or decompose by heat. It is preferable to mix the crosslinking agent and the like in a short time at a temperature at which reaction or decomposition does not occur.

[Rubber cross-linked product]
The crosslinked rubber of the present invention is obtained by crosslinking the above rubber composition.
The rubber cross-linked product of the present invention is produced by using the rubber composition of the present invention to perform molding using a molding machine corresponding to a desired shape, for example, an extruder, an injection molding machine, a compressor, a roll, etc., and heating. It can be produced by carrying out a crosslinking reaction and fixing the shape as a rubber crosslinked product. In this case, the molding may be performed in advance and then crosslinked, or the molding and the crosslinking may be performed simultaneously. The molding temperature is usually 10 to 200°C, preferably 25 to 150°C. The crosslinking temperature is usually 100 to 250° C., preferably 130 to 220° C., more preferably 150 to 200° C., and the crosslinking time is usually 0.1 minutes to 10 hours, preferably 1 minute to 5 hours. As a heating method, a method used for crosslinking rubber such as press heating, steam heating, oven heating, and hot air heating may be appropriately selected.

The rubber cross-linked product of the present invention may be further heated for secondary cross-linking depending on the shape and size of the rubber cross-linked product. The secondary crosslinking varies depending on the heating method, the crosslinking temperature, the shape, etc., but is preferably 1 to 48 hours. The heating method and heating temperature may be appropriately selected.

The rubber cross-linked product of the present invention has excellent compression set resistance while maintaining basic properties as a rubber such as tensile strength, elongation and hardness. The compression set of the rubber cross-linked product of the present invention measured according to JIS K6262 is appropriately selected according to the purpose of use, but is usually 1 to 50%, preferably 5 to 25%, more preferably 8 Is in the range of up to 20%.

Taking advantage of the above characteristics, the rubber cross-linked product of the present invention is, for example, an O-ring, packing, diaphragm, oil seal, shaft seal, bearing seal, mechanical seal, well head seal, electric/electronic device seal, air compression. Sealing materials such as equipment seals; rocker cover gaskets mounted on the connecting portion between the cylinder block and the cylinder head, oil pan gaskets mounted on the connecting portion between the oil pan and the cylinder head or the transmission case, the positive electrode, the electrolyte plate, and the like. Various gaskets such as gaskets for fuel cell separators, gaskets for top covers of hard disk drives, etc. mounted between a pair of housings that sandwich a unit cell having a negative electrode; cushioning materials, vibration damping materials; wire coating materials; industrial belts; It is preferably used as tubes and hoses; sheets;

Further, the rubber cross-linked product of the present invention is an extrusion molding product and a mold cross-linked product used for automobile applications, for example, fuel hose, filler neck hose, vent hose, paper hose, fuel oil around a fuel tank such as an oil hose. It is preferably used for various hoses such as air hoses such as system hoses, turbo air hoses and emission control hoses, radiator hoses, heater hoses, brake hoses, air conditioner hoses.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. In addition, "part" in each example is based on weight unless otherwise specified.
Various physical properties were evaluated according to the following methods.

[Moonie viscosity (ML1+4, 100°C)]
The Mooney viscosity (polymer Mooney) of acrylic rubber was measured according to JIS K6300.

[Moonies coach test (ML145℃)]
The Mooney scorch time (t5 and t35) and Vmin of the acrylic rubber composition were measured at 145° C. according to JIS K6300. In this measurement, the time when the Mooney viscosity increased from Vmin by 5M was set to t5, and the time when the Mooney viscosity increased from Vmin to 35M was set to t35. The acrylic rubber composition used for the measurement was prepared according to JIS K6299. Larger values of t5 and t35 mean that it takes more time for vulcanization, and it can be judged that the storage stability of the rubber composition is excellent and the vulcanization promoting effect is suppressed (good control). .. A lower value of Vmin means less initial vulcanization of the rubber composition, and it can be judged that the storage stability is excellent.
Further, as a storage stability acceleration test, a Mooney scorch test (a Mooney scorch test after storage) was performed on the acrylic rubber composition stored at 40° C. and 80% humidity for 3 days under the same conditions as above. The difference between Vmin in the Mooney scorch test after storage and Vmin in the Mooney scorch test before storage was defined as ΔVmin. It can be judged that the smaller the value of ΔVmin, the smaller the change in the rubber composition during storage and the better the storage stability.

[Normal physical properties (tensile strength, elongation, hardness)]
The acrylic rubber composition is put into a mold having a length of 15 cm, a width of 15 cm, and a depth of 0.2 cm, and is crosslinked by pressing at 170° C. for 20 minutes while applying a pressing pressure of 10 MPa to obtain a sheet-shaped rubber crosslinked product. It was The obtained rubber cross-linked product was punched with a No. 3 dumbbell to prepare a test piece. The hardness of this test piece was measured using a durometer hardness tester (type A) according to JIS K6253. Furthermore, tensile strength and elongation were measured according to JIS K6251.

[Air heat aging test]
A test piece prepared in the same manner as the test piece used for the evaluation of the normal state physical properties was placed in a gear type oven under an environment of a temperature of 175° C. for 70 hours, and then by the same method as the evaluation of the normal state physical properties. The heat aging resistance was evaluated by measuring the tensile strength, elongation and hardness, and comparing the obtained results with the normal state physical properties measured according to the above method.

[Compression set test]
The acrylic rubber composition is molded and cross-linked by a press at 170° C. for 20 minutes to produce a cylindrical test piece having a diameter of 29 mm and a thickness of 12.5 mm, and further heated at 150° C. for 4 hours to perform secondary cross-linking. Let According to JIS K6262, the test piece after secondary cross-linking obtained above was allowed to stand for 25 hours in an environment of 150° C. while being compressed by 25%, and then the compression was released to set the compression set (%). ) Was measured. The smaller the value of the compression set (%), the more excellent the compression set resistance.

[Example 1]
In a mixing container equipped with a homomixer, 49.95 parts of pure water, 40.9 parts of ethyl acrylate, 35.0 parts of n-butyl acrylate, 20.0 parts of 2-methoxyethyl acrylate, 1.5 parts of acrylonitrile. , 2.6 parts of monochlorovinyl acetate, 0.57 part of sodium lauryl sulfate (trade name "Emar 2FG", manufactured by Kao Corporation) as an anionic emulsifier, and polyoxyethylene/polyoxypropylene copolymer as a nonionic emulsifier. A monomer emulsion was obtained by stirring 1.40 parts (trade name "Pronon 208", manufactured by NOF CORPORATION) and 0.22 parts of sodium L-ascorbate.

Next, 54.19 parts of pure water and 0.95 part of the monomer emulsion obtained above were put into a polymerization reaction tank equipped with a thermometer and a stirrer, and the temperature was 15° C. under a nitrogen stream. Cooled down. Then, in the polymerization reaction tank, 44.74 parts of the monomer emulsion obtained above, 0.0002 parts of ferrous sulfate as a reducing agent, 0.0264 parts of sodium ascorbate as a reducing agent, polymerization 0.066 parts of potassium persulfate as an initiator was continuously added dropwise over 2 hours. Then, while maintaining the temperature in the polymerization reaction tank at 23° C., the reaction was continued for 1 hour, and it was confirmed that the polymerization conversion rate reached 95%. Polymerization was performed by adding hydroquinone as a polymerization terminator. The reaction was stopped and an emulsion polymerization liquid was obtained.

With respect to 100 parts of the emulsion polymerization liquid obtained by the polymerization, mono(or di or tri)(α-methylbenzyl)phenol (trade name "Nocrac SP", manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) as an antioxidant is used. A mixed solution was obtained by mixing 0.03 part. Then, the obtained mixed liquid was transferred to a coagulation tank, 30 parts of industrial water was added to 100 parts of this mixed liquid, the temperature was raised to 85° C., and then the obtained mixed liquid was stirred. The polymer was coagulated by adding 22 parts of magnesium sulfate to 100 parts of the polymer (polymer contained in the emulsion polymerization liquid), thereby obtaining a water-containing crumb of acrylic rubber (A1).

Next, add 388 parts of industrial water to 100 parts of the solid content of the water-containing crumb of the obtained acrylic rubber (A1), stir at room temperature for 5 minutes in the coagulation tank, and then discharge water from the coagulation tank. Then, the hydrous crumb was washed with water. In this example, such washing with water was repeated 4 times.

Next, to 100 parts of the solid content of the water-containing crumb washed with water as described above, an aqueous sulfuric acid solution (pH 3) prepared by mixing 388 parts of industrial water and 0.13 part of concentrated sulfuric acid was added, and at room temperature in the coagulation tank After stirring for 5 minutes, water was discharged from the coagulation tank to pickle the hydrous crumbs. Next, 388 parts of pure water was added to 100 parts of the solid content of the hydrous crumbs pickled, and the mixture was stirred at room temperature for 5 minutes in the coagulation tank, and then the water was discharged from the coagulation tank to obtain the hydrous crumbs. Was washed with pure water, and the hydrous crumb washed with pure water was dried at 110° C. for 1 hour with a hot air dryer (belt conveyor type band dryer) to obtain a solid acrylic rubber (A1). . At this time, no adhesion of acrylic rubber to the hot air dryer was observed.

The acrylic rubber (A1) thus obtained has a Mooney viscosity (ML1+4, 100° C.) of 33, and its composition is as follows: ethyl acrylate unit 40.9% by weight, n-butyl acrylate unit 35.0% by weight, acrylic acid The methoxyethyl unit was 20.0% by weight, the acrylonitrile unit was 1.5% by weight, and the monochlorovinyl acetate unit was 2.6% by weight.

Using a Banbury mixer, 100 parts of the above-obtained acrylic rubber (A1), 60 parts of carbon black (trade name "Seast 116", manufactured by Tokai Carbon Co., Ltd.), 1 part of stearic acid, and 4, 4'- 1 part of bis(α,α-dimethylbenzyl)diphenylamine (trade name “Nocrac CD”, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) was added and mixed at 50° C. for 5 minutes. Then, the obtained mixture was transferred to a roll at 50° C., and 1.0 part of zinc dibutyldithiocarbamate (trade name “NOXCELLER BZ”, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 2,4,6-trimercapto-s. -Triazine (trade name "Disnet F", manufactured by Sankyo Kasei Co., Ltd.) 0.5 parts, N-cyclohexyl thiophthalimide (trade name "Sant Guard PVI", manufactured by Sanshin Chemical Industry Co., Ltd.) 0.3 parts Then, by kneading, an acrylic rubber composition is obtained, and according to the above method, Mooney scorch test, hardness, tensile strength and elongation at break, air heat aging test, compression set test are performed, and the results are shown. Shown in 1.

[Example 2]
An acrylic rubber (A2) was obtained in the same manner as in Example 1 except that 100 parts of sodium sulfate was used instead of 22 parts of magnesium sulfate as a coagulant.
The acrylic rubber (A2) thus obtained has a Mooney viscosity (ML1+4, 100° C.) of 33, and its composition is as follows: ethyl acrylate unit 40.9% by weight, n-butyl acrylate unit 35.0% by weight, acrylic acid The methoxyethyl unit was 20.0% by weight, the acrylonitrile unit was 1.5% by weight, and the monochlorovinyl acetate unit was 2.6% by weight.
Using the resulting acrylic rubber (A2), an acrylic rubber composition was obtained in the same manner as in Example 1, and the Mooney scorch test, hardness, tensile strength and elongation at break, air heat aging test, compression set test were performed. The results were shown in Table 1.

[Example 3]
The monomer composition and the polymerization process were the same as in Example 1 to obtain an emulsion polymerization solution, and to 100 parts of the emulsion polymerization solution obtained by the polymerization, mono (or di or tri) (α- A mixed solution was obtained by mixing 0.06 part of methylbenzyl)phenol (trade name “Raditex SP-50E”, manufactured by Higashi Chemical Co., Ltd., 50% by weight aqueous dispersion). Then, 30 parts of industrial water was added to 100 parts of the obtained mixed solution, and the temperature was adjusted to 80° C., to 110 parts of a 20 wt% magnesium sulfate aqueous solution as a coagulant (22 parts in terms of magnesium sulfate) continuously. The addition caused the polymer to solidify, thereby obtaining a water-containing crumb of acrylic rubber (A3).

Then, in the same manner as in Example 1, the hydrous crumb was washed with water, washed with acid, washed with pure water, and dried to obtain a solid acrylic rubber (A3). At this time, no adhesion of acrylic rubber to the hot air dryer was observed.

The resulting acrylic rubber (A3) has a Mooney viscosity (ML1+4, 100° C.) of 33, and its composition is as follows: ethyl acrylate unit 40.9% by weight, n-butyl acrylate unit 35.0% by weight, acrylic acid The methoxyethyl unit was 20.0% by weight, the acrylonitrile unit was 1.5% by weight, and the monochlorovinyl acetate unit was 2.6% by weight.
Using the resulting acrylic rubber (A3), an acrylic rubber composition was obtained in the same manner as in Example 1, and the Mooney scorch test, hardness, tensile strength and elongation at break, air heat aging test, compression set test were performed. The results were shown in Table 1.

[Example 4]
An acrylic rubber (A4) was obtained in the same manner as in Example 1 except that 500 parts of a 20 wt% sodium sulfate aqueous solution (100 parts in terms of sodium sulfate) was used instead of 22 parts of magnesium sulfate as a coagulant. ..

The acrylic rubber (A4) thus obtained has a Mooney viscosity (ML1+4, 100° C.) of 33. The composition of the acrylic rubber (A4) is ethyl acrylate unit 40.9% by weight and n-butyl acrylate unit 35.0. % By weight, methoxyethyl acrylate unit by 20.0% by weight, acrylonitrile unit by 1.5% by weight, and monochlorovinyl acetate unit by 2.6% by weight.
Using the resulting acrylic rubber (A4), an acrylic rubber composition was obtained in the same manner as in Example 1, and the Mooney scorch test, hardness, tensile strength and elongation at break, air heat aging test, compression set test were performed. The results are shown in Table 1.

[Example 5]
Instead of sodium lauryl sulfate as an anionic emulsifier, polyoxyethylene alkylphenyl ether phosphate ester sodium salt of polyoxyethylene alkylphenol phosphate ester (trade name "phosphanol LO-529", manufactured by Toho Chemical Co., Ltd., hydrophobic group A solid acrylic rubber (A5) was obtained in the same manner as in Example 1 except that the phosphoric acid ester salt of a higher alcohol having 15 carbon atoms was used.

The Mooney viscosity (ML1+4, 100° C.) of the obtained acrylic rubber (A5) was 33, and the composition of the acrylic rubber (A5) was 40.9% by weight of ethyl acrylate unit and 35.0% of n-butyl acrylate unit. % By weight, methoxyethyl acrylate unit by 20.0% by weight, acrylonitrile unit by 1.5% by weight, and monochlorovinyl acetate unit by 2.6% by weight.
Using the resulting acrylic rubber (A5), an acrylic rubber composition was prepared in the same manner as in Example 1, and the Mooney scorch test, hardness, tensile strength and elongation at break, air heat aging test, compression set test were conducted. The results were shown in Table 1.

[Example 6]
Instead of sodium lauryl sulfate as an anionic emulsifier, polyoxyethylene alkyl ether phosphate (trade name "phosphanol RA-600", manufactured by Toho Chemical Co., Ltd., has 6 to 10 carbon atoms in a hydrophobic group (alkyl group). A solid acrylic rubber (A6) was obtained in the same manner as in Example 1 except that the sodium salt of the higher alcohol phosphoric acid ester salt was used.

The resulting acrylic rubber (A6) has a Mooney viscosity (ML1+4, 100° C.) of 33, and the composition of the acrylic rubber (A6) is as follows: ethyl acrylate unit 40.9% by weight, n-butyl acrylate unit 35.0. % By weight, methoxyethyl acrylate unit by 20.0% by weight, acrylonitrile unit by 1.5% by weight, and monochlorovinyl acetate unit by 2.6% by weight.
Using the resulting acrylic rubber (A6), an acrylic rubber composition was obtained in the same manner as in Example 1, and the Mooney scorch test, hardness, tensile strength and elongation at break, air heat aging test, compression set test were performed. The results were shown in Table 1.

[Comparative Example 1]
A solid acrylic rubber (C1) was obtained in the same manner as in Example 1 except that 4 parts of calcium chloride was used instead of 22 parts of magnesium sulfate as a coagulant.

The acrylic rubber (C1) thus obtained has a Mooney viscosity (ML1+4, 100° C.) of 33, and its composition is as follows: ethyl acrylate unit 40.9% by weight, n-butyl acrylate unit 35.0% by weight, acrylic acid The methoxyethyl unit was 20.0% by weight, the acrylonitrile unit was 1.5% by weight, and the monochlorovinyl acetate unit was 2.6% by weight.
Using the resulting acrylic rubber (C1), an acrylic rubber composition was obtained in the same manner as in Example 1, and the Mooney scorch test, hardness, tensile strength and elongation at break, air heat aging test, compression set test were performed. The results were shown in Table 1.

[Comparative Example 2]
A solid acrylic rubber (C2) was obtained in the same manner as in Example 1 except that 80 parts of sodium chloride was used instead of 22 parts of magnesium sulfate as a coagulant.

The resulting acrylic rubber (C2) has a Mooney viscosity (ML1+4, 100° C.) of 33, and its composition is as follows: ethyl acrylate unit 40.9% by weight, n-butyl acrylate unit 35.0% by weight, acrylic acid The methoxyethyl unit was 20.0% by weight, the acrylonitrile unit was 1.5% by weight, and the monochlorovinyl acetate unit was 2.6% by weight.
Using the obtained acrylic rubber (C2), an acrylic rubber composition was obtained in the same manner as in Example 1, and the Mooney scorch test, hardness, tensile strength and elongation at break, air heat aging test, compression set test were performed. The results were shown in Table 1.

（＊１）２０重量％水溶液の状態で添加
（＊２）２０重量％水溶液の状態で添加

(*1) Add in 20 wt% aqueous solution (*2) Add in 20 wt% aqueous solution

From Table 1, a crosslinkable acrylic rubber produced by polymerizing a monomer containing a crosslinkable monomer using a redox catalyst in the presence of a nonionic emulsifier and an anionic emulsifier and coagulating with a metal sulfate (Implementation) Examples 1 to 6) are quite comparable to those obtained by coagulating with a conventionally used coagulant in a normal state physical property test, an air heat aging test and a compression set test of a crosslinked product (Comparative Examples 1 and 2). You can see that there is no.

On the other hand, in the Mooney scorch test, the acrylic rubber produced according to the present invention has initial physical properties (Vmin: smaller is better) and can be suppressed by nearly 10% as compared with the conventional technique, and long-term physical properties (t5, (t35: the longer both are better), but it is improved by about 10 to 50% compared to the conventional technique, and it is understood that the storage stability is remarkably improved. Further, in the test of Mooney scorch after heat aging, the acrylic rubbers (Examples 1 to 4) produced by the present invention show the same results as the above, and are significantly improved in the change of Vmin. Recognize. Further, among the acrylic rubbers produced by the present invention, the one using the divalent metal sulfate (Examples 1 and 3) can obtain a higher effect than the one using the monovalent metal sulfate. Recognize.

Claims (26)

A monomer containing a (meth)acrylic acid ester and at least one crosslinkable monomer selected from the group consisting of a carboxyl group-containing monomer, an epoxy group-containing monomer and a halogen group-containing monomer. An emulsion polymerization step of obtaining an emulsion polymerization liquid by emulsion polymerization using a polymerization initiator in the presence of a nonionic emulsifier and an anionic emulsifier,
A coagulation step of contacting the emulsion polymerization liquid with a metal sulfate to coagulate to obtain a hydrous crumb,
A washing step of washing the hydrous crumb,
A drying step of drying the washed water-containing crumb,
A method for producing an acrylic rubber, comprising: The method for producing an acrylic rubber according to claim 1, wherein the ratio of the nonionic emulsifier to the anionic emulsifier used is in the range of 1/99 to 99/1 in terms of the weight ratio of nonionic emulsifier/anionic emulsifier. The acrylic rubber according to any one of claims 1 to 2, wherein the ratio of the nonionic emulsifier to the anionic emulsifier used is in the range of 50/50 to 75/25 in terms of the weight ratio of nonionic emulsifier/anionic emulsifier. Manufacturing method. The method for producing an acrylic rubber according to claim 1, wherein the polymerization initiator is combined with a reducing agent. The method for producing an acrylic rubber according to claim 4, wherein at least two kinds of compounds are used as the reducing agent. The method for producing an acrylic rubber according to claim 4, wherein a metal ion-containing compound in a reduced state and a reducing agent other than the metal ion-containing compound in the reduced state are used in combination as the reducing agent. The method for producing an acrylic rubber according to claim 6, wherein the metal ion-containing compound in the reduced state is ferrous sulfate. The method for producing an acrylic rubber according to claim 6 or 7, wherein the reducing agent other than the metal ion-containing compound in the reduced state is sodium formaldehyde sulfoxylate, ascorbic acid or ascorbic acid salt. The method for producing an acrylic rubber according to claim 6 or 7, wherein the reducing agent other than the metal ion-containing compound in the reduced state is ascorbate. The method for producing an acrylic rubber according to claim 1, wherein the polymerization initiator is an organic peroxide or an inorganic peroxide. The contact between the emulsion polymerization solution and the metal sulfate, either by adding the metal sulfate to the emulsion polymerization solution, or by adding the emulsion polymerization solution to a solution or dispersion of gold metal sulfate. The method for producing an acrylic rubber according to any one of claims 1 to 10, which is carried out by the method of. The method for producing an acrylic rubber according to claim 1, wherein a contact temperature between the emulsion polymerization liquid and the metal sulfate is 60° C. or higher. The method for producing an acrylic rubber according to claim 1, wherein the metal sulfate is a monovalent or divalent metal sulfate. The method for producing an acrylic rubber according to claim 1, wherein the anionic emulsifier is a phosphoric acid ester salt. The method for producing an acrylic rubber according to claim 1, wherein the cleaning includes acid cleaning. An acrylic rubber produced by the production method according to claim 1. The monomer composition is (meth)acrylic acid ester monomer unit 50 to 99.9% by weight, crosslinkable monomer unit 0.01 to 20% by weight, and other copolymerizable monomer unit 0 to 0. The acrylic rubber according to claim 16, which is 49.99% by weight. The acrylic rubber according to claim 16 or 17, having a Mooney viscosity (ML1+4, 100°C) in the range of 10 to 150. A rubber composition comprising a rubber component containing the acrylic rubber according to claim 16 and a crosslinking agent. The cross-linking agent is selected from the group consisting of polyamine compounds, polyepoxy compounds, polycarboxylic acids, organic carboxylic acid ammonium salts, organic carboxylic acid metal salts, isocyanuric acid compounds, triazine compounds, and metal soap/sulfur. The rubber composition according to claim 19, which is at least one kind. The rubber composition according to claim 20, further comprising a crosslinking accelerator. The crosslinking accelerator is a guanidine-based crosslinking accelerator, a diazabicycloalkene-based crosslinking accelerator, an aliphatic secondary amine-based crosslinking accelerator, an aliphatic tertiary amine-based crosslinking accelerator, and a dithiocarbomate-based vulcanization accelerator. 22. The rubber composition according to claim 21, which is at least one selected from the group consisting of: The rubber composition according to claim 21 or 22, further comprising a scorch inhibitor. The rubber composition according to any one of claims 19 to 23, further comprising an antioxidant. The rubber composition according to any one of claims 19 to 24, which further comprises a filler. A rubber cross-linked product obtained by cross-linking the rubber composition according to any one of claims 19 to 25.