JP7010318B2 - Acrylic rubber manufacturing method - Google Patents

Description

The present invention relates to a method for producing acrylic rubber, and more particularly to a method for producing acrylic rubber capable of giving a rubber crosslinked product having excellent water resistance.

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

Such acrylic rubber is usually obtained by emulsion-polymerizing a monomer mixture constituting acrylic rubber, coagulating it by adding a coagulant to the obtained emulsion polymerization solution, and drying the hydrous crumb obtained by coagulation. (For example, see Patent Document 1).

On the other hand, in recent years, various members for automobiles, such as sealing materials, hose materials, vibration-proof materials, tube materials, belt materials, and boot materials, have excellent water resistance in addition to heat resistance and oil resistance. Is required. However, conventional acrylic rubbers such as the acrylic rubber described in Patent Document 1 do not always have sufficient water resistance, and therefore cannot meet the recent demand for water resistance.

Japanese Unexamined Patent Publication No. 7-1452291

The present invention has been made in view of such an actual situation, and an object of the present invention is to provide a method for producing acrylic rubber capable of providing a rubber crosslinked product having excellent water resistance.

According to the present invention, it is a method for producing acrylic rubber having Mooney viscosity (ML1 + 4, 100 ° C.) of 10 to 80, and is emulsion polymerization by emulsion polymerization of a monomer for forming the acrylic rubber. A water-containing crumb by an emulsion polymerization step of obtaining a liquid, an ethylene oxide polymer addition step of adding an ethylene oxide polymer to the emulsion polymerization liquid before coagulation, and coagulation of the emulsion polymerization liquid with a coagulant. A method for producing acrylic rubber is provided, comprising a solidification step of obtaining the above.

In the production method of the present invention, it is preferable that the acrylic rubber contains a crosslinkable monomer unit, and the acrylic rubber is an α, β-ethylenically unsaturated carboxylic acid simple substance as the crosslinkable monomer unit. It is more preferable to contain a weight unit.

In the production method of the present invention, the content of the crosslinkable monomer unit in the acrylic rubber is preferably 0.1 to 10% by weight.
In the production method of the present invention, it is preferably 10,000 to 200,000.
In the production method of the present invention, the ethylene oxide-based polymer is preferably an ethylene oxide homopolymer.
In the production method of the present invention, the amount of the ethylene oxide-based polymer added in the step of adding the ethylene oxide-based polymer is 0.005 to 1 weight by weight with respect to 100 parts by weight of the monomer for forming the acrylic rubber. It is preferably a part.

In the production method of the present invention, the emulsion polymerization of the monomer is preferably carried out in the presence of a nonionic emulsifier and an anionic emulsifier, and the amount of the nonionic emulsifier and the anionic emulsifier used is adjusted to the nonionic emulsifier / anion. The weight ratio of the sex emulsifier is more preferably 50/50 to 75/25.
In the production method of the present invention, in the emulsion polymerization step, the monomer, the polymerization initiator and the reducing agent for forming the acrylic rubber are continuously added dropwise to the polymerization reaction system from the start of the polymerization reaction to an arbitrary time. It is preferable to carry out the emulsion polymerization reaction while carrying out the emulsion polymerization reaction.
In the production method of the present invention, the polymerization reaction system is in the state of a monomer emulsion obtained by mixing the monomer for forming the acrylic rubber with an emulsifier and water from the start of the polymerization reaction to an arbitrary time. It is preferable to carry out the emulsion polymerization reaction while continuously dropping the mixture.

Further, according to the present invention, there is provided a method for producing an acrylic rubber composition, which comprises a step of blending a cross-linking agent with the acrylic rubber obtained by the above-mentioned production method.
Further, according to the present invention, there is provided a method for producing a rubber crosslinked product, which comprises a step of cross-linking the acrylic rubber composition obtained by the above production method.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a method for producing acrylic rubber capable of giving a rubber crosslinked product having excellent water resistance.

<Acrylic rubber>
First, the acrylic rubber produced by the production method of the present invention will be described.
The acrylic rubber produced by the production method of the present invention is a (meth) acrylic acid ester as a main component (in the present invention, it means a rubber having 50% by weight or more in the total monomer unit of rubber) in the molecule. Monomer [Acrylic acid ester monomer and / or methacrylic acid ester monomer. Hereinafter, the same applies to methyl (meth) acrylate and the like. ] It is a rubber-like polymer containing a unit.

The (meth) acrylic acid ester monomer forming the (meth) acrylic acid ester monomer unit which is the main component of the acrylic rubber produced by the production method of the present invention is not particularly limited, but is, for example, (meth). ) Acrylic acid alkyl ester monomer, (meth) acrylic acid alkoxyalkyl ester monomer and the like can be mentioned.

The (meth) acrylic acid alkyl ester monomer is not particularly limited, but an ester of alkanol having 1 to 8 carbon atoms and (meth) acrylic acid is preferable, and specifically, methyl (meth) acrylic acid, ( Ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-hexyl (meth) acrylate, (meth) 2-Ethylhexyl acrylate, cyclohexyl (meth) acrylate and the like can be mentioned. Among these, ethyl (meth) acrylate and n-butyl (meth) acrylate are preferable, and ethyl acrylate and n-butyl acrylate are particularly preferable. These can be used alone or in combination of two or more.

The (meth) acrylic acid alkoxyalkyl ester monomer is not particularly limited, but an ester of an alkoxyalkyl alcohol having 2 to 8 carbon atoms and (meth) acrylic acid is preferable, and specifically, (meth) acrylic acid. Methoxymethyl, ethoxymethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-propoxyethyl (meth) acrylate, 2-butoxyethyl (meth) acrylate , 3-Methoxypropyl (meth) acrylate, 4-methoxybutyl (meth) acrylate and the like. Among these, 2-ethoxyethyl (meth) acrylate and 2-methoxyethyl (meth) acrylate are preferable, and 2-ethoxyethyl acrylate and 2-methoxyethyl acrylate are particularly preferable. These can be used alone or in combination of two or more.

The content of the (meth) acrylic acid ester monomer unit in the acrylic rubber produced by the production method of the present invention is usually 50 to 99.9% by weight, preferably 60 to 99.5% by weight, and more. It is preferably 70 to 99.5% by weight. If the content of the (meth) acrylic acid ester monomer unit is too small, the weather resistance, heat resistance, and oil resistance of the obtained rubber crosslinked product may decrease, while if it is too large, the obtained rubber crosslinked product may be deteriorated. The heat resistance of the object may decrease.

In the acrylic rubber produced by the production method of the present invention, the (meth) acrylic acid ester monomer unit includes 30 to 100% by weight of the (meth) acrylic acid alkyl ester monomer unit, and (meth) acrylic. It is preferable to use an acid alkoxyalkyl ester monomer unit consisting of 70 to 0% by weight.

The acrylic rubber produced by the production method of the present invention may contain a crosslinkable monomer unit, if necessary, in addition to the (meth) acrylic acid alkyl ester monomer unit. The crosslinkable monomer forming the crosslinkable monomer unit is not particularly limited, and is, for example, α, β-ethylenically unsaturated carboxylic acid monomer; a monomer having an epoxy group; having a halogen atom. Monomer; diene monomer; and the like.

The α, β-ethylenically unsaturated carboxylic acid monomer forming the α, β-ethylenically unsaturated carboxylic acid monomer unit is not particularly limited, but is, for example, α, β-having 3 to 12 carbon atoms. Ethyl unsaturated monocarboxylic acid, α, β-ethylenic unsaturated dicarboxylic acid with 4-12 carbon atoms, α, β-ethylenic unsaturated dicarboxylic acid with 4-12 carbon atoms and alkanol with 1-8 carbon atoms And monoester. By using the α, β-ethylenically unsaturated carboxylic acid monomer, the acrylic rubber can be made into a carboxyl group-containing acrylic rubber having a carboxyl group as a cross-linking point, whereby a rubber cross-linked product can be obtained. , The compression resistance and permanent strain resistance can be further improved.

Specific 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.
Specific examples of the α, β-ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms include butendionic acids such as fumaric acid and maleic acid; itaconic acid; citraconic acid; chloromaleic acid; and the like.
Specific examples of the monoester of α, β-ethylenic 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 malein. Butendionic acid monochain alkyl esters such as monomethyl acid, monoethyl maleate, monon-butyl maleate; monocyclopentyl fumarate, monocyclohexyl fumarate, monocyclohexenyl fumarate, monocyclopentyl maleate, monocyclohexyl maleate, malein Examples thereof include butendionic acid monoesters having an alicyclic structure such as monocyclohexenyl acid acid; monomethyl itaconate, monoethyl itaconate, monon-butyl itaconate, monocyclohexylitaconate and the like; and the like.
Among these, a monoester of α, β-ethylenically unsaturated dicarboxylic acid having 4 to 12 carbon atoms and an alkanol having 1 to 8 carbon atoms is preferable, and a monoester of butendionic acid or butendion having an alicyclic structure is preferable. Acid monoesters are more preferred, mono-butyl fumarate, mono n-butyl maleate, monocyclohexyl fumarate, and monocyclohexyl maleate are even more preferred, and mono n-butyl fumarate is particularly preferred. These α, β-ethylenically unsaturated carboxylic acid monomers can be used alone or in combination of two or more. Among the above-mentioned monomers, the dicarboxylic acid includes those existing as an anhydride.

The monomer having an epoxy group is not particularly limited, and for example, an epoxy group-containing (meth) acrylic acid ester such as glycidyl (meth) acrylate; an epoxy group-containing ether such as allyl glycidyl ether and vinyl glycidyl ether; and the like. Can be mentioned.

The monomer having a halogen atom is not particularly limited, and for example, an unsaturated alcohol ester of a halogen-containing saturated carboxylic acid, a (meth) acrylic acid haloalkyl ester, a (meth) acrylic acid haloacyloxyalkyl ester, and a (meth) acrylic. Examples thereof include acid (haloacetylcarbamoyloxy) alkyl esters, halogen-containing unsaturated ethers, halogen-containing unsaturated ketones, halomethyl group-containing aromatic vinyl compounds, halogen-containing unsaturated amides, and haloacetyl group-containing unsaturated monomers.

Specific examples of the unsaturated alcohol ester of the halogen-containing saturated carboxylic acid include vinyl chloroacetate, vinyl 2-chloropropionate, and allyl chloroacetic acid.
Specific examples of the (meth) acrylic acid haloalkyl ester include (meth) acrylic acid chloromethyl, (meth) acrylic acid 1-chloroethyl, (meth) acrylic acid 2-chloroethyl, and (meth) acrylic acid 1,2-dichloroethyl. , 2-Chloropropyl (meth) acrylic acid, 3-chloropropyl (meth) acrylic acid, and 2,3-dichloropropyl (meth) acrylic acid.
Specific examples of the (meth) acrylic acid haloacyloxyalkyl ester include (meth) acrylic acid 2- (chloroacetoxy) ethyl, (meth) acrylic acid 2- (chloroacetoxy) propyl, and (meth) acrylic acid 3- (chloro). Examples thereof include acetoxy) propyl and 3- (hydroxychloroacetoxy) propyl (meth) acrylate.
Specific examples of the (meth) acrylic acid (haloacetylcarbamoyloxy) alkyl ester include (meth) acrylic acid 2- (chloroacetylcarbamoyloxy) ethyl and (meth) acrylic acid 3- (chloroacetylcarbamoyloxy) propyl. Can be mentioned.

Specific 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.
Specific examples of the halogen-containing unsaturated ketone include 2-chloroethyl vinyl ketone, 3-chloropropyl vinyl ketone, 2-chloroethyl allyl ketone and the like.
Specific examples of the halomethyl group-containing aromatic vinyl compound include p-chloromethylstyrene, m-chloromethylstyrene, o-chloromethylstyrene, and p-chloromethyl-α-methylstyrene.

Specific examples of the halogen-containing unsaturated amide include N-chloromethyl (meth) acrylamide.
Specific examples of the haloacetyl group-containing unsaturated monomer include 3- (hydroxychloroacetoxy) propyl allyl ether and p-vinylbenzylchloroacetic acid ester.

Examples of the diene monomer include a conjugated diene monomer and a non-conjugated diene monomer.
Specific examples of the conjugated diene monomer include 1,3-butadiene, isoprene, piperylene and the like.
Specific examples of the non-conjugated diene monomer include ethylidene norbornene, dicyclopentadiene, dicyclopentadienyl (meth) acrylate, and 2-dicyclopentadienyl ethyl (meth) acrylate. ..

Among the crosslinkable monomers, when an α, β-ethylenically unsaturated carboxylic acid monomer is used, the acrylic rubber can be a carboxyl group-containing acrylic rubber. By using acrylic rubber containing a carboxyl group as the acrylic rubber, it is possible to improve the compression resistance and permanent strain resistance while improving the oil resistance and heat resistance.

The content of the crosslinkable monomer unit in the acrylic rubber produced by the production method of the present invention is preferably 0.1 to 10% by weight, more preferably 0.5 to 7% by weight, still more preferably 0. .5 to 5% by weight. By setting the content of the crosslinkable monomer unit in the above range, it is possible to more appropriately enhance the compression resistance and permanent strain resistance while improving the mechanical properties and heat resistance of the obtained rubber crosslinked product.

The acrylic rubber produced by the production method of the present invention is a (meth) acrylic acid ester monomer unit, and a crosslinkable monomer unit used as needed, as well as other simple monomers copolymerizable with these. It may have a unit of a meter. Examples of such copolymerizable monomers include aromatic vinyl monomers, α, β-ethylenically unsaturated nitrile monomers, acrylamide-based monomers, and other olefin-based monomers. Can be mentioned.

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-based 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.

The other copolymerizable monomers may be used alone or in combination of two or more. The content of the unit of these other copolymerizable monomers in the acrylic rubber of the present invention is usually 49.9% by weight or less, preferably 39.5% by weight or less, and more preferably 29.5% by weight. % Or less.

<Manufacturing method of acrylic rubber>
Next, the method for producing the acrylic rubber of the present invention will be described.
The method for producing acrylic rubber of the present invention is:
An emulsion polymerization step of obtaining an emulsion polymerization solution by emulsion polymerization of a monomer for forming acrylic rubber, and
An ethylene oxide-based polymer addition step of incorporating an ethylene oxide-based polymer into the emulsion polymerization solution before solidification, and a step of adding the ethylene oxide-based polymer.
It comprises a coagulation step of obtaining a water-containing crumb by adding a coagulant to the emulsion polymer solution adjusted to a temperature of 78 ° C. or higher and coagulating it.

Alternatively, as a method for producing an acrylic rubber of the present invention, in the above emulsion polymerization step, a monomer for forming an acrylic rubber is mixed in advance with an emulsifier and water to obtain a monomer emulsified liquid (emulsified liquid). It is also possible to carry out emulsion polymerization in the state of the obtained monomeric emulsion (preparation step) (emulsification polymerization step). It is also possible to configure the structure so that emulsion polymerization is carried out after adding an ethylene oxide polymer.

<Emulsion polymerization process>
The emulsion polymerization step in the production method of the present invention is a step of obtaining an emulsion polymerization solution by emulsion polymerization of a monomer for forming acrylic rubber.

As the emulsion polymerization method in the emulsion polymerization step, an ordinary method may be used, and an emulsifier, a polymerization initiator, a polymerization terminator and the like can be used according to a conventional method.

The emulsifier is not particularly limited, and for example, polyoxyethylene alkyl ether such as polyoxyethylene dodecyl ether, polyoxyethylene alkylphenol ether such as polyoxyethylene nonylphenyl ether, and polyoxyethylene alkyl such as polyoxyethylene stearate ester. Nonionic emulsifiers such as esters, polyoxyethylene sorbitan alkyl esters, polyoxyethylene polyoxypropylene copolymers; salts of fatty acids such as myristic acid, palmitic acid, oleic acid and linolenic acid, and alkylbenzene sulfone such as sodium dodecylbenzene sulfonate. Higher alcohol sulfates such as acid salts, sodium lauryl sulfates, higher phosphoric acid ester salts such as sodium alkylphosphates, anionic emulsifiers such as alkylsulfosuccinates; alkyltrimethylammonium chlorides, dialkylammonium chlorides, benzylammonium chlorides, etc. Cationic esterifiers; and the like. These emulsifiers can be used alone or in combination of two or more. Among these nonionic emulsifiers, polyoxyethylene polypropylene glycol, polyethylene glycol monostearate, polyoxyethylene alkyl ether, and polyoxyethylene alkyl phenol ether are preferable. As the nonionic emulsifier, those having a weight average molecular weight of less than 10,000 are preferable, those having a weight average molecular weight of 500 to 8000 are more preferable, and those having a weight average molecular weight of 600 to 5000 are further preferable. Further, among these anionic emulsifiers, higher phosphoric acid ester salts and higher alcohol sulfate ester salts are preferable.

Among these emulsifiers, at least one of a nonionic emulsifier and an anionic emulsifier is preferable, at least an anionic emulsifier is more preferably contained, and it is further preferable to use a nonionic emulsifier and an anionic emulsifier in combination. By using the nonionic emulsifier and the anionic emulsifier in combination, the coagulation described later is performed while effectively suppressing the generation of stains due to the adhesion of the polymer aggregates to the polymerization apparatus (for example, the polymerization tank) during emulsion polymerization. It is possible to reduce the amount of the coagulant used in the process, and as a result, the amount of the coagulant in the finally obtained acrylic rubber can be reduced, and the water resistance of the rubber crosslinked product obtained thereby can be further improved. Can be improved.

Further, by using the nonionic emulsifier and the anionic emulsifier in combination, the emulsifying action can be enhanced, so that the amount of the emulsifier itself used can be reduced, and as a result, in the finally obtained acrylic rubber. It is possible to reduce the residual amount of the emulsifier contained in the acrylic rubber, thereby further increasing the water resistance of the obtained acrylic rubber.

The amount of the emulsifier used in the production method of the present invention is the total amount of the emulsifier used with respect to 100 parts by weight of the monomer used for the polymerization, preferably 0.1 to 5 parts by weight, and more preferably 0.5 to 4 parts by weight. , More preferably 1 to 3 parts by weight. When the nonionic emulsifier and the anionic emulsifier are used in combination, the amount of the nonionic emulsifier used is more than 0 parts by weight, preferably 0 parts by weight, based on 100 parts by weight of the monomer used for polymerization. .1 to 3 parts by weight, more preferably 0.5 to 2 parts by weight, still more preferably 0.7 to 1.7 parts by weight, and the amount of the anionic emulsifier used is 100 parts by weight of the monomer used for polymerization. On the other hand, it is more than 0 parts by weight, 4 parts by weight, preferably 0.1 to 3 parts by weight, more preferably 0.5 to 2 parts by weight, and further preferably 0.35 to 0.75 parts by weight. When the nonionic emulsifier and the anionic emulsifier are used in combination, the weight ratio of the nonionic emulsifier / anionic emulsifier is preferably 1/99 to 99/1, preferably 10/90 to 80/20. More preferably, 25/75 to 75/25 is even more preferable, 50/50 to 75/25 is even more preferable, and 65/35 to 75/25 is particularly preferable.

Examples of the polymerization initiator include azo compounds such as azobisisobutyronitrile; organic peroxides such as diisopropylbenzene hydroperoxide, cumene hydroperoxide, paramentan hydroperoxide, and benzoyl peroxide; sodium persulfate and 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. 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.

Further, the organic peroxide and the inorganic peroxide as the polymerization initiator are preferably used as the redox-based polymerization initiator in combination with the reducing agent. The reducing agent used in combination is not particularly limited, but is a compound containing metal ions in a reduced state such as ferrous sulfate, sodium hexamethylenediamine tetraacetate, and ferrous naphthenate; ascorbic acid and sodium ascorbate. , Ascorbic acid (salt) such as potassium ascorbate; erythorbic acid (salt) such as erythorbic acid, sodium erisorbate, potassium bisulfite; saccharides; sulphinate such as sodium hydroxymethanesulfite; sodium sulfite, potassium sulfite, sulfite Sodium bisulfite, aldehyde sodium bisulfite, potassium hydrogen sulfite sulfite; sodium pyrosulfite, potassium pyrosulfite, sodium pyrosulfite, potassium pyrosulfite, etc., pyrosulfite; sodium thiosulfate, potassium thiosulfate, etc. ; Phosphoric acid, sodium bisulfite, potassium phosphite, sodium bisulfite, potassium bisulfite phosphite (salt); pyrosulfite, sodium pyrosulfite, potassium pyrosulfite, sodium pyrosulfite, pyrosulfite Pyrobisulfite (salt) such as potassium hydrogen phosphate; sodium formaldehyde sulfoxylate and the like. These reducing agents can be used alone or in combination of two or more. The amount of the reducing agent used is preferably 0.0003 to 0.5 parts by weight with respect to 100 parts by weight of the monomer used for the polymerization.

Examples of the polymerization terminator include hydroxylamine, hydroxyamine sulfate, diethylhydroxyamine, hydroxyamine sulfonic acid and its alkali metal salt, sodium dimethyldithiocarbamate, hydroquinone and the like. The amount of the polymerization inhibitor 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.

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 the polymerization.

In emulsion polymerization, if necessary, polymerization auxiliary materials such as a molecular weight adjusting agent, a particle size adjusting agent, a chelating agent, and an oxygen scavenger can be used.

The emulsion polymerization may be carried out by any of a batch method, a semi-batch method and a continuous method, but the semi-batch method is preferable. Specifically, in a reaction system containing a polymerization initiator and a reducing agent, a monomer used for polymerization is continuously added dropwise to the polymerization reaction system from the start of the polymerization reaction to an arbitrary time to carry out the polymerization reaction. It is preferable to carry out the polymerization reaction by continuously dropping the monomer, the polymerization initiator, and the reducing agent used for the polymerization into the polymerization reaction system from the start of the polymerization reaction to an arbitrary time. It is more preferable to carry out the polymerization reaction by continuously dropping all of the monomer, the polymerization initiator and the reducing agent used for the polymerization into the polymerization reaction system 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, and thereby the polymerization reaction rate can be improved. The polymerization is usually carried out in a temperature range of 0 to 70 ° C, preferably 5 to 50 ° C.

When the polymerization reaction is carried out while continuously dropping the monomer used for the polymerization, the monomer used for the polymerization is mixed with an emulsifier and water to form a monomer emulsion, and the monomer is prepared. It is preferable to continuously drop the emulsion in the state of an emulsion. The method for preparing the monomer emulsion is not particularly limited, and a method of stirring the total amount of the monomer used for the polymerization, the total amount of the emulsifier, and water using a stirrer such as a homomixer or a disc turbine may 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.

In addition, when the polymerization reaction is carried out by continuously dropping the monomer, the polymerization initiator, and the reducing agent used for the polymerization into the polymerization reaction system from the start of the polymerization reaction to an arbitrary time, these are separated. The polymerization initiator and the reducing agent may be added dropwise to the polymerization system using the dropping device of the above, or at least the polymerization initiator and the reducing agent may be mixed in advance and, if necessary, dropped from the same dropping device into the polymerization system as an aqueous solution. You may. After the completion of the dropping, the reaction may be continued for an arbitrary time in order to further improve the polymerization reaction rate.

<Ethylene oxide polymer addition process>
The step of adding the ethylene oxide-based polymer in the production method of the present invention is a step of adding the ethylene oxide-based polymer to the emulsion polymerization solution before coagulation.

The method for incorporating the ethylene oxide-based polymer into the emulsion polymerization solution is not particularly limited, and the method is such that the emulsion polymerization solution before coagulation can be in a state of containing the ethylene oxide-based polymer. Anything is fine as long as it is. For example, an ethylene oxide-based polymer may be added to the emulsion polymerization solution after emulsion polymerization, or a solution before emulsion polymerization, specifically, a solution to be subjected to emulsion polymerization (for example, to form acrylic rubber). An ethylene oxide-based polymer is added to a monomer emulsion obtained by mixing the monomer of (1) with an emulsifier and water, and emulsion polymerization is carried out in the presence of the ethylene oxide-based polymer to carry out ethylene oxide. An emulsion polymerization solution containing a system polymer may be obtained. Among these, since the amount of the coagulant used in the coagulation step described later can be reduced and the water resistance can be further enhanced, the ethylene oxide polymer should be added to the emulsion polymerization solution after the emulsion polymerization. It is preferable that the mode is the same. The form of addition of the ethylene oxide polymer is not particularly limited, but when the ethylene oxide polymer is solid at room temperature, it may be added in the solid state or dissolved in a solvent such as water. It may be added in a state.

According to the production method of the present invention, the ethylene oxide-based polymer is previously contained in the emulsion polymerization solution before coagulation, and in the presence of such an ethylene oxide-based polymer, coagulation in the coagulation step described later. By performing the above at 78 ° C. or higher, the coagulability of the emulsion polymerization solution can be improved, and thereby the amount of the coagulant in the coagulation step can be reduced. As a result, the residual amount of the coagulant in the finally obtained acrylic rubber can be reduced, and the water resistance in the case of a rubber crosslinked product can be further improved. In particular, according to the present inventors, a diligent study on the relationship between the residual amount of the coagulant in the acrylic rubber and the water resistance of the obtained rubber crosslinked product revealed that the residual amount of the coagulant in the acrylic rubber was found. If the amount is too large, the water resistance of the obtained rubber crosslinked product will decrease, and by coagulating at a temperature of 78 ° C or higher in the presence of an ethylene oxide polymer, the amount of coagulant used can be reduced, resulting in acrylic. It has been found that the residual amount of the coagulant in the rubber can be reduced.

The ethylene oxide-based polymer may be a polymer having a polyethylene oxide structure as the main chain structure, and is not particularly limited, but is preferably a polymer having substantially only a polyethylene oxide structure, and specifically. Examples thereof include polyethylene oxide, polypropylene oxide, and ethylene oxide / propylene oxide copolymers, and among them, polyethylene oxide, that is, an ethylene oxide homopolymer is preferable. The weight average molecular weight of the ethylene oxide polymer is preferably 10,000 to 1,000,000, more preferably 10,000 to 200,000, and even more preferably 20,000 to 120,000.

The amount of the ethylene oxide polymer added in the step of adding the ethylene oxide polymer is preferably 0.005 to 1 part by weight, more preferably 0.006 to 0, based on 100 parts by weight of the acrylic rubber component in the emulsion polymer solution. It is 6.6 parts by weight, more preferably 0.007 to 0.5 parts by weight, still more preferably 0.01 to 0.1 parts by weight, and particularly preferably 0.02 to 0.06 parts by weight.

Further, in the production method of the present invention, in addition to the ethylene oxide-based polymer, some of the compounding agents to be blended in acrylic rubber, specifically, antiaging agents and / or lubricants are also coagulated. It is preferable to include it in the emulsion polymerization solution before the process.

For example, by preliminarily containing an antiaging agent in the emulsion polymerization solution before coagulation, deterioration of acrylic rubber due to heat during drying in a drying step described later can be effectively suppressed. Specifically, it is possible to effectively suppress the decrease in Mooney viscosity due to deterioration due to heating during drying, which effectively improves the normal tensile strength and elongation at break in the case of a rubber crosslinked product. It can be enhanced to. In addition, by blending the anti-aging agent in the state of the emulsion polymerization solution before coagulation, the anti-aging agent can be appropriately dispersed, so that even when the blending amount of the anti-aging agent is reduced, the anti-aging agent can be appropriately dispersed. The addition effect can be fully exerted. Specifically, the amount of the antiaging agent to be blended 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 solution. Even with a relatively small amount of compounding, the effect of addition can be fully exerted. Even if the anti-aging agent is contained in the emulsion polymerization solution before coagulation, the added anti-aging agent is not substantially removed in the subsequent coagulation, washing, drying, etc. , The addition effect can be fully exhibited. Further, as a method of containing an antiaging agent in the emulsion polymerization solution, a method of adding it to the emulsion polymerization solution after the emulsion polymerization and before the coagulation, or a method of adding it to the solution before the emulsion polymerization is performed. However, when it is added to the solution before the emulsion polymerization, agglomerates are generated during the emulsion polymerization, which may cause stains on the polymerization apparatus. Therefore, it is after the emulsion polymerization. Moreover, the method of adding to the emulsion polymerization solution before coagulation is preferable.

The antiaging agent is not particularly limited, but is 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butylphenol, butylhydroxyanisole, 2,6-di-t-butyl-. α-Dimethylamino-p-cresol, octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, styrenated phenol, 2,2'-methylene-bis (6-α-methyl- Benzyl-p-cresol), 4,4'-methylenebis (2,6-di-t-butylfunol), 2,2'-methylene-bis (4-methyl-6-t-butylphenol), 3- (3, 5-Di-tert-butyl-4-hydroxyphenyl) Phenolic antioxidants that do not contain sulfur atoms such as stearyl propionate, alkylated bisphenol, and butylation reaction products of p-cresol and dicyclopentadiene; 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) Phenolic thiophenolic anti-aging agents; Tris (nonylphenyl) ) Phenolic acid ester antiaging agents such as phosphite, diphenylisodecylphosphite, tetraphenyldipropylene glycol diphosphite; sulfur ester antiaging agents such as dilauryl thiodipropionate; phenyl-α-naphthylamine, phenyl-β -Naphtylamine, p- (p-toluenesulfonylamide) -diphenylamine, 4,4'-(α, α-dimethylbenzyl) diphenylamine, N, N-diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl- Amin-based antioxidants such as p-phenylenediamine, butylaldehyde-aniline condensates; imidazole-based antioxidants such as 2-mercaptobenzimidazole; 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinolin Kinolin-based anti-aging agents such as 2,5-di- (t-amyl) hydroquinone and other hydroquinone-based anti-aging agents; and the like. These anti-aging agents may be used alone or in combination of two or more.

Further, by preliminarily containing the lubricant in the emulsion polymerization solution before coagulation, the obtained acrylic rubber can be contained in a state in which the lubricant is well dispersed, and as a result, the obtained acrylic rubber can be contained. The adhesiveness of the acrylic rubber can be appropriately reduced, whereby adhesion to the dryer during drying can be prevented, operability during drying can be improved, and the obtained acrylic rubber can be obtained. It can be made excellent in roll workability. The amount of the lubricant added is preferably 0.1 to 0.4 parts by weight, more preferably 0.15 to 0.3 parts by weight, still more preferably 0, with respect to 100 parts by weight of the acrylic rubber component in the emulsion polymerization solution. .2 to 0.3 parts by weight. Even if the lubricant is contained in the emulsion polymerization solution before coagulation, the premixed lubricant is not substantially removed in the subsequent coagulation, washing, drying, etc., so that it is contained in the emulsion polymerization solution. Even when it is contained, the effect of its addition can be sufficiently exerted.

The lubricant is not particularly limited, and examples thereof include phosphoric acid ester, fatty acid ester, fatty acid amide, and higher fatty acid. Examples of the method of containing the lubricant in the emulsion polymerization solution include a method of adding the lubricant to the emulsion polymerization solution after the emulsion polymerization and before the solidification, and a method of adding the lubricant to the solution before the emulsion polymerization. Will be.

When an antioxidant and / or a lubricant is added to the emulsion polymerization solution before coagulation in addition to the ethylene oxide polymer, the order of addition is not particularly limited and may be appropriately selected.

<Coagulation process>
In the coagulation step in the production method of the present invention, the emulsion polymerization solution obtained by the emulsion polymerization step is adjusted to a temperature of 78 ° C. or higher, and a coagulant is added to the emulsion polymerization solution adjusted to a temperature of 78 ° C. or higher. This is the process of obtaining a water-containing crumb.

In the production method of the present invention, the ethylene oxide-based polymer is previously contained in the emulsion polymerization solution before coagulation, and in the presence of such an ethylene oxide-based polymer, at a temperature of 78 ° C. or higher. By coagulating, the amount of the coagulant in the coagulation step of the emulsion polymerization solution can be reduced, so that the residual amount of the coagulant in the finally obtained acrylic rubber can be reduced, and the rubber crosslinked product can be obtained. The water resistance can be further improved. If the coagulation temperature is too low, the coagulability of the emulsion polymerization solution will decrease, and the amount of coagulant required for coagulation will increase, resulting in the residual amount of coagulant in the finally obtained acrylic rubber. Will increase, and the water resistance will decrease when a rubber crosslinked product is used. In the production method of the present invention, the temperature (solidification temperature) of the emulsion polymerization liquid at the time of solidification is 78 ° C. or higher, preferably 79 ° C. or higher, and more preferably 80 ° C. or higher. Further, the upper limit of the temperature of the emulsion polymerization liquid at the time of coagulation is not particularly limited, but is usually 90 ° C. or lower.

The coagulant is not particularly limited, and examples thereof include monovalent to trivalent metal salts. The monovalent to trivalent metal salt is a salt containing a metal that becomes a 1 to trivalent metal ion when dissolved in water, and is not particularly limited, but is not particularly limited, but is an inorganic acid selected from, for example, hydrochloric acid, nitrate, sulfuric acid and the like. And salts of organic acids such as acetic acid and metals selected from sodium, potassium, lithium, magnesium, calcium, zinc, titanium, manganese, iron, cobalt, nickel, aluminum, tin and the like. Further, hydroxides of these metals and the like can also be used.

Specific examples of the 1- to trivalent metal salt include 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 chloride. Metal chlorides such as tin; Nitrate 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, tin nitrate; sodium sulfate , Potassium sulfate, lithium sulfate, magnesium sulfate, calcium sulfate, zinc sulfate, titanium sulfate, manganese sulfate, iron sulfate, cobalt sulfate, nickel sulfate, aluminum sulfate, sulfates such as tin sulfate; and the like. Among these, calcium chloride, sodium chloride, aluminum sulfate, magnesium chloride, magnesium sulfate, zinc chloride, zinc sulfate and sodium sulfate are preferable. Among them, monovalent or divalent metal salts are preferable, calcium chloride, sodium chloride, magnesium sulfate and sodium sulfate are more preferable, and magnesium sulfate or sodium sulfate is more preferable. In addition, these can be used alone or in combination of two or more.

The amount of the coagulant used can reduce the residual amount of the coagulant in the finally obtained acrylic rubber while sufficiently coagulating the acrylic rubber, whereby the rubber crosslinked product can be obtained. From the viewpoint of improving water resistance, preferably 1 to 100 parts by weight, more preferably 2 to 40 parts by weight, still more preferably 3 to 20 parts by weight, based on 100 parts by weight of the acrylic rubber component in the emulsion polymerization solution. Particularly preferably, it is 3 to 12 parts by weight.

<Washing process>
In the production method of the present invention, it is preferable that the water-containing crumb obtained in the above-mentioned solidification step is further provided with a washing step for washing.

The washing method is not particularly limited, and examples thereof include a method in which water is used as a washing liquid and water washing is performed by mixing the added water together with the water-containing crumb. 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.

The amount of water added to the water-containing crumb during washing with water 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 washing with water is preferably 50 to 9,800 parts by weight, more preferably 300 to 1,800 parts by weight with respect to 100 parts by weight of the solid content (mainly acrylic rubber component) contained in the water-containing crumb. It is a part by weight.

The number of washings 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 2 to 10 times, more preferably 3 to 8 times. 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 washings with water is large, but even if the washing is performed beyond the above range, the effect of removing the coagulant can be obtained. Although it is small, it is preferable that the number of washings with water is within the above range because the influence of the decrease in productivity becomes large due to the increase in the number of steps.

Further, in the production method of the present invention, after washing with water, pickling using an acid as a cleaning liquid may be further performed. By performing acid cleaning, it is possible to further enhance the compression set resistance in the case of a crosslinked rubber product, and when the acrylic rubber is a carboxyl group-containing acrylic rubber having a carboxyl group, this acid cleaning is performed. The effect of improving the compression resistance and permanent strain resistance is particularly large. The acid used for pickling is not particularly limited, and sulfuric acid, hydrochloric acid, phosphoric acid and the like can be used without limitation. Further, in pickling, when adding an acid to a hydrous crumb, it is preferable to add it in the state of an aqueous solution, preferably pH = 6 or less, more preferably pH = 4 or less, still more preferably pH = 3 or less. It is preferable to add it in the form of an aqueous solution. The method of pickling is not particularly limited, and examples thereof include a method of mixing an aqueous solution of the added acid together with the water-containing crumb.

The temperature during pickling 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 pickling is not particularly limited, but is preferably pH = 6 or less, more preferably pH = 4 or less, and even more preferably pH = 3 or less. The pH of the washing water for acid washing can be determined, for example, by measuring the pH of the water contained in the water-containing crumb after acid washing.

After the acid washing, it is preferable to further wash with water, and the conditions for washing with water may be the same as those described above.

<Drying process>
Further, in the production method of the present invention, it is preferable that the water-containing crumb that has been washed in the washing step is further provided with a drying step of drying.

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

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., 100. It is more preferable to set the temperature at about 170 ° C.

According to the production method of the present invention, acrylic rubber can be obtained as described above.

The Mooney viscosity (ML1 + 4, 100 ° C.) (polymer Mooney) of the acrylic rubber thus produced is preferably 10 to 80, more preferably 20 to 70, still more preferably 25 to 60.

Further, in the acrylic rubber produced by the production method of the present invention, the residual amount of the coagulant contained in the acrylic rubber is preferably 9,000 wt ppm or less, more preferably 7,000 wt ppm or less, and further. It is preferably 5,000 ppm by weight or less, and particularly preferably 3,500 ppm or less. The lower limit of the residual amount of the coagulant is not particularly limited, but is preferably 10% by weight or more. By setting the residual amount of the coagulant in the acrylic rubber within the above range, the water resistance in the case of a crosslinked rubber product can be made more excellent. The residual amount of the coagulant can be determined, for example, by performing elemental analysis on acrylic rubber and measuring the content of the element contained in the coagulant. The method for setting the residual amount of the coagulant to the above-mentioned amount is not particularly limited, but in addition to the method of performing coagulation in the coagulation step at a temperature of 78 ° C. or higher in the presence of an ethylene oxide polymer, coagulation is performed. Examples thereof include a method in which the amount of the agent added is within the above-mentioned range, and a method in which the washing conditions are adjusted as described above.

Further, in the acrylic rubber of the present invention, the residual amount of the emulsifier contained in the acrylic rubber is preferably 22,000% by weight or less, more preferably 20,000 by weight or less, still more preferably 18,000 by weight ppm. Hereinafter, it is particularly preferably 17,000 ppm by weight or less. The lower limit of the residual amount of the emulsifier is not particularly limited, but is preferably 10% by weight or more, more preferably 200% by weight or more, and further preferably 500% by weight or more. By setting the residual amount of the emulsifier in the acrylic rubber within the above range, the water resistance in the case of a crosslinked rubber product can be further enhanced. The residual amount of the emulsifier can be obtained from, for example, the peak area of the molecular weight corresponding to the emulsifier in the measurement chart obtained by GPC measurement on acrylic rubber. The method for setting the residual amount of the emulsifier to the above-mentioned amount is not particularly limited, but for example, as described above, a nonionic emulsifier and an anionic emulsifier are used in combination, and the addition amount thereof is described above. There is a method to make it within the range.

<Acrylic rubber composition>
The acrylic rubber composition of the present invention is obtained by blending a cross-linking agent with the acrylic rubber obtained by the above-mentioned production method of the present invention.

The cross-linking agent is not particularly limited, and is, for example, a polyvalent amine compound such as a diamine compound and a carbonate thereof; sulfur; a sulfur consortium; a triazinethiol compound; a polyvalent epoxy compound; an organocarboxylate ammonium salt; an organic peroxide. Conventionally known cross-linking agents such as oxides; dithiocarbamic acid metal salts; polyvalent carboxylic acids; quaternary onium salts; imidazole compounds; isocyanuric acid compounds; organic peroxides; can be used. These cross-linking agents can be used alone or in combination of two or more. The cross-linking agent is preferably appropriately selected depending on the type of the cross-linking monomer unit.

Among these, when the acrylic rubber produced by the production method of the present invention has α, β-ethylenically unsaturated carboxylic acid monomer unit as a crosslinkable monomer unit, it can be used as a crosslinking agent. It is preferable to use a polyvalent amine compound and a carbonate thereof.

The polyvalent amine compound and its carbonate are not particularly limited, but a polyvalent amine compound having 4 to 30 carbon atoms and a carbonate thereof are preferable. Examples of such polyvalent amine compounds and carbonates thereof include aliphatic polyvalent amine compounds, carbonates thereof, and aromatic polyvalent amine compounds.

The aliphatic polyvalent amine compound and a carbonate thereof are not particularly limited, and examples thereof include hexamethylenediamine, hexamethylenediamine carbamate, and N, N'-dicinnamylidene-1,6-hexanediamine. Among these, hexamethylenediamine carbamate is preferable.

The aromatic polyvalent amine compound is not particularly limited, and is, for example, 4,4'-methylenedianiline, p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether. , 4,4'-(m-phenylenediisopropyridene) dianiline, 4,4'-(p-phenylenediisopropyriden) dianiline, 2,2'-bis [4- (4-aminophenoxy) phenyl] propane, Included are 4,4'-diaminobenzanilide, 4,4'-bis (4-aminophenoxy) biphenyl, m-xylylenediamine, p-xylylenediamine, and 1,3,5-benzenetriamine. Among these, 2,2'-bis [4- (4-aminophenoxy) phenyl] propane is preferable.

The content of the cross-linking agent in the acrylic rubber composition of the present invention is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, and particularly preferably 0. 2 to 4 parts by weight. By setting the content of the cross-linking agent in the above range, the mechanical strength of the rubber cross-linked product can be made excellent while the rubber elasticity is sufficient.

Further, it is preferable that the acrylic rubber composition of the present invention further contains a cross-linking accelerator. The cross-linking accelerator is not particularly limited, but the acrylic rubber produced by the production method of the present invention has a carboxyl group as a cross-linking group, and the cross-linking agent is a polyvalent amine compound or a carbonic acid thereof. In the case of salts, guanidine compounds, diazabicycloalkene compounds, imidazole compounds, quaternary onium salts, tertiary phosphine compounds, aliphatic monovalent secondary amine compounds, aliphatic monovalent tertiary amine compounds, etc. Can be used. Among these, a guanidine compound, a diazabicycloalkene compound, and an aliphatic monovalent secondary amine compound are preferable, and a guanidine compound is particularly preferable. These basic cross-linking promoters can be used alone or in combination of two or more.

Specific examples of the guanidine compound include 1,3-di-o-tolylguanidine, 1,3-diphenylguanidine and the like. Specific examples of the diazabicycloalkene compound include 1,8-diazabicyclo [5.4.0] unde-7-sen, 1,5-diazabicyclo [4.3.0] no-5-nen and the like. .. Specific examples of the imidazole compound include 2-methylimidazole and 2-phenylimidazole. Specific examples of the quaternary onium salt include tetra n-butylammonium bromide and octadecyltri n-butylammonium bromide. Specific examples of the tertiary phosphine compound include triphenylphosphine and tri-p-tolylphosphine.

The aliphatic monovalent secondary amine compound is a compound in which two hydrogen atoms of ammonia are replaced with an aliphatic hydrocarbon group. The aliphatic hydrocarbon group that replaces the hydrogen atom is preferably one having 1 to 30 carbon atoms. Specific examples of the aliphatic monovalent secondary amine compound include dimethylamine, diethylamine, dipropylamine, diallylamine, diisopropylamine, di-n-butylamine, dit-butylamine, di-sec-butylamine, dihexylamine, and dihexylamine. Examples thereof include heptylamine, dioctylamine, dinonylamine, didecylamine, diundecylamine, didodecylamine, ditridecylamine, ditetradecylamine, dipentadecylamine, disetylamine, di-2-ethylhexylamine, and dioctadecylamine.

The aliphatic monovalent tertiary amine compound is a compound in which all three hydrogen atoms of ammonia are substituted with an aliphatic hydrocarbon group. The aliphatic hydrocarbon group that replaces the hydrogen atom is preferably one having 1 to 30 carbon atoms. Specific examples of the aliphatic monovalent tertiary amine compound include trimethylamine, triethylamine, tripropylamine, triallylamine, triisopropylamine, tri-n-butylamine, tri-t-butylamine, tri-sec-butylamine, and trihexylamine. , Triheptylamine, Trioctylamine, Trinonylamine, Tridecylamine, Triundecylamine, Tridodecylamine and the like.

The content of the crosslinking accelerator in the acrylic rubber composition of the present invention is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 7.5 parts by weight, based on 100 parts by weight of the acrylic rubber. Parts, particularly preferably 1 to 5 parts by weight. By setting the content of the cross-linking accelerator in the above range, the tensile strength and the compression set resistance of the obtained rubber cross-linked product can be further improved.

In addition to the above components, the acrylic rubber composition of the present invention can contain a compounding agent usually used in the rubber processing field. Examples of such compounding agents include reinforcing fillers such as silica and carbon black; non-reinforcing fillers such as calcium carbonate and clay; antiaging agents; light stabilizers; anti-scorch agents; plasticizers; processing aids. Agents; adhesives; lubricants; lubricants; flame retardants; fungicides; antistatic agents; colorants; crosslink retardants; and the like. The blending amount of these blending agents is not particularly limited as long as the purpose and effect of the present invention are not impaired, and an amount suitable for the blending purpose can be appropriately blended.

Further, the acrylic rubber composition of the present invention may be further blended with a rubber, an elastomer, a resin or the like other than the acrylic rubber of the present invention as long as the effects of the present invention are not impaired. For example, rubbers other than acrylic rubber such as acrylic rubber, natural rubber, polybutadiene rubber, polyisoprene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, silicon rubber, fluororubber, etc. other than the acrylic rubber of the present invention described above; olefin-based Elastomers such as elastomers, styrene-based elastomers, vinyl chloride-based elastomers, polyester-based elastomers, polyamide-based elastomers, polyurethane-based elastomers, and polysiloxane-based elastomers; polyolefin-based resins, polystyrene-based resins, polyacrylic resins, polyphenylene ether-based resins, polyesters. Resins such as based resins, polycarbonate resins, polyamide resins, vinyl chloride resins, and fluororesins; and the like can be blended. The total amount of the rubber, elastomer, and resin other than the acrylic rubber of the present invention described above is preferably 50 parts by weight or less, more preferably 10 parts by weight or less, still more preferably 10 parts by weight, based on 100 parts by weight of the acrylic rubber. It is 1 part by weight or less.

In the acrylic rubber composition of the present invention, a cross-linking agent and other various compounding agents used as necessary are mixed with acrylic rubber, mixed and kneaded with a Banbury mixer, a kneader, or the like, and then a kneading roll is used. It is prepared by further kneading.

The blending order of each component is not particularly limited, but after sufficiently mixing the components that are difficult to react or decompose by heat, the cross-linking agent, which is a component that easily reacts or decomposes by heat, is mixed at a temperature at which reaction or decomposition does not occur. It is preferable to mix in a short time.

<Rubber cross-linked product>
The rubber crosslinked product of the present invention is obtained by cross-linking the acrylic rubber composition of the present invention described above.
The rubber crosslinked product of the present invention is formed by using the acrylic rubber composition of the present invention with a molding machine corresponding to a desired shape, for example, an extruder, an injection molding machine, a compressor, a roll, or the like, and is heated. It can be manufactured by carrying out a cross-linking reaction and fixing the shape as a rubber cross-linked product. In this case, cross-linking may be performed after molding in advance, or cross-linking may be performed at the same time as molding. The molding temperature is usually 10 to 200 ° C, preferably 25 to 120 ° C. The crosslinking temperature is usually 130 to 220 ° C., preferably 150 to 190 ° C., and the crosslinking time is usually 2 minutes to 10 hours, preferably 3 minutes to 5 hours. As the heating method, a method used for cross-linking rubber such as press heating, steam heating, oven heating, and hot air heating may be appropriately selected.

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

Since the rubber crosslinked product of the present invention thus obtained is obtained by using the acrylic rubber obtained by the above-mentioned production method of the present invention, it has excellent water resistance. Therefore, the rubber crosslinked product of the present invention makes use of such characteristics to seal O-rings, packings, oil seals, bearing seals, etc. in a wide range of fields such as transportation machines such as automobiles, general equipment, and electrical equipment. Materials; Gaskets; Buffering materials, Anti-vibration materials; Wire coating materials; Industrial belts; Tubes / hoses; Sheets; etc.

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

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

[Residual amount of coagulant]
The residual amount of the coagulant in the acrylic rubber was measured by performing elemental analysis on the acrylic rubber using (ICP-AES). Specifically, the content ratio of the element contained in the coagulant used was obtained by elemental analysis, and the residual amount of the coagulant was calculated from the obtained content ratio.

[Tensile strength, elongation]
The acrylic rubber composition was placed in a mold having a length of 15 cm, a width of 15 cm, and a depth of 0.2 cm, and was first crosslinked by pressing at 170 ° C. for 20 minutes while pressurizing at a press pressure of 10 MPa, and then the obtained primary crosslink was obtained. The material was further heated in a gear oven at 170 ° C. for 4 hours for secondary cross-linking to obtain a sheet-shaped rubber cross-linked product. The obtained rubber crosslinked product was punched out with a No. 3 dumbbell to prepare a test piece. Next, using this test piece, tensile strength and elongation were measured according to JIS K6251.

[water resistant]
The acrylic rubber composition was placed in a mold having a length of 15 cm, a width of 15 cm, and a depth of 0.2 cm, and was first crosslinked by pressing at 170 ° C. for 20 minutes while pressurizing at a press pressure of 10 MPa, and then the obtained primary crosslink was obtained. The material was further heated in a gear oven at 170 ° C. for 4 hours for secondary cross-linking to obtain a sheet-shaped rubber cross-linked product. Then, the obtained sheet-shaped rubber crosslinked product was cut into 3 cm × 2 cm × 0.2 cm test pieces, and the obtained test pieces were placed in distilled water adjusted to a temperature of 80 ° C. for 70 hours in accordance with JIS K6258. A dipping test for dipping was performed, and the volume change rate of the test piece before and after dipping was measured according to the following formula. It can be judged that the smaller the volume change rate before and after immersion, the more the swelling with water is suppressed, and the better the water resistance.
Volume change rate before and after immersion (%) = (Volume of test piece after immersion-Volume of test piece before immersion) ÷ Volume of test piece before immersion × 100

[Manufacturing Example 1]
46.294 parts of pure water, 49.3 parts of ethyl acrylate, 49.3 parts of n-butyl acrylate, 1.4 parts of mono-n-butyl fumarate, anionic surfactant in a mixing container equipped with a homomixer. Sodium lauryl sulfate (trade name "Emar 2FG", manufactured by Kao Co., Ltd.) 0.567 parts, and polyoxyethylene dodecyl ether as a nonionic surfactant (trade name "Emargen 105", weight average molecular weight: about 1500, Kao Co., Ltd.) 1.4 parts were charged and stirred to obtain a monomeric emulsion.

Next, 170.853 parts of pure water and 2.97 parts of the monomer emulsion obtained above were put into a polymerization reaction tank equipped with a thermometer and a stirrer, and the temperature was 12 ° C. under a nitrogen stream. Cooled down to. Next, in the polymerization reaction tank, 145.29 parts of the monomer emulsion obtained above, 0.00033 part of ferrous sulfate as a reducing agent, 0.264 parts of sodium ascorbate as a reducing agent, and. 7.72 parts of a 2.85 wt% potassium persulfate aqueous solution as a polymerization initiator (0.22 parts as the amount of potassium persulfate) was continuously added dropwise over 3 hours. After that, the reaction was continued for 1 hour while the temperature in the polymerization reaction tank was kept at 23 ° C., it was confirmed that the polymerization conversion rate reached 95%, and hydroquinone as a polymerization terminator was added for polymerization. The reaction was stopped to obtain an emulsion polymerization solution.

Then, polyethylene oxide (weight average molecular weight (Mw) = 100,000, weight average molecular weight is measured using GPC in a DMF solvent containing 10 mmol LiBr) with respect to 100 parts of the emulsion polymerization solution obtained by polymerization) 0. 0.11 part (that is, the total of ethyl acrylate, n-butyl acrylate, and mono-butyl fumarate) of 100 parts of the charged monomers used in producing the emulsion polymerization solution was 0. 039 parts), stearyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate as an antioxidant (trade name "Irganox 1076", manufactured by BASF) 0.3 parts (emulsion polymerization solution) (1 part for a total of 100 parts of the charged monomer used in the production), and polyoxyethylene stearyl ether phosphate as a lubricant (trade name “Phosphanol RL-210”, weight average molecular weight: Approximately 500, manufactured by Toho Kagaku Kogyo Co., Ltd.) 0.075 parts (0.25 parts for a total of 100 parts of the charged monomers used in producing the emulsion polymerization liquid) are mixed to obtain a mixed liquid. rice field. Then, the obtained mixed liquid is transferred to a coagulation tank, 60 parts of industrial water is added to 100 parts of this mixed liquid, the temperature is raised to 80 ° C., and then the mixed liquid is stirred at a temperature of 80 ° C. However, by continuously adding 3.3 parts of sodium sulfate as a coagulant (11 parts with respect to 100 parts of the polymer contained in the mixed solution), the polymer was coagulated and then filtered and thereby acrylic. A hydrous crumb of rubber (A1) was obtained.

Next, 388 parts of industrial water was added to 100 parts of the solid content of the water-containing crumb obtained above, 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 contain water. The crumb was washed with water. In this production example, such washing with water was repeated 4 times.

Next, a sulfuric acid aqueous solution (pH = 3) consisting of a mixture of 388 parts of industrial water and 0.13 parts of concentrated sulfuric acid was added to 100 parts of the solid content of the water-containing crumb washed with water above, and in the coagulation tank. After stirring at room temperature for 5 minutes, the water-containing crumb was pickled by draining water from the coagulation tank. When the pH of the water-containing crumb after pickling (pH of the water in the water-containing crumb) was measured, the pH was 3. Next, 388 parts of pure water was added to 100 parts of the solid content of the water-containing crumb that had been 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 discharge the water-containing crumb. The water-containing crumb that had been washed with pure water was dried at 110 ° C. for 1 hour with a hot air dryer to obtain a solid acrylic rubber (A1).

The obtained acrylic rubber (A1) has a Mooney viscosity (ML1 + 4, 100 ° C.) of 33, and the composition of the acrylic rubber (A1) is 49.3% by weight of ethyl acrylate and 49.3 by weight of n-butyl acrylate. By weight%, mono-n-butyl fumarate unit was 1.4% by weight. Further, with respect to the acrylic rubber (A1), the residual amount of the coagulant in the acrylic rubber (A1) was measured according to the above method. The results are shown in Table 1.

[Manufacturing Example 2]
Using the emulsion polymerization solution obtained in the same manner as in Production Example 1, the mixed solution obtained by mixing an antiaging agent, polyethylene oxide, and a lubricant in the same manner as in Production Example 1 was subjected to coagulation. A water-containing crumb of acrylic rubber (A2) was obtained by performing a solidification operation in the same manner as in Production Example 1 except that the temperature of the mixed solution was set to 85 ° C.

Next, the water-containing crumb of the obtained acrylic rubber (A2) was washed with water, pickled, pure water, and dried with a hot air dryer four times in the same manner as in Production Example 1, to obtain a solid acrylic rubber. (A2) was obtained. The obtained acrylic rubber (A2) has a Mooney viscosity (ML1 + 4, 100 ° C.) of 33, and the composition of the acrylic rubber (A2) is 49.3% by weight of ethyl acrylate and 49.3 by weight of n-butyl acrylate. By weight%, mono-n-butyl fumarate unit was 1.4% by weight. Further, the residual amount of the coagulant in the acrylic rubber (A2) was measured according to the above method. The results are shown in Table 1.

[Manufacturing Example 3]
Using the emulsion polymerization solution obtained in the same manner as in Production Example 1, the mixed solution obtained by mixing an antiaging agent, polyethylene oxide, and a lubricant in the same manner as in Production Example 1 was subjected to coagulation. A water-containing crumb of acrylic rubber (A3) was obtained by performing a solidification operation in the same manner as in Production Example 1 except that the temperature of the mixed solution was 90 ° C.

Next, the water-containing crumb of the obtained acrylic rubber (A3) was washed with water, pickled, pure water, and dried with a hot air dryer four times in the same manner as in Production Example 1, to obtain a solid acrylic rubber. (A3) was obtained. The obtained acrylic rubber (A3) has a Mooney viscosity (ML1 + 4, 100 ° C.) of 33, and the composition of the acrylic rubber (A3) is 49.3% by weight of ethyl acrylate and 49.3 by weight of n-butyl acrylate. By weight%, mono-n-butyl fumarate unit was 1.4% by weight. Further, the residual amount of the coagulant in the acrylic rubber (A3) was measured according to the above method. The results are shown in Table 1.

[Manufacturing Example 4]
In a mixing vessel equipped with a homomixer, 46.294 parts of pure water, 49.3 parts of ethyl acrylate, 49.3 parts of n-butyl acrylate, 1.4 parts of mono-n-butyl fumarate, anionic surfactant. Sodium lauryl sulfate (trade name "Emar 2FG", manufactured by Kao) 0.567 parts, polyoxyethylene dodecyl ether as a nonionic surfactant (trade name "Emargen 105", manufactured by Kao) 1.4 parts , And polyethylene oxide (weight average molecular weight (Mw) = 100,000) were charged and stirred to obtain a monomeric emulsion.

Next, 170.853 parts of pure water and 2.97 parts of the monomer emulsion obtained above were put into a polymerization reaction tank equipped with a thermometer and a stirrer, and the temperature was 12 ° C. under a nitrogen stream. Cooled down to. Next, 145.32 parts of the monomer emulsion obtained above, 0.00033 part of ferrous sulfate as a reducing agent, 0.264 parts of sodium ascorbate as a reducing agent, and 0.264 parts of sodium ascorbate as a reducing agent were placed in the polymerization reaction tank. 7.72 parts of a 2.85 wt% potassium persulfate aqueous solution as a polymerization initiator (0.22 parts as the amount of potassium persulfate) was continuously added dropwise over 3 hours. After that, the reaction was continued for 1 hour while the temperature in the polymerization reaction tank was kept at 23 ° C., it was confirmed that the polymerization conversion rate reached 95%, and hydroquinone as a polymerization terminator was added for polymerization. The reaction was stopped to obtain an emulsion polymerization solution.

Then, with respect to 100 parts of the emulsion polymerization solution obtained by the polymerization, stearyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate (trade name "Irganox 1076", BASF) as an antiaging agent was added. 0.3 parts (1 part for a total of 100 parts of the prepared monomer used in producing the emulsion polymerization solution) and polyoxyethylene stearyl ether phosphate as a lubricant (trade name "Foss") Fanol RL-210 ”, manufactured by Toho Kagaku Kogyo Co., Ltd.) By mixing 0.075 parts (0.25 parts for a total of 100 parts of the charged monomers used in producing the emulsion polymerization solution). A mixture was obtained. Then, the water-containing crumb of acrylic rubber (A4) was formed by performing a coagulation operation on the obtained mixed liquid in the same manner as in Production Example 1 except that the temperature of the mixed liquid at the time of coagulation was set to 85 ° C. Obtained.

Next, the water-containing crumb of the obtained acrylic rubber (A4) was washed with water, pickled, pure water, and dried with a hot air dryer four times in the same manner as in Production Example 1, to obtain a solid acrylic rubber. (A4) was obtained. The obtained acrylic rubber (A4) has a Mooney viscosity (ML1 + 4, 100 ° C.) of 33, and the composition of the acrylic rubber (A4) is 49.3% by weight of ethyl acrylate and 49.3 by weight of n-butyl acrylate. By weight%, mono-n-butyl fumarate unit was 1.4% by weight. Further, the residual amount of the coagulant in the acrylic rubber (A4) was measured according to the above method. The results are shown in Table 1.

[Manufacturing Example 5]
Using the emulsion polymerization solution obtained in the same manner as in Production Example 1, the emulsion polymerization solution obtained in the same manner as in Production Example 1 was mixed in the same manner as in Production Example 1 except that polyethylene oxide was not mixed. A liquid was obtained, and the temperature of the mixed liquid at the time of coagulation was set to 85 ° C. and the amount of sodium sulfate as a coagulant was 10 parts (100 parts of the polymer contained in the mixed liquid) with respect to the obtained mixed liquid. A water-containing crumb of acrylic rubber (A5) was obtained by performing a solidification operation in the same manner as in Production Example 1 except that the amount was 33.3 parts).

Next, the water-containing crumb of the obtained acrylic rubber (A5) was washed with water, pickled, pure water, and dried with a hot air dryer four times in the same manner as in Production Example 1, to obtain a solid acrylic rubber. (A5) was obtained. The obtained acrylic rubber (A5) has a Mooney viscosity (ML1 + 4, 100 ° C.) of 33, and the composition of the acrylic rubber (A5) is 49.3% by weight of ethyl acrylate and 49.3 by weight of n-butyl acrylate. By weight%, mono-n-butyl fumarate unit was 1.4% by weight. Further, the residual amount of the coagulant in the acrylic rubber (A5) was measured according to the above method. The results are shown in Table 1.

[Manufacturing Example 6]
Using the emulsion polymerization solution obtained in the same manner as in Production Example 1, the emulsion polymerization solution obtained in the same manner as in Production Example 1 was replaced with 0.011 part of polyethylene oxide, and polyoxyethylene dodecyl ether (trade name). "Emulgen 105", weight average molecular weight: about 1500, compound in which a dodecyl group is bonded to a polyoxyethylene structure, manufactured by Kao Co., Ltd.) 0.011 part (monomer used for producing an emulsion polymerization solution) A mixed solution was obtained in the same manner as in Production Example 1 except that 0.039 parts were used for a total of 100 parts, and the temperature of the mixed solution at the time of solidification was 85 ° C. with respect to the obtained mixed solution. The coagulation operation is carried out in the same manner as in Production Example 1 except that the amount of sodium sulfate as a coagulant is 10 parts (33.3 parts with respect to 100 parts of the polymer contained in the mixed solution). As a result, a water-containing crumb of acrylic rubber (A6) was obtained.

Next, the water-containing crumb of the obtained acrylic rubber (A6) was washed with water, pickled, pure water, and dried with a hot air dryer four times in the same manner as in Production Example 1, to obtain a solid acrylic rubber. (A6) was obtained. The obtained acrylic rubber (A6) has a Mooney viscosity (ML1 + 4, 100 ° C.) of 34, and the composition of the acrylic rubber (A6) is 49.3% by weight of ethyl acrylate and 49.3 by weight of n-butyl acrylate. By weight%, mono-n-butyl fumarate unit was 1.4% by weight. Further, the residual amount of the coagulant in the acrylic rubber (A6) was measured according to the above method. The results are shown in Table 1.

[Example 1]
Using a Banbury mixer, 100 parts of acrylic rubber (A1) obtained in Production Example 1, 30 parts of clay (trade name "Satinton Clay 5A", manufactured by Takehara Chemical Industry Co., Ltd., fired kaolin), silica (trade name "" Carplex 1120 ", 15 parts manufactured by Evonik, silica (trade name" Carplex 67 ", manufactured by Evonik) 35 parts, 2 parts stearate, 4,4'-bis (α, α-dimethylbenzyl) diphenylamine ( 2 parts of product name "Nocrack CD", manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., and 1 part of 3-methacryloxypropyltrimethoxysilane (trade name "KBM-503", manufactured by Shinetsu Silicone Co., Ltd.) It was added and mixed at 50 ° C. for 5 minutes. The resulting mixture was then transferred to a roll at 50 ° C. to 0.6 parts of hexamethylenediamine carbamate (trade name "Diak # 1", manufactured by DuPontau Elastomer, aliphatic polyvalent amine compound), and 1,3. An acrylic rubber composition was obtained by blending two parts of -o-tolylguanidine (trade name "Noxeller DT", manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., a cross-linking accelerator) and kneading them.

Then, using the obtained acrylic rubber composition, each measurement / evaluation of tensile strength, elongation, and water resistance was performed according to the above method. The results are shown in Table 2.

[Examples 2 to 4]
Acrylic in the same manner as in Example 1 except that the acrylic rubbers (A2) to (A4) obtained in Production Examples 2 to 4 were used instead of the acrylic rubber (A1) obtained in Production Example 1. Table 2 shows the results of measuring and evaluating the rubber composition in the same manner.

[Comparative Examples 1 and 2]
Acrylic in the same manner as in Example 1 except that the acrylic rubbers (A5) and (A6) obtained in Production Examples 5 and 6 were used instead of the acrylic rubber (A1) obtained in Production Example 1. Table 2 shows the results of measuring and evaluating the rubber composition in the same manner.

（＊１）単量体乳化液作製のための配合剤の添加量は、仕込み単量体１００部に対する配合量で示した。
（＊２）凝固前の乳化重合液に添加した配合剤の添加量は、乳化重合液１００部に対する配合量で示した。
（＊３）凝固工程で使用した凝固剤の添加量は、乳化重合液に、老化防止剤、ポリエチレンオキシド、および／または滑剤を添加することにより得られた混合液１００部に対する配合量で示した。

(* 1) The amount of the compounding agent added for preparing the monomer emulsion is shown as the compounding amount with respect to 100 parts of the charged monomer.
(* 2) The amount of the compounding agent added to the emulsion polymerization solution before coagulation is shown as the amount to be added to 100 parts of the emulsion polymerization solution.
(* 3) The amount of the coagulant added in the coagulant step is shown as the blending amount with respect to 100 parts of the mixed solution obtained by adding the antiaging agent, polyethylene oxide, and / or the lubricant to the emulsion polymerization solution. ..

As shown in Tables 1 and 2, Production Examples 1 to 1 to which ethylene oxide-based polymer was added to the emulsion polymerization solution before solidification and solidification was performed at a temperature of 78 ° C. or higher in the presence of the ethylene oxide-based polymer. The rubber crosslinked product obtained by using the acrylic rubber obtained in No. 4 was excellent in water resistance (Production Examples 1 to 4, Examples 1 to 4).

On the other hand, the acrylic obtained by Production Example 7 in which the ethylene oxide-based polymer was not added to the emulsion polymerization solution before solidification and Production Example 8 in which polyoxyethylene dodecyl ether was used instead of the ethylene oxide-based polymer. Similarly, the rubber crosslinked product obtained by using rubber was also inferior in water resistance (Production Examples 5 and 6, Comparative Examples 1 and 2).

Claims (10)

A method for producing acrylic rubber having a Mooney viscosity (ML1 + 4, 100 ° C.) of 10 to 80.
An emulsion polymerization step of obtaining an emulsion polymerization solution by emulsion polymerization of a monomer for forming the acrylic rubber, and an emulsion polymerization step.
An ethylene oxide-based polymer addition step of adding an ethylene oxide-based polymer to the emulsion polymerization solution before solidification, and a step of adding the ethylene oxide-based polymer.
A coagulation step of obtaining a water-containing crumb by coagulating the emulsion polymerization solution with a coagulant is provided .
A method for producing acrylic rubber in which the ethylene oxide-based polymer is an ethylene oxide homopolymer . The method for producing acrylic rubber according to claim 1, wherein the acrylic rubber contains a crosslinkable monomer unit. The method for producing acrylic rubber according to claim 2, wherein the acrylic rubber contains an α, β-ethylenically unsaturated carboxylic acid monomer unit as the crosslinkable monomer unit. The method for producing acrylic rubber according to claim 2 or 3, wherein the content of the crosslinkable monomer unit in the acrylic rubber is 0.1 to 10% by weight. The method for producing acrylic rubber according to any one of claims 1 to 4, wherein the ethylene oxide-based polymer has a weight average molecular weight of 10,000 to 200,000. Claim 1 to the addition amount of the ethylene oxide-based polymer in the ethylene oxide-based polymer addition step is 0.005 to 1 part by weight with respect to 100 parts by weight of the monomer for forming the acrylic rubber. 5. The method for producing acrylic rubber according to any one of 5. The method for producing acrylic rubber according to any one of claims 1 to 6 , wherein the monomer is emulsion-polymerized in the presence of a nonionic emulsifier and an anionic emulsifier. The method for producing acrylic rubber according to claim 7 , wherein the amount of the nonionic emulsifier and the anionic emulsifier used is 50/50 to 75/25 in terms of the weight ratio of the nonionic emulsifier / the anionic emulsifier. In the emulsion polymerization step, the emulsion polymerization reaction is carried out while continuously dropping the monomer, the polymerization initiator and the reducing agent for forming the acrylic rubber into the polymerization reaction system from the start of the polymerization reaction to an arbitrary time. The method for producing acrylic rubber according to any one of claims 1 to 8 . The monomer for forming the acrylic rubber is continuously added dropwise to the polymerization reaction system from the start of the polymerization reaction to an arbitrary time in the state of a monomer emulsion formed by mixing an emulsifier and water. The method for producing acrylic rubber according to claim 9 , wherein the emulsion polymerization reaction is carried out.