Method of producing acrylic rubber

Abstract

To provide a method of producing an acrylic rubber excellent in storage stability.SOLUTION: A method of producing an acrylic rubber includes: an emulsion polymerization process of polymerizing a monomer in emulsion to obtain an emulsion polymerization liquid; a coagulation process of coagulating the emulsion polymerization liquid by a coagulant to obtain a hydrous crumb; and a drying process of drying the hydrous crumb, where a base process for adding a base is included in processes after the emulsion polymerization process, and an amount of a base used for the ester compound is adjusted until the base process when using an ester compound other than a monomer constituting an acrylic rubber.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing an acrylic rubber, and more specifically, to a method for producing an acrylic rubber having excellent storage stability. [Background technology]

[0002] Acrylic rubber is a polymer whose main component is an acrylic ester, and is generally known as a rubber having excellent heat resistance, oil resistance, and ozone resistance, and is widely used in the automotive industry.

[0003] Such acrylic rubber is usually obtained by emulsion polymerizing a monomer mixture constituting the acrylic rubber, adding a coagulant to the obtained emulsion polymerization liquid, and drying the obtained water-containing crumbs.

[0004] In the method of producing acrylic rubber, the production conditions for each step are investigated, and Patent Document 1 discloses that by adjusting the residual calcium concentration and pH of the polymer, the resulting cross-linked acrylic rubber has excellent physical properties. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO2018 / 147142 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the inventors of the present invention have confirmed that the storage stability of acrylic rubber varies depending on the manufacturing method used. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a manufacturing method for acrylic rubber having excellent storage stability. [Means for solving the problem]

[0007] As a result of intensive research into achieving the above-mentioned object, the present inventors have discovered that in a method for producing acrylic rubber which includes an emulsion polymerization step of emulsion-polymerizing monomers to obtain an emulsion polymerization liquid, a coagulation step of coagulating the emulsion polymerization liquid with a coagulant to obtain water-containing crumbs, and a drying step of drying the water-containing crumbs, an acrylic rubber which has excellent storage stability can be produced by including a base step in the steps following the emulsion polymerization step, and by adjusting the amount of base used when an ester compound other than the monomers that constitute the acrylic rubber is used up until the base step, this has led to the completion of the present invention.

[0008] The aspects of the present invention are as follows. Item 1. An emulsion polymerization step of obtaining an emulsion polymerization liquid by emulsion polymerization of a monomer; A coagulation step of coagulating the emulsion polymerization liquid with a coagulant to obtain a water-containing crumb; Drying process to dry the moist crumbs Including, Furthermore, the method includes a base step of adding a base in a step subsequent to the emulsion polymerization step, Ester compounds other than the monomers that make up acrylic rubber are used up to the base step. When the amount of base used in the base step is X parts by mass relative to 100 parts by mass of the ester compound, the molecular weight of the base used is Y, and the valence of the base used is Z, 0.15≦(X / Y) / Z≦2.5 A manufacturing method for acrylic rubber that satisfies the above requirements. Item 2. The method for producing an acrylic rubber according to Item 1, wherein the ester compound is a phosphate ester compound and / or a sulfate ester compound. Item 3. A method for producing an acrylic rubber-containing composition, further comprising a step of blending a crosslinking agent with the acrylic rubber obtained by the method for producing an acrylic rubber according to item 1 or 2. Item 4. A method for producing an acrylic rubber cross-linked product, further comprising a step of cross-linking the acrylic rubber composition obtained by the method for producing an acrylic rubber-containing composition according to item 3. Effect of the Invention

[0009] The present invention is a method for producing an acrylic rubber having excellent storage stability. Since the acrylic rubber obtained by the production method of the present invention has excellent storage stability, even if it is stored for a long period of time, the processability does not deteriorate significantly, and scorch (crosslinking before the crosslinking step) can be prevented. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The acrylic rubber produced by the production method of the present invention is a polymer mainly composed of structural units derived from (meth)acrylic acid ester. Here, the term "main component" refers to a polymer containing 50% by mass or more of structural units derived from (meth)acrylic acid ester. Note that "(meth)acrylic acid ester" means "acrylic acid ester or methacrylic acid ester", and the same applies to similar expressions in the present application.

[0011] Examples of the structural unit derived from the (meth)acrylic acid ester include a structural unit derived from an alkyl (meth)acrylic acid ester and a structural unit derived from an alkoxyalkyl (meth)acrylic acid ester. The structural unit derived from the (meth)acrylic acid ester is preferably a structural unit derived from an alkyl (meth)acrylic acid ester having an alkyl group having 1 to 8 carbon atoms, or a structural unit derived from an alkoxyalkyl (meth)acrylic acid ester having an alkoxyalkyl group having 2 to 8 carbon atoms, more preferably a structural unit derived from an alkyl (meth)acrylic acid ester having an alkyl group having 2 to 6 carbon atoms and / or a structural unit derived from an alkoxyalkyl (meth)acrylic acid ester having an alkoxyalkyl group having 2 to 6 carbon atoms, and particularly preferably a structural unit derived from an alkyl (meth)acrylic acid ester having an alkyl group having 2 to 4 carbon atoms and / or a structural unit derived from an alkoxyalkyl (meth)acrylic acid ester having an alkoxyalkyl group having 2 to 4 carbon atoms. The structural unit derived from the (meth)acrylic acid ester may be a single structural unit or two or more structural units derived from a (meth)acrylic acid ester.

[0012] Specific examples of (meth)acrylic acid alkyl esters include (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate, of which ethyl (meth)acrylate and n-butyl (meth)acrylate are preferred. Specific examples of the (meth)acrylic acid alkoxyalkyl ester include (meth)acrylic acid esters such as methoxymethyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-methoxypropyl (meth)acrylate, 2-ethoxypropyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, and 4-ethoxybutyl (meth)acrylate, with methoxyethyl (meth)acrylate being preferred.

[0013] In the acrylic rubber of the present invention, the content of structural units derived from (meth)acrylic acid ester in all structural units of the acrylic rubber is more preferably 50 mass% or more, and particularly preferably 60 mass% or more, and the upper limit is preferably 99.5 mass% or less, more preferably 99 mass% or less, and particularly preferably 98.5 mass% or less.

[0014] The acrylic rubber of the present invention contains a structural unit derived from an unsaturated monomer having a crosslinking group. Examples of the structural unit derived from an unsaturated monomer having a crosslinking group include a structural unit derived from an unsaturated monomer having a halogen group (e.g., a chlorine group), a structural unit derived from an unsaturated monomer having a carboxyl group, and a structural unit derived from an unsaturated monomer having an epoxy group, and the structural unit derived from an unsaturated monomer having a halogen group (especially a chlorine group) or a carboxyl group is particularly preferred.

[0015] Examples of the unsaturated monomer having a halogen group include vinyl monochloroacetate and allyl chloroacetate, with vinyl monochloroacetate being preferred.

[0016] Examples of the unsaturated monomer having a carboxy group include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, 2-pentenoic acid, and cinnamic acid, unsaturated dicarboxylic acids such as fumaric acid, maleic acid, and itaconic acid, carboxylic anhydrides such as maleic anhydride and citraconic anhydride, butenedioic acid mono-chain alkyl esters such as monomethyl fumarate, monoethyl fumarate, mono-n-butyl fumarate, monomethyl maleate, monoethyl maleate, mono-2-ethylhexyl maleate, and mono-n-butyl maleate, butenedioic acid mono-cyclic alkyl esters such as monocyclopentyl fumarate, monocyclohexyl fumarate, monocyclopentyl maleate, and monocyclohexyl maleate, and itaconic acid monoesters such as monomethyl itaconate, monoethyl itaconate, mono-n-butyl itaconate, and monocyclohexyl itaconate. Among these, there may be mentioned unsaturated dicarboxylic acid monoesters such as monoethyl fumarate, monopropyl fumarate, monobutyl fumarate, monoethyl itaconate, monopropyl itaconate, and monobutyl itaconate.

[0017] Examples of the unsaturated monomer having an epoxy group include glycidyl (meth)acrylate and (meth)allyl glycidyl ether.

[0018] The content of the structural units derived from unsaturated monomers having a crosslinking group in the acrylic rubber is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, particularly preferably 0.5% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, particularly preferably 2.5% by mass or less, based on the total structural units of the acrylic rubber. The above range of the structural units derived from unsaturated monomers having a crosslinking group is preferable in terms of physical properties such as strength and compression set, and processability.

[0019] Furthermore, the acrylic rubber of the present invention may contain, in addition to the above-mentioned structural units, structural units derived from other monomers copolymerizable therewith. Examples of the other structural units include structural units derived from ethylenically unsaturated nitriles, structural units derived from (meth)acrylamide monomers, structural units derived from aromatic vinyl monomers, structural units derived from conjugated diene monomers, structural units derived from non-conjugated dienes, structural units derived from other olefins, etc.

[0020] Examples of the ethylenically unsaturated nitrile include compounds such as acrylonitrile, methacrylonitrile, α-methoxyacrylonitrile, and vinylidene cyanide.

[0021] Examples of the (meth)acrylamide monomer include acrylamide, methacrylamide, diacetone acrylamide, diacetone methacrylamide, N-butoxymethyl acrylamide, N-butoxymethyl methacrylamide, N-butoxyethyl acrylamide, N-butoxyethyl methacrylamide, N-methoxymethyl acrylamide, N-methoxymethyl methacrylamide, N-propioxymethyl acrylamide, N-propioxymethyl methacrylamide, N-methyl acrylamide, N-methyl methacrylamide, N,N-dimethyl acrylamide, N,N-dimethyl methacrylamide, N,N-diethyl acrylamide, N,N-diethyl methacrylamide, N-methylolacrylamide, N-methylol methacrylamide, ethacrylamide, crotonamide, cinnamic acid amide, maleindiamide, itacondiamide, methylmaleamide, methyl itaconamide, maleimide, itaconimide, and other compounds.

[0022] Examples of aromatic vinyl monomers include compounds such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, o-ethylstyrene, p-ethylstyrene, α-fluorostyrene, p-trifluoromethylstyrene, p-methoxystyrene, p-aminostyrene, p-dimethylaminostyrene, p-acetoxystyrene, styrenesulfonic acid or a salt thereof, α-vinylnaphthalene, 1-vinylnaphthalene-4-sulfonic acid or a salt thereof, 2-vinylfluorene, 2-vinylpyridine, 4-vinylpyridine, divinylbenzene, diisopropenylbenzene, and vinylbenzyl chloride.

[0023] Examples of conjugated diene monomers include compounds such as 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,2-dichloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-neopentyl-1,3-butadiene, 2-bromo-1,3-butadiene, 2-cyano-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, chloroprene, and piperylene.

[0024] Examples of structural units derived from non-conjugated dienes include structural units derived from non-conjugated diene compounds such as 1,4-pentadiene, 1,4-hexadiene, ethylidenenorbornene, norbornadiene, and dicyclopentadiene.

[0025] Other olefin monomers include esters such as dicyclopentadienyl acrylate, dicyclopentadienyl methacrylate, dicyclopentadienyl ethyl acrylate, and dicyclopentadienyl ethyl methacrylate, as well as compounds such as ethylene, propylene, vinyl chloride, vinylidene chloride, 1,2-dichloroethylene, vinyl acetate, vinyl fluoride, vinylidene fluoride, 1,2-difluoroethylene, vinyl bromide, vinylidene bromide, 1,2-dibromoethylene, ethyl vinyl ether, and butyl vinyl ether.

[0026] In the acrylic rubber of the present invention, when structural units derived from these other copolymerizable monomers are contained, the content in all structural units is preferably 0 to 45% by mass, more preferably 0 to 20% by mass.

[0027] The method for producing acrylic rubber of the present invention includes an emulsion polymerization step of obtaining an emulsion polymerization liquid by emulsion polymerizing monomers, a coagulation step of coagulating the emulsion polymerization liquid with a coagulant to obtain water-containing crumbs, and a drying step of drying the water-containing crumbs. It also includes a base step of adding a base in the steps following the emulsion polymerization step, and an ester compound other than the monomers that constitute the acrylic rubber is used (added) before the base step.

[0028] The process for obtaining an emulsion polymerization liquid by emulsion polymerization of monomers will be described below. Hereinafter, this process may also be referred to as an emulsion polymerization process.

[0029] The emulsion polymerization step is a step of obtaining an emulsion polymerization liquid by emulsion-polymerizing monomers that will constitute the acrylic rubber.

[0030] In the emulsion polymerization step, a conventional method may be used, and the emulsifier, polymerization initiator, chain transfer agent, polymerization terminator and the like may be any of the conventionally known agents that are generally used.

[0031] The emulsifier is not particularly limited, and nonionic emulsifiers and anionic emulsifiers that are generally used in emulsion polymerization methods can be used. Examples of nonionic emulsifiers include polyoxyethylene alkyl ethers, polyoxyethylene alcohol ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene polycyclic phenyl ethers, polyoxyalkylene alkyl ethers, sorbitan fatty acid esters, polyoxyethylene fatty acid esters, and polyoxyethylene sorbitan fatty acid esters. Examples of anionic emulsifiers include alkylbenzene sulfonates, alkyl sulfates, polyoxyethylene alkyl ether sulfates, polyoxyalkylene alkyl ether phosphates or their salts, polyoxyalkylene alkyl phenyl ether phosphates or their salts, and fatty acid salts such as sodium lauryl sulfate. These may be used alone or in combination. Examples of salts include alkali metals such as sodium and potassium, ammonia, and amines.

[0032] The amount of the emulsifier used may be an amount generally used in emulsion polymerization. Specifically, it is in the range of 0.01 to 10% by mass, preferably 0.03 to 7% by mass, and more preferably 0.05 to 5% by mass, based on the amount of the charged monomer. When a reactive surfactant is used as the monomer component, the addition of an emulsifier is not necessarily required.

[0033] The polymerization initiator is not particularly limited, and a polymerization initiator generally used in emulsion polymerization can be used. Specific examples thereof include inorganic polymerization initiators such as persulfates, such as potassium persulfate, sodium persulfate, and ammonium persulfate, 2,2-di(4,4-di(t-butylperoxy)cyclohexyl)propane, 1-di(t-hexylperoxy)cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 4,4-di(t-butylperoxy)n-butyl valerate, 2,2-di(t-butylperoxy)butane, t-butyl hydroperoxide, and cumene hydroperoxide. Side, diisopropylbenzene hydroperoxide, p-menthane hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, t-butylcumyl peroxide, di-t-butyl peroxide, di-t-hexyl peroxide, di(2-t-butylperoxyisopropyl)benzene, dicumyl peroxide, diisobutyryl peroxide, di(3,5,5-trimethylhexanoyl) peroxide, dilauroyl peroxide, disuccinic acid peroxide peroxydicarbonate, dibenzoyl peroxide, di(3-methylbenzoyl) peroxide, benzoyl(3-methylbenzoyl) peroxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(4-t-butylcyclohexyl) peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate, di-sec-butyl peroxydicarbonate, cumyl peroxyneodecanate, 1,1,3,3-tetramethylbutyl peroxyneodecanate Canate, t-hexylperoxyneodecanate, t-butylperoxyneodecanate, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanate, t-hexylperoxy-2-ethylhexanate, t-butylperoxy-2-ethylhexanate, t-butylperoxylaurate, t-butylperoxy-3,5,Polymerization initiators of organic peroxides such as 5-trimethylhexanate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy2-ethylhexyl monocarbonate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxyacetate, t-hexylperoxybenzoate, t-butylperoxybenzoate, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, hydroperoxides, azobisisobutyronitrile, 4-4'-azobis(4- Examples of the azo initiator include 2-2'-azobis[2-(2-imidazolin-2-yl)propane, 2-2'-azobis(propane-2-carboxamidine), 2-2'-azobis[N-(2-carboxyethyl)-2-methylpropanamide, 2-2'-azobis[2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane], 2-2'-azobis(1-imino-1-pyrrolidino-2-methylpropane) and 2-2'-azobis[2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propanamide]. These polymerization initiators may be used alone or in combination of two or more.

[0034] The amount of the polymerization initiator used may be any amount generally used in emulsion polymerization, specifically, in the range of 0.01 to 5% by mass, preferably 0.01 to 4% by mass, and more preferably 0.02 to 3% by mass, based on the amount of the charged monomer.

[0035] In addition, the organic peroxide and inorganic peroxide as the polymerization initiator can be used as a redox polymerization initiator by combining with a reducing agent. The reducing agent to be used in combination is not particularly limited, but includes compounds containing metal ions in a reduced state such as ferrous sulfate and cuprous naphthenate, methane compounds such as sodium formaldehyde sulfoxylate and sodium methanesulfonate, amine compounds such as dimethylaniline, ascorbic acid and its salts, and inorganic salts having reducing properties such as alkali metal salts of sulfurous acid and thiosulfuric acid. 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 10.0 parts by mass relative to 100 parts by mass of the charged monomer.

[0036] Chain transfer agents can be used as necessary. Specific examples of chain transfer agents include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-stearyl mercaptan, xanthogen compounds such as 2,4-diphenyl-4-methyl-1-pentene, 2,4-diphenyl-4-methyl-2-pentene, dimethyl xanthogen disulfide, and diisopropyl xanthogen disulfide, terpinolene, tetramethylthiuram disulfide, tetraethylthiuram disulfide, and tetramethylthiuram monosulfide. Thiuram compounds, phenolic compounds such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol, allyl compounds such as allyl alcohol, halogenated hydrocarbon compounds such as dichloromethane, dibromomethane and carbon tetrabromide, vinyl ethers such as α-benzyloxystyrene, α-benzyloxyacrylonitrile and α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexyl thioglycolate, etc., may be used alone or in combination. The amount of these chain transfer agents is not particularly limited, but is usually 0 to 5 parts by mass per 100 parts by mass of the charged monomer.

[0037] Examples of the polymerization terminator include hydroxylamine, hydroxylamine sulfate, diethylhydroxyamine, hydroxylamine sulfonic acid and its alkali metal salts, sodium dimethyldithiocarbamate, and quinone compounds such as hydroquinone. The amount of the polymerization terminator used is not particularly limited, but is usually 0 to 2 parts by mass relative to 100 parts by mass of the total monomers.

[0038] In addition, polymerization secondary materials such as particle size regulators, chelating agents, and oxygen scavengers can be used as necessary.

[0039] The emulsion polymerization may be any of batch, semi-batch, and continuous. The polymerization time and temperature are not particularly limited. They can be appropriately selected depending on the type of polymerization initiator used, but generally, the polymerization temperature is 10 to 100°C, and the polymerization time is 0.5 to 100 hours.

[0040] The process of coagulating the emulsion polymerization liquid with a coagulant to obtain water-containing crumbs will be described below. Hereinafter, this process may also be referred to as the coagulation process.

[0041] The coagulant used in the coagulation step is not particularly limited, but is preferably an inorganic metal salt, specific examples of which include sodium sulfate, magnesium sulfate, aluminum sulfate, sodium chloride, and calcium chloride.

[0042] The method of coagulation by coagulant is not particularly limited, and a commonly used method can be adopted. One example of the method is to continuously or batchwise supply the emulsion polymerization liquid to an aqueous solution containing a coagulant, and this operation produces a water-containing crumb. At that time, the temperature of the aqueous solution containing the coagulant is affected by the type and amount of monomer used, shear force due to stirring, etc., so it cannot be uniformly specified, but is generally 50°C or higher, preferably in the range of 60°C to 100°C.

[0043] In the present invention, the method may include a step of washing the obtained wet crumbs with water. Hereinafter, this step may be referred to as a water washing step. The purpose of the water washing step is to remove the coagulant contained in the wet crumbs.

[0044] In the present invention, a step of drying the hydrous crumb is included. Hereinafter, this step may also be referred to as a drying step.

[0045] The acrylic rubber can be obtained by removing the water from the hydrous crumb and drying it. The drying method is not particularly limited, but it is generally dried using a flash dryer or a fluidized bed dryer.

[0046] The drying temperature is not particularly limited, but is preferably from 50° C. to 250° C., and more preferably from 80 to 200° C. The drying time varies depending on the drying temperature.

[0047] Before the drying step, a dehydration step using a centrifuge or the like may be performed.

[0048] In the production method of the present invention, a base step of adding a base is included in the steps subsequent to the emulsion polymerization step, and an ester compound other than the monomers constituting the acrylic rubber is used before the base step.

[0049] Examples of the ester compound other than the monomer constituting the acrylic rubber include a phosphoric acid ester compound and a sulfuric acid ester compound. Note that since the ester compound other than the monomer constituting the acrylic rubber does not constitute the acrylic rubber, it does not have a (meth)acryloyl group.

[0050] The phosphate ester compound includes alkyl ether phosphate ester, alkyl phosphate ester, and salts thereof.

[0051] Examples of alkyl ether phosphates and salts thereof include polyoxyalkylene alkyl ether phosphates such as polyoxyalkylene 2-ethylhexyl ether phosphate, polyoxyalkylene stearyl ether phosphate, polyoxyalkylene myristyl ether phosphate, polyoxyalkylene lauryl ether phosphate, polyoxyalkylene palmityl ether phosphate, polyoxyalkylene oleyl ether phosphate, polyoxyalkylene tridecyl ether phosphate, etc. Examples of polyoxyalkylenes include polyoxyethylene and polyoxypropylene, and examples of their salts include alkali metals such as sodium and potassium, ammonia, and amines.

[0052] The alkyl phosphate ester and its salt are preferably a mono- or di-alkyl phosphate ester having 12 to 24 carbon atoms and its salt, and a mono- or di-alkyl phosphate ester having 16 to 18 carbon atoms and its salt. Specific examples include stearyl phosphate ester, myristyl phosphate ester, lauryl phosphate ester, palmityl phosphate ester, etc., and examples of the salts thereof include alkali metals such as sodium and potassium, ammonia, and amines.

[0053] Examples of the sulfate compound include alkyl ether sulfate, alkyl sulfate, and salts thereof.

[0054] Examples of alkyl ether sulfates and salts thereof include polyoxyalkylene stearyl ether sulfates, polyoxyalkylene myristyl ether sulfates, polyoxyalkylene lauryl ether sulfates, polyoxyalkylene palmityl ether sulfates, etc. Examples of polyoxyalkylenes include polyoxyethylene, polyoxypropylene, etc., and examples of their salts include alkali metals such as sodium and potassium, ammonia, amines, etc.

[0055] The alkyl sulfate and salts thereof are preferably mono- or di-alkyl sulfates and salts thereof having 12 to 24 carbon atoms, and mono- or di-alkyl sulfates and salts thereof having 16 to 18 carbon atoms. Specific examples include stearyl sulfate, myristyl sulfate, lauryl sulfate, palmityl sulfate, etc., and salts thereof include alkali metals such as sodium and potassium, ammonia, and amines.

[0056] The ester compound other than the monomers constituting the acrylic rubber may be used up to the base step, specifically, may be used in the emulsion polymerization step, the coagulation step, the water-washing step, and further between the emulsion polymerization step, the coagulation step, and the water-washing step.

[0057] In the production method of the present invention, the ester compound may function as an emulsifier in the emulsion polymerization step, a lubricant for improving workability after drying, or the like, and is not particularly limited in the purpose of use. The ester compound is preferably used as an emulsifier in the emulsion polymerization step.

[0058] In the process subsequent to the emulsion polymerization process, the base step in which a base is added satisfies 0.15≦(X / Y) / Z≦2.5, where the amount of base used in the base step is X parts by mass relative to 100 parts by mass of the ester compound other than the monomers constituting the acrylic rubber, the molecular weight of the base used is Y, and the valence of the base used is (Z).

[0059] Examples of the base used in the base step include hydroxide compounds such as sodium hydroxide, potassium hydroxide, calcium hydroxide, etc., carbonate compounds such as sodium hydrogen carbonate, potassium carbonate, etc., ammonia, inorganic ammonium compounds, organic amine compounds such as triethylamine, etc., and sodium hydrogen carbonate and sodium hydroxide are preferable. Note that the base is blended mainly for the purpose of neutralizing the ester that is hydrolyzed during the production process of the acrylic rubber, rather than acting directly on the ester compound.

[0060] In the present invention, when the amount of base used in the base step is X parts by mass relative to 100 parts by mass of the ester compound other than the monomers constituting the acrylic rubber, the molecular weight of the base used is Y, and the valence of the base used is (Z), it is preferable to satisfy 0.15≦(X / Y) / Z≦2.5, more preferably to satisfy 0.18≦(X / Y) / Z≦2.3, and even more preferably to satisfy 0.18≦(X / Y) / Z≦1.5.

[0061] The base step is carried out after the emulsion polymerization step, and is not particularly limited as long as it is after the ester compound is used, but it is preferably carried out before the drying step or the dehydration step carried out before the drying step, and may be carried out after the coagulation step.

[0062] The molecular weight range of the acrylic rubber used in the present invention thus produced is set to be within the Mooney viscosity (ML) at 100°C in the Mooney scorch test specified in JIS K 6300 from the viewpoint of processability. 1+4 ) is preferably 10 to 100, more preferably 15 to 90, and even more preferably 20 to 80.

[0063] <Acrylic rubber-containing composition> The acrylic rubber-containing composition of the present invention contains at least the above-mentioned acrylic rubber and a crosslinking agent.

[0064] As the crosslinking agent, a conventionally known crosslinking agent such as a polyamine compound, a polyepoxy compound, a polyisocyanate compound, an aziridine compound, a sulfur compound, a higher fatty acid metal salt (fatty acid metal soap), or a thiol compound can be used.

[0065] Examples of higher fatty acid metal salts include alkali metal salts or alkaline earth metal salts of fatty acids having an alkyl or alkenyl group with 8 to 18 carbon atoms, such as sodium stearate, potassium stearate, potassium myristate, sodium palmitate, calcium stearate, magnesium stearate, sodium oleate, potassium oleate, and barium oleate, and these may be used alone or in combination.

[0066] Examples of the polyamine compound include aliphatic polyamine compounds such as hexamethylenediamine, hexamethylenediamine carbamate, and N,N'-dicinnamylidene-1,6-hexanediamine, and aromatic polyamine compounds such as 4,4'-methylenedianiline, m-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-(m-phenylenediisopropylidene)dianiline, 4,4'-(p-phenylenediisopropylidene)dianiline, 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminobenzanilide, 4,4'-bis(4-aminophenoxy)biphenyl, m-xylylenediamine, p-xylylenediamine, 1,3,5-benzenetriamine, 1,3,5-benzenetriaminomethyl, and isophthalic acid dihydrazide.

[0067] Examples of polyfunctional epoxy compounds include glycidyl ether type epoxy compounds such as phenol novolac type epoxy compounds, cresol novolac type epoxy compounds, cresol type epoxy compounds, bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, brominated bisphenol A type epoxy compounds, brominated bisphenol F type epoxy compounds, and hydrogenated bisphenol A type epoxy compounds; and other polyfunctional epoxy compounds such as alicyclic epoxy compounds, glycidyl ester type epoxy compounds, glycidyl amine type epoxy compounds, and isocyanurate type epoxy compounds.

[0068] Examples of polyisocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, 1,5-naphthylene diisocyanate, 1,3,6-hexamethylene triisocyanate, 1,6,11-undecane triisocyanate, and bicycloheptane triisocyanate.

[0069] Examples of the aziridine compound include tris-2,4,6-(1-aziridinyl)-1,3,5-triazine, tris[1-(2-methyl)aziridinyl]phosphinoxide, and hexa[1-(2-methyl)aziridinyl]triphosphatriazine.

[0070] Examples of the sulfur compound include sulfur, 4,4'-dithiomorpholine, tetramethylthiuram disulfide, and tetraethylthiuram disulfide.

[0071] Examples of the thiol compound include 1,3,5-triazinedithiol or a derivative thereof, and 1,3,5-triazinetrithiols such as 1,3,5-triazine-2,4,6-trithiol.

[0072] These crosslinking agents may be used alone or in combination of two or more. The amount of each crosslinking agent is 0.05 to 20 parts by mass, preferably 0.1 to 10 parts by mass, per 100 parts by mass of the acrylic rubber of the present invention.

[0073] The acrylic rubber-containing composition of the present invention may also contain any of other additives commonly used in the art, such as a lubricant, an antioxidant, a light stabilizer, a filler, a reinforcing agent, a plasticizer, a processing aid, a pigment, a colorant, a crosslinking accelerator, a crosslinking auxiliary, a crosslinking retarder, an antistatic agent, and a foaming agent.

[0074] Examples of the antioxidant include amines, phosphates, quinolines, cresols, phenols, and dithiocarbamate metal salts. Preferred are amines such as diphenylamine derivatives such as 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, and phenylenediamine derivatives.

[0075] Examples of the crosslinking accelerator include guanidine compounds, amine compounds, thiourea compounds, thiazole compounds, sulfenamide compounds, thiuram compounds, and quaternary ammonium salts, with guanidine compounds and amine compounds being preferred.

[0076] Furthermore, it is possible to blend with rubber, resin, etc., as is commonly done in the technical field, without departing from the spirit of the present invention. Examples of rubbers used in the present invention include butadiene rubber, styrene-butadiene rubber, isoprene rubber, natural rubber, acrylonitrile-butadiene rubber, acrylonitrile-butadiene-isoprene rubber, ethylene-propylene-diene rubber, epichlorohydrin rubber, etc., and examples of resins include PMMA (polymethyl methacrylate) resin, PS (polystyrene) resin, PUR (polyurethane) resin, PVC (polyvinyl chloride) resin, EVA (ethylene / vinyl acetate) resin, AS (styrene / acrylonitrile) resin, PE (polyethylene) resin, etc.

[0077] The total amount of the rubber and resin is 50 parts by mass or less, preferably 10 parts by mass or less, and more preferably 1 part by mass or less, per 100 parts by mass of the acrylic rubber of the present invention.

[0078] The method for producing an acrylic rubber-containing composition of the present invention includes a step of blending a crosslinking agent with the acrylic rubber obtained by the above-mentioned method for producing an acrylic rubber.

[0079] The acrylic rubber-containing composition of the present invention can be compounded using any method conventionally used in the field of polymer processing, such as an open roll, a Banbury mixer, or various kneaders.

[0080] The compounding procedure can be the usual procedure used in the field of polymer processing. For example, the polymer alone is first kneaded, then compounding ingredients other than the crosslinking agent and crosslinking accelerator are added to prepare compound A, and then compound B is kneaded by adding the crosslinking agent and crosslinking accelerator.

[0081] The cross-linked acrylic rubber product is obtained by cross-linking the acrylic rubber-containing composition, and the method for producing the cross-linked acrylic rubber product includes a step of cross-linking the acrylic rubber-containing composition obtained by the above-mentioned method for producing the acrylic rubber-containing composition.

[0082] In the process of crosslinking the acrylic rubber-containing composition, the acrylic rubber-containing composition can be usually heated to 100 to 250°C to form a crosslinked product. The crosslinking time varies depending on the temperature, but is usually performed between 0.5 and 300 minutes. The crosslinking molding may be performed in a single step of crosslinking and molding, or the previously molded acrylic rubber-containing composition may be heated again to form a crosslinked product, or the crosslinked product may be heated first and then processed for molding. As a specific method for crosslinking molding, any method such as compression molding using a mold, injection molding, heating using a steam can, air bath, infrared rays, or microwaves may be used.

[0083] Therefore, taking advantage of the above-mentioned properties, the crosslinked product of the present invention can be suitably used as various gaskets, such as O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, mechanical seals, wellhead seals, seals for electric and electronic devices, seals for pneumatic devices, cylinder head gaskets attached to the joint between a cylinder block and a cylinder head, rocker cover gaskets attached to the joint between a rocker cover and a cylinder head, oil pan gaskets attached to the joint between an oil pan and a cylinder block or a transmission case, gaskets for fuel cell separators attached between a pair of housings sandwiching a unit cell having a positive electrode, an electrolyte plate, and a negative electrode, and gaskets for the top covers of hard disk drives.

[0084] The crosslinked product of the present invention can be used as a rubber material, and is suitably used as an extrusion molded product and a mold crosslinked product for automobile applications, such as various hoses, including fuel oil hoses around fuel tanks, such as fuel hoses, filler neck hoses, vent hoses, vapor hoses, and oil hoses, air hoses, such as turbo air hoses and emission control hoses, radiator hoses, heater hoses, brake hoses, and air conditioner hoses. EXAMPLES

[0085] The present invention will be specifically described with reference to examples and comparative examples, although the present invention is not limited thereto. In the examples and comparative examples, the production of acrylic rubber, and the physical properties of an acrylic-rubber-containing composition containing the obtained acrylic rubber and a crosslinking agent, and a rubber material (specifically, a crosslinked product obtained by crosslinking) prepared using the acrylic-rubber-containing composition were evaluated.

[0086] (Production of emulsion polymerization liquid A) A polymerization reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a pressure reducing device was charged with 150 parts by mass of water, 1.2 parts by mass of polyoxyethylene 2-ethylhexyl ether phosphate sodium salt as an ester compound, 98.0 parts by mass of ethyl acrylate as a monomer, and 2.0 parts by mass of vinyl monochloroacetate, and oxygen was sufficiently removed by repeatedly degassing under reduced pressure and replacing with nitrogen, after which 0.12 part by mass of sodium formaldehyde sulfoxylate and 0.1 part by mass of cumene hydroperoxide were added to initiate an emulsion polymerization reaction under normal pressure and temperature, and the reaction was continued until the polymerization conversion rate reached 95%, thereby obtaining an emulsion polymerization liquid A.

[0087] (Production of emulsion polymerization liquid B) Except for changing the monomers and their amounts to 48.0 parts by mass of ethyl acrylate, 25.0 parts by mass of n-butyl acrylate, 25.0 parts by mass of 2-methoxyethyl acrylate, and 2.0 parts by mass of vinyl monochloroacetate, the same procedure as in the production of emulsion polymerization liquid A was carried out to obtain emulsion polymerization liquid B. The polymerization conversion rate at this time was 99%.

[0088] (Production of emulsion polymerization liquid C) Except for changing the emulsifier to 0.42 parts by mass of sodium lauryl sulfate (i.e., sodium salt of lauryl sulfate ester) and 0.6 parts by mass of polyoxyethylene alkyl ether as the ester compound, the same procedure as in the production of emulsion polymerization liquid B was carried out to obtain emulsion polymerization liquid C. The polymerization conversion rate at this time was 99%.

[0089] Next, the emulsion polymerization liquid is used to produce an acrylic rubber through a coagulation process and a drying process. If a base process is further included, the value of (X / Y) / Z is also described, where the amount of base used in the base process is X parts by mass, the molecular weight of the base used is Y, and the valence of the base used is (Z) for 100 parts by mass of the ester compound other than the monomer that constitutes the acrylic rubber.

[0090] [Example 1] (Manufacture of acrylic rubber A) 100 parts by mass of water and 6 parts by mass of sodium sulfate were added to a beaker and heated to 90° C. Next, 100 parts by mass of emulsion polymerization liquid A was dropped to coagulate the polymer and obtain hydrous crumbs, after which 0.24 parts by mass of sodium bicarbonate was added as a base, and the polymer was then washed twice with 250 parts by mass of water and dried at 85° C. for 16 hours to obtain acrylic rubber A. Here, the value of (X / Y) / Z was 0.60.

[0091] [Example 2] (Manufacture of acrylic rubber B) Except for changing the base to 0.36 parts by mass of a 10% by weight aqueous solution of sodium hydroxide, this was produced in the same manner as acrylic rubber A. Here, the value of (X / Y) / Z was 0.19.

[0092] [Example 3] (Manufacture of acrylic rubber C) Except for changing the base to 0.36 parts by mass of sodium bicarbonate, this was produced in the same manner as acrylic rubber A. Here, the value of (X / Y) / Z was 0.89.

[0093] [Example 4] (Manufacture of acrylic rubber D) It was produced in the same manner as acrylic rubber A, except that the emulsion polymerization liquid was changed to emulsion polymerization liquid B. Here, the value of (X / Y) / Z was 0.60.

[0094] [Example 5] (Manufacture of Acrylic Rubber E) Except for changing to 3.6 parts by mass of 10% by weight sodium hydroxide, this was produced in the same manner as acrylic rubber D. Here, the value of (X / Y) / Z was 1.88.

[0095] [Example 6] (Manufacture of Acrylic Rubber F) Except for changing the emulsion polymerization liquid to emulsion polymerization liquid C and changing the amount of sodium hydrogen carbonate to 0.24 parts by mass, this was produced in the same manner as acrylic rubber A. Here, the value of (X / Y) / Z was 2.27.

[0096] (Manufacture of acrylic rubber G) [Comparative Example 1] It was produced in the same manner as Acrylic Rubber A, except that no base was added.

[0097] (Manufacture of Acrylic Rubber H) [Comparative Example 2] It was prepared in the same manner as Acrylic Rubber D, except that no base was added.

[0098] (Manufacture of Acrylic Rubber I) [Comparative Example 3] It was produced in the same manner as Acrylic Rubber F, except that no base was added.

[0099] [Comparative Example 4] (Manufacture of acrylic rubber J) Except for changing the amount of sodium hydrogen carbonate to 0.04 parts by mass, this was produced in the same manner as acrylic rubber D. Here, the value of (X / Y) / Z was 0.10.

[0100] [Comparative Example 5] (Manufacture of Acrylic Rubber K) Except for changing the amount of sodium hydrogen carbonate to 1.21 parts by mass, this was produced in the same manner as acrylic rubber D. Here, the value of (X / Y) / Z was 3.00.

[0101] (Method for promoting storage of acrylic rubber) Each of the produced acrylic rubbers was stored for 7 days in a thermohygrostat (PR-3K, manufactured by Espec Corp.) adjusted to an atmosphere of 80°C and 75% humidity. After that, each acrylic rubber was taken out and thoroughly dried.

[0102] (Evaluation method for storage stability) According to the formulation in the table, acrylic rubber compositions were produced by kneading acrylic rubber without accelerated storage and acrylic rubber after accelerated storage, and the physical properties of the compositions with and without accelerated storage were compared.

[0103] (Production of Acrylic Rubber Composition) First, the compounding ingredients shown in Table 1 were kneaded in a kneader at 100°C to prepare compound A. Compound A was then kneaded in an open roll at room temperature to prepare compound B. In the table, A indicates the raw material of compound A, and B indicates the raw material to be mixed with compound A when compound B is prepared. The units for the compounding ingredients in Table 1 are parts by mass. 4,4'-bis(α,α-dimethylbenzyl)diphenylamine was used as the anti-aging agent.

[0104] (Preparation of uncrosslinked sheet) Each of the acrylic copolymer-containing compositions obtained above was kneaded using a kneader and an open roll to prepare an uncrosslinked sheet having a thickness of 2 to 2.5 mm.

[0105] (Mooney Scorch Exam) The uncrosslinked sheet thus obtained was subjected to the Mooney scorch test defined in JIS K 6300-1 at 125° C. using a Mooney Viscometer AM-3 manufactured by Toyo Seiki Co., Ltd. The results are shown in Table 1.

[0106] (Preparation of secondary cross-linked product) The uncrosslinked rubber sheet obtained above was pressed at 180℃ for 10 minutes to obtain a 2mm-thick primary crosslinked product, which was then heated in an air oven at 180℃ for 3 hours to obtain a secondary crosslinked product.

[0107] (Normal physical property test) The obtained secondary cross-linked product was subjected to a tensile test and a hardness test. The tensile test was performed according to the method specified in JIS K 6251, and the hardness test was performed according to the method specified in JIS K 6253.

[0108] The test results of the examples and comparative examples obtained by each test method are shown in Table 1. In each table, the minimum Mooney value Vm and t5 refer to the minimum Mooney viscosity and Mooney scorch time (scorch time (t5)) defined in the Mooney scorch test of JIS K6300-1. 100M, tensile strength, and elongation refer to the tensile stress, tensile strength, and elongation at 100% elongation defined in the tensile test of JIS K6251, and hardness refers to the hardness defined in the hardness test of JIS K6253. The results are shown in Table 1.

[0109] [Table 1]

[0110] Table 1 shows that the acrylic rubbers of the Examples obtained by the manufacturing method of the present invention have excellent storage stability, with the scorch time (t5) being maintained (10 minutes or more) and the minimum Mooney value changing little in both the acrylic rubber without accelerated storage and the acrylic rubber after accelerated storage. On the other hand, the acrylic rubbers of the Comparative Examples either had a shorter scorch time (t5) (less than 10 minutes) or the minimum Mooney value changed significantly, indicating that they had inferior storage stability compared to the acrylic rubbers of the Examples. [Industrial Applicability]

[0111] The acrylic rubber obtained by the method for producing acrylic rubber of the present invention has excellent storage stability, and a rubber material (specifically, a cross-linked product obtained by cross-linking) produced using a composition containing the obtained acrylic rubber has excellent heat resistance and oil resistance, and is therefore suitable as a rubber material for various components for automobiles, such as sealing materials, hose materials, vibration-proof materials, tube materials, belt materials, and boots materials.

Claims

1. an emulsion polymerization step of obtaining an emulsion polymerization liquid by emulsion polymerization of monomers; A coagulation step of coagulating the emulsion polymerization liquid with a coagulant to obtain a water-containing crumb; Drying process to dry the moist crumbs Including, Furthermore, the method includes a base step of adding a base in a step subsequent to the emulsion polymerization step, An ester compound other than the monomer constituting the acrylic rubber is used up to the base step, When the amount of the base used in the base step is X parts by mass relative to 100 parts by mass of the ester compound, the molecular weight of the base used is Y, and the valence of the base used is Z, 0.15≦(X / Y) / Z≦2.5 A manufacturing method for acrylic rubber that satisfies the above requirements.

2. The method for producing an acrylic rubber according to claim 1, wherein the ester compound is a phosphate compound and / or a sulfate compound.

3. A method for producing an acrylic rubber-containing composition, further comprising a step of blending a crosslinking agent with the acrylic rubber obtained by the method for producing an acrylic rubber according to claim 1 or 2.

4. A method for producing a cross-linked acrylic rubber product, further comprising a step of cross-linking the acrylic rubber composition obtained by the method for producing an acrylic rubber-containing composition according to claim 3.

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