JP2022162559A - Acrylic copolymer and crosslinked product thereof - Google Patents

Abstract

To provide: a crosslinked product of an acrylic copolymer for producing a rubber material which has an excellent balance between oil resistance and cold resistance, and in particular has excellent acid resistance; an acrylic copolymer for obtaining the crosslinked product; and a composition containing the acrylic copolymer.SOLUTION: The present invention pertains to an acrylic copolymer which contains 18-28 mass% of structural units derived from methacrylates (however, structural units derived from methyl methacrylates are less than 10 mass%) and 0.5-5 mass% of structural units derived from crosslinkable monomers having carboxy groups. The present invention further pertains to an acrylic copolymer-containing composition which contains the aforementioned copolymer and a crosslinking agent, and to a crosslinked product thereof.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to an acrylic copolymer and its crosslinked product, and more particularly, an acrylic copolymer capable of providing a rubber material excellent in cold resistance, oil resistance, and acid resistance, and a rubber material made from the acrylic copolymer. is. Hereinafter, the material composed of the crosslinked product may be referred to as "rubber material" or "crosslinked rubber material".

In general, acrylic polymers are polymers whose main raw material is acrylic acid ester, and are known as materials with excellent properties related to durability. It is widely used as a rubber material for automobiles.

In recent years, the thermal environmental conditions around internal combustion engines have become more severe due to the increase in output of internal combustion engines and exhaust gas measures, etc., and deterioration due to contact with heat, air, moisture, additives, etc. of engine oil has become more severe than ever. Therefore, there is a demand for further improvement in the performance of rubber parts that can withstand degraded engine oil.

As an example of improving hydrolysis resistance while maintaining a balance between oil resistance and cold resistance against such a situation, Patent Document 1 discloses alkyl acrylate, methyl methacrylate at a specific ratio, and cross-linking at a specific ratio. An acrylic rubber copolymerized with a site monomer is disclosed.

JP 2016-27155 A

The acrylic rubber obtained by copolymerizing a specific proportion of methyl methacrylate and a specific proportion of a crosslinking site monomer disclosed in Patent Document 1 does not have sufficient acid resistance. Therefore, the present invention provides a crosslinked product of an acrylic copolymer to give a rubber material having an excellent balance between oil resistance and cold resistance, and particularly excellent acid resistance, an acrylic copolymer for that purpose, and an acrylic copolymer. The object is to provide a composition.

（一般式（Ｉ）中、Ｒ_１はメチル基、Ｒ₂はアルキル基、アルコキシル基のいずれかである。） As a result of various investigations, the present inventors have found that the structural unit derived from the methacrylic acid ester represented by the following general formula (I) is 18 to 28% by mass (however, the structural unit derived from methyl methacrylate is less than 10% by mass. ), an acrylic copolymer containing 0.5 to 5% by mass of structural units derived from a crosslinkable monomer having a carboxyl group, an acrylic copolymer containing the above copolymer and a crosslinking agent The present inventors have completed the present invention based on the finding that the above objects can be achieved by a composition containing coalescence and a crosslinked product thereof.

(In general formula (I), _R1 is a methyl group, and _R2 is either an alkyl group or an alkoxyl group.)

（一般式（Ｉ）中、Ｒ_１はメチル基、Ｒ₂はアルキル基、アルコキシル基のいずれかである。）
項２ 下記の条件（ｉ）～（ｉｉ）を満たす項１記載のアクリル共重合体。
（ｉ）前記（Ｉ）に示されるメタクリル酸エステルに由来する構成単位を含有する共重合体のＦｅｄｏｒｓ法による溶解パラメータ（ＳＰ値）が９．８以上である。
（ｉｉ）前記（Ｉ）に示されるメタクリル酸エステルに由来する構成単位を含有する共重合体のＦｏｘの式により求められるガラス転移温度（Ｔｇ）が－２５℃以下である。
項３ 炭素数１～８のアルキル基を有するアクリル酸アルキルエステルに由来する構成単位、および/または炭素数２～８のアルコキシアルキル基を有するアクリル酸アルコキシアルキルエステルに由来する構成単位２０～８１.９質量％を含有する項１又は２に記載のアクリル共重合体。
項４ カルボキシル基を有する架橋性モノマーがエチレン性不飽和ジカルボン酸モノエステルである項１～３いずれかに記載のアクリル共重合体。
項５ エチレン単量体に由来する構成単位を含む請求項１～４いずれかに記載のアクリル共重合体。
項６ 項１～５いずれかに記載のアクリル共重合体と架橋剤を含有するアクリル共重合体含有組成物。
項７ 項６に記載のアクリル共重合体含有組成物を用いて作製された架橋物。 Aspects of the present invention are as follows.
Item 1 Containing 18 to 28% by mass of a structural unit derived from a methacrylic acid ester represented by the following general formula (I) (provided that the structural unit derived from methyl methacrylate is less than 10% by mass), and a carboxyl group An acrylic copolymer containing 0.5 to 5% by mass of structural units derived from a crosslinkable monomer having

(In general formula (I), _R1 is a methyl group, and _R2 is either an alkyl group or an alkoxyl group.)
Item 2 The acrylic copolymer according to Item 1, which satisfies the following conditions (i) to (ii).
(i) The solubility parameter (SP value) of the copolymer containing the structural unit derived from the methacrylic acid ester shown in (I) above according to the Fedors method is 9.8 or more.
(ii) The glass transition temperature (Tg) of the copolymer containing structural units derived from the methacrylic acid ester shown in (I) above, which is determined by the Fox formula, is -25°C or lower.
Item 3 Structural units derived from an alkyl acrylate having an alkyl group of 1 to 8 carbon atoms and/or structural units derived from an alkoxyalkyl ester having an alkoxyalkyl group of 2 to 8 carbon atoms 20 to 81. 3. The acrylic copolymer according to Item 1 or 2, containing 9% by mass.
Item 4. The acrylic copolymer according to any one of Items 1 to 3, wherein the crosslinkable monomer having a carboxyl group is an ethylenically unsaturated dicarboxylic acid monoester.
[5] The acrylic copolymer according to any one of [1] to [4], which contains a structural unit derived from an ethylene monomer.
Item 6. An acrylic copolymer-containing composition comprising the acrylic copolymer according to any one of Items 1 to 5 and a cross-linking agent.
Item 7. A crosslinked product produced using the acrylic copolymer-containing composition according to Item 6.

The rubber material produced using the composition containing the acrylic copolymer of the present invention has an excellent balance of oil resistance and cold resistance, and is particularly excellent in acid resistance. It is suitable as an industrial rubber material, a rubber material for automobiles, and the like.

（一般式（Ｉ）中、Ｒ_１はメチル基、Ｒ₂はアルキル基、アルコキシル基のいずれかである。） First, the acrylic copolymer in the present invention will be explained.
The acrylic copolymer of the present invention contains 18 to 28% by mass of structural units derived from a methacrylic acid ester represented by the following general formula (I) (provided that the structural unit derived from methyl methacrylate is less than 10% by mass. A) an acrylic copolymer containing 0.5 to 5% by mass of structural units derived from a crosslinkable monomer having a carboxyl group.

(In general formula (I), _R1 is a methyl group, and _R2 is either an alkyl group or an alkoxyl group.)

In the methacrylic acid ester represented by the general formula (I) of the present invention, R ₂ is preferably an alkyl group having 1 to 18 carbon atoms, an alkoxy group having 2 to 18 carbon atoms, and an alkyl group having 1 to 12 carbon atoms. more preferably an alkoxy group having 2 to 12 carbon atoms, an alkyl group having 1 to 8 carbon atoms, more preferably an alkoxy group having 2 to 8 carbon atoms, an alkyl group having 1 to 4 carbon atoms, An alkoxy group having 2 to 4 carbon atoms is more preferred.

Specific examples of the methacrylic acid ester represented by the general formula (I) of the present invention include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, ethoxyethyl methacrylate, methoxyethyl methacrylate, isobutyl methacrylate, and methacrylic acid. n-pentyl, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, n-decyl methacrylate, isodecyl methacrylate, n-dodecyl methacrylate, n-lauryl methacrylate and n-octadecyl methacrylate, etc. Structural units derived from methacrylic acid esters can be exemplified, n-butyl methacrylate, ethoxyethyl methacrylate, methoxyethyl methacrylate, 2-ethylhexyl methacrylate, derived from a methacrylic acid alkyl ester selected from isodecyl methacrylate A structural unit derived from n-butyl methacrylate or ethoxyethyl methacrylate is preferred. These may be structural units derived from single or two or more (meth)acrylic acid alkyl esters.

In the acrylic copolymer of the present invention, the content of the structural unit derived from the methacrylic acid ester represented by the general formula (I) is 18% by mass or more in the total structural units of the acrylic copolymer, and 19% by mass. The upper limit is preferably 28% by mass or less, more preferably 25% by mass or less. In addition, in the present invention, when methyl methacrylate is used in the methacrylic acid ester represented by the general formula (I), it is less than 10% by mass in all structural units of the acrylic copolymer from the viewpoint of acid resistance. preferably 8% by mass or less.

A structural unit derived from a crosslinkable monomer having a carboxy group is preferably a structural unit having an ethylenically unsaturated dicarboxylic acid monoester.
Structural units derived from crosslinkable monomers having a carboxy group include structural units derived from ethylenically unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, 2-pentenoic acid, and cinnamic acid, fumaric acid, and malein. Structural units derived from ethylenically unsaturated dicarboxylic acids such as acid and itaconic acid, monoalkyl fumarate such as monomethyl fumarate, monoethyl fumarate, monopropyl fumarate, monobutyl fumarate, monohexyl fumarate, and monooctyl fumarate , monomethyl maleate, monoethyl maleate, monopropyl maleate, monobutyl maleate, monopentyl maleate, monoalkyl maleate such as monodecyl maleate, monomethyl itaconate, monoethyl itaconate, monopropyl itaconate, monobutyl itaconate Structural units derived from ethylenically unsaturated dicarboxylic acid monoesters such as itaconic acid monoalkyl esters can be exemplified.

The content of structural units derived from a crosslinkable monomer having a carboxy group in the acrylic copolymer of the present invention is preferably 0.1% by mass or more, and is 0.5% by mass or more, based on all structural units. is more preferably 5% by mass or less, and more preferably 2% by mass or less. A constitutional unit derived from a crosslinkable monomer having a carboxy group within the above range is preferable in terms of physical properties such as strength and compression set, and workability.

In the acrylic copolymer of the present invention, a structural unit derived from an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and/or an alkoxyalkyl acrylate having an alkoxyalkyl group having 2 to 8 carbon atoms. It preferably contains a structural unit derived from it, and is preferably a structural unit derived from an acrylic acid alkyl ester having an alkyl group of 1 to 8 carbon atoms. These may be structural units derived from single or two or more acrylic acid esters.
Specific examples of structural units derived from acrylic acid alkyl esters having an alkyl group having 1 to 8 carbon atoms include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, acrylic Examples of structural units derived from acrylic acid esters such as isobutyl acrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, and cyclohexyl acrylate is preferably a structural unit derived from ethyl acrylate or n-butyl acrylate.
Specific examples of structural units derived from alkoxyalkyl acrylates having an alkoxyalkyl group having 2 to 8 carbon atoms include methoxymethyl acrylate, methoxyethyl acrylate, ethoxymethyl acrylate, 2-ethoxyethyl acrylate, acrylic 2-propoxyethyl acid, 2-butoxyethyl acrylate, 2-methoxypropyl acrylate, 2-ethoxypropyl acrylate, 3-methoxypropyl acrylate, 3-ethoxypropyl acrylate, 4-methoxybutyl acrylate, acrylic acid Structural units derived from acrylic acid esters such as 4-ethoxybutyl can be exemplified, and structural units derived from methoxyethyl acrylate are preferred.

In the (meth)acrylic copolymer of the present invention, a structural unit derived from an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms and/or an alkoxyalkyl acrylate having an alkoxyalkyl group having 2 to 8 carbon atoms The content of structural units derived from an ester is 20 to 81.9% by mass, preferably 49.9 to 81.9% by mass, of the total structural units of the (meth)acrylic copolymer, 59 0.5 to 80.5% by mass is more preferable. When the structural unit is within the above range, it is preferable from the viewpoint of the balance between cold resistance and oil resistance.

The acrylic copolymer of the present invention may contain structural units derived from ethylene monomers.

In the (meth)acrylic copolymer of the present invention, when it contains a structural unit derived from an ethylene monomer, the content of the structural unit derived from the ethylene monomer is the total amount of the (meth)acrylic copolymer. It is preferably 1 to 70% by mass, more preferably 5 to 50% by mass, particularly preferably 10 to 50% by mass in the structural unit.

Furthermore, the acrylic copolymer of the present invention may contain, in addition to the above structural units, structural units derived from other monomers copolymerizable therewith. 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, and structural units derived from conjugated diene monomers. , structural units derived from non-conjugated dienes, structural units derived from other olefins, and the like.

Structural units derived from ethylenically unsaturated nitriles include structural units derived from compounds such as acrylonitrile, methacrylonitrile, α-methoxyacrylonitrile and vinylidene cyanide.

Structural units derived from (meth)acrylamide monomers include acrylamide, methacrylamide, diacetoneacrylamide, diacetonemethacrylamide, N-butoxymethylacrylamide, N-butoxymethylmethacrylamide, N-butoxyethylacrylamide, N-butoxy ethyl methacrylamide, N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, N-propioxymethylacrylamide, N-propioxymethylmethacrylamide, N-methylacrylamide, N-methylmethacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, ethacrylamide, crotonamide, cinnamic acid amide, malediamide, itacondiamide, Structural units derived from compounds such as methylmaleamide, methylitaconamide, maleimide and itaconimide are included.

Structural units derived from aromatic vinyl monomers include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, o-ethylstyrene, p-ethylstyrene, α-fluorostyrene, p-trifluoromethyl styrene, p-methoxystyrene, p-aminostyrene, p-dimethylaminostyrene, p-acetoxystyrene, styrenesulfonic acid or its salts, α-vinylnaphthalene, 1-vinylnaphthalene-4-sulfonic acid or its salts, 2- Structural units derived from compounds such as vinylfluorene, 2-vinylpyridine, 4-vinylpyridine, divinylbenzene, diisopropenylbenzene, and vinylbenzyl chloride can be mentioned.

Structural units derived from conjugated diene-based monomers include 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, Structural units derived from compounds such as 3-butadiene, 1,3-pentadiene, 1,3-hexadiene, chloroprene and piperylene can be mentioned.

Structural units derived from non-conjugated dienes include structural units derived from compounds of non-conjugated dienes such as 1,4-pentadiene, 1,4-hexadiene, ethylidene norbornene, norbornadiene, and dicyclopentadiene. .

Structural units derived from other olefinic monomers include esters such as dicyclopentadienyl acrylate, dicyclopentadienyl methacrylate, dicyclopentadienylethyl acrylate, and dicyclopentadienylethyl methacrylate. 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.

The copolymer of the present invention preferably has a solubility parameter (SP value) of 9.8 or more according to the Fedors method, and more preferably 9.8 to 10.2 from the viewpoint of the oil resistance of the resulting rubber. preferable.

Here, the "solubility parameter value (SP value)" in the present specification is based on the following formula according to the Fedors method [Robert F. Fedors, Polymer Engineering and Science, 14, 147-154 (1974)]. is the determined value δ.
Fedors formula: δ = (ΣΔei/ΣΔvi) ^1/2
[Unit: (cal/cm ³ ) ^1/2 ]
[Here, Δei: vaporization energy of atoms and atomic groups (cal/mol), Δvi: molar volume (cm ³ /mol). ]

The copolymer of the present invention preferably has a glass transition temperature (Tg) of -25.degree. Although the lower limit is not particularly limited, it is -45°C or higher.

The glass transition temperature (calculated Tg) can be calculated from Fox's formula [2].
1/calculated Tg=W1/Tg(1)+W2/Tg(2)+...+Wn/Tn [2]
W1, W2, . , Tg(2), .
The glass transition temperature of homopolymers is known from various literatures, catalogs, etc., and is described, for example, in J. Brandup, E.H. Immergut, E.A. Grulke: Polymer Handbook: John Wiley & Sons, Inc. there is For monomers for which there are no numerical values in various documents, values measured by general thermal analysis or differential thermal analysis can be adopted.

In the acrylic copolymer of the present invention, the content of the structural units can be determined by the nuclear magnetic resonance spectrum of the obtained polymer.

<Method for producing acrylic copolymer>
The acrylic copolymer used in the present invention can be obtained by polymerizing various monomers. All of the monomers to be used may be commercially available products, and there are no particular restrictions.

As the form of the polymerization reaction, any of an emulsion polymerization method, a suspension polymerization method, a bulk polymerization method, and a solution polymerization method can be used. Emulsion polymerization under normal pressure, which is generally used as a method for producing polymers, is preferred.

In the case of polymerization by emulsion polymerization, a conventional method may be used, and conventionally known polymerization initiators, emulsifiers, chain transfer agents, polymerization terminators and the like can be used.

The emulsifier used in the present invention is not particularly limited, and nonionic emulsifiers and anionic emulsifiers generally used in the emulsion polymerization method can be used. Examples of nonionic emulsifiers include polyoxyethylene alkyl ethers, polyoxyethylene alcohol ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polycyclic phenyl ethers, polyoxyalkylene alkyl ethers, sorbitan fatty acid esters, polyoxyethylene fatty acid esters, and Examples include polyoxyethylene sorbitan fatty acid esters, and examples of anionic emulsifiers include alkylbenzene sulfonates, alkyl sulfates, polyoxyethylene alkyl ether sulfates, polyoxyalkylene alkyl ether phosphates or salts thereof, and fatty acid salts. Examples of salts include alkali metals such as sodium and potassium, ammonia, and amines. You may use 1 type(s) or 2 or more types of these. Representative examples of anionic emulsifiers include sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and triethanolamine dodecyl sulfate.

The amount of the emulsifier used in the present invention may be the amount generally used in the emulsion polymerization method. 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 using a reactive surfactant as a monomer component, addition of an emulsifier is not necessarily required.

The polymerization initiator used in the present invention is not particularly limited, and polymerization initiators commonly used in emulsion polymerization can be used. Specific examples thereof include inorganic polymerization initiators represented by 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, cumene hydroperoxide, diisopropylbenzene hydroperoxide, p-menthane hydroperoxide, 1,1,3,3-tetramethyl Butyl 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, dibenzoyl peroxide, di(3-methylbenzoyl) peroxide, benzoyl(3-methylbenzoyl) peroxide , diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di(2-ethylhexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate carbonate, cumyl peroxyneodecanate, 1,1,3,3-tetramethylbutyl peroxyneodecanate, t-hexyl peroxyneodecanate, t-butyl peroxyneodecanoate, t-hexyl peroxyneodecanate Valate, t-butylperoxypivalate, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexa t-hexylperoxy-2-ethylhexanate, t-butylperoxy-2-ethylhexanate, t-butylperoxylaurate, t-butylperoxy-3,5,5-trimethylhexanate, t-hexyl peroxyisopropyl monocarbonate, t-butyl peroxy isopropyl monocarbonate, t-butyl peroxy 2-ethylhexyl monocarbonate, 2,5-dimethyl-2 ,5-di(benzoylperoxy)hexane, t-butylperoxyacetate, t-hexylperoxybenzoate, t-butylperoxybenzoate, 2,5-dimethyl-2,5-di(t-butylperoxy) Organic peroxide polymerization initiators such as hexane, hydroperoxide, azobisisobutyronitrile, 4-4'-azobis(4-cyanovaleric acid), 2-2'-azobis[2-(2- imidazolin-2-yl) propane, 2-2′-azobis (propane-2-carbamidine) 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′- and azo initiators such as azobis {2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propanamide}. These polymerization initiators may be used singly or in combination of two or more.

The amount of the polymerization initiator used in the present invention may be the amount generally used in the emulsion polymerization method. Specifically, it is 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.

Organic peroxides and inorganic peroxides as polymerization initiators can also be used as redox polymerization initiators by combining them with reducing agents. The reducing agent used in combination is not particularly limited, but compounds containing metal ions in a reduced state such as ferrous sulfate and cuprous naphthenate, methane compounds such as sodium methanesulfonate, and amines such as dimethylaniline. compounds, ascorbic acid and its salts, and reducing inorganic salts such as alkali metal salts of sulfurous acid and thiosulfate. These reducing agents can be used alone or in combination of two or more. The amount of the reducing agent to be used is preferably 0.0003 to 10.0 parts by weight per 100 parts by weight of the charged monomer.

A chain transfer agent can be used as needed. Specific examples of chain transfer agents include alkylmercaptans such as n-hexylmercaptan, n-octylmercaptan, t-octylmercaptan, n-dodecylmercaptan, t-dodecylmercaptan and n-stearylmercaptan, 2,4-diphenyl-4 -methyl-1-pentene, 2,4-diphenyl-4-methyl-2-pentene, xanthogen compounds such as dimethylxanthogen disulfide, diisopropylxanthogen disulfide, terpinolene, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram mono Thiuram compounds such as sulfide, phenolic compounds such as 2,6-di-t-butyl-4-methylphenol, styrenated phenol, allyl compounds such as allyl alcohol, halogens such as dichloromethane, dibromomethane, and carbon tetrabromide Hydrocarbon compounds, vinyl ethers such as α-benzyloxystyrene, α-benzyloxyacrylonitrile, α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexylthio Glycolate and the like may be mentioned, and one or more of these may be used. Although the amount of these chain transfer agents is not particularly limited, they are usually used in an amount of 0 to 5 parts by weight per 100 parts by weight of the charged monomers.

Examples of the polymerization terminator include hydroxylamine, hydroxylamine sulfate, diethylhydroxyamine, hydroxylaminesulfonic acid and alkali metal salts thereof, sodium dimethyldithiocarbamate, and quinone compounds such as hydroquinone. The amount of polymerization terminator to be used is not particularly limited, but is usually 0 to 2 parts by mass with respect to 100 parts by mass of all monomers.

Further, the pH of the polymer obtained by the above method can be adjusted by using a base as a pH adjuster, if necessary. Specific examples of bases include sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, inorganic ammonium compounds, organic amine compounds and the like. The pH range is pH 1-11, preferably pH 1.5-10.5, more preferably pH 2-10.

In addition to these, polymerization auxiliary materials such as particle size modifiers, chelating agents, and oxygen scavengers can be used as necessary.

Emulsion polymerization may be of a batch system, a semi-batch system, or a continuous system. Polymerization time and polymerization temperature are not particularly limited. Although it can be appropriately selected depending on the type of polymerization initiator to be used, the polymerization temperature is generally 10 to 100° C. and the polymerization time is 0.5 to 100 hours.

There are no particular restrictions on the method for recovering the polymer obtained by the above method, and a commonly practiced method can be employed. An example of the method is a method of continuously or batchwise supplying the polymerization liquid to an aqueous solution containing a coagulant, and this operation yields a coagulated slurry. The coagulant is not particularly limited, and is preferably an inorganic metal salt, and specific examples thereof include sodium sulfate, magnesium sulfate, aluminum sulfate, sodium chloride, calcium chloride, and the like. At that time, the temperature of the aqueous solution containing the coagulant is affected by coagulation conditions such as the type and amount of monomer used, and the shear force due to stirring, etc., so it cannot be uniformly specified, but it is generally 50 ° C. Above, preferably in the range of 60 ° C. to 100 ° C.

The coagulated slurry obtained by the above method is preferably washed with water to remove the coagulant. If washing with water is not performed at all, or if washing is insufficient, there is a risk that ion residues derived from the coagulant will be precipitated during the molding process.

An acrylic copolymer can be obtained by removing moisture from the solidified slurry after washing with water and drying it. Although the drying method is not particularly limited, it is generally dried using a flash dryer, a fluidized bed dryer, or the like. Also, a dehydration step using a centrifugal separator or the like may be performed before the drying step.

From the standpoint of workability, the molecular weight range of the acrylic copolymer produced in this way and used in the present invention is 10 in terms of Mooney viscosity (ML ₁₊₄ ) at 100° C. in the Mooney scorch test specified in JIS K 6300. It is preferably from 100 to 100, more preferably from 15 to 90, and even more preferably from 20 to 80.

<Composition containing acrylic copolymer>
The acrylic copolymer-containing composition of the present invention contains at least the above acrylic copolymer and a cross-linking agent.

Examples of cross-linking agents include conventionally known cross-linking agents commonly used for cross-linking rubber such as polyamine compounds, polyepoxy compounds, polyisocyanate compounds, aziridine compounds, sulfur compounds, basic metal oxides and organic metal halides. agent can be used. Among these, polyvalent amine compounds are preferably used.

Examples of polyvalent amine compounds include aliphatic polyvalent amine compounds such as hexamethylenediamine, hexamethylenediamine carbamate, N,N'-dicinnamylidene-1,6-hexanediamine, 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-xylyl Examples include aromatic polyvalent amine compounds such as diamine, 1,3,5-benzenetriamine, 1,3,5-benzenetriaminomethyl, and isophthalic acid dihydrazide.

Polyepoxy compounds include 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. compounds, glycidyl ether type epoxy compounds such as hydrogenated bisphenol A type epoxy compounds; alicyclic epoxy compounds, glycidyl ester type epoxy compounds, glycidylamine type epoxy compounds, isocyanurate type epoxy compounds and other polyvalent epoxy compounds be done.

Polyvalent isocyanate 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, bicycloheptane triisocyanate and the like.

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

Sulfur compounds include sulfur, 4,4'-dithiomorpholine, tetramethylthiuram disulfide, tetraethylthiuram disulfide and the like.

Basic metal oxides include zinc oxide, lead oxide, calcium oxide, magnesium oxide and the like.

Examples of organic metal halides include dicyclopentadienyl metal dihalides, and examples of metals include titanium and zirconium.

These cross-linking agents may be used alone or in combination of two or more. The amount of the cross-linking agent is 0.05 to 20 parts by weight, preferably 0.1 to 10 parts by weight, per 100 parts by weight of the acrylic copolymer of the present invention.

The acrylic copolymer-containing composition of the present invention may also contain other additives commonly used in the art, such as lubricants, anti-aging agents, light stabilizers, fillers, reinforcing agents, plasticizers, and processing aids. Agents, pigments, colorants, cross-linking accelerators, cross-linking auxiliaries, cross-linking retarders, antistatic agents, foaming agents and the like can be optionally added.

As the reinforcing agent, carbon black or the like can be exemplified. It is preferably 30 parts by mass or more, more preferably 120 parts by mass or less, and more preferably 100 parts by mass or less.

Examples of anti-aging agents include amines, phosphates, quinolines, cresols, phenols, dithiocarbamate metal salts and the like, and diphenylamines such as 4,4'-bis(α,α-dimethylbenzyl)diphenylamine. Amines such as derivatives and phenylenediamine derivatives are preferred.

The content of the antioxidant is preferably 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, with respect to 100 parts by mass of the acrylic copolymer, and 0.3 to 3 parts by mass is particularly preferred.

Examples of cross-linking accelerators include guanidine compounds, amine compounds, thiourea compounds, thiazole compounds, sulfenamide compounds, thiuram compounds, quaternary ammonium salts, etc. Guanidine compounds and amine compounds are preferred.

The content of the cross-linking accelerator is preferably 0.1 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, with respect to 100 parts by mass of the acrylic copolymer, and 0.1 to 5 parts by mass is particularly preferred.

Further, blending with rubbers, resins, etc., which is commonly practiced in the technical field, is also possible without departing from the gist of the present invention. Examples of the rubber 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, and the like. 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, and the like.

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

As a method for blending the acrylic copolymer-containing composition of the present invention, any means conventionally used in the field of polymer processing, such as an open roll, a Banbury mixer, various kneaders, and the like can be used.

As the compounding procedure, a usual procedure in the field of polymer processing can be used. For example, first, only the polymer is kneaded, then a cross-linking agent and a compounding agent other than the cross-linking accelerator are added to prepare an A kneading compound, and then the cross-linking agent and cross-linking accelerator are added to perform B kneading. be able to.

The composition of the present invention can be made into a crosslinked product by heating to 100 to 250°C. The cross-linking time varies depending on the temperature, but is generally carried out between 0.5 and 300 minutes. In cross-linking molding, in the case of integrally performing cross-linking and molding, in the case of forming a cross-linked product by heating the previously molded acrylic copolymer-containing composition, or in the case of molding the cross-linked product by heating first. may be processed. Specific methods for cross-linking molding include compression molding using a metal mold, injection molding, steam can, air bath, heating with infrared rays, or microwaves.

The thus obtained crosslinked product of the present invention is excellent in cold resistance, oil resistance and acid resistance.

Therefore, the crosslinked product of the present invention utilizes the above properties to provide O-rings, packings, diaphragms, oil seals, shaft seals, bearing seals, mechanical seals, well head seals, seals for electrical and electronic equipment, and seals for pneumatic equipment. , a cylinder head gasket that is attached to the connection between the cylinder block and the cylinder head, a rocker cover gasket that is attached to the connection between the rocker cover and the cylinder head, and a connection between the oil pan and the cylinder block or transmission case. oil pan gaskets, fuel cell separator gaskets mounted between a pair of housings sandwiching a unit cell having a positive electrode, an electrolyte plate and a negative electrode, and top cover gaskets for hard disk drives.

In addition, the crosslinked product in the present invention can be used as a rubber material, and as an extrusion molding product and a mold crosslinked product used for automobile applications, fuel tanks such as fuel hoses, filler neck hoses, vent hoses, vapor hoses, and oil hoses. Suitable for various types of hoses such as surrounding fuel oil hoses, turbo air hoses, air hoses such as emission control hoses, radiator hoses, heater hoses, brake hoses and air conditioner hoses.

The present invention will be specifically described with reference to examples and comparative examples. However, the present invention is not limited to these.
In the present examples and comparative examples, an acrylic copolymer-containing composition containing the obtained acrylic copolymer and a cross-linking agent, and a cross-linked composition obtained by cross-linking the acrylic copolymer-containing composition were used. The physical properties of the object were evaluated.

[Example 1]
(Production of acrylic copolymer A)
200 parts by mass of water, 1.7 parts by mass of polyoxyalkylene alkyl ether phosphate, 41.5 parts by mass of ethyl acrylate as a monomer, and After 37.5 parts by mass of n-butyl acrylate, 19.6 parts by mass of n-butyl methacrylate, and 1.4 parts by mass of monoethyl fumarate were charged, and oxygen was sufficiently removed by repeating degassing under reduced pressure and nitrogen replacement. , 0.1 parts by mass of sodium ascorbate and 0.1 parts by mass of potassium persulfate are added to initiate an emulsion polymerization reaction at normal pressure and normal temperature, and the reaction is continued until the polymerization conversion reaches 95%. The polymerization was stopped by adding 0.0075 parts by weight. The resulting emulsion polymerization liquid was coagulated with an aqueous sodium sulfate solution, washed with water and dried to obtain an acrylic copolymer A.

[Example 2]
(Production of acrylic copolymer B)
From Example 1, the monomers to be charged and their amounts were 36.7 parts by mass of ethyl acrylate, 12.7 parts by mass of n-butyl acrylate, 29.7 parts by mass of 2-methoxyethyl acrylate, and 19.5 parts by mass of isodecyl methacrylate. An acrylic copolymer B was obtained in the same manner as in Example 1, except that parts by mass and monoethyl fumarate were changed to 1.4 parts by mass.

[Example 3]
(Production of acrylic copolymer C)
From Example 1, the monomers to be charged and their amounts were 49.7 parts by mass of ethyl acrylate, 24.7 parts by mass of n-butyl acrylate, 4.5 parts by mass of 2-ethylhexyl methacrylate, and 19 parts by mass of 2-ethoxyethyl methacrylate. An acrylic copolymer C was obtained in the same manner as in Example 1, except that 0.7 parts by mass and 1.4 parts by mass of monoethyl fumarate were used.

[Example 4]
(Production of acrylic copolymer D)
From Example 1, the monomers to be charged and their amounts were 17.7 parts by mass of ethyl acrylate, 53.7 parts by mass of n-butyl acrylate, 11.7 parts by mass of butyl methacrylate, and 7.7 parts by mass of 2-methoxyethyl acrylate. An acrylic copolymer D was obtained in the same manner as in Example 1, except that the parts by mass were changed to 7.8 parts by mass of methyl methacrylate and 1.4 parts by mass of monoethyl fumarate.

[Comparative Example 1]
(Production of acrylic copolymer E)
From Example 1, the monomers to be charged and their amounts were changed to 49.5 parts by mass of ethyl acrylate, 44.5 parts by mass of n-butyl acrylate, 4.6 parts by mass of methyl methacrylate and 1.4 parts by mass of monoethyl fumarate. An acrylic copolymer E was obtained in the same manner as in Example 1 except that the procedure was changed.

[Comparative Example 2]
(Production of acrylic copolymer F)
From Example 1, 39.5 parts by mass of n-butyl acrylate, 29.5 parts by mass of 2-methoxyethyl acrylate, 29.6 parts by mass of 2-ethylhexyl methacrylate and 1 part by mass of monoethyl fumarate An acrylic copolymer F was obtained in the same manner as in Example 1, except that the content was changed to 4 parts by mass.

[Comparative Example 3]
(Production of acrylic copolymer G)
From Example 1, the monomers to be charged and their amounts were changed to 39.4 parts by mass of ethyl acrylate, 30.9 parts by mass of n-butyl acrylate, 28.3 parts by mass of butyl methacrylate and 1.4 parts by mass of monoethyl fumarate. An acrylic copolymer G was obtained in the same manner as in Example 1 except that the procedure was changed.

<Dissolution parameters>
For the acrylic copolymers A to G, the solubility parameter (SP value) was calculated by the Fedors method. The results are shown in Tables 1 and 2.

<Glass transition temperature>
For the acrylic copolymers A to G, the glass transition temperature (Tg) determined by Fox's formula was calculated. The results are shown in Tables 1 and 2.

<Mooney viscosity (ML ₁₊₄ , 100°C)>
For the acrylic copolymers A to G, the Mooney viscosity (ML ₁₊₄ ) was measured at a measurement temperature of 100° C. using a Mooney Viscometer AM-3 manufactured by Toyo Seiki Co., Ltd. according to the Mooney viscosity test of the uncrosslinked rubber physical test method of JIS K6300. It was measured. The results are shown in Tables 1 and 2.

(Production of Acrylic Copolymer-Containing Composition)
100 parts by weight each of acrylic copolymers A to G, 60 parts by weight of carbon black (classification according to ASTM D1765; N550), 2 parts by weight of stearic acid (carbon black dispersant, softening agent) and 4,4'-bis ( 2 parts by mass of α,α-dimethylbenzyl)diphenylamine (antiaging agent) are kneaded in a kneader at 120° C., then 0.6 parts by mass of hexamethylenediamine carbamate (aliphatic diamine cross-linking agent), di-o-tolylguanidine (Crosslinking accelerator) 2 parts by mass was added, and kneaded at room temperature with a kneading roll to prepare each acrylic copolymer-containing composition.

(Production of uncrosslinked sheet)
Each acrylic copolymer-containing composition obtained above was kneaded with a kneader and an open roll to prepare an uncrosslinked sheet having a thickness of 2 to 2.5 mm.

(Mooney scorch test)
Using the obtained uncrosslinked sheet, the Mooney scorch test defined in JIS K 6300 was measured at 125° C. using a Mooney Viscometer AM-3 manufactured by Toyo Seiki Co., Ltd. The results are shown in Tables 1 and 2.

(Preparation of crosslinked product)
The uncrosslinked rubber sheet obtained above was press-treated at 180°C for 10 minutes and then heated in an air oven at 180°C for 3 hours to obtain a crosslinked product.

(Cold resistance test)
According to JIS K 6261, TM-2533 manufactured by Ueshima Seisakusho Co., Ltd. was used for evaluation by the Gehman torsion test, and the temperature (T10) at which the modulus at room temperature (25° C.) became 10 times was measured. The lower the T10 temperature, the better the cold resistance. The results are shown in Tables 1 and 2.

(Normal physical property test)
Using the obtained crosslinked product, a tensile test and a hardness test were evaluated using TG-2kN manufactured by Minebea Co., Ltd. The tensile test was performed according to JIS K6251, and the hardness test was performed according to JIS K6253. The results are shown in Tables 1 and 2.

(Acid resistance test: Zinc chloride aqueous solution immersion test)
Cut the crosslinked product described above into 1 cm pieces each, put it in 100 ml of a 1 wt % zinc chloride aqueous solution, store it in an autoclave at 150° C. for 50 hours, take out the test piece, air dry it, and measure the change in hardness in the same manner as in the evaluation of normal physical properties. did The results are shown in Tables 1 and 2.

(Acid resistance test: mixed acid aqueous solution immersion test)
Cut the crosslinked product described above into 1 cm pieces and add 100 ml of an acidic aqueous solution (Add 1 ml of sulfuric acid, 500 μl of hydrochloric acid, 1.5 ml of 60% aqueous nitric acid, and 500 μl of acetic acid to 500 ml of water to prepare an acidic aqueous solution of pH 1). After being stored in an autoclave at 150° C. for 50 hours, the test piece was taken out, air-dried, and then measured for change in hardness in the same manner as in the evaluation of normal physical properties. The results are shown in Tables 1 and 2.

(Oil resistance test)
The oil resistance test was conducted according to JISK6258.
A test piece was prepared by obtaining a sheet-like cross-linked acrylic rubber and punching out the obtained sheet-like cross-linked acrylic rubber in the same manner as in the evaluation of the normal physical properties described above. Specifically, a test piece having a length of 30 mm, a width of 20 mm, and a thickness of 2.0±0.2 mm was prepared for the volume change test.

This test piece for volume change test was placed in a glass tube having an inner volume of 250 cc, and 200 cc of the test liquid was put thereinto and placed so that the test piece was completely immersed in the liquid. A glass tube was placed in a heating bath and heated at 150° C. for 72 hours.

As the test liquid, test lubricating oil No. 3 (trade name: IRM903, manufactured by Nippon Sun Oil Co., Ltd.) described in JISK6258 was used.

After heating, the test piece for volume change test was taken out, the test liquid was wiped off, the volume was measured, and the volume change rate ΔV (%) from the initial volume was calculated. The smaller the volume change rate, the better the oil resistance. The results are shown in Tables 1 and 2.

As shown in Tables 1 and 2, Examples 1 to 4, which are crosslinked products obtained by crosslinking the copolymers of the present invention, exhibited excellent results in the balance of oil resistance, cold resistance, and acid resistance. On the other hand, in Comparative Examples 1 to 3, which are cross-linked products obtained by cross-linking copolymers not belonging to the present invention, in Comparative Example 1, the acid resistance hardness change rate of the cross-linked product was large. Moreover, in Comparative Example 2, the acid resistance and oil resistance of the crosslinked product in the zinc chloride aqueous solution deteriorated. In addition, in Comparative Example 3, the result was that the oil resistance and cold resistance of the crosslinked product were deteriorated. From the above results, it can be seen that the acrylic copolymer of the present invention is excellent in acid resistance while maintaining a balance between oil resistance and cold resistance.

The acrylic copolymer of the present invention can be widely used as a material for rubber products and resin products, or as a raw material for adhesives and paints, taking advantage of its excellent cold resistance, oil resistance and acid resistance. In particular, the crosslinked product produced using the acrylic copolymer of the present invention is extremely effective in applications such as industrial rubber materials such as engine gaskets, oil hoses, air hoses, and O-rings, and automotive rubber materials.

Claims (7)

Containing 18 to 28% by mass of a structural unit derived from a methacrylic acid ester represented by the following general formula (I) (provided that the structural unit derived from methyl methacrylate is less than 10% by mass) and having a carboxyl group An acrylic copolymer containing 0.5 to 5% by mass of structural units derived from a crosslinkable monomer.

(In general formula (I), _R1 is a methyl group, and _R2 is either an alkyl group or an alkoxyl group.) 2. The acrylic copolymer according to claim 1, which satisfies the following conditions (i) to (ii).
(i) The solubility parameter (SP value) of the copolymer containing the structural unit derived from the methacrylic acid ester shown in (I) above according to the Fedors method is 9.8 or more.
(ii) The glass transition temperature (Tg) of the copolymer containing structural units derived from the methacrylic acid ester shown in (I) above, which is determined by the Fox formula, is -25°C or lower. 20 to 81.9 masses of constituent units derived from an alkyl acrylate ester having an alkyl group having 1 to 8 carbon atoms and/or an alkoxyalkyl ester having an alkoxyalkyl group having 2 to 8 carbon atoms. The acrylic copolymer according to claim 1 or 2, containing %. 4. The acrylic copolymer according to any one of claims 1 to 3, wherein the crosslinkable monomer having a carboxyl group is an ethylenically unsaturated dicarboxylic acid monoester. 5. The acrylic copolymer according to any one of claims 1 to 4, which contains a structural unit derived from an ethylene monomer. An acrylic copolymer-containing composition comprising the acrylic copolymer according to any one of claims 1 to 5 and a cross-linking agent. A crosslinked product produced using the acrylic copolymer-containing composition according to claim 6 .