Method for producing a (meth)acrylic acid ester polymer

Abstract

To provide a method for producing a (meth) acrylic acid ester polymer having low yellowness and high uniformity of molecular weight with high polymerization initiation efficiency.SOLUTION: There is provided a method for producing a (meth) acrylic acid ester polymer by subjecting a methacrylic acid ester to anionic polymerization in the presence of at least one Lewis base (A), an organolithium compound (B) and an organoaluminum compound (C) represented by AlR1OAr1OAr2 (I) (wherein R1 is a saturated hydrocarbon group which may have a substituent or an aromatic hydrocarbon group which may have a substituent, and OAr1 and OAr2 are each independently an aryloxy group which may have a substituent) in the polymerization system and followed by further polymerizing a methacrylic acid ester in the presence of an aluminum compound (S) represented by AlR2R3R4 (II) (wherein R2, R3 and R4 are each independently a hydrogen atom, a saturated hydrocarbon group which may have a substituent or an aromatic hydrocarbon group which may have a substituent).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a (meth)acrylic acid ester polymer. [Background technology]

[0002] (Meth)acrylic acid ester polymers are used as materials for optical components, lighting components, signboard components, decorative components, etc., taking advantage of their excellent transparency.

[0003] For example, Patent Document 1 proposes that, in an anionic polymerization method for (meth)acrylic acid esters in the presence of a tertiary organoaluminum compound, an organolithium compound, and at least one type of Lewis base, the proportion of a compound having a specific chemical structure as the tertiary organoaluminum compound is within a specific range, thereby enabling the production of a (meth)acrylic polymer with a highly uniform molecular weight and with high polymerization initiation efficiency without impairing the inherent properties of the (meth)acrylic polymer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-178134 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when an attempt is made to produce a (meth)acrylic acid ester polymer by the method described in the above patent document, it has been found that the product contains phenols (e.g., 2,6-di-t-butyl-4-methylphenol) derived from the organoaluminum compound used during production, and these phenols turn into quinone compounds (e.g., 2,6-di-t-butyl-4-methylene-2,5-cyclohexadiene-1-one) upon exposure to heat or ultraviolet light, causing the resulting (meth)acrylic acid ester polymer to yellow, which may adversely affect the optical properties.

[0006] An object of the present invention is to provide a method for producing a (meth)acrylic acid ester polymer having low yellowness and high uniformity in molecular weight with high polymerization initiation efficiency. [Means for solving the problem]

[0007] According to the present invention, the above object is achieved by providing the following items [1] to [7]. [1] In the polymerization system, at least one Lewis base (A), an organolithium compound (B), and AlR 1 OAr 1 OAr 2 (I) (wherein, R 1 represents a saturated hydrocarbon group which may have a substituent, or an aromatic hydrocarbon group which may have a substituent, and OAr 1 and OAr 2 each independently represents an aryloxy group which may have a substituent. A methacrylic acid ester is anionically polymerized in the presence of an organoaluminum compound (C) represented by AlR 2 R 3 R 4 (II) (wherein, R 2 , R 3 and R 4 and each independently represent hydrogen, a saturated hydrocarbon group which may have a substituent, or an aromatic hydrocarbon group which may have a substituent. [2] The method according to [1], wherein the Lewis base (A) is a polyamine compound (A1). [3] The method according to [2], wherein the polyamine compound (A1) is at least one selected from N,N,N',N'-tetramethylethylenediamine, N,N,N',N",N"-pentamethyldiethylenetriamine, and 1,1,4,7,10,10-hexamethyltriethylenetetraamine. [4] The method according to [1], wherein the Lewis base (A) is an ether compound (A2). [5] The method according to [4], wherein the ether compound (A2) is a non-cyclic ether compound (A2-1) having one or more ether bonds in the molecule or a cyclic ether compound (A2-2) having two or more ether bonds in the molecule. [6] The method according to any one of [1] to [5], wherein the organoaluminum compound (C) is isobutylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum. [7] The method according to any one of [1] to [6], wherein the aluminum compound (D) is at least one selected from trimethylaluminum, triethylaluminum, and triisobutylaluminum. [Effects of the Invention]

[0008] According to the present invention, a (meth)acrylic acid ester polymer having high molecular weight uniformity can be produced with high polymerization initiation efficiency without impairing the inherent properties of the (meth)acrylic acid ester polymer, such as transparency. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below. In this specification, "(meth)acrylic acid ester" is a general term for "methacrylic acid ester" and "acrylic acid ester", "(meth)acrylic" is a general term for "methacrylic" and "acrylic", and "(meth)acryloyl" is a general term for "methacryloyl" and "acryloyl".

[0010] The Lewis base (A) used in the present invention is not particularly limited as long as it is effective for producing a (meth)acrylic acid ester polymer. The Lewis base (A) is preferably at least one Lewis base selected from the group consisting of polyamine compounds (A1) and ether compounds (A2).

[0011] The polyamine compound (A1) is a compound having two or more amine structures in the molecule, and can be used without any particular limitation as long as it does not adversely affect the polymerization reaction. In the present invention, the term "amine structure" refers to a partial chemical structure in which two or three carbon atoms are bonded to one nitrogen atom. When a nitrogen atom is bonded to two carbon atoms, one is a nitrogen-carbon single bond and the other is a nitrogen-carbon double bond, and both the nitrogen atom and the carbon atom are ring atoms of a nitrogen-containing aromatic ring. Furthermore, the two or three carbon atoms bonded to the nitrogen atom may constitute part of the aromatic ring.

[0012] Examples of the polyamine compound (A1) include chain polyamine compounds such as N,N,N',N'-tetramethylethylenediamine, N,N,N'N'-tetraethylethylenediamine, N,N,N',N",N"-pentamethyldiethylenetriamine, 1,1,4,7,10,10-hexamethyltriethylenetetraamine, and tris[2-(dimethylamino)ethyl]amine; 1,3,5-trimethylhexahydro-1,3,5-triazine, 1,4,7-trimethyl-1,4,7-triazacyclononane, and 1,4,7,10,13,16-hexamethyl-1,4 and aromatic heterocyclic compounds such as 2,2'-bipyridyl and 2,2':6',2"-terpyridine. Among the polyamine compounds (A1), from the viewpoints of polymerization initiation efficiency and maintaining high living properties during polymerization, chain polyamine compounds are preferred, and N,N,N',N'-tetramethylethylenediamine, N,N,N',N",N"-pentamethyldiethylenetriamine, and 1,1,4,7,10,10-hexamethyltriethylenetetraamine are more preferred.

[0013] It is not preferable to use a tertiary monoamine compound such as triethylamine instead of the Lewis base (A) because it reduces the polymerization initiation efficiency and the living property during polymerization. The polyamine compound (A1) may be used alone or in combination of two or more.

[0014] The ether compound (A2) has an ether bond (-O-) in the molecule and does not contain a metal component, and can be used without any particular limitation as long as it does not adversely affect the polymerization reaction. As the ether compound (A2), from the viewpoints of high polymerization initiation efficiency and high living property during polymerization, a non-cyclic ether compound (A2-1) having one or more ether bonds in the molecule or a cyclic ether compound (A2-2) having two or more ether bonds in the molecule is preferred.

[0015] Examples of the acyclic ether compound (A2-1) having one or more ether bonds in the molecule include acyclic monoether compounds such as dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, and anisole; 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-diisopropoxyethane, 1,2-dibutoxyethane, 1,2-diphenoxyethane, 1,2-dimethoxypropane, 1,2-diethoxypropane, and 1,2-diphenylpropane. - Acyclic diether compounds such as diisopropoxypropane, 1,2-dibutoxypropane, 1,2-diphenoxypropane, 1,3-dimethoxypropane, 1,3-diethoxypropane, 1,3-diisopropoxypropane, 1,3-dibutoxypropane, 1,3-diphenoxypropane, 1,4-dimethoxybutane, 1,4-diethoxybutane, 1,4-diisopropoxybutane, 1,4-dibutoxybutane, and 1,4-diphenoxybutane; diethylene acyclic triether compounds such as glycol dimethyl ether, dipropylene glycol dimethyl ether, dibutylene glycol dimethyl ether, diethylene glycol diethyl ether, dipropylene glycol diethyl ether, and dibutylene glycol diethyl ether; and dialkyl ethers of polyalkylene glycols such as triethylene glycol dimethyl ether, tripropylene glycol dimethyl ether, tributylene glycol dimethyl ether, triethylene glycol diethyl ether, tripropylene glycol diethyl ether, tributylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetrapropylene glycol dimethyl ether, tetrabutylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetrapropylene glycol diethyl ether, and tetrabutylene glycol diethyl ether. Examples of the cyclic ether compound (A2-2) having two or more ether bonds in the molecule include dioxane, and crown ethers such as 12-crown-4, 15-crown-5, and 18-crown-6.

[0016] Among the above ether compounds (A2), the non-cyclic ether compounds (A2-1) are preferred, and diethyl ether and 1,2-dimethoxyethane are more preferred, in view of the fact that the effects of the present invention are particularly pronounced and that they are readily available.

[0017] In addition, when a cyclic ether compound having one ether bond in the molecule, such as an epoxy compound such as tetrahydrofuran or propylene oxide, is used as the ether compound (A2), the interaction with the organoaluminum compound (C) is too strong, and it may react directly with the organolithium compound (B) or the growing living polymer. Therefore, it is usually preferable to avoid using a cyclic ether compound having one ether bond in the molecule as the Lewis base (A). The above ether compounds (A2) may be used singly or in combination of two or more.

[0018] The Lewis base (A) may be a compound having one or more ether bonds and one amine structure in the molecule, or a compound having one or more ether bonds and two or more amine structures in the molecule. Compounds having one or more ether bonds and one amine structure in the molecule can be classified as the ether compound (A2), and compounds having one or more ether bonds and two or more amine structures in the molecule can be classified as the polyamine compound (A1).

[0019] The Lewis base (A) may be used singly or in combination of two or more kinds. Thus, a mixture of the polyamine compound (A1) and the ether compound (A2) may be used.

[0020] The organolithium compound (B) used in the present invention is preferably an organolithium compound containing one or more carbon atoms serving as an anion center in the molecule and having the same number of lithium cations as the anion centers as counter ion centers. Focusing on the carbon atom at the anion center, organolithium compounds (B) can be classified into three types: organolithium compounds (B1) having a chemical structure with a tertiary carbon atom as the anion center, organolithium compounds (B2) having a chemical structure with a secondary carbon atom as the anion center, and organolithium compounds (B3) having a chemical structure with a primary carbon atom as the anion center.

[0021] Examples of the organolithium compound (B1) having a chemical structure with a tertiary carbon atom as the anion center include t-alkyllithiums such as t-butyllithium and 1,1-dimethylpropyllithium; 1,1-diarylalkyllithiums such as 1,1-diphenylhexyllithium and 1,1-diphenyl-3-methylpentyllithium; and α,α-dialkyl-α-lithioacetic acid esters such as ethyl α-lithioisobutyrate, butyl α-lithioisobutyrate, and methyl α-lithioisobutyrate.

[0022] Examples of the organolithium compound (B2) having a chemical structure with a secondary carbon atom as the anion center include sec-alkyllithiums such as isopropyllithium, 1-methylpropyllithium (sec-butyllithium), 1-methylbutyllithium, 2-ethylpropyllithium, and 1-methylpentyllithium; cycloalkyllithiums such as cyclohexyllithium; diarylmethyllithiums such as diphenylmethyllithium; and 1-alkyl-1-arylmethyllithiums such as α-methylbenzyllithium.

[0023] Examples of the organolithium compound (B3) having a chemical structure in which a primary carbon atom serves as the anion center include n-alkyllithium such as methyllithium, propyllithium, n-butyllithium, and n-pentyllithium.

[0024] Among the above-mentioned organolithium compounds (B), in terms of achieving both convenience in industrial use (low risk of fire, ease of handling, ease of production, etc.) and high polymerization initiation ability, organolithium compounds (B2) having a chemical structure in which a secondary carbon atom serves as the anion center are preferred, lithium salts of hydrocarbons having 3 to 40 carbon atoms and having a chemical structure in which a secondary carbon atom serves as the anion center are more preferred, and 1-methylpropyllithium (sec-butyllithium) is particularly preferred.

[0025] The organolithium compounds (B) may be used alone or in combination of two or more.

[0026] In the production method of the present invention, it is important that the methacrylic acid ester is anionically polymerized in the polymerization system in the presence of at least one Lewis base (A), an organolithium compound (B), and an organoaluminum compound (C), and then the methacrylic acid ester or the acrylic acid ester is further polymerized in the presence of a specific aluminum compound (D). In a preferred embodiment of the present invention, at least one Lewis base (A), an organolithium compound (B), and an organoaluminum compound (C) are mixed, if necessary, in the presence of a solvent, and a methacrylic acid ester is added to the mixture to polymerize it. Thereafter, an aluminum compound (D) and a (meth)acrylic acid ester are added to the reaction mixture to polymerize it further. The aluminum compound (D) and the (meth)acrylic acid ester are preferably added in this order.

[0027] The organoaluminum compound (C) may, for example, be an oxygen-containing organoaluminum compound represented by the following general formula (I). AlR 1 OAr 1 OAr 2 (I) (In the above formula (I), R 1 represents a saturated hydrocarbon group which may have a substituent, or an aromatic hydrocarbon group which may have a substituent, and OAr 1 and OAr 2each independently represents an aryloxy group which may have a substituent.

[0028] R 1 Examples of saturated hydrocarbon groups that can be represented include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, a 2-methylbutyl group, a 3-methylbutyl group, an n-octyl group, and a 2-ethylhexyl group; and cycloalkyl groups such as a cyclohexyl group.

[0029] R 1 Examples of aromatic hydrocarbon groups that can be represented include aryl groups such as a phenyl group; and aralkyl groups such as a benzyl group.

[0030] Examples of the substituents that these saturated hydrocarbon groups and aromatic hydrocarbon groups may have include alkoxy groups such as methoxy, ethoxy, isopropoxy, and t-butoxy; halogen atoms such as chlorine and bromine atoms; etc. The number of substituents in a substituted saturated hydrocarbon group or a substituted aromatic hydrocarbon group is preferably 1 to 3, and more preferably 1 to 2.

[0031] OAr 1 and OAr 2 Examples of the optionally substituted aryloxy group that can be represented by the formula (I) include aryloxy groups that do not have a substituent, such as a phenoxy group, a 2-methylphenoxy group, a 4-methylphenoxy group, a 2,6-dimethylphenoxy group, a 2,4-di-t-butylphenoxy group, a 2,6-di-t-butylphenoxy group, a 2,6-di-t-butyl-4-methylphenoxy group, a 2,6-di-t-butyl-4-ethylphenoxy group, a 2,6-diphenylphenoxy group, a 1-naphthoxy group, a 2-naphthoxy group, a 9-phenanthryloxy group, and a 1-pyrenyloxy group; and aryloxy groups that have a substituent, such as a 7-methoxy-2-naphthoxy group.

[0032] OAr 1 and OAr 2and (S)-(-)-1,1'-bi-2-naphthol, etc., include groups in which hydrogen atoms in two phenolic hydroxyl groups are removed.

[0033]

[0047] Examples of the one or more substituents that the aryloxy group which may have the above-mentioned substituent and the arylenedioxy group which may have the above-mentioned substituent may have include alkoxy groups such as a methoxy group, an ethoxy group, an isopropoxy group, and a t-butoxy group; and halogen atoms such as chlorine and bromine.

[0034] In addition, OAr in general formula (I) 1 and OAr 2 may have the same chemical structure or different chemical structures as long as they are within the above-defined range.

[0035] Examples of the organoaluminum compound (C) include ethylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum, ethylbis(2,6-di-t-butylphenoxy)aluminum, ethyl[2,2'-methylenebis(4-methyl-6-t-butylphenoxy)]aluminum, isobutylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum, isobutylbis(2,6-di-t-butylphenoxy)aluminum, and isobutyl[2,2'-methylenebis(4-methyl-6-t-butylphenoxy)]aluminum. ))]aluminum, n-octylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum, n-octylbis(2,6-di-t-butylphenoxy)aluminum, n-octyl[2,2'-methylenebis(4-methyl-6-t-butylphenoxy)]aluminum, phenylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum, and benzylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum.

[0036] The atomic group directly bonded to aluminum in the aluminum compound (D) does not contain an aryloxy group, and therefore the polymerization solution after polymerization termination does not contain phenols derived from the aluminum compound (D), and therefore does not contain any substances that cause yellowing of the polymer, and therefore a highly transparent (meth)acrylic acid ester polymer can be obtained.

[0037] The aluminum compound (D) may, for example, be an aluminum compound represented by the following general formula (II). AlR 2 R 3 R 4 (II) (In the above formula (II), R 2 , R 3 and R 4 are each independently hydrogen, a saturated hydrocarbon group which may have a substituent, or an aromatic hydrocarbon group which may have a substituent.

[0038] R 2 , R 3 and R 4 Examples of the optionally substituted saturated hydrocarbon group that can be represented by include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, a 2-methylbutyl group, a 3-methylbutyl group, an n-octyl group, and a 2-ethylhexyl group; and cycloalkyl groups such as a cyclohexyl group.

[0039] R 2 , R 3 and R 4 Examples of the aromatic hydrocarbon group which may have a substituent include aryl groups such as a phenyl group; and aralkyl groups such as a benzyl group.

[0040] Examples of the one or more substituents that these saturated hydrocarbon groups and aromatic hydrocarbon groups may have include alkoxy groups such as methoxy, ethoxy, isopropoxy, and t-butoxy; and halogen atoms such as chlorine and bromine.

[0041] Examples of the aluminum compound (D) include trimethylaluminum, triethylaluminum, tri(n-butyl)aluminum, triisobutylaluminum, tri(n-hexyl)aluminum, tri(n-octyl)aluminum, diisobutylaluminum hydride, triphenylaluminum, and tribenzylaluminum.

[0042] Among the above aluminum compounds (D), trimethylaluminum and triisobutylaluminum are preferred, with triisobutylaluminum being particularly preferred, from the viewpoints of availability and economy.

[0043] The methacrylic acid ester used in the present invention is not particularly limited as long as it has anionic polymerizability. Examples of methacrylic acid esters include monofunctional methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, vinyl methacrylate, allyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, glycidyl methacrylate, trimethoxysilylpropyl methacrylate, methoxyethyl methacrylate, N,N-dimethylaminoethyl methacrylate, and N,N-diethylaminoethyl methacrylate.

[0044] The acrylic acid ester used in the present invention is not particularly limited as long as it has anionic polymerizability. Examples of acrylic acid esters include monofunctional acrylic acid esters such as methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, vinyl acrylate, allyl acrylate, n-butyl acrylate, t-butyl acrylate, cyclohexyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, glycidyl acrylate, trimethoxysilylpropyl acrylate, methoxyethyl acrylate, N,N-dimethylaminoethyl acrylate, and N,N-diethylaminoethyl acrylate.

[0045] The (meth)acrylic acid esters may be used alone or in combination of two or more. In addition to the monofunctional (meth)acrylic acid esters exemplified above, other anionically polymerizable monomers may be used in combination. When an anionically polymerizable monomer other than a monofunctional (meth)acrylic acid ester (hereinafter abbreviated as "other anionically polymerizable monomer") is used, the proportion of structural units derived from the other anionically polymerizable monomer in the (meth)acrylic acid ester polymer obtained by the production method of the present invention is preferably 1 to 50 mol %, more preferably 3 to 20 mol %. Furthermore, the proportion of the other anionically polymerizable monomer is preferably 1 to 50 mol %, more preferably 3 to 20 mol %, during polymerization in the presence of a Lewis base (A), an organolithium compound (B), and an organoaluminum compound (C), and is preferably 1 to 50 mol %, more preferably 3 to 20 mol %, during polymerization in the presence of an aluminum compound (D).

[0046] Examples of such anionic polymerizable monomers other than monofunctional (meth)acrylic acid esters include polyfunctional (meth)acrylic acid esters having two or more (meth)acryloyl groups, such as 2-methylpropane-1,2-diol dimethacrylate, 1,1-dimethylpropane-1,3-diol dimethacrylate, 2-methylpropane-1,2-diol diacrylate, and 1,1-dimethylpropane-1,3-diol diacrylate.

[0047] The methacrylic acid ester polymerized before the presence of the aluminum compound (D) and the (meth)acrylic acid ester polymerized in the presence of the aluminum compound (D) may be the same or different.

[0048] In addition, a block copolymer having a plurality of polymer blocks can be produced by anionic polymerization of a combination of two or more (meth)acrylic acid esters, typically by sequential polymerization of (meth)acrylic acid esters corresponding to the respective polymer blocks.

[0049] It is preferable to thoroughly dry the (meth)acrylic acid ester and other anionically polymerizable monomers used as needed in advance under a stream of inert gas such as nitrogen gas, etc., in order to ensure smooth progress of the polymerization reaction. The drying treatment can be carried out using a dehydrating / desiccating agent such as calcium hydride, molecular sieves, or activated alumina.

[0050] The amount of the Lewis base (A) used can be appropriately set depending on the reaction conditions and the like. From the viewpoints of high polymerization initiation efficiency, high living property during polymerization, and the like, the molar ratio of the Lewis base (A) to the organolithium compound (B) is preferably 0.1 times or more, more preferably 0.3 times or more, and even more preferably 0.5 times or more. The Lewis base (A) can also be used as a solvent, but in order to avoid a significant decrease in the polymerization initiation efficiency, it is generally preferable to limit the amount of the Lewis base (A) used to 95 mass % or less based on the total mass of the polymerization system.

[0051] The amount of the organolithium compound (B) used can be appropriately set depending on the monomers used, the degree of polymerization of the target polymer, etc., but it is preferably 0.01 to 10 moles per 100 moles of the total of the anionically polymerizable monomers including the (meth)acrylic acid ester, in order to enable smooth production of the target polymer.

[0052] The amount of the organoaluminum compound (C) used can be appropriately set depending on the type of polymerization operation, the type of solvent constituting the polymerization system in the case of solution polymerization, and other various polymerization conditions, etc. The amount of the organoaluminum compound (C) used is usually preferably in the range of 0.3 to 300 mol, more preferably 1 to 100 mol, per mol of the organolithium compound (B).

[0053] The amount of the aluminum compound (D) used can be appropriately determined depending on the type of polymerization operation, the type of solvent constituting the polymerization system when solution polymerization is carried out, and other various polymerization conditions. The amount of the aluminum compound (D) used is preferably in the range of 0.1 to 100 mol, more preferably in the range of 1 to 20 mol, per 1 mol of the organoaluminum compound (C).

[0054] The aluminum compound (D) is added after anionic polymerization of the methacrylic acid ester in the presence of the Lewis base (A), organolithium compound (B), and organoaluminum compound (C) in the polymerization system. The degree of polymerization of the methacrylic acid ester polymer before the addition of the aluminum compound (D) can be appropriately set depending on the degree of polymerization of the target (meth)acrylic acid ester polymer, but is preferably 1 to 500. If the degree of polymerization is less than 1, the molecular weight uniformity will be low or the polymerization initiation efficiency will be low. If the degree of polymerization exceeds 500, productivity will be poor.

[0055] The number of moles of the (meth)acrylic acid ester monomer added after the addition of the aluminum compound (D) is preferably in the range of 1 to 10,000 moles, more preferably in the range of 1 to 5,000 moles, per mole of the methacrylic acid ester monomer polymerized before the addition of the aluminum compound (D).

[0056] The production method of the present invention can employ any polymerization method, such as solution polymerization, bulk polymerization, or precipitation polymerization. Solution polymerization in an organic solvent is preferred because it allows for control of the polymerization temperature, uniformity of conditions within the polymerization system, and smooth progression of polymerization. While the organic solvent is not particularly limited, aromatic hydrocarbon solvents such as toluene, ethylbenzene, and xylene; saturated hydrocarbon solvents such as hexane, cyclohexane, and methylcyclohexane; halogenated hydrocarbon solvents such as chloroform, methylene chloride, and carbon tetrachloride; and ester solvents such as dimethyl phthalate are generally preferred because of their relatively high safety during handling, their low risk of contamination with wastewater, and ease of solvent recovery and purification. These organic solvents may be used alone or in combination of two or more.

[0057] When an organic solvent is used in the production method of the present invention, the amount used can be adjusted appropriately depending on the degree of polymerization of the target polymer, the type of monomer, the type of Lewis base (A) used, the type of organolithium compound (B), the type of organoaluminum compound (C), the type of aluminum compound (D), the type of organic solvent, etc. From the viewpoints of smooth progress of polymerization, ease of separation and recovery of the produced polymer, reduction of the burden of waste liquid treatment, etc., it is generally preferable to use an organic solvent in the range of 200 to 3000 parts by weight per 100 parts by weight of the anionically polymerizable monomer containing a (meth)acrylic acid ester used.

[0058] In the production method of the present invention, in order to maintain high polymerization initiation efficiency, it is preferable to contact the Lewis base (A) with the organoaluminum compound (C) before contacting it with the organolithium compound (B). The organoaluminum compound (C) may be added to the polymerization system prior to the anionically polymerizable monomer containing a (meth)acrylic acid ester, or may be added to the polymerization system simultaneously with the monomer. Furthermore, in the latter case, the organoaluminum compound (C) and the monomer may be mixed in advance and added in the form of a mixture.

[0059] In the production method of the present invention, the aluminum compound (D) may be added to the polymerization system simultaneously with the anionically polymerizable monomer containing a (meth)acrylic acid ester, or the aluminum compound (D) and the anionically polymerizable monomer may be mixed in advance and added in the form of a mixture.

[0060] The production method of the present invention can produce copolymers when two or more (meth)acrylic acid esters, or one or more (meth)acrylic acid esters and one or more other anionically polymerizable monomers are used. In this case, as with conventional anionic polymerization, any copolymerization form, such as random, block, or tapered block, can be produced depending on the monomer addition method (e.g., whether two or more monomers are added simultaneously or separately at intervals), the combination of monomer types, etc. The production method of the present invention can exhibit high living properties, making it suitable for producing block copolymers that require high blocking efficiency.

[0061] In the production method of the present invention, other known additives may be added to the polymerization system as needed, in accordance with known anionic polymerization techniques, such as inorganic salts (e.g., lithium chloride), metal alkoxide compounds (e.g., lithium methoxyethoxyethoxide, potassium t-butoxide), and organic quaternary salts (e.g., tetraethylammonium chloride, tetraethylphosphonium bromide).

[0062] In the production method of the present invention, the polymerization temperature may be selected appropriately depending on the type of (meth)acrylic acid ester used, etc. In many cases, the polymerization temperature is preferably in the range of -60°C to +100°C, more preferably in the range of -30°C to +50°C. Furthermore, when polymerizing an acrylic acid ester, if the polymerization temperature is too low, the stereoregularity of the resulting polymer increases. Therefore, if the objective is to produce an acrylic acid ester polymer with excellent flexibility, the polymerization temperature is preferably -50°C or higher. Furthermore, in the anionic polymerization method of the present invention, the cooling conditions for the polymerization system can be relaxed compared to conventional anionic polymerization methods, and high living properties can be achieved even when polymerization is carried out at temperatures closer to room temperature.

[0063] The production method of the present invention is preferably carried out under an atmosphere of an inert gas such as nitrogen, argon, or helium. Furthermore, in the anionic polymerization method of the present invention, polymerization is preferably carried out under sufficient stirring conditions so that the polymerization system becomes uniform. In the production method of the present invention, the polymerization time can be appropriately set depending on the molecular weight of the polymer, etc., but it is possible to proceed with polymerization at a higher rate than conventional polymerization methods. Depending on the polymerization conditions employed, for example, polymerization of methacrylic acid esters can be completed within several minutes, and polymerization of acrylic acid esters can be completed within several tens of seconds. Therefore, in the production method of the present invention, anionic polymerization can also be carried out using a tubular continuous polymerization apparatus that is highly productive and has good cooling efficiency.

[0064] In the production method of the present invention, the polymerization reaction can be terminated by adding a polymerization terminator to the reaction mixture at the stage when the target polymer chain is formed, in accordance with known anionic polymerization methods. Examples of polymerization terminators that can be used include protic compounds such as methanol, acetic acid, and a methanol solution of hydrochloric acid. The amount of polymerization terminator used can be appropriately determined depending on the amount of active terminals in the polymer, but is generally preferably within the range of 1 to 100 moles per mole of the organolithium compound (B).

[0065] In the production method of the present invention, a terminal functional group imparting agent (e.g., aldehyde, lactone, carbon dioxide, etc.) may be added to the reaction system after the completion of all the polymerization steps but before the addition of the polymerization terminator. In this case, a polymer having functional groups such as hydroxyl groups or carboxyl groups at the molecular chain ends can be obtained. If metal components derived from the organolithium compound (B), organoaluminum compound (C), and aluminum compound (D) remain in the polymer separated from the reaction mixture after polymerization termination, they may cause deterioration in the physical properties of the polymer and materials using it, poor transparency, etc. Therefore, depending on the intended use of the polymer, it is preferable to remove the metal compounds derived from the organolithium compound (B), organoaluminum compound (C), and aluminum compound (D) after the polymerization is completed. Effective methods for removing the metal compounds include subjecting the polymer to cleaning treatments such as washing with an acidic aqueous solution or adsorption treatment using an adsorbent such as an ion exchange resin. Examples of acidic aqueous solutions that can be used include hydrochloric acid, sulfuric acid, nitric acid, acetic acid, propionic acid, and citric acid.

[0066] The method for separating and obtaining the polymer from the reaction mixture after terminating the polymerization is not particularly limited, and any method based on known methods can be used. Examples of the method for separating and obtaining the polymer include a method of pouring the reaction mixture into a poor solvent for the polymer to precipitate the polymer, and a method of distilling off the solvent from the reaction mixture to obtain the polymer.

[0067] Furthermore, according to the present invention, polymers of any molecular weight can be produced. While the molecular weight of the polymers that can be produced varies over a wide range, a number-average molecular weight (Mn) in the range of 1,000 to 1,000,000 is generally preferred in terms of the handleability, flowability, and mechanical properties of the resulting polymer. Furthermore, according to the present invention, polymers with high molecular weight uniformity (i.e., narrow molecular weight distribution) can usually be obtained, and it is possible to produce polymers with a molecular weight distribution (Mw (weight-average molecular weight) / Mn (number-average molecular weight)) of 1.5 or less. However, by controlling the rate of addition of the anionically polymerizable monomer to the polymerization system, the rate of diffusion of the monomer within the polymerization system, and the like, it is also possible to intentionally obtain polymers with a broad molecular weight distribution. [Example]

[0068] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way. The various physical properties in the examples and comparative examples were measured or evaluated by the following methods. In the following examples, chemicals were dried and purified by conventional methods and degassed with nitrogen before use. Chemicals were transferred and supplied under a nitrogen atmosphere.

[0069] "Polymerization conversion rate" A Shimadzu GC-2014A gas chromatograph was connected to an Agilent Technologies, Inc. DB-1 column (df = 1.0 μm, 0.25 mm I.D. x 60 m). Measurements were performed under the following conditions: injection temperature 250°C, detector temperature 300°C, column temperature 60°C (held for 2 minutes) at a rate of 10°C / min to 100°C, and then at a rate of 30°C / min to 250°C. The polymerization conversion was calculated based on the results. n-Decane was used as an internal standard.

[0070] "Weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw / Mn)" The weight-average molecular weight, number-average molecular weight, and molecular weight distribution of the polymers obtained in the examples and comparative examples described below were determined in terms of polystyrene equivalent molecular weight by gel permeation chromatography (hereinafter abbreviated as GPC). Apparatus: Tosoh Corporation GPC apparatus "HLC-8220" Separation column: Two TSK-gel SuperMultiporeHZ-M columns (column diameter: 4.6 mm, column length: 15 cm) manufactured by Tosoh Corporation connected in series Eluent: tetrahydrofuran Eluent flow rate: 0.36 mL / min Column temperature: 40℃ Detection method: Refractive index (RI)

[0071] "Polymerization initiation efficiency" The polymerization initiation efficiency (F1) was calculated from the Mn of the obtained polymer (referred to as Mn(R1)) and the Mn of the polymer obtained when the polymerization initiation efficiency is 100% (calculated value: referred to as Mn(I1)) using the following formula. F1 = Mn(I1) / Mn(R1) Mn(I1) was calculated by the following formula, where M1 is the molecular weight of the methacrylic acid ester monomer used, N1 is the number of moles of the methacrylic acid ester used per mole of the organolithium compound (B) used, M2 is the molecular weight of the (meth)acrylic acid ester monomer used, and N2 is the number of moles of the (meth)acrylic acid ester used per mole of the organolithium compound (B) used. Mn(I1) = M1 × N1 + M2 × N2 When F1 was 0.85 or more, the polymerization initiation efficiency was evaluated as high and marked with "+", and when it was less than 0.85, the polymerization initiation efficiency was evaluated as low and marked with "-".

[0072] "Uniformity of molecular weight" Regarding the molecular weight distribution of the polymers obtained in the examples and comparative examples described below, if the molecular weight distribution was 1.5 or less, it was evaluated as "+" indicating high molecular weight uniformity, and if it was more than 1.5, it was evaluated as "-" indicating low molecular weight uniformity.

[0073] "Yellowness measurement" Yellowness index (YI) was measured using a Nippon Denshoku color computer SD 7000. When YI was 3.0 or less, the yellowness was evaluated as low and marked with "+", and when it was over 3.0, the yellowness was evaluated as high and marked with "-".

[0074] [Example 1] (Procedure 1) A 1 L four-neck flask was equipped with a flat-blade disk stirrer. After purging the atmosphere with argon, 200 g of toluene was added and cooled to 0 °C using a methanol bath. 1.18 g (5.12 mmol) of 1,1,4,7,10,10-hexamethyltriethylenetetraamine and 16.2 mL (7.29 mmol) of a toluene solution containing 0.45 mol / L of isobutylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum were added. 4.00 mL (4.88 mmol) of a cyclohexane / hexane solution containing 1.22 mol / L of sec-butyllithium was added and stirred for 10 minutes. 14.65 g (146 mmol) of methyl methacrylate was added dropwise to the vigorously stirred solution at 0 °C. A portion of the solution was sampled and poured into methanol, and the resulting white precipitate (PMMA) was collected and dissolved in tetrahydrofuran. Measurement by GPC revealed that the Mn was 3,000. Next, 1.45 g (7.31 mmol) of triisobutylaluminum was added, followed by the dropwise addition of 58.63 g (586 mmol) of methyl methacrylate. A portion of the resulting solution was sampled 10 minutes after all of the methyl methacrylate had been added dropwise, and the polymerization conversion rate was measured by gas chromatography, which was found to be 99.8%. (Procedure 2) 50 g of the resulting solution was poured into 250 g of methanol, and the resulting white precipitate (PMMA) was recovered and dissolved in tetrahydrofuran. Measurement by GPC revealed that Mn was 15,600, Mw / Mn was 1.10 (molecular weight uniformity: "+"). The polymerization initiation efficiency was 0.96 ("+"). The white precipitate was dissolved in chloroform to prepare a cast film (thickness: 0.05 mm). The obtained film was irradiated with 5,000 mJ / cm 2 using a high-pressure mercury lamp (output: 3 kW) at 25°C. 2 The film was irradiated with ultraviolet light. After irradiation, the yellowness index of the film was measured using a color computer, and the result was YI=0.94 (yellowness index: "+").

[0075] [Example 2] After the procedure 1 of Example 1, 219.86 g (2196 mmol) of methyl methacrylate was further added dropwise. A portion of the resulting solution was sampled 10 minutes after all of the methyl methacrylate had been added dropwise, and the polymerization conversion rate was measured by gas chromatography, which was found to be 99.8%. 50 g of the resulting solution was poured into 250 g of methanol, and the resulting white precipitate (PMMA) was recovered and dissolved in tetrahydrofuran. Measurement by GPC revealed that Mn was 63,100, Mw / Mn was 1.12 (molecular weight uniformity: "+"), and the polymerization initiation efficiency was 0.95 ("+"). The white precipitate was dissolved in chloroform to prepare a cast film (thickness: 0.05 mm). The obtained film was irradiated with 5,000 mJ / cm 2 using a high-pressure mercury lamp (output: 3 kW) at 25°C. 2 The film was irradiated with ultraviolet light. After the irradiation, the yellowness of the film was measured using a color computer, and the result was YI=0.95 (yellowness index: "+").

[0076] [Comparative Example 1] The polymerization and polymerization termination procedures were carried out in the same manner as in Example 1, except that the 0.45 mol / L toluene solution of isobutylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum used in Example 1 was adjusted to 32.4 mL (14.6 mmol) and no triisobutylaluminum was added. The polymerization conversion was 99.9%. The Mn was 15,300, the Mw / Mn was 1.09 (molecular weight uniformity: "+"), and the polymerization initiation efficiency was 0.98 ("+"). The YI was 5.3 (yellowness index: "-").

[0077] Comparative Example 2 The polymerization and polymerization termination procedures were carried out in the same manner as in Example 1, except that triisobutylaluminum was added after the dropwise addition of sec-butyllithium and before the dropwise addition of methyl methacrylate. The polymerization conversion was 99.8%. Mn was 24,500, Mw / Mn was 1.67 (uniformity of molecular weight: "-"), and the polymerization initiation efficiency was 0.61 ("-"). Furthermore, YI was 1.0 (yellowness index: "+"). [Industrial Applicability]

[0078] According to the present invention, a (meth)acrylic acid ester polymer having low yellowness and high uniformity in molecular weight can be produced with high polymerization initiation efficiency.

Claims

1. In the polymerization system, at least one Lewis base (A), an organolithium compound (B), and AlR １ OAr １ OAr ２ (I) (wherein, R １ represents a saturated hydrocarbon group which may have a substituent, or an aromatic hydrocarbon group which may have a substituent, OAr １ and OAr ２ and (C) an organoaluminum compound (C) represented by AlR ２ R ３ R ４ (II) (wherein R ２ , R ３ and R ４ and each independently represent hydrogen, a saturated hydrocarbon group which may have a substituent, or an aromatic hydrocarbon group which may have a substituent), and further polymerize a (meth)acrylic acid ester in the presence of an aluminum compound (D), The method for producing a (meth)acrylic acid ester polymer, wherein the Lewis base (A) is a polyamine compound (A1).

2. 2. The method according to claim 1, wherein the polyamine compound (A1) is at least one selected from the group consisting of N,N,N',N'-tetramethylethylenediamine, N,N,N',N",N"-pentamethyldiethylenetriamine, and 1,1,4,7,10,10-hexamethyltriethylenetetraamine.

3. 3. The process according to claim 1, wherein the organoaluminum compound (C) is isobutylbis(2,6-di-t-butyl-4-methylphenoxy)aluminum.

4. The method according to any one of claims 1 to 3, wherein the aluminum compound (D) is at least one selected from the group consisting of trimethylaluminum, triethylaluminum, and triisobutylaluminum.