Method for producing (METH)acrylic ester, (METH)acrylic ester composition, and (METH)acrylic polymer

Abstract

To provide a (meth)acrylic ester that exhibits reduced coloration through a simple process.SOLUTION: A method for producing a (meth)acrylic ester according to the present invention comprises: causing methyl (meth)acrylate and an alcohol to undergo a transesterification reaction in the presence of a catalyst, to obtain a reaction solution containing a (meth)acrylic ester; and bringing the reaction solution into contact with an adsorbent containing aluminum oxide and silicon dioxide within the same particle. In one example, the APHA value, which represents the Hazen color number, may be 100 or less.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] (Meth)acrylic polymers obtained using (meth)acrylic acid esters are used in various fields such as paints, adhesives, resin modifiers, artificial marble, paper latex, etc. For example, the target (meth)acrylic acid alkyl ester can be produced by utilizing a transesterification reaction between the raw material (meth)acrylic acid alkyl ester and alkyl alcohol in the presence of the catalyst Ti(OR)4 (R is an alkyl group) (Patent Document 1).

[0003] Since transparency is often required for the applications of (meth)acrylic acid esters, it is important to remove coloring impurities (for example, Patent Documents 2 and 3). Patent Document 2 discloses treating a solution containing polytetramethylene ether glycol di(meth)acrylate with at least one adsorbent selected from the group consisting of basic alumina, basic ion exchange resins, and synthetic adsorbents. Patent Document 3 discloses that a reaction liquid containing polytetramethylene ether glycol di(meth)acrylate is simultaneously contacted with diatomaceous earth and basic alumina in the presence of water. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-274986 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-12551 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-189415 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the examples of Patent Document 2, the treatment to reduce coloring is cumbersome, as in the case of washing with a 10% aqueous sodium hydroxide solution before treatment with basic alumina. Also, in the examples of Patent Document 3, the water content is reduced before the addition of tetra-n-butyl titanate, and then water is added for the treatment to reduce coloring. Therefore, the treatment to reduce coloring is cumbersome.

[0006] The present invention primarily provides a production method that enables a (meth)acrylic acid ester with reduced coloration to be obtained by a simple method. [Means for solving the problem]

[0007] The present invention has the following aspects. [1] A method for producing a (meth)acrylic acid ester, A method for producing a reaction liquid containing a (meth)acrylic acid ester by subjecting methyl (meth)acrylate and an alcohol to a transesterification reaction in the presence of a catalyst; contacting the reaction solution with an adsorbent containing aluminum oxide and silicon dioxide in the same particle; A manufacturing method comprising: [2] The method according to [1], wherein the transesterification reaction is carried out in the presence of a titanium catalyst. [3] The method according to [2], wherein the amount of the adsorbent used is 0.35 to 5.00 kg per 1 mol of the titanium catalyst contained in the reaction solution when the adsorbent is brought into contact with the reaction solution. [4] The production method according to any one of [1] to [3], wherein the temperature of the reaction liquid when the reaction liquid is brought into contact with the adsorbent is 40 to 100°C. [5] The method according to any one of [1] to [4], wherein the alcohol comprises a diol which may have an etheric oxygen atom. [6] The methyl (meth)acrylate and the diol are subjected to a transesterification reaction to produce at least one selected from the group consisting of a mono(meth)acrylic acid ester and a di(meth)acrylic acid ester; [5] The production method according to [5], wherein the reaction solution is brought into contact with the adsorbent when the proportion of the mono(meth)acrylic acid ester becomes 20 mass% or less of the total amount of the diol, the mono(meth)acrylic acid ester, and the di(meth)acrylic acid ester. [7] The method according to any one of [1] to [6], wherein silica alumina is used as the adsorbent.

[0008] [8] A (meth)acrylic acid ester composition containing a (meth)acrylic acid ester obtained by the production method according to any one of [1] to [7]. [9] A mono(meth)acrylic acid ester obtained by the production method according to [5] or [6]; A di(meth)acrylic acid ester obtained by the production method according to [5] or [6]; A (meth)acrylic acid ester composition comprising:

[10] The (meth)acrylic acid ester composition according to [9], wherein the content of the mono(meth)acrylic acid ester is 0.1 to 20 mass % of the total amount of the (meth)acrylic acid ester composition.

[11] The (meth)acrylic acid ester composition according to any one of [8] to

[10] , wherein the Hazen color number APHA is 100 or less.

[12] A (meth)acrylic polymer obtained by polymerizing a (meth)acrylic acid ester obtained by the production method according to any one of [1] to [7].

[13] A (meth)acrylic polymer obtained by copolymerizing a (meth)acrylic acid ester obtained by the production method according to any one of [1] to [7] with another monomer copolymerizable with the (meth)acrylic acid ester. [Effects of the Invention]

[0009] According to the present invention, there is provided a production method that can obtain a (meth)acrylic acid ester with reduced coloration by a simple method. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, several embodiments of the present invention will be described in detail. The following embodiments are merely examples for the purpose of explanation, and the present invention is not limited to these embodiments. Furthermore, the present invention can be implemented in various forms without departing from the spirit of the present invention.

[0011] The following terms have the following meanings: "(Meth)acrylic acid" is a general term for "acrylic acid" and "methacrylic acid." "(Meth)acrylate" is a general term for "acrylate" and "methacrylate." The term "etheric oxygen atom" refers to an oxygen atom that forms an ether bond (-O-) between carbon atoms. "Monomer" means a compound having a polymerizable carbon-carbon double bond. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. For example, "1 to 20" means 1 or more and 20 or less. The lower and upper limits of the numerical ranges disclosed in this specification can be arbitrarily combined to form a new numerical range.

[0012] [Method of producing (meth)acrylic acid ester] The method for producing a (meth)acrylic acid ester of the present invention includes: obtaining a reaction liquid containing a (meth)acrylic acid ester by subjecting methyl (meth)acrylate and an alcohol to a transesterification reaction in the presence of a catalyst; and contacting the reaction liquid with an adsorbent containing aluminum oxide and silicon dioxide in the same particle.

[0013] In the method for producing a (meth)acrylic acid ester of the present invention, a reaction liquid containing a (meth)acrylic acid ester is brought into contact with an adsorbent containing aluminum oxide and silicon dioxide in the same particle, thereby producing a (meth)acrylic acid ester with reduced coloration, as will be shown in the examples described later.

[0014] By using an adsorption treatment using an adsorbent containing aluminum oxide and silicon dioxide in the same particle, discoloration can be reduced without prior washing with an aqueous sodium hydroxide solution as in Patent Document 2. Furthermore, there is no need to add water for the discoloration reduction treatment of Patent Document 3. Therefore, a (meth)acrylic acid ester with reduced discoloration can be obtained by a simple method. More detailed embodiments will be described below.

[0015] (alcohol) The alcohol used in the transesterification reaction may be any of a monoalcohol, a dialcohol, and a trialcohol. Any of the monoalcohol, the dialcohol, and the trialcohol may be an ether bond-containing alcohol having an etheric oxygen atom.

[0016] The number of carbon atoms in the alcohol is not particularly limited, but is preferably 2 to 20, more preferably 2 to 18, even more preferably 2 to 12, and even more preferably 2 to 8.

[0017] The monoalcohol is preferably a monoalcohol having 2 to 20 carbon atoms. Examples of the monoalcohol having 2 to 20 carbon atoms include ethanol, n-butanol, isobutanol, t-butanol, 2-ethylhexanol, lauryl alcohol, stearyl alcohol, isobornyl alcohol, allyl alcohol, phenol, benzyl alcohol, and phenoxyethanol.

[0018] The monoalcohol having 2 to 20 carbon atoms may be used alone or in combination of two or more. The monoalcohol having 2 to 20 carbon atoms preferably includes a linear or branched monoalcohol having 2 to 20 carbon atoms, and more preferably includes n-butanol or isobutanol.

[0019] The dialcohol is preferably a dialcohol having 2 to 8 carbon atoms. Furthermore, the trialcohol is preferably a trialcohol having 2 to 8 carbon atoms. Examples of dialcohols having 2 to 8 carbon atoms and trialcohols having 2 to 8 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, and trimethylolpropane. Of these, the dialcohols having 2 to 8 carbon atoms and trialcohols having 2 to 8 carbon atoms preferably include one or more selected from the group consisting of ethylene glycol, 1,2-propanediol, 1,3-propanediol, and trimethylolpropane. The dialcohols having 2 to 8 carbon atoms and trialcohols having 2 to 8 carbon atoms may be used alone or in combination of two or more kinds.

[0020] The number of etheric oxygen atoms in the ether bond-containing alcohol is preferably 1, but is not particularly limited thereto. The ether bond-containing alcohol may be used alone or in combination of two or more.

[0021] The ether bond-containing alcohol is preferably an ether bond-containing alcohol having 2 to 20 carbon atoms. Examples of ether bond-containing alcohols having 2 to 20 carbon atoms include diethylene glycol, triethylene glycol, PEG200, PEG300, 2-methoxyethanol, glycidyl alcohol, and tetrahydrofurfuryl alcohol. Of these, the ether bond-containing alcohol is preferably one selected from diethylene glycol, 2-methoxyethanol, glycidyl alcohol, and tetrahydrofurfuryl alcohol.

[0022] (catalyst) The catalyst is not particularly limited, but examples thereof include hydroxides, carbonates, and hydrogencarbonates of alkali metals such as lithium, sodium, and potassium; oxides, hydroxides, and carbonates of alkaline earth metals such as magnesium and calcium; alkali metal alkoxides such as lithium methoxide, sodium methoxide, sodium ethoxide, and potassium t-butoxide; alkali metal amides such as lithium amide, sodium amide, and potassium amide; titanium alkoxides such as tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate, tetrabutyl titanate, and tetra(2-ethylhexyl) titanate; and tin compounds such as dibutyltin oxide and dioctyltin oxide. The catalyst may be used alone or in combination of two or more.

[0023] Titanium catalysts are preferred because they produce fewer by-products of Michael addition reaction products during the transesterification reaction and have high catalytic activity, and titanium alkoxides, dibutyltin oxide, and dioctyltin oxide are more preferred.

[0024] One or more catalysts may be supplied to the reactor alone. Alternatively, the catalyst may be supplied to the reactor in a state where it is dissolved in the same alcohol as the raw material alcohol, or in a state where it is dissolved in the raw material (meth)acrylic acid ester. For example, a method in which the catalyst is directly dissolved in the entire amount of alcohol used in the reaction and supplied to the reactor, or a method in which the catalyst is dissolved in a portion of the alcohol used in the reaction and supplied to the reactor, may be mentioned. The amount of the catalyst used is preferably 0.001 mol % or more and 1 mol % or less, and more preferably 0.01 mol % or more and 0.1 mol % or less, relative to 1 mol of the alcohol.

[0025] (Transesterification reaction) In the transesterification reaction, methyl (meth)acrylate reacts with alcohol to produce (meth)acrylic acid ester, with methanol as a by-product. The ratio of the amounts of methyl (meth)acrylate and alcohol to be charged can be determined appropriately. From the viewpoint of increasing productivity, the ratio of methyl (meth)acrylate to 1 mol of alcohol is preferably 0.1 mol to 10 mol, more preferably 0.3 mol to 4 mol.

[0026] The reaction temperature of the transesterification reaction varies depending on the type of alcohol and whether or not a solvent is used, but is preferably 40 to 160°C, more preferably 50 to 140°C, and even more preferably 60 to 120°C. When the reaction temperature of the transesterification reaction is equal to or higher than the lower limit of the above-mentioned range, the reaction rate is better. When the reaction temperature of the transesterification reaction is equal to or lower than the upper limit of the above-mentioned range, decomposition, coloration, polymerization, etc. of the (meth)acrylic acid ester are easily suppressed.

[0027] The reaction pressure for the transesterification reaction is not particularly limited, and the reaction may be carried out under any of reduced pressure, normal pressure, and increased pressure.

[0028] Examples of reaction methods for the transesterification reaction include a batch method in which all raw materials are charged into a single reactor and the reaction is carried out to completion, a continuous method in which raw materials are continuously supplied into a reactor and the reaction is carried out continuously, and a circulation method in which a reactor and a blending tank are used and the raw materials are circulated between the reactor and the blending tank and the reaction is carried out in the reactor.

[0029] Since the transesterification reaction is an equilibrium reaction, productivity can be improved by separating the by-product methanol using a distillation column. For example, it is preferable to carry out the transesterification reaction while separating methanol from the system as an azeotropic mixture with methyl (meth)acrylate. Therefore, it is preferable that the reactor used for the transesterification reaction is a reactor equipped with a distillation column.

[0030] Examples of such reactors include a reactor vessel called a reaction kettle equipped with a distillation column on top, and a distillation column in which a still can be used as a reaction vessel. Examples of distillation columns include packed columns using packings such as Raschig rings, Lessing rings, Dixon packings, Pall rings, saddles, and Sulzer packings made of stainless steel, glass, or ceramic, and plate columns such as perforated plate columns and bubble cap columns.

[0031] The number of theoretical plates of the distillation column is preferably 5 or more, more preferably 7 or more, from the viewpoints of high separation capacity and stable operation.

[0032] The distillation column and the reactor may be connected in any of the following ways: the distillation column is connected to the top of the reactor, the distillation column is connected to the top of a separate vessel connected to the reactor, or the reactor is connected to any position between the top and bottom of the distillation column. In any of these connection ways, there may be one or more paths between the reactor and the distillation column, and a device such as a heat exchanger may be interposed between them.

[0033] When a monoalcohol which may have an etheric oxygen atom is used in the transesterification reaction with methyl (meth)acrylate, the transesterification reaction proceeds as shown in the following formula.

[0034] [ka]

[0035] In the formula, R 1a is a hydrogen atom or a methyl group. 2a is a hydrocarbon group having 2 to 20 carbon atoms which may have an etheric oxygen atom.

[0036] According to the transesterification reaction shown in the above chemical reaction formula, a (meth)acrylic acid ester (1) represented by the following formula (1) is obtained. CH2=CR 1a -C(=O)-OR 2a ...Equation (1)

[0037] R 2a The hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group. R 2a The hydrocarbon group R may be linear, branched, or may have a ring. 2a When the hydrocarbon group has a ring, the ring may be an aliphatic ring or an aromatic ring. R 2a The hydrocarbon group preferably has 2 to 20 carbon atoms, more preferably 2 to 18 carbon atoms, and even more preferably 2 to 12 carbon atoms.

[0038] R 2a Examples of the hydrocarbon group include an alkyl group having 2 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, a cycloalkenyl group having 3 to 20 carbon atoms, an alkynyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and an aromatic alkyl group having 7 to 20 carbon atoms. An "aromatic alkyl group" refers to a group in which one or more hydrogen atoms of an alkyl group are substituted with an aryl group.

[0039] R 2a Examples of the alkyl group include an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, a lauryl group, and a stearyl group. R 2a Examples of the cycloalkyl group include a cyclopropyl group, a cyclohexyl group, and an isobornyl group. R 2a Examples of the alkenyl group include a vinyl group and an allyl group. R 2a Examples of the cycloalkenyl group include a cyclopentenyl group, a cyclopentadienyl group, and a cyclohexenyl group. R 2a The alkynyl group includes, for example, a propynyl group. R 2a Examples of the aryl group include a phenyl group and a naphthyl group. R 2aExamples of the aromatic alkyl group include a benzyl group and a phenoxyethyl group.

[0040] Because of its relatively easy physical properties, R 2a As the alkyl group, an alkyl group having 2 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and an aromatic alkyl group having 7 to 20 carbon atoms are preferred, and an ethyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, a lauryl group, a stearyl group, a cyclohexyl group, an isobornyl group, an allyl group, a phenyl group, and a benzyl group are more preferred.

[0041] R 2a When R has an etheric oxygen atom, 2a The number of carbon atoms in R is preferably 2 to 20, more preferably 2 to 8. The number of etheric oxygen atoms is preferably 1, but is not limited thereto and may be 2 or more. 2a Even when R has an etheric oxygen atom, 2a The hydrocarbon group R may be linear, branched, or may have a ring. 2a When the hydrocarbon group has a ring, the ring may or may not have an etheric oxygen atom.

[0042] R 2a When R has an etheric oxygen atom, 2a Examples of the alkyl group include a 2-methoxyethyl group, a 2-(2-methoxyethoxy)ethyl group, a 2-[2-(2-methoxyethoxy)ethoxy]ethyl group, a glycidyl group, and a tetrahydrofurfuryl group. In view of their physical properties, 2-methoxyethyl, glycidyl and tetrahydrofurfuryl groups are preferred because they are relatively easy to handle.

[0043] Examples of the (meth)acrylic acid ester (1) include ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, allyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, glycidyl (meth)acrylate, 2-(2-methoxyethoxy)ethyl (meth)acrylate, 2-[2-(2-methoxyethoxy)ethoxy]ethyl (meth)acrylate, and tetrahydrofurfuryl (meth)acrylate.

[0044] As the (meth)acrylic acid ester (1), R 2a is a linear or branched alkyl group having 2 to 20 carbon atoms; R is an alkyl (meth)acrylate; 2a cycloalkyl(meth)acrylate, R is a cycloalkyl group having 3 to 20 carbon atoms; 2a is an alkenyl group having 2 to 20 carbon atoms, R 2a is an aryl group having 6 to 20 carbon atoms, R 2a is an aromatic alkyl group having 7 to 20 carbon atoms, and ethyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, allyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, glycidyl (meth)acrylate, and tetrahydrofurfuryl (meth)acrylate are more preferred.

[0045] When a diol which may have an etheric oxygen atom is transesterified with methyl (meth)acrylate, at least one (meth)acrylic acid ester selected from the group consisting of a mono(meth)acrylic acid ester and a di(meth)acrylic acid ester is produced. For example, the transesterification reaction proceeds as shown in the following formula:

[0046] [ka]

[0047] In the formula, R 1b , R 3b and R 5b are each independently a hydrogen atom or a methyl group. R 2b is a linear or branched alkylene group having 2 to 8 carbon atoms which may have an etheric oxygen atom. R 41b is a linear or branched alkylene group having 2 to 8 carbon atoms which may have an etheric oxygen atom.

[0048] According to the transesterification reaction shown in the above chemical reaction formula, a (meth)acrylic acid ester (2) represented by the following formula (2) and a (meth)acrylic acid ester (3) represented by the following formula (3) are obtained. CH2=CR 1b -C(=O)-OR 2b -OH...Formula (2) CH2=CR 3b -C(=O)-OR 41b -OC(=O)-CR 5b =CH2...Equation (3)

[0049] When a trialcohol which may have an etheric oxygen atom is transesterified with methyl(meth)acrylate, at least one (meth)acrylic acid ester selected from the group consisting of a mono(meth)acrylic acid ester, a di(meth)acrylic acid ester, and a tri(meth)acrylic acid ester is produced. For example, the transesterification reaction proceeds as shown in the following formula:

[0050] [ka]

[0051] In the formula, R 3b , R 5b , R 6b , R 8b and R 9b are each independently a hydrogen atom or a methyl group. 7b R is a linear or branched trivalent hydrocarbon group having 2 to 8 carbon atoms which may have an etheric oxygen atom. 42b is a linear or branched alkylene group having 2 to 8 carbon atoms which may have an etheric oxygen atom.

[0052] According to the transesterification reaction shown in the above chemical reaction formula, a (meth)acrylic acid ester (4) represented by the following formula (4) is obtained.

[0053] [ka]

[0054] In the (meth)acrylic acid ester (2) and the (meth)acrylic acid ester (3), R 2b and R 41b The number of carbon atoms is preferably 2 to 8, and more preferably 2 to 6. R 2b and R 41b Examples of R include an ethylene group, a propylene group, an isopropylene group, and a butylene group. 2b and R 41bExamples of the hydroxy group include a hydroxyethylene group, a hydroxypropylene group, and a hydroxybutylene group.

[0055] R 7b The trivalent hydrocarbon group has 2 to 8 carbon atoms, preferably 2 to 4 carbon atoms. R 7b An example of the trivalent hydrocarbon group is —(CH 2 )—C(—CH 2 —)(—CH 3 )—CH 2 —.

[0056] Examples of the (meth)acrylic acid ester (2) include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, diethylene glycol monomethacrylate, triethylene glycol mono(meth)acrylate, and 1,4-butanediol monomethacrylate. Examples of the (meth)acrylic acid ester (3) include ethylene glycol di(meth)acrylate, 1,3-propanediol di(meth)acrylate, 1,2-propanediol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, diethylene glycol dimethacrylate, triethylene glycol di(meth)acrylate, and 1,4-butanediol dimethacrylate. An example of the (meth)acrylic acid ester (4) is trimethylolpropane tri(meth)acrylate.

[0057] The (meth)acrylic acid ester (2), the (meth)acrylic acid ester (3), and the (meth)acrylic acid ester (4) preferably include one or more selected from the group consisting of ethylene glycol di(meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and trimethylolpropane tri(meth)acrylate.

[0058] (polymerization inhibitor) The transesterification reaction may be carried out in the presence of a polymerization inhibitor. Examples of the polymerization inhibitor include phenolic compounds, quinone compounds, nitrobenzene compounds, N-oxyl compounds, amine compounds, phosphorus-containing compounds, sulfur-containing compounds, iron-containing compounds, copper-containing compounds, and manganese-containing compounds. The polymerization inhibitor may be used alone or in combination of two or more kinds.

[0059] Examples of phenolic compounds include alkylphenols, hydroxyphenols, aminophenols, nitrophenols, nitrosophenols, alkoxyphenols, and tocopherols.

[0060] Examples of alkylphenols include o-cresol, m-cresol, p-cresol, 2-t-butyl-4-methylphenol, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 2-t-butylphenol, 4-t-butylphenol, 2,4-di-t-butylphenol, 2-methyl-4-t-butylphenol, 4-t-butyl-2,6-dimethylphenol, 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), and 3,5-di-t-butyl-4-hydroxytoluene.

[0061] Examples of hydroxyphenols include hydroquinone, 2-methylhydroquinone, 2-t-butylhydroquinone, 2,5-di-t-butylhydroquinone, 2,6-di-t-butylhydroquinone, 2,5-di-t-amylhydroquinone, 2-t-butylmethoxyhydroquinone, 2,3,5-trimethylhydroquinone, 2,5-dichlorohydroquinone, 1,2-dihydroxybenzene, 2-acetylhydroquinone, 4-methylcatechol, 4-t-butylcatechol, 2-methylresorcinol, 4-methylresorcinol, and 2,3-dihydroxyacetophenone.

[0062] Examples of aminophenols include o-aminophenol, m-aminophenol, p-aminophenol, 2-(N,N-dimethylamino)phenol, and 4-(ethylamino)phenol.

[0063] Examples of nitrophenols include o-nitrophenol, m-nitrophenol, p-nitrophenol, and 2,4-dinitrophenol.

[0064] Examples of nitrosophenols include o-nitrosophenol, m-nitrosophenol, p-nitrosophenol, and α-nitroso-β-naphthol.

[0065] Examples of alkoxyphenols include 2-methoxyphenol, 2-ethoxyphenol, 2-isopropoxyphenol, 2-t-butoxyphenol, 4-methoxyphenol, 4-ethoxyphenol, 4-propoxyphenol, 4-butoxyphenol, 4-t-butoxyphenol, 4-heptoxyphenol, hydroquinone monobenzyl ether, t-butyl-4-methoxyphenol, di-t-butyl-4-methoxyphenol, pyrogallol-1,2-dimethyl ether, and hydroquinone monobenzoate.

[0066] Examples of tocopherols include α-tocopherol and 2,3-dihydro-2,2-dimethyl-7-hydroxybenzofuran.

[0067] Examples of quinone compounds include p-benzoquinone, chloro-p-benzoquinone, 2,5-dichloro-p-benzoquinone, 2,6-dichloro-p-benzoquinone, tetrachloro-p-benzoquinone, tetrabromo-p-benzoquinone, 2,3-dimethyl-p-benzoquinone, 2,5-dimethyl-p-benzoquinone, methoxy-p-benzoquinone, and methyl-p-benzoquinone.

[0068] Examples of nitrobenzene compounds include nitrobenzene, o-dinitrobenzene, m-dinitrobenzene, p-dinitrobenzene, 2,4-dinitrobenzene, dinitrodurene, and 2,2-diphenyl-1-picrylhydrazine.

[0069] Examples of the N-oxyl compounds include 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-acetoxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 2,2,6,6-tetramethyl-piperidine-N-oxyl, piperidine-1-oxyl, 4-(dimethylamino)-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-amino-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-ethenoloxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, and 4-benzoyloxy-2,2,6,6-tetramethyl-piperidine-N-oxol. Sil, 2,2,5,5-tetramethyl-piperidine-N-oxyl, 3-amino-2,2,5,5-tetramethyl-piperidine-N-oxyl, 4,4',4"-tris(2,2,6,6-tetramethyl-piperidine-N-oxyl)phosphite, 3-oxo-2,2,5,5-tetramethylpyrrolidine-N-oxyl, pyrrolidine-1-oxyl, 2,2,5,5-tetramethyl-1-oxa-3-azacyclopentyl-3-oxy, 2,2,5,5-tetramethyl-3-pyrrolinyl-1-oxy-3-carboxylic acid, 2,2,3,3,5,5,6,6-octamethyl-1,4-diazacyclohexyl-1,4-dioxy, di-t-butyl nitroxide, and di-t-amyl nitroxide.

[0070] Examples of the amine compounds include N,N-diphenylamine, alkylated diphenylamine, 4,4'-dicumyl-diphenylamine, 4,4'-dioctyldiphenylamine, 4-aminodiphenylamine, p-nitrosodiphenylamine, N-nitrosodinaphthylamine, N-nitrosodiphenylamine, N-nitrosophenylnaphthylamine, N-nitrosophenylhydroxylamine, N,N'-dialkyl-p-phenylenediamine (the two alkyl groups may be the same or different, each independently have 1 to 4 carbon atoms, and may be linear or branched), N,N'-diphenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl- Examples include 1,4-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N,N-diethylhydroxylamine, 1,4-benzenediamine, N-(1,4-dimethylpentyl)-N'-phenyl-1,4-benzenediamine, 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, 2,2,4-trimethyl-1,2-dihydroquinoline polymer, aldol-α-naphthylamine, N-phenyl-β-naphthylamine, 4-hydroxy-2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 1,4-dihydroxy-2,2,6,6-tetramethylpiperidine, and 1-hydroxy-4-benzoyloxy-2,2,6,6-tetramethylpiperidine.

[0071] Examples of phosphorus-containing compounds include triphenylphosphine, triphenyl phosphite, triethyl phosphite, tris(isodecyl)phosphite, tris(tridecyl)phosphite, phenyl diisooctyl phosphite, phenyl diisodecyl phosphite, phenyl di(tridecyl)phosphite, diphenyl isooctyl phosphite, diphenyl isodecyl phosphite, diphenyl tridecyl phosphite, phosphonic acid [1,1-diphenyl-4,4'-diylbistetrakis-2,4-bis(1,1-dimethylethyl)phenyl] ester, triphenyl phosphite, tris(nonylphenyl)phosphite, 4,4'-isopropylidenediphenol alkyl phosphite, tris(2,4-di-t-butylphenyl)phosphite, tris(biphenyl)phosphite, and diphenyl phosphite. Examples of suitable phosphate phosphates include tearyl pentaerythritol diphosphite, di(2,4-di-t-butylphenyl)pentaerythritol diphosphite, di(nonylphenyl)pentaerythritol diphosphite, phenyl bisphenol A pentaerythritol diphosphite, tetra(tridecyl)-4,4'-butylidenebis(3-methyl-6-t-butylphenol) diphosphite, hexa(tridecyl)-1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane triphosphite, 3,5-di-t-butyl-4-hydroxybenzyl phosphate diethyl ester, sodium bis(4-t-butylphenyl) phosphate, sodium 2,2'-methylene-bis(4,6-di-t-butylphenyl) phosphate, and 1,3-bis(diphenoxyphosphonyloxy)benzene.

[0072] Examples of sulfur-containing compounds include diphenyl sulfide, phenothiazine, 3-oxophenothiazine, 5-oxophenothiazine, phenothiazine dimer, 1,4-dimercaptobenzene, 1,2-dimercaptobenzene, 2-mercaptophenol, 4-mercaptophenol, 2-(methylthio)phenol, 3,7-bis(dimethylamino)phenothiazinium chloride, and sulfur (element).

[0073] An example of an iron-containing compound is iron(III) chloride.

[0074] Examples of copper-containing compounds include copper dimethyldithiocarbamate, copper diethylthiocarbamate, copper dibutylthiocarbamate, copper salicylate, copper acetate, copper thiocyanate, copper nitrate, copper chloride, copper carbonate, copper hydroxide, copper acrylate, and copper methacrylate.

[0075] Examples of manganese-containing compounds include manganese dialkyldithiocarbamate (the two alkyl groups are methyl, ethyl, propyl, or butyl groups and may be the same or different), manganese diphenyldithiocarbamate, manganese formate, manganese acetate, manganese octanoate, manganese naphthenate, manganese permanganate, and manganese salts of ethylenediaminetetraacetic acid.

[0076] From the viewpoint of storage stability, the polymerization inhibitor is preferably at least one selected from the group consisting of phenolic compounds, N-oxyl compounds, amine compounds, phosphorus-containing compounds, and sulfur-containing compounds, more preferably at least one selected from the group consisting of hydroquinone, 4-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, N,N-diphenylamine, N-nitrosodiphenylamine, triphenyl phosphite, and phenothiazine, and even more preferably at least one selected from the group consisting of hydroquinone, 4-methoxyphenol, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, N,N-diphenylamine, N-nitrosodiphenylamine, and phenothiazine.

[0077] (solvent) The transesterification reaction is preferably carried out without a solvent from the viewpoints of productivity and the burden of solvent recovery, but a solvent inert to the reaction may be used as necessary. When a solvent is used, it is preferable to use a solvent that forms an azeotropic composition with the by-produced methanol.

[0078] Examples of the solvent include n-pentane, n-hexane, n-heptane, n-octane, 2,3-dimethylbutane, 2,5-dimethylhexane, 2,2,4-trimethylpentane, cyclohexane, benzene, and toluene. Of these, n-hexane, n-heptane, and cyclohexane are preferred. The solvent may be used alone or in combination of two or more kinds.

[0079] (adsorption treatment) In purifying the reaction liquid, the reaction liquid containing the (meth)acrylic acid ester is brought into contact with an adsorbent containing aluminum oxide and silicon dioxide in the same particle. The adsorbent containing aluminum oxide and silicon dioxide in the same particle is not particularly limited, but an example thereof is silica alumina.

[0080] Examples of adsorbents containing aluminum oxide and silicon dioxide in the same particle include activated clay, silica alumina, and zeolite. Among these, silica alumina is preferably used as the adsorbent because it can effectively remove coloring.

[0081] Silica-alumina contains silicon dioxide (SiO2) and aluminum oxide (Al2O3). Silica-alumina prepared by any synthesis method can be used.

[0082] The aluminum content of silica-alumina is preferably 1 to 50 mass%, more preferably 3 to 40 mass%, and even more preferably 5 to 30 mass%. The aluminum content of silica-alumina can be calculated by mass spectrometry as the proportion of aluminum to the total amount of all constituent elements of silica-alumina.

[0083] The silicon content of silica-alumina is preferably 5 to 70 mass%, more preferably 10 to 60 mass%, and even more preferably 15 to 50 mass%. The silicon content of silica-alumina can be calculated by mass spectrometry as the silicon content ratio to the total amount of all constituent elements of silica-alumina.

[0084] Commercially available silica-alumina may be used, but is not limited to, for example, LA, HA, HA60A series, N630L series, N630HN series (products of JGC Catalysts and Chemicals), Neobead SA, Galleon Neutral D2-Y (products of Mizusawa Industrial Chemicals), Mullite (product of Saint-Gobain), and Silica-Alumina Catalyst Carrier Grade 135 (product of Sigma-Aldrich).

[0085] When a titanium catalyst is used, the amount of adsorbent containing aluminum oxide and silicon dioxide in the same particle is preferably 0.35 to 5.00 kg per mol of titanium catalyst contained in the reaction solution when contacted with the adsorbent, more preferably 0.45 to 4.00 kg per mol of titanium catalyst, and even more preferably 0.55 to 3.00 kg per mol of titanium catalyst. When the amount of adsorbent used is equal to or greater than the lower limit of the above-mentioned range, coloration of the (meth)acrylic acid ester is more easily suppressed. When the amount of adsorbent used is equal to or less than the upper limit of the above-mentioned range, removal by purification is easy.

[0086] The timing of starting the adsorption treatment is not particularly limited and may be appropriately changed depending on the composition ratio of the mono(meth)acrylic acid ester and the di(meth)acrylic acid ester, and can be set in consideration of the desired composition ratio.

[0087] In some examples, the more the proportion of the mono(meth)acrylic acid ester in the reaction solution is reduced to a certain extent, the more easily the coloration-reducing effect of the adsorption treatment is exerted. For example, when a diol which may have an etheric oxygen atom is used as the alcohol in the transesterification reaction, it is useful to contact the reaction solution with an adsorbent when the proportion of the mono(meth)acrylic acid ester becomes 20 mass% or less of the total amount of the diol which may have an etheric oxygen atom, the mono(meth)acrylic acid ester, and the di(meth)acrylic acid ester.

[0088] The temperature of the reaction liquid when contacting the reaction liquid with the adsorbent is not particularly limited, but is preferably 40 to 100°C, more preferably 45 to 90°C, and even more preferably 50 to 80°C. If the temperature of the reaction liquid when contacting the reaction liquid with the adsorbent is equal to or higher than the lower limit of the above-mentioned range, the adsorption efficiency is improved, and coloration is easily suppressed. If the temperature of the reaction liquid when contacting the reaction liquid with the adsorbent is equal to or lower than the upper limit of the above-mentioned range, decomposition and polymerization of the (meth)acrylic acid ester are easily suppressed.

[0089] After the transesterification reaction is completed, the catalyst is dissolved or precipitated as needed, and then removed by methods such as separation or filtration. The excess (meth)acrylic acid ester may be recovered either before or after catalyst removal. The recovery can be carried out by heating under normal or reduced pressure to evaporate or condense. It is then preferable to dissolve the reaction solution in an organic solvent and wash it. Examples of such organic solvents include hydrocarbons, ethers, and ester-based solvents.

[0090] Before or after the adsorption treatment, filtration may be performed to remove insoluble impurities such as insolubilized catalyst, adsorbent, and dust. Filtration may be performed under pressure or reduced pressure. Furthermore, diatomaceous earth or the like may be used as a filter aid to prevent filtration load. A polymerization inhibitor may also be used in the adsorption treatment. The type and method of use of the polymerization inhibitor are the same as those described for the transesterification reaction.

[0091] Alternatively, after the transesterification reaction, the reaction mixture may be purified to separate unreacted raw materials and by-products. Purification can be performed by various methods, such as distillation, crystallization, extraction, and column chromatography.

[0092] [(Meth)acrylic acid ester composition] The (meth)acrylic acid ester composition contains a (meth)acrylic acid ester obtained by the above-described method for producing a (meth)acrylic acid ester of the present invention. The reaction solution obtained by the method for producing a (meth)acrylic acid ester of the present invention may be used as the (meth)acrylic acid ester composition as it is, or an optional component may be blended with the reaction solution and used as the (meth)acrylic acid ester composition.

[0093] In one example, the (meth)acrylic acid ester composition contains at least one selected from the group consisting of the (meth)acrylic acid ester (1), the (meth)acrylic acid ester (2), the (meth)acrylic acid ester (3), and the (meth)acrylic acid ester (4).

[0094] For example, when a diol which may have an etheric oxygen atom is used as the alcohol in the transesterification reaction, a (meth)acrylic acid ester composition containing a mono(meth)acrylic acid ester and a di(meth)acrylic acid ester is obtained. In this case, the content of the mono(meth)acrylic acid ester is preferably 0.1 to 20 mass%, more preferably 0.1 to 15 mass%, and even more preferably 0.1 to 10 mass% of the total amount of the (meth)acrylic acid ester composition.

[0095] The APHA of the (meth)acrylic acid ester composition is preferably 100 or less, more preferably 80 or less, even more preferably 70 or less, and particularly preferably 50 or less. APHA is a value of the Hazen color number, and is measured by colorimetry or absorptiometry.

[0096] (other monomers) The (meth)acrylic acid ester composition may further contain, as an optional component, another monomer copolymerizable with the (meth)acrylic acid ester.

[0097] Examples of other monomers include methyl (meth)acrylate, unsaturated carboxylic acid, unsaturated carboxylic acid anhydride, maleimide, hydroxy group-containing vinyl monomer, vinyl ester, nitrogen-containing vinyl monomer, epoxy group-containing monomer, aromatic vinyl monomer, alkanediol di(meth)acrylate, polyoxyalkylene glycol di(meth)acrylate, and vinyl monomer having two or more ethylenically unsaturated bonds in the molecule. The other monomers may be used alone or in combination of two or more.

[0098] Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, and itaconic acid. Examples of unsaturated carboxylic acid anhydrides include maleic anhydride and itaconic anhydride. Examples of maleimides include N-phenylmaleimide and N-cyclohexylmaleimide.

[0099] Examples of the hydroxy group-containing vinyl monomer include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate. Examples of vinyl esters include vinyl acetate and vinyl benzoate. Examples of the nitrogen-containing vinyl monomer include methacrylamide and acrylonitrile. Examples of epoxy group-containing monomers include glycidyl acrylate and glycidyl methacrylate.

[0100] Examples of aromatic vinyl monomers include styrene and α-methylstyrene. Examples of alkanediol di(meth)acrylates include ethylene glycol di(meth)acrylate, 1,2-propylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate.

[0101] Examples of polyoxyalkylene glycol di(meth)acrylates include diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, triethylene glycol (meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and neopentyl glycol di(meth)acrylate. An example of a vinyl monomer having two or more ethylenically unsaturated bonds in the molecule is divinylbenzene.

[0102] Other monomers that may be used include vinyl chloride, vinylidene chloride and derivatives thereof, unsaturated polyester prepolymers obtained from at least one polycarboxylic acid including an ethylenically unsaturated polycarboxylic acid and at least one diol, and vinyl ester prepolymers obtained by acrylic-modifying the terminals of epoxy groups.

[0103] (Polymerization initiator) The (meth)acrylic acid ester composition may further contain a polymerization initiator. Examples of the polymerization initiator include azo compounds, organic peroxides, persulfate compounds, and redox-based polymerization initiators. The polymerization initiator may be used alone or in combination of two or more kinds.

[0104] Examples of azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2-methylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(2-methylpropane), 1,1-azobis(cyclohexanecarbonitrile), and dimethyl-2,2'-azobisisobutyrate.

[0105] Examples of organic peroxides include benzoyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxybenzoate, t-hexylperoxybenzoate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxyacetate, and t-hexylperoxyisopropyl monocarbonate. peroxyisopropyl peroxide, t-hexylperoxy-2-ethylhexanoate, t-amylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxyethylhexanoate, 1,1,2-trimethylpropylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxyisopropyl monocarbonate, 1,1,2-trimethylpropylperoxyisopropyl monocarbonate, 1,1,3,3-tetramethylbutylperoxyisononatoate, 1,1,2-trimethylpropylperoxyisononatoate, di-t-butyl peroxide, di-t-hexyl peroxide, lauroyl peroxide, and dilauroyl peroxide.

[0106] An example of the persulfate compound is potassium persulfate.

[0107] The content of the polymerization initiator is not particularly limited and may be, for example, 0.005 to 5 parts by mass relative to 100 parts by mass of the total mass of the monomers in the (meth)acrylic acid ester composition.

[0108] (additives) The (meth)acrylic acid ester composition may further contain additives such as a chain transfer agent, a release agent, a lubricant, a plasticizer, an antioxidant, an antistatic agent, a light stabilizer, an ultraviolet absorber, a flame retardant, a flame retardant aid, a polymerization inhibitor, a filler, a pigment, a dye, a silane coupling agent, a leveling agent, an antifoaming agent, and a fluorescent agent, as necessary. The additives may be used alone or in combination of two or more.

[0109] [(Meth)acrylic polymer] A (meth)acrylic polymer can be produced by polymerizing the (meth)acrylic ester composition. The (meth)acrylic polymer may be a homopolymer of the above-mentioned (meth)acrylic ester, a copolymer of two or more of the above-mentioned (meth)acrylic ester, or a copolymer having units based on the above-mentioned other monomer.

[0110] The polymerization method is not particularly limited. Examples include bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization. Among these, bulk polymerization is preferred from the viewpoints of the environmental load caused by the use of solvents and the transparency of the resulting (meth)acrylic polymer.

[0111] The bulk polymerization method is not particularly limited, and examples thereof include various cast polymerization methods such as cell casting and continuous casting.

[0112] The cast polymerization method is a method in which a (meth)acrylic polymer is obtained by injecting a (meth)acrylic acid ester composition into a mold consisting of two inorganic glass plates or metal plates (e.g., SUS plates) arranged opposite each other at a predetermined distance and having their peripheries sealed with a gasket such as a soft resin tube, and polymerizing the composition.

[0113] The mold for cast polymerization is not particularly limited, and various molds can be used. Examples of molds for cell casting include those in which two plates such as inorganic glass plates, chrome-plated metal plates, and stainless steel plates are arranged opposite each other at a predetermined distance, and a gasket is placed on the edges of the plates to form a sealed space between the plates and the gasket.

[0114] An example of a mold for continuous casting is one in which a sealed space is formed by the opposing surfaces of a pair of endless belts running in the same direction at the same speed and gaskets running at the same speed as the endless belts on both side edges of the endless belts.

[0115] The gap between the molds is adjusted as appropriate so as to obtain a resin plate of the desired thickness, but is generally 1 to 30 mm.

[0116] The polymerization temperature is preferably 125 to 210°C, more preferably 130 to 180°C. The polymerization time is preferably 0.5 to 24 hours.

[0117] The weight average molecular weight (Mw) of the (meth)acrylic polymer is not particularly limited and can be, for example, 100,000 to 1,000,000. The larger the Mw of the (meth)acrylic polymer, the more improved the solvent resistance and chemical resistance can be. The Mw of the (meth)acrylic polymer can be controlled by adjusting the polymerization temperature, polymerization time, amount of polymerization initiator added, and the like.

[0118] Applications of the (meth)acrylic polymer are not particularly limited, and examples thereof include paints, adhesives, resin modifiers, artificial marble, paper latex, optical materials, signs, lighting covers, windows for machinery and equipment, aquarium tanks, and components for various display devices. [Example]

[0119] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following description.

[0120] [Abbreviation] MMA: methyl methacrylate 2EDOH: Diethylene glycol 2EDmMA: Diethylene glycol monomethacrylate 2EDdiMA: Diethylene glycol dimethacrylate 1,4-BDOH: 1,4-butanediol 1,4-BDmMA: 1,4-butanediol monomethacrylate 1,4-BDdiMA: 1,4-butanediol dimethacrylate 3EDOH: Triethylene glycol 3EDmMA: Triethylene glycol monomethacrylate 3EDdiMA: Triethylene glycol dimethacrylate PHEOH: Phenoxyethanol PHEMA: Phenoxyethyl methacrylate MEHQ: 4-Methoxyphenol (hydroquinone monomethyl ether) Silica-alumina powder 1: Mizusawa Industrial Chemicals Co., Ltd. product "Galleon Neutral D2-Y" (aluminum content 28%, silicon content 22%) Silica-alumina powder 2: Sigma-Aldrich "grade 135" (aluminum content 6%) Activated carbon: Kanto Chemical Co., Ltd. product "Activated carbon (powder)" Activated alumina: Mizusawa Industrial Chemicals Co., Ltd. product "Neo Bead MSC#100"

[0121] [APHA] APHA color index standard solutions of 20, 30, 50, 70, 100, and 200 were prepared using an APHA color index standard solution (No. 500, Kishida Chemical Co., Ltd.). Each of these standard solutions was placed in a 1 cm quartz cell. The absorbance at 417 nm of each quartz cell was measured using an ultraviolet-visible spectrophotometer (product name: UV-1800, Shimadzu Corporation). From these absorbance values, the APHA value of each standard solution and a calibration curve of absorbance were created. The absorbance at 417 nm of the measurement sample was measured using the same method as for the standard solutions. The APHA of the measurement sample was calculated from this absorbance value and the calibration curve.

[0122] [GC measurement] The GC measurement was performed using a Shimadzu GC-2014.

[0123] The GC conditions are as follows: Column (product name: DB-WAX, manufactured by Agilent Technologies, length: 30 m, inner diameter: 0.32 mm, film thickness: 0.25 μm) Injection volume: 1.0μL Vaporization chamber temperature: 230℃ Column oven temperature: held at 50°C for 5 minutes, heated from 50°C to 230°C at 10°C / min, and held at 230°C for 5 minutes. Carrier gas: Helium Injection mode: Split (split ratio 50) Control mode: Constant linear velocity (35.0 cm / sec) Detector: FID Detector temperature: 250℃ Detector hydrogen flow rate: 40 mL Detector air flow rate: 410 mL Make-up gas: Helium Make-up gas flow rate: 30mL

[0124] [Example 1] [ka]

[0125] The transesterification reaction shown in the above formula was carried out, and the details are as follows. A 2 L five-neck flask equipped with a rectification column (internal diameter 35 mm, 10 theoretical plates), a stirring blade, a thermometer, and an air inlet tube was prepared. 218 g of 2EDOH (Mitsubishi Chemical Corporation product), 1230 g of MMA, and 0.1 g of MEHQ were placed in the flask. The flask was heated in an oil bath while air was bubbled and stirred. MMA and water were extracted azeotropically at an internal temperature of 100-110 °C. The water content of the flask's internal solution was analyzed using a Karl Fischer moisture analyzer (product name: CA-21, Mitsubishi Chemical Analytical Co., Ltd.). After confirming that the water content was 32 ppm, 2.8 g of tetra-n-butyl titanate was added. The pressure was then gradually reduced from 700 to 550 Torr, ensuring that the internal temperature did not exceed 100 °C. The transesterification reaction was carried out while extracting MMA and methanol azeotropically.

[0126] Next, 0.202 g of silica alumina powder 1 was added to 50.0 g of a sample taken from the resulting reaction solution, and the mixture was stirred for 1 hour while heating at 60°C. The mixture was then filtered using a separatory funnel and filter paper (Kiriyama funnel filter paper No. 4, 60 mm diameter) and concentrated using an evaporator. The concentrated solution was filtered through a 0.45 μm PTFE filter, and the APHA content of the sample was measured. The composition of the reaction solution was also analyzed by GC. The results are shown in Table 1.

[0127] [Comparative Example 1] In Comparative Example 1, activated carbon was used as the adsorbent instead of silica alumina powder 1. In addition, an acrylic ester composition was produced in the same manner as in Example 1, except that the sample amount of the collected reaction liquid, the amount of the adsorbent, and the stirring temperature of the adsorbent were changed as shown in Table 1. The results are shown in Table 1.

[0128] [Example 2] [ka]

[0129] The chemical reaction shown in the above formula was carried out, with the details as follows: A 2 L five-neck flask equipped with a rectification column (internal diameter 35 mm, 10 theoretical plates), a stirring blade, a thermometer, and an air inlet tube was prepared. 180 g of 1,4-BDOH (Mitsubishi Chemical Corporation product), 1200 g of MMA, and 0.7 g of MEHQ were placed in the flask. The flask was heated in an oil bath while air was bubbled and stirred. MMA and water were extracted azeotropically at an internal temperature of 100-110 °C. The water content of the liquid in the flask was analyzed using a Karl Fischer moisture analyzer (product name: CA-21, Mitsubishi Chemical Analytical Co., Ltd.). After confirming that the water content was 84 ppm, 2.7 g of tetra-n-butyl titanate was added. The pressure was gradually reduced from 700 to 630 Torr so that the internal temperature did not exceed 110 °C. The transesterification reaction was carried out while extracting MMA and methanol azeotropically.

[0130] Next, 0.624 g of silica alumina powder 2 was added to 20.0 g of the reaction solution obtained, and the mixture was stirred for 1.5 hours while heating at 60°C. The mixture was then filtered using a separatory funnel and filter paper (Kiriyama funnel filter paper No. 4, 60 mm diameter) and concentrated using an evaporator. The concentrated solution was filtered through a 0.45 μm PTFE filter, and the APHA content of the sample was measured. The composition of the reaction solution was also analyzed by GC. The results are shown in Table 2.

[0131] [Example 3, Example 4, Comparative Example 2] An acrylic ester composition was produced in the same manner as in Example 2, except that the sample amount of the collected reaction solution, the type of adsorbent, the amount of adsorbent used, and the stirring temperature of the adsorbent were changed as shown in Table 2. The results are shown in Table 2.

[0132] [Table 1]

[0133] [Table 2]

[0134] In the table, "adsorbent / Ti" is the amount of adsorbent used (kg / mol) per 1 mol of titanium catalyst used in the transesterification reaction (the same applies hereinafter).

[0135] In Examples 1 to 4, APHAs could be reduced by using silica-alumina as an adsorbent containing aluminum oxide and silicon dioxide in the same particle. As shown in the results of Examples 1 to 3, in particular, when the amount of silica-alumina used was 0.35 kg or more per 1 mol of the titanium catalyst used in the transesterification reaction, APHAs could be sufficiently reduced. In contrast, in Comparative Examples 1 and 2, APHA could not be reduced sufficiently.

[0136] [Example 5] The transesterification reaction was carried out under the same conditions as in Example 1. The reaction liquid was sampled 5.5 hours and 6.0 hours after the start of the transesterification reaction. Each reaction liquid was then subjected to an adsorption treatment using silica alumina powder 1. The sample amount of the sampled reaction liquid, the type and amount of adsorbent used, the adsorbent stirring temperature, and the stirring time are shown in Table 3. The mixture was then filtered using a separatory funnel and filter paper (Kiriyama funnel filter paper No. 4, 60 mm diameter) and concentrated using an evaporator. The concentrated solution was filtered through a 0.45 μm PTFE filter, and the APHA content of the sample was measured. The composition of the reaction solution was also analyzed by GC. The results are shown in Table 3.

[0137] [Table 3]

[0138] As can be seen from Table 3, the APHA value was also sufficiently low in Example 5. In particular, the APHA value was lower in the sample collected 6.0 hours after the start of the transesterification reaction than in the sample collected 5.5 hours after the start of the transesterification reaction. From these results, it was considered preferable to bring the adsorbent into contact with the reaction solution when the proportion of 2EDmMA became 20% by mass or less of the total amount of 2EDOH, 2EDmMA, and 2EDdiMA.

[0139] [Example 6] [ka]

[0140] The chemical reaction shown in the above formula was carried out, with the details as follows: A 2 L five-neck flask equipped with a rectification column (internal diameter 35 mm, theoretical plate count 10), a stirring blade, a thermometer, and an air inlet tube was prepared. 60 g of 3EDOH (Mitsubishi Chemical Corporation product), 240 g of MMA, and 0.02 g of MEHQ were placed in the flask. The flask was heated in an oil bath while air was bubbled and stirred. MMA and water were extracted azeotropically at an internal temperature of 100-110°C. The water content of the flask's internal liquid was analyzed using a Karl Fischer moisture analyzer (product name: CA-21, Mitsubishi Chemical Analytical Co., Ltd.). After confirming that the water content was 24 ppm, 0.4 g of tetramethyl titanate was added. The transesterification reaction was carried out at atmospheric pressure while extracting MMA and methanol azeotropically.

[0141] Next, 1.164 g of silica alumina powder 1 was added to 118.6 g of a sample taken from the resulting reaction solution, and the mixture was stirred for 1 hour while heating at 60°C. The mixture was then filtered using a separatory funnel and filter paper (Kiriyama funnel filter paper No. 4, 60 mm diameter) and concentrated using an evaporator. The concentrated solution was filtered through a 0.45 μm PTFE filter, and the APHA content of the sample was measured. The composition of the reaction solution was also analyzed by GC. The results are shown in Table 4.

[0142] [Example 7] [ka]

[0143] The chemical reaction shown in the above formula was carried out, with the details as follows: A 2-L five-neck flask equipped with a rectification column (internal diameter 35 mm, theoretical plate count 10), a stirring blade, a thermometer, and an air inlet tube was prepared. 59 g of PHEOH (Yokkaichi Synthetic Co., Ltd.), 257 g of MMA, and 0.05 g of MEHQ were placed in the flask. The flask was heated in an oil bath while air was bubbled and stirred. MMA and water were extracted azeotropically at an internal temperature of 100-110°C. The water content of the flask's internal solution was analyzed using a Karl Fischer moisture analyzer (product name: CA-21, Mitsubishi Chemical Analytical Co., Ltd.). After confirming that the water content was 7 ppm, 0.19 g of tetramethyl titanate was added. The transesterification reaction was carried out at atmospheric pressure while extracting MMA and methanol azeotropically.

[0144] Next, 1.164 g of silica alumina powder 1 was added to 134.3 g of a sample taken from the resulting reaction solution, and the mixture was stirred for 1 hour while heating at 60°C. The mixture was then filtered using a separatory funnel and filter paper (Kiriyama funnel filter paper No. 4, 60 mm diameter) and concentrated using an evaporator. The concentrated solution was filtered through a 0.45 μm PTFE filter, and the APHA content of the sample was measured. The composition of the reaction solution was also analyzed by GC. The results are shown in Table 5.

[0145] [Example 8] A 2 L five-neck flask equipped with a rectification column (internal diameter 35 mm, theoretical plate count 10), a stirring blade, a thermometer, and an air inlet tube was prepared. 262 g of PHEOH (Yokkaichi Synthetic Co., Ltd.), 1139 g of MMA, and 0.23 g of MEHQ were placed in the flask. The flask was heated in an oil bath while air was bubbled and stirred. MMA and water were extracted azeotropically at an internal temperature of 100-110°C. The water content of the flask's internal solution was analyzed using a Karl Fischer moisture analyzer (product name: CA-21, Mitsubishi Chemical Analytical Co., Ltd.). After confirming that the water content was 36 ppm, 1.3 g of tetra-n-butyl titanate was added. The transesterification reaction was carried out at atmospheric pressure while extracting MMA and methanol azeotropically. Next, 1.228 g of silica alumina powder 1 was added to 415.6 g of a sample taken from the resulting reaction solution, and the mixture was stirred for 1 hour while heating at 60°C. The mixture was then filtered using a separatory funnel and filter paper (Kiriyama funnel filter paper No. 4, 60 mm diameter) and concentrated using an evaporator. The concentrated solution was filtered through a 0.45 μm PTFE filter, and the APHA content of the sample was measured. The composition of the reaction solution was also analyzed by GC. The results are shown in Table 5.

[0146] [Table 4]

[0147] [Table 5]

[0148] In Examples 6 to 8, APHAs could also be reduced by using silica alumina as an adsorbent containing aluminum oxide and silicon dioxide in the same particle. [Industrial Applicability]

[0149] According to the present invention, a (meth)acrylic acid ester with reduced coloration can be obtained by a simple method.

Claims

1. A method for producing a (meth)acrylic acid ester, comprising: obtaining a reaction liquid containing a (meth)acrylic acid ester by subjecting methyl (meth)acrylate and an alcohol to a transesterification reaction in the presence of a catalyst; contacting the reaction solution with an adsorbent containing aluminum oxide and silicon dioxide in the same particle; A manufacturing method comprising:

2. The process according to claim 1, wherein the transesterification reaction is carried out in the presence of a titanium catalyst.

3. 3. The method according to claim 2, wherein the amount of the adsorbent used is 0.35 to 5.00 kg per 1 mol of the titanium catalyst contained in the reaction solution when the reaction solution is brought into contact with the adsorbent.

4. 2. The method according to claim 1, wherein the reaction solution is brought into contact with the adsorbent at a temperature of 40 to 100°C.

5. The method according to claim 1 , wherein the alcohol comprises a diol which may have an etheric oxygen atom.

6. a transesterification reaction between the methyl (meth)acrylate and the diol to produce at least one selected from the group consisting of a mono(meth)acrylic acid ester and a di(meth)acrylic acid ester, 6. The production method according to claim 5, wherein the reaction solution is contacted with the adsorbent when a proportion of the mono(meth)acrylic acid ester becomes 20 mass% or less of a total amount of the diol, the mono(meth)acrylic acid ester, and the di(meth)acrylic acid ester.

7. The method according to claim 1, wherein silica alumina is used as the adsorbent.

8. A (meth)acrylic acid ester composition comprising a (meth)acrylic acid ester obtained by the production method according to any one of claims 1 to 7.

9. A mono(meth)acrylic acid ester obtained by the production method according to claim 5 or 6; A di(meth)acrylic acid ester obtained by the production method according to claim 5 or 6; A (meth)acrylic acid ester composition comprising:

10. The (meth)acrylic acid ester composition according to claim 9, wherein the content of the mono(meth)acrylic acid ester is 0.1 to 20 mass% of the total amount of the (meth)acrylic acid ester composition.

11. The (meth)acrylic acid ester composition according to claim 8 , wherein the Hazen color number APHA is 100 or less.

12. A (meth)acrylic polymer obtained by polymerizing the (meth)acrylic acid ester obtained by the production method according to any one of claims 1 to 7.

13. A (meth)acrylic polymer obtained by copolymerizing the (meth)acrylic acid ester obtained by the production method according to any one of claims 1 to 7 with another monomer copolymerizable with the (meth)acrylic acid ester.

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