JPH069496A - Production of @(3754/24)meth)acrylic acid esters - Google Patents

Abstract

PURPOSE:To simplify the purification and readily obtain a (meth)acrylic acid ester by carrying out the esterification reaction of (meth)acrylic acids with alcohols in the presence of a water-soluble polymerization inhibitor and a water- soluble esterifying catalyst, then washing the reactional product with water and removing the polymerization inhibitor and the catalyst. CONSTITUTION:The dehydrating esterification reaction of (C1) (meth)acrylic acid with (D) alcohols (e.g. butyl alcohol) or the transesterification reaction of (C2) (meth)acrylic acid esters (e.g. methyl methacrylate) with (D) the alcohols is carried out in the presence of (A) a water-soluble polymerization inhibitor (e.g. potassium hydroquinone-2-sulfonate) and (B) a water-soluble esterifying catalyst (e.g. p-toluenesulfonic acid) and the polymerization inhibitor and the esterifying catalyst are then removed by washing with water to remarkably simplify and reduce the scale of the purification step. Thereby, the objective (meth)acrylic acid esters are obtained without requiring the neutralizing washing with a large amount of an alkali or an acid and the subsequent washing with water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing (meth) acrylic acid esters from which an esterification catalyst and a polymerization inhibitor can be easily removed, and more specifically, a water-soluble polymerization inhibitor and a water-soluble ester. (Meth) acrylic acid and alcohols are subjected to dehydration esterification reaction or (meth) acrylic acid esters and alcohols are subjected to transesterification reaction in the presence of a catalyst for esterification, and then esterified by washing with water. The present invention relates to a method for producing (meth) acrylic acid esters by removing a catalyst and a polymerization inhibitor.

[0002]

2. Description of the Related Art (Meth) acrylic acid ester is a single or other polymerizable monomer, oligomer, polymer, dye,
Radicals produced by thermal decomposition of these initiators, decomposition by ultraviolet rays or radiation irradiation, etc. in the presence of radical initiators such as peroxides, persulfates or azobis compounds by mixing with pigments, inorganic fillers, adjusters, etc. Polymerizes easily by
It produces polymers with excellent mechanical properties, heat resistance, weather resistance and oxidation resistance.

Further, since it is easily copolymerized with various compounds having a carbon-carbon double bond, it is possible to adjust the physical properties of the polymer according to the intended use, and it is possible to adjust the properties of paints, inks, coating agents, adhesives, and tacks. It is used in a wide range of fields as a raw material for agents, resins, rubbers, optical materials and the like.

A method for producing corresponding (meth) acrylic acid esters by dehydration esterification reaction of (meth) acrylic acid and alcohols or transesterification reaction of (meth) acrylic acid esters and alcohols As a general method, the following method is used.

That is, (meth) acrylic acid and alcohols, or (meth) acrylic acid ester of a lower aliphatic alcohol and alcohols are heated and reacted in the presence of an esterification catalyst and a polymerization inhibitor, When the water (or lower alcohol) generated is distilled off azeotropically with a solvent outside the reaction system, the reaction is carried out, and if the target (meth) acrylic acid ester is a low boiling point compound that can be purified by distillation, it is purified by distillation after completion of the reaction. In the case of an impossible high boiling point compound, after the completion of the same, the esterification catalyst and the polymerization inhibitor are removed by washing with an alkali or acid solution, followed by concentration to obtain the desired ester.

As the above esterification catalyst, generally, sulfuric acid, phosphoric acid, methanesulfonic acid, benzenesulfonic acid, p
Acid catalysts such as toluene sulfonic acid, strongly acidic cation exchange resins have been used.

As the polymerization inhibitor, hydroquinone, t
ert-Butyl hydroquinone, methoquinone, 2,4-
Phenolic compounds such as dimethyl-6-tert-butylphenol, catechol and tert-butylcatechol, amines such as phenothiazine, p-phenylenediamine and diphenylamine, copper such as copper dimethyldithiocarbamate, copper diethyldithiocarbamate and copper dibutyldithiocarbamate. One or a combination of compounds such as complexes has been used. Further, one or a combination of powders of selected metals such as copper, manganese and iron, compounds such as oxides, chlorides, sulfates, nitrates and acetates, or a combination thereof has been used in combination.

[0008]

However, in any method using these compounds, after the reaction is completed,
The esterification catalyst and polymerization inhibitor remaining in the system are removed by neutralization washing with an excess of alkali or acid, and then washing with a large amount of water is repeated to adjust the pH of the target (meth) acrylic acid ester. Therefore, there is a problem that the purification process becomes large-scale and complicated.

That is, the ease of neutralization removal depends on the strength of acidity or alkalinity, and the esterification catalyst, unreacted (meth) acrylic acid remaining in the system, and the polymerization inhibitor are neutralized in this order. Therefore, in order to completely remove the polymerization inhibitor,
First of all, it is necessary to neutralize the former two and wash with a large amount of alkali or acid sufficient to neutralize the polymerization inhibitor. Furthermore, after washing, the pH of the target (meth) acrylic acid ester is biased toward the acidic or alkaline side, so that the pH of the ester is adjusted by washing with a large amount of water for the purpose of preventing hydrolysis during storage. It is necessary to adjust to the neutral range. Therefore, in the refining process, a large amount of alkali or acid and water are consumed, and the process also has to be extremely complicated and large-scale, and it is impossible to recover residual (meth) acrylic acid at all. There were challenges.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted earnest studies to solve the above-mentioned problems associated with the conventional method for producing (meth) acrylic acid esters, and as a result, (meth) acrylic acid and alcohols have been obtained. In a dehydration esterification reaction, or in a reaction in which a (meth) acrylic acid ester and an alcohol are transesterified, when a water-soluble polymerization inhibitor and a water-soluble esterification catalyst are used in combination, a relatively small amount after the reaction is completed. The present inventors have found that the polymerization inhibitor and the esterification catalyst can be easily removed only by washing with water, and that the subsequent pH adjustment is unnecessary, and have completed the present invention.

That is, in the present invention, in the presence of a water-soluble polymerization inhibitor (A) and a water-soluble esterification catalyst (B),
After dehydration esterification reaction of (meth) acrylic acid (C ₁ ) and alcohols (D) or transesterification reaction of (meth) acrylic acid esters (C ₂ ) and alcohols (D), washing with water And a polymerization inhibitor (A) and an esterification catalyst (B) are removed by a method of producing a (meth) acrylic acid ester.

The greatest feature of the present invention is that the water-soluble polymerization inhibitor (A) and the water-soluble esterification catalyst (B) are used in combination, so that the polymerization inhibitor (A ) And the esterification catalyst (B) can be completely removed, and the neutralization washing with a large amount of alkali or acid and the subsequent water washing step as in the conventional technique are unnecessary, and the purification step is also remarkably accompanied. It is being simplified and downsized. Further, there is also an advantage that the pH of the (meth) acrylic acid ester after washing is not required to be adjusted and the residual (meth) acrylic acid is not neutralized, so that it can be recovered.

Water-soluble polymerization inhibitor (A) used in the present invention
The polymer may be a water-soluble polymerization inhibitor, and examples thereof include acids having a functional group such as a phenolic hydroxyl group, an amino group, a nitro group and a nitroso group and salts thereof, and salts of selected metals. However, in addition to these, a polymerization inhibitor that changes into a salt and becomes water-soluble by the end of the reaction, such as a transition metal or an oxide thereof, can be mentioned. Usually selected from the group consisting of phenolic hydroxyl groups, amino groups, nitro groups and nitroso groups 1
Aromatic sulfonic acids having at least one kind of functional group or a salt thereof, and a combination of the aromatic sulfonic acid or a salt thereof with a selected metal, an oxide thereof or a salt thereof are used. Among them, the aromatic sulfonic acid is used. Alternatively, it is preferable to use a salt thereof and a salt of a selected metal in combination because polymerization resistance is remarkably excellent.

Examples of the aromatic sulfonic acids and salts thereof include phenol-2-sulfonic acid and phenol-
3-sulfonic acid, phenol-4-sulfonic acid, 2-methyl-1-phenol-4-sulfonic acid, 2-methyl-
1-phenol-6-sulfonic acid, 3-methyl-1-phenol-4-sulfonic acid, 3-methyl-1-phenol-6-sulfonic acid, 4-methyl-1-phenol-6
-Sulfonic acid, 2-tert-butyl-1-phenol-4-sulfonic acid, 2-tert-butyl-1-phenol-6-sulfonic acid, 2,6-dimethyl-1-phenol-4-sulfonic acid, 2 , 3-Dimethyl-1-phenol-4-sulfonic acid, 2,3-dimethyl-1-phenol-6-sulfonic acid, 2,4-dimethyl-1-phenol-6-sulfonic acid, 2,5-dimethyl- 1-phenol-4-sulfonic acid, 2,5-dimethyl-1-phenol-6-sulfonic acid,

Hydroquinone-2-sulfonic acid, hydroquinone-2,5-disulfonic acid, catechol-4-sulfonic acid, catechol-6-sulfonic acid, catechol-
3,5-disulfonic acid, catechol-3,6-disulfonic acid, catechol-4,5-disulfonic acid, pyrogallol-4-sulfonic acid, pyrogallol-5-sulfonic acid,
2-nitro-1-phenol-4-sulfonic acid, 2-nitro-1-phenol-6-sulfonic acid, 2-nitroso-1-phenol-4-sulfonic acid, 2-nitroso-1
-Phenol-6-sulfonic acid, poly (4-vinyl-1)
-Phenol-2-sulfonic acid), poly (2-vinyl-)
1-phenol-4-sulfonic acid), naphtholsulfonic acids, naphthohydroquinonesulfonic acids, naphthoquinonesulfonic acids, nitrosonaphtholsulfonic acids,
Aromatic sulfonic acid compounds containing phenolic hydroxyl groups such as nitronaphthol sulfonic acids, and alkali metal salts or ammonium salts thereof;

2-amino-1-phenol-4-sulfonic acid, 2-amino-1-phenol-6-sulfonic acid,
3-amino-1-phenol-4-sulfonic acid, 3-amino-1-phenol-6-sulfonic acid, 4-amino-
1-phenol-6-sulfonic acid, phenylenediamine sulfonic acids, nitroaniline sulfonic acids, nitrosoaniline sulfonic acids, aminonaphthol sulfonic acids and other amino group-containing aromatic sulfonic acid compounds, and alkali metal salts or ammonium salts thereof These may be used alone or in combination of two or more.

Of these, aromatic sulfonic acids having a phenolic hydroxyl group adjacent to a lower alkyl group and salts thereof, and two phenolic hydroxyl groups are preferred because of their excellent polymerization inhibiting function and water solubility. Aromatic sulfonic acid salts having the above, aromatic sulfonic acid salts having a phenolic hydroxyl group and a nitroso group,

For example, 2-methyl-1-phenol-4-
Sulfonic acid, 2-methyl-1-phenol-6-sulfonic acid, 2-tert-butyl-1-phenol-4-sulfonic acid, 2,6-dimethyl-1-phenol-4-sulfonic acid, 2,3- Dimethyl-1-phenol-4-sulfonic acid, 2,3-dimethyl-1-phenol-6-sulfonic acid, 2,4-dimethyl-1-phenol-6-sulfonic acid, 2,5-dimethyl-1-phenol -4-Sulfonic acid, 2,5-dimethyl-1-phenol-6-sulfonic acid and other aromatic sulfonic acids, and their alkali metal salts or ammonium salts;

Hydroquinone-2-sulfonic acid, naphthohydroquinone-2-sulfonic acid, naphthohydroquinone-5-sulfonic acid, naphthohydroquinone-6-sulfonic acid, 2-nitroso-1-phenol-4-sulfonic acid, 2-nitroso -1-phenol-6-sulfonic acid,
2-nitroso-1-naphthol-4-sulfonic acid, 2-
Nitroso-1-naphthol-5-sulfonic acid, 2-nitroso-1-naphthol-6-sulfonic acid, 2-nitroso-1-naphthol-7-sulfonic acid, 2-nitroso-1
-Alkali metal salts or ammonium salts of aromatic sulfonic acids such as naphthol-8-sulfonic acid are particularly preferred.

Examples of the selected metals, oxides and salts thereof include transition metal powders, transition metal oxides, selected metal chlorides, sulfates, nitrates, acetates and oxalates. However, a chloride, a sulfate or a nitrate which is easily soluble in water is usually used. Further, the kind of the above-mentioned selected metal may be any selected metal having a polymerization preventing function, and examples thereof include copper, manganese, iron, cerium and the like, and usually copper, manganese or iron is used. These compounds may be used alone or in combination.

Among the above polymerization inhibitors (A), compounds having a function as a polymerization preventing function as well as a function as an esterification catalyst (B), for example, aromatic sulfonic acids having a phenolic hydroxyl group adjacent to a lower alkyl group. Etc.,
When this is used, it is not always necessary to use the water-soluble esterification catalyst (B) in combination, as long as the addition amount is sufficient for polymerization inhibition and esterification, only the polymerization inhibitor (A) is used. Can be regarded as the combined use of the esterification catalyst (B).

Water-soluble polymerization inhibitor (A) in the present invention
The addition amount of (meth) acrylic acid (C ₁ ) or (meth)
The amount is usually 0.005 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the total of the acrylic acid esters (C ₂ ) and the alcohols (D).

Although not particularly required, the above water-soluble polymerization inhibitor (A) and the following water-soluble esterification catalyst (B)
, A purified (meth) acrylic acid ester is obtained and then added as a stabilizer, a conventional polymerization inhibitor such as hydroquinone, metoquinone, catechol, etc., may be added in a suitable range as a stabilizer in advance. May be added and used in combination.

Examples of the water-soluble esterification catalyst (B) used in the present invention include water-soluble strongly acidic compounds such as mineral acids, halogenated carboxylic acids, and sulfonic acids. Usually, mineral acids and aroma are used. Group sulfonic acids are used.

The above-mentioned mineral acids include, for example, sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, fuming sulfuric acid, phosphoric acid and hydrochloric acid, and the aromatic sulfonic acids include, for example, benzenesulfonic acid, o-toluenesulfonic acid, m-toluenesulfone. Acid, p-toluenesulfonic acid, xylenesulfonic acid, etc. may be mentioned, and these may be used alone or in combination.

Among these esterification catalysts (B), benzene sulfonic acid and p-toluene sulfonic acid are particularly preferable because they have both excellent esterification catalyst function and water solubility.

The addition amount of the water-soluble esterification catalyst (B) in the present invention is the total weight of (meth) acrylic acid (C ₁ ) or (meth) acrylic acid esters (C ₂ ) and alcohols (D). Usually 0.1 to 1 per 100 parts by weight
It is 0 part by weight, preferably 0.5 to 5 parts by weight.

The (meth) acrylic acid (C
Examples of ₁ ) include acrylic acid and methacrylic acid,
Further, as (meth) acrylic acid esters (C ₂ ),
For example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate,
Examples thereof include lower aliphatic alcohol esters of (meth) acrylic acid such as ethyl methacrylate, propyl methacrylate, and butyl methacrylate. Among these, acrylic acid or methacrylic acid is used in the dehydration esterification reaction with alcohols, and methyl acrylate, ethyl acrylate, methyl methacrylate or ethyl methacrylate is used because the lower boiling points of the lower alcohols produced in the transesterification reaction are low. Is preferably used.

As the alcohol (D) used in the present invention, any compound can be used as long as it contains at least one alcoholic hydroxyl group. Examples of such compounds include butyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol,
Alkyl type alcohols such as isodecyl alcohol, 2-ethylhexyl alcohol, dodecyl alcohol, lauryl alcohol, palmityl alcohol and stearyl alcohol;

Methoxyethyl alcohol, ethoxyethyl alcohol, butoxyethyl alcohol, methoxydiethylene glycol, ethoxydiethylene glycol,
Alkoxy group-containing alcohols such as butoxydiethylene glycol, methoxytripropylene glycol, ethoxytripropylene glycol, butoxytripropylene glycol, methoxypolyethylene glycol, methoxypolypropylene glycol;

Cyclic alkyl type alcohols such as cyclopentyl alcohol, cyclohexyl alcohol, cyclooctyl alcohol, methylcyclohexyl alcohol and ethylcyclohexyl alcohol; tetrafurfryl type alcohols such as tetrafurfryl alcohol and methyltetrafurfrel alcohol. Isobornyl alcohols such as isobornyl alcohol and methylisobornyl alcohol; heterocyclic aliphatic group-containing alcohols such as dicyclopentenyl alcohol, dicyclopentadienyl alcohol, dicyclopentenyloxyethyl alcohol;

Tert-Butylaminoethyl alcohol, N, N-dimethylaminoethyl alcohol, N, N
-Amino group-containing alcohols such as diethylaminoethyl alcohol; fluorine-containing alcohols such as tetrafluoropropyl alcohol and heptadecafluorodecyl alcohol; benzyl group-containing alcohols such as benzyl alcohol;

Phenyl group-containing alcohols such as phenol and methylphenol; phenoxy group-containing alcohols such as phenoxyethyl alcohol, phenoxydiethylene glycol, phenoxytriethylene glycol and phenoxyhexaethylene glycol; alkylene oxide-modified phosphate alcohols, Monovalent alcohols such as ε-caprolactone-modified hydroxy alcohol, ε-caprolactone-modified tetrahydrofurfuryl alcohol and other modified hydroxyl groups modified with ε-caprolactone or alkylene oxide;

Alkyl alcohols having hydroxyl groups at both ends such as 1,4-butanediol, 1,6-hexanediol and neopentyl glycol; ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, Alkylene glycol type alcohols such as tripropylene glycol and polypropylene glycol; ester type both-end hydroxyl group-containing alcohols such as ethylene glycol hydroxypivalate, diethylene glycol hydroxypivalate and neopentyl glycol hydroxypivalate;

Trimethylolpropane, ethoxytrimethylolpropane, propoxytrimethylolpropane, ditrimethylolpropane, ethoxyditrimethylolpropane, propoxyditrimethylolpropane,
ε-caprolactone modified trimethylolpropane, ε-
Alcohols of trimethylolpropane and its derivatives, such as caprolactone-modified ditrimethylolpropane;

Of pentaerythritol and derivatives thereof such as pentaerythritol, ethoxypentaerythritol, propoxypentaerythritol, dipentaerythritol, ethoxydipentaerythritol, propoxydipentaerythritol, ε-caprolactone modified pentaerythritol, ε-caprolactone modified dipentaerythritol and the like. Alcohols;

Trihydroxyisocyanurate, tris (hydroxyethyl) isocyanurate, tris (ethylene oxide modified) isocyanurate, tris (propylene oxide modified) isocyanurate, tris (ε-
Caprolactone-modified) isocyanurate such as isocyanurate and its derivative alcohols;

Alcohols of heterocyclic derivatives such as di (hydroxyethyl) dicyclopentadiene; ethylene oxide-added bisphenol A, propylene oxide-added bisphenol A, ethylene oxide-added hydrogenated bisphenol A, propylene oxide-added hydrogenated bisphenol A, ε- Modified alcohols of bisphenol compounds such as caprolactone-modified bisphenol A, ethylene oxide-added bisphenol S, propylene oxide-added bisphenol S, ethylene oxide-added hydrogenated bisphenol S, propylene oxide-added hydrogenated bisphenol S, and ε-caprolactone-modified bisphenol S;

Glycerin, ethylene oxide-added glycerin, propylene oxide-added glycerin, ε
Examples thereof include polyhydric alcohols such as captolactone-modified glycerin, but usable alcohols are not limited thereto.

The (meth) acrylic acid (C
₁ ) or (meth) acrylic acid ester (C ₂ ) is used in an amount of (meth) acrylic acid (C ₁ ) or (meth) based on 1.0 of the number of hydroxyl groups in the alcohol (D). ) acrylic acid esters (C ₂₎ can be widely varied with 0.03 to 30 units. However, when the alcohol removed after the reaction can be distilled off by distillation, 0.03 to 1.
It is 0, and among them, 0.10 to 0.95 are preferable in that the reaction proceeds rapidly and there is no side reaction or formation of a coloring substance. When the alcohol to be removed after completion of the reaction cannot be removed by distillation, it is usually 1.0 to 30, and among them, the reaction proceeds rapidly and side reactions and the formation of coloring substances are not generated. 0.05 to 10 are preferable.

The dehydration esterification reaction or transesterification reaction in the present invention can be carried out in an organic solvent or in the absence of a solvent. As the solvent, benzene, toluene, xylene, hexane, cyclohexane, heptane, octane,
Nonane, methylcyclohexane, etc., which are phase-separated from water when mixed with water and can be azeotroped with water or a lower alcohol produced by a transesterification reaction, and have a boiling point of 60 to 1
Those in the range of 40 ° C. are used. These solvents may be used alone or as a mixture, and may be used even if the solvents are incompatible with the starting alcohols or incapable of dissolving them. The amount added is usually in the range of 0 to 300% by weight with respect to the total amount of the reaction system.

The reaction temperature in the present invention is usually 40 to 20.
It is selected from the range of 0 ° C, preferably 60 to 120 ° C, and the reaction time is usually 0.5 to 20 hours, preferably 1 to 1
It is set to about 5 hours. Among them, the reaction temperature is 60 to 80 ° C. and the reaction time is 3 to 12 hours, which is the most preferable in that the desired (meth) acrylic acid ester can be obtained in high purity.

The reaction in the present invention may be carried out under atmospheric pressure, under reduced pressure for easily removing the produced water or alcohol out of the reaction system, or for reducing the boiling point of the solvent. It may be carried out under pressure, or under any pressure.

In the reaction of the present invention, (meth) acrylic acid (C ₁ ) or (meth) acrylic acid ester (C
₂ ) and oxygen or a mixture of oxygen and an inert gas, such as air or oxygen / argon mixed gas, in the reaction liquid and / or on the reaction liquid surface over the entire reaction time in order to prevent polymerization of the (meth) acrylic acid ester formed. When introduced, the effect of preventing polymerization is further improved. At this time, it is preferable to blow oxygen or a mixture of oxygen and an inert gas into the reaction solution so as to form fine bubbles so that water generated by the esterification reaction is quickly removed, and gas near the contact interface is also preferable. Blowing into the phase is preferable from the viewpoint of preventing polymerization on the surface of the reaction vessel and in the contact area between the reaction liquid and the gas phase. In any case, it is preferable to carry out the blowing into the system since it can prevent the polymerization during the reaction in the liquid or in the gas phase and promote the reaction.

The water-soluble polymerization inhibitor and the water-soluble esterification catalyst in the present invention can be removed by washing with water. The reaction liquid after completion of the reaction can be diluted with an organic solvent that is compatible with the reaction liquid and phase-separates from water at an arbitrary ratio. The method of washing with water is not particularly limited, and any commonly used method such as stirring and extraction can be used, and the amount of washing water, the number of washings, etc. can be changed as necessary. It is also possible to wash with an aqueous solution in which neutral salts are dissolved during washing. Examples of usable neutral salts include alkali metal sulfates, chlorides, nitrates, alkaline earth metal sulfates, chlorides, nitrates, etc., which have good solubility in water. If it is a thing, it will not be specifically limited to these.

The water-soluble polymerization inhibitor (A) and the water-soluble esterification catalyst (B) removed in the present invention are in the state of an aqueous solution as they are, in the state of being concentrated into a concentrated aqueous solution, or by evaporation to dryness. It is also possible to use it in the reaction again in the reaction state.

In the method for producing (meth) acrylic acid esters in the present invention, the water-soluble polymerization inhibitor (A)
After completion of the removal of both the water-soluble esterification catalyst (B) and the water-soluble esterification catalyst (B), the recovery of the (meth) acrylic acid or (meth) acrylic acid esters and the solvent remaining in the reaction solution is extracted as necessary. Purification such as removal of coloring components and reaction by-products can be carried out by a method such as distillation and adsorption, crystallization, reprecipitation, filtration and the like. Any of these generally known purification methods can be used, and they can be used alone or in combination.

Since the purified (meth) acrylic acid esters thus obtained have the property of being easily polymerized,
When it is used immediately in some polymerization step, or when it is stored, it is necessary to add a new polymerization inhibitor. In this case, as the type of the polymerization inhibitor, hydroquinone and metoquinone are mainly used, but metoquinone is particularly preferably used in that there is no modified coloring. The addition amount depends on the kind of the (meth) acrylic acid ester obtained, but is usually 5 to 5000 ppm, preferably 50 to 2500.
It is ppm.

[0049]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the contents of the present invention are not limited to the examples. Further, the following% is based on weight unless otherwise specified.

The purification methods (1) and (2) used in Examples and Comparative Examples, the removal rate of the polymerization inhibitor, the removal rate of the esterification catalyst, the presence or absence of the polymer, the recovered amount of (meth) acrylic acid,
The method for obtaining the (meth) acrylic acid ester yield and the alcohol conversion rate is shown below.

Purification method (1) Pure water corresponding to 20% by weight of this reaction solution was added to this reaction diluted solution, stirred for 20 minutes, and allowed to stand for 4 hours to separate the upper layer solution. This washing operation was repeated 3 times. Next, 0.08 g of methoquinone was added to this upper layer solution, and the mixture was heated to 70 ° C. to first recover the solvent under reduced pressure, and further distillate and recover the residual (meth) acrylic acid under high reduced pressure, and use diatomaceous earth as a filter aid. Dust and the like mixed during each operation were filtered to obtain the target (meth) acrylic acid ester.

Purification method (2) The desired (meth) acrylic acid ester was obtained in the same manner as in the purification method (1) except that the number of washing operations with pure water was changed to 5.

Polymerization inhibitor removal rate It was calculated from the content of the polymerization inhibitor in the reaction solution before and after purification, which was measured by ion chromatography (however, in the case of a transition metal salt, an atomic absorption spectrophotometer). -Esterification catalyst removal rate It was calculated from the content of the esterification catalyst in the reaction solution before and after purification, which was measured by ion chromatography.

Presence / Absence of Polymer Methyl alcohol was added 4 times by volume to the reaction solution after the reaction, and the presence / absence of a polymer was determined by the presence / absence of cloudiness. -(Meth) acrylic ester yield Calculated from the amount of (meth) acrylic ester after purification and the theoretical yield. -Alcohol reaction conversion rate The amount of alcohol before and after the reaction was measured and calculated by gas chromatography. -(Meth) acrylic acid ester purity The purity of (meth) acrylic acid ester after purification by GPC measurement [content of (meth) acrylic acid ester monomer in the purified product including monomers and multimers] I asked.

Examples 1 to 39 and Comparative Examples 1 to 4 In a 1-liter glass four-necked flask equipped with a reflux condenser, a water separator, an air introduction tube, a thermometer, a stirrer and a dropping funnel, Table 1
The amounts of the polymerization inhibitor, the esterification catalyst, the alcohol, the (meth) acrylic acid, and the solvent shown in to 8 were charged. Next, while blowing air at 20 ml / min into this flask,
While heating using a hot water bath and stirring the inner solution, the solvent and by-produced water start to azeotropically evaporate, and the reaction times shown in Tables 1 to 8 are followed in Examples 1 to 35 under atmospheric pressure. Example 3
In Nos. 6 to 39, under the reduced pressure shown in Table 8, only the solvent was refluxed while azeotropically removing water by the water separator, and the reaction was carried out at the reaction temperatures shown in Tables 1 to 8. Immediately after completion of the reaction,
After adding the amount of the diluent solvent shown in Fig. 8 and cooling to room temperature and purifying this reaction diluted solution by the purification method shown in Tables 1 to 8, polymerization inhibitor removal rate, esterification catalyst removal rate, polymer Presence / absence, yield of (meth) acrylic acid ester and conversion rate of alcohol reaction were determined. The results are shown in Tables 1-8. In Comparative Examples 1 to 4, in order to remove 100% of the polymerization inhibitor, neutralization washing with a large amount of alkali was necessary.

[0056]

[Table 1]

[0057]

[Table 2]

[0058]

[Table 3]

[0059]

[Table 4]

[0060]

[Table 5]

[0061]

[Table 6]

[0062]

[Table 7]

[0063]

[Table 8]

The water-soluble polymerization inhibitors 1-24 and the water-soluble esterification catalyst 1-shown in Tables 1 to 8 and Tables 9 to 11 below.
4 is as follows. Water-soluble polymerization inhibitor 1: Hydroquinone-2-sodium sulfonate 〃 2: Hydroquinone-2-potassium sulfonate 〃 3: Ammonium hydroquinone-2-sulfonate 〃 4: Manganese sulfate 〃 5: Manganese chloride 〃 6: Manganese nitrate 〃 7: Copper sulfate 〃 8: Cupric chloride 〃 9: Copper nitrate 〃 10: Ferrous sulfate 〃 11: Ferric chloride 〃 12: Iron nitrate

〃 13: Phenol-4-sulfonic acid 〃 14: Sodium phenol-4-sulfonic acid 〃 15: 2-Methyl-1-phenol-4-sulfonic acid 〃 16: 2-Methyl-1-phenol-4- Potassium sulfonate 〃 17: 2,6-dimethyl-1-phenol-4-sulfonic acid 〃 18 ： Potassium 2,6-dimethyl-1-phenol-4-sulfonate 〃 19 ： Potassium naphthohydroquinone-2-sulfonate 〃 20: 2-nitroso-1-phenol-4-sulfonic acid potassium 〃 21: 2-nitroso-1-naphthol-4-sulfonic acid potassium 〃 22: 1-naphthol-4-sulfonic acid potassium 〃 23: 1 -Aniline-4-potassium sulfonate 〃 24: potassium p-phenylenediamine-2-sulfonate Beam

Water-soluble esterification catalyst 1: benzenesulfonic acid 〃 2: p-toluenesulfonic acid 〃 3: 1,2-xylene-4-sulfonic acid 〃 4: sulfuric acid

Examples 40-52 and Comparative Examples 5-8 1 equipped with a rectification column, a reflux condenser with a solenoid valve equipped with a temperature sensor, an air inlet tube, a thermometer, a stirrer and a dropping funnel.
1 water-soluble polymerization inhibitor (A), water-soluble esterification catalyst (B), in an amount shown in Tables 8 to 10 in a glass four-necked flask,
Alcohol and methyl (meth) acrylate were charged.
Next, while blowing air at 20 ml / min into this flask, the inner solution was stirred and heated using a water bath. The column top temperature of the rectification column is set to a temperature shown in Tables 9 to 11, and an azeotropic solution of methyl (meth) acrylate and methyl alcohol produced as a by-product is distilled at a temperature not higher than the set temperature, and the temperature becomes higher than the set temperature. In the case of contact, it was completely refluxed. The reaction is shown in Tables 9 to 11 after methyl (meth) acrylate and methyl alcohol start azeotropic distillation.
The above azeotrope was separated at the reaction temperatures shown in Tables 9 to 11 during the reaction time shown in Table 1. After the reaction,
It heated at 60-80 degreeC under reduced pressure, and distilled and collect | recovered the residual methyl (meth) acrylate. Immediately thereafter, Tables 9-11
The reaction mixture was cooled to room temperature by adding the amount of the diluent solvent shown in Table 1, and the reaction diluted solution was purified using the purification methods shown in Tables 9 to 11, followed by removal rate of the polymerization inhibitor, removal rate of the esterification catalyst, and presence or absence of polymer. , (Meth) acrylic acid ester yield and alcohol reaction conversion were determined. The results are shown in Tables 9-11. In Comparative Examples 5 to 8, in order to remove the polymerization inhibitor by 100%, neutralization washing with a large amount of alkali was necessary.

[0068]

[Table 9]

[0069]

[Table 10]

[0070]

[Table 11]

[0071]

According to the production method of the present invention, the polymerization inhibitor and the esterification catalyst can be removed only by washing with water after the completion of the reaction. Therefore, as in the prior art, neutralization washing with a large amount of alkali or acid is carried out. And the subsequent water washing process becomes unnecessary,
Along with this, there is an advantage that the purification process is remarkably simplified and the scale is reduced. Further, it is not necessary to adjust the pH of the (meth) acrylic acid ester after washing, and the residual (meth) acrylic acid remains.
Since acrylic acid is not neutralized, there is also an advantage that it can be recovered.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location // C07B 61/00 300

Claims (9)

[Claims] 1. A dehydration esterification reaction of (meth) acrylic acid (C ₁ ) and an alcohol (D) in the presence of a water-soluble polymerization inhibitor (A) and a water-soluble esterification catalyst (B). Or a (meth) acrylic acid ester (C ₂ ) and an alcohol (D) are subjected to transesterification reaction, followed by washing with water to remove the polymerization inhibitor (A) and the esterification catalyst (B). And a method for producing (meth) acrylic acid esters. 2. The polymerization inhibitor (A) is an aromatic sulfonic acid having at least one functional group selected from the group consisting of a phenolic hydroxyl group, an amino group, a nitro group and a nitroso group, or a salt thereof. 1. The manufacturing method according to 1. 3. The polymerization inhibitor (A) comprises an aromatic sulfonic acid having a phenolic hydroxyl group adjacent to a lower alkyl group, a salt thereof, a salt of an aromatic sulfonic acid having two or more phenolic hydroxyl groups, and a pheno. The method according to claim 1, which is one or more compounds selected from the group consisting of salts of aromatic sulfonic acids having a hydroxyl group and a nitroso group. 4. The production method according to claim 1, 2 or 3, wherein the reaction temperature of the dehydration esterification reaction or the transesterification reaction is 60 to 80 ° C. 5. The production method according to claim 2, 3 or 4, wherein a salt of a transition metal is further used as the polymerization inhibitor (A). 6. The method according to claim 5, wherein the transition metal salt is a salt of at least one metal selected from the group consisting of copper, iron and manganese. 7. The process according to claim 2, 3 or 4, wherein the water-soluble esterification catalyst (B) is a mineral acid or an aromatic sulfonic acid. 8. The method according to claim 2, 3 or 4, wherein the water-soluble esterification catalyst (B) is benzenesulfonic acid or p-toluenesulfonic acid. 9. The production method according to claim 1, wherein the alcohol (D) is a polyhydric alcohol.