JPH0840980A - Method for producing (meth) acrylic acid esters - Google Patents

Abstract

(57) [Summary] [Structure] Water-soluble compound (A) having both polymerization prevention function and esterification catalyst function, water-soluble esterification catalyst (B) other than (A), and other than (A) In the presence of a water-soluble polymerization inhibitor (C) such as 2-methyl-1-phenol-4-sulfonic acid, p-toluenesulfonic acid and copper sulfate (meth) acrylic acid (D) and alcohols ( E) is subjected to dehydration esterification reaction in an inert gas atmosphere having an oxygen content of preferably 5 to 13% by volume, and then washed with reaction water separated from the reaction system and washed with A) and (B). And (C) are removed, followed by washing with an aqueous alkaline solution, preferably further washing with an aqueous solution of a neutral salt such as sodium sulfate, to produce a (meth) acrylic acid ester. [Effect] The amount of the esterification catalyst used can be reduced, and the waste liquid can be significantly reduced. Moreover, the high molecular weight by-product can be easily removed by washing the reaction liquid with an alkaline aqueous solution and then with an aqueous solution of a neutral salt.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing (meth) acrylic acid esters.

[0002]

2. Description of the Related Art (Meth) acrylic acid esters are used alone or in combination with other polymerizable monomers, oligomers, polymers, dyes, pigments, inorganic fillers, adjusters, etc.
In the presence of radical initiators such as persulfates or azobis compounds, they are easily polymerized by radicals generated by thermal decomposition of these initiators or decomposition by irradiation of ultraviolet rays or radiation, and mechanical properties, heat resistance, weather resistance, acid resistance, etc. It produces a polymer with excellent chemical properties.

Further, (meth) acrylic acid esters are
Since it is easily copolymerized with various compounds having carbon-carbon double bonds, it is possible to adjust the physical properties of the polymer according to the application. Paints, inks, coating agents, adhesives, pressure sensitive adhesives, resins, rubbers. It is widely used as a raw material for optical materials.

The conventional (meth) acrylic acid and alcohols are dehydrated and esterified to obtain the corresponding (meth)
The following methods are generally used for producing acrylic acid esters.

That is, (meth) acrylic acid and alcohols are mixed in an air atmosphere with a polymerization inhibitor and a large amount of an esterification catalyst [for example, a total amount of 100 parts by weight of (meth) acrylic acid and alcohols is It is 2 in fairness 2-10137
8.3 parts by weight, and 8.3 parts by weight in JP-A 1-258643] are used to cause a reaction by heating, and water produced is azeotropically distilled out of the reaction system using an organic solvent. While reacting, and after completion of the reaction, the polymerization inhibitor and the esterification catalyst are removed by washing with an alkali or acid solution, then the residual alkali is washed with water and concentrated to obtain the desired (meth) acrylic acid ester. Is the way. still,
The reason why the reaction is carried out in an air atmosphere is to enhance the polymerization preventing effect of the polymerization inhibitor.

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 above-mentioned polymerization inhibitors, phenol compounds such as hydroquinone, tert-butylhydroquinone, methoquinone, 2,4-dimethyl-6-tert-butylphenol, catechol and tert-butylcatechol, phenothiazine, p-phenylene. One or a mixture of amines such as diamine and diphenylamine, copper dimethyldithiocarbamate, copper diethyldithiocarbamate, copper complex such as copper dibutyldithiocarbamate and the like, or a mixture thereof has been used. Further, if necessary, one or a mixture of powders of transition metals such as copper, manganese and iron, compounds such as oxides, chlorides, sulfates, nitrates and acetates, or a mixture thereof has been used together. .

[0008]

However, in these conventional methods, after completion of the reaction, the polymerization inhibitor remaining in the system and a large amount of the esterification catalyst are removed by neutralization washing with an excess of alkali or acid, After that, washing with a large amount of water was repeated to obtain the desired (meth) acrylic acid ester, so that there was a problem that the amount of waste liquid became large. Further, the water of reaction obtained by separating from the reaction system contains unreacted (meth) acrylic acid and the like, and this is also treated as a waste liquid, so that there is a problem that the waste liquid increases accordingly.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems associated with the conventional method for producing (meth) acrylic acid esters, and as a result, have found that they have a polymerization-preventing function and an esterification-catalyst function. When a water-soluble compound having both of the following is used in combination with a water-soluble esterification catalyst other than the compound and a water-soluble polymerization inhibitor other than the compound, the esterification catalyst (polymerization prevention function and esterification catalyst function It is possible to reduce the amount of the water-soluble compound having a combination of and a water-soluble esterification catalyst other than the compound), and to use the small amount of reaction water separated from the reaction system in the dehydration esterification reaction to obtain the ester. The catalyst and polymerization inhibitor can be easily removed by washing with water,
It was found that the amount of waste liquid can be remarkably reduced, and the present invention has been completed.

Further, the inventors of the present invention wash the unreacted (meth) acrylic acid remaining in the reaction system with an aqueous alkaline solution and then wash it with an aqueous solution of a neutral salt, thereby producing a water-insoluble high molecular weight compound. It was also found that the filtration characteristics of the by-products are improved and that high-purity (meth) acrylic acid esters can be easily obtained.

Further, the present inventors have found that a water-soluble compound having both a polymerization preventing function and an esterification catalyst function, a water-soluble esterifying catalyst other than the compound, and a water-soluble polymerization preventing agent other than the compound. When a dehydration esterification reaction is carried out in an inert gas atmosphere with an oxygen content of 5 to 13% by volume in combination with an agent, flammability in the reaction system is enhanced in a state where the polymerization inhibitory effect of the polymerization inhibitor is enhanced. It was also found that the danger of compound explosion can be significantly reduced and high safety can be ensured.

That is, the present invention provides a water-soluble compound (A) having both a polymerization preventing function and an esterification catalyst function, a water-soluble esterification catalyst (B) other than the compound (A), and the compound. Obtained by subjecting (meth) acrylic acid (D) and alcohols (E) to a dehydration esterification reaction in the presence of a water-soluble polymerization inhibitor (C) other than (A), and then separating from the reaction system. The compound (A), the esterification catalyst (B) and the polymerization inhibitor (C) are washed with water to remove the compound (A), followed by washing with an aqueous alkali solution. Production method,

In the above-mentioned method for producing (meth) acrylic acid esters, the method for producing the (meth) acrylic acid esters, which comprises washing with an aqueous alkaline solution and then washing with an aqueous solution of a neutral salt, The present invention provides a method for producing a dehydration esterification reaction in an inert gas atmosphere having a rate of 5 to 13% by volume.

As the water-soluble compound (A) having both a polymerization preventing function and an esterification catalyst function used in the present invention,
Examples thereof include acids having a functional group such as a phenolic hydroxyl group, an amino group, a nitro group and a nitroso group, or salts thereof. Among these, preferred are aromatic sulfonic acids having one or more functional groups selected from the group consisting of phenolic hydroxyl group, amino group, nitro group and nitroso group, alkali metal salts or ammonium salts thereof. Is mentioned.

Examples of the aromatic sulfonic acids, alkali metal salts or ammonium salts thereof include phenol-2-sulfonic acid, 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),

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- Four
-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-naphthol Aromatic sulfonic acid compounds containing phenolic hydroxyl group such as -8-sulfonic acid,
Their sodium, potassium or ammonium salts;

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-
Amino group-containing aromatic sulfonic acid compounds such as 1-phenol-6-sulfonic acid, phenylenediamine sulfonic acids, nitroaniline sulfonic acids, nitrosoaniline sulfonic acids, aminonaphthol sulfonic acids, their sodium salts, potassium salts, ammonium salts, etc. These may be used alone or in combination of two or more.

Among these, the aromatic sulfone having a lower alkyl group and a phenolic hydroxyl group has a high polymerization preventing function and a high esterification catalyst function, is well balanced, and has excellent solubility in water. Acids, alkali metal salts or ammonium salts thereof (wherein the lower alkyl group represents an alkyl group having 1 to 4 carbon atoms), 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-
Aromatic sulfonic acids such as sulfonic acid, and their sodium salts, potassium salts, ammonium salts and the like can be mentioned.
It should be noted that among the above-mentioned aromatic sulfonic acids and their salts, aromatic sulfonic acids are more preferable in that the yield is relatively high.

In the present invention, the amount of the water-soluble compound (A) having both the polymerization preventing function and the esterification catalyst function is 100 parts by weight of the total weight of the (meth) acrylic acid (C) and the alcohols (D). On the other hand, it is usually 0.005 to 10 parts by weight, preferably 0.1 to 2 parts by weight.

Although not particularly necessary, the above compound (A) and the following water-soluble esterification catalyst (B) and water-soluble polymerization inhibitor (C) other than this compound (A) are removed,
If a stabilizer is added after obtaining a purified (meth) acrylic acid ester, the stabilizer (C) is previously added in an appropriate amount in the above range to the compound (A), the esterification catalyst (B), the polymerization inhibitor (C). ) May be used in combination. Examples of the stabilizer used here include conventional polymerization inhibitors such as hydroquinone, metoquinone, and catechol.

Examples of the water-soluble esterification catalyst (B) other than the above compound (A) used in the present invention include acidic compounds other than the above compound (A), among which mineral acids, halogenated carboxylic acids, sulfonic acids and the like. The strongly acidic compounds having water solubility, particularly mineral acids and aromatic sulfonic acids, are preferable.

The above-mentioned mineral acids include, for example, sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, fuming sulfuric acid, phosphoric acid, hydrochloric acid, and the like, and aromatic sulfonic acids include, for example, benzenesulfonic acid,
o-toluenesulfonic acid, m-toluenesulfonic acid, p
-Toluene sulfonic acid, xylene sulfonic acid, etc. are mentioned respectively, 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 esterification catalyst (B) in the present invention is usually 0.1 to 10 relative to 100 parts by weight of the total of (meth) acrylic acid (D) and alcohols (E).
Parts by weight, preferably 0.5 to 6 parts by weight.

Examples of the water-soluble polymerization inhibitor (C) other than the above compound (A) used in the present invention include transition metals other than the above compound (A), transition metal oxides, transition metal salts, etc. Examples thereof include powders of metals, oxides of transition metals, chlorides of transition metals, sulfates, nitrates, acetates, oxalates, etc. Usually, chlorides, sulfates or nitrates which are easily water-soluble are used.

Further, the kind of the above transition metal may be any transition metal having a polymerization preventing function, and examples thereof include copper, manganese, iron, cerium and the like, but copper, manganese or iron is usually used. These compounds may be used alone or in combination. Specific examples include cuprous chloride, copper sulfate, copper nitrate, manganese chloride, manganese sulfate, manganese nitrate, ferrous chloride, ferrous sulfate, and nitric acid first.
Examples include iron.

The addition amount of the polymerization inhibitor (C) in the present invention is usually such that the concentration of the polymerization inhibitor (C) in the reaction system is 50 to 2
000 ppm, preferably 100-1000 p
The amount is pm.

(Meth) acrylic acid (D) used in the present invention
Examples thereof include acrylic acid and methacrylic acid. As the alcohol (E) 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, isodecyl alcohol, 2-ethylhexyl alcohol, dodecyl alcohol, lauryl alcohol, palmityl alcohol, stearyl alcohol, etc. Alkyl alcohols of

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, 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;

Pentaerythritol such as pentaerythritol, ethoxypentaerythritol, propoxypentaerythritol, dipentaerythritol, ethoxydipentaerythritol, propoxydipentaerythritol, ε-caprolactone-modified pentaerythritol, ε-caprolactone-modified dipentaerythritol, and derivatives thereof. 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 a heterocyclic derivative 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. Among them, polyhydric alcohols, particularly dihydric alcohols are preferable from the viewpoint of easy adjustment of the esterification ratio.

(Meth) acrylic acid (D) in the present invention
The amount used is 1.0 for the number of hydroxyl groups in the alcohols (E).
The number of (meth) acrylic acid can be varied widely from 0.03 to 30 per unit, but usually 1.0 to 30.
Among them, 1.05 to 5 are preferable in that the reaction proceeds rapidly and side reactions and the formation of coloring substances do not occur.

The dehydration esterification reaction in the present invention can be carried out in an organic solvent or without a solvent, but is usually carried out in an organic solvent because it is easy to control the reaction and remove reaction water. Examples of the organic solvent used here include benzene, toluene, xylene, hexane, cyclohexane, heptane, octane, nonane, methylcyclohexane, and the like, which are phase-separated from water when mixed with water and are azeotropic with water. Those having a boiling point in the range of 60 to 140 ° C. are usually used, and among them, the aromatic hydrocarbons are excellent in solubility of the (meth) acrylic acid ester, the compound (A) and the esterification catalyst (B). Especially preferred is toluene.

These solvents may be used alone or as a mixture thereof, and may be used even if the solvent is incompatible with the alcohol as a raw material or incapable of dissolving them. The addition amount is usually 0 to 300 parts by weight, preferably 20 to 150 parts by weight, based on 100 parts by weight of the total of (meth) acrylic acid (D) and alcohols (E).

The reaction temperature in the present invention is usually 40 to 1.
The temperature is 40 ° C., preferably 60 to 90 ° C., and the reaction time is usually 0.5 to 50 hours, preferably 1 to 20 hours. The reaction in the present invention can be carried out under atmospheric pressure, under reduced pressure to easily remove the produced water of reaction out of the reaction system, or under pressure to raise the reaction temperature. Any pressure may be used.

In the reaction of the present invention, oxygen or a mixture of oxygen and an inert gas such as air or an oxygen / argon mixed gas is used to prevent the polymerization of (meth) acrylic acid (D) and the produced (meth) acrylic acid ester. When introduced into the reaction solution and / or on the surface of the reaction solution over the entire reaction time, the polymerization inhibiting effect is further improved. The mixing ratio of the oxygen and the inert gas is not particularly limited, but it is preferable to use an inert gas having an oxygen content of 5 to 13% by volume from the viewpoint of safety in preventing ignition and explosion. The flow rate of this gas is not limited as long as it does not impair the polymerization prevention effect, but from the economical point of view, it is 0.1 to 10 ml / mole of (meth) acrylic acid charged.
Minutes are preferred.

At this time, if oxygen or a mixture of oxygen and an inert gas is blown into the reaction solution so as to form fine bubbles, the efficiency of the polymerization-preventing effect becomes high, and the water produced by the esterification reaction is rapidly produced. Is preferable, and blowing into the gas phase in the vicinity of the contact interface is preferable from the viewpoint of preventing polymerization in the contact region between the surface of the reaction vessel, the reaction solution 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 method of washing with reaction water in the present invention is as follows:
The method is not particularly limited, and any commonly used method such as stirring and extraction may be used, and the amount of reaction water used for washing, the number of times of washing, and the like can be changed as necessary. The amount of reaction water used for washing is sufficient if the reaction water is obtained by separating from the reaction system.

In the present invention, the washing water obtained by washing with the reaction water contains the water-soluble polymerization inhibitor (A) and / or the esterification catalyst (B) and unreacted (meth) acrylic acid. It can be reused for the reaction in the state of the aqueous solution as it is, in the state of being concentrated to a concentrated aqueous solution, or in the state of being evaporated to dryness.

In the method for producing (meth) acrylic acid esters of the present invention, after the washing with reaction water is completed, the remaining unreacted (meth) acrylic acid can be removed by washing with an alkaline aqueous solution. However, the method of washing with an aqueous solution of a neutral salt and / or with water after washing with an alkaline aqueous solution has good quality such as hue of the product, and particularly unreacted (meth) acrylic acid is washed with an alkaline aqueous solution. After the removal, the high molecular weight by-products and the like are washed with an aqueous solution of a neutral salt to be removed, and if necessary, washing is also used in combination, which is preferable in that the filtration characteristics of the product are improved.

At this time, the washing method is not particularly limited as long as the mixed washing can be easily performed, and any of commonly used methods such as stirring, extraction and centrifugation may be used. Further, if necessary, a refined production method in which (meth) acrylic acid or a solvent remaining in the reaction solution is recovered by a method such as extraction or distillation and then combined with the above washing method is also possible.

In washing with an alkaline aqueous solution, an alkaline aqueous solution having a concentration in which an alkaline salt is dissolved can be used, but an aqueous solution of 0.5 to 25% by weight is preferable. The amount of the alkaline aqueous solution used is 0.8 to 2.0 with respect to the neutralization equivalent of the reaction solution that has been washed with the reaction water.
Aqueous solution containing double amount of alkali, preferably 1.0-1.
An aqueous solution containing twice the amount of alkali can be used. At this time, the addition of the alkaline aqueous solution may be carried out collectively or in a divided manner.

The alkalis that can be used for washing with an aqueous alkali solution are not particularly limited as long as they are water-soluble alkalis. For example, hydroxides, carbonates, phosphates or alkaline earth metals of alkali metals are used. Metal hydroxides, carbonates, phosphates and the like are used, among which sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, particularly sodium hydroxide and potassium hydroxide are preferable.

In washing with an aqueous solution of a neutral salt, any neutral salt concentration can be used as long as the neutral salt is dissolved, but an aqueous solution of 0.5 to 25% by weight is preferable. The amount of the neutral salt aqueous solution used is usually 1 to 100 parts by weight of the reaction solution which has been washed with the alkaline aqueous solution.
200 parts by weight, preferably 5 to 50 parts by weight.

The neutral salt that can be used for washing with an aqueous solution of a neutral salt is not particularly limited as long as it is a water-soluble neutral salt, and examples thereof include sulfates and hydrochlorides of alkali metals. A nitrate, a sulfate of an alkaline earth metal, a hydrochloride, a nitrate or the like is used, and among them, a sulfate of an alkali metal, particularly sodium sulfate or potassium sulfate is preferable.

In washing with water, the amount of water used is usually 1 to 2 with respect to 100 parts by weight of the reaction solution which has been washed with an alkaline aqueous solution or the aqueous solution of a neutral salt.
00 parts by weight, preferably 5 to 50 parts by weight.

When the dehydration esterification reaction is carried out in an organic solvent, purified (meth) acrylic acid ester can be obtained by washing with water and then distilling off the organic solvent. Distillation of the organic solvent may be carried out under any conditions of reduced pressure or normal pressure, but in order to suppress the polymerization reaction of the product, it is usually carried out under reduced pressure by adding a polymerization inhibitor. It is more preferable to carry out in an inert gas atmosphere having an oxygen content of 5 to 13% by volume.

The type of polymerization inhibitor used here is
For example, phenol-based compounds such as hydroquinone and metoquinone are mainly used, but metoquinone is particularly preferably used because there is no modified coloring. The amount of addition depends on the kind of the (meth) acrylic acid ester obtained,
Usually 5 to 5000 ppm, preferably 50 to 2500 p
pm.

[0059]

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. In addition,% in the examples is based on weight unless otherwise specified.

Example 1 A 3 l glass four-necked flask equipped with a reflux condenser, a water separator, an air inlet tube, a thermometer and a stirrer was charged with acrylic acid 6
20 g, 321 g of trimethylolpropane, 6.5 g of 2-methyl-1-phenol-4-sulfonic acid, 44 g of p-toluenesulfonic acid, 0.8 g of copper sulfate, and 1317 g of toluene as a solvent were charged.

Next, 7% oxygen concentration nitrogen gas was blown into this flask at 30 ml / min to heat it using a hot water bath. While stirring the inner solution, toluene and by-produced water began to azeotrope. For 12 hours, water was azeotropically removed by a water separator under a reduced pressure of 360 to 260 torr, and only toluene was refluxed to react at 75 ° C. The amount of reaction water separated from the reaction system in this reaction was 134 g, and 11 g of acrylic acid was contained in this.

Immediately after completion of the reaction, the reaction solution was cooled to room temperature, then 107 g (containing acrylic acid) of the reaction water dehydrated and separated during the esterification reaction was added to the reaction solution, stirred for 10 minutes, and then allowed to stand for 30 minutes. After confirming that the two layers were separated, the washing water for the lower layer was withdrawn from the bottom to separate the solution for the upper layer to obtain 99.
Obtained in a yield of 5%.

The removal rate of 2-methyl-1-phenol-4-sulfonic acid, p-toluenesulfonic acid and copper sulfate removed by this water washing was about 90%. Moreover, the amount of the wash water extracted was as small as 144 g (containing 2-methyl-1-phenol-4-sulfonic acid 5.9 g, p-toluenesulfonic acid 39 g, copper sulfate 0.7 g and acrylic acid 17 g). It was This washing water could be reused as it is for the production of acrylic acid ester.

To the obtained crude acrylic acid ester, 181 g of 20% aqueous sodium hydroxide solution was added, stirred for 10 minutes, and allowed to stand for 30 minutes to confirm that it was separated into two layers. Then, the lower layer was separated and removed. The operation was repeated once.

Then, 250 g of a 7% sodium sulfate aqueous solution was added to this, and the mixture was stirred and allowed to stand, and after confirming that the layers were separated into two layers, the lower layer was separated and removed. 7 more
250 g of water instead of 250% sodium sulfate aqueous solution
After the same stirring and standing except that the above was used, the operation of separating and removing the lower layer was repeated twice to obtain 9 parts of the crude acrylic acid ester.
Obtained in a yield of 5.0%.

At this time, the total amount of waste liquid was 1234 g. The crude acrylic acid ester thus obtained was mixed with 10
0 ppm was added, the solvent was distilled off under reduced pressure, and 653 g of trimethylolpropane triacrylate was obtained at a yield of 92%.

The obtained product was filtered under reduced pressure at 60 Torr with a filter having a pore size of 1 micron and a diameter of 47 mm, and the filtration rate was 30 g / min.

Examples 2 to 15 Example 1 except that the compounds shown in Table 1 were used in the amounts shown in Table 1 as the compound (A), the esterification catalyst (B) and the polymerization inhibitor (C). An acrylic ester was obtained in the same manner as in. Table 2 shows the results.

[0069]

[Table 1]

A1: sodium naphthalate 2-sulfonate A2: potassium 2-methyl-1-phenol-4-sulfonate A3: 2-nitroso-1-phenol-4-sulfonic acid A4: 4-amino- Sulfonic acid A5: 2-methyl-1-phenol-4-sulfonic acid B1: p-toluenesulfonic acid B2: sulfuric acid B3: benzenesulfonic acid

[0071]

[Table 2]

Example 16 As in Example 1, dehydration esterification reaction, washing with water and 20
% Aqueous sodium hydroxide solution. After this, without washing with a sodium sulfate aqueous solution,
Washing with 200 g of water was performed twice.

At this time, the total amount of waste liquid was 892 g. Next, 100 ppm of methquinone was added to the obtained crude acrylic acid ester and the solvent was distilled off under reduced pressure to obtain trimethylolpropane triacrylate in a yield of 92%.

The obtained product was filtered under reduced pressure with a filter having a pore size of 1 micron and a diameter of 47 mm at 60 torr. The filtration rate was 21 g / min.

Comparative Example 1 78 g of p-toluenesulfonic acid as an esterification catalyst
Was reacted in the same manner as in Example 1 except that 1.0 g of pyrogallol was used as the polymerization inhibitor.

After the completion of the reaction, the reaction solution was cooled to room temperature, 200 g of water was added to the obtained reaction solution, followed by washing with water, washing with 181 g of 20% aqueous sodium hydroxide solution twice, and washing with 1000 g of water three times. Carried out to obtain crude acrylic ester in a yield of 92%.

At this time, the total amount of waste liquid was 3658 g. Then, 100 ppm of methquinone was added to the obtained crude acrylic acid ester, and the solvent was distilled off under reduced pressure to obtain trimethylolpropane triacrylate in a yield of 88%.

The obtained product was filtered under reduced pressure with a filter having a pore size of 1 micron and a diameter of 47 mm at 60 torr, and the filtration rate was 19 g / min.

[0079]

According to the production method of the present invention, the amount of the esterification catalyst used can be reduced and the waste liquid can be remarkably reduced. Moreover, the high molecular weight by-product can be easily removed by washing the reaction liquid with an alkaline aqueous solution and then with an aqueous solution of a neutral salt. Furthermore, the oxygen content rate is 5
By reacting in an inert gas atmosphere of ˜13% by volume, the danger of explosion of the flammable compound in the system can be significantly reduced.

Claims (17)

[Claims] 1. A water-soluble compound (A) having both a polymerization preventing function and an esterification catalyst function, a water-soluble esterification catalyst (B) other than the compound (A), and a compound other than the compound (A). In the presence of the water-soluble polymerization inhibitor (C), the (meth) acrylic acid (D) and the alcohols (E) are subjected to dehydration esterification reaction, and then the reaction water obtained by separating from the reaction system is used. A method for producing (meth) acrylic acid esters, which comprises washing with water to remove the compound (A), the esterification catalyst (B) and the polymerization inhibitor (C), and then washing with an aqueous alkali solution. 2. The production method according to claim 1, wherein washing with an aqueous solution of a neutral salt is performed after washing with an alkaline aqueous solution. 3. The production method according to claim 1 or 2, wherein after washing with an alkaline aqueous solution or after washing with an aqueous solution of a neutral salt, washing with water is performed. 4. The compound (A) is a phenolic hydroxyl group,
Aromatic sulfonic acids having at least one functional group selected from the group consisting of an amino group, a nitro group and a nitroso group,
The production method according to claim 1, 2 or 3, wherein these are alkali metal salts or ammonium salts. 5. The compound (A) is an aromatic sulfonic acid having a lower alkyl group and a phenolic hydroxyl group, or an alkali metal salt or ammonium salt thereof,
The manufacturing method according to 2 or 3. 6. The method according to claim 4 or 5, wherein the esterification catalyst (B) is a mineral acid or an aromatic sulfonic acid. 7. The production method according to claim 4 or 5, wherein the esterification catalyst (B) is benzenesulfonic acid or p-toluenesulfonic acid. 8. The method according to claim 6 or 7, wherein the polymerization inhibitor (C) is one or more compounds selected from the group consisting of transition metals, transition metal oxides and transition metal salts. 9. The production method according to claim 6, wherein the polymerization inhibitor (C) is a chloride, sulfate or nitrate of copper, manganese or iron. 10. The production method according to claim 1, wherein the reaction is carried out in an inert gas atmosphere having an oxygen content of 5 to 13% by volume. 11. The production method according to claim 1, wherein the dehydration esterification reaction is carried out in an organic solvent. 12. The method according to claim 11, wherein the organic solvent is an aromatic hydrocarbon. 13. The method according to claim 1, wherein the aqueous solution of the neutral salt is an aqueous solution of an alkali metal sulfate. 14. The addition amount of the esterification catalyst (B) is
The amount is 0.5 to 6 parts by weight based on 100 parts by weight of the total of (meth) acrylic acid (D) and alcohols (E).
The manufacturing method according to any one of 1 to 13. 15. The amount of the compound (A) added is 0.1 to 2 parts by weight based on 100 parts by weight of the total of the (meth) acrylic acid (D) and the alcohols (E). Production method. 16. The amount of the polymerization inhibitor (C) added is such that the concentration of the polymerization inhibitor (C) in the reaction system is 100 to 1000 ppm.
16. The method according to claim 15, wherein the amount is 17. The production method according to claim 1, wherein the alcohol (E) is a polyhydric alcohol.