JPH08217726A - Production of pentaerythritol (meth)acrylic ester - Google Patents

Abstract

PURPOSE: To obtain in high yield the subject high-purity compound having such triacrylic ester/pentacrylic ester ratio as to be kept in a liquid state at room temperature. CONSTITUTION: In conducting an esterification between pentaerythritol and (meth)acrylic acid in the presence of a catalyst, polymerization inhibitor and organic solvent, 1st step: the reaction is carried out for 10min to 3h in such a state as to keep the water produced in the reaction system while retaining reaction temperature within 80-90 deg.C from a point when the reaction temperature falls within this range; 2nd step: the reaction temperature is set at a level lower than that in the 1st step and the water produced is removed from the reaction system to complete the reaction; thus affording the objective pentaerythritol (meth)acrylic ester.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a process for producing pentaerythritol (meth) acrylic ester by reacting pentaerythritol with (meth) acrylic acid.

[0002]

2. Description of the Related Art Pentaerythritol (meth) acrylic ester is used alone or in combination with other polymerizable monomers, oligomers, polymers, dyes, pigments, inorganic fillers, etc. to form peroxides, persulfates, azobis compounds or ketones. In the presence of radical initiators such as compounds, they are easily polymerized by radicals generated by thermal decomposition of these initiators or decomposition by irradiation of ultraviolet rays or radiation, and have excellent mechanical properties, heat resistance, weather resistance, oxidation resistance, etc. Produce a polymer.

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, such as paints, inks, coating agents, adhesives, It is used in a wide range of fields as a raw material for adhesives, resins, rubbers, optical materials and the like.

Pentaerythritol (meth) acrylic ester is obtained by esterification of pentaerythritol and (meth) acrylic acid or transesterification reaction of pentaerythritol and (meth) acrylic acid ester. The products obtained are usually pentaerythritol tetra (meth) acrylic ester, pentaerythritol tri (meth) acrylic ester, pentaerythritol di (meth) acrylic ester, pentaerythritol mono (meth) acrylic ester and pentaerythritol poly (meth) acrylic ester. It contains oligomers such as acrylic ester. Among these compounds, especially tetra (meta)
When a large amount of acrylic ester or oligomers is produced, the product becomes solid at room temperature, which is inconvenient to handle. In addition, the increase in the number of oligomers reduces the ratio of double bonds to the molecular weight, resulting in a decrease in reactivity as an acrylic ester.

However, in the reaction between pentaerythritol and (meth) acrylic acid, since pentaerythritol is insoluble in a general organic solvent, the produced (meth) acrylic ester of pentaerythritol is dissolved in the solvent. Since the tetra (meth) acrylic ester is preferentially produced, the product tends to be in a solid state at room temperature.

In order to solve this problem, Japanese Patent Laid-Open No. 1-1
Japanese Patent Publication No. 99936 discloses a method for producing pentaerythritol (meth) acrylic ester which can suppress the formation of tetra (meth) acrylic ester and maintain a liquid state at room temperature. According to this production method, the esterification product water is allowed to exist in the reaction system in the first-step reaction, and the esterification rate becomes 2
The amount of tetra (meth) acrylic ester produced can be suppressed by adjusting the amount of tetra (meth) acrylic ester to 0 to 70% and then removing the produced water from the reaction system in the second stage reaction to stop the reaction at an esterification rate of 75 to 95%. It has been shown to be possible.

[0007]

However, when the reaction is carried out in accordance with the above-mentioned patent, the amount of oligomers produced increases and the amount of tetra (meth) acrylic ester produced is small, but high purity and high yield are obtained. It was impossible to get the object.

The problem to be solved by the present invention is to suppress the amount of tetra (meth) acrylic ester produced, keep the reaction product in a liquid state at room temperature, and to obtain pentaerythritol (meth) with high purity and high yield. ) To provide a method for producing an acrylic ester.

[0009]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve the above-mentioned problems associated with the conventional method for producing pentaerythritol (meth) acrylic ester, and as a result, have found that pentaerythritol and (meth) acrylic acid In the esterification reaction, the reaction is carried out in a state where the generated water is retained in the reaction system in the first step, and then the reaction temperature is changed to the first in the second step.
By setting the temperature lower than the stage and removing the produced water from the reaction system to complete the reaction, the production amount of tetraacrylic ester is suppressed and the liquid state is maintained at room temperature, and high purity and high yield are achieved. It was found that it is possible to obtain pentaerythritol (meth) acrylic ester, and the present invention has been completed.

That is, according to the present invention, in order to solve the above-mentioned problems, pentaerythritol and (meth) acrylic acid are added.
In the method for producing a pentaerythritol (meth) acrylic ester which is esterified in the presence of a catalyst, a polymerization inhibitor and an organic solvent, (1) while maintaining this temperature range from the time of reaching the temperature of 80 to 90 ° C, The first step of reacting for 10 minutes to 3 hours while keeping water in the reaction system,
(2) A method for producing pentaerythritol (meth) acrylic ester, which comprises a second step in which the reaction temperature is set lower than the reaction temperature in the first step to remove produced water from the reaction system. provide.

The feature of the production method of the present invention is that the reaction is carried out with the produced water being kept in the reaction system in the first step to promote the dissolution of pentaerythritol as a raw material,
In the following second step, the reaction temperature is set to a temperature lower than that in the first step, and the produced water is removed from the reaction system to complete the reaction, whereby the production amount of tetraacrylic ester is suppressed and the liquid state is maintained at room temperature. In addition, it is possible to obtain pentaerythritol (meth) acrylic ester with high purity and high yield.

The esterification catalyst used in the present invention is
Any compound having a catalytic function for the esterification reaction may be used, and examples thereof include inorganic acids such as sulfuric acid and phosphoric acid; aromatic sulfonic acids such as benzenesulfonic acid and p-toluenesulfonic acid; methanesulfonic acid and trifluoromethanesulfonic acid. Aliphatic sulfonic acids such as; acid ion exchange resins and the like. However, it is preferable to use a water-soluble compound having both a polymerization preventing function and a catalytic function in combination with a water-soluble catalytic compound other than the compound in order to reduce the amount of the catalyst and the polymerization. It is preferable in that the amount of the inhibitor can be reduced, the side reaction can be suppressed, and the catalyst can be easily removed.

Examples of the water-soluble compound (A) having both an esterification catalyst function and a polymerization preventing function used in the present invention include acids having functional groups such as phenolic hydroxyl group, amino group, nitro group and nitroso group. The salt etc. are mentioned. 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.

Examples of the aromatic sulfonic acids include phenol-2-sulfonic acid, phenol-3-sulfonic acid, phenol-4-sulfonic acid and 2-methyl-sulfonic acid.
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-sulfone 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-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-naphthol-8-sulfonic acid and other phenolic hydroxyl group-containing aromatic sulfonic acid compounds, 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 Examples thereof include amino group-containing aromatic sulfonic acid compounds such as sulfonic acids, nitrosoaniline sulfonic acids, and aminonaphthol sulfonic acids, and these may be used alone or in combination.

Among these, aromatic sulfonic acids having a lower alkyl group and a phenolic hydroxyl group (in terms of high catalytic function and high polymerization inhibiting function, good balance between them, and excellent solubility in water ( Here, 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-t
ert-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,
Aromatic sulfonic acids such as 2,5-dimethyl-1-phenol-6-sulfonic acid may be mentioned.

The amount of the water-soluble compound (A) having both the catalytic function and the polymerization preventing function in the present invention is (meth)
The range of 0.005 to 10 parts by weight is preferable, and the range of 0.1 to 2 parts by weight is particularly preferable, based on 100 parts by weight of the total weight of acrylic acid and pentaerythritol.

As the water-soluble esterification catalyst (B) other than the water-soluble compound having both the esterification catalyst function and the polymerization prevention function used in the present invention, for example, the above-mentioned catalyst function and polymerization prevention function are combined. Acidic compounds other than water-soluble compounds, especially mineral acids, halogenated carboxylic acids,
Water-soluble strongly acidic compounds such as sulfonic acids, especially mineral acids and aromatic sulfonic acids are preferable.

Examples of the above-mentioned mineral acids include sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, fuming sulfuric acid, phosphoric acid and hydrochloric acid, and examples of aromatic sulfonic acids include benzenesulfonic acid, o-toluenesulfonic acid and m-toluene. Examples thereof include sulfonic acid, p-toluenesulfonic acid, and xylenesulfonic acids, and these may be used alone or in combination.

Among these catalyst compounds, a methyl group may be present at the p-position such as benzenesulfonic acid and p-toluenesulfonic acid because of their excellent esterification catalytic function and water solubility. Benzenesulfonic acid is particularly preferred.

The amount of the water-soluble catalyst compound (B) other than the water-soluble compound having both the catalytic function and the polymerization preventing function used in the present invention is 100 parts by weight in total of (meth) acrylic acid and pentaerythritol. For 0.1 to 10
A range of parts by weight is preferable, and a range of 0.5 to 6 parts by weight is particularly preferable.

Examples of the water-soluble polymerization inhibitor other than the water-soluble compound (A) having both the esterification catalyst function and the polymerization prevention function used in the present invention include transition metal powders and transition metal oxides. Examples thereof include transition metal chlorides, sulfates, nitrates, acetates, salts of transition metals such as oxalates, etc. Usually, a readily water-soluble transition metal chloride, sulfate or nitrate is used. The types of transition metals include
Any transition metal having a polymerization preventing function may be used, for example,
Copper, manganese, iron, cerium and the like, but usually,
Copper, manganese or iron is 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, ferrous nitrate and the like.

The addition amount of the polymerization inhibitor in the present invention is usually such that the concentration of the polymerization inhibitor in the reaction system is 50 to 2000 ppm.
Is preferable, and an amount in the range of 100 to 1000 ppm is particularly preferable.

Examples of the (meth) acrylic acid used in the present invention include acrylic acid and methacrylic acid.

The amount of (meth) acrylic acid used in the present invention is not particularly limited, but it is preferably in the range of 1.0 to 5.0 mol with respect to 1 mol of pentaerythritol.
The range of 3.0 to 4.0 mol is particularly preferable. When the amount of (meth) acrylic acid used is less than 1.0 mol with respect to 1 mol of pentaerythritol, the progress of the reaction tends to be slow and the yield tends to be low. )
When the amount of acrylic acid used is more than 5.0 mol per 1 mol of pentaerythritol, the production amount of tetraacrylic ester and oligomers tends to increase rapidly, which is not preferable.

The dehydration esterification reaction in the present invention can be carried out in an organic solvent or without solvent, but it is usually carried out in an organic solvent because it is easy to control the reaction and remove reaction water. As the organic solvent used here, for example,
Benzene, toluene, xylene, hexane, cyclohexane, heptane, octane, nonane, methylcyclohexane, etc., which can be phase-separated from water when mixed with water and can be azeotroped with water and have a boiling point of 60 to 140 ° C. Those in the range are usually used, and among these, aromatic hydrocarbons, particularly toluene, are preferable because they are excellent in solubility of the (meth) acrylic ester and the catalyst compound. 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. Addition amount is (meta)
Generally, a range of 0 to 300 parts by weight is preferable for 100 parts by weight of acrylic acid and pentaerythritol in total,
A range of 20 to 150 parts by weight is particularly preferred.

In the first step of the present invention, heating is started to
When the temperature in the reaction system reaches a certain temperature, the reaction is carried out for 10 minutes to 3 hours while maintaining the temperature range while keeping the water (produced water) produced by the esterification reaction in the reaction system. By allowing the reaction to proceed while keeping the produced water in the reaction system, pentaerythritol as a raw material is dissolved in the produced water, and as a result, the reaction of pentaerythritol can be promoted.

The reaction temperature in the first step of the present invention is a temperature at which the solvent and the produced water are not azeotropic, and in order to obtain an appropriate reaction rate, the range of 60 to 100 ° C. is preferable,
The range of 80 to 95 ° C is particularly preferable. The reaction can be carried out under reduced pressure as long as it is within the above temperature range and the solvent and produced water are not azeotropic.

The reaction time in the first step of the present invention is preferably 10 minutes to 3 hours, particularly preferably 20 minutes to 1 hour. When the reaction time is shorter than 10 minutes, the amount of water produced is small, so it takes time to dissolve pentaerythritol, and as a result, the amount of tetraacrylic ester produced tends to increase, which is not preferable. Further, if the reaction time is longer than this, the reaction is close to the equilibrium state, the progress is slowed down, and the production amount of the oligomer is increased, which tends to lower the purity of the target product, which is not preferable.

The reaction temperature in the second step of the present invention is lower than that in the first step. In the second stage reaction,
The degree of reduced pressure is adjusted so that the solvent and the produced water can be azeotropically distilled, the production of the tetraacrylic ester can be further suppressed, and the following appropriate reaction temperature can be obtained. The reaction temperature in the second stage is preferably 50 to 90 ° C, particularly preferably 60 to 75 ° C. The reaction of the second stage can be carried out under normal pressure, but in that case, it is necessary to select a solvent having a boiling point capable of azeotroping the produced water within the above optimum temperature range.

The reaction time in the second step of the present invention is 2 to 1
The range of 2 hours is preferable, and the range of 4 to 8 hours is particularly preferable. If the reaction time in the second step is shorter than 2 hours, it is difficult to complete the reaction, which is not preferable.
In this case, a large amount of diacrylic ester and monoacrylic ester, which are soluble in water and easily disappear during the washing and purification after the reaction, are produced, resulting in a decrease in yield. If the reaction time in the second step is longer than 12 hours, the amount of tetraacrylic ester and oligomers produced tends to increase, which is not preferable.

As mentioned above, by carrying out the reaction temperature in the second stage at a lower temperature than in the first stage,
This makes it possible to obtain a high-purity target product, and when the reaction temperature in the second step is the same as or higher than that in the first step, the yield and the purity decrease sharply. Become.

In the reaction of the present invention, oxygen or a mixture of oxygen and an inert gas, for example, for preventing the polymerization of (meth) acrylic acid or the produced (meth) acrylic acid ester, for example,
When air or oxygen / argon mixed gas is introduced into the reaction liquid and / or on the surface of the reaction liquid over the entire reaction time, the polymerization preventing effect is further improved. In this case, the mixing ratio of 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 inhibiting effect, but from the economical point of view, it is 0.1 to 10 per 1 mol of (meth) acrylic acid charged.
A range of ml / min is preferred.

At this time, oxygen or a mixture of oxygen and an inert gas is blown into the reaction solution so as to form fine bubbles, so that the efficiency of the polymerization preventing effect is enhanced and the reaction is produced by the esterification reaction. Water is preferable in that it can be quickly removed, and blowing into the gas phase near the contact interface is preferable in that it prevents polymerization in the contact region between the surface of the reaction vessel, the reaction solution, and the gas phase. In any case, blowing oxygen or a mixture of oxygen and an inert gas into the system can prevent the polymerization of the acrylic double bond portion during the esterification reaction, whether in the liquid or in the gas phase, and the esterification Since it works to accelerate the reaction, it is preferable to carry out the esterification reaction together.

After completion of the reaction, a purification step is carried out by a known method such as washing with water and distillation. Usually, the reaction product is washed with water to remove the catalyst, the polymerization inhibitor and the like, and then unreacted (meth) acrylic acid is removed by washing with an alkaline aqueous solution, followed by washing with water. Further, if necessary, the solvent can be removed to obtain the intended pentaerythritol acrylic ester.

The method for washing the reaction product is not particularly limited, and any commonly used method such as stirring and extraction may be used, and the amount of water used for washing, the number of times of washing and the like are also required. It can be changed accordingly. still,
As the water used for washing, the produced water obtained by separating from the reaction system is sufficient.

In the present invention, the washing water obtained by washing with generated water contains a water-soluble polymerization inhibitor and / or catalyst and unreacted (meth) acrylic acid, so that the aqueous solution as it is, It is also possible to reuse in the reaction in the state of concentrating to form a concentrated aqueous solution or in the state of being evaporated to dryness.

In the method for producing pentaerythritol (meth) acrylic ester of the present invention, after the washing with the reaction water is completed, the unreacted (meth) acrylic acid remaining can be removed by washing with an alkaline aqueous solution. is there. After washing with an alkaline aqueous solution, washing with an aqueous solution of a neutral salt and / or washing with water,
Good quality such as product hue can be obtained. In particular, a method in which unreacted (meth) acrylic acid is removed by washing with an aqueous alkaline solution, high molecular weight byproducts and the like are removed by washing with an aqueous solution of a neutral salt and, if necessary, water washing is used in combination It is preferable in that it improves the filtration characteristics of the product.

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 purification method in which the (meth) acrylic acid and the solvent remaining in the reaction solution are recovered by a method such as extraction or distillation and then combined with the above-mentioned washing method is also effective.

The concentration of the alkaline aqueous solution used for washing with the alkaline aqueous solution may be any concentration as long as the alkaline salt is dissolved, 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 the neutralization equivalent of the reaction solution that has been washed with the reaction water.
An aqueous solution containing 2.0 times the amount of alkali is preferable.
The amount of the aqueous solution containing 0 to 1.2 times the amount of alkali is more preferable. At this time, the alkaline aqueous solution may be added all at once or may be added in portions.

The alkalis usable in the alkaline aqueous solution used for washing are not particularly limited as long as they are water-soluble alkalis, and examples thereof include hydroxides, carbonates, phosphates or alkali metals of alkali metals. Examples include hydroxides, carbonates, phosphates, etc. of earth metals, and among them,
Sodium hydroxide, potassium hydroxide, sodium carbonate,
Potassium carbonate is preferable, and sodium hydroxide and potassium hydroxide are particularly 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 in the range of 0.5 to 25% by weight is preferable. The amount of the neutral salt aqueous solution used is 1 with respect to 100 parts by weight of the reaction solution that has been washed with the alkaline aqueous solution.
The range is preferably from 200 to 200 parts by weight, particularly preferably from 5 to 50 parts by weight.

The neutral salt that can be used in washing with an aqueous solution of 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. Examples thereof include nitrates, alkaline earth metal sulfates, hydrochlorides, nitrates, and the like. Among these, alkali metal sulfates are preferable, and sodium sulfate and potassium sulfate are particularly preferable.

The amount of water used in washing with water is 1 to 100 parts by weight of the reaction solution which has been washed with the alkaline aqueous solution or the aqueous solution of the neutral salt.
A range of 200 parts by weight is preferable, and a range of 5 to 50 parts by weight is particularly preferable.

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 either 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. At this time, a method of carrying out in an inert gas atmosphere having an oxygen content of 5 to 13% by volume is more preferable.

The type of polymerization inhibitor used here is
For example, a phenolic compound such as hydroquinone and methoquinone is mainly used, but metoquinone is particularly preferably used in that it does not have modified coloring. The amount added is
Although it depends on the kind of the obtained (meth) acrylic acid ester, usually, the range of 5 to 5000 ppm is preferable,
A range of up to 2500 ppm is particularly preferred.

[0046]

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 these examples. In addition, the yields in the examples are shown as percentages of the ratio of the amount of pentaerythritol consumed for the production of tetraacrylic ester and triacrylic ester to the amount of pentaerythritol used.

(Example 1) 1,296 g (18.0 g) of acrylic acid was placed in a three-liter glass four-necked flask equipped with a reflux condenser, a water separator, an air inlet tube, a thermometer and a stirrer.
Mol), 680 g (5.0 mol) of pentaerythritol, 39.5 g (0.21 mol) of 3-hydroxy-4-methyl-benzenesulfonic acid, 79.0 g (0.46 g) of p-toluenesulfonic acid, copper sulfate. 0.98 g and 790.4 g of toluene as a solvent were charged. Next, 3% of nitrogen gas with 7% oxygen concentration was added to the flask.
Heating in the flask was started while blowing at 0 ml / min, and the inner solution was stirred. The contents reached 90 ° C. in 1 hour. After heating and stirring at this temperature for 0.5 hour, the system was cooled to 60
Reduce the pressure to 0 mmHg, and raise the reaction temperature to 0.5 over 65 hours.
The temperature was lowered to ° C and the reaction was carried out for 4 hours. During this period, the pressure reduction degree was gradually increased to remove the generated water, and finally 200 mmHg
And

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 lower layer washing water was drawn from the bottom to separate the upper layer solution to obtain a crude acrylic ester.

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

Next, 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
% Water instead of 250% sodium sulfate aqueous solution 250 g
After the same stirring and standing except that was used, the lower layer was separated and removed. This operation was repeated once again to obtain a mixture of pentaerythritol acrylic ester in a yield of 86%.
The content (purity) of triacrylic ester and tetraacrylic ester in this mixture was 89%, and the production ratio of triacrylic ester and tetraacrylic ester was 1.51 as a weight ratio by gas chromatographic analysis.

(Examples 2 to 4) Experiments were conducted in the same manner as in Example 1 except that the reaction temperatures and reaction times of the first and second steps were the temperatures and times shown in Table 1. The results are shown in Table 1.

(Comparative Examples 1 and 2) Experiments were carried out in the same manner as in Example 1 except that the reaction temperatures and reaction times of the first and second steps were the temperatures and times shown in Table 1. The results are shown in Table 1.

[0053]

[Table 1]

In the above table, "tri / tetra ratio" means the production ratio of triacrylic ester and tetraacrylic ester.

(Example 5) A mixture of pentaerythritol acrylic ester was obtained in the same manner as in Example 1 except that 0.93 g of manganese sulfate was used instead of copper sulfate in a yield of 84%. It was The content (purity) of triacrylic ester and tetraacrylic ester in this mixture was 88%, and the production ratio of triacrylic ester and tetraacrylic ester was 1.51 as a weight ratio by gas chromatographic analysis.

(Example 6) A mixture of pentaerythritol acrylic ester was obtained in the same manner as in Example 1 except that 1.12 g of iron acetate was used in place of copper sulfate in a yield of 88%. It was The content (purity) of triacrylic ester and tetraacrylic ester in this mixture is
The production ratio of triacrylic ester and tetraacrylic ester at 86% was 1.44 as a weight ratio by gas chromatographic analysis.

[0057]

According to the production method of the present invention, after the reaction is carried out for 10 minutes to 3 hours with the produced water being kept in the reaction system,
In the following second step, the reaction temperature is set to a temperature lower than that in the first step, and the produced water is removed from the reaction system to complete the reaction, whereby a triacrylic ester capable of maintaining a liquid state at room temperature. It is possible to obtain pentaerythritol (meth) acrylic ester in a high yield and high purity at a ratio of / pentaacrylic ester.

Claims (7)

[Claims] 1. A method for producing pentaerythritol (meth) acrylic ester, which comprises esterifying pentaerythritol and (meth) acrylic acid in the presence of a catalyst, a polymerization inhibitor and an organic solvent, wherein (1) 80 to 90 ° C. From the time when the temperature reaches the temperature of 1), the generated water is kept in the reaction system for 10 minutes to 3 hours while maintaining this temperature range.
Step 2, (2) a pentaerythritol (meth) acrylic ester comprising a second step in which the reaction temperature is set lower than the reaction temperature in the first step to remove produced water from the reaction system. Method. 2. In the reaction time of the first stage, 80-9
The method according to claim 1, wherein the reaction is carried out for 20 minutes to 1 hour while maintaining the temperature range of 5 ° C. from the time when the temperature range of 5 ° C. is reached. 3. The production method according to claim 1, wherein the reaction temperature in the second step is 60 to 75 ° C. 4. The molar ratio of (meth) acrylic acid to pentaerythritol is 3.0: 1.0 to 4.0:
The manufacturing method according to claim 1, 2 or 3, which is in the range of 1.0. 5. A water-soluble compound (A) having both a polymerization preventing function and an esterification catalyst function as a catalyst and a polymerization inhibitor, a water-soluble esterification catalyst (B) other than the compound (A), and the compound ( The production method according to claim 1, 2, 3 or 4, wherein a water-soluble polymerization inhibitor other than A) is used. 6. The compound (A) is an aromatic sulfonic acid derivative having a lower alkyl group and a phenolic hydroxyl group, and the compound (B) is a benzenesulfonic acid which may have a methyl group at the p-position. The compound (C) is selected from the group consisting of copper, manganese or iron chlorides, sulfates or nitrates, and the method according to claim 1, 2, 3, 4, 5 or 6. 7. The production method according to claim 1, wherein the organic solvent is an aromatic hydrocarbon.