JPH0680033B2 - Method for producing acrylic acid ester or methacrylic acid ester - Google Patents

Description

The present invention relates to a method for producing an ester of acrylic acid or methacrylic acid and a higher alcohol, and in particular, to recover acrylic acid or methacrylic acid used in excess efficiently and to obtain a higher alcohol. The present invention relates to a method for producing an ester in high yield and high purity.

[Conventional technology]

Esters of acrylic acid or methacrylic acid (hereinafter referred to as (meth) acrylic acid) and higher alcohols are widely used as raw material monomers for acrylic resins, paints, adhesives, pressure-sensitive adhesives and the like.

(Meth) acrylic acid higher alcohol ester is generally produced by directly esterifying (meth) acrylic acid and a higher alcohol. In this direct esterification, if a higher alcohol is used in excess, it is difficult to separate and purify the produced ester. Therefore, a method in which (meth) acrylic acid is used in excess is widely used.

However, the method of using excess (meth) acrylic acid is
There is a problem that excess (meth) acrylic acid is removed to the outside of the system by the neutralization water washing in the purification step after the reaction, and at the same time, a part of the produced ester is also lost.

In order to improve these problems, the use of an organic inert solvent and the recovery and utilization of (meth) acrylic acid have been studied (for example, JP-A-58-192851). However, no satisfactory method has been found yet.

[Problems to be solved by the invention]

When (meth) acrylic acid and a higher alcohol are directly esterified to obtain a higher alcohol ester of (meth) acrylic acid, excess (meth) acrylic acid used is efficiently recovered, and at the same time, the desired ester can be obtained in a high yield. It is intended to obtain high purity.

[Means for solving problems]

The present inventors have conducted intensive studies on a method for obtaining a higher alcohol ester of (meth) acrylic acid with almost no loss of excess (meth) acrylic acid, and as a result, have found an epoch-making production method. I was happy to complete.

That is, according to the present invention, after esterifying a higher alcohol and an excess of (meth) acrylic acid in the presence of an esterification catalyst and a polymerization inhibitor, a lower alcohol is added to esterify the remaining (meth) acrylic acid. The method for producing an acrylic acid ester or a methacrylic acid ester is characterized in that the obtained (meth) acrylic acid ester is fractionally distilled.

The higher alcohol used in the present invention, octyl alcohol, nonyl alcohol, decyl alcohol, undecyl alcohol, dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, hexadecyl alcohol, heptadecyl alcohol, octadecyl alcohol, nona Saturated and unsaturated alcohols having 8 to 22 carbon atoms such as decyl alcohol, eicosyl alcohol, docosyl alcohol, dodecenyl alcohol, pentadecenyl alcohol and octadecenyl alcohol, or straight and side chains Examples thereof include alcohols and adducts of these alcohols with ethylene oxide or propylene oxide. These alcohols can be used alone or as a mixture of two or more kinds.

Examples of the polymerization inhibitor used in the present invention include hydroquinone, hydroquinone monomethyl ether, phenothiazine, and t-butylcresol.

As the esterification catalyst, sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid, benzenesulfonic acid, xylenesulfonic acid, etc. can be used.

As the lower alcohol used in the present invention, methanol, ethanol, propanol, isopropanol,
Examples include isobutanol and butanol, with methanol being particularly preferred.

In the production method of the present invention, higher alcohol and excess (meth)
Acrylic acid is subjected to an esterification reaction (first-stage esterification) while dehydrating in the presence of an esterification catalyst and a polymerization inhibitor, and the reaction is continued until condensed water does not come out from the reaction system to produce a higher alcohol. Esterify. After completion of the esterification reaction in the first step, a lower alcohol is added to continue the esterification reaction (esterification in the second step). After completion of the reaction, the (meth) acrylic acid lower alcohol ester in the reaction system is distilled off under reduced pressure to remove the reaction catalyst to obtain the desired (meth) acrylic acid higher alcohol ester.

The esterification reaction in the present invention is difficult to proceed at a temperature lower than 60 ° C and easily polymerizes at a temperature higher than 150 ° C. Therefore, it is preferably carried out at 60 to 150 ° C, under reduced pressure, under normal pressure or under pressure. Good. In particular, in the esterification reaction in the second step, it is preferable to carry out the reaction under pressure in order to suppress the distillation of the lower alcohol to proceed the reaction.

The amount of (meth) acrylic acid used in the present invention is excessive with respect to the higher alcohol, and is usually 1.1 to 2.0 times mol, preferably 1.1 to 1.2 times mol.

The amount of esterification catalyst used is 0 for higher alcohols.
It is 5 to 4 mol%, preferably 1 to 2 mol%. Also,
The amount of the polymerization inhibitor used is 50 to 1000 ppm, preferably 100 to 500 ppm in the reaction system.

The amount of lower alcohol used in the esterification reaction in the second step was 1.1 with respect to the residual (meth) acrylic acid.
˜1.0 times mol, preferably 2 to 6 times mol.
This esterification reaction proceeds sufficiently without adding an esterification catalyst and a polymerization inhibitor, and the reaction is 60 to 100.
The remaining (meth) acrylic acid becomes an ester of a lower alcohol almost quantitatively at a temperature of ℃, preferably 80 to 100 ℃ for about 3 hours.

Distillation of the produced (meth) acrylic acid lower alcohol ester can be carried out by ordinary vacuum distillation, thin film distillation, or the like.

The esterification catalyst is preferably removed by neutralization with an alkaline aqueous solution. As the alkali used at this time, those generally known as alkaline substances such as sodium hydroxide, potassium hydroxide and sodium carbonate can be used. The concentration of the alkaline aqueous solution is preferably 0.1 to 30% in consideration of generation of by-products.

〔The invention's effect〕

By the method of the present invention, not only the (meth) acrylic acid used in excess can be utilized almost completely, but also the higher alcohol ester of (meth) acrylic acid can be obtained in high yield and high purity.

The obtained (meth) acrylic acid higher alcohol ester and (meth) acrylic acid lower alcohol ester should be used as raw material monomers for acrylic resins, paints, adhesives, etc. in a wide range of fields, equivalent to or more than conventional products. You can

〔Example〕

 The present invention will be described with reference to Examples and Comparative Examples.

Example 1 50 equipped with a thermometer, air blowing tube, water separator and stirrer
Methacrylic acid 103.3 g (1.2 mol) in a 0 ml four-necked flask,
Take 270.0 g (1.0 mol) of octadecyl alcohol, 3.5 g (2 mol% of alcohol) of p-toluenesulfonic acid and 0.11 g (300 ppm) of hydroquinone, and raise the temperature to 110-115 ° C while passing a small amount of air. The reaction was carried out for 45 hours while removing the produced water outside the reaction system under a reduced pressure of ~ 600 mmHg. The reaction rate of alcohol was 99.2%, and the amount of methacrylic acid remaining in the reaction system was 13.6 g.

Then, after cooling the reaction system to 50 ° C, 30.3 g of methanol was added.
(6 times mol of residual methacrylic acid) was added, the temperature was raised to 80 ° C., and the reaction was carried out for 3 hours. As a result of gas chromatography analysis, 99.1% of the remaining methacrylic acid was methyl esterified.

Then, under reduced pressure of 160 mmHg, 15.0 g of methyl methacrylate and excess methanol were combined and 39.0 g was distilled off at 46 ° C. Recovery rate of residual methacrylic acid as methyl methacrylate
It was 95.2%.

Next, the catalyst in the reaction solution was neutralized with an aqueous solution of sodium hydroxide and then separated into layers, and the oil layer was dehydrated to obtain 324.6 g of octadecyl methacrylate. The recovery rate for octadecyl alcohol was 96.0%.

Comparative Example 1 After the esterification reaction of methacrylic acid and octadecyl alcohol was carried out in the same manner as in Example 1, 110-115 under reduced pressure of 100 mmHg without esterification with methanol.
Excess methacrylic acid was recovered at 1 ° C. for 1 hour to obtain 8.1 g of methacrylic acid. The recovery rate of residual methacrylic acid was 59.6%.

The reaction solution was neutralized with an aqueous sodium hydroxide solution and then separated into layers, and the oil layer was dehydrated to obtain 323.6 g of octadecyl methacrylate.
The recovery rate for octadecyl alcohol was 95.7%.

Example 2 Methacrylic acid 94.7 g (1.1 mol), dodecyl alcohol 18
A reaction was carried out in the same manner as in Example 1 for 4 hours using 6.3 g (1.0 mol), p-toluenesulfonic acid 3.5 g (2 mol% based on alcohol) and hydroquinone monomethyl ether 0.14 g (500 ppm). The reaction rate of alcohol was 99.0%, and the amount of methacrylic acid present in the reaction system was 7.2 g.

Then, in the same manner as in Example 1, 10.7 g of methanol (4 times mol of residual methacrylic acid) was used for the reaction. 99.2% of the remaining methacrylic acid was methyl esterified.

Then, methyl methacrylate 8.
15.4 g of distillate containing 0 g was obtained. The recovery rate of residual methacrylic acid was 95.4% as methyl methacrylate.

Then, in the same manner as in Example 1, the catalyst was neutralized, separated into layers, and dehydrated to obtain 243.4 g of dodecyl methacrylate. The recovery rate for dodecyl alcohol was 95.8%.

Comparative Example 2 After the esterification reaction of methacrylic acid and dodecyl alcohol was carried out in the same manner as in Example 2, the catalyst in the reaction solution was neutralized with an aqueous sodium hydroxide solution without esterification with methanol. After separation, the oil layer was dehydrated to obtain 243.0 g of dodecyl methacrylate (recovery rate for dodecyl alcohol: 95.6%). Excess methacrylic acid was removed as a lower layer aqueous solution during the layer separation and was not recovered.

Example 3 Acrylic acid 86.5 g (1.2 mol), octyl alcohol 130.
2 g (1.0 mol), p-toluenesulfonic acid 1.7 g (1 mol% with respect to alcohol) and hydroquinone 0.1 g (450 p
pm) and reacted in the same manner as in Example 2. The reaction rate of alcohol was 99.0%, and the amount of acrylic acid present in the reaction system was 11.5 g.

Then, the same reaction as in Example 1 was carried out using 30.6 g of methanol (6 times the molar amount of residual acrylic acid). 99.0% of the remaining acrylic acid was methyl esterified.

Thereafter, in the same manner as in Example 1, methyl acrylate 13.0
36.6 g of distillate containing g was obtained. The recovery rate of residual acrylic acid was 95.0% as methyl acrylate.

Then, the catalyst was neutralized, separated into layers, and dehydrated in the same manner as in Example 1 to obtain 176.2 g of octyl acrylate. The recovery rate for octyl alcohol was 95.6%.

The balance and recovery of (meth) acrylic acid in the above Examples and Comparative Examples are summarized in Table 1.

As is clear from Table 1, the method of the present invention can efficiently recover excess (meth) acrylic acid.

Claims (3)

[Claims] 1. A higher alcohol is esterified with excess acrylic acid or methacrylic acid in the presence of an esterification catalyst and a polymerization inhibitor, and then a lower alcohol is added to esterify the remaining acrylic acid or methacrylic acid.
A method for producing an acrylic acid ester or a methacrylic acid ester, characterized in that the obtained acrylic acid ester or a methacrylic acid ester is fractionally distilled. 2. The method for producing an acrylic acid ester or a methacrylic acid ester according to claim 1, wherein the higher alcohol is an alcohol having 8 to 22 carbon atoms. 3. The method for producing an acrylic acid ester or a methacrylic acid ester according to claim 1, wherein the lower alcohol is methanol.