JP2004051546A - Method for producing (meth)acrylic ester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing the (meth)acrylic ester in high yield and purity with slight discoloration without forming impurities insoluble to an aromatic hydrocarbon such as toluene or xylene, an ester such as ethyl acetate or methyl methacrylate or an alcohol such as methanol as solvent and/or reactive diluent. <P>SOLUTION: The method for producing the (meth)acrylic ester comprises carrying out a reaction between an alcohol and (meth)acrylic acid in a reaction solvent in the presence of an acid catalyst, and after the esterification reaction, neutralizing and then washing with water the resultant reaction liquid, adding a basic lithium salt at 0.01-5 wt.% based on the (meth)acrylic ester formed, distilling off the reaction solvent while introducing molecular oxygen into the system, and then filtering off insolubles. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a high yield, a high purity, a low coloration, and an acrylate or an acrylic ester which, when dissolved in a solvent such as an aromatic hydrocarbon and / or a reactive diluent, does not generate impurities insoluble therein. The present invention relates to a method for producing methacrylic acid esters (hereinafter abbreviated as (meth) acrylic acid esters).
[0002]
[Prior art]
As a method for producing a (meth) acrylic acid ester, a method of reacting (meth) acrylic acid and an alcohol while blowing molecular oxygen in the presence of an organic solvent, a polymerization inhibitor, and an acid catalyst has been used for a long time. . After completion of the reaction, the unreacted (meth) acrylic acid and the acid catalyst are removed by alkali neutralization, and the organic solvent is distilled off under reduced pressure. ) Acrylic esters are manufactured. However, this method has a problem that the (meth) acrylic acid ester obtained after the esterification reaction is colored with respect to the hue of the raw material (meth) acrylic acid or alcohol. For this reason, various means for producing a (meth) acrylic acid ester with less coloring have been proposed.
[0003]
For example, first, a method of purifying by vacuum distillation represented by JP-A-51-54515, and a method of adsorbing and removing a coloring substance with activated carbon, activated clay and the like are reported in JP-A-59-219252. Have been. Further, in JP-A-11-263779, the present inventors have reported a method of adding a weakly basic salt containing potassium or sodium at the time of removing the organic solvent after completion of the reaction.
[0004]
[Problems to be solved by the invention]
Of these production methods, in the method represented by JP-A-51-54515, the purified (meth) acrylic acid ester is limited to those having a relatively low boiling point, and those having a high boiling point are (meth) acrylic esters. The acid ester has problems such as a risk of polymerization. In addition, the method disclosed in Japanese Patent Application Laid-Open No. 59-219252 has problems that the process becomes complicated, and it takes a lot of time to remove activated carbon and the like. Further, according to the method disclosed in JP-A-11-263779, solvents and / or reactive diluents include aromatic hydrocarbons such as toluene and xylene, esters such as ethyl acetate and methyl methacrylate, and alcohols such as methanol. However, there is a problem that insoluble impurities are generated.
[0005]
Accordingly, the present invention provides a method for producing a (meth) acrylic acid ester with high yield, high purity and little coloration without going through complicated industrial operations.
[0006]
[Means for Solving the Problems]
That is, the present invention relates to a method for producing an (meth) acrylic acid ester by reacting an alcohol and (meth) acrylic acid in a reaction solvent in the presence of an acid catalyst, and neutralizing the reaction solution after completion of the esterification reaction. After washing with water, the resulting neutralized solution is added with 0.01 to 5% by weight of a basic lithium salt based on the generated (meth) acrylate, and the reaction solvent is distilled while introducing molecular oxygen. The present invention relates to a method for producing a (meth) acrylate, characterized in that a (meth) acrylate is obtained by removing the insoluble matter by filtration.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the method for producing a (meth) acrylate according to the present invention will be specifically described.
[0008]
In the present invention, first, an alcohol and (meth) acrylic acid are esterified in a reaction solvent in the presence of an acid catalyst. In the reaction, it is preferable to use (meth) acrylic acid in excess of the alcohol in order to complete the reaction in a short time and to improve the reaction conversion. Usually, it is preferable to use (meth) acrylic acid in an amount of 1 to 5 mol per 1 mol of the hydroxyl group contained in the alcohol. If the amount of the (meth) acrylic acid is too small, the reaction is slowed, and the alcohol tends to remain. On the other hand, if the amount of (meth) acrylic acid used is too large, the productivity will deteriorate.
[0009]
In the present invention, the alcohol used for the esterification reaction is not particularly limited, but examples thereof include 1-butanol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, trimethylolethane, , 2,6-hexanetriol, pentaerythritol, dipentaerythritol, etc., aliphatic hydrocarbon mono- and / or polyhydric alcohols, tricyclo [5.2.1.0 ^2,6 ] decenol, tricyclo [5.2.1] .0 ^2,6] decanol, tricyclo [5.2.1.0 ^2,6] decenyl oxyethanol, tricyclo [5.2.1.0 ^2,6] dec sulfonyloxy ethanol, tricyclo [5.2 .1.0 ^2,6] decenyl oxy propanol, tricyclo [5.2.1.0 ^2,6] dec sulfonyloxy propanol Tricyclo [5.2.1.0 ^2,6] decenyl oxy ethoxyethanol, tricyclo [5.2.1.0 ^2,6] cycloaliphatic mono- and / or polyhydric alcohols such as deca oxy ethoxyethanol , Polyethylene glycol, polyethylene glycol monoalkyl ether (eg, polyethylene glycol monomethyl ether), polypropylene glycol, polypropylene glycol monoalkyl ether (eg, polypropylene glycol monomethyl ether), polytetramethylene glycol, polytetramethylene glycol monoalkyl ether (eg, polytetramethylene) Glycol monomethyl ether) and other polyalkylene glycol mono- and / or polyhydric alcohols, benzyl alcohol, bisphenol A alkylene Aromatic-containing mono- and / or polyadducts such as oxide adducts (eg, bisphenol A ethylene oxide adduct, bisphenol A propylene oxide adduct) and bisphenol S alkylene oxide adducts (eg, bisphenol S ethylene oxide adduct, bisphenol S propylene oxide adduct). Nitrogen-containing alcohols such as polyhydric alcohols, hydroxypiperidines, and tris (2-hydroxyethyl) isocyanurate.
The present invention relates to alcohols having relatively high hydrophilicity, specifically, polyethylene glycol, polyethylene glycol monoalkyl ether (for example, polyethylene glycol monomethyl ether), bisphenol A ethylene oxide adduct, and tris (2-hydroxyethyl) isocyanate. It has a great effect on nurate and the like, and particularly has a great effect on tris (2-hydroxyethyl) isocyanurate.
[0010]
As the acid catalyst used in the esterification reaction of the present invention, a catalyst in a general esterification reaction is used. For example, paratoluenesulfonic acid, sulfuric acid, benzenesulfonic acid, methanesulfonic acid, ion exchange resins and the like can be mentioned. Of these, paratoluenesulfonic acid, which has few problems such as corroding the kettle and accelerating the production of a polymer, is particularly preferable.
[0011]
The amount of the catalyst used in the present invention is preferably usually in the range of 0.01 to 10.0% by weight based on the total amount of alcohol and (meth) acrylic acid. If the amount is less than 0.01% by weight, the progress of the reaction tends to be slow, and if it exceeds 10.0% by weight, the effect is not particularly improved and the economy tends to be uneconomical.
[0012]
As the reaction solvent used in the present invention, benzene, toluene, xylene, or the like can be used alone or in combination of two or more. However, toluene alone is particularly preferable in terms of handling.
[0013]
In the esterification reaction in the present invention, it is preferable that a polymerization inhibitor is present, as is usually carried out in the production of (meth) acrylate. Examples of the polymerization inhibitor include hydroquinone, hydroquinone monomethyl ether, t-butylcatechol, t-butylhydroquinone, 2,4-dimethyl-6-t-butylphenol, 2,6-di-t-butyl-p-cresol, and parabenzoquinone. , 2,5-diphenylparabenzoquinone, phenothiazine, diphenylamine and the like are used. Above all, hydroquinone monomethyl ether is particularly preferably used as a polymerization inhibitor having little coloring during storage and use of the product.
[0014]
The use amount of these polymerization inhibitors is preferably from 5 to 2,000 ppm, particularly preferably from 10 to 500 ppm, based on the (meth) acrylic acid ester to be produced. If it is less than 5 ppm, the effect of preventing polymerization tends to be insufficient, and if it exceeds 2000 ppm, adverse effects such as inhibition of esterification tend to occur.
[0015]
In the present invention, in order to prevent polymerization of the reaction solution, it is preferable to blow molecular oxygen to cause an esterification reaction. The molecular oxygen is preferably used in a diluted state, and preferably air is used. The blowing of molecular oxygen is also preferable in order to prevent the polymerization of the (meth) acrylic acid ester which evaporates and exists as a vapor or condensed on the upper kettle wall or the like. The amount of molecular oxygen to be used is preferably introduced at a rate of 10 to 1000 ml / min with respect to 1 mol of (meth) acrylate to be produced.
[0016]
The esterification reaction in the present invention is preferably performed at 60 to 120 ° C. under normal pressure or reduced pressure, and particularly preferably 70 to 90 ° C. from the viewpoint of product quality.
As a form of the esterification reaction, a method generally known to those skilled in the art for producing (meth) acrylic acid ester from (meth) acrylic acid and alcohol can be employed. In this method, in order to increase the conversion of alcohols, it is preferable to carry out the synthesis while removing by-product water from the system by azeotropic distillation with the reaction solvent.
[0017]
In the present invention, the reaction solution after the completion of the esterification reaction is neutralized and washed with water to remove unreacted (meth) acrylic acid, catalysts, impurities, and coloring components. A known method can be used for the neutralization, but it is preferable to wash with water or a neutral salt aqueous solution before neutralizing with an alkaline aqueous solution in order to prevent ester decomposition (sapon value) at the time of neutralization. .
[0018]
In the present invention, for washing performed before neutralization, water or an aqueous solution of a neutral salt such as salt or ammonium sulfate is used, but saline is particularly preferable. The amount of water or neutral salt aqueous solution used for washing performed before neutralization is preferably 2 to 30% by weight, more preferably 5 to 20% by weight, based on the reaction solution after the esterification reaction. . Further, when washing with a neutral salt aqueous solution, the concentration of the aqueous solution is preferably 1 to 30% by weight, more preferably 15 to 20% by weight.
[0019]
For the neutralization in the present invention, for example, an aqueous solution of an alkaline substance such as potassium hydroxide, sodium hydroxide, potassium carbonate, and sodium carbonate is used. The amount of the alkaline substance used for the neutralization is preferably 1.01 to 1.5 times the neutralization equivalent of the reaction solution after the completion of the esterification reaction. If the amount of the alkaline substance is less than 1.01, the neutralization tends to be insufficient, and if it exceeds 1.5 times, the wastewater increases, and further, ester decomposition (ken value) tends to occur. The concentration of the aqueous solution of the alkaline substance used here is preferably 1% by weight or more, more preferably 5 to 30% by weight.
[0020]
After the above neutralization, the reaction solution is further washed with water or an aqueous solution of a neutral salt. Water or an aqueous solution of a neutral salt used for washing may have a pH of 8 or less, and particularly preferably a saline solution. The completion of the washing is controlled by the pH, and the washing liquid after the washing is preferably adjusted to pH 8 or less. If the pH is not properly managed, it may not be possible to completely remove (meth) acrylic acid, catalysts, impurities and coloring components.
[0021]
The reaction solution after the completion of the above washing is then subjected to distillation of the reaction solvent. The heating at this time has been a conventional problem that the desired (meth) acrylic acid ester itself is easily colored or polymerized. Therefore, the present invention provides a method for preventing coloring and polymerization by adding a basic lithium salt and distilling off the solvent under a certain temperature condition. Further, the solvent and / or the reactive diluent such as toluene and methacrylic acid may be added. It has been found that a high-quality (meth) acrylic acid ester free of impurities insoluble in methyl acid, methanol and the like can be obtained in high yield. The basic lithium salt is a salt composed of a weak acid and lithium, and examples thereof include lithium carbonate, lithium hydrogen carbonate, and lithium acetate. Among them, lithium carbonate is preferred because of its high effect of preventing coloring and polymerization and easy removal by filtration after distilling off the solvent. The addition amount of the basic lithium salt is preferably 0.01 to 5% by weight, more preferably 0.05 to 0.5% by weight of the (meth) acrylic acid ester formed.
[0022]
The distillation of the reaction solvent in the present invention is preferably carried out under normal pressure or reduced pressure while maintaining the temperature at 90 ° C or lower, more preferably at 80 ° C or lower, particularly preferably at 50 to 80 ° C. Above 90 ° C., it may be difficult to prevent coloring and polymerization only by adding a basic lithium salt, while at a liquid temperature of 50 ° C. or lower, there are disadvantages such as a longer distillation time of the reaction solvent. Occurs.
[0023]
The (meth) acrylate ester from which the above-mentioned reaction solvent has been distilled off must be filtered. The insoluble matter is removed by filtration.
[0024]
As described above, an alcohol and (meth) acrylic acid are subjected to an esterification reaction in a reaction solvent in the presence of an acid catalyst while introducing molecular oxygen. After the reaction, the reaction solution is neutralized and washed. The (meth) acrylic acid ester obtained by adding a basic lithium salt, distilling off the reaction solvent while introducing molecular oxygen, and filtering off the insoluble matter has a high yield, high purity and little coloring, Furthermore, impurities insoluble in solvents and / or aromatic hydrocarbons such as toluene and xylene, esters such as ethyl acetate and methyl methacrylate, and alcohols such as methanol, which are reactive diluents, are not generated.
[0025]
【Example】
Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto.
[0026]
[Example 1]
In a 1 l cylindrical flask (diameter 85 mm) equipped with a stirrer, a thermometer, an air inlet tube, a cooling tube and a drainage device, 160 g (0.61 mol) of tris (2-hydroxyethyl) isocyanurate, 134. 0 g (1.86 mol), 425 g of toluene, 16.0 g of paratoluenesulfonic acid and 0.264 g of hydroquinone monomethyl ether were charged. The pressure in the system was adjusted to 340 mmHg, and the air introduction amount was adjusted to 500 ml / min.
Further, after the stirring rotation speed was set to 320 rpm, the temperature was raised in a hot water bath. While removing water generated during the reaction, the pressure was adjusted so as to maintain the reaction temperature at 80 ° C., and sampling was performed every hour to measure the acid value. When the acid value reached 18 ± 0.5, the reaction was terminated, and the reaction solution was cooled.
When the temperature of the reaction solution became 40 ° C. or lower, 115 g of 16% by weight saline solution was charged, and the mixture was stirred at 300 rpm for 15 minutes and washed with water. After stirring, the mixture was allowed to stand for 15 minutes, and the aqueous layer was extracted.
Subsequently, 49 g of a 25% by weight aqueous sodium hydroxide solution and 69 g of a 16% by weight saline solution were charged and stirred at 300 rpm for 30 minutes. After stirring, the mixture was allowed to stand for 2 hours, and the aqueous layer was extracted. The pH of the aqueous layer was 9.
Subsequently, 115 g of a 16% by weight saline solution was charged and stirred at 300 rpm for 30 minutes. After stirring, the mixture was allowed to stand for 1 hour, and the aqueous layer was extracted. The pH of the aqueous layer was 7-8.
Next, 0.5 g of lithium carbonate was added to the washed organic layer, and the reactor was adjusted to a stirring rotation speed of 300 rpm, an air introduction amount of 500 ml / min, a pressure of 200 mmHg, and heated in a hot water bath. At a liquid temperature of 50 to 55 ° C, toluene began to distill, and the pressure was lowered to 170 mmHg so as not to exceed 80 ° C while monitoring the liquid temperature. Thereafter, the temperature of the solution was adjusted by raising and lowering the hot water bath, and the process was terminated when the toluene content of the solution in the flask became 2% or less, and returned to normal pressure. Vacuum suction filtration was performed while the liquid temperature was 60 ° C. or higher, to obtain 249 g of a product (yield: 95%). The color (APHA) of the product was 40, and the methanol solubility and the toluene solubility were good.
[0027]
[Comparative Example 1]
As a result of performing the same operation as in Example 1 except that sodium hydrogen carbonate was used instead of lithium carbonate, the obtained product was 244 g (yield 94%). Methanol solubility was good and the hue (APHA) was 40, but toluene insolubles were formed.
[0028]
【The invention's effect】
As is clear from the examples, in the present invention, the alcohol and the (meth) acrylic acid are reacted in a reaction solvent in the presence of an acid catalyst, and in the method for producing the desired (meth) acrylate, the neutralization is carried out. Before washing with water, adding a basic lithium salt before distilling off the reaction solvent, and while introducing molecular oxygen, a method characterized by distilling off the solvent under predetermined temperature conditions, A method for producing a (meth) acrylic ester which has high yield, high purity, little coloration, and does not produce impurities insoluble in solvents and / or reaction diluents such as toluene, methyl methacrylate, and methanol. I was able to.

Claims (5)

Alcohol and acrylic acid or methacrylic acid are reacted in a reaction solvent in the presence of an acid catalyst. To the resulting neutralized solution, 0.01 to 5% by weight of a basic lithium salt with respect to the resulting acrylate or methacrylate is added, and while introducing molecular oxygen, the reaction solvent is distilled off to form an insoluble solution. A method for producing an acrylic ester or a methacrylic ester, wherein an acrylic ester or a methacrylic ester is obtained by filtering off the product. The method according to claim 1, wherein the distillation of the reaction solvent is performed at 90 ° C or lower. 3. The method according to claim 1, wherein after the esterification reaction is completed, the reaction solution is washed with water or a neutral salt solution before neutralizing the reaction solution. The method according to any one of claims 1 to 3, wherein the alcohol is tris (2-hydroxyethyl) isocyanurate. The method according to any one of claims 1 to 4, wherein the basic lithium salt is lithium carbonate.