JPH0570408A - Production of 2-(1-hydroxymethyl)acrylic acid alkyl ester - Google Patents

Abstract

(57) [Abstract] [Purpose] Highly pure 2- (1-hydroxymethyl) acrylic acid alkyl ester (hereinafter abbreviated as RHMA)
To provide a method for maintaining a high yield. [Structure] A method for producing RHMA by reacting an acrylic acid alkyl ester with a methanol-containing formaldehyde aqueous solution in the presence of a tertiary amine, wherein the crude RHMA obtained by the reaction is dissolved in water, and a specific solvent is used. A method for producing RHMA, which comprises extracting and removing impurities. [Effect] By using a specific solvent, impurities can be removed efficiently, and the target RHMA can be obtained with high purity and high yield.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing 2- (1-hydroxymethyl) acrylic acid alkyl ester by reacting acrylic acid alkyl ester with formaldehyde in the presence of a tertiary amine, particularly containing methanol. It is intended to provide a method for removing peculiar impurities generated when an aqueous formaldehyde solution is used as a raw material.

[0002]

2. Description of the Related Art As a method for producing 2- (1-hydroxymethyl) acrylic acid alkyl ester, JP-A-61-1
134353 discloses a process characterized in that an alkyl acrylate ester is reacted in the presence of a hydrated formaldehyde or a semi-acetal derived from formaldehyde and an alcohol and a tertiary amine. Here, a methanol-containing formaldehyde aqueous solution which is industrially readily available (that is, methanol is added to about 5% in order to avoid the polymerization of formaldehyde and increase the solubility in water)
Is commercially available as an aqueous solution containing 15% by weight), and after the completion of the reaction, the desired product is extracted with an organic solvent such as diethyl ether,
The extract is rectified to obtain 2- (1-hydroxymethyl) acrylic acid alkyl ester.

[0003]

However, in the extract of crude 2- (1-hydroxymethyl) acrylic acid alkyl ester produced by the above-mentioned production method, a peculiar impurity such as 2 -Since methoxymethoxymethylene acrylic acid alkyl ester, 2-ethoxymethoxymethylene acrylic acid alkyl ester and the like coexist, the separation efficiency is poor even when rectified, and particularly when an intended product having a purity of 98% by weight or more is obtained, distillation yield Since the rate is remarkably reduced, further improvement is required in order to satisfy both industrial quality and yield.

[0004]

The inventors of the present invention have conducted extensive studies to solve the above problems, and as a result,
The present invention has been completed by discovering that impurities that were difficult to remove by a distillation method can be efficiently removed by dissolving-(1-hydroxymethyl) acrylic acid alkyl ester in water and performing extraction with a specific solvent. .. That is, the present invention is
"(A) A step of reacting an acrylic acid alkyl ester with a methanol-containing formaldehyde aqueous solution in an organic solvent compatible with water in the presence of a tertiary amine, (B) obtained in the previous step (A) 2- (1 -Hydroxymethyl) acrylic acid alkyl ester was extracted with an organic solvent incompatible with water, and then the organic solvent was distilled off from the extract to give a crude 2-
A step of obtaining (1-hydroxymethyl) acrylic acid alkyl ester, (C) the crude 2- (1-hydroxymethyl)
At least 1 selected from the group consisting of petroleum ether and hydrocarbons having 5 to 8 carbon atoms by dissolving alkyl acrylate in water.
A step of extracting and removing impurities using a seed solvent, (D) a step of isolating 2- (1-hydroxymethyl) acrylic acid alkyl ester from the aqueous layer obtained in the previous step (C),
A method for producing a 2- (1-hydroxymethyl) acrylic acid alkyl ester comprising a bond of It is.

The feature of the present invention is that the coarse 2- (1
-Hydroxymethyl) acrylic acid alkyl ester (hereinafter abbreviated as RHMA) aqueous solution is used to extract and remove coexisting impurities with a specific solvent.
By this step, impurities that are difficult to separate by distillation can be removed, and a high-purity target product can be obtained in high yield. The present invention will be described in detail below.

Step (A) The step (A) of the present invention comprises a step of reacting an alkyl acrylate ester with a methanol-containing formaldehyde aqueous solution in an organic solvent compatible with water in the presence of a tertiary amine. In the reaction, an acrylic acid alkyl ester is
It is reacted with a methanol-containing aqueous formaldehyde solution in an organic solvent compatible with water at a temperature of 0 to 150 ° C., preferably 0 to 80 ° C. in the presence of a tertiary amine as a catalyst. The pH of the reaction solution is preferably 8 to 13. The reaction is usually carried out at atmospheric pressure, but it can be carried out under reduced pressure or under pressure. When carrying out the reaction at a temperature of 100 ° C. or higher, it is necessary to operate under pressure.

Examples of the alkyl group of the acrylic acid alkyl ester of the present invention include methyl, ethyl, n-propyl and i.
-Propyl and the like. With an alkyl group having a carbon number of at least butyl, the target RHMA is difficult to dissolve in water,
Inappropriate. Although the content of formaldehyde and methanol is not particularly limited as the methanol-containing formaldehyde aqueous solution, it is usually practical to use commercially available formalin containing 37% by weight or more of formaldehyde and about 5 to 15% by weight of methanol. is there. The acrylic acid alkyl ester and formaldehyde are usually reacted in an equimolar ratio, but one of them may be used in excess. For example, the molar ratio of alkyl acrylate and formaldehyde can be changed within the range of 1:20 to 2: 1, preferably 1: 5 to 1: 0.75.

Examples of the tertiary amine include trimethylamine, triethylamine, tri-n-propylamine, triisopropylamine, tributylamine, triisobutylamine, tri-n-pentylamine, N-methyldiisopropylamine, N, N-. Diethylisopropylamine, N, N-dimethylethylamine, N, N-dimethylisopropylamine, tri-2-ethylhexylamine, N-methyldiethylamine, N, N-dimethyl-n-propylamine, N, N-dimethyl-n- Butylamine, N, N-dimethyl-isobutylamine, N, N-
Dimethyl- (2-ethylhexyl) -amine, N, N-
Diisopropyl- (2-ethylhexyl) -amine,
N, N-di-n-butyl- (2-ethylhexyl) -amine, N-methyl-di (2-ethylhexyl) -amine, N-n-butyl-di (2-ethylhexyl) -amine, N-isobutyl- Examples thereof include di (2-ethylhexyl) -amine, 1,4-diazabicyclo- [2,2,2] -octane, pyrocholine and quinolidine, and preferably 1,4-diazabicyclo- [2,2,2] -octane. ,
Pyrocholine and quinolidine are preferred. The amount of the tertiary amine used is 0.1 to 10 parts by weight based on 100 parts by weight of the mixture of alkyl acrylate and formaldehyde.
It is preferably 3 to 8 parts by weight.

Examples of water-compatible organic solvents include methanol, ethanol, isopropanol, n-propanol, butanols, ethylene glycol, propylene glycol, partially or wholly etherified glycols having 2 to 4 carbon atoms, Examples thereof include polyethylene glycol having a molecular weight of 800 or less, dioxane, tetrahydrofuran and acetonitrile, and a mixture of these solvents. The amount of the organic solvent used is 1000 parts by weight or less, preferably 10 to 200 parts by weight, based on 100 parts by weight of the total amount of the alkyl acrylate and the aqueous formaldehyde solution.

Further, since the RHMA produced in this step is very susceptible to polymerization, it is advantageous to use a polymerization inhibitor. Examples of such a polymerization inhibitor include methoxyhydroquinone, benzoquinone, chloranil, Pt-butylcatechol, hydroquinone, phenothiazine, N, N'-diphenyl-P-phenylenediamine and sulfur.
Especially, methoxyhydroquinone and sulfur are preferable. The concentration of such a polymerization inhibitor is 100 to 700 ppm, preferably 300 to 500 ppm in the reaction solution. If it is less than 50 ppm, the effect is insufficient, and if it exceeds 800 ppm, the effect is not exhibited for the added amount.

Step (B) In the step (B), an organic solvent that is incompatible with water is added to the reaction product solution obtained in the previous step (A) to extract RHMA with a solvent, and then the organic solution is extracted from the extract solution. Distill off the solvent to remove crude RHM
This is a step of obtaining A. The organic solvent that is not compatible with water is not particularly limited as long as it is an organic solvent that is incompatible with water and dissolves RHMA, and examples thereof include toluene, xylene, diethyl ether, ethylene dichloride, chloroform, Carbon tetrachloride, ethyl acetate, 4-methyl-2-pentanone, benzene and the like can be mentioned, and toluene, xylene, chloroform and the like are practical.

Step (C): The crude RHMA is dissolved in water, petroleum ether, carbon number 5 to
This is a step of extracting and removing impurities using at least one solvent selected from the hydrocarbons of No. 8. The amount of water used in this step is 1 to 10 times the weight of RHMA, preferably 3 times.
A weight of up to 5 times is practical. The hydrocarbon having 5 to 8 carbon atoms is preferably n-hexane, cyclohexane,
Examples include n-octane. Petroleum ether, carbon number 5
The amount of hydrocarbons used up to 8 is based on the RHMA aqueous solution.
0.1 to 10 times by weight, preferably 0.7 to 1.3 times by weight is used.

Step (D) is a step of isolating RHMA from the aqueous layer obtained in the previous step (C). In such a step, an appropriate amount of a salt of an alkali metal such as sodium chloride, potassium chloride or ammonium chloride or an alkaline earth metal is usually added to the aqueous layer obtained in the previous step (C) to salt out RHMA. Then, a solvent similar to the organic solvent that is not compatible with water used in the step (B) is 0.1 to 5.0 times by weight, preferably 2.0 to 3.0 times the RHMA water layer portion. RHMA using 0 times weight
To extract. After distilling off the solvent of this extract, distillation is performed if necessary. During the distillation, in order to prevent the polymerization of RHMA, the polymerization inhibitor as described above is added in an amount of 300 to 1000.
It is preferable to carry out distillation by adding ppm. As a result, the desired high-purity RHMA is obtained. The RHMA obtained by the production method of the present invention is industrially very useful as a monomer for polymerizing a polymer compound useful for various uses such as paints, pressure-sensitive adhesives and adhesives.

[0014]

[Production] In the production method of the present invention, petroleum ether used as an extractant and hydrocarbons having 5 to 8 carbon atoms are produced when an alkyl acrylate ester is reacted with a methanol-containing formaldehyde aqueous solution. It has a function of extracting and removing peculiar impurities having a boiling point close to that of RHMA.

[0015]

EXAMPLES The present invention will be described in more detail below with reference to examples. Example 1 <(A) Step> Acrylic acid ethyl ester 100.12
g (1.00 mol), 37% by weight formaldehyde aqueous solution (methanol content 7% by weight) 121.85 g (1.5
0 mol), 1.4-diazabicyclo- [2,2,2] -octane 7.00 g (62.6 mmol), methoxyhydroquinone 0.0207 g, and acetonitrile 100 m.
l was mixed, heated to reflux at 80 to 82 ° C. for 1 hour, and reacted.

<Step (B)> The above reaction solution was cooled to 50 ° C., neutralized to pH 5.0 with concentrated hydrochloric acid, and diluted with 200 ml of toluene.
The desired product was extracted with l. The toluene was distilled off to obtain crude 2
-(1-Hydroxymethyl) acrylic acid ethyl ester (hereinafter abbreviated as EHMA) 140.38 g (purity 4
3.2% by weight, yield 46.6%, selectivity to charged ester 5
6.9%). The composition of this crude EHMA is shown below. EHMA 43.2% by weight Methoxy form 3.3% by weight Ethoxy form 1.2% by weight Dehydration condensate 3.2% by weight Acetal form 3.2% by weight Diacetal form 0.6% by weight Others 0.71% by weight

[0017]

<Step (C)> The crude EHMA (30.0 g) was dissolved in water (150 ml) and extracted twice with 60 ml of petroleum ether to remove impurities. <Step (D)> Sodium chloride was added to the aqueous layer portion obtained in the previous step (C) until it was saturated, and the mixture was extracted with toluene.
When toluene was distilled off under reduced pressure from the extract, the target E
HMA was obtained as 26.8 g (purity 98.1% by weight), and EH
The recovery rate of MA was 95.0% by weight, the overall yield of EHMA was 43.4%, and the purity was 98.1% by weight. The composition of this EHMA is shown below. EHMA 98.1% by weight methoxy trace ethoxy trace trace dehydration condensate 0.1% by weight acetal 0.2% by weight diacetal 0.2% by weight other 1.4% by weight Note) methoxy, ethoxy, dehydration condensation Body, acetal and diacetal are the same as above.

Comparative Example Crude EHMA 109.8 obtained in step (B) of Example 1
1 g was distilled at 86.7-87.6 ° C./5.0 mmHg to obtain 47.43 g of EHMA having a purity of 98.2% by weight.
However, the distillation yield of EHMA was remarkably low at 46.0% by weight. On the other hand, when the distillation yield was increased to 95% by weight, the purity dropped to 45.0% by weight.

Example 2 An experiment was conducted in the same manner as in Example 1 except that n-hexane was used instead of the petroleum ether in the step (C) in Example 1. As a result, 27.39 g (purity: 97.7% by weight) of the target EHMA was obtained. The overall yield was 44.0%. Example 3 An experiment was performed in the same manner as in Example 1 except that cyclohexane was used instead of the petroleum ether in the step (C). As a result, 25.41 g (purity 98.8% by weight) of the target EHMA was obtained. The overall yield was 41.8%.

Example 4 In step (A) of Example 1, ethyl acrylate 1 was added.
An experiment was conducted in the same manner as in the same example except that 86.09 g (1.00 mol) of acrylic acid methyl ester was used instead of 00.12 g (1.00 mol). (B) At the end of the process, coarse 2
-(1-Hydroxymethyl) acrylic acid methyl ester (hereinafter abbreviated as MHMA) 63.70 g (purity 87.
5% by weight, yield 48%) was obtained. After the completion of step (D), 25.63 g (purity 98.5% by weight) of the target MHMA was obtained, and the overall yield was 45.5%.

Example 5 In step (A) of Example 1, acrylic acid ethyl ester 1 was used.
An experiment was conducted in the same manner as in the example except that 114.14 g (1.00 mol) of isopropyl acrylic acid ester was used instead of 00.12 g (1.00 mol). At the end of the step (B), crude 2- (1-hydroxymethyl) acrylic acid isopropyl ester (hereinafter abbreviated as i-PHMA) 6
4.3 g (purity 85.0% by weight, yield 37.7%) was obtained. After the step (D), the target i-PHMA is 23.5.
g (purity 98.0% by weight) was obtained, and the overall yield was 33.4%.
Met.

Claims (1)

[Claims] 1. A step (A) of reacting an alkyl acrylate ester with a methanol-containing formaldehyde aqueous solution in an organic solvent compatible with water in the presence of a tertiary amine,
(B) The 2- (1-hydroxymethyl) acrylic acid alkyl ester obtained in the previous step (A) is extracted with an organic solvent that is incompatible with water, and then the organic solvent is distilled off from the extract to give a crude 2 A step of obtaining an alkyl ester of (1-hydroxymethyl) acrylic acid, (C) the crude alkyl ester of 2- (1-hydroxymethyl) acrylic acid is dissolved in water, and the mixture is converted from petroleum ether or a hydrocarbon having 5 to 8 carbon atoms. A step of extracting and removing impurities by using at least one selected solvent, (D) from the aqueous layer portion obtained in the previous step (C),
A process for producing a 2- (1-hydroxymethyl) acrylic acid alkyl ester, which comprises the step of isolating the (1-hydroxymethyl) acrylic acid alkyl ester.