JP2000159726A - Production of hydroxyalkyl acrylate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a hydroxyalkyl acrylate, capable of enhancing the reaction conversion of methyl acrylate, suitably controlling the conversion of an alkanediol and maximizing the production of the hydroxyalkyl acrylate which is a monoester compound. SOLUTION: This method for producing a hydroxyalkyl acrylate comprises subjecting a 2-10C alkanediol and methyl acrylate to a transesterification in the presence of a catalyst. Therein, the methyl acrylate is used in an amount of 0.5-2 fold moles that of the alkanediol, and the reaction is carried out, while the by-produced methanol is removed as an azeotropic mixture by a reactive distillation in the presence of an azeotropic solvent (for example, n-hexane) with methanol.

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 a hydroxyalkyl acrylate, and more particularly, to a method for producing a hydroxyalkyl acrylate by subjecting an alkanediol and methyl acrylate to a transesterification reaction in the presence of a catalyst. The production of industrially advantageous hydroxyalkyl monoacrylates, in which the reaction rate was increased by efficiently removing the by-product methanol to the outside of the reaction system, and the methanol could be separated without loss of raw materials. It is about the method.

[0002] Hydroxyalkyl acrylates share a hydrophobic alkyl unit and a hydrophilic hydroxyl group in the molecule, so that polymers or copolymers having practically interesting physical properties with appropriate flexibility and hydrophilicity are provided. Since it is useful as a raw material and its hydroxyl group is highly reactive, it is expected to be used as a crosslinkable polymer or copolymer in paint-related applications.

[0003]

2. Description of the Related Art As a method for producing a hydroxyalkyl acrylate, a direct esterification method in which an alkanediol and a carboxylic acid are subjected to an esterification reaction in the presence of an acidic catalyst is known (German Patent No. 1518572;
JP-A-4-69353, JP-A-7-126214
No.).

The direct esterification method has many problems. For example, the method described in the above-mentioned German Patent No. 1518572 uses a strong acid catalyst, so that there is a concern about corrosion of the reactor, and it involves a cyclization reaction of the alkanediol as a raw material and a high boiling of the product. Therefore, there is a disadvantage that the selectivity of the target hydroxyalkyl acrylate is lowered. Furthermore, since the above-mentioned method neutralizes the reaction catalyst and unreacted acrylic acid in the state of an aqueous solution, it is difficult to separate the water-soluble alkanediol from the neutralized salts at the time of recovery and reuse.

In order to overcome the above-mentioned problems, the present inventors have developed a method for producing a hydroxyalkyl acrylate by transesterifying an alkanediol and a lower ester of acrylic acid in the presence of a distanoxane catalyst. It was proposed (Japanese Patent Application No. 10-152175).

However, when methyl acrylate is used as a reaction raw material in the transesterification method, there are the following problems. In other words, when the reaction is carried out in the absence of a solvent, methanol produced as a by-product of the reaction azeotropes with the methyl acrylate, so that when the methanol is removed by reactive distillation, the raw material methyl acrylate accompanies the distillation distillate. Loss.

The above azeotropic composition under normal pressure conditions has a weight ratio of methanol: acrylic acid methyl ester of about 50:50.
It is. Therefore, when recovering methyl acrylate from a mixture having such an azeotropic composition, a complicated separation process is required.

On the other hand, there is also disclosed a technique capable of reducing the distillation loss of methyl acrylate by performing reactive distillation in the presence of a third component azeotropic with methanol in a reaction system. For example, in the example of JP-A-7-238058, n-hexane and cyclohexane are exemplified as the third component used in the transesterification reaction between tetrahydrobenzyl alcohol and methyl (meth) acrylate. In this embodiment, methyl (meth) acrylate is used in a large excess with respect to the alcohol in order to maximize the conversion of the starting alcohol.

However, when the above method is applied to the production of hydroxyalkyl acrylate, there are the following problems.

(1) When a large excess of methyl acrylate is used, the by-product of the diester in which two hydroxyl groups of the alkanediol are esterified increases. In addition, the conversion rate of acrylic acid methyl ester decreases, and the load of collecting and removing unreacted acrylic acid methyl ester increases.

(2) When a minimum amount of methyl acrylate is used for the reaction, the reaction rate is reduced at the end of the reaction when the concentration of methyl acrylate is reduced. Also, when the concentration of methyl acrylate decreases, the boiling point of the reaction mixture increases significantly due to the increase in boiling point,
The distillation temperature in the reactive distillation is increased, which may cause an undesirable reaction such as a polymerization reaction.

(3) As an azeotropic solvent, n-hexane is particularly suitable for reducing the loss of acrylic acid methyl ester. However, when an excessive amount of n-hexane is supplied to the reaction system, the reaction temperature is lowered due to a decrease in boiling point. And the reaction slows down.

(4) When the amount of the azeotropic solvent is small, the reaction temperature changes largely as the solvent is discharged out of the system as the reaction proceeds, and the loss of methyl acrylate increases.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to increase the reaction conversion of methyl acrylate, appropriately control the conversion of alkanediol, It can maximize the amount of hydroxyalkyl acrylate that is an ester compound,
An object of the present invention is to provide a method for producing a hydroxyalkyl acrylate.

[0015]

That is, the gist of the present invention is to provide a method for producing a hydroxyalkyl acrylate by subjecting an alkanediol having 2 to 10 carbon atoms to a transesterification reaction with methyl acrylate in the presence of a catalyst. The amount of acrylic acid methyl ester used is 0.5 to 2 times the molar amount of the alkanediol compound, and the reaction is carried out while removing by-product methanol as an azeotropic mixture by reactive distillation in the presence of an azeotropic solvent with methanol. And a method for producing a hydroxyalkyl acrylate.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail for each step.

<Reaction Step> One raw material for the transesterification in the present invention is an alkanediol having 2 to 10 carbon atoms. Such alkanediols include ethylene glycol, butanediol, hexanediol,
Decanediol and the like. In particular, 1,4-butanediol is preferably used. Another source material in the present invention is acrylic acid methyl ester.

In the present invention, the above-mentioned alkanediol diacrylate can coexist in the reaction system. Examples of such a compound include 1,4-butanediol diacrylate. This compound has 1,
Although it is a by-product during the production of 4-hydroxybutyl acrylate by the reaction of 4-butanediol and methyl acrylate, it is converted to 4-hydroxybutyl acrylate by transesterification with 1,4-butanediol. Also acts as a raw material.

In the present invention, a general-purpose transesterification catalyst can be used as the reaction catalyst. Examples of such a reaction catalyst include acids such as sulfuric acid, Lewis acids, metal alkoxides, and the like. In the present invention, a titanium-based compound such as tetraalkyl titanate or a tin-based compound such as dialkyltin oxide is preferable from the viewpoint of high selectivity. Among them, a tetraalkyldistannoxane represented by the following general formula (I) is preferable. The compound is preferably used from the viewpoint of recovery and reuse of the catalyst.

[0020]

Embedded image

In the general formula (I), the alkyl groups represented by R ¹ , R ² , R ³ and R ⁴ are usually alkyl groups having 1 to 20 carbon atoms. , Ethyl group, propyl group, butyl group, pentyl group, octyl group,
Dodecyl group, stearyl group and the like can be mentioned. Further, the substituent in the phenyl group which may have a substituent is
Usually, it is an alkyl group, and specific examples thereof include the same alkyl groups as described above. The alkyl group or the optionally substituted phenyl group for R ^{1 to} R ⁴ is
They may be different from each other. As R ^{1 to} R ⁴ ,
From the viewpoints of catalyst extraction recovery rate and catalyst solubility in the extraction separation in the post-reaction step, an alkyl group having 4 to 12 carbon atoms and a phenyl group are preferable, and among them, an alkyl group having 8 carbon atoms is preferable from industrial availability. Is particularly preferred.

In the general formula (I), X and Y represent -O
_{H, -O (CH 2) n} OH, -O (CH 2) n OCOCH =
CH ₂ , —OR, —OCOR, —OCOCH = CH ₂ (n
Represents an integer of 1 to 10, R represents alkyl) and a halogen atom. Of these, good hydrolysis resistance of the catalyst, extraction efficiency in terms of high, preferably -OCOR or -OCOCH = CH _2.
The above n is preferably 2 to 6, and R is preferably an alkyl group having 1 to 8 carbon atoms. Examples of the halogen atom include Cl and Br.

The above stannoxane compounds can be easily obtained by the method described in, for example, Advance in Organometallic Chemistry, Vol. 5, p. 159 (1967).

Since the transesterification reaction between alkanediol and methyl acrylate is an equilibrium reaction, the reaction conversion is suppressed by the presence of methanol as a by-product. Therefore, in the present invention, the reaction is carried out by reactive distillation in the presence of an azeotropic solvent with methanol while removing by-product methanol as an azeotropic mixture. The conversion of methyl acrylate and diol can be increased by such reactive distillation. If no azeotropic solvent is used, methanol forms an azeotrope with methyl acrylate. Therefore, removal of methanol involves loss of the raw material methyl acrylate. On the other hand, according to the present invention, it is possible to prevent the methyl acrylate from distilling out of the reaction system and increase the conversion of the methyl acrylate. When a hydrocarbon solvent described below is used as the azeotropic solvent, the increase in the boiling point of the reaction system caused when the concentration of methyl acrylate decreases in the latter half of the reactive distillation is suppressed, and an appropriate reaction temperature is maintained. There is also the effect of doing.

The type of the reactive distillation column to be used is not particularly limited, and a packed column, a tray column and the like can be used. The theoretical plate number of the reactive distillation column is usually 3 to 50 plates, preferably 5 to 20 plates.

In the present invention, the use ratio of acrylic acid methyl ester to 1 mole of alkanediol is 0.5 to 2 moles, preferably 0.5 to 2 moles in terms of acrylic group.
２2 mol. With the use ratio in this range, the ratio of the hydroxyalkyl acrylate in the reaction product can be maximized by appropriately converting the alkanediol, the productivity can be increased, and the overall extraction efficiency can be increased.

The alkanediol and its three components, monoester and diester, have an equilibrium relationship, and by controlling the conversion of the alkanediol used in the reaction, the composition distribution of the three components changes. The esterification of about 50% of the hydroxyl groups of the alkanediol maximizes the monoester abundance. When the amount of the methyl acrylate used per mole of the alkanediol exceeds 2 moles, it is difficult to control the conversion of the alkanediol, the conversion of methyl acrylate decreases, and the formation of the diester increases. The yield of the desired hydroxyalkyl acrylate decreases. Conversely, if it is less than 0.5 mole, the conversion of the alkanediol is not sufficient,
The yield of the desired product is low, resulting in an inefficient process.

On the other hand, the use ratio of the reaction catalyst is usually 0.01 to 50 mol%, preferably 0.1 to 20 mol%, based on the raw material, though it depends on the kind.

At the time of the reaction, it is preferable to add a polymerization inhibitor to the reaction system in order to prevent polymerization of the raw materials and products. Examples of the polymerization inhibitor include phenothiazines, hydroquinones, and copper compounds such as copper salts of dialkyldithiocarbamic acids. Furthermore, by having molecular oxygen present in the reaction system, usually, air is directly or diluted with an inert gas such as nitrogen and continuously introduced into the reaction system, whereby the polymerization prevention effect is further enhanced. Often.

In the present invention, as the azeotropic solvent with methanol, an aliphatic or alicyclic hydrocarbon having 6 or 7 carbon atoms is preferably used. Specific examples of such hydrocarbons include n-hexane, cyclohexane, and n-heptane, and n-hexane is particularly preferred in that it minimizes the distillation loss of methyl acrylate.

The amount of the azeotropic solvent used in the reaction may be at least an amount sufficient to form an azeotrope with methanol as a by-product and to distill off the methanol. However, when the amount of solvent to the reaction liquid is too large, the production efficiency is lowered, because it causes a decrease in the reaction rate, the reaction raw material liquid 5
It is preferred that the content be 0% by weight or less.

The azeotropic solvent may be continuously supplied to the reactor or may be supplied to the reactor all at once from the beginning of the reaction. However, the larger the amount of the azeotropic solvent used, the lower the reaction temperature and the lower the reaction rate. Therefore, in order to carry out the reaction while maintaining a high reaction rate and preventing the distillation loss of methyl acrylate, it is preferable to control the concentration of the azeotropic solvent present in the reaction system to 0.2 to 20% by weight.

Specifically, the concentration of the azeotropic solvent in the initial stage of the reaction is set to 0.2 to 20% by weight, and if the azeotropic solvent becomes insufficient due to the progress of the reactive distillation, the necessary amount is continuously supplied. As the continuous supply method, either a method of continuously supplying a predetermined amount at all times or a method of repeatedly supplying a predetermined amount intermittently may be used. When n-hexane capable of minimizing the distillation loss of methyl acrylate is used, the effect of lowering the reaction temperature on the supply amount of n-hexane is large, and
Since the amount of solvent required for azeotroping with methanol is large, the above continuous supply method is particularly effective.

In any of the above continuous supply methods, the temperature of the reaction solution and the temperature of the rectification column can be used for controlling the appropriate supply amount of the azeotropic solvent. For example, in the case of normal pressure, the reaction temperature is in the range of 75 to 110 ° C, and the temperature of the rectification column is the azeotropic temperature of methanol and hydrocarbon (hexane: 50 ° C, cyclohexane: 55 ° C, heptane: 58 ° C). ), It can be determined that the supply amount of the azeotropic solvent is appropriate.

The rectification column is operated under appropriate reflux so that azeotropy between methanol and the azeotropic solvent is maintained. The rate of distillation of the azeotrope (the amount of distillate per hour) is increased or decreased according to the rate of methanol production by the reaction. Generally, the reaction rate increases when the formed methanol is removed from the reaction system as quickly as possible. However, if the distillation rate of the azeotrope is too high, methanol becomes insufficient and methyl acrylate increases in the distillate. Therefore, in order to shorten the reaction time and achieve a high conversion of methyl acrylate, monitor the temperature of the rectification column and control the distillation rate so that methanol and the azeotropic solvent are stabilized at the azeotropic temperature. Is preferred.

The reaction pressure may be any of pressurization, normal pressure and reduced pressure, but conditions close to normal pressure are preferably used because of easy operability. The reaction temperature is usually 60 to 15
0 ° C, preferably 70 to 130 ° C. Reaction temperature 6
If the temperature is lower than 0 ° C., sufficient reaction activity cannot be obtained.
When the temperature exceeds 150 ° C., side reactions such as polymerization tend to occur. The reaction time is usually 2 to 15 hours, and the reaction reaches an equilibrium depending on the reaction time. In particular, by keeping the temperature of the reaction solution at 75 to 110 ° C., the concentration of the azeotropic solvent in the reaction solution can be kept in a suitable range.

The azeotropic solvent distilled together with methanol can be separated from the methanol phase by cooling or adding water, and can be reused in the reaction system. In the case of cooling, the mixture is cooled to a temperature in the range of −30 to 40 ° C., the mutual solubility with methanol is reduced, and the mixture is allowed to stand for separation. When water is added, water is used in an amount of about 0.05 to 10 times the weight of methanol. And mixing with water, mechanical stirring,
This is performed using a static mixer or the like, and the distillate and the water are sufficiently brought into contact with each other, and then separated by standing. In general, the method of adding water can reduce the methanol content in the recovered azeotropic solvent.

<Product Recovery Step> After the completion of the reactive distillation, the unreacted alkanediol, hydroxyalkyl acrylate and alkyl diacrylate monoesters, an azeotropic solvent and a small amount of unreacted methyl acrylate are contained in the reaction solution. include.

Therefore, after the catalyst is separated from the reaction solution as required, the hydroxyalkyl acrylate is separated by a separation method such as distillation, liquid-liquid extraction, adsorption and crystallization. For example, in the case of a method for producing 4-hydroxybutyl acrylate by a transesterification reaction of 1,4-butanediol and methyl acrylate using a distannoxane catalyst, a mixed solvent of an aliphatic or alicyclic hydrocarbon and water is used. By liquid-liquid extraction, the by-produced 1,4-butanediol diacrylate and the catalyst are extracted and separated into a hydrocarbon phase, and the remaining aqueous solution of 4-hydroxybutyl acrylate and 1,4-butanediol is extracted with a polar organic solvent using a polar organic solvent. Hydroxyalkyl acrylate can be extracted.

In particular, diester extraction solvents include n
-Aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane are preferably used. Thus, the process can be simplified by using the same extraction solvent as the azeotropic solvent. If the diacrylate compound separated by the liquid-liquid extraction is circulated to the reaction system, the diacrylate compound is reconverted into a hydroxyalkyl acrylate by a transesterification reaction with an alkanediol, so that the hydroxyalkyl acrylate can be efficiently produced.

[0041]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention.

In the following examples, unless otherwise specified, the reaction was conducted in a rectification column, a temperature measuring tube, an air introducing tube, a solvent introducing tube, and a jacket (corresponding to steam heating).
The above rectification column (70φ) is filled with 1/4 inch McMahon packing at a height of 60 cm.
A 0 L stainless steel reactor was used, and a countercurrent contact type liquid-liquid extraction column (Sumitomo Heavy Industries: Curl column 25) was used for extraction.
φ1.5 m) was used. The number of theoretical plates in the rectification column corresponds to about 5 plates. In the following description, the following abbreviations are used.

[0043]

[Table 1] 1,4-BG: 1,4-butanediol AEM: Acrylic acid methyl ester HX: n-hexane CHX: cyclohexane HP: n-heptane MeOH: methanol 4-HBA: 4-hydroxybutyl acrylate BDA: 1 , 4-butanediol diacrylate

Example 1 In a reactor, 1,4-BG: 5.41 kg (60 mol)
l), AEM: 4.65 kg (54 mol), HX: 1
30 g, diacryloyloxydistannoxane: 160
g, phenothiazine: 24 g, and transesterification was carried out in the following manner while continuously supplying a small amount of the polymerization inhibitor-containing HX from the top of the rectification column.

From the air inlet tube, 6 at 750 ml / min
Volume% oxygen / nitrogen was blown. Heating was started by flowing steam through the jacket of the reactor. Boiling started at a liquid temperature of about 84 ° C. The total reflux was performed for 1 hour, and the temperature at the top of the rectification column and at the middle stage of the column was stabilized at 50 ° C.

Thereafter, distillation of an azeotrope of MeOH and HX was started under the condition of a reflux ratio of 10. The distillation rate of the azeotrope was about 1 L / Hr. Then, after the temperature of the rectification column started to rise, continuous supply of hexane to the reactor was started. The supply rate was about 700 ml / Hr. The continuous supply of HX was adjusted so that the temperature of the reaction solution was 84 to 108 ° C. During this time, the concentration of HX in the reaction solution was 0.5 to 2
Weight percent. The top temperature of the rectification column was almost constant at 50 ° C. The distillate was switched when 5.5 Hr had passed since the start of distillation and the amount of distillate reached 6.8 L. Hereinafter, the distillate before the fraction switching (MeOH fraction) is referred to as distillate (A), and the distillate after fraction switching is referred to as distillate (B).

The amount of the distillate (A) was 4720 g, and the composition was determined by gas chromatography to be HX: 6.
9.3% by weight (3270 g), MeOH: 24.6% by weight
% (1160 g), AEM: 6.1% by weight (288 g)
Met.

After the distillate was switched, the continuous supply of HX was temporarily stopped, the pressure in the reactor was reduced to 300 mmHg, and the remaining methyl acrylate was recovered.
Was continuously supplied, and the remaining AEM was recovered together with hexane. The top temperature of the rectification column once dropped to 30 ° C., but rose again and became constant at about 40 ° C., so the distillation was terminated. The time required from the switching of the fraction to the end of the distillation was about 1.5 hours.

The amount of the distillate (B) was 2136 g, and the composition was HX: 76% by weight (1630 g), MeO
H: 11.7% by weight (250 g), AEM: 11.8% by weight (252 g).

On the other hand, the composition of the reaction solution after removing the distillate (B) was 1,934 g for 1,4-BG and 4 for 4-HBA.
135 g, BDA: 1797 g, HX: 107 g, AE
M: 29 g.

The conversion with respect to the AEM charged in the reactor was 86.7%, and the amount of AEM mixed in the distillate (A) was 6.2% by weight based on the charged amount. The conversion rate of AEM was determined by the following equation.

[0052]

## EQU1 ## (mol number of esterified hydroxyl group of 1,4-BG) / (mol number of AEM) × 100

Example 2 1,4-BG: 5.41 kg (60 mol)
1), AEM: 4.65 kg (54 mol), CHX:
3490 g, diacryloyloxydistannoxane: 4
74 g and phenothiazine: 60 g were charged, and a transesterification reaction was carried out in the following manner while continuously supplying a small amount of HX containing a polymerization inhibitor from the top of the rectification column.

From the air inlet tube, 6 at 750 ml / min.
Volume% oxygen / nitrogen was blown. Heating was started by flowing steam through the jacket of the reactor. Boiling started at a liquid temperature of about 70 ° C. The total reflux was performed for 1 hour, and the temperature at the top of the rectification column was stabilized at 54 ° C.

Thereafter, distillation of an azeotropic mixture of MeOH and CHX was started under the condition of a reflux ratio of 10. The distillation rate of the azeotropic mixture is about 0.5 L so that the temperature of the rectification column does not rise.
/ Hr. When the amount of the distillate reached 4.0 L after the elapse of 8.0 hours from the start of the distillation, the temperature of the rectification column began to rise sharply, so that the fraction was switched. Hereinafter, the distillate before the distillate was switched was represented as distillate (A), and the distillate after the distillate was switched was represented as distillate (B).

The amount of the distillate (A) was 3,066 g, and the composition was determined by gas chromatography to be CH
X: 56.3% by weight (1730 g), MeOH:
9% by weight (916 g), AEM: 13.8% by weight (42
4g).

After the distillate was switched, the distillation was further continued at normal pressure. When the distilling temperature reached 71 ° C., the distillation was terminated. At this time, the temperature of the reaction solution was 105 ° C.

The amount of the distillate (B) was 1352 g, and the composition was determined by gas chromatography to be CH 2
X: 52.7% by weight (712 g), MeOH: 17.8
% (241 g), AEM: 29.5% by weight (399
g).

On the other hand, the amount of the reaction solution after removing the distillate (B) was 9060 g, and the composition was 1,4-BG:
2130 g, 4-HBA: 4110 g, BDA: 154
0 g, CHX: 740 g, and AEM: 60 g.

The conversion with respect to AEM charged in the reactor was 81.6%, and the amount of AEM mixed in the distillate (A) was 9.1% by weight based on the charged amount.

Example 3 1,4-BG: 5.41 kg (60 mol)
l), AEM: 4.65 kg (54 mol), HP: 3
000 g, diacryloyloxydistannoxane: 16
0 g and phenothiazine: 60 g were charged, and a transesterification reaction was performed in the following manner while continuously supplying a small amount of HX containing a polymerization inhibitor from the top of the rectification column.

From the air inlet tube, 6 at 750 ml / min
Volume% oxygen / nitrogen was blown. Heating was started by flowing steam through the jacket of the reactor. Boiling started at a liquid temperature of about 78 ° C. The total reflux was performed for 1 hour, and the temperature at the top of the rectification column was stabilized at 58 ° C.

Thereafter, distillation of an azeotropic mixture of MeOH and HP was started under the condition of a reflux ratio of 10. The distillation rate of the azeotrope is about 0.3 to not increase the temperature of the rectification column.
It was maintained at 0.6 L / Hr. When the amount of distillate reached 3.8 L after 8.0 hours had passed from the start of distillation, the temperature of the rectification column began to rise sharply, so that the fraction was switched. Hereinafter, the distillate before distillate switching is referred to as distillate (A),
The distillate after distillate switching was represented as distillate (B).

The amount of the distillate (A) was 2850 g, and the composition was determined by gas chromatography analysis as HP:
40.8% by weight (1160g), MeOH: 39.1% by weight (1110g), AEM: 20.1% by weight (570)
g).

After the distillate was switched, the distillation was further continued at normal pressure, and the distillation was stopped when the distilling temperature reached 93 ° C. At this time, the temperature of the reaction solution was 102 ° C. Met.

The amount of the distillate (B) was 665 g, and the composition was determined by gas chromatography analysis to be HP: 5
6.6% by weight (376 g), MeOH: 12.4% by weight
(62 g), AEM: 31.0% by weight (206 g).

On the other hand, the amount of the reaction solution after removing the distillate (B) was 9220 g, and its composition was 1,4-BG:
2170 g, 4-HBA: 4060 g, BDA: 150
0 g, HP: 880 g, AEM: 41 g.

The conversion with respect to AEM charged in the reactor was 78.9%, and the amount of AEM mixed in the distillate (A) was 12.4% by weight based on the charged amount.

Comparative Example 1 In a reactor, 1,4-BG: 5.41 kg (60 mol)
l), AEM: 4.65 kg (54 mol), diacryloyloxydistannoxane: 160 g, phenothiazine: 24 g were charged, and a transesterification reaction was performed in the following manner.

From the air inlet tube, 6 at 750 ml / min
Volume% oxygen / nitrogen was blown. Heating was started by flowing steam through the jacket of the reactor. Boiling started at a liquid temperature of about 86 ° C. The total reflux was performed for 1 hour, and the temperature at the top of the rectification column and at the middle stage of the column was stabilized at 62 ° C.

Thereafter, distillation of an azeotropic mixture of MeOH and AEM was started under the condition of a reflux ratio of 10. Distillation was switched when the temperature of the reaction solution reached 120 ° C. after elapse of 3.0 hours from the start of distillation. Hereinafter, the distillate before the distillate was switched was represented as distillate (A), and the distillate after the distillate was switched was represented as distillate (B).

The amount of the distillate (A) was 850 g, and the composition was MeOH: 51% by weight and AEM: 49% by weight.

After the fraction was switched, the reaction distillation was continued while gradually reducing the pressure in the reactor. To lower the pressure, the amount of oxygen-containing gas blown into the liquid was gradually reduced.
When the pressure became 100 mmHg or less, the distillate could hardly be cooled and condensed. Finally, distillation was stopped at a pressure of 20 mmHg and a liquid temperature of 120 ° C.

The amount of the distillate (B) was 1410 g, and the composition was MeOH: 37% by weight, AEM: 63% by weight.
Met.

The amount of the reaction solution recovered by removing the distillate (B) was 7550 g, and its composition was 1,4-BG:
2600 g, 4-HBA: 3630 g, BDA: 107
It was 0 g. The total amount of the distillate was 2260 g, and the composition was 950 g of MeOH and 131 g of AEM.
It was 0 g.

The conversion to AEM charged in the reactor was 68%, and the A mixed in the distillates (A) and (B)
EM was 28% by weight based on the charged amount.

Comparative Example 2 1,4-BG: 3600 g (40 mol)
AEM: 7750 g (90 mol), HX: 300 g,
Tetraoctyl diacryloyloxydistannoxane:
160 g and phenothiazine: 40 g were charged, and a transesterification reaction was carried out in the following manner while continuously supplying a small amount of HX containing a polymerization inhibitor from the top of the rectification column.

From the air inlet tube, 6 at 750 ml / min
Volume% oxygen / nitrogen was blown. Heating was started by flowing steam through the jacket of the reactor. Boiling started at a liquid temperature of about 84 ° C. The total reflux was performed for 1 hour, and the temperature at the top of the rectification column and the middle stage of the column was stabilized at 50 ° C.

Thereafter, distillation of an azeotropic mixture of MeOH and HX was started under the condition of a reflux ratio of 10. The distillation rate of the azeotrope was about 1 L / Hr. Then, after the temperature of the rectification column started to rise, continuous supply of hexane to the reactor was started. The supply rate was about 700 ml / Hr. The continuous supply of HX was adjusted so that the temperature of the reaction solution was 80 to 102 ° C. During this time, the concentration of HX in the reaction solution was 0.5 to 5
Weight percent. The top temperature of the rectification column was almost constant at 50 ° C. Distillate switching was performed when the amount of distillate reached 11.2 L after 10.5 hours had elapsed from the start of distillation. Hereinafter, the distillate before the distillate was switched was represented as distillate (A), and the distillate after the distillate was switched was represented as distillate (B).

The amount of the distillate (A) was 7,870 g, and the composition was HX: 70.2% by weight (5530 g), Me
OH: 23.4% by weight (1840 g), AEM: 6.4
% By weight (500 g).

[0081] After fraction switching, temporarily stops the continuous supply of HX, the pressure in the reactor was evacuated to 300MmH g, was recovered acrylic acid methyl ester remaining, again HX
Was continuously supplied, and the remaining AEM was recovered together with hexane. The top temperature of the rectification column once dropped to 30 ° C., but rose again and became constant at about 40 ° C., so the distillation was terminated.

The amount of the distillate (B) was 3400 g, and the composition was HX: 53% by weight (1800 g), MeO
H: 11.2% by weight (380 g), AEM: 35.9% by weight (1220 g).

On the other hand, the amount of the reaction solution after removing the distillate (B) was 8150 g, and the composition was 1,4-BG:
43 g, 4-HBA: 1180 g, BDA: 6070 g
Met.

The conversion of AEM charged into the reactor was 77.0%, and the amount of AEM mixed in the distillate (A) was 6.5% by weight based on the charged amount. Also, 1,4-
The conversion of BG was 98.8%.
The amount of 4-HBA produced relative to BG was 20% by weight,
It was about 40% compared to Example 1.

Comparative Example 3 In a 100 ml reactor, 1,4-BG: 90 g (1 mol)
1), AEM: 86 g (0.9 mol), HX: 10
g, tetraoctyl diacryloyloxydistannoxane: 5.2 g, phenothiazine: 0.36 g,
The reaction was performed under reflux conditions.

The reaction was carried out at about 73 ° C. for 30 hours, and it was confirmed that the reaction reached equilibrium. The composition at this time is 1,4
-BG: 47 g, 4HBA: 59 g, BDA: 15 g, and the conversion of AEM was 62%.

[0087]

[Table 2]

[0088]

According to the present invention, the distillation loss of methyl acrylate is prevented, the reaction utilization of methyl acrylate is increased, the high reaction rate is maintained, and the yield of the monoester is maximized. The transesterification reaction can be carried out as follows, and therefore, the hydroxyalkyl acrylate can be industrially advantageously produced.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // C07B 61/00 300 C07B 61/00 300 F term (reference) 4H006 AA02 AC48 AD16 BB11 BC30 BC31 BD20 BD35 BD52 BN10 KA03 4H039 CA66 CD10 CD40

Claims (5)

[Claims] When producing a hydroxyalkyl acrylate by subjecting an alkanediol having 2 to 10 carbon atoms to a transesterification reaction with a methyl acrylate in the presence of a catalyst, the amount of the methyl acrylate used relative to the alkanediol compound is reduced. A method for producing a hydroxyalkyl acrylate, wherein the reaction is carried out by removing the by-produced methanol as an azeotropic mixture by reactive distillation in the presence of an azeotropic solvent with methanol to a molar amount of 0.5 to 2 times. . 2. The method according to claim 1, wherein the azeotropic solvent is an aliphatic or alicyclic hydrocarbon having 6 or 7 carbon atoms. 3. The azeotropic solvent is n-hexane.
Production method described in 1. 4. The concentration of the azeotropic solvent present in the reaction system is set at 0.
The reaction is carried out while maintaining the content at 2 to 20% by weight.
The production method according to any one of the above. 5. The azeotropic solvent is recovered by bringing a mixed solvent of methanol and an azeotropic solvent into contact with water and extracting and removing methanol from an aqueous phase, and reused in the transesterification reaction. 5. The production method according to 4.