JP2001172236A - Method for purifying dimethylaminoethyl acrylate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a purification method obtaining the objective dimethylaminoethyl acrylate by distilling off methyl acrylate and dimethylaminoethanol by continuous distillation from a mixed solution containing at least methyl acrylate, dimethylaminoethanol and dimethylaminoethyl acrylate while suppressing formation of Michael adduct and polymer without using a refrigerant at <=-5 deg.C. SOLUTION: A mixed solution containing at least methyl acrylate, dimethylaminoethanol and dimethylaminoethyl acrylate is continuously supplied to a distillation apparatus equipped with a first and a second distillation columns. Firstly methyl acrylate is distilled off by the first distillation column, a bottom product from the first distillation column is supplied to the second distillation column, dimethylaminoethanol is distilled off from the second distillation column and dimethylaminoethyl acrylate is left in a bottom product from the second distillation column.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing dimethylaminoethyl acrylate, and more particularly to a method for producing methyl dimethyl and dimethyl acrylate from a mixture containing at least methyl acrylate, dimethylaminoethanol and dimethylaminoethyl acrylate. The present invention relates to a method for obtaining dimethylaminoethyl acrylate excluding aminoethanol.

[0002]

2. Description of the Related Art Since dimethylaminoethyl acrylate has an amino group in the molecule, it is used as a dye-improving agent for fibers, an antistatic agent for plastics, and the like. The polymerized polymer is useful as a toner binder, an ultraviolet curing printing material, a coating resin, a polymer coagulant, an ion exchange resin, and the like.

Conventionally, dimethylaminoethyl acrylate has been produced by the following method. That is, first, methyl acrylate and dimethylaminoethanol are subjected to a transesterification reaction in the presence of a transesterification catalyst, and a reaction solution containing unreacted raw materials obtained by this reaction is transferred to a purification step. In this step, unreacted raw materials are distilled off by a batch operation while gradually changing the degree of vacuum, and the catalyst and impurities are further removed to produce the target dimethylaminoethyl acrylate.

[0004] However, under the heating condition in distillation, the production of so-called Michael adducts, in which dimethylaminoethanol as a raw material and methanol produced as a by-product are added to the double bond of methyl acrylate, increases, resulting in a decrease in yield. Further, methyl acrylate and dimethylaminoethyl acrylate have high polymerizability and are heated during distillation, so that a polymer is easily produced. The production of the polymer not only lowers the yield of the target product, but also causes clogging of piping and equipment, making stable operation of the process impossible.

Japanese Patent Application Laid-Open No. 54-163517 discloses that, when dimethylaminoalkyl (meth) acrylate is purified from a reaction solution, not only the temperature of the distillate is suppressed to 100 ° C. or less, but also the heated surface is suppressed to 100 ° C. or less. It describes that the formation of a polymer is thereby suppressed. But in this case,
Not only does the temperature difference between the heating surface and the distillate almost disappear, the heating device becomes excessively large, and the amount of the heating fluid used becomes large, which is not economically preferable.

[0006] In JP-A-11-106369 and JP-A-2-59546, when purifying dimethylaminoethyl acrylate, the degree of reduced pressure is gradually changed by batch operation to recover unreacted raw materials. Generally, distillation by batch operation requires time other than that required for distillation, such as liquid transfer, heating, and liquid removal. When efficiently purifying the target product in large quantities, distillation by continuous operation is preferable. However, in the distillation method by continuous operation, the pressure,
Operating conditions such as temperature are operated at a constant value. Therefore, when distilling unreacted raw materials by a distillation method by a continuous operation, distillation must be performed under a high vacuum in order to avoid polymerization of dimethylaminoethyl acrylate. The dew point of the vapor containing methyl acid was lowered, and an expensive refrigerant of -5 ° C or lower had to be used to completely condense the vapor.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and at least suppresses the formation of Michael adducts and polymers while suppressing at least methyl acrylate, dimethylaminoethanol and From a mixed solution containing dimethylaminoethyl acrylate, methyl acrylate and dimethylaminoethanol are distilled off by continuous distillation without using a refrigerant at −5 ° C. or lower, thereby obtaining a purification method for obtaining the target dimethylaminoethyl acrylate. The purpose is to provide.

[0008]

According to the present invention, a mixed solution containing at least methyl acrylate, dimethylaminoethanol and dimethylaminoethyl acrylate is supplied to a distillation apparatus having a first distillation column and a second distillation column. The mixture is continuously supplied, and firstly, methyl acrylate is mainly distilled off in the first distillation column, and then the bottoms from the first distillation column are discharged in the second distillation column.
Acrylic acid, characterized in that dimethylaminoethanol is mainly distilled off in a second distillation column and dimethylaminoethyl acrylate is left in the bottoms from the second distillation column. The present invention relates to a method for purifying dimethylaminoethyl.

In the present invention, the bottom temperature of each of the first and second distillation columns is preferably 100 ° C. or less, and the top temperature is preferably 0 ° C. or more and 40 ° C. or less.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention can be applied to a mixed solution supplied to a distillation apparatus in the present invention as long as it contains at least methyl acrylate, dimethylaminoethanol and dimethylaminoethyl acrylate. The present invention is particularly preferably used in the step of producing dimethylaminoethyl acrylate by transesterification of methyl acrylate and dimethylaminoethanol.

This transesterification reaction is usually by-produced in the presence of a transesterification catalyst, for example, alcoholates such as alkali metal alcoholates, titanium alcoholates and aluminum alcoholates, organotin compounds, lead compounds and thallium compounds. Methyl acrylate is reacted with dimethylaminoethanol while removing methanol. If this reaction is performed continuously, methyl acrylate is 10 to 10% in the mixed solution after the reaction.
75% by mass, dimethylaminoethanol is 10 to 20% by mass, and dimethylaminoethyl acrylate is 20 to 20% by mass.
About 75% by mass and other catalysts and the like are included. The type of transesterification is not particularly limited, and may be a continuous reaction or a batch reaction. However, since the purification method of the present invention is a continuous treatment, it is extremely efficient to employ a continuous reaction for the transesterification.

The distillation apparatus used in the present invention has a first distillation column and a second distillation column. The first distillation column mainly contains methyl acrylate, and the second distillation column contains dimethylaminoethanol. Distill off. As the type of the distillation column, a known type can be used. For example, a plate type or a packed column type may be used. The number of distillation columns used depends on the type used, but it is sufficient if there are approximately 3 to 30 stages.

In any of the distillation columns, the distillation is usually carried out under reduced pressure, and preferably, the pressure at the top of the distillation column is 13 kP.
It is desirable to operate under a. In order to avoid the use of expensive refrigerants, it is preferable that the top temperature is high, and in order to avoid polymerization at the bottom, the bottom temperature is preferably low. .9 kPa,
In the second distillation column, the pressure is preferably set to 0.6 to 6.5 kPa.

The temperature at the bottom of each distillation column is determined by the boiling point of the bottoms at that pressure. In both distillation columns, polymerization of alkyl acrylate and dimethylaminoethyl acrylate and by-products such as Michael adducts occur. In order to suppress a decrease in the yield due to an increase in the production amount of the product, the temperature is preferably set to 100 ° C. or lower, particularly 90 ° C.
C. or less is preferred.

[0015] The temperature at the top of the column is 100
Although it is determined by the degree of reduced pressure and the composition of the distillate necessary for the temperature to be lower than or equal to 0 ° C. or lower, in the present invention, by using two units of the first distillation column and the second distillation column, it is possible to obtain a relatively high degree. It can be set, and usually needs to be 0 ° C to 40 ° C, preferably 5 to 40 ° C. This makes it possible to easily and completely condense the vapor from the top of the column, particularly the vapor containing methyl acrylate in the first distillation column, without using a refrigerant at -5 ° C or lower.

In the present invention, the mixture is first supplied to a first distillation column to mainly remove methyl acrylate. However, if only methyl acrylate is distilled off, the tower top temperature may be too low. In such a case, conditions including dimethylaminoethanol or dimethylaminoethyl acrylate may be employed.

Further, even if some methyl acrylate remains in the bottoms from the first distillation column, it can be removed by the operation of the second distillation column. The content of methyl acrylate in the discharged liquid is 4% by mass or less, preferably 2% by mass or less.

Next, the bottom product from the first distillation column is continuously supplied to the second distillation column, and dimethylaminoethanol is mainly distilled off in the second distillation column. That is, in consideration of the respective gas-liquid equilibria of dimethylaminoethanol and dimethylaminoethyl acrylate, the second distillation is carried out under the condition that dimethylaminoethanol can be distilled off and the target product dimethylaminoethyl acrylate is not distilled off. The column is operated, thereby effectively removing dimethylaminoethanol. As long as the purpose is met, a very small amount of dimethylaminoethyl acrylate may be actually distilled off, and the remaining methyl acrylate can be further removed.

The content of methyl acrylate in the bottoms from the second distillation column is 1% by mass or less, preferably 0.1% by mass.
1% by mass or less, dimethylaminoethanol content is 5%
% By mass or less, preferably 2% by mass or less.

In the present invention, a polymerization inhibitor is added to the distillation column during the distillation to prevent polymerization of methyl acrylate and dimethylaminoethyl acrylate, for example, from the top of the distillation column or the top of the condenser. be able to. Examples of commonly used polymerization inhibitors include, for example, phenothiazine, hydroquinone monomethyl ether, and the like. The addition amount of the polymerization inhibitor is an amount sufficient to sufficiently exhibit the effect of inhibiting the polymerization, and the effect when the amount is too large, such as a problem of separation of the polymerization inhibitor from the target product dimethylaminoethyl acrylate, It is preferable to select the obtained dimethylaminoethyl acrylate within a range that does not have an adverse effect such as polymerization inhibition when used as a raw material monomer of the polymer.
It is preferable to use it in the range of 2% by mass.

Oxygen or a mixture of oxygen and an inert gas, such as air, a mixed gas of oxygen and argon, etc., may be introduced from the lower part of the distillation column or the like, and may be used for the polymerization of methyl acrylate or dimethylaminoethyl acrylate. The suppression effect can be further improved.

[0022]

The present invention will be described in more detail with reference to the following examples. In Examples and Comparative Examples, analysis of the liquid was performed by gas chromatography.

Reference Example 1 Dimethylaminoethanol and methyl acrylate were charged as raw materials into a 6-liter glass flask equipped with a distillation tower, a stirring blade, and a thermometer, and dibutyltin oxide was used as a catalyst. Was subjected to a transesterification reaction. The composition of the resulting reaction solution excluding the catalyst was methanol 0.2% by mass, methyl acrylate 45.
4% by mass, 4.8% by mass of dimethylaminoethanol, and 49.6% by mass of dimethylaminoethyl acrylate.

Embodiment 1 FIG. 1 is a view schematically showing an apparatus used in the embodiment. The apparatus shown in FIG. 1 includes a first distillation column (1), a second distillation column (6), and a single distillation still (8). Then, a reaction solution containing methyl acrylate, dimethylaminoethanol and methylaminoethyl acrylate is supplied to a first distillation column (hereinafter, referred to as a methyl acrylate recovery column), and methyl acrylate is distilled from the top of the column. Then, the obtained bottoms are supplied to a second distillation column (hereinafter, referred to as an alcohol recovery column), dimethylaminoethanol is distilled from the top of the column, and the obtained bottoms are transferred to a simple distillation pot (8). By feeding and removing the catalyst, dimethylaminoethyl acrylate can be obtained.

The methyl acrylate recovery column (first distillation column (1)) includes a heater (2a), a condenser (3a), a liquid distributor (4a), and a vacuum generator (5a).
In the heater (2a), the liquid drawn from the bottom of the tower is heated,
A part is sent to the alcohol recovery column (second distillation column (6)) as bottoms, and the rest is returned to the bottom. Condenser (3
a) is cooled by the refrigerant to condense the vapor from the top into liquid and send the liquid to the liquid distributor (4a). In the liquid distributor (4a), a part is extracted according to a predetermined reflux ratio, and the rest is returned to the distillation column. The vacuum generator (5a) is used to bring the inside of the system into a predetermined reduced pressure state.

In Example 1, a 6-stage glass-made Oldershaw distillation column (hereinafter, methyl acrylate recovery column) was used as the methyl acrylate recovery column, and the reaction solution obtained in Reference Example 1 was poured from the bottom of the column. At the third stage, 830 g / h was fed, and at this time, the distillation ratio was 0.5, the column top pressure was 5.5 kPa, the column top temperature was 10.6 ° C, and the column bottom temperature was 81.3 ° C. The column was operated to distill off methyl acrylate, and 0.8% by mass of methyl acrylate, 7.2% by mass of dimethylaminoethanol, and 92.0% by mass of dimethylaminoethyl acrylate
And continuously sent to an alcohol recovery tower.

On the other hand, the alcohol recovery column (second distillation column (6)) includes a heater (2b), a condenser (3b), a liquid distributor (4b), and a vacuum generator (5b).
Each function is the same as in the case of the methyl acrylate recovery tower.

Using a 15-stage glass-made Oldershaw distillation column as the alcohol recovery column, the bottoms continuously fed from the methyl acrylate recovery column were fed to the eighth column from the bottom of the column at 434 g / h. Feed, reflux ratio 6 and top pressure 1.
3 kPa, top temperature 31.0 ° C, bottom temperature 80.3
The dimethylaminoethanol was distilled off by operating the distillation column under the condition of ° C. The obtained bottoms were 0.2% by mass of dimethylaminoethanol and 99.8% by mass of dimethylaminoethyl acrylate. The bottom liquid obtained from the bottom of the column was continuously sent to the simple distillation still (8).

The single distillation still (8) is provided with a stirrer (7), a condenser (3c) and a vacuum generator (not shown).
Continuous simple distillation was performed under a reduced pressure of 1.3 kPa to distill out the target dimethylaminoethyl acrylate to remove dibutyltin oxide.
99.8% by mass of dimethylaminoethyl acrylate containing 2% by mass was obtained at 346 g / h.

In order to prevent polymerization, a dimethylethyl acrylate solution in which 10% by mass of phenothiazine was dissolved was charged at a rate of 1 g / h from the top of the condenser from both the tops of the methyl acrylate recovery tower and the alcohol recovery tower. Then, air was supplied from the column bottom at a rate of 60 ml / h.

Although the refrigerant used was at 0 ° C., all the vapor from the top of the distillation column was condensed, and no formation of a polymer or Michael adduct was confirmed.

Comparative Example 1 As shown in FIG. 2, the distillation apparatus used in Comparative Example 1 had one distillation column (hereinafter referred to as a low-boiling recovery column) (9) and a simple distillation pot (18). ). The low-boiling recovery tower (9) includes a heater (12) and a condenser (1).
3a), liquid distributor (14) and vacuum generator (15)
And the simple still (18) comprises a stirrer (17),
It has a condenser (13b) and a vacuum generator (not shown), and the operation of each device is the same as that of the distillation device shown in FIG.

Using a 10-stage Oldshaw distillation column as a low-boiling recovery column, the reaction solution obtained in Reference Example 1 was supplied to the fourth column from the top at 430 g / h, and the temperature at the bottom of the column was measured. Is 8
The pressure at the top was adjusted to 1.3 kPa so as to be 0 ° C.,
Methyl acrylate and dimethylaminoethanol were distilled off. From the top of the low-boiling recovery tower, 1 g of a dimethylethyl acrylate solution in which 10% by mass of phenothiazine was dissolved.
/ H from the top of the condenser and 60 ml of air from the bottom
/ H.

Although the refrigerant used was at 0 ° C., the temperature at the top of the column was −11.7 ° C., most of the vapor was not condensed in the condenser, and the distillation operation was stopped.

[Comparative Example 2] A low-boiling recovery column similar to that in Comparative Example 1 was used, and the reaction solution obtained in Reference Example 1 was supplied to the fourth stage from the top of the column at 430 g / h. Temperature is 120 ° C
The pressure at the top of the column was adjusted to 16.8 kPa, and methyl acrylate and dimethylaminoethanol were distilled off. From the top of the low-boiling recovery tower, a dimethylethyl acrylate solution in which 10% by mass of phenothiazine was dissolved was 1 g /
h from the top of the condenser and air from the bottom of the column at 60 ml /
h.

At this time, the temperature at the top of the tower was 35.9 ° C.
Most of the vapor was condensed in the condenser. Dibutyltin oxide was removed from the bottom product obtained by simple distillation under a reduced pressure of 1.3 kPa to obtain 98.8% by mass of dimethylaminoethyl acrylate at 172 g / h.

However, after the end of the experiment, a polymer was confirmed inside the heating device.

[0038]

According to the present invention, while suppressing the formation of Michael adducts and polymers, a mixed solution containing at least methyl acrylate, dimethylaminoethanol and dimethylaminoethyl acrylate can be cooled at -5 ° C or lower. Without using, methyl acrylate and dimethylaminoethanol can be distilled off by continuous distillation to provide a purification method for obtaining the target dimethylaminoethyl acrylate.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a distillation apparatus used in Examples.

FIG. 2 is a diagram schematically showing a distillation apparatus used in a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Methyl acrylate recovery tower 2a, 2b Heater 3a, 3b, 3c Condenser 4a, 4b Liquid distributor 5a, 5b Vacuum generator 6 Alcohol recovery tower 7 Stirrer 8 Single distillation still 9 Low-boiling recovery tower 12 Heater 13a 13b Condenser 14 Liquid distributor 15 Vacuum generator 17 Stirrer 18 Simple distillation still

Continued on the front page (72) Akira Ogawa, Inventor 20-1 Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Co., Ltd. Central Research Laboratory (72) Inventor Yoshihide Nagabuchi 20-1 Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Central Technology Research Institute Co., Ltd. (72) Inventor Wataru Hatano 20-1 Miyukicho, Otake City, Hiroshima Prefecture Mitsubishi Rayon Co., Ltd. Central Technology Research Center F term (reference) 4H006 AA02 AD11 BC50 BD60

Claims (3)

[Claims] 1. A mixed solution containing at least methyl acrylate, dimethylaminoethanol and dimethylaminoethyl acrylate is continuously supplied to a distillation apparatus provided with a first distillation column and a second distillation column. After distilling off mainly methyl acrylate in the first distillation column, the bottoms from the first distillation column are supplied to the second distillation column, and dimethylaminoethanol is mainly distilled in the second distillation column. A method for purifying dimethylaminoethyl acrylate, wherein dimethylaminoethyl acrylate is left in the bottoms from the second distillation column. 2. The temperature of each of the first and second distillation columns is set to 100 ° C. or lower, and the top temperature is set to 0 ° C.
The method for purifying dimethylaminoethyl acrylate according to claim 1, wherein the temperature is set to 40 ° C or lower. 3. The dimethyl acrylate according to claim 1, wherein the mixed solution is a reaction solution obtained when a transesterification reaction of methyl acrylate and dimethylaminoethanol is performed to produce dimethylaminoethyl acrylate. A method for purifying aminoethyl.