JPH0713050B2 - Method for producing dimethylaminoethyl acrylate - Google Patents

Description

Detailed Description of the Invention a. OBJECT OF THE INVENTION [Industrial field of use] The present invention uses tetra-n-butyl titanate (hereinafter abbreviated as TBT) as a catalyst and n-butyl acrylate (hereinafter abbreviated as BA) and dimethylaminoethyl alcohol (hereinafter DM.
The present invention relates to a method for producing high-purity dimethylaminoethyl acrylate (hereinafter abbreviated as DA) by a transesterification reaction with AE) and reuse of a catalyst.

Dialkylamino (meth) acrylates such as DA, dimethylaminoethylmethacrylate, diethylaminoethylmethacrylate, etc. can be used as they are or with an amino group of 3
The quaternary or quaternary ammonium salt is used as a dyeing property improver for fibers, an antistatic agent for plastics, a pigment dispersant in paints, an ultraviolet curing aid, and further by homopolymerization or copolymerization with other unsaturated compounds. The resulting polymer is a fiber treatment agent, a toner binder, a paint, a lubricant additive,
It is used as a paper-strengthening agent, an adhesive, an ion exchange resin, a polymer coagulant, and the like, and is used in a wide range of fields. Therefore, the present invention can be effectively utilized in the field of using those drugs.

[Prior Art] A method for producing a dialkylaminoalkyl acrylate by transesterification of an alkyl acrylate and a dialkylaminoalkyl alcohol is already known, and as a catalyst, a tin compound such as an alkali metal alcoholate, magnesium alcoholate, tita alcoholate, or dibutyltin oxide, or It is known to use acetylacetone metal complex compounds such as acetylacetone.

Purification of the obtained dialkylaminoalkyl acrylate is generally carried out by a distillation operation, and as the atmosphere at that time, air or a 5% ON (oxygen / nitrogen) atmosphere is widely adopted.

Further, as a purification method particularly intended for high purification, a method of treating with activated carbon (JP-A-63-79858), a method of treating with zeolite (JP-A-63-230714) and the like are known. There is.

[Problems to be Solved by the Invention]

However, when an alkali metal alcoholate such as sodium methylate is used as a catalyst in the synthesis of DA, the raw material dialkylaminoalkyl alcohol or the alcohol by-produced in the reaction is used as the raw material alkyl acrylate or the target dialkylaminoalkyl acrylate.
The reaction of addition to the heavy bond portion is likely to occur, and the yield and purity of the target dialkylaminoalkyl acrylate are significantly reduced. Further, since the catalyst reacts with a small amount of water in the reaction system to be deactivated, it requires an operation such as sufficient dehydration in advance, and even if such an operation is performed, the catalyst is deactivated with time. Therefore, it is necessary to continuously add the catalyst to the reaction system.

In the case of magnesium alcoholate as well as in the case of alkali metal alcoholate, the above-mentioned addition reaction is likely to occur and the yield of DA is significantly reduced.

When a tin compound such as dibutyltin oxide is used as a catalyst, its catalytic activity is lower than that of an alkali metal alcoholate, so that there is a problem that a large amount of catalyst is required or the reaction time must be lengthened. is doing.

When titanium alcoholate is used as a catalyst, the catalyst is deactivated due to the influence of a small amount of water in the reaction system, and the cause is unknown, but like the alkali metal alcoholate, deactivation over time is also observed.

In particular, in the industrial production method, it is extremely difficult to avoid the inclusion of a trace amount of water, so the catalyst deactivation is unavoidable to some extent, and there is a problem that a large amount of catalyst must be used.

Further, titanium alcoholate has a lower catalytic activity than that of alkali metal alcoholate, and also in this respect, there is a problem that a large amount of catalyst is required or the reaction time must be lengthened.

Conventionally, the reaction solution obtained by using titanium alcoholate as a catalyst is purified by distillation as it is, but a trace amount of DMAE
However, high-purity DA could not be obtained. Further, the catalyst in the bottom of the rectification bottom hardly shows any catalytic activity, and even if some activity is recognized, the fact that the bottom residue viscosity is considerably high does not recover the catalyst.

Although some of the acetylacetone metal compounds have been proposed as catalysts, they have the drawbacks of low catalytic activity, requiring a long reaction time, and accelerating the polymerization of DA and the like depending on the metal used. Further, the acetylacetone-based complex is expensive and is not suitable industrially.

When DA is used as a tertiary or quaternary salt for polymerization, if the raw material acrylate, DMAE or other by-products are contained in DA, it may cause deterioration of the physical properties of the resulting polymer. It is desired that the DA used has a high purity with less impurities. In particular, when the polymer is used as a coagulant for various kinds of waste water, its molecular weight is required to have a high molecular weight of several millions, so that the raw material DA needs to be of higher purity.

As described above, the purification of DA has conventionally been carried out by distillation, but it was impossible to improve the purity of the product DA by producing a low boiling point due to decomposition of by-products due to high temperature during distillation. . Furthermore, the acrylate that is the raw material and the target dimethylaminoethyl acrylate are much more easily polymerized than the methacrylate, and it is not possible to use air or 5
In vacuum distillation in% ON atmosphere, polymerization in the distillation column, condenser, especially in the distillation column kettle and heater is vigorous, so
Means such as adding a large amount of polymerization inhibitor to the kettle liquid have been adopted, but they are not completely satisfactory.

B. Structure of the Invention [Means for Solving the Problems] In order to find a method for producing dimethylaminoethyl acrylate that does not have the above-mentioned problems, the present inventors have used titanium alcoholate as a catalyst and various alkyl acrylates and DMAE.
As a result of diligently studying the transesterification reaction with, as titanium alcoholate, as alkyl acrylate and DMAE
When n-butanol produced as a by-product is distilled off from the reaction solution under reduced pressure, preferably in the absence of oxygen, the reaction proceeds,
In a usual amount of catalyst, DA can be obtained in a very high reaction yield of 85% or more in the reaction for 4 to 5 hours without losing the catalytic activity without performing dehydration operation before the reaction, In addition, the reaction solution obtained is recovered by removing the catalyst by distillation in the absence of oxygen, and the distillate containing DA is purified by distillation again in the absence of oxygen (hereinafter abbreviated as high boiling distillation method), It is possible to obtain high-purity DA, and the bottoms containing the recovered catalyst have sufficient catalytic activity even if they are reused in the reaction without any treatment such as purification, and can be reused several times or more. Heading out, the present invention has been completed.

That is, in the present invention, a reaction liquid of n-butyl acrylate and dimethylaminoethyl alcohol, which is reacted by distilling off by-produced n-butanol under reduced pressure using tetra-n-butyl titanate as a catalyst, is used to substantially eliminate oxygen. The present invention relates to a method for producing dimethylaminoethyl acrylate, which comprises first recovering tetra-n-butyl titanate by distillation in the presence and then purifying it.

The present inventors applied for a patent first (Japanese Patent Application No. 1-049987)
High-purity DA can also be obtained by a method in which the reaction solution obtained according to the method is directly distilled in a nitrogen atmosphere, but according to the present invention, the demand for higher quality DA in recent years is satisfied, and resource saving and cost reduction are achieved. A method that greatly contributes to

The reaction molar ratio of BA and DMAE in the production method of the present invention is 1.0
˜10.0 is preferable, and 1.1 to 5.0 is more preferable. When the molar ratio exceeds 10.0, a large reactor is required, and a large amount of energy is required for recycling excess BA, which is desirable to avoid. The TBT used in the present invention may be a commercially available product as it is. The amount of TBT used is preferably 0.1 to 10 mol% and more preferably 0.5 to 5 mol% with respect to the starting material DMAE. As the charging method of TBT, either a charging method at a time or a continuous charging method or a dividing charging method can be adopted, but the charging method at the time of charging the raw materials is advantageous and preferable.

The reaction solvent does not usually need to be used, but it is also possible to use xylene, toluene, hexane or the like as an azeotropic solvent for the by-product n-butanol.

The reaction temperature is affected by the composition of the raw materials used, but is determined by the degree of vacuum.

The reaction temperature preferred in the present invention is 60 to 150 ° C, more preferably 9
The temperature is 0 to 120 ° C., and this temperature is adjusted by adjusting the degree of pressure reduction. The corresponding degree of vacuum is 200-500 Torr.

The reaction time is usually 4 to 5 hours, though it depends on the reaction temperature, the amount of catalyst and the like.

In the present invention, it is preferable to add a polymerization inhibitor to the reaction system for the purpose of suppressing the thermal polymerization plan during the reaction. The polymerization inhibitor used in this case may be a known one such as hydroquinone monomethyl ether or phenothiazine, and one or more of these may be used. These polymerization inhibitors are preferably 0.01 to 2w with respect to the total amount charged.
t%, more preferably 0.05 to 1 wt% is used.

After completion of the reaction, unreacted BA, DMAE, by-product n-butanol, and target compound under reduced pressure in the reaction solution in the absence of oxygen.
Highly pure DA can be obtained by distilling DA and the like and removing the catalyst TBT, then again adding a polymerization inhibitor to the distillate and distilling in the absence of oxygen by a conventional method. The recovered catalyst can be used as it is for repeated reaction without any purification, but the viscosity tends to increase slightly as the number of repetitions increases, so it was recovered from the viewpoint of stability in industrial production. It is preferable to extract a part of the catalyst and add a new catalyst for use.

In the conventional distillation in the presence of oxygen, DA is extremely likely to be colored and polymerization is also likely to occur, and this tendency becomes more remarkable when the temperature is high, and such a method is difficult to adopt.

When removing the catalyst by distillation, it is possible to completely distill off the volatile components because there are almost no high-boiling impurities.
90-95% of the reaction completed solution considering handling during reuse
Is preferably distilled. DA when the distillation rate is reduced
It is desirable to avoid it because it lowers the productivity.

The polymerization inhibitor added at the time of the redistillation may be a known one, for example, hydroquinone, hydroquinomonomethyl ether, phenothiazine, etc., and one or more of them may be used. These polymerization inhibitors are preferably 0.01 to 2 wt% with respect to the total amount charged, more preferably 0.05
Used in the range of ~ 1wt%.

The catalyst removal and DA purification steps are preferably performed at 130 ° C. or lower from the viewpoint of suppressing the thermal polymerization reaction. It is possible to use a heat medium such as silicone oil for suppressing polymerization, but the problem of polymerization does not occur even if it is not particularly used.

Since the distillate distilled in the reaction step of the present invention contains only n-butanol and a small amount of BA, the distillate containing n-butanol as a main component is directly reacted with acrylic acid, for example. If you do, you can easily get BA, and this BA
It is also one of the features of the present invention that it can be recycled as a raw material of the present invention, and by-product alcohol can be effectively used.

[Action]

Conventionally, using a TBT catalyst under a reduced pressure, BA and DMAE are transesterified to distill off n-butanol as a by-product.
No technique for obtaining DA has been reported, and it is unclear why the present invention having these contents provides DA with high selectivity and high yield, and further shows that the catalyst can be reused. However, conventional TBT catalysts known in U.S. Pat.No. 2,822,348 and the like have been pointed out to have drawbacks such as long-term deactivation due to deactivation over time, deactivation by a small amount of water, and low activity, as described above. Considering the present situation where these problem-free catalysts are being studied, the action in the present invention is completely unpredictable.

For example, in the method for producing DA in which methyl acrylate (hereinafter abbreviated as MA) is used as the alkyl acrylate and the by-product methanol is azeotropically distilled with MA under atmospheric pressure, the reaction rate is extremely high even when the TBT catalyst is used in the same manner as in the present invention. The yield of DA is about 30% even if the reaction is allowed to proceed for 6 hours.

In addition, when ethyl acrylate (hereinafter abbreviated as EA) is used as the alkyl acrylate and reacted in the same manner,
The DA yield is about 70% after 7 hours of reaction, and the DA selectivity is also high.
85-95%.

When the reaction is carried out while distilling off the by-product n-butanol under atmospheric pressure without maintaining the reduced pressure state using BA (hereinafter abbreviated as atmospheric pressure method), the cause is unknown, but the reaction solution is The fact that it becomes cloudy and the reaction rate becomes extremely slow and TBT is inactivated over time is observed. Similar to the depressurization method, the atmospheric method also requires selective extraction of n-butanol as a by-product, but the reaction temperature must be 130 to 150 ° C. in order to selectively and efficiently extract butanol in the atmospheric method. As a result, polymerization of BA and DA occurs, and the yield of DA is reduced, and no excellent action in the present invention is found in the atmospheric method at any point.

Furthermore, in the present invention, as described above, the action of the present invention is exhibited without using a reaction solvent, and the process without using a reaction solvent is extremely simple, and the present invention is industrially more effectively utilized. .

The most remarkable effect of the present invention is that highly pure DA can be obtained by an industrially versatile and advantageous distillation operation and that the catalyst can be reused.

According to the study by the present inventors, when the reaction solution obtained according to the method of the present invention is distilled without removing the catalyst (hereinafter abbreviated as direct distillation method), the distillate DA is obtained even under the condition that the rectification effect is large. While low-boiling components of 0.3 to 0.5% are found in the product, low-boiling components such as DMAE can be easily removed by distillation in the absence of the catalyst TBT by the above-described deboiling distillation method.
It was found that DA with a high purity of 99.9% or more can be obtained. The details of obtaining such an action are also unknown.

In addition, the catalyst can be reused as it is without treating the distillation bottom containing the catalyst such as purification, and according to the method of the present invention, the catalyst can be reused several times or more without adding a new catalyst. Is possible. On the other hand, in the bottoms obtained by the direct distillation method, the catalytic activity is low, and the action as seen in the deboiling distillation method is not recognized.

According to the present invention, the catalyst is hardly deactivated even in the synthesis step, and it is possible to maintain the catalytic activity even in the distillation step.

The action in the present invention is completely unpredictable from the phenomenon of catalyst deactivation over time, which was conventionally considered inevitable in TBT.

The recovered catalyst can be used as it is.
The rectification residue in the DA purification step does not show a phenomenon such as an increase in viscosity due to polymerization, and can be recycled as a rectification raw material, so that the yield of DA is reduced even when the catalyst of the present invention is removed. There is no such disadvantage.

〔Example〕

Hereinafter, in order to describe the present invention more specifically, examples and comparative examples will be described in detail. The definitions of conversion rate, selectivity and yield used in the present specification are as follows.

Overall yield (%) = Yield (%) x Distillation yield (%) / 100 Example 1. BA1 in a three-necked flask equipped with a stirrer, a thermometer, a condenser and a fractionation column and equipped with a rectification column. , 920g (15.0mol), DMAE445g
(5.0 mol), TBT 34.1 g (0.1 mol) and phenothiazine 2.4 g (1,000 ppm) as a polymerization inhibitor were added, and heating was started under reduced pressure of 300 Torr with stirring. After totally refluxing for 30 minutes, the reaction liquid temperature is 110 to 120 ° C, and the rectification tower overhead temperature is 96 to
The n-butanol produced by maintaining at 98 ° C has a reflux ratio of 3.0-
The reaction was performed for 4 hours while extracting at 5.0.

When the reaction solution was analyzed by gas chromatography, DM
The reaction rate of AE was 92% and the yield of DA was 90%.

Next, this reaction solution is placed in a nitrogen atmosphere at 30 Torr and 90 to 100 ° C.
The catalyst was removed with to obtain 1,944 g of a distillate containing DA. Furthermore, after adding 1.9 g of phenothiazine to the distillate, a condenser,
Using a rectification column (15 theoretical plates) equipped with a fractionation column, after distilling off n-butanol, BA, and DMAE under a nitrogen atmosphere at 20 Torr, 70 to 85 ° C., and a reflux ratio of 1.0 to 10.0, the same nitrogen was used. Under the atmosphere,
Distilled at 20 Torr, 85 to 95 ° C., and a reflux ratio of 1.0 to 2.0 to obtain DA611g. The overall yield of DA was 86% and the purity was 99.9%.

Comparative Example 1. MA1,290 g (15.0 mol), DMAE44 in the same apparatus as in Example 1.
5 g (5.0 mol), TBT 34.1 g (0.1 mol) and phenothiazine 1.8 g (1,000 ppm) as a polymerization inhibitor were added, and heating was started while stirring. The resulting azeotropic mixture of methanol and MA was completely refluxed for 30 minutes, and then the rectification column overhead temperature was further adjusted to 60
Keeping the temperature at ~ 65 ° C and drawing the azeotrope out of the system 6
Reacted for hours. As a result of analyzing the reaction liquid by gas chromatography, the yield of DA was 28%.

Comparative Example 2. The same operation as in Example 1 was carried out and the reaction was carried out for 4 hours.

When the reaction solution was analyzed by gas chromatography, the conversion rate of DMAE was 92% and the yield of DA was 91%.

Next, using a rectification column (theoretical plate 15) equipped with a condenser and a fractionation column, under a nitrogen atmosphere, 20 Torr, 70 to 85 °, a reflux ratio of 1.0 to 30.
After n-butanol, BA and DMAE were distilled off at 0, they were also distilled under a nitrogen atmosphere at 20 Torr, 85 to 95 ° C and a reflux ratio of 1.0 to 2.0 to obtain DA586g. Total yield of DA is 86%, purity is 99.6%
Met.

Example 2. The same operation as in Example 1 was performed and the reaction was carried out for 4 hours.

When the reaction solution was analyzed by gas chromatography, DM
The reaction rate of AE was 91% and the yield of DA was 90%.

The catalyst was removed from this reaction solution under a nitrogen atmosphere at 30 Torr and 90 to 100 ° C. to obtain 20,121 g of a distillate containing DA. 106 g of the catalyst recovered in Example 1 and BA1,920 g in the same apparatus as in Example 1.
(15.0 mol) and DMAE445g (5.0 mol) were added, and heating was started under reduced pressure of 300 Torr with stirring. The reaction solution temperature is 110
˜120 ° C., while maintaining the overhead temperature of the rectification column at 96 to 98 ° C., while extracting n-butanol produced at a reflux ratio of 3.0 to 5.0, 4
A time reaction was performed.

When the reaction solution was analyzed by gas chromatography, DM
The reaction rate of AE was 90% and the yield of DA was 89%. The following table shows the results of carrying out the reaction a total of four times in the same manner.

As is clear from the table, no decrease in the activity of the catalyst was observed even after repeated use of the recovered catalyst. Furthermore, accumulation of high boiling impurities was not observed.

C. EFFECTS OF THE INVENTION According to the present invention, dimethylaminoethyl acrylate can be produced with high purity, high yield and low cost, and a very suitable raw material for producing a polymer flocculant, a fiber treating agent, etc. is supplied. And the effect of contributing to the industry using them is enormous.

Claims (1)

[Claims] 1. A reaction liquid of n-butyl acrylate and dimethylaminoethyl alcohol, which is reacted with tetra-n-butyl titanate as a catalyst while distilling off by-product n-butanol under reduced pressure, and a reaction liquid containing substantially no oxygen. A method for producing dimethylaminoethyl acrylate, characterized in that tetra-n-butyl titanate is first recovered by distillation in the presence and then purified.