JPH03112949A - Production of dimethylaminoethyl acrylate - Google Patents

Abstract

PURPOSE:To obtain the objective compound by reacting n-butyl acrylate with dimethylaminoethyl alcohol in the presence of n-butyl titanate as a catalyst while distilling out by-produced n-butanol under reduced pressure and distilling the reaction liquid in the absence of oxygen. CONSTITUTION:The subject substance having extremely high purity can be produced by reacting n-butyl acrylate with dimethylaminoethyl alcohol in the presence of tetra-n-butyl titanate as a catalyst while distilling out by-produced n-butanol under reduced pressure, distilling the reaction liquid in the absence of oxygen to remove and recover the catalyst and distilling the distillate again in the absence of oxygen. The inactivation of the catalyst can be prevented at normal amount of catalyst even without dehydrating the catalyst before reaction and the objective compound can be produced in extremely high reaction yield (>=85%) by the reaction for 4-5hr. The subject substance is useful as a dyeability-improving agent, textile-treating agent, raw material for polymer flocculant, etc.

Description

Detailed Description of the Invention A.8 Objective of the Invention [Industrial Application Field] The present invention is directed to the production of n-butyl acrylate (hereinafter referred to as B
The present invention relates to a method for producing high-purity dimethylaminoethyl acrylate (hereinafter referred to as DA) through a transesterification reaction between dimethylaminoethyl alcohol (hereinafter referred to as DMAE) and reuse of the catalyst.

Dialkylamino (meth)acrylates such as DA, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, etc. can be used as is or with an amino group
Grade or quaternary ammonium salts can be used as dyeability improvers for fibers, antistatic agents for plastics, pigment dispersants in paints, and ultraviolet curing aids, as well as by homopolymerization or copolymerization with other unsaturated compounds. The resulting polymers can be used as fiber treatment agents, toner binders, paints, lubricating oil additives,
It is used in a wide range of fields, including paper strength enhancers, adhesives, ion exchange resins, and polymer flocculants. Therefore, the present invention can be effectively utilized in fields where such drugs are used.

[Conventional technology]

A method for producing dialkylaminoalkyl acrylate by transesterification reaction between an alkyl acrylate and a dialkylaminoalkyl alcohol is already known. It is known to use acetylacetone metal complex compounds and the like.

The obtained dialkylaminoalkyl acrylate is generally purified by a distillation operation, and the atmosphere at that time is generally air or a 5% ON (oxygen/nitrogen) atmosphere.

In addition, as purification methods particularly intended for high purity, there are known methods such as treatment with activated carbon (Japanese Unexamined Patent Publication No. 63-79858) and treatment with zeolite (Japanese Unexamined Patent Publication No. 63-230714). There is.

[Problem to be solved by the invention]

However, when an alkali metal alcoholade such as sodium methylate is used as a catalyst in the synthesis of DA, the dialkylaminoalkyl alcohol as a raw material and the alcohol by-produced in the reaction become double molecule of the raw material alkyl acrylate and the target substance dialkylaminoalkyl acrylate. Addition reactions to the bonding moiety are likely to occur, significantly reducing the yield and purity of the target dialkylaminoalkyl acrylate. In addition, since the catalyst reacts with trace amounts of moisture in the reaction system and deactivates, operations such as sufficient dehydration are required in advance, and even if such operations are performed, the catalyst will deactivate over time. Therefore, it is necessary to continuously add a catalyst to the reaction system.

In the case of magnesium alcoholade, as in the case of alkali metal alcoholade, the above-mentioned addition reaction is likely to occur, which significantly reduces the yield of DA.

When a tin compound such as dibutyltin oxide is used as a catalyst, its catalytic activity is lower than that of an alkali metal alcoholide, so there are problems in that a large amount of catalyst is required or the reaction time has to be lengthened. are doing.

Even when titanium alcoholade is used as a catalyst, the catalyst deactivates due to the influence of trace amounts of moisture in the reaction system.Although the cause is unknown, deactivation over time is also observed as with alkali metal alcoholades.

In particular, in industrial production methods, it is extremely difficult to avoid contamination with trace amounts of water, so some degree of catalyst deactivation is unavoidable, and a large amount of catalyst must be used.

In addition, titanium alcoholado is alkali metal alcohola-1
The catalytic activity is lower than that of ., and in this respect also there are problems in that a large amount of catalyst is required or the reaction time has to be lengthened.

Conventionally, the reaction solution obtained using titanium alcoholado as a catalyst is directly purified by distillation, but a trace amount of DM is
Highly pure DA could not be obtained due to contamination with AE and the like. In addition, the catalyst in the residue of the rectifier has almost no catalytic activity, and even if some activity is observed, the viscosity of the residue in the rectifier is quite high, so the catalyst is not recovered.

Although some acetylacetone metal compounds have been proposed as catalysts, they have the disadvantage that they have low catalytic activity and require a long time for reaction, and that depending on the metal used, they may accelerate the polymerization of DA and the like.

Furthermore, acetylacetone complexes are expensive and therefore unsuitable for industrial use.

When polymerizing DA as it is or as a tertiary or quaternary salt, raw materials such as acrylate and DM are added to DA.
If AE and other by-products are contained, it will cause a decrease in the physical properties of the produced polymer, so the DA used
Therefore, it is desired to have high purity with fewer impurities.

In particular, when the polymer is used as a flocculant for various wastewaters, the molecular weight is required to be as high as several hundred blades, so the raw material DA needs to be of higher purity.

As mentioned above, DA has conventionally been purified by distillation, but low-boiling components are generated due to the decomposition of by-products due to the high temperature during distillation, making it impossible to improve the purity of the product DA. . Furthermore, the raw material acrylate and the target dimethylaminoethyl acrylate are extremely easy to polymerize compared to methacrylate, and in the conventional vacuum distillation in air or 5% ON atmosphere, the acrylate is polymerized in the distillation column, the condenser, and especially in the distillation column. Because the polymerization in the pot and heater is intense, measures such as adding a large amount of polymerization inhibitor to the pot solution have been adopted, but these are by no means satisfactory.

1. Structure of the Invention [Means for Solving the Problem] The present inventors aimed to find a method for producing dimethylaminoethyl acrylate free from the above-mentioned problems, using titanium alcoholade as a catalyst and various alkyl acrylates and DM.
As a result of intensive studies on the transesterification reaction with AE, we used tetra-n-butyl titanate (hereinafter abbreviated as TBT) as the titanium alcoholade, n-butyl acrylate (hereinafter abbreviated as BA) and DMAE as the alkyl acrylate, and the by-produced n- If the reaction proceeds while distilling butanol from the reaction solution under reduced pressure, preferably in the absence of oxygen, the catalyst activity will not be lost at a normal catalyst amount without dehydration before the reaction. DA can be obtained with an extremely high reaction yield of 85% or more in a reaction of 4 to 5 hours, and the catalyst is removed and recovered by distillation of the reaction solution obtained in the absence of oxygen, and a distillate containing DA is obtained. By repeating distillation and purification in the absence of oxygen (hereinafter abbreviated as de-high-boiling distillation method), extremely high purity DA can be obtained, and the recovered can residue containing the catalyst can be purified in any way. The present inventors discovered that sufficient catalytic activity was observed even when the catalyst was reused in the reaction, and that it could be reused several times or more, leading to the completion of the present invention.

That is, the present invention uses tetra n-butyl titanate as a catalyst to react a reaction solution of n-butyl acrylate and dimethylaminoethyl alcohol under reduced pressure while distilling off by-product n-butanol, in the substantial absence of oxygen. The present invention relates to a method for producing dimethylaminoethyl acrylate, characterized in that tetra n-butyl titanate is first recovered by distillation and then purified.

The inventors previously filed a patent application (Patent Application Hei 1-04998
Although highly pure DA can also be obtained by directly distilling the reaction solution obtained according to method No. 7) in a nitrogen atmosphere, the present invention satisfies the recent demand for higher quality DA and saves resources. And a method that greatly contributes to cost reduction can be obtained.

The reaction molar ratio of BA and DMAH in the production method of the present invention is preferably 1.0 to 10.0, more preferably 1.1.
~5°0. If the molar ratio exceeds 10.0, a large reactor will be required and a large amount of energy will be required to recycle excess BA, so it is desirable to avoid this. Commercially available TBT can be used as is in the present invention.

The amount of TBT used is preferably in the range of 0.1 to 10 mol%, more preferably 0.5 to 5 mol%, based on the raw material DMAH. As for the method of charging TBT, it is possible to adopt a method of charging all at once, a method of continuous charging, or a method of charging in parts, but a method of charging TBT all at once at the time of charging raw materials is advantageous and preferable.

Although it is not usually necessary to use a reaction solvent, it is also possible to use, for example, xylene, toluene, hexane, etc. as an azeotropic solvent for by-product n-butanol.

Although the reaction temperature is influenced by the composition of the raw materials, it is determined by the degree of reduced pressure.

The preferred reaction temperature for the present invention is 60 to 150°C, more preferably 90 to 120°C, and this temperature is controlled by adjusting the degree of vacuum. Corresponding pressure reduction degree is 200-500To
It is rr.

The reaction time depends on the reaction temperature, amount of catalyst, etc., but is usually 4 to 5 hours.

In the present invention, it is preferable to add a polymerization inhibitor to the reaction system for the purpose of suppressing the thermal polymerization reaction during the reaction. The polymerization inhibitor used in this case may be known ones such as hydroquinone methyl ether, phenothiazine, etc., and one or more of these may be used. The amount of these polymerization inhibitors is preferably 0.01 based on the total amount charged.
It is used in a range of 2 tvt%, more preferably 0.05 to 1 wt%.

After completion of the reaction, unreacted BA, DMAE, by-product n-butanol, the target compound DA, etc. were distilled out from the reaction solution under reduced pressure in the absence of oxygen, and the catalyst TBT was removed.
High purity DA can be obtained by adding a polymerization inhibitor to the distillate again and distilling it in the absence of oxygen using a conventional method.

The recovered catalyst can be used as it is for repeated reactions without being purified to the same level, but as the number of repetitions increases, the viscosity tends to increase slightly, so from the point of view of stability in industrial production, recovery is not recommended. It is preferable to extract a portion of the catalyst and add a new catalyst for use.

In the conventional distillation in the presence of oxygen, DA is extremely susceptible to coloring and polymerization, and this tendency is even more pronounced at high temperatures, making it difficult to employ such a method.

When removing the catalyst by distillation, there are almost no high-boiling point impurities, so it is possible to completely distill out the volatile components.
Considering the handling at the time of reuse, the reaction finished liquid is 90-9
Preferably, 5% is distilled off. It is desirable to avoid reducing the distillation rate since it reduces the productivity of DA.

The polymerization inhibitor added at the time of redistillation may be any known one, such as hydroquinone, hydroquinone monomethylnitene, phenothiazine, etc., and one or more of these may be used.

The amount of these polymerization inhibitors is preferably 0.0% based on the total amount charged.
It is used in a range of 0.01 to 2 wt%, more preferably 0.05 to 1 wt%.

It is desirable to carry out the catalyst removal and DA purification steps at 130°C or lower in order to suppress the thermal polymerization reaction. Although it is possible to use a heat medium such as silicone oil to suppress the polymerization, it is possible to prevent the polymerization even if it is not used. No problems arise.

The distillate distilled in the reaction step of the present invention contains only n-butanol and a small amount of BA, so the n-
BA can be easily obtained by reacting the distillate containing butanol as a main component with, for example, acrylic acid, and this BA can be recycled as a raw material for the present invention, and the by-product alcohol can be effectively used. This is also one of the features of the present invention.

[Effect]

Conventionally, there has been no report on a technique for obtaining DA by transesterifying BA and DMAE using a TBT catalyst under reduced pressure and distilling off the by-produced n-butanol.
It is unclear why the present invention, which has these contents, allows DA to be obtained with high selectivity and high yield, and further shows the effect that the catalyst can be reused. As mentioned above, the TBT catalyst known in the art has been pointed out to have drawbacks such as deactivation over time, deactivation due to trace amounts of moisture, and a long reaction time due to low activity. Considering the current situation under consideration, the effect of the present invention is completely unpredictable.

For example, in the DA manufacturing method where methyl acrylate (hereinafter abbreviated as MA) is used as the alkyl acrylate and the by-product methanol is extracted under normal pressure by azeotroping with MA, TBT
Even if a catalyst is used in the same manner as in the present invention, the reaction rate is extremely slow and the yield of DA is about 30% even after 6 hours of reaction.

In addition, ethyl acrylate (
When the reaction is carried out in the same manner using EA (hereinafter abbreviated as EA),
After 7 hours of reaction, the yield of DA is about 70% and the selectivity of DA is 85 to 95%.

In addition, if the reaction is proceeded with distilling off the by-product n-butanol under normal pressure without maintaining a reduced pressure state using BA (hereinafter referred to as the normal pressure method), the reaction liquid will start to leak during the reaction, although the cause is unknown. It is observed that the mixture becomes cloudy, the reaction rate becomes extremely slow, and TBT is deactivated over time. Similar to the reduced pressure method, the normal pressure method requires the selective extraction of by-product n-butanol, but in the normal pressure method, in order to selectively and efficiently extract butanol, the reaction temperature must be 130 to 150°C. , as a result, polymerization of BA and DA occurs,
This results in a decrease in the yield of DA, and no superior effect of the present invention is found in the normal pressure method in any respect.

Furthermore, in the present invention, the effect of the present invention is exhibited even without using a reaction solvent as described above, and the process without using a reaction solvent is extremely simple, so that the present invention can be used more effectively industrially. .

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

According to studies by the present inventors, if the reaction solution obtained according to the method of the present invention is distilled without removing the catalyst (hereinafter referred to as direct distillation method), even under conditions that have a large rectification effect, the distillate DA Although 0.3 to 0.5% of low-boiling components were found to be mixed in, the catalyst TBT was removed by the above-described high-boiling distillation method.
It has been found that when distilled in the absence of DMAE, low-boiling components such as DMAE can be easily removed and DA with a high purity of 99.9% or more can be obtained. The details of how such an effect can be obtained are also unknown.

In addition, the catalyst can be reused as it is without any purification or other treatment, and according to the method of the present invention, it can be reused several times or more without adding a new catalyst. is possible. On the other hand, the catalytic activity of the residue obtained by the direct distillation method is low, and the effect seen in the high-boiling distillation method is not observed.

According to the present invention, the catalyst is hardly deactivated during the synthesis process, and the catalyst activity can be maintained even during the distillation process.

The effect of the present invention cannot be predicted at all from the phenomenon of catalyst deactivation over time, which was conventionally thought to be unavoidable in TBT.

The catalyst of the present invention can be used as it is, and the residue of the rectification tank in the DA refining process does not show any phenomenon of viscosity increase due to polymerization, and can be recycled as a raw material for rectification. Even if the removal is performed, there is no disadvantage such as a decrease in the yield of DA.

(Example) In order to explain the present invention more specifically, the present invention will be explained in detail by giving Examples and Comparative Examples.The definitions of conversion rate, selectivity and yield used in this specification are as follows. It is as follows.

1 Number of co-supplied DMAE moles Selectivity (%) = Yield (%) / Conversion rate (%) / 100 Overall yield (%) - Yield (%) × Distillation yield (%) / 100 Example 1゜1,920 g of BA (15,0-
T-/L, ), DMAE445 g (5.0 mol)
, TBT34. l g (0.1 mol) and phenothiazine 2.4 g (1,000 pp
m) was added, and heating was started under a reduced pressure of 300 Torr while stirring.

After total refluxing for 30 minutes, the temperature of the reaction solution was maintained at 110-120°C, and the temperature of the rectifying column was maintained at 96-98°C, while the n-butanol produced was extracted at a reflux ratio of 3.0-5.0. The reaction was carried out for 4 hours.

When the reaction solution was analyzed by gas chromatography, D
The MAE reaction rate was 92%, and the DA yield was 90%.

Next, this reaction solution was heated under a nitrogen atmosphere at 30 Torr and 90
The catalyst was removed at ~100 °C and the distillate containing DA was 1,9
44g was obtained. Furthermore, 1.9 phenothiazine was added to the distillate.
After adding 70 g of water, using a rectification column (15 theoretical plates) equipped with a cooler and a fractionation column, under a nitrogen atmosphere at 20 Torr, 70
n-butanol at ~85°C, reflux ratio 1.0-10.0,
After distilling off BA and DMAE, 2
．． QTorr, 85-95°C1 reflux ratio 1.0-2.0
611 g of DA was obtained.

The overall yield of DA was 86% and the purity was 99.9%.

Comparative example 1゜Example 1. Equipment similar to MA 1,290g (15
゜0 mol), DMAE445 g (5.0 mol)
, 34.1 g (0.1 mol) of TBT and 1.8 g (1,000 ppm) of phenothiazine as a polymerization inhibitor were added, and heating was started with stirring. The generated methanol and MAO azeotrope were completely refluxed for 30 minutes, and then reacted for 6 hours while maintaining the top temperature of the rectification column at 60 to 65°C and extracting the azeotropic mixture from the system.

As a result of analyzing the reaction solution by gas chromatography, the yield of DA was 28%.

Comparative example 2゜Example 1. The reaction was carried out in the same manner as above for 4 hours.

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

Next, a rectification column (15 theoretical plates) equipped with a cooler and a fractionation column
under nitrogen atmosphere, 20 Torr, 70-85 @,
n-butanol, BA, DM at a reflux ratio of 1.0 to 30.0.
After distilling off the AE, the temperature was adjusted to 2Q Torr under the same nitrogen atmosphere.
, distilled at 85-95°C1 reflux ratio 1.0-2.0, D
586 g of A was obtained. The overall yield of DA was 82% and the purity was 99.6%.

Example 2゜Example 1. The reaction was carried out in the same manner as above for 4 hours.

When the reaction solution was analyzed by gas chromatography, D
The MAE reaction rate was 91%, and the DA yield was 90%.

This reaction solution was heated under nitrogen atmosphere at 30 Torr, 90 to 10
The catalyst was removed at 0°C and the distillate containing DA was heated to 20°121
I got g. Example 1. 106 g of the catalyst recovered in Example 1, 920 g (15.0 mol) of BA L, and 445 g (5.0 mol) of DMAE were added to the same apparatus as 3.
Heating was started under reduced pressure of 0.00 Torr while stirring. The reaction was carried out for 4 hours while maintaining the reaction solution temperature at 110 to 120°C and the rectification column top temperature at 96 to 98°C and extracting the produced n-butanol at a reflux ratio of 3.0 to 5.0.

When the reaction solution was analyzed by gas chromatography, D
The reaction rate of MAH was 90%, and the yield of DA was 89%. The reaction was carried out in the same manner a total of four times, and the results are shown in the following table.

As is clear from the table, no decrease in the activity of the catalyst was observed even when the recovered catalyst was used repeatedly.

Furthermore, no accumulation of high-boiling point impurities was observed.

C6 Effects of the Invention According to the present invention, dimethylaminoethyl acrylate can be produced with high purity, high yield, and low cost, and provides a raw material that is very suitable for producing polymer flocculants, fiber treatment agents, etc. The benefits they can bring to the industries that use them are enormous.

Claims (1)

[Claims] 1. Using tetra n-butyl titanate as a catalyst, n was reacted under reduced pressure while distilling off the by-produced n-butanol.
- Production of dimethylaminoethyl acrylate, characterized in that tetra n-butyl titanate is first recovered and then purified by distilling a reaction solution of butyl acrylate and dimethylaminoethyl alcohol in the substantial absence of oxygen. Method