JPS6023101B2 - Method for producing methacrylic acid dimethylaminoethyl ester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [1-] The present invention relates to a method for producing dimethylaminoethyl methacrylate ester by transesterifying methyl methacrylate and dimethylaminoethyl alcohol in the presence of a transesterification catalyst.

It is known that dimethylaminoethyl methacrylate is produced by transesterifying methyl methacrylate and dimethylaminoethanol, and conventionally, an alkali metal alcoholate such as sodium methylate has been used as a transesterification catalyst. It has been known.

However, according to the study results of the present inventors, when the above transesterification reaction is carried out using an alkali metal alcoholate as a catalyst, the double bond of methyl methacrylate and dimethylaminoethyl methacrylate to be produced, The disadvantage is that the addition reaction between the raw material dimethylaminoethanol and the methanol created by the reaction is extremely likely to occur, reducing the yield and purity of the target substance dimethylaminoethyl methacrylate. found. It has also been proposed to use aluminum alcoholate or titanium alcoholate as a catalyst, but these catalysts are both expensive and easily hydrolyzed and deactivated by excess moisture.
It has drawbacks such as the need for a troublesome dehydration operation in the reaction system in advance. Furthermore, in general, when the above-mentioned metal alcoholate is used as a catalyst in a transesterification reaction, there are the following problems.

That is, as shown in formula m, these metal alcoholates M(OR)n are first substituted with the raw material alcohol R'OH used in the transesterification reaction, [wherein M is N
metals such as a, K, Mg, AI, Tj, R is methyl,
Alkyl groups such as ethyl and propyl, n is 1, 2, 3
, is an integer of 4, which is the same as the valence of the metal M, and ROH means the raw material alcohol used in the transesterification reaction, respectively.

] M(OR') n For example, titanium isopropylate is said to exhibit catalytic activity in the form of Ti( OC 3 days 7) 4 is substituted with the raw alcohol dimethylaminoethanol and changes to Tj [OC 2 days 4N (C ratio) 2] 4, so the expensive raw material dimethylaminoethanol is lost by 4 moles of titanium. In addition, it also has the disadvantage that isopropanol is produced as a by-product, making the separation operation complicated.

■ As a result of intensive studies to solve the problems of conventional catalyst installation, the inventors have found that these problems can be solved by selecting specific catalysts such as potassium carbonate, rubidium carbonate, and cesium carbonate. This discovery led to the completion of the present invention. That is, the present invention provides ``In producing dimethylaminoethyl methacrylate ester by transesterifying methyl methacrylate and dimethylaminoethanol in the presence of a transesterification catalyst, potassium carbonate, A method for producing dimethylaminoethyl methacrylate, which is characterized by using a carbonate of an alkali metal selected from the group consisting of rubidium carbonate and cesium carbonate.

(3} Below, the constituent elements of the present invention will be divided and explained in detail.

In the method of the present invention, the amount of methyl methacrylate used is in the range of 1.2 to 10 moles, preferably 1.5 to 5 moles, per mole of dimethylaminoethanol.

As the polymerization inhibitor, those well known as polymerization inhibitors for unsaturated esters, such as phenothiazine, hydroquinone, and hydroquinone monomethyl ether, can be used, and the amount added is 0.05 to 100% of the reaction solution.
A range of 2% by weight is preferred. Next, the amount of the catalyst used is in the range of 0.01 to 2% by weight, more preferably 0.02 to 1% by weight, based on the total amount of methyl methacrylate and dimethylaminoethanol. % by weight.

As the catalyst, potassium carbonate, rubidium carbonate, or cesium carbonate can be equally used, but calcium carbonate is particularly preferred from the viewpoint of catalytic activity and cost.

The quality of these carbonates is equivalent to that of anhydrous industrial chemicals, and they can be used sufficiently. However, regarding lithium carbonate and sodium carbonate, which are carbonates of the same alkali metal,
As a result of experiments conducted by the present inventors, it was found that almost no catalytic activity was observed. It has now been found that the catalyst used in the process of the invention has a significantly increased activity in the dissolved state compared to the solid state.

However, since the solubility of these catalysts in the mixture of methyl methacrylate and dimethylaminoethanol is low regardless of temperature, when added to the mixture of methyl methacrylate and dimethylaminoethanol in a solid state, Even under heating, the amount dissolved is still small, and as a result, the catalytic activity is not necessarily satisfactory. On the other hand, the catalytic activity can be increased by first dissolving these catalysts in dimethylaminoethanol, which is more soluble than methyl methacrylate, under heating, and then adding a predetermined amount of methyl methacrylate. It becomes possible to make it larger. Further, as a means for increasing the solubility of the catalyst of the present invention, there is a method of dissolving the catalyst in methanol and using it, which is an extremely preferred embodiment.

That is, the catalyst has particularly high solubility in methanol among organic solvents, and methanol is a by-product of the transesterification reaction, and can be quickly released from the reaction system by co-isolation with methyl methacrylate. This is because it is a substance that does not participate in brewing or reaction. Therefore, the reaction rate can be further increased by melting the catalyst in methanol under heating in advance and adding this to the mixture of dimethylaminoethanol and methyl methacrylate. In the method of the present invention, the transesterification reaction can be carried out under normal pressure, but from the viewpoint of suppressing polymerization, the reaction is preferably carried out under reduced pressure, preferably in the range of 200 to 760 torr. The reaction temperature is determined by the boiling point of the reaction system at that pressure, and is preferably in the range of 80 to 13,000 because the reaction rate is sufficiently high and polymerization can be sufficiently suppressed. This transesterification reaction is shown by equation '2), but in order to obtain dimethylaminoethyl methacrylate in high yield, it is necessary to remove the methanol produced from the reaction system.

Therefore, the by-product methanol can be extracted from the system by azeotropic distillation with methyl methacrylate in a reaction. Here, one embodiment of the reaction operation is shown in which a reaction tank with a distillation column is used as the reaction tank, and the temperature at the top of the distillation column is preferably as close as possible to the azeotropic temperature of methanol and methyl methacrylate. Bringing the distillate gas from the top closer to an azeotropic composition,
Further, in order to minimize the release of dimethylaminoethanol, it is necessary to carry out reflux at an appropriate ratio, and the reflux ratio is preferably in the range of 1 to 1 bait concentration. As the reaction progresses, the production of final ethanol decreases, so the temperature at the top of the column increases.
By monitoring this temperature, the progress of the reaction can be determined. Furthermore, the progress of the reaction can also be confirmed by analyzing unreacted dimethylaminoethanol in the reaction solution using gas chromatography. The reaction time may vary depending on the molar ratio of raw materials, pressure, reflux ratio, etc., but is usually 5 to 7 hours. After the reaction is completed, unreacted methyl methacrylate is first distilled off from the reaction solution under reduced pressure, and then the target product, dimethylaminoethyl methacrylate, is distilled off. According to the method of the present invention, the catalytic activity is sufficiently high compared to other catalysts, and there is little decrease in yield due to side reactions, resulting in high yield and high purity compared to other catalysts. dimethylaminoethyl methacrylate can be produced.

Furthermore, in terms of catalyst cost, combined with the small amount used, it is clearly cheaper than other catalysts. Dimethylaminoethyl methacrylate produced according to the present invention can be used as an extremely important raw material for obtaining cationic polymers used as flocculants, conductive processing agents, and paper-making agents.

{41 Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Glass tube with outer diameter 5 side and length 5 side filled with 50% inner diameter 5
Enemy Mosquito, 1 with rope azusa machine with length 55 skin glass column
The flask was placed in an oil bath.

The outside of the glass column could be heated with a ribbon heater, and a splitter-type reflux distributor was attached to the top of the column. Add 133.7 torr of dimethylaminoethanol, 600.7 torr of methyl methacrylate, 1.5 torr of phenothiazine, 1.5 torr of hydroquinone monomethyl Able, and 2 torr of powdered special grade anhydrous potassium carbonate under reduced pressure to the above flask. heated with.

Total reflux is carried out until the top of the column falls to 53.5 to 5400, and after reaching the above temperature, while changing the reflux ratio to maintain the temperature, methanol produced by the reaction is distilled out of the system by azeotropy with methyl methacrylate. I forced it. The reflux ratio during this period is approximately 2 to 6.
The reaction was terminated when the top temperature reached 7,000 and the reflux ratio reached 10. The reaction time was 5 hours. Then, the system internal pressure was set to 20 Torr, and the tower top temperature was set to 20 to 20 Torr.
Distill methyl methacrylate at 30oo, and further,
Dimethylaminoethyl methacrylate was distilled at a pressure of 5 torr and a top temperature of 56 to 5,800.

The purity of this distillate was 212.1 minutes, and the purity of dimethylaminoethyl methacrylate was 99.2%, which is a yield of 89.9% based on the raw material dimethylaminoethanol.
Met. Example 2 The same reaction apparatus as in Example 1 was used, and the reaction was carried out in exactly the same manner as in Example 1, except that the type of catalyst was changed.

Claims (1)

[Claims] 1. In producing dimethylaminoethyl methacrylate ester by transesterifying methyl methacrylate and dimethylaminoethanol in the presence of a transesterification catalyst, the group consisting of potassium carbonate, rubidium carbonate, and cesium carbonate is used as the transesterification resin. 1. A method for producing dimethylaminoethyl methacrylate ester, characterized by using a carbonate of an alkali metal selected from the above.