JPH0774196B2 - Method for producing maleimide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Purpose of the Invention (Field of Industrial Application) The present invention is used as a raw material for various polymer compounds, and as a raw material for antioxidants, rubber curing agents, corrosion inhibitors, bactericides, and the like. As
The present invention relates to a method for producing maleimide, which is a compound having an extremely wide range of applications.

(Prior Art and Problems Thereof) The following are known known methods for producing maleimide.

As a method for producing a maleimide, for example, a method of oxidizing pyrrole with chromium sulfate or oxygen with oxygen in the presence of light and eosin, and a method of heating mycin diamide with zinc chloride are known. bad.

A method is known in which maleic anhydride is reacted with furan or cyclopentadiene to produce a Diels-Alder adduct, which is treated with ammonia to be converted into an imide compound, and further thermally decomposed to obtain maleimide. The process is complicated and cannot be said to be an industrial manufacturing method.

Further, the following two examples are known as methods for producing maleimide by cyclodehydration of maleamic acid in a liquid phase using a dehydrating agent.

1) German Patent Laid-Open Publication No. 1,934,791 discloses a method of producing maleimide by mixing and heating previously dehydrated orthophosphoric acid and maleamic acid and then distilling them, but the yield of maleimide is low.

2) In JP-A-50-126659, maleamic acid is reacted with a dehydrating agent such as acetyl chloride, benzoyl chloride, thionyl chloride or phosphorus pentoxide in an amide solvent at a temperature of -10 ° C to 90 ° C. A method for producing a maleimide is shown. However, acetyl chloride and thionyl chloride, which are dehydrating agents that generate maleimide by this method, have extremely high reactivity with water and react with water in the air to generate a large amount of hydrochloric acid gas or sulfurous acid gas, or with water. Not only is the handling method not simple, such as the generation of high heat due to the rapid reaction of, but it is highly dangerous to the human body and is highly corrosive. As a result, workability is poor and equipment costs are high. Furthermore, these dehydrating agents are expensive, are difficult to recover from the reaction product, and are difficult to dispose of. Also, post-treatment is difficult in the reaction using these dehydrating agents, which is industrially disadvantageous. There are many points.

Further, in the dehydrating agent described in this publication (JP-A-50-126659), the formation of maleimide is recognized in acetic anhydride, ethyl chloroformate, etc., which has a relatively low reactivity with water and is relatively easy to handle. None or low production rate.

In addition to these, various dehydrating agents are known, for example, by reacting a dehydrating agent such as phosphorus trichloride, phosphorus pentoxide, antimony trichloride, antimony pentachloride, phosphorus oxychloride with maleamic acid, The production rate of maleimide is low.

The above dehydrating agent, for example, phosphorus trichloride and phosphorus pentachloride are chlorinating agents (in organic synthesis), and acetyl chloride and acetic anhydride are acetylating agents. Therefore, since the action mechanisms that cause dehydration are different from each other, it is not always possible to obtain maleimide in high yield using any dehydrating agent.

(B) Structure of the invention The present inventor has conducted extensive studies on a dehydrating agent for maleamic acid and / or a salt thereof, and as a result, cyanuric chloride, which has not been industrially used as a dehydrating agent, is maleamine acid and / or its The present invention has been completed by finding that maleimide is produced in high yield by reaction with a salt.
It should be noted that cyanuric chloride is inexpensive, has low reactivity with water, has low corrosiveness, is easy to handle, and has the advantage of being less dangerous to the human body. Thus, the present invention provides for the use of maleamic acid and / or in a substantially anhydrous aprotic polar solvent.
Alternatively, the gist is a method of producing a maleimide by dehydrating the salt with cyanuric chloride.

In producing the maleimide in the present invention,
(I) Maleamic acid and / or a salt thereof is dissolved or dispersed in an aprotic polar solvent and cyanuric chloride is added thereto, or (ii) Cyanuric chloride is dissolved in an aprotic polar solvent, or You may make it disperse | distribute and may add maleamic acid and / or its salt here, and may make it react. Furthermore, both may be added simultaneously in the aprotic polar solvent. In this way, the two react with each other in the aprotic polar solvent to form maleimide. At this time, since the reaction heat is generated relatively little, the temperature can be easily controlled, and since the maleimide is produced at a high production rate in a wide range of temperature, stable production with high yield can be easily achieved. The reaction proceeds faster at higher temperatures, but ends in a short time even at a mild temperature near room temperature. After the completion of the reaction, cyanuric chloride used as a dehydrating agent becomes cyanuric acid, but since cyanuric acid has extremely low solubility in general organic solvents, it can be easily recovered and reused.

Here, as the aprotic polar solvent, those having high solubility of maleamic acid and / or a salt thereof are preferable, and N, N-dimethylformamide, N, N-diethylformamide, N, N-methylethylformamide and the like are used. N, N-di-lower alkylformamide is particularly preferred. Further, other non-polar solvent that does not adversely affect the reaction (for example, benzene, toluene, chloroform, carbon tetrachloride, etc.) may be used in combination. It goes without saying that these solvents need to be used in a substantially anhydrous state to the extent that the reaction of the present invention is a dehydration reaction, so that the reaction is not substantially hindered. Further, the amount used is not particularly limited, but it is preferable to use the same weight or more with respect to the maleamic acid.

Examples of the salt of maleamic acid include metal salts such as alkali metals and alkaline earth metals and tertiary amine salts such as trialkylamines.

The amount of cyanuric chloride used as a dehydrating agent is theoretically required to be 1/3 mol per 1 mol of maleamic acid. Therefore, cyanuric chloride is usually added to 1 mol of maleamic acid.
Use at least 1/3 mol. However, from an economical point of view, unreacted maleamic acid can be recovered and reused by using a small amount of, for example, 0.05 mol, of cyanuric chloride to 1 mol of maleamic acid. On the other hand, the upper limit of the amount of cyanuric chloride used is not particularly limited, but it is not economically preferable to use it in an amount of 1.5 times or more mol per 1 mol of maleamic acid.

The reaction temperature is preferably −20 ° C. or higher and 100 ° C. or lower. If the temperature is below -20 ° C, the reaction time will be longer than necessary.
It is difficult to control the reaction at high temperatures above 0 ° C, and side reactions cannot be ignored. An even more preferable reaction temperature is 0 ° C or higher and 80
It is below ℃.

When the maleimide synthesized in this manner is isolated from the reaction system, the reaction is stopped by adding water, for example, and the precipitated cyanuric acid is separated and recovered, and the solubility in water such as ethyl acetate is low. Extraction with a solvent that dissolves, evaporation of the solvent, and recrystallization with water may be performed. The maleimide once produced has a high yield because it has good stability in the reaction system.

The present invention will be specifically described below with reference to Examples and Comparative Examples.

(Example) Example (1) In a 200 ml four-necked flask equipped with a thermometer, a reflux condenser and a stirrer, 11.5 g (0.1 mol) of maleamic acid and 60 ml of N, N-dimethylformamide were put and mixed and dissolved. To this, 12.91 g (0.07 mol) of cyanuric chloride was added and mixed, and the reaction temperature was controlled at 40 ° C. When the reaction product after 10 minutes was quantified by gas chromatography, the production rate of maleamide was confirmed to be 94.3%. Then, 30 ml of water was added to stop the reaction, and the precipitated cyanuric acid was collected by filtration and then extracted with ethyl acetate. The solvent was distilled off and recrystallization from water yielded 8.27 g (0.0853 mol) of white crystals. (Melting point
93.5-94.5 ° C).

When the IR spectrum of this crystal was compared with that of a maleimide sample, all the peaks were in agreement and were confirmed to be maleimide. Further, the content of maleimide in the crystals was determined by gas chromatography and found to be 99% or more.

Examples (2) to (7) The procedure of Example (1) was repeated except that the reaction temperature and the reaction time were changed. Table 1 shows the relationship between the reaction temperature and the reaction time and the maleimide production rate.

Example (8) The procedure of Example (1) was repeated, except that the solvent was changed to N, N-diethylformamide. The production rate of maleimide after 1 hour of reaction time was 86.1%.

Example (9) In a 200 ml four-necked flask equipped with a thermometer, a reflux condenser and a stirrer, 9.22 g (0.05 mol) of cyanuric chloride was dissolved in 50 g of N, N-dimethylformamide. To this, 13.7 g (0.10 mol) of sodium maleamate was added and mixed. When the reaction temperature was controlled at 50 ° C. and the maleimide production rate after 1 hour was measured by gas chromatography, it was 83.2%.

Comparative Example (1) The procedure of Example (1) was repeated except that the solvent was changed to protic solvents such as methyl alcohol, acetic acid, and acetone. After 1 hour of reaction time, the production rate of maleimide was quantified by gas chromatography, but the production of maleimide was not observed in any case.

Comparative Example (2) [Additional test of Example 1 described in JP-A-50-126659] In a 200 ml four-necked flask equipped with a thermometer, a reflux condenser and a stirrer, 11.5 g (0.1 mol) of maleamic acid and N were added. 50 ml of N-dimethylformamide was added and mixed and dissolved. Acetyl chloride (10.0 g, 0.125 mol) was added dropwise to the reaction mixture at a temperature of 28 to 33 ° C. After completion of the dropping, the mixture was reacted at 48 to 52 ° C. for 1 hour, and then the production rate of maleimide in the system was quantified by gas chromatography. As a result, a production rate of 82.9% was confirmed. Then methanol
After adding 30 ml, the solvent was distilled off by vacuum distillation at 80 ° C. in a nitrogen stream. 10 ml of water was added to the residue to dissolve it, 130 ml of diethyl ether was extracted in four portions, dried over anhydrous sodium sulfate, and the diethyl ether was distilled off. As a result, white crystals 9.45
got g. However, this crystal has poor purity, and the content of maleimide was measured by gas chromatography.
64.0%, the practical yield of maleimide is 6.05 g (0.0
624 mol).

Comparative Example (3) 11.5 g of maleamic acid was dissolved in 50 g of N, N-dimethylformamide, and benzoyl chloride 1 was added at a reaction temperature of 50 ° C. with stirring.
6.6 g was added dropwise. After 30 minutes, the production rate of maleimide was measured by gas chromatography and found to be 59.6%.

Comparative Example (4) The procedure of Example (1) was repeated except that the dehydrating agent was changed to 12.8 g (1.25 mol) of acetic anhydride. The production rate of maleimide was measured 30 minutes and 2 hours after the addition of the dehydrating agent, but no production of maleimide was observed.

(C) Effects of the Invention According to the present invention, (1) a target product, a high yield of maleimide, (2) the use of dianur chloride, which is less reactive with water and less corrosive, as a raw material, Workability is good and equipment cost is low. (3) Compared to acetyl chloride, which is water-soluble and difficult to recover, cyanuric acid, which is a product after reaction of cyanuric chloride, has a high solubility in a solvent, particularly water. Since it has low crystallinity and good crystallinity, it can be easily separated and recovered. The recovered cyanuric acid is also useful as a chlorine stabilizer in water, a resin raw material for paints, and a selective herbicide. (4) It can be synthesized in a short time under mild temperature conditions. Therefore, it is extremely useful as an industrial production method of maleimide.

Claims (3)

[Claims] 1. A method for producing maleimide, which comprises obtaining maleimide by dehydrating maleamic acid and / or its salt in a substantially anhydrous aprotic polar solvent in the presence of cyanuric chloride. 2. The production method according to claim 1, wherein the reaction temperature is −20 ° C. or higher and 100 ° C. or lower. 3. The process according to claim 1, wherein the aprotic polar solvent is N, N-dilower alkylformamide.