JPS62138468A - Production of n-substituted maleimide - Google Patents

Abstract

PURPOSE:In producing the titled compound from maleic anhydride and a primary amine through a dicarboxylic acid monoamide, to purify the aimed compound advantageously, by bringing a remaining acidic substance into contact with a specific basic substance before distillation and/or during distillation. CONSTITUTION:In producing an N-substituted maleimide useful as a heat resistance improver for a resin such as ABS, MMA, PVC, etc., an intermediate for drugs and agricultural chemicals, by dehydrating a dicarboxylic acid monoamide, obtained from maleic anhydride and a primary amine, in the presence of an acid or a compound which is reacted with water to form an acid, an acidic substance remaining in the reaction solution is brought into contact with one or more basic substances selected from an oxide, a hydroxide and a carbonate of an alkaline earth metal preferably in the presence of water before distillation and/or during distillation so occurrence of polymerization reaction and impurities such as maleic anhydride, etc., is suppressed and the aimed high-purity compound is obtained by a simple process in high yield.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is applicable to ABS, MMA, PVC, etc., which are used as intermediate thickness 1 for heat resistance improvers, pharmaceuticals, and agricultural chemicals.
This invention relates to an improved method for producing substituted maleimides.

[Prior Art] Conventionally, as a method for producing Ni-converted maleimide from maleic anhydride and a primary amine via a dicarboxylic acid monoamide, for the latter half of the dehydration reaction, (1) a method of omitting the action of a dehydrating agent such as acetic anhydride ( For example, Special Publication No. 46-29140
．． USP 2,14.536>, (2) using a base as a catalyst,
A method of azeotropic dehydration of produced water with a solvent (for example,
7-24024>, (3) Method of azeotropic dehydration of produced water with a solvent using an acid as a catalyst (19 Suebo, Japanese Patent Publication No. 55-4639
4.1 Imomon nR60-100554, JP11J (60
-112758> etc. are listed in 7.1. However, (1
Method (2) is economically disadvantageous because it consumes an equimolar amount of 11 (2) with respect to the produced water, and method (2) generally requires high temperature and has poor yield and crystallinity. Must have.

On the other hand, as method (3), \2. ＼-dimethylacetamide, N-methylpyrrolitone, etc.
Add onium salt (1", r!f: fl
No. 0-213154), a method was attempted to improve the solubility of dicarboxylic acid monoamide, which is necessary as a catalyst or intermediate, and to facilitate the reaction, and the desired N-substituted maleimide was obtained with relatively high yield. There is. However, it is not necessarily sufficient to separate and purify high-purity N-substituted maleimide from the obtained reaction product in good yield.

As a separation and purification technique for N-substituted maleimide, for example, there is a method in which a reactant is added to a large amount of water and precipitated as crystals, but this results in a large loss of solvent and N-substituted maleimide. In a method in which the reactant is used as it is, or all or part of the solvent is distilled off, cooled, and the precipitated crystals are filtered out, catalyst remaining in the reaction solution, unreacted dicarboxylic acid monoamide, and various side reactions are removed. The adhesion and contamination of substances to the crystals is unavoidable, and complicated processes such as recrystallization using a new solvent are required to obtain 1q of high-purity products. Furthermore, a method of purifying the reactant by distillation has also been reported (Japanese Patent Application Laid-open No. 12758/1983).
. In this method, after the reaction using a phosphorus-based dehydrating agent, most of the solvent is evaporated, the solution phase of the phosphorus compound is separated into fraction 1, and the N-substituted maleimide is then distilled. Is it necessary? If only liquid separation is performed in step 11, strong acidic compounds such as phosphoric acid will remain, so from the viewpoint of preventing corrosion of the equipment (purchasing restrictions apply).Furthermore, if the intermediate dicarboxylic acid monoamide is present in the reaction product, However, if residual acidic compounds such as phosphoric acid exist, decomposition products such as maleic anhydride will be generated during distillation, which will inevitably lead to disadvantages such as a significant decrease in the target purity of the Nu-substituted maleimide, which is not necessarily industrially satisfactory. There's no way to do it.

[Problems to be Solved by the Invention] The present inventors dehydrated dicarboxylic acid monoamide in the presence of an acid or a compound that reacts with water to produce an acid (hereinafter referred to as "acid catalyst etc."). Regarding the method for producing N-substituted maleimide, the above-mentioned drawbacks have been improved, and high-purity N-substituted maleimide can be obtained in a high yield through a simple process, and the quality can be improved even if dicarboxylic acid monoamide, which is a reaction intermediate, remains. We investigated ways to find more advantageous methods, such as those that do not become a hindrance.

As a result, the acidic substances remaining in the reactants are hydroxylated.
~ When distilled after neutralization with an alkali metal compound such as aluminum or potassium hydroxide, N-substituted maleimide polymerizes during distillation and the yield decreases significantly, whereas alkaline earth metal hydroxides etc. When distilled after neutralization with an alkali earth metal hydroxide or the like, the polymerization reaction that occurs with alkali metal compounds does not occur, and furthermore, even if dicarboxylic acid monoamide coexists in the distillation raw material, maleic anhydride is not produced. The inventors have discovered that extremely pure N-substituted maleimides can be obtained in high yields because no impurities such as acids are generated, and have completed the defense of the present application. Ilj et al., the present invention relates to maleic anhydride and
When separating and purifying N-substituted maleimide, which is obtained by dehydrating a dicarboxylic acid monoamide that is protected from amines in the presence of an acid catalyst, the remaining acidic substance is mixed with a specific basic substance before distillation and/or by distillation. Contact inside 'V
Make it J! The object of the present invention is to provide a method for obtaining extremely pure N-substituted maleimide with a high yield through a simple process.

[Means for Solving the Problems] It is recommended that the primary amine used in the present invention be a compound represented by the following general formula.

NH2 (wherein R is an alkyl group, a halogen atom, an alkoxy group, a carboxyl group, an alkyl group having 1 to 20 carbon atoms, which may have a substituent such as a 2-2 group or a hydroxyl group, or a cycloalkyl group) , ) represents an engineering group or a naphthyl group) Specifically, methylamine, ethylamine, n-butylamine, n-ocdylamine, 2-ethylhexylamine, n-dodecylamine, n-octadecylamine, cyclohegycylamine, aniline. , toluidine, xylidine, ethylamine, isopropylaniline, dodecylamine, p-chloroaniline, 2,4-dichloroaniline,
Examples include anisidine, phenetidine, amine-benzo-1, nitroaniline, and aminophenol.

The acid catalysts used in the reaction according to the present invention include (11) phosphoric acid, phosphorous acid, hypophosphorous acid, metaphosphoric acid,
Non-carrying acids such as pyrophosphoric acid, tripolyphosphoric acid, polyphosphoric acid, organic acids such as methanesulfonic acid, p-toluenesulfonic acid, benzenesulfonic acid, naphthalenesulfonic acid, and phosphorus pentoxide, phosphorus sesquioxide, sulfur trioxide, Examples include oxides such as sulfur disilide.

For the above-mentioned acid catalysts, it may be more preferable to use onium compounds such as trimethyldodecyl ammonium bromide, benzyltrimethyl ammonium chloride, etc. or tertiary amines as co-catalysts. Specific examples of the above compounds are detailed in Japanese Patent Application No. 60-213154.

The basic substance used in separating and purifying N-substituted maleimide from the reaction product is an alkaline earth metal oxide, its hydroxide, or its carbonate, and among these, magnesium, calcium, or barium is used, but is not particularly limited. The oxides, hydroxides or carbonates of are preferred. These basic substances can be used alone or in a mixture of two or more.

The amount of these basic substances used is preferably 0.5 to 100 times the amount of acidic substances in the distillation raw material.

If the amount is less than 0.5 times the equivalent, the quality of the N-substituted maleimide obtained by distillation will be poor, and the effect of preventing corrosion by acidic substances will be insufficient. On the other hand, if it is used more than 100 times as much, it will only be economically disadvantageous and there will be no industrial advantage. However, this upper limit does not apply, for example, when a packed column is filled with molded articles or crushed pieces of the basic substance and a distillation raw material is passed therethrough.

When applying a basic substance, it is preferable that water coexists with the substance, as this will promote the reaction with the acidic substance in the distillation process. In this case, the amount of water added is preferably 1 to 50% by weight based on the distillation raw material.

As the solvent used in the reaction, any of hydrocarbons, halogen-containing hydrocarbons, and aprotic polar solvents can be used. Specifically, toluene, xylene, ethylbenzene, cumene, hexane, octane, decane, cyclobexane, methifurediclohexane, ethylcyclohexane, light oil, chlorbepine, dichloroethane, trichloroethane, perchlorethane, N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-methylcaprolactam, tetramethylurea, N,N-dimethylpiperidinone, dimethylsulfoxide, sulfolane, methylisobutylketone, hexamethylphosphoro Amide, 1.
3-dimethyl-2-imidazolidinone and the like can be used alone or in a mixture of two or more.

A general method of carrying out the invention is described below.

Maleic anhydride and a primary amine are reacted in the presence of the aforementioned solvent at temperatures below 150'C, preferably from 20 to 80'C to form the corresponding dicarboxylic acid monoamide, and then the resulting reaction ) Add an acid catalyst etc. to the mixture, 90~
Generally, the reaction is carried out by stirring and heating at 150°C, preferably 00 to 40°C, and removing water produced by the reaction. However, maleic anhydride and a primary amine are reacted in a different solvent than the dehydration reaction of dicarboxylic acid monoamide, such as acetone, the intermediate dicarboxylic acid monoamide is once separated, and then the dehydration imidization reaction is performed in the above solvent. You can also do that. Furthermore, when only a nonpolar solvent such as a hydrocarbon or a halogen-containing hydrocarbon is used as a solvent, it is preferable to use an acid catalyst or the like together with the above-mentioned onium compound and/or tertiary amine.

Next, the distillation raw material is brought into contact with the above-mentioned specific basic substance, and various methods can be employed for this purpose. For example, the basic substance can be added alone or together with water to the reaction product and then directly distilled.
Distillation or further distillation can be performed after removing unreacted basic substances by δ. In addition, steaming water is passed through a tower filled with molded products and crushed pieces of the basic substance! You can also do a. It is preferable to add water in these cases as well.

Depending on the type of acid catalyst, solvent, and amine used in raw material box 1, the acidic substance may be separated by cooling the reaction solution. In this case, it is particularly preferable to add the basic substance after separating and removing the acidic substance, since a sufficient effect can be obtained with a small amount of the basic substance. Further, when the reaction mixture containing only a non-polar solvent or a non-polar solvent is sufficiently cooled, the N-substituted maleimide precipitates as crystals.

In this case as well, it is preferable to treat the filtered crystals with a basic substance.

Distillation is preferably carried out under reduced pressure at a liquid temperature of 200'C or less. At temperatures above 200'C, the product deteriorates, resulting in a decrease in yield and quality.

[Example 1 The present invention will be explained in detail with reference to Examples below.

Example 1 Maleic anhydride (47.5!7 (0.0
, 50 mol), xylene 1453, toluene 273 and n-octane 35 cJ were charged, and while stirring at a reaction temperature of 50'C, aniline 44. i (0.48 mol) was added dropwise little by little over 1 hour, and the mixture was allowed to react roughly for 30 minutes at the same temperature.

To the resulting reaction mixture were added 2.59 g of sulfuric acid and 0.93 g of benzyltrimethylammonium chloride, heated at reflux temperature (125 to 135° C.) with stirring, and reacted for about 3 hours while removing produced water.

After the reaction is complete, separate the acid 14 compounds into layers under a cold oven, and add calcium hydroxide 2.89% (2.0 times the remaining acidic substance) to the upper layer, water 6.59 was added and stirred for 1 hour at 80'C. Next, at 70'C, excess solids such as calcium hydroxide were filtered out, the aqueous layer was separated, and the oil layer was poured into a 500 mI! It was transferred to a bottle flask and distilled under reduced pressure.As a result, a yellow crystalline product of 75.69 (yield 91% based on the charged aniline) was obtained. The purity of N-phenylmaleimide by GPC is 99% or more, and the acid value is 0.
It was of extremely high purity, with a purity of 1 or less.

Example 2 Maleic anhydride 47°59 was placed in the same reactor as Example 1.
(0.50 mol) was charged with 2009 y of luene and 20 y of N-methylpyrrolidone, and while stirring at a reaction temperature of 40'C, 44.7 y (0.48 mol) of aniline was added little by little at 1 ml.
The mixture was added dropwise over a period of time, and the reaction was continued for an additional 30 minutes at the same temperature. Phosphoric acid-7,07 was added to the resulting reaction mixture and stirred.
The reactor was heated at 10'C for 2.5 hours while removing the produced water. After the reaction is complete, cool and separate the acidic substance in the lower layer, and add 5.0g of magnesium hydroxide to the upper layer (6 times equivalent to the acidic component).
, 10.09 g of water was added, and the mixture was stirred at 70'C for 1 hour.

Next, excess solids such as magnesium hydroxide were removed by filtration, and the product was distilled under reduced pressure in the same manner as in Example 1.

As a result, the melting point was 90.5-91.5°C, and the GPC purity was 9.
N-71 Nilmaleimide 78.9% or more, acid value 0.2.
0 g (yield based on aniline: 94%) was obtained.

Example 3 In a reactor similar to Example 1, 71 twin acid anhydride and 47°59
(0.50 mol) and; heluene 1093 and xylene 1083 were charged, and while stirring at a reaction temperature of 50'C, aniline 44.7s (0.48 mol) was added dropwise little by little over 1 hour. Allowed to react for minutes. Phosphorous pentoxide 6.89 and dimethylstearylamine'+, 5y were added to the resulting reaction mixture and the mixture was heated to 120-130 with stirring.
The reaction was continued for 5 hours while removing the produced water at 'C. After the reaction was completed, the mixture was cooled and distilled in the same manner as in Example 1 together with 6.9 y of barium carbonate (3.0 times equivalent to the acid I product in the distilled raw material) and 153 y of water. As a result, the melting point was 89.5-90
゜5°C, GPC purity 99% or more, acid 1i11i0.3
74.73 of N-phenylmaleimide (yield based on aniline: 90%) was obtained.

Examples 4 to 7 In Example 1, instead of aniline, 0.48 mol of various primary amines shown in Table 1 was used, and 5.
Core distillation was carried out in the same manner as in Example 1 except that 0q was used.

Table 1 shows the yield and analysis results for IH, N-phenylmale rmi 1.

Comparative Example 1 The same operation as in Example 19111 was carried out without adding the Ruito compound. The yield of the obtained N-phenylmaleimide based on aniline was 91%, but i+:1! :ff8
4.

5-86.5°C, purity 95.0″ by Gl)C,
The quality was poor, with an acid value of 6.3.

3≧) Sili 2 In Example 1, instead of calcium hydroxide, 3.1s of sodium hydroxide (2.0 times equivalent to the remaining acidic substance) was added, and the mixture was stirred at 80'C for 1 hour at 1j't. After purchase, 7
When the oil layer separated at 0°C was distilled, polymerization occurred midway, resulting in 10% of the target N-phenylmaleimide.
The yield was as low as:

[Effect of the invention] Decomposition of dicarboxylic monoamide produced during distillation and ＼-
Since polymerization of the substituted maleimide can be prevented, extremely pure N-substituted maleimide can be obtained in high yield with simple operations. Furthermore, since the acidic compounds remaining in the distilled raw material are neutralized, there is no fear of corrosion of the equipment during distillation.

Claims (2)

[Claims] (1) When purifying the N-substituted maleimide obtained by dehydrating dicarboxylic acid monoamide obtained from maleic anhydride and a primary amine in the presence of an acid or a compound that reacts with water to produce an acid, residual Purifying the acidic substance by contacting it with one or more basic substances selected from the group consisting of alkaline earth metal oxides, hydroxides, and carbonates before and/or during distillation. Characteristic method for producing high purity N-substituted maleimide. (2) A method for producing a high-purity N-substituted maleimide according to claim (1), which comprises bringing the remaining acidic substance and basic substance into contact in the presence of water.