JPS6263561A - Production of maleimide - Google Patents

Abstract

PURPOSE:To obtain a maleimide at a low cost, by cyclizing and imidating a maleinamic acid in the presence of an acid catalyst in an organic solvent capable of forming an azeotropic mixture with water within a specific temperature range wile removing the formed water as a mixture thereof with the organic solvent to the outside of the system. CONSTITUTION:A maleinamic acid expressed by the formula (R is alkyl, phenyl pyridyl, etc.) is cyclized in the presence of 10-30mol%, based on the raw material, acid catalyst, e.g. sulfuric acid or pyrophosphoric acid, in an organic solvent capable of forming an azeotropic mixture with water, e.g. benzene or octane, while heating at 200-250 deg.C for 1-15hr to afford the aimed maleimide. The formed water is removed to the outside of the system by azeotropic distillation. USE:A raw material for resins, medicines and agricultural chemicals.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing maleimides.

Maleimide compounds are useful compounds as raw materials for resin raw materials, medicines, agricultural chemicals, etc., and the present invention provides an advantageous method for producing them.

[Conventional technology]

Methods for producing maleimides have been studied for a long time.

The most common method is to produce maleimide by dehydrating maleamic acid using a dehydrating agent such as acetic anhydride, for example, as disclosed in US Pat.
It is also disclosed in the specification of No. 36.

That is, it is a method in which maleic anhydride and an amine compound are reacted, and the resulting maleamic acid is dehydrated and ring-closing imidized in the presence of acetic anhydride and sodium acetate. This method requires more than the equivalent amount of expensive acetic anhydride to maleamic acid in the imidization reaction, and also requires a large amount of water to separate and recover the maleimide produced from the liquid after the imidization reaction. Therefore, it has the drawback that it requires a large amount of cost to treat the wastewater containing acetic acid. For these reasons, this method is too expensive to industrially produce imide compounds.

On the other hand, a method that does not use a chemical dehydrating agent such as acetic anhydride is disclosed in Japanese Patent Publication No. 51-40078 and No. That is, thermal dehydration and ring closure are carried out with a solvent such as toluene, xylene, or chlorobenzene having a boiling point of 80°C or higher as a diluent and an acid catalyst such as sulfur trioxide, sulfuric acid, orthophosphoric acid, and the water produced at this time is subjected to azeotropic reaction with the solvent. This method involves distilling it out of the thread. This method is superior to the method using acetic anhydride in that it not only does not require an expensive dehydrating agent such as acetic anhydride, but also that the maleimide produced is easy to separate and recover.

However, a major problem is that the yield of the imidization reaction is lower than that of the method using acetic anhydride.

The reason for this is that compared to the imidization method using acetic anhydride, the above method of thermal dehydration in a solvent is more likely to cause side reactions due to the high reaction rate, and therefore maleimide containing many impurities is The only thing that can be changed is
Furthermore, this is thought to be due to the fact that the generated maleimide itself is thermally unstable, causing the generated maleimide to deteriorate during the reaction.

Also, as in the specification of JP-A No. 53-68770,
Maleic anhydride and an amine compound are reacted in an organic III medium, and the resulting maleic acid amide is subjected to a dehydration ring-closing reaction in the coexistence of an aprotic polar solvent such as dimethylformamide or dimethyl sulfoxide and an acid catalyst without isolating the maleic acid amide. There is a way.

According to this method, the yield is improved compared to the second method. However, the manufacturing cost of maleimide is high due to the use of a large amount of expensive and toxic aprotic polar solvents such as dimethylformamide, and the effects of the acid catalyst used in the reaction deteriorate the quality of solvents such as dimethylformamide. However, due to the high boiling point of these aprotic polar solvents, it is difficult to remove them from the maleimide product. .

[Problem that the invention seeks to solve]

In this way, the currently existing methods for producing maleimides are
Many problems have been pointed out, and it is not satisfactory for industrial implementation.

The purpose of the present invention is to provide a method for producing maleimides that satisfies the following requirements: (1) It is a safe and simple method; (2) Maleimides with high purity can be obtained; and (3) maleimides can be produced at low cost. That's true.

[Means for solving problems]

The present inventors have long continued research on synthetic reactions of maleimides. If the dehydration ring-closing reaction of maleamic acid is carried out in one reaction above 200°C and below 250°C, the rate of the ring-closing reaction becomes faster, so the selectivity of maleamic acid to maleimides is significantly increased. They found that the present invention can be improved significantly and completed the present invention.

That is, the present invention provides a method for heating maleamic acids at temperatures exceeding 200°C in the presence of an acid catalyst in an organic solvent capable of azeotroping with water.
This is a method for producing maleimides, characterized by carrying out ring-closing imidization while removing produced water from the system as a mixture with the organic solvent at a temperature of 50° C. or lower.

The most distinctive feature of the present invention is that the ring-closing imidization reaction is carried out at a high temperature of more than 200°C and less than 250°C.

Japanese Patent Publication No. 51-40078, Japanese Patent Publication No. 60-112758
As described in the title, it has conventionally been thought that it is more advantageous to carry out the ring-closing imidization reaction of maleamic acid at a relatively low temperature of 80 to 200°C, preferably 80 to 150°C. Ta. However, according to the findings of the present inventors, contrary to conventional wisdom, it has been found that when producing N-substituted maleimides, the yield is improved when the reaction is carried out at a high temperature exceeding 200°C.

It has been found that this effect is particularly noticeable in maleimides having aliphatic substituents such as methylmaleimide, apyrmaleimide, butylmaleimide, laurylmaleimide, cyclohexylmaleimide, and the like.

The maleamic acid used in the present invention is usually easily obtained by the reaction of maleic anhydride and primary amines, and is represented by the following general formula.

In particular, the following primary amines are suitable as raw materials for the maleamic acid used in the present invention.

Methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, 5ec-butylamine, tert-butylamine, n-hexylamine, n-dodecylamine, allylamine, benzylamine, cyclohexylamine, aniline, nitroaniline,
Aminophenol, aminobenzoic acid, anisidine, ■toxyphenylamine, monochloroaniline, dichloroaniline, toluidine, xylidine, ethylaniline, etc.

Maleamic acid can be synthesized almost stoichiometrically by reacting 0.8 to 1.5 moles, preferably 0.9 to 1.2 moles, of amine per mole of maleic anhydride. If the amine compound is in excess of maleic anhydride, it is necessary to use a larger amount of acid catalyst than necessary when directly subjecting it to the imidization reaction. Since a large amount of reaction products are produced and the yield of the imidization reaction becomes low,
The above range is preferable.

Furthermore, the organic solvent used in the present invention is preferably a solvent that can azeotropically remove the water produced in the dehydration ring-closing reaction, is inert, and does not participate in the reaction, such as benzene, toluene, xylenes, ethylbenzene, isopropylbenzene, cumene, etc. , mesitylene, tert-butylbenzene,
Pseudocumene, trimethylhexane, octane, tetrachloroethane, nonone, chlorobenzene, ethylcyclohexane, petroleum fraction with boiling point 120-170'C, m
-Dichlorobenzene, 5ec-butylbenzene, p-dichlorobenzene, decane, p-cymene, O-dichlorobenzene, butylbenzene, decahydronaphthalene, tetrahydronaphthalene, dodecane, naphthalene, cyclohexylbenzene, boiling point 170-250 There are petroleum distillates etc. at ℃. Use of this solvent a facilitates the reaction,
In addition, from the viewpoint of satisfying economic conditions, it is used 1 to 20 times as much, preferably 3 to 7 times, as much as maleamic acid.

In addition, 1. A reimide having a boiling point suitable for the reaction conditions is selected while taking into consideration the solubility, price, ease of handling, etc. of the reimide. Furthermore, when considering the separation of the maleimide from the solvent after the reaction is completed, it may be advantageous to use a low boiling point solvent and carry out the reaction under pressure.

As the acid catalyst, sulfuric acid, sulfuric anhydride, p-toluenesulfonic acid, orthophosphoric acid, metaphosphoric acid, birophosphoric acid, etc. are used.

Use E is added in an amount of 2 to 80 mol %, preferably 10 to 30 mol %, based on maleamic acid.

In the actual droplet method of the present invention, first, an amine compound is added to a solution of maleic anhydride in an organic solvent, and the temperature is lower than 150°C.
Maleamic acid is obtained by reacting preferably at 30 to 120°C for 15 to 120 minutes. then adding the acid catalyst without isolating the maleamic acid,
Maleimides can be produced in high yield by heating at 200 to 250° C. for 1 to 15 hours and carrying out the reaction while distilling the produced water out of the system by azeotropic distillation.

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

Example 1 An 11 glass flask was fitted with a meter, a stirrer and a water separator.

Next, a solution in which 53 g of maleic anhydride powder was dissolved in 50 (l) of tetrahydronaphthalene was charged into the flask.Next, the temperature inside the flask was adjusted to 90°C, and a solution in which 50 g of aniline was dissolved in 400 g of tetrahydronaphthalene was charged. was added little by little over 30 minutes to synthesize a tetrahydronaphthalene slurry of N-phenylmaleamic acid.The yield of N-phenylmaleamic acid was 99.
4 mole % to aniline.

10 g of orthophosphoric acid was added to the slurry liquid thus obtained, and the mixture was reacted at 210° C. for 3 hours.

Thereafter, the mixture was cooled to 30° C., washed with water, and tetrahydronaphthalene was distilled off under reduced pressure to obtain 78 g of N-phenylmaleimide crystals. The purity of this crystal was measured by liquid chromatography and was found to be 87.3 i4 ff.
1%, and the yield of this product is 7% based on the raw material aniline.
This corresponds to 3.2 mol%.

Comparative Example 1 A reaction was carried out under exactly the same conditions as in Example 1, except that tetrahydronaphthalene was changed to ortho-xylene and the reaction temperature was changed to 140°C once. 82 g of N-phenylmaleimide crystals were obtained.

The purity of this crystal was measured by liquid chromatography and was found to be 74.8% by weight, corresponding to a yield of 65.9% by mole based on the raw material aniline.

Example 2 Petroleum fraction 10 containing 98% or more of aromatic hydrocarbons with a boiling point in the range of 180 to 220° C.
0 g was charged, maleic anhydride M1000 was added thereto, and the temperature inside the flask was raised to 100° C. to dissolve the maleic anhydride.

Next, 100 g of cyclohexylamine was added to 600 g of the above solvent.
A total of 0 drops of a solution of Q was added under stirring in 1 hour to obtain N-
A slurry of cyclohexylmaleamic acid in the above solvent was synthesized.

Next, Ortholin FIf60C) was added to the slurry liquid, heated and maintained at 210° C. with stirring, and reacted for 2 hours while distilling water produced by the reaction out of the system together with the solvent. After the reaction was completed, the lower acid catalyst layer was separated and removed from the reaction solution at 200°C.

Subsequently, the temperature of the reaction solution was lowered to 60° C., 100 g of water was added, and the mixture was stirred and washed with water for 30 minutes, and the aqueous layer was separated.

After repeating this operation twice, 5 tt from the organic layer
m HQ (abs) (7) Under reduced pressure s W is distilled off b
T.

Next, 0.3 g of copper dibutyldithiocarbamate was newly added to the flask, and N
- Distillation of cyclohexylmaleimide was carried out. As a result, 1370 N-cyclohexylmaleimide with bright white crystals was obtained.

The purity of this product was 99.8% by weight, and the yield was equivalent to 75.7% by mole based on the raw material cyclohexylamine.

Example 3 The same reactor as in Example 2 was used. This flask was charged with ortho-xylene 100Q, and anhydrous maleic 11
000 was added and the temperature inside the flask was raised to 110° C. to dissolve maleic anhydride.

Then, a solution of 100 g of cyclohexylamine dissolved in 400 g of ortho-xylene was added dropwise over 30 minutes with stirring to synthesize a slurry of N-cyclohexylmaleamic acid in the above solvent. Next, 40° of orthophosphoric acid was added to the slurry liquid, heated, and reacted at 220° C. for 1 hour under a pressure of 5 atm. After the reaction was completed, the lower acid catalyst layer was separated and removed from the reaction solution at 140°C.

Subsequently, the temperature of the reaction solution was lowered to 60° C., 100 g of water was added, and the mixture was stirred and washed with water for 30 minutes, and the aqueous layer was separated.

After repeating this operation twice, remove 5 mm from the organic layer.
The solvent was distilled off under reduced pressure of l-1(J (abs)).

Next, 0.3a of copper dibutyl didiochlorbamate was newly added to the flask, and N
- Distillation of cyclohexylmaleimide was carried out. As a result, 148 g of N-cyclohexylmaleimide with bright white crystals was obtained.

The concentration of this product was 99.8% by weight, and the yield was equivalent to 81.9% by mole based on the starting material cyclohexylamine.

Comparative Example 2 Example 1 was carried out under the same conditions as in Example 1, except that the pressure was normal pressure and the reaction temperature was 147° C. to obtain 93 g of N-cyclohexylmaleimide.

The purity of this product was 99.8% by weight, and the yield was equivalent to 51.57% based on the raw material cyclohegycylamine.

Claims (1)

[Claims] (1) Maleamic acid is removed from the system as a mixture with the organic solvent in the presence of an acid catalyst in an organic solvent capable of azeotroping with water at a temperature exceeding 200°C and below 250°C. A method for producing maleimides, which comprises ring-closing imidization.