JPH0427227B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing maleimides. Maleimide compounds are used as raw materials for resins, pharmaceuticals,
This compound is useful as a raw material for agricultural chemicals and the like, and the present invention provides an advantageous method for producing it.

[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, which is also disclosed in US Pat. No. 2,444,536. .

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 an equivalent amount of expensive acetic anhydride to maleamic acid in the imidization reaction, and also requires a large amount of water when separating and recovering maleimide produced from the liquid after the imidization reaction. As a result, a large amount of wastewater containing acetic acid is produced, which has the disadvantage of requiring a large amount of cost to detoxify it. For these reasons, this method is too expensive to industrially produce imide compounds.

Also, as in the specification of Japanese Patent Application Laid-Open No. 53-68770,
Maleic anhydride and an amine compound are reacted in an organic solvent, the resulting maleamic acid is isolated, and a dehydration ring-closing reaction is carried out in the coexistence of an aprotic polar solvent such as dimethylformamide or dimethyl sulfoxide and an acid catalyst. There is a way. However, this method requires a large amount of aprotic polar solvents such as expensive and toxic dimethylformamide, which increases the production cost of maleimide. There are problems such as increased loss due to deterioration of the solvent, and furthermore, it is difficult to remove these aprotic polar solvents from the product maleimide due to their high boiling points. Therefore, it cannot be said that it is an excellent method.

Furthermore, as disclosed in Japanese Patent Publication No. 51-40078, solvents such as toluene, xylene, and chlorobenzene having a boiling point of 80°C or higher and chlorosulfonic acid, p-toluenesulfonic acid, and benzenesulfone are used as diluents. There is also a method of carrying out thermal dehydration ring closure with an acid catalyst such as orthophosphoric acid, pyrophosphoric acid, phosphorous acid, etc., and distilling the water produced at this time out of the system by azeotropy with the solvent. Compared to the above two methods, this method not only does not require large amounts of expensive dehydrating agents such as acetic anhydride, but also
It is excellent in that the maleimide produced is easy to separate and recover.

However, this method uses relatively many expensive acid catalysts such as chlorosulfonic acid, p-toluenesulfonic acid, benzenesulfonic acid, orthophosphoric acid, pyrophosphoric acid, phosphorous acid, etc. The yield is also low and it is not economically satisfactory as an industrial production method.

On the other hand, JP-A-54-30155 discloses a method for producing oligoimides using a mixture of an inorganic or organic acid-containing acid and a quaternary ammonium salt of this acid as a catalyst.

However, the quaternary ammonium salt used in combination with an acid catalyst in this method is an ammonium salt in which the nitrogen atom is substituted at least twice, such as dimethyldialkyl ammonium methanesulfonate, methanesulfonic acid, tetraoctylammonium, etc. is an expensive phase transfer catalyst. Therefore, the use of such compounds is too expensive.

In this method, it is essential to limit the ratio of the acid catalyst to the quaternary ammonium salt within a certain range in order to maintain a good imidization yield. However, since the ratio of these catalysts changes once used in the reaction, it is not possible to obtain a good imidization yield even if the catalyst is used again as it is.

Therefore, in order to use the catalyst again, there is a problem in that a great deal of effort is required to maintain and manage the catalyst activity, such as refining and adjusting the catalyst.

[Problem that the invention seeks to solve]

As described above, the currently existing methods for producing maleimides have many problems and are not satisfactory for industrial implementation.

Thus, an object of the present invention is to provide a method for producing maleimides with higher purity in a complete and simple manner and at low cost compared to the above-mentioned methods.

[Means for solving problems]

The present inventors have long continued research on synthetic reactions of maleimides. As a result of intensive studies on catalysts used in the ring-closing imidization reaction, we have found that the amine salt produced by the neutralization reaction between the raw material amine of maleimides and an acid has extremely high selectivity for the ring-closing imidization reaction. They discovered that it exhibits catalytic action and completed the present invention.

Conventionally, it was believed that an oxygen-containing acid was indispensable during the ring-closing imidization reaction, and the sole use of an amine salt produced by a neutralization reaction with such an acid had a significant catalytic effect on the ring-closing imidization reaction. It's totally amazing to have.

That is, the present invention involves mixing maleamic acid with water in the presence of an amine salt produced by a neutralization reaction between an amine used as a raw material during the production of maleimides and an inorganic or organic monobasic acid or polybasic acid. This is a method for producing maleimides, which is characterized by heating in an azeotropic organic solvent and performing ring-closing imidization while removing water generated during the reaction from the system as a mixture with the organic solvent.

The most characteristic feature of the present invention is that in the ring-closing imidization reaction, sulfuric acid, orthophosphoric acid, pyrophosphoric acid,
Instead of acid catalysts such as p-toluenesulfonic acid, ammonium salts produced by the neutralization reaction between amines used as raw materials during the production of maleimides and inorganic or organic monobasic acids or polybasic acids are used. It is used as a catalyst.

Further, in some cases, a metal-containing compound or a stabilizer may be present in the ring-closing imidization reaction.

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 the formula, R is selected from an alkyl group having 1 to 20 carbon atoms, a phenyl group, a benzyl group, a cyclohexyl group, a pyridyl group, a quinolyl group, and those in which these groups are substituted with halogen, carboxyl group, or nitro group. It is also possible. 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,
sec-butylamine, tert-butylamine, n-
hexylamine, n-dodecylamine, allylamine, benzylamine, cyclohexylamine,
Aniline, nitroaniline, aminophenol,
Aminobenzoic acid, anisidine, ethoxyphenylamine, monochloroaniline, dichloroaniline, toluidine, xylidine, ethylaniline, etc.

The synthesis of maleamic acid takes place almost stoichiometrically, with 1 mole of maleic anhydride producing 1 mole of amine.
mol is preferred, but 0.8 to 1.5 mol, preferably 0.9 to 1.5 mol
It is possible to react within the range of 1.2 mol. 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, and side reactions may be generated in the imidization reaction. The above range is preferable since a large amount of substances are produced and the yield of the imidization reaction becomes low.

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, petroleum distillate with a boiling point of 50 to 120°C. , xylenes, ethylbenzene, isopropylbenzene, cumene, mesitylene, tert-butylbenzene, pseudocumene, trimethylhexane, octane, tetrachloroethane, nonane, chlorobenzene, ethylcyclohexane, boiling point 120
~170℃ petroleum fraction, m-dichlorobenzene, sec
-Butylbenzene, p-dichlorobenzene, decane, p-cymene, o-dichlorobenzene, butylbenzene, decahydronaphthalene, tetrahydronaphthalene, dodecane, naphthalene, cyclohexylbenzene, petroleum distillates with a boiling point of 170-250°C, etc. There is. The amount of this solvent to be used is 1 to 20 times the amount (volume) of maleamic acid, preferably 3 times the amount (volume) of the maleamic acid, in order to perform the reaction smoothly and satisfy economic conditions.
~7 times the amount used.

Further, a maleimide having a boiling point suitable for the reaction conditions is selected while taking into account the solubility, price, ease of handling, etc. of the maleimide. Furthermore, when considering the separation of the maleimides 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 a catalyst, sulfuric acid, p-toluenesulfonic acid,
It is obtained by neutralizing inorganic or organic monobasic acids or polybasic acids such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, benzenesulfonic acid, trichloroacetic acid, etc. and amines, which are raw materials for the production of maleimides. A prepared amine salt is used.
In these amine salts, at least one proton of the monobasic acid or polybasic acid must be replaced with an amine.

In addition, the amount used is 2 to 2 to maleamic acid.
The amount is 400 mol%, preferably 20 to 200 mol%.

Further, depending on the case, a metal-containing compound and a stabilizer may be allowed to coexist in the reaction.

Since the amine salt produced as described above does not dissolve in the organic solvent used in the present invention, the reaction system is essentially separated into two layers: an organic layer and a catalyst layer. This state is the same during the reaction and at the end of the reaction, and in addition, the amine salt as a catalyst does not substantially change before and after the reaction. Therefore, the amine salt itself can be used as it is without being recovered or purified in the next reaction.

When using this catalyst layer for the next reaction, the organic layer after the reaction and the catalyst layer may be separated at a temperature in the range of 120 to 250°C and the catalyst layer may be used as it is for the next reaction, or the catalyst layer may be used as it is for the next reaction. The layer may be mixed with 5 to 20% water by weight to lower the temperature and viscosity and may be added in the form of an aqueous solution for easy handling.

Further, depending on the case, a metal-containing compound or a stabilizer may be allowed to coexist in the reaction system for the reaction. At least one metal-containing compound used at this time is selected from the group consisting of zinc, chromium, palladium, cobalt, nickel, iron, and aluminum.
Among these, zinc acetate is particularly effective. The amount of these used is 0.05 to 0.5 as metal per 1 mole of maleamic acid.
It is mol%, preferably 0.01 to 0.1 mol%.

Furthermore, as a stabilizer, methoxybenzoquinone,
p-methoxyphenol, phenothiazine, hydroquinone, alkylated diphenylamines, methylene blue, tert-butylcatechol, tert-
Butylhydroquinone, zinc dimethyldithiocarbamate, copper dimethyldithiocarbamate, copper dibutyldithiocarbamate, copper salicylate, thiodipropionic acid esters, mercaptobenzimidazole, triphenylphosphite, alkylphenols, alkylbisphenols, and the like are used.

The effects of these stabilizers play a role in allowing the maleimide produced by the imidization reaction to exist stably without deterioration even under the high temperature of the imidization reaction.

As for the amount added, adding a trace amount will have little effect, and conversely, adding an excessive amount is not desirable because it may cause a problem of mixing into the product. Therefore, the amount of these used is 0.005 to 0.5 mol%, preferably 0.05 to 0.3 mol%, based on 1 mol of maleamic acid.
It is mole%.

As a method of carrying out the present invention, first, an amine compound is added to a solution of maleic anhydride in an organic solvent,
Maleamic acid is obtained by reacting at 150°C or lower, preferably 30-120°C, for 15-120 minutes. Next, the above salt catalyst or the salt catalyst layer separated from the reaction system is added without isolating the maleamic acid, and optionally a metal-containing compound and/or stabilizer is added, and the temperature is heated at 120 to 250°C. Maleimides can be produced in high yield by heating preferably at 130 to 220°C for 1 to 15 hours and carrying out the reaction while distilling the produced water out of the system by azeotropic distillation.

The present invention has been described above, and the advantages obtained by the present invention are as follows.

The amine salt produced by the neutralization reaction between amines, which are raw materials for the production of maleimides, and an inorganic or organic monobasic acid or polybasic acid has a highly selective catalytic effect on the ring-closing imidization reaction. Therefore, highly pure maleimides can be obtained in high yield.

Since the amine salt used as a catalyst is stable and can be used repeatedly in the reaction, the cost of the catalyst can be almost ignored.

Since the catalyst is used repeatedly, there is virtually no need to treat the used catalyst to make it non-polluting, and since it is a closed system, there is no need to worry about environmental problems due to catalyst disposal.

As described above, maleimides can be produced cheaply, safely and easily.

The present invention will be explained in more detail below using anhydrides.

Example 1 Ortho-xylene 100 in a 300 c.c. Meyer flask
g and 60 g of sulfuric acid were dispersed. Next, while cooling the Mayer flask in a water bath, 122 g of cyclohexylamine was added dropwise to obtain a white crystal xylene slurry solution of dicyclohexylamine sulfate salt.

On the other hand, 100 g of ortho-xylene was charged into a flask equipped with a thermometer, a cooling tube equipped with a water separator, a dropping funnel, and a stirrer, and 100 g of maleic anhydride was added to the flask.
was added to raise the temperature inside the flask to 100°C to dissolve maleic anhydride.

Next, a solution of 100 g of cyclohexylamine dissolved in 600 g of ortho-xylene was added dropwise in its entirety over 1 hour with stirring to synthesize a slurry of N-cyclohexylmaleamic acid in the above solvent.

Next, add the entire amount of the above amine salt slurry solution to this slurry liquid, heat it and keep it at 147°C with stirring.
The reaction was allowed to proceed for 2 hours while water produced by the reaction was distilled out of the system together with the solvent. 147℃ after completion of reaction
The catalyst layer separated from the reaction solution as a lower layer was separated and removed.

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, 10mmHg from the organic layer is removed.
The solvent of (abs) was distilled off under reduced pressure.

Next, 0.3 g of copper dibutyl dithiocarbamate was newly added to the flask, and N-
Distillation of cyclohexylmaleimide was carried out. As a result, 168 g of bright white crystals of N-cyclohexylmaleimide were obtained. The purity of this stuff is 99.8
The yield is 92.8 mol% based on the raw material cyclohexylamine.

Subsequently, the reaction procedure was repeated in exactly the same manner except that the catalyst layer separated from the reaction system was used, and 169 g of bright white crystals of N-cyclohexylmaleimide were obtained. The purity of this stuff is 99.8% by weight
The yield corresponds to 93.3 mol% based on the raw material cyclohexylamine.

Example 2 Ortho-xylene 100 in a 300 c.c. Meyer flask
g and 60 g of orthophosphoric acid were dispersed. Next, while cooling the Mayer flask in a water bath, 61 g of cyclohexylamine was added dropwise to obtain a white crystal xylene slurry solution of orthophosphoric acid monocyclohexylamine salt.

On the other hand, 100 g of ortho-xylene was charged into a flask equipped with a thermometer, a cooling tube equipped with a water separator, a dropping funnel, and a stirrer, and 100 g of maleic anhydride was added to the flask.
g was added thereto, the temperature inside the flask was raised to 100°C, and the maleic anhydride was dissolved.

Then, a solution of 100 g of cyclohexylamine dissolved in 600 g of ortho-xylene was added dropwise over 1 hour while stirring to synthesize a slurry of N-cyclohexylmaleamidic acid in ortho-xylene.

Next, the entire amount of the above amine salt slurry and 0.1 g of copper dibutyldithiocarbamate were added to this slurry, heated and kept at 143°C with stirring, while distilling water produced by the reaction out of the system together with ortho-xylene. The reaction was allowed to proceed for 7 hours. 143 after completion of reaction
The catalyst layer separated into the lower layer from the reaction solution was separated and removed at °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, 10mmHg from the organic layer is removed.
(abs) and ortho-xylene was distilled off under reduced pressure.

Next, 0.3 g of copper dibutyl dithiocarbamate was newly added to the flask, and N-
Distillation of cyclohexylmaleimide was carried out. As a result, 168 g of bright white crystals of N-cyclohexylmaleimide were obtained. The purity of this stuff is 99.8
% by weight, and the yield corresponds to 90.0 mol% based on the raw material cyclohexylamine.

Next, the reaction operation was repeated in exactly the same manner except that the catalyst layer separated from the reaction system was used as a catalyst, and 164 g of bright white crystals of N-cyclohexylmaleimide were obtained. The purity of this thing is
The yield was 99.8% by weight, corresponding to 90.6% by mole based on the raw material cyclohexylamine.

Example 3 100 g of P-cymene and 10 g of orthophosphoric acid were dispersed in a 300 c.c. Meyer flask. Next, while cooling the Mayer flask in a water bath, aniline 9.5
g was added dropwise to obtain a white crystal slurry solution of monoaniline orthophosphoric acid salt.

On the other hand, one glass flask was equipped with a thermometer, a stirrer, and a water separator.

Next, 53 g of maleic anhydride powder was added to P-cymene 50
The solution dissolved in g was charged into the above flask.
Next, the temperature inside the flask was adjusted to 130°C, and a solution prepared by dissolving 50 g of aniline in 400 g of P-cymene was added little by little over 30 minutes to synthesize a slurry liquid of N-phenylmaleamic acid.

To the thus obtained slurry liquid, the entire amount of the above amine salt slurry, 0.034 g of zinc acetate, and 0.065 g of p-methoxyphenol were added, and the reaction was carried out for 3 hours at a temperature of 180° C. while distilling off the produced water together with P-cymene. . After that, cool to 30℃, wash with water, and
- Cymene was distilled off under reduced pressure to obtain 94.0 g of N-phenylmaleimide crystals. The purity of this crystal was determined by liquid chromatography to be 93.7% by weight, corresponding to a yield of 94.7% by mole to amine.

Subsequently, the reaction operation was repeated in exactly the same manner except that the catalyst layer separated from the reaction system was used, and 95.0 g of N-phenylmaleimide crystals were obtained.

The purity of this crystal was determined by liquid chromatography to be 93.2% by weight, corresponding to a yield of 95.2% by mole to amine.

Comparative Example 1 99.2 g of cyclohexylamine was added to a solution of 98 g of maleic anhydride dissolved in 500 g of toluene with stirring.
It was added dropwise at 50-70°C. Stir for 2 hours after completion of dropping,
N-cyclohexylmaleamic acid was obtained. Subsequently, 14 g of methanesulfonic acid, 8.7 g of methanesulfonic acid-N-cyclohexylmaleamide, and 15 g of N-methylpyrrolidone were added to this solution, and the resulting water was refluxed at 115°C for 3.5 hours as an azeotropic distillate with toluene. I reacted while removing it.

Thereafter, 15 g of acetic anhydride was added and the mixture was allowed to react for 30 minutes, after which the temperature was lowered to 60° C. and the reaction mixture was filtered to remove insoluble impurities, catalyst, unreacted N-cyclohexylmaleamic acid, and the like. followed by liquid
200 g of water was added, stirred and washed with water for 30 minutes, and the aqueous layer was separated. After repeating this operation twice, toluene was distilled off from the organic layer under reduced pressure of 30 mmHg (abs), yielding 172 g of a colored solid containing cyclohexylmaleimide. According to GPC analysis, the content of N-cyclohexylmaleimide was 10.0% by weight, and the yield of N-cyclohexylmaleimide was 9.6% by mole based on cyclohexylamine. The results of gas chromatography analysis of the reaction solution also showed similar yields.

Comparative Example 2 In the method of Comparative Example 1, 73 g of n-butylamine was used instead of cyclohexylamine, 14 g of methanesulfonic acid and 8.4 g of methanesulfonic acid tributylamine salt were used as reaction catalysts, and N was used as a polar solvent.
The reaction was carried out in exactly the same manner except that dimethylformamide was used in place of methylpyrrolidone, and 151 g of a colored oily liquid containing N-n-butylmaleimide was obtained.

According to GPC analysis, the content of N-n-butylmaleimide was 13.4% by weight, and the yield was 13.2% by mole based on the raw material n-butylamine.

Furthermore, analysis by gas chromatography of the reaction solution after washing with water revealed that the yield was similar.

Comparative Example 3 43.1g of maleic anhydride was mixed with 331.8g of chlorobenzene.
39.7 g of cyclohexylamine in a solution dissolved in
was added and reacted at 40°C for 1 hour.

Dimethylacetamide 12 was added to the resulting slurry of N-cyclohexylmaleamide acid.
cc and 2 g of trichloroacetic acid were added, heated to 135°C, and reacted for 6 hours while removing water produced by the reaction together with the solvent.

After the reaction was completed, 402 g of the reaction solution was collected. Analysis of N-cyclohexylmaleimide in this reaction solution by gas chromatography revealed that it contained 2.2% by weight of N-cyclohexylmaleimide.

The yield of N-cyclohexylmaleimide was equivalent to 12.3 mol% based on the raw material cyclohexylamine.

Claims (1)

[Claims] 1. When producing maleimides by subjecting maleamic acid obtained from maleic anhydride and amines to a dehydration ring-closing reaction, an amine salt obtained from the amine and an inorganic or organic acid is used as a catalyst. A method for producing maleimides, which comprises heating maleamic acid in an organic solvent capable of azeotroping with water, and performing ring-closing imidization while discharging the generated water out of the reaction system together with the organic solvent. 2 amine salt to raw maleamic acid
The method according to claim 1, characterized in that the amount is present in a range of 400 mol %. 3. The method according to claim 1 or 2, wherein the heating temperature is in the range of 120 to 250°C.