JPH06184104A - Production of n-arylmaleimides - Google Patents

Abstract

PURPOSE:To carry out reduction of waste matter and improve economical efficiency and further suppress the formation of by-products difficult to separate and obtain an N-arylmaleimide in high yield by separating and recovering an acid catalyst and an aprotic polar solvent and repeatedly using the catalyst and the solvent. CONSTITUTION:In reacting maleic anhydride with an aromatic pirmary amine in an organic solvent including an aprotic polar solvent in the presence of an acid catalyst, the reaction is carried out by using the aprotic polar solvent and sulfuric acid as an acid catalyst which was previously dehydrated by azeotrope formation with the organic solvent. The molar ratio of the maleic anhydride to the aromatic primary amines to be supplied is kept usually 1.0-3.0, preferably 1.0-1.5 and the reaction is carried out at 80-170 deg.C, preferably 90-150 deg.C. After the reaction is finished, the acid catalyst and the solvent are extracted with water and are separated and recovered by concentration the water extract to provide the objective N-arylmaleimide represented by the formula (R<1> to R<5> are H, halogen, NO2, OH, COOH, 1-6C alkyl, alkoxy, phenyl or sulfonyl).

Description

Detailed Description of the Invention

[0001]

The present invention relates to ABS, PMMA, P
The present invention relates to a method for producing N-arylmaleimides in high yield, which is useful as a heat resistance improver for resins such as VC and as an intermediate for medicines and agricultural chemicals.

[0002]

2. Description of the Related Art Research on the production technology of maleimides has been conducted for a long time. As a method for producing maleimides, for example, JP-A-53-68770 discloses a maleamic acid obtained from maleic anhydride and an aromatic primary amine with an acid catalyst and an aprotic polar solvent such as dimethylacetamide. In a water-immiscible solvent in the presence of
A method for producing maleimides by reacting at high temperature is disclosed. Further, JP-A-63-122666 discloses that maleic anhydride is heated in an aromatic organic solvent containing an aprotic polar solvent such as dimethyl sulfoxide in the presence or absence of an acid catalyst at a temperature of 50 to 200 ° C. A method for producing maleimides by reacting with aromatic primary amines in a range is disclosed. However, according to these methods, the acid catalyst and the aprotic polar solvent used in the reaction are not recovered and become a large amount of industrial waste, which is an environmental problem.

[0003]

The object of the present invention is to reduce the amount of waste and improve the economical efficiency by separating and recovering the acid catalyst and the aprotic polar solvent, and repeatedly using them. By-products such as N-aryl-3-arylaminosuccinimide are suppressed, and N-aryl-3
It is to provide a method for producing an arylmaleimide.

[0004]

Means for Solving the Problems The inventors of the present invention have made earnest studies in view of the above-mentioned problems, and have obtained the following findings. When sulfuric acid is used as an acid catalyst without any treatment, it is a highly viscous residue that is difficult to remove and consists of maleic amic acid which is a reaction intermediate in the reaction process and an acidic component which is considered to be a decomposition product of the maleimides formed. Remain in the reactor and the reaction yield decreases. Furthermore, in the method of adding the aromatic primary amines under the reflux of the organic solvent containing maleic anhydride, the maleic anhydride is hydrolyzed by the water in the reaction system to become maleic acid and does not act as a reaction substrate. Instead, maleic anhydride is gradually distilled out of the reaction system together with water. As a result, it was found that maleic anhydride was deficient with respect to the aromatic primary amines, a large amount of N-aryl-3-arylsuccinimide and the like was by-produced, and the yield was reduced.

Based on these findings, sulfuric acid is used as an acid catalyst after dehydration treatment with an aromatic organic solvent, and maleic anhydride is constantly reacted with aromatic primary amines under reflux of this organic solvent. It was found that the N-arylmaleimides can be produced in good yield by adding them in an amount not less than the equivalent amount. Further, the aprotic polar solvent and the acid catalyst used in the reaction can be recovered not only by transferring them from the reaction solution to the aqueous phase by extracting with water at the end of the reaction and concentrating them, but also by repeating them. The inventors have found that they can be used and completed the present invention.

That is, according to the present invention, in producing N-arylmaleimides from maleic anhydride and aromatic primary amines in the presence of an acid catalyst in an organic solvent containing an aprotic polar solvent, an aprotic Using N-methyl-2-pyrrolidone, N, N-dimethylformamide or dimethylsulfoxide as the polar solvent, a step of azeotropic dehydration of sulfuric acid used as an acid catalyst with an organic solvent in advance, and a maleic anhydride aromatic group. The step of supplying so that the molar ratio to the one amine is always 1.0 to 3.0, the step of extracting the acid catalyst and the aprotic polar solvent with water after the reaction, The following general formula (1) including the step of concentrating the water extract containing

[0007]

[Chemical 2]

(Wherein R ¹ , R ² , R ³ , R ⁴ and R ⁵ are each independently a hydrogen atom, a halogen atom, a nitro group, a hydroxyl group, a carboxyl group, an alkyl group having 1 to 6 carbon atoms or an alkoxyl group. , Phenyl group and sulfonyl group)
And a step of azeotropically dehydrating the acid catalyst and aprotic polar solvent recovered in this method together with an organic solvent to completely remove water in the catalyst layer, maleic anhydride The step of supplying so that the molar ratio to the aromatic primary amines is always 1.0 to 3.0, the step of extracting the catalyst and the aprotic polar solvent from the reaction solution after completion of the reaction, and the water extraction It is a method for producing N-arylmaleimides, which comprises a step of concentrating a liquid to separate and collect an acid catalyst and an aprotic polar solvent.

The present invention will be described in detail below.

In the method of the present invention, first, the mixture of the acid catalyst and the organic solvent is azeotropically dehydrated. The acid catalyst means one containing H ₂ SO ₄ , and specifically, for example, concentrated sulfuric acid, diluted sulfuric acid,
Fuming sulfuric acid and the like can be mentioned, and it is preferable to use concentrated sulfuric acid from the viewpoint of easy handling and azeotropic dehydration treatment. The acid catalyst may be, for example, xylene sulfonic acid, toluene sulfonic acid, methane sulfonic acid, benzene sulfonic acid,
Sulfonic acids such as ethanesulfonic acid and octanesulfonic acid may be used in combination.

On the other hand, the organic solvent may be an organic solvent which is inactive with respect to the N-arylmaleimides and the reaction substrate and immiscible with water. Examples thereof include benzene, toluene, xylene, cumene, ethylbenzene, chlorobenzene, nitrobenzene, mesitylene, and anisole, and it is preferable to use toluene and xylene from the viewpoint of control of reaction temperature and easy removal of the solvent.
Further, the amount used is appropriately 1 to 7 times, preferably 1 to 4 times the weight of the aromatic primary amines.

[0012] In the above azeotropic dehydration, when using, for example, concentrated sulfuric acid as sulfuric acid, relative to H ₂ SO ₄ 1 mole of concentrated sulfuric acid, 1.1 mol to about 0.2 mol, more preferably 0. It is suitable to distill 4 to 1.1 mol of water from the viewpoint of increasing the yield of maleimides.
When dilute sulfuric acid is used as sulfuric acid, the amount of water distilled out is generally higher than the above amount.

Azeotropic dehydration is carried out, for example, at 70 to 180 ° C., preferably 80 to 160 ° C. for 10 to 90 minutes, preferably 1
It can be carried out by heating for 5 to 60 minutes, and it can be carried out not only at normal pressure but also under pressure or under pressure. In addition, it is preferable to carry out in an atmosphere of an inert gas such as nitrogen or argon.

If the amount of sulfuric acid used is too small, the reaction rate of imidization decreases, the reaction does not proceed sufficiently, and the reaction time tends to be long. Further, when the amount is too large, a large amount of by-products due to hydrolysis, polymerization and isomerization reaction tends to be generated, so 0.5 to 30 mol, preferably 1 to 100 mol of the aromatic primary amine as a raw material is used. It is suitable to use ~ 15 mol.

Examples of the aprotic polar solvent used in this reaction system include N, N-dimethylformamide and N
-Methyl-2-pyrrolidone, dimethyl sulfoxide and the like can be mentioned. The amount used is 0.5 to 40 mol, preferably 1 to 30 mol, per 100 mol of the aromatic primary amine. The aprotic polar solvent may be added all at once at the beginning or may be added continuously or intermittently. If the addition amount of the aprotic polar solvent is too large, the selectivity of the maleimides tends to decrease, and conversely, if it is too small, the reaction rate of the maleimides tends to decrease due to the decrease of the reaction rate.

In this reaction system, an inorganic copper salt such as copper (II) sulfate is used as a polymerization inhibitor, and the amount thereof is 0.0002 wt% to 5 wt%, preferably 0.001 wt% with respect to maleic anhydride. % To 1 wt%.

The aromatic primary amines used in this reaction are not particularly limited, and the aromatic ring has an alkyl group such as a methyl group and an ethyl group, an alkoxyl group such as a methoxy group and an ethoxy group. There is no problem even if it has a substituent such as a group, a nitro group, an amino group, a hydroxyl group, a carboxyl group, a sulfonyl group, a halogen such as fluoro, chloro and bromo.

Specifically, aniline, 2-chloroaniline, 3-chloroaniline, 4-chloroaniline, 4-fluoroaniline, 4-bromoaniline, 2-nitroaniline, 2-hydroxyaniline, 4-hydroxyaniline, 2-aminoaniline, 2,6-dichloroaniline,
4-methoxyaniline, 4-ethoxyaniline, 4-methylaniline, 2,6-dimethylaniline, 4-carboxyaniline, 2,4,6-trichloroaniline, 4
Examples thereof include sulfonylaniline and biphenylamine.

The other raw material, maleic anhydride, is
What is obtained from any source may be used, and the amount of maleic anhydride used is not particularly limited as long as it is 1: 3.0 in a molar ratio with respect to the aromatic primary amines. It is economical and desirable to use it at a molar ratio of preferably 1: 1.0 to 2.0, more preferably 1: 1.0 to 1.5. When the amount of maleic anhydride used is less than 1 in terms of molar ratio with respect to the aromatic primary amines, not only the yield of maleimides decreases due to the decrease in conversion but also N-aryl- which is difficult to purify. There is a tendency that many by-products such as 3-arylsuccinimide are produced.

The reaction conditions in this reaction are that the reaction temperature is 8
It is desirable that the temperature is 0 to 170 ° C, preferably 90 to 150 ° C. If the reaction temperature is too low, the reaction rate decreases, the reaction time increases, and the yield of maleimides decreases. On the contrary, when the reaction temperature becomes high, it becomes difficult to suppress the hydrolysis, polymerization and isomerization reactions, and the selectivity of maleimides decreases. Further, this reaction can be carried out not only under normal pressure but also under pressure or under reduced pressure within the above temperature range. The reaction can be preferably carried out under an atmosphere of an inert gas such as nitrogen or argon.

The method of the present invention is described in detail below.

In the method of the present invention, first, the acid catalyst and the organic solvent are heated under reflux for 0.5 to 1 hour for dehydration.
After the dehydration treatment, at least one selected from the above-mentioned aprotic polar solvents is added. The mixture is brought to reflux and maleic anhydride and aromatic primary amines are added simultaneously under reflux. At this time, it is added so that the molar ratio of the already added maleic anhydride to the already added aromatic primary amines is always 1 or more. The method of addition may be continuous or intermittent. Furthermore, the aromatic primary amines may be used as they are, or may be used after being dissolved in a solvent. Further, it is preferable to remove the condensed water generated along with the progress of the reaction to the outside of the system.

The maleic anhydride may be added as a solid as it is, but it is preferable that the maleic anhydride is melted as it is at 60 to 70 ° C. in advance or dissolved in a small amount of a solvent and added. The time required for addition is 0.5 to 8 hours, preferably 1 to 4 hours. When the addition time is short, a large amount of maleamic acid, which is a reaction intermediate, remains, and the reaction time after addition becomes long. When the addition time is long, the selectivity of the target maleimides decreases due to polymerization, hydrolysis and the like.
After the addition is completed, the reaction is completed by continuing the reflux.

The reaction time after the addition of the raw materials varies depending on the reaction temperature, but it is preferably about 0.5 to 2 hours. When the reaction time is shorter than this, the conversion rate becomes low.
On the contrary, if the reaction time is long, side reactions are likely to occur and the selectivity is lowered, such being undesirable.

After completion of the reaction, water is added to the reaction solution to separate it into an organic phase containing maleimides and an aqueous phase containing an acid catalyst and a polar solvent. At this time, the amount of water is 10 to 100 wt%, preferably 15 to 70 wt% with respect to the weight of the reaction liquid.
It is suitable to use the water. This separation operation 1
Repeat 5 times. If the amount of water used is large, the waste in the process of removing water afterwards becomes large, and if the amount of water is small, the acid catalyst and aprotic polar solvent cannot be extracted sufficiently, so a large amount of polar solvent is replenished for repeated use. It is necessary and uneconomical. The acid catalyst recovered at this time corresponds to 95 to 100% of the total amount of the acid catalyst used. Moreover, the polar solvent to be recovered is 85 to 1 with respect to the total amount of the polar solvent used.
Equivalent to 00%. When the recovered catalyst is reused, the reaction yield does not change significantly even if it is used as it is, but in order to use it repeatedly, the loss of the polar solvent, that is, the amount of 0 to It is desirable to carry out the reaction by adding 15%. Moreover, regarding the acid catalyst, there is no significant effect even if it is added or not. By removing water from the separated aqueous phase containing the acid catalyst and the polar solvent under reduced pressure, and further performing azeotropic dehydration with the organic solvent used in the reaction, it becomes possible to repeatedly use the acid catalyst and the polar solvent.

On the other hand, the organic phase after water extraction can be washed with dilute aqueous sodium hydrogen carbonate and then distilled to isolate N-arylmaleimides.

The general formula (1) obtained by the method of the present invention
Examples of N-arylmaleimides represented by
N-phenylmaleimide, N- (2-chlorophenyl)
Maleimide, N- (3-chlorophenyl) maleimide,
N- (4-chlorophenyl) maleimide, N- (4-fluorophenyl) maleimide, N- (4-bromophenyl) maleimide, N- (4-nitrophenyl) maleimide, N- (2-aminophenyl) maleimide, N -(2
-Hydroxyphenyl) maleimide, N- (4-hydroxyphenyl) maleimide, N- (4-methoxyphenyl) maleimide, N- (4-ethoxyphenyl) maleimide, N- (4-methylphenyl) maleimide, N-
(2,6-dichlorophenyl) maleimide, N- (2,
6-dimethylphenyl) maleimide, N- (4-carboxylphenyl) maleimide, N- (2,4,6-trichlorophenyl) maleimide, N- (2,4,6-trimethylphenyl) maleimide, N- (4- Examples thereof include sulfonylphenyl) maleimide and N-biphenylmaleimide.

[0028]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 500 equipped with thermometer, water separator, condenser and stirrer
90 ml of xylene and 0.53 ml of concentrated sulfuric acid were added to a 4-ml four-necked flask, and 0.4 ml of water produced by stirring and refluxing for 30 minutes at a temperature range of 130 to 135 ° C. under normal pressure was distilled out of the system by azeotropic distillation. . After heating to reflux and azeotropic dehydration, 80 ℃
And 7.2 ml of N-methyl-2-pyrrolidone and 50 mg of copper sulfate as a polymerization inhibitor (200 ppm with respect to maleic anhydride) are added, and the mixture is refluxed.
The temperature was raised to 30 to 135 ° C. After the start of reflux, 46.6 g (0.5 mo of aniline dissolved in 15 ml of xylene)
1) and 51.4 g (0.525 mol) of maleic anhydride dissolved in 20 ml of xylene were simultaneously added dropwise at a constant rate and the entire amount was added over 1.5 hours. Water generated by the reaction was distilled out of the reaction system together with xylene. After the addition of aniline and maleic anhydride was completed,
The reaction was continued under reflux for 5 hours.

After completion of the reaction, the reaction solution was washed twice with 50 ml of pure water (25 wt% based on the total weight of the reaction solution). After washing with water and further with dilute aqueous sodium hydrogen carbonate, xylene was removed from the organic phase under reduced pressure to obtain 87.7 g of a yellow solid crude crystal of N-phenylmaleimide.

Analysis by high performance liquid chromatography revealed that the crystals had a purity of 95.9 wt% and a yield of 97.1 mol%. At this time, the amount of maleic anhydride distilled out of the reaction system was 3.2 mol% with respect to the maleic anhydride used.

Example 2 The washing solution recovered in Example 1 was depressurized to remove water to recover the acid catalyst and N-methyl-2-pyrrolidone.
The reaction was repeated using the reaction apparatus used in. The recovered catalyst solution was azeotropically dehydrated with 90 ml of xylene for 30 minutes to completely remove water in the catalyst solution. After azeotropic dehydration, the mixture is allowed to cool to 80 ° C., 1.4 ml of N-methyl-2-pyrrolidone is added, and the mixture is refluxed 130 to 13
The temperature was raised to 5 ° C. After the start of refluxing, 46.6 g (0.5 mol) of aniline dissolved in 15 ml of xylene and 2
51.4 g maleic anhydride dissolved in 0 ml xylene
And (0.525 mol) were simultaneously added dropwise at a constant rate, and the whole amount was added dropwise over 1.5 hours. Water generated by the reaction was distilled out of the reaction system together with xylene. After the addition of aniline and maleic anhydride was completed, the reaction was continued under reflux for 0.5 hours.

After completion of the reaction, the reaction solution was washed twice with 60 ml of pure water. After washing with water and further with diluted sodium bicarbonate water, xylene was removed from the organic phase under reduced pressure to obtain a yellow solid N-.
87.7 g of crude phenylmaleimide crystals were obtained.

Analysis by high performance liquid chromatography revealed that the crystals had a purity of 95.9 wt% and a yield of 97.1 mol%. At this time, the amount of maleic anhydride distilled out of the reaction system was 3.0 mol% with respect to the maleic anhydride used.

Examples 3 to 5 The acid catalyst phase recovered in the same manner as in Example 2 was used up to 3 times to carry out the reaction. The results are summarized in Table 1.

[0036]

[Table 1]

[0037]

EFFECT OF THE INVENTION According to the method of the present invention, by-products which are difficult to separate can be suppressed, N-arylmaleimides can be produced in a high yield, and the polarities used in the reaction can be suppressed. Since the solvent and the acid catalyst are repeatedly used, it is possible to reduce waste and improve economical efficiency.

Claims (2)

[Claims] 1. An organic solvent containing an aprotic polar solvent,
In producing N-arylmaleimides from maleic anhydride and aromatic primary amines in the presence of an acid catalyst, an aprotic polar solvent is used, and sulfuric acid used as an acid catalyst is azeotroped with an organic solvent in advance. Step of dehydration, step of supplying so that the molar ratio of maleic anhydride to aromatic primary amines is always 1.0 to 3.0, after completion of reaction, acid catalyst and aprotic polar solvent are extracted with water And a step of concentrating an aqueous extract containing an acid catalyst and an aprotic polar solvent, the following general formula (1): (In the formula, R ¹ , R ² , R ³ , R ⁴ and R ⁵ are each independently a hydrogen atom, a halogen atom, a nitro group, a hydroxyl group, a carboxyl group, an alkyl group having 1 to 6 carbon atoms, an alkoxyl group, a phenyl group. And a sulfonyl group). 2. A step of azeotropically dehydrating the acid catalyst and the aprotic polar solvent recovered in claim 1 together with an organic solvent to completely remove water in the catalyst solution, and a maleic anhydride aromatic primary amine. Molar ratio to the class is always 1.0-3.0
So that the acid catalyst and the aprotic polar solvent are extracted from the reaction solution by water extraction after the reaction, the water extract is concentrated to remove the acid catalyst and the aprotic polar solvent. The method for producing N-arylmaleimides according to claim 1, comprising a step of separating and collecting.