JPS6383065A - Production of maleimides - Google Patents

Abstract

PURPOSE:To obtain maleimides in high selectivity, by subjecting a maleamic acid obtained from maleic anhydride and amines to dehydrocyclization using a mixture of a salt of said amines and an acid and an acid as a catalyst in a specific solvent, on the dehydrocyclization of said maleamic acid. CONSTITUTION:When a maleamic acid obtained from maleic anhydride and amines is subjected to dehydrocyclization to produce maleimide useful as a raw material of resin and a raw material of medicine, agricultural chemicals, etc., above-mentioned raw material (maleamic acid) is subject to ring-closing imidation using a mixture containing >=40mol% (A) amine salt obtained from above-mentioned amines and an inorganic or organic acid and (B) an inorganic or organic acid in an amount of 2-40mol% based on above-mentioned raw material as a catalyst in an inert organic solvent insoluble in water or incapable of blending with water while heating at 120-250 deg.C to safely, readily attain the aimed compound in high purity and yield and at low cost.

Description

[Detailed description of the invention] [Industrial application field] 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 the same.

[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, 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 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 this reason, this method must be said to be an extremely expensive method for industrially producing imide compounds.

Also, as in the specification of JP-A No. 53-68770,
A method of reacting maleic anhydride with an amine compound in an organic solvent and carrying out 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 maleamic acid produced. There is also.

However, this method uses a large amount of expensive and toxic aprotic polar solvents such as dimethylformamide, which increases the production cost of maleimide, and the acid catalyst used in the reaction does not produce dinomethylformamide. These problems include problems such as deterioration of the solvents, resulting in large losses, and the difficulty of removing these aprotic polar solvents from the product maleimide due to their high boiling points. However, it cannot be said that it is an excellent method.

Furthermore, as disclosed in Japanese Patent Publication No. 51-40078, solvents such as notatoehatoluene, xylene, and chlorobenzene, which have a boiling point of 80° C. or higher, and chlorosulfonic acid, p-)luenesulfonic acid, and benzene are used as diluents. There is also a method in which thermal dehydration ring closure is performed together with an acid catalyst such as sulfonic acid, orthophosphoric acid, pyrophosphoric acid, or phosphorous acid, and the water produced at this time is distilled out of the thread by azeotropy with a solvent. This method is superior to the above two methods in that it not only does not require a large amount of an expensive dehydrating agent such as acetic anhydride, but also that the maleimide produced is easy to separate and recover.

However, in this method, chlorosulfonic acid,
A relatively large amount of expensive acid catalysts such as P-toluenesulfonic acid, benzenesulfonic acid, orthophosphoric acid, pyrophosphoric acid, phosphorous acid, etc. are used, and the yield of maleimides is low, making it economical for industrial production. It is not completely satisfying.

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, Expensive phase transfer catalysts such as tetraoctylammonium. Therefore, the use of such compounds is an extremely expensive method.

In this method, it is also 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 the catalyst used in the -degree reaction changes, 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]

In this way, the currently existing methods for producing maleimides are
It has many problems and is not satisfactory for industrial implementation.

Thus, the object of the present invention is to provide a complete and simple method for producing maleimides with higher purity than the above-mentioned methods.The present inventors have long continued research on the synthesis reaction of maleimides.

In particular, as a result of intensive studies on catalysts used in the ring-closing imidization reaction, we found that the mixture of amine salt and acid produced by the neutralization reaction between the raw material amine of maleimides and the acid is water-insoluble or water-immiscible and inert. The present invention was completed based on the discovery that the present invention exhibits a catalytic action with extremely high selectivity for ring-closing imidization reactions in organic solvents.

Conventionally, it was believed that organic or inorganic strong acids exhibit the best catalytic action for ring-closing imidization reactions, and therefore a mixed catalyst system of an amine salt and an acid produced by a neutralization reaction with such an acid has been used. It must be said that it is quite surprising that the acid-only catalyst system used also shows superior selectivity.

That is, the present invention involves heating maleamic acid in the presence of a mixture of an amine salt and an acid produced by a neutralization reaction between an amine used as a raw material during the production of maleimides and an inorganic or organic acid. This is a method for producing maleimides, which is characterized by ring-closing imidization.

The most characteristic feature of the present invention is that in the ring-closing imidization reaction, instead of using acid catalysts such as sulfuric acid, orthophosphoric acid, pyrophosphoric acid, and p-)luenesulfonic acid, amines, which are used as raw materials during the production of maleimides, and inorganic or The purpose is to use a mixture of an amine salt produced by a neutralization reaction with an organic monobasic acid or polybasic acid and an inorganic or organic monobasic acid or polybasic acid as a catalyst.

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

The maleamic acid used in the present invention is usually easily obtained by a reaction between 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, isoglobilamine, n-butylamine, Bee-butylamine, tart-butylamine, n-hexylamine, n-dodecylamine, allylamine, benzylamine, cyclohexylamine, aniline, nitroaniline,
Amine phenol, aminobenzoic acid, anisidine, ethoxyphenylamine, monochloroaniline, dichloroaniline, toluidine, xylidine, ethylaniline, etc.

The synthesis of maleamic acid is almost stoichiometric;
It is preferable that 1 mole of the amine be reacted with 1 mole of maleic anhydride, but it is possible to react in a range of 0.8 to 1.5 moles, preferably 0.9 to 1.2 moles.

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 is insoluble or immiscible in water, inert, and does not participate in the reaction, such as benzene, toluene, and
~120℃ petroleum fraction, xylenes, ethylbenzene,
inglobilbenzene, cumene, mesitylene, tert
-Butylbenzene, pseudocumene, trimethylhexane, octane, tetrachloroethane, nonane, chlorobenzene, ethylcyclohexane, boiling point 120-170°C
petroleum fraction, m-dichlorobenzene, 5ee-butylbenzene, p-dichlorobenzene, decane, p-cymene, 0-dichlorobenzene, butylbenzene, decahyde 90 naphthalene, tetrahydronaphthalene, dodecane, naphthalene, cyclohexyl Benzene, boiling point 170~
There are petroleum fractions at 250°C. The amount of this solvent to be used is 1 to 20 times (volume), preferably 3 to 7 times the amount of maleamic acid, in order to conduct the reaction smoothly and satisfy economic conditions.

Furthermore, a maleimide having a boiling point suitable for the reaction conditions is selected while taking into consideration 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-)luenesulfonic acid, orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, benzenesulfonic acid,
Amine salts obtained by neutralizing inorganic or organic monobasic acids or polybasic acids such as trichloroacetic acid with amines, which are raw materials for the production of maleimides, and these inorganic or organic monobasic acids or polybasic acids. Mixtures with polybasic acids are used.

In addition, the amine salt component in the mixed catalyst is at least 400 mol%.
Preferably, good results are obtained if it is present in the range of 50 to 80 mol.

The amount of mixed catalyst used is 2% for maleamic acid.
-400 mol, preferably 20-200 mol.

Further, in some cases, a polymetal-containing compound and a stabilizer may be present in the presence of the reaction.

Since the mixed catalyst system of amine salt and acid 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 mixed catalyst system of an amine salt and an acid as a catalyst does not substantially change before and after the reaction. Therefore, the mixed catalyst system itself can be used as is without recovery or purification in the next reaction.

When this catalyst layer is used 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% by weight of water to lower the temperature and viscosity and may be added in the form of an easy-to-handle aqueous solution.

Further, in some cases, a polymetal-containing compound or a stabilizer may be allowed to coexist in the reaction system for the reaction. The metal-containing compound used at this time is at least one metal oxide, acetate, maleate, or succinate selected from the group consisting of zinc, chromium, palladium, cobalt, nickel, iron, and aluminum. , nitrates, phosphates, chlorides and sulfates, among which zinc acetate is particularly effective. The amount of these used is 0.005 to 0.5 mol% as metal per 1 mol of maleamic acid.
and preferably 0.01 to 0.1 mol%.

Furthermore, as stabilizers, methoxybenzoquino/, p-methoxyphenol, phenothiazine, hydroquinone, alkylated diphenylamines, methylene blue, ter
t-Butylcatechol, tert-butylhydroquinone, zinc dimethyldithiocarbamate, copper dimethyldithiocarbamate, copper dibutyldithiocarbamate, copper salicylate, thiodigcopionic acid esters, mercaptobenzimitasole, triphenylphosphite, alkylphenols, alkylbisphenols Sudo is 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% per mol of maleamic acid.
The content is preferably 0.05 to 0.3 mol%.

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, and the temperature is lower than 150°C.
Simaleamic acid is obtained by reacting preferably at 30 to 120°C for 15 to 120 minutes. Next, without isolating the maleamic acid, the above-mentioned mixed catalyst of salt and acid, or a mixed catalyst layer of salt and acid separated from the reaction system, is added, and if necessary, a polymetal-containing compound and / or add stabilizer, 120-250℃, preferably 13
The reaction can be carried out by heating at 0 to 220°C for 1 to 15 hours and the water produced is distilled out of the system by azeotropic distillation, or by being distilled out of the system after the reaction is completed. Maleimides can be produced in high yield.

The present invention has been described above, but according to the present invention.

The benefits seen are as follows.

■ A mixed catalyst system consisting of an amine salt and an acid 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 high resistance to the ring-closing imidization reaction. Since it has a highly selective catalytic effect, it is possible to obtain highly pure maleimides in high yields.

■ The mixed catalyst system of amine salt and acid used as a catalyst is stable and can be used repeatedly in the reaction, so the cost of the catalyst can be almost ignored.

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

As shown in (1) to (3) above, maleimides can be produced cheaply, safely and easily.

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

Example 1 Oxoxylene 10 in 300 CC Mayer Fusco
0iP and orthophosphoric acid 60y- were dispersed. Next, while cooling the Mayer flask in a water bath, 37 g of cyclohexylamine was added dropwise to obtain a white quinrene slurry solution as a mixed catalyst of orthophosphoric acid monocyclohexylamine salt and orthophosphoric acid. Note that the amount of amine salt in this mixed catalyst was 60.9 mol%.

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 thereto to bring the temperature inside the flask to 100'C. Maleic anhydride was dissolved.

Next, 600 tons of ortho-xylene and 100 tons of cyclohexylamine? A slurry of N-cyclohexylmaleamic acid in oxoxylene was synthesized by adding the entire amount of the solution containing N-cyclohexylmaleamidic acid dropwise over 1 hour while stirring.

Next, the total amount of the mixed slurry of the above amine salt and orthophosphoric acid (the amount of mixed catalyst corresponds to 60.7 mol% based on maleamic acid) and 0.1 of copper dibutyldithiocarbamate were added to this slurry. In addition, the reaction mixture was heated and maintained at 143°C with stirring for 7 hours while water produced by the reaction was distilled out of the system together with oxoxylene.

After the reaction was completed, the lower catalyst layer was separated and removed from the reaction solution at 143°C.

Subsequently, the temperature of the reaction solution was lowered to 60°C, and the temperature was lowered to 100°C. Water of P was added, and the mixture was stirred and washed with water for 30 minutes, and the aqueous layer was separated. After repeating the above operation twice, 10 abg of oxoxylene was distilled off from the organic layer under reduced pressure.

Next, 0.3 iP of copper dibutyldithiocarbamate was newly added to the flask, and 51ffllEHg (abs) was added.
N-cyclohexylmaleimide was distilled under reduced pressure over 30 minutes while maintaining the internal temperature at 130 to 150°C.

As a result, a colorful white crystal 171? N-cyclohexylmaleimide was obtained. The purity of this product was 99.8% by weight, and the yield was equivalent to 94.4% by mole based on the raw material cyclohexylamine.

Next, the reaction operation was repeated in exactly the same manner except that a catalyst layer separated from the reaction system was used as a catalyst, and a colorful white crystal of N-cyclohexylmaleimide 1711 was obtained.
? I got it. The purity of this product is 99.8% by weight,
The yield corresponds to 94.4 mol% based on the raw material cyclohexylamine.

Example 2 100 kg of Kp-cymene and 100 kg of orthophosphoric acid were dispersed in a 300 cc Meyer flask. Next, while cooling the Mayer flask in a water bath, n--1"f-ruamino 56? was added dropwise to obtain a mixed white slurry solution of butylamine salt of orthophosphoric acid and orthophosphoric acid.
The amount of amine salt in this mixed catalyst corresponds to 75.0 mol%.

On the other hand, a reactor was prepared in which 11 glass flasks were equipped with a thermometer, a stirrer, and a water separator.

Next, 53 g of maleic anhydride powder was added to 50 g of p-cymene.
The solution dissolved in the above was charged to the above reactor.

Next, the temperature inside the reactor was adjusted to 130'C, and n-diptylamine 40iPp-cymene 400? was added dropwise little by little over 30 minutes to synthesize a slurry of N-(n-butyl)maleamic acid.

The total amount of the mixed catalyst slurry (the amount of the mixed catalyst is 18% based on maleamic acid) is added to the slurry thus obtained.
6.5 molti), ioacetic acid, 034. Si
' and p-methoxyphenol 0.065! y- was added thereto, and the reaction was carried out at a temperature of 1800C for 3 hours while distilling off the produced water together with p-cymene. The weight of the reaction solution after the completion of the reaction was 620y-, and the concentration of N-(n-butyl)maleimide in this was measured to be 11.5% by weight, which was based on the raw material n-butylamine. This corresponds to 85.1 molti.

Subsequently, the reaction operation was repeated in exactly the same manner except that the catalyst layer separated from the reaction system was used, and 625 volumes of reaction liquid were obtained. The concentration of N-(n-butyl)maleimide in this was measured and was 11.6% by weight, which is 86% by weight.
．． Equivalent to 5 molti.

Example 3 Orthophosphoric acid 60y- in a 300CC Meyer flask
I put it in. Next, cyclohexylamine 461- was added dropwise to the Mayer flask while cooling it in a water bath to obtain a viscous mixed catalyst slurry of cyclohexylmonoamine phosphate and phosphoric acid. Incidentally, the amount of amine salt in this mixed catalyst was 75.8 mol.

On the other hand, xylene ZoofP was placed in an 11 glass autoclave equipped with a thermometer, cooling tube, addition funnel, and stirrer.
was charged, 100 g of maleic anhydride was added thereto, the temperature inside the flask was raised to 100°C, and the maleic anhydride was dissolved.

Then, cyclohexylamine 10 was added to xylene 4009-
A solution containing N-cyclohexylmaleamic acid was added dropwise over 30 minutes with stirring to synthesize a slurry of N-cyclohexylmaleamic acid in the above solvent.

Next, the slurry liquid was heated without distilling the mixed catalyst slurry out of the entire system, and the internal temperature was maintained at 152° C., and the reaction was allowed to proceed for 3 hours. The pressure in this time series is 1.2 at the beginning of the reaction.
What was an ATM turned out to be 7.3 hours later. It became Oatm.

After the reaction was completed, the reactor was cooled to bring the internal temperature to 130° C., then returned to normal pressure, and the reactant was taken out and allowed to stand, and the reaction solution was clearly separated into two layers: an organic layer and a catalyst layer.

The weight of this organic layer is 660? The N-cyclohexylmaleimide content therein was 24.6% by weight as measured by gas chromatography. This corresponds to 89.8 molti based on the raw material cyclohexylamine.

Next, the same procedure was repeated except that a mixed catalyst layer of amine salt and acid separated from the reaction system was used, and the organic layer was 664? I got it. The content of N-7 chlorohexylmaleimide in this was 24.5% by weight. This corresponds to 90.0 mole based on the raw material cyclohexylamine.

Comparative Example 1 Cyclohexylamine c+c+, 2? The mixture was added dropwise at 50 to 70°C while stirring. Stir for 2 hours after finishing the dropping.
N-cyclohexylmaleamic acid was obtained. Next, add methanesulfonic acid 14 to this solution. , methanesulfonic acid-N-cyclohexylmaleamide P-acid 8.7 and N-methylpyrrolidone 14M' were added at 115°C for 3 hours.
．． The reaction was carried out under reflux for 5 hours while removing the produced water as an azeotropic fraction with toluene.

Thereafter, 15y- of acetic anhydride was added, and after reacting for 30 minutes, the temperature was lowered to 60° C. and the reaction solution was filtered to remove insoluble impurities, the catalyst, unreacted N-cyclohexylmaleamic acid, and the like. Next, add 20Of water to solution F and add 3
The mixture was stirred for 0 minutes and washed with water, and the aqueous layer was separated. After repeating this operation twice, 30 mmHg (abs) was removed from the organic layer.
When toluene was distilled off under reduced pressure, a solid containing cyclohexylmaleimide of color 172? I got it. According to GPC analysis, the content of N-cyclohexylmaleimide
: 10. The yield of N-cyclohexylmaleimiton was 96 moles based on cyclohexylamine. Incidentally, analysis results of the reaction solution by gas chromatography also showed similar yields.

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

According to GPC analysis, the content of N-n-butylmaleimide 0 was 13.4% by weight, and the yield was 13.2 mol greater than the raw material n-butylamine.

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

Comparative Example 3 Maleic anhydride 43.1y-4-chlorobenzene 331
．． 7 chlorhexylamine in a solution dissolved in 89 39.7
．． P was added and reacted at 40°C for 1 hour.

The resulting slurry of N-cyclohexylmaleamic acid contains 12 cc of dimethylacetamide and 2 cc of trichloroacetic acid. was 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 added. N in this reaction solution
-When cyclohexylmaleimide was analyzed by gas chromatography, N-cyclohexylmaleimide was found to be 2.
It contained 2% by weight.

The yield of N-cyclohexyl maleimide was equivalent to over 12.3 mol based on the raw material cyclohexylamine.

Claims (4)

[Claims] (1) When producing maleimides by dehydrating and ring-closing maleamic acid obtained from maleic anhydride and amines, an amine salt obtained from the amine and an inorganic or organic acid, and an inorganic or organic acid A method for producing maleimides, which comprises heating maleamic acid in a water-insoluble or water-immiscible inert organic solvent to cause a ring-closing imidization reaction using a mixture of the above as a catalyst. (2) The amine salt component in the mixed catalyst is at least 40 mol%
The method according to claim (1), characterized in that: (3) Add 2 to 4 mixed catalysts to the raw maleamic acid.
The method according to claim (1) or (2), characterized in that the reaction is carried out in the presence of 00 mol%. (4) Claims (1), (2), or (3) characterized in that the heating temperature is in the range of 120 to 250°C.
Method described.