JPS5829791B2 - Maleimidonoseizouhou - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing maleimide.

More specifically, the present invention is directed to producing maleimide from N-carbamoyl maleamic acid, and more specifically, by maintaining N-carbamoyl maleamic acid in a solvent at a temperature of 50 to 150°C in the presence of a catalyst to form maleimide. The present invention relates to a method for producing maleimide, which is characterized by converting maleimide into

Maleimide is a compound that has an extremely wide range of uses as a raw material for various polymeric compounds, and as a raw material for fungicides, insecticides, herbicides, antioxidants, rubber hardening agents, anticorrosion agents, etc., but it is not used industrially. An advantageous manufacturing method has yet to be established.

Conventionally, maleimide has been produced by reacting maleic anhydride with furan or cyclopentadiene.
A long-known method has been known in which an alter-adduct is produced, which is then treated with ammonia to convert it into a maleimide adduct, and the resulting maleimide adduct is thermally decomposed to produce maleimide, which is then separated and obtained. However, the process is complicated and cannot be called an industrial method.

Further, US Pat. No. 2,788,349 discloses a method for producing maleimide using N-carbamoyl maleamic acid as a raw material through a reaction as shown in formula (1X2).

As is clear from the reaction formula, this method involves producing and isolating N-carbamoylmaleimide from the raw material N-carbamoylmaleamic acid, and then simply thermally decomposing the N-carbamoylmaleimide or using zinc chloride as a catalyst. This is a method of producing maleimide by thermal decomposition or decomposition at 95 to 1000 C using dimethylformamide as a solvent and catalyst, and it is an essential condition to produce and isolate the intermediate N-carbamoylmaleimide. There is.

However, in order to produce N-carbamoylmaleimide, it is necessary to carry out a dehydration ring-closing reaction from the raw material N-carbamoylmaleamic acid and an equimolar amount of acid anhydride, during which the acid anhydride is hydrated and consumed. However, the process for producing maleimide from N-carbamoylmaleamic acid is not only complicated, but also requires a large cost of auxiliary raw materials, so it cannot be said to be an industrial production method.

The purpose of the present invention is to provide an industrially implementable method for producing maleimide, and more specifically, maleimide is produced in one step using N-carbamoylmaleamic acid as a raw material without isolating any intermediates. The purpose is to provide a method.

As a result of various studies for the above purpose, the present inventors prepared N-carbamoyl maleamic acid in an inert solvent in the presence of a catalyst of at least one metal compound selected from copper, zinc, nickel or cobalt for 50 to 50 minutes. The present invention was completed by discovering that maleimide can be produced by maintaining the temperature at 150°C.

N-carbamoylmaleamic acid, which is the starting material of the present invention, can be obtained extremely easily, in high yield, and with high purity by a known method, for example, by the reaction of maleic anhydride with urea, so it can be used as a raw material for producing the target maleimide. It is suitable as

However, it goes without saying that the present invention is not limited to the method for producing N-carbamoylmaleamic acid as a starting material.

According to the method of the present invention, maleimide can be completed in one step without the need for auxiliary raw materials such as acid anhydrides, so the process is simpler and extremely economical compared to known methods.

The method of the present invention is carried out as follows.

A catalyst consisting of N-carbamoyl maleamic acid and at least one metal compound selected from copper, zinc, nickel, or cobalt is added to a solvent to dissolve or partially suspend the mixture, and the mixture is maintained at a predetermined temperature. After a predetermined reaction time, a reaction solution containing maleimide is obtained.

Maleimide can be obtained from the reaction solution by a conventional method.

The metal compounds used as catalysts in the present invention include copper,
It is a compound of zinc, nickel or cobalt, and the form of the compound is not particularly limited, but preferred examples include chloride, oxide or acetate.

The amount of the catalyst to be used is 1 mol φ or more, preferably 5 to 100 mol, relative to the raw material N-carbamoylmaleamic acid, and the effect is hard to be observed if the amount used is 1 mol φ or less.

The solvent used in the method of the present invention is not particularly limited, but it is preferably a solvent in which N-carbamoylmaleamic acid is soluble and inert to the maleimide produced.
For example, aprotic polar solvents such as dimethylformamide and dimethylsulfoxide are particularly preferred.

The reaction temperature in the method of the invention is 50-150°C, preferably 70-120°C.

Temperatures below 50° C. are not preferred because the production rate is extremely slow.

Furthermore, since the maleimide product is a substance that is highly polymerizable, a reaction temperature of 150° C. or higher is not preferred.

From the thus obtained reaction solution containing maleimide,
Maleimide can be easily isolated by conventional methods.

That is, maleimide can be obtained by distilling off the solvent from the reaction solution and then distilling the residue, or by performing solvent extraction from the residue.

The present invention will be explained in more detail with reference to Examples below.

Example 1 100 ml of dimethylformamide, 200 g of N-carbamoyl maleamic acid and cupric chloride9. Og was placed in a flask, and the temperature was raised to 100° C. while stirring, and the reaction was continued for 1 hour.

After the reaction was completed, dimethylformamide was distilled off at 80'C under reduced pressure, and then 40 d of ethyl acetate was added to the residue after distilling dimethylformamide, and the mixture was heated under reflux in a water bath for 30 minutes.

After cooling, filter the filtrate and collect ethyl acetate from the filtrate.
When treated at πHg and an oil bath temperature of 120° C., the product was distilled out and 7.7 g of crystals were obtained in an air-cooled collection tube.

The obtained product was confirmed to be maleimide as a result of the following analysis.

Melting point = 88-90°C, elemental analysis: 14.39 weight strength (excluding nitrogen), infrared absorption spectrum completely matches the svector of maleimide, and the yield of maleimide based on the starting material N-carbamoyl maleamic acid is 62.7 mol. It was φ.

Example 2 A reaction was carried out in the same manner as in Example 1, and after the reaction was completed, the reaction was carried out under reduced pressure for 80 minutes.
After dimethylformamide was distilled at .degree. C., vacuum distillation was directly performed instead of the solvent extraction operation in Example 1.

That is, as a result of treating the residue at 5 mmHg and an oil bath temperature of 120° C., maleimide was obtained in a yield of 61.0 mol.

Examples 3 to 7 The same procedure as in Example 1 was carried out except that the catalyst and the amount used thereof were changed as shown in Table 1, and the results shown in Table 1 were obtained.

Example 8 The same procedure as in Example 1 was carried out except that dimethyl sulfoxide was used as the solvent. As a result, maleimide was obtained in a yield of 3.57 mol.

Example 9 The same procedure as in Example 1 was carried out except that the reaction temperature was 110° C. and the reaction time was 30 minutes. As a result, maleimide was obtained in a yield of 60.8 mol.

Example 10 The same procedure as in Example 1 was conducted except that the reaction temperature was 70° C., the reaction time was 8 hours, and the solvent was recovered at 70° C. under reduced pressure. As a result, maleimide was obtained in a yield of 560 mol.

Claims (1)

[Claims] IN-carbamoyl maleamic acid is dissolved in an inert organic solvent in the presence of at least one metal compound selected from the group consisting of copper, zinc, nickel, or cobalt.
1. A method for producing maleimide, which comprises converting maleimide by maintaining the temperature at 0.00.