CS264403B1 - Process for the preparation of N, N * -m-phenylene-bis-malesic acid - Google Patents

Abstract

The method for preparing N,N'-m-phenylene-bis-maleamic acid consists in the reaction of m-phenylenediamine with maleic anhydride in an aqueous medium. Maleic anhydride is introduced into an aqueous solution of m-phenylenediamine with stirring, either as a solid or as a solution in an organic solvent. The pH of the reaction mixture is maintained at a value of 6.5 to 9.5 during the reaction by adding alkaline agents. The product remains dissolved in the reaction mixture after the combined reaction and is precipitated by acidification. This allows obtaining a pure product by simply removing impurities before isolating it from the solution. N,N'-m-phenylene-bis-maleamic acid is an intermediate for the production of m-phenylene-bis-maleimide, which is to be used in the rubber and plastics industry.

Description

The invention relates to a novel process for the preparation of Ν, Ν'-m-phenylene-bis-maleamic acid by reaction of m-phenylenediamine and maleic anhydride. N, N'-m-phenylene-bis-maleamic acid (I) is an intermediate for the preparation of m-phenylene-bis-maleimide, which has an important use in the rubber and plastics industry both as an important adhesive in rubber and rubber-steel systems and for the preparation of heat-resistant polymers. The acid and its imide also exhibit insecticidal and fungicidal properties.

1 H-CO-CH = CH-COOH

HOOC-CH-CH-CO-N The general method for preparing m-phenylene-bis-maleamic acid is by condensing m-phenylenediamine with maleic anhydride. Practical methods employ an environment of organic solvents, especially acetone and other aliphatic ketones for this reaction, but condensations are also described in less common polar organic solvents such as N-methylpyrrolidone, dimethylsulfoxide and aliphatic carboxamides such as dimethylformamide and the like. to 80 ° C and the product is isolated either directly by filtration if it starts to fall out of the reaction mixture during the reaction, or prior dilution of the reaction mixture with water must be carried out.

The disadvantage of these processes lies precisely in the use of organic solvents. The reactions must be carried out in closed reaction vessels in operations equipped with flammable substances, ie with a certain degree of explosion hazard. Other complications are caused by filtration, which must be carried out on pressurized presses, common filter presses or presses cannot be used. The technological process must then be extended to the necessity of regeneration of solvents from waste filtrates.

These disadvantages of the hitherto known processes are solved by the present invention, which relates to a novel process for the preparation of Ν, Ν'-m-phenylene-bis-maleamic acid by reaction of m-phenylenediamine with maleic anhydride. SUMMARY OF THE INVENTION The invention provides that 1.8 to 4.0 parts by weight of maleic anhydride solid or optionally dissolved in an inert solvent are introduced into an aqueous solution of 1 part by weight of m-phenylene diamine while maintaining the pH of the reaction mixture at between 6.5 and 9.5 and upon completion of the reaction, the product is isolated by filtration with a mineral acid. The pH of the reaction solution is kept within these limits by the addition of aqueous alkaline hydroxide or by dissolving 0.9 to 4.0 parts by weight of sodium bicarbonate or sodium carbonate per part by m-phenylenediamine in the reaction solution.

In practice, the reaction exotherms the synthesis so that the reaction mixture is not heated and the heat of reaction is released or the temperature is controlled by moderate cooling. The optimum temperature is in the range of 30 to 50 ° C, a temperature above 60 ° C is not recommended, as according to the literature, the product may be subject to partially competitive reactions, the fumes of which may pollute the final product.

The pH of the reaction solution can be kept within optimal limits either by the addition of alkaline lye, preferably by automatic dosing based on the pH sensor data, or the pH of the reaction mixture can be maintained by adding a predetermined amount of bicarbonate or carbonate to the solution x. sodium. The pH has a significant effect on the course of the reaction. The high pH will cause the rate of hydrolysis of the maleic anhydride to exceed the rate of acylation of m-phenylenediamine, thereby increasing the consumption of maleic anhydride disproportionately with the time required for the reaction.

At a low pH, premature precipitation of the product and the monoacylic m-phenylenediamine from the solution begins, which again increases the required reaction time and the product additionally contains a greater amount of free amino groups.

The amount of water required for the reaction is not critical and does not affect the yield, since the product formed is almost insoluble in an acidic aqueous medium. The amount of water must be chosen so that it is sufficient to dissolve the m-phenylenediamine well and to allow the acid to precipitate out of solution in the form of larger crystals, allowing easy filtration or filtration. another wash.

Maleic anhydride can be introduced into the reaction directly in the solid phase. However, the process requires good mixing, for example with a propeller stirrer. If good mixing cannot be guaranteed, solutions of maleic anhydride in organic solvents for the reaction of inert solvents may also be used. Such solvents may be, for example, acetone, methyl ethyl ketone, dimethylformamide, N-methylpyrrolidine, dimethylsulfoxide and the like.

The product is isolated by acidification of the reaction mixture by addition of a mineral acid to a pH in the range of about 3 to 5. Both hydrochloric acid and sulfuric acid, respectively, can be used for acidification without differences in product quality. and others.

In addition to the above advantages over the known methods of eliminating the problems arising from working with organic solvents, the novel process has one particularly valuable advantage. Since the reaction is carried out in an aqueous, slightly alkaline medium, both the starting components and, in particular, the product are soluble in the medium. This gives a clear reaction solution of the product, which can be easily clerred without or with the addition of carbonaffin, optionally. kieselguhr and, after acidification, obtain very pure m-phenylene-bis-maleamic acid.

In other words, if one of the starting materials is used in a less pure state, in particular as regards the quality of the easily oxidized m-phenylenediamine-oxidizing processes, a very pure desired product can still be obtained. In the previously used solvent syntheses, which utilized the fact that the product was directly precipitated from the reaction mixture, since m-phenylene-bis-maleamic acid was almost insoluble in most solvents, it could not be purified at all without complications. Refining was only possible with the addition of another production phase to the process system.

The following examples describe the reaction. Parts shown are by weight.

He did

The reactor is charged with 1.500 parts of water, in which 108 parts of m-phenylenediamine and 235 parts of sodium bicarbonate are dissolved with stirring. After dissolution, 225.4 parts of solid maleic anhydride in the form of scales are added in portions over 1 hour. The temperature of the reaction solution increases by about 10 ° C. Maleic anhydride is added such that the next dose is added after dissolution of the previous one. After the dosing is complete, the solution is stirred for 1 hour and then acidified by the addition of 230 parts by volume of conc. hydrochloric acid to pH 3.8. The precipitated pale yellow product is suction filtered and washed with 2000 parts of water. 80 to 950 parts of product paste are obtained which, after drying in a hazelnut oven at 110 ° C, yields 300 parts of practically pure N, N'-m-phenylene-bis-maleamic acid, which is almost 99% of the theory calculated on m-phenylenediamine.

Example 2

The procedure of Example 1 can be modified so that instead of adding solid scale maleic anhydride, a solution of 225.4 parts of maleic anhydride in 350 parts of acetone can be added. The advantage of the process is only in easier dosing and shortening the reaction time by about one third. The yield of the reaction is quantitative relative to the m-phenylenediamine employed.

Example 3

A solution of 108 parts of m-phenylenediamine in 1200 parts of water is presented in the reactor. At 35 ° C, maleic anhydride is added to the reactor in portions of 10 parts every 3 minutes. The pH of the reaction solution at the start of the reaction is adjusted to 8.0 by addition of 15 parts 20% sodium hydroxide solution *. Throughout the reaction, this value is maintained automatically such that any increase in the acidity of the reaction solution (i.e., a decrease in pH) indicated by the introduced pH probe is immediately compensated automatically by the necessary 20% NaOH solution. The total consumption for the reaction is 560 parts. After completion of the maleic anhydride dosing and stirring for half an hour, conc. hydrochloric acid pH adjusted to 3.8, the precipitated product is filtered off on a filter press, the filter cake washed with 2,000 parts of water and dried. Yield 302 parts of pale yellow powder.

Claims (3)

SUBJECT OF THE INVENTION Process for the preparation of N, N'-m-phenylene-bis-maleamic acid of the formula I by reaction of m-phenylenediamine and maleic anhydride, characterized in that 1.8 to 4.0 wt. The pH of the reaction mixture is kept between 6.5 and 9.5 for the duration of the reaction, and after completion of the reaction, the acidified product is isolated by filtration with a mineral acid. HOOC-CH «CH-CO-NH- NH-CO-CH-CH-COOH AND 2. A process according to claim 1, wherein the determined pH is maintained by the addition of aqueous alkaline hydroxide during the reaction. 3. The process of claim 1 wherein the determined pH range of the reaction mixture is achieved by adding 0.9 to 4.0 parts by weight of sodium bicarbonate or sodium carbonate per part by weight of m-phenylenediamine to the reaction solution.