CS260072B1 - A method of cyclizing arylene-bis-maleamic acids - Google Patents

Abstract

Cyclization of arylene-bis-maleamic acids of formula I by reaction with acetic anhydride and an organic tertiary base to arylene-bis-maleimides.

Description

The invention relates to a process for the cyclization of arylenebis-maleamic acids of formula 1,

Y.

HOOC-CH = CH-CO-NH

X

-NH — CO — CH — CH — COOH, (I) wherein X and Y are H, Cl or CH 3, wherein X and Y are the same or may be different. These substances find use in the rubber and plastics industries as adhesives for bonding carrier materials to natural or synthetic rubber and as additives in the preparation of heat-resistant polymers, especially acrylic resins. They are also used in the preparation of biocidal substances.

The methods used to date for the cyclization of arylene-bis-maleamic acids to arylene-bis-maleimides are carried out using a mixture of alkali salts of fatty acids and anhydrides using a mixture of alkali salts of fatty acids and lower fatty acid anhydrides (US Pat.

444,536, Brit. U.S. Pat. No. 1,137,592). Manganese, cobalt or lithium salts (German Pat. No. 2,719,903), or a mixture of nickel salts, triethyl amine and acetic anhydride (German Pat. No. 2,040,094) or magnesium salts (US Pat. No. 4,154,737). Also disclosed are methods using water removal by cyclization by azeotropic distillation with toluene (US Pat. No. 3,944,525) or by the addition of anhydrous alkali fatty acid salts in the presence of a solvent (Cs. AO 203 356).

The disadvantage of the prior art processes is the use of relatively expensive catalysts or solvents and, above all, the difficulty in isolating the resulting products; none of these processes has solved the problem of waste filtrate disposal, which in addition causes environmental problems in many cases due to the presence of heavy metal ions.

It has now been found that the aforementioned drawbacks of the hitherto known methods solve the present invention. The object of the invention is a novel process for cyclizing arylene-bis-maleamic acids, which comprises reacting a mixture of 1 mole of arylene-bis-maleamic acid, 2 to 6 moles of acetic anhydride and 0.1 to 2 moles of organic tertiary base at 20 °. The product is isolated by filtration after diluting the reaction mixture with water. The process can also be modified such that the product is isolated by filtration after neutralization of the reaction mixture with an alkali hydroxide or carbonate solution. In this case, the filtrate can be advantageously used for the preparation of sodium acetate, which has a wide range of applications.

The advantage of this process lies in its simplicity, the associated low technical and economic demands and, compared to the known processes, a considerably lower waste toxicity and thus a greater environmental advantage. Especially preferred is a process using neutralized filtrates from product isolation, since about 80% utilization of the used acetic anhydride can be achieved, which in the prior art goes all into the waste water.

As the tertiary organic base, for example, tri-n-butylemine, pyridine, triethylamine, triethanolamine or other available substances can be used for cyclization. In practical use, there was no significant difference in the effect on the course of the reaction, which could indicate a greater advantage of using one of them. Advantages can only be decided on the basis of their availability, price range or toxicity.

The process utilizing the neutralization of the reaction mixture to produce a byproduct - sodium acetate has the advantage that the reaction mixture need not be so diluted, since the salinity of the resulting solution is not sufficient to eliminate all of the product. Sodium acetate can then be obtained by crystallization with separate mother filtrates, or directly using a saturated solution of sodium acetate in other chemical products where the pH adjustment of the aqueous medium is carried out. This is most common with conventional dyeing products. For neutralization, it is then essentially irrelevant whether sodium hydroxide or sodium carbonate solutions are used.

The amount of acetic anhydride for cyclization is always higher than the theory. However, the amount must be chosen which is sufficient to dilute the reaction mixture so as to be miscible. A device with good stirring capability then requires less acetic anhydride for cyclization.

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

He did

57 parts of acetic anhydride and 14 parts of pyridine are introduced into the reactor. 61 parts of p-phenylene-bis-maleamic acid are added to the mixture and the mixture is heated to 55 ° C with stirring for 4 hours. After heating, the reaction mixture was diluted with 1500 parts cold water and the precipitated product was filtered off under suction. After washing with 500 parts of water and drying, 44 parts of p-phenylene-bis-maleimide are obtained as pale yellow needles of m.p. above 310 ° C.

Example. 2

The reactor was charged with 303 parts of acetic anhydride to which 48 parts of triethylamine were added. 300 parts of m-phenylene-bis-maleamic acid are gradually added to the resulting solution while stirring. The resulting suspension was stirred at 50 ° C for 4 hours and then poured into 1200 parts of ice. The precipitated pale yellow product is suction filtered, washed with 600 parts of water and dried. Yield 235 parts of m-phenylene-bis-malenimide, m.p. 202 DEG.

Example 3

300 parts of acetic anhydride are charged to the reactor and 45 parts of tri-n-butylamine are added. 315 parts of 2-methyl-1,3-phenylene-bis-maleamic acid were added to the resulting solution with stirring. The resulting suspension was stirred at 60 ° C for 3 hours, then neutralized with cooling by the addition of 2350 parts by volume of 2.5 mol / L sodium hydroxide solution (NaOH) and the resulting suspension was suction filtered. The precipitated product is washed under suction with 500 parts of water and dried. The yield of 2,4-toluylene-bis-maleimide is 245 parts, m.p. 171 ° C. The mother filtrates are concentrated to crystallize and the precipitated sodium acetate trihydrate is filtered off with suction.

About 450 parts of this by-product can be obtained.

Claims (2)

A process for cyclizing arylene-bls-maleamic acids of formula I Y. HOOC-CH-CH-CO-NH X - NH - CO - CH = CH - COOH (I) wherein X and Y are H, Cl or CH 2, wherein X and Y are the same or may be different, to the arylene-bis-maleimides indicated therein. A mixture of 1 mol of arylene-bis-maleamic acid, 2-6 moles of acetic anhydride and 0.1-2 moles of organic tertiary base is allowed to react at 20 ° C to 80 ° C and after completion of the reaction the product is isolated by filtration after diluting the reaction mixture. water. 2. Arylene-bis-maleamic acid cyclization process according to claim 1, characterized in that the product is isolated by filtration after neutralization of the reaction mixture with an alkali hydroxide or carbonate solution.