SU670568A1 - Method of purifying n-vinylpyrrolidone - Google Patents

Description

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The invention relates to a method for the purification of N-vinylnirrolidone, which is widely used as a monomer for the preparation of polyvinylpyrrolidone and a number of copolymers for various purposes in the chemical industry.

Upon receipt of N-winlpyrrolidone by direct vinylation of 2-pyrrolidone with acetylene at a temperature of 160-180 ° C for 3-4 hours using a potassium pyrrolidonate as catalyst 1, a significant resinification of the reaction mass occurs, as well as the formation of by-products (primary and secondary amines of aliphatic yes, acetaldehyde, etc.). The presence of these impurities makes it difficult for N-vinyl pyrrolidone to be purified by distillation, even under different process conditions.

Particularly high purity requirements for N-vinylpyrrolidone are made in the manufacture of low molecular weight polyvinylpyrrolidone used for medical purposes.

A known method of purification of N-vinylpyrrolidone by distillation under reduced pressure in the presence of additives of organic substances — polycarboxylic acids of molecular weight from 10,000 to 300,000 2.

The yield of the target product is 87-89%, the content of the main oil is 99.2-99.4%. The disadvantage of this method is the relatively low yield of N-vinylpyrrolidone and the content of the main substance in it.

The aim of the invention is to increase the yield of N-vinyl pyrrolidone and improve its quality.

This goal is achieved by the method of purification of N-vinylpyrrolidone by distillation under reduced pressure in the presence of additives of organic substances, a distinctive feature of which is the use of alkyl- or aryl diisocyanates as additives of organic compounds.

C4-Ca-alkyldiisocyanates are used as alkyl diisocyanates.

As aryl diisocyanates, either toluene diisocyanate or 3,3 or 4,4-biphenylene diisocyanates are used.

Typically, alkyl or aryl diisocyanates are added in an amount of 0.1-1.0% by weight of N vinylnirrolidone.

The proposed method allows to increase the yield of N-vinylpyrrolidone to 92-95% and increase the content of the main substance in it to 99.6-99.9%. This is due to the fact that diisocyanates interact with

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impurities of various chemical structures contained in the technical M-vinylylirrolidone, with the formation of solid products of the urethane series.

The method is illustrated by the following examples.

Example 1. In a distillation colony with a cube capacity of 2 liters, 70 cm high, with a nozzle of Raschig rings, 1 kg of technical vinylpyrrolidone (VP) is loaded, containing 98.5% of the basic substance (GLC data). 10 g of hexamethylene diisocyanate are introduced into the cube and the rectification process is carried out with the following parameters: cube temperature 160-180 ° C, column top temperature 100-120 ° C, residual pressure 8-10 mm Hg. Art., reflux number 20: 1. A fraction with a boiling point of 92-93 ° C at 8 mm Hg is taken. Art., 1, (literature data p 1.5120, kip. 92 ° C at 8 mm Hg. Art.). The output of EP 940 g (94%), the content of the basic substance according to GLC of 99.8%.

Example 2. In a distillation column with the characteristics given in example 1, load 1 kg of VP, purified over polymethacrylic acid with a basic substance content of 99.2% and 1 g of hexamethylenediisocyanate. The process is carried out as described in Example 1. The fraction boiling at 92-93 ° C and 8 mm Hg is removed. Art. The output of EP 950 g (95%), the content of the basic substance of 99.9% (GLC), p,.

Example 3. As in Example 1, except that 4.66 g of tetramethylene diisocyanate is added and the reflux number is set to 30: 1. A fraction boiling at: 92-93 ° C and 8 mm Hg is taken. Art. Physico-chemical constants as in example 1. The output of the EP 950 g (95%), the content of the basic substance of 99.7% (GLC).

Example 4. As in Example 1, except that 8.0 g of octamethylene diisocyanate was added. Physico-chemical constants, as in example 1. The output of the EP 940 g (94%), the content of the basic substance of 99.6% (GLC).

Example 5. In distillation column4

Well, worn in Example 1, 1 kg of technical BI containing 98.0% of the main substance is loaded (GLC data), 10 g of toluylene diisocyanate are added to the cube and the rectification process is performed with the parameters specified in Example 1. The output of pure VP 920 g (92%), boiling point 92--93 ° C at 8 mm Hg. Art., 1.5122. Content

the main substance according to GLC 99.9%.

Example 6 In the same manner as in Example 5, except that 5 g of 3,3biphenylene diisocyanate was added. The output of the EP 930 g (93%), the content of the substance of 99.8% (GLC), 1,5122, / Dec 9.9-93 C at 8 mm Hg. Art.

Example 7 In the same manner as in Example 5, except that 7 g of 4,4 biphenylene diisocyanate was added. The output of VP 920 g (92%). The parameters of physico-chemical constants, as in example 2. The content of the basic substance, determined by GLC, is 99.8%.

Claims (3)

1. A method for purifying N-vinylilyrrolidone by distillation under ionic pressure in the presence of additives of organic substances, characterized in that, in order to increase the yield and improve the quality of the target product, Cj-Ca-alkyl-aryl aryl diisocyanates are used as additives of organic matter. 2. A method according to claim 1, characterized in that either aryl diisocyanate or 3.3 or 4,4-biphenylene diisocyanates are used as aryl diisocyanates. 3. Method according to paragraphs. 1-3, characterized in that the alkyl or aryl diisocyanates are added in an amount of 0.1-1.0% by weight of N vinylpyrrolidone. Sources of information taken into account in the examination 1. Sidelkovska F.P. Khimi N-vinylpyrrolidone and its iolimer. M., Spider, 1970. 2. For the number 2385940/04, cl. From 07D 207/26, 07/12/76, on which the decision to issue an author's certificate was made.