RU2243211C2 - Method for preparing 2,2'-azobis-isobutyronitrile - Google Patents

Abstract

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to a method for preparing 2,2'-azobis-isobutyronitrile used as a foaming agent for polymers and an initiating agent in radical polymerization of unsaturated hydrocarbons. Method involves interaction of acetone cyanohydrin with hydrazine hydrate in an aqueous medium followed by oxidation of intermediate 2,2'-hydrazobis-isobutyronitrile with hydrogen peroxide in acid medium in the presence of bromine or its compounds with using tungsten, vanadium and molybdenum compounds as a catalyst. The oxidation process is carried out in the presence of surface-active substances taken in the amount 0.05-1% of charged acetone cyanohydrin being without isolation of the intermediate compound. Method provides preparing the end substance with the yield 94-95.3% as measured for the parent hydrazine.

EFFECT: improved preparing method.

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Description

The invention relates to a method for producing 2,2'-azobisisobutyronitrile, used as a foaming agent of polymers and initiator of radical polymerization of unsaturated hydrocarbons.

A known method of producing 2,2'-azobisisobutyronitrile by the interaction of acetone cyanohydrin with hydrazine salts (sulfates, chlorides, phosphates) in an aqueous medium in the presence of caustic alkalis at 15-50 ° C with the formation of an intermediate 2,2'-hydrazobisisobutyronitrile, which is filtered off, washed with water, dried and then oxidized with hydrogen peroxide in the presence of bromine and sulfuric acid compounds in an aqueous medium at a temperature of 15-40 ° C. Product yield 80-92%. (Patent СРР No. 90608, MKI ₄ , С 07 С 121/00, 1984; Patent СРР No. 91258, MKI ₄ , С 07 С 121/04, 1985; Patent СРР No. 90607, MKI ₄ , С 07 С 121/00, 1984; Patent CPP No. 90708, MKI ₄ , C 07 C 121/14, 1985).

The disadvantages of the known methods are: a large number of highly concentrated salt wastewater, due to the use of hydrazine salts and alkalis in the first stage of the process and washing of the intermediate product, the complexity of the process due to the stages of isolation of the intermediate product and its drying, insufficiently high yield of the product.

The closest in technical essence and the achieved result is a method for producing 2,2'-azobisisobutyronitrile, according to which, at the first stage, 2,2'-hydrazobisisobutyronitrile is obtained by known methods from hydrazine or its adducts and acetone cyanohydrin and then oxidized to the end product by the action of hydrogen peroxide in aqueous medium in the presence of mineral or organic acid, bromine compounds and as catalysts for molybdenum, vanadium, tungsten or uranium compounds at 0-50 ° C. The product is filtered off, washed with water and dried in vacuo at 35 ± 2 ° C. The yield of 2,2'-azobisisobutyronitrile is 91.4-98.2%, counting on 2,2'-hydrazobisisobutyronitrile (Auth. Certificate Czechoslovakia No. 2323250 MKI ₄ , C 07 C 121/16, 1983).

The disadvantages of this method of producing 2,2'-azobisisobutyronitrile are: the complexity of the apparatus design due to the presence of stages of isolation and preparation of a suspension of intermediate 2,2'-hydrazobisisobutyronitrile, unfavorable sanitary and environmental characteristics of the process due to additional contact with cyanide compounds at the stages of isolation, washing and preparing a suspension of an intermediate product, a large amount of wastewater requiring careful neutralization from cyanide compounds obtained at the stage of isolation of both the intermediate and the target product.

The objective of the present invention is to develop a technology for producing 2,2'-azobisisobutyronitrile in a simplified scheme with improved sanitary and environmental characteristics of the production.

The problem is solved by the method of producing 2,2'-azobisisobutyronitrile, which consists in the condensation of hydrazine hydrate with acetone cyanohydrin in an aqueous medium in the presence of 0.05-1% of a surfactant from charged acetoncyahydrin followed by oxidation of the resulting intermediate 2,2'-hydrazobisisobutyronitrile its evolution by hydrogen peroxide in an acidic medium in the presence of bromine or its compounds and as catalysts for tungsten, vanadium or molybdenum compounds.

The technical result from the implementation of the proposed method, the introduction of a surfactant into the reaction mass ensures the wettability of the hydrophobic intermediate product, which contributes to its uniform distribution and improves contact with the oxidizing agent, the process design is simplified and its duration is reduced, the amount of wastewater is reduced and sanitary and environmental characteristics are improved.

A distinctive feature of the proposed method is the process in the presence of surfactants, without the release of 2,2'-hydrazobisisobutyronitrile.

Water, a surfactant, acetone cyanohydrin are charged into the reactor, and hydrazine hydrate is dosed at 20-40 ° C. The mass is kept at 20-45 ° C for 2-8 hours. Then, catalyst, acid, bromine or a compound thereof are sequentially loaded into it at 10-20 ° C, hydrogen peroxide is held for 4-6 hours. The target product is filtered off, washed with water and dried. The product yield 94 - 95.3%, counting on the starting hydrazine.

The invention is illustrated by the following examples:

Example 1

In a reaction flask with a capacity of 1 dm ³ equipped with a mechanical stirrer, reflux condenser, thermometer and dropping funnel, 340 cm ^{3 of} water, 0.06 g of neonol AF 9-10, 116.06 g of 99% acetone cyanohydrin, 32.68 g 65.6% hydrazine hydrate and incubated for 4 hours at 30-35 ° C. At the end of the exposure, cool the contents of the flask to 10-15 ° C, load 0.2 g of sodium tungstate, acidify to pH 1-2 and dose 3 cm ^{3 of} bromine and 88 cm ^{3 of} 34.8% hydrogen peroxide. It is maintained at 15-20 ° C until a yellow color appears. The target product is filtered off, washed with water, and dried.

105.2 g of 2,2'-azobisisobutyronitrile are obtained, which is 95% of theory, based on the starting hydrazine. Melting point 102-103.5 ° C.

Example 2

Under the conditions of Example 1, from 17.2 g of 99% acetoncyanohydrin, 50 cm ^{3 of} water, 0.017 g of syntamide-5, 4.89 g of 65.6% hydrazine hydrate, 0.038 g of sodium tungstate, 9.0 g 40 % hydrobromic acid and 13 cm ^{3 of} 34.8% hydrogen peroxide receive 15.65 g of 2,2'-azobasisobutyronitrile, which is 95.3% of theory, based on the original hydrazine. Melting point 102-104 ° C.

Example 3

Under the conditions of Example 1, from 17.2 g of 99% acetoncyanohydrin, 50 cm ^{3 of} water, 4.89 g of 65.6% hydrazine hydrate, 0.015 g of neonol AF 9-10, 0.03 g of ammonium metavanadate, 0 55 g of sodium bromide and 13 cm ^{3 of} 34.8% hydrogen peroxide give 15.55 g of 2,2'-azobisisobutyronitrile, which is 94.5% of theory, based on the starting hydrazine. Melting point 101.5 ° C.

Claims (1)

The method of producing 2,2'-azobisisobutyronitrile by the interaction of acetone cyanohydrin with hydrazine hydrate in an aqueous medium followed by oxidation of the intermediate 2,2'-hydrazobisisobutyronitrile with hydrogen peroxide in an acidic medium in the presence of bromine or its compounds using a catalyst - compounds of tungsten, vanadium, molybdenum, the fact that the oxidation process is carried out in the presence of surfactants in an amount of 0.05-1% of the loaded acetoncyanohydrin without isolation of the intermediate product.