CS244312B1 - 1,1-azobisformamide production method - Google Patents

Abstract

The present invention provides a process for producing 1,1'-azobisphamamide by oxidizing hydrazodicarbonamide with hydrogen peroxide in the presence of a strong acid and a bromine or iodine compound. The oxidation is carried out in the presence of 0.1 to 10 wt. a catalyst, calculated as hydrazodicarbonamide, from the group consisting of a sulphate, chloride, nitrate or oxygen containing a medium or iron compound. The oxidation takes place at a temperature of 25 to 90 ° C, preferably 45 to 70 ° C.

Description

The present invention provides a process for the production of 1,1‘-azobisphoramide (synonyms: azodicarbonamide, azodicarboxylic acid diamide, azodicarboxamide, azoplastone) which is used as an additive to plastics. It is most often used as a blowing agent for plastics and rubbers because it releases nitrogen when heated. Its decomposition products are not toxic substances.

Industrial production of azoplastone is most often based on 1,1‘-hydrazobisformamide (hydrazocarbonamide, hydrazocarboxamide).

This is oxidized with sodium dichromate or chlorine. The process of oxidation with dichromates has the disadvantage of having to treat the chromium sludge, since they contain Cr ions and Cr ^eh ions and admixtures of organic substances in addition to Cr ³⁺ ions. The processing of these sludges is laborious, converting them to chromium oxide is energy intensive. Working with dichromates is demanding not only from the ecological point of view. These compounds often cause eczema and contact with compounds. Chlorine can cause allergies and other health problems. Occupational diseases are increasingly occurring at relevant workplaces.

Chlorine oxidation of 1,1‘-hydrazobisformamide is particularly difficult for businesses that do not have a chlorine economy and a chlorine source.

Preferred 1,1'-hydrazobisformamide oxidizers include a 30 to 60% solution of peroxide in water. The oxidation itself can be carried out in an aqueous suspension and in the presence of bromine or iodine compounds, strong inorganic or organic acids, and optionally metal element oxides.

The influence of metal compounds (Cr, Mn, Zn, Co, Ni, W, Al, Snj on the decomposition temperature of azoplastone (NSR Pat. 2,341,928) is described in the literature. Oxidation occurs in the presence of compounds of these metals. hydrogen peroxide (35 wt.% H2O2) uses vanadium dioxide or tellurium dioxide (Japan Kokai 77 133 924), also selenium dioxide (Japan Kokai 73 32 830J), also in combination with bromine or iodine compounds.

The present invention provides a process for the preparation of 1,1‘-azobisformamide by oxidation of hydrazodicarboxamide with hydrogen peroxide in the presence of a strong acid and a bromine or iodine compound, which is carried out by oxidation of hydrazodicarboxamide in the presence of 0.1 to 10% by weight. a catalyst selected from the group consisting of sulphate, chloride, nitrate or oxygen containing a compound of the medium or iron, calculated on the hydrazodicarboxamide, wherein preferably the waste water is recirculated.

Ι, Γ-azobisformamide is prepared in high yield by oxidation of 1,1'-hydrazobisformamide in aqueous suspension with an aqueous solution of hydrogen peroxide in the presence of bromine or iodine compounds in a strong, most often inorganic acid environment under the catalytic action of medium or iron compounds which they serve as oxygen carriers. The metals may be used in the form of chlorides, sulphates, nitrates or oxygen-containing compounds, preferably copper (I) chloride, iron (II) chloride and / or copper (II) sulphate.

The concentration of the metal compound is in the range of 0.1 to 10% by weight. % to an oxidized hydrazo derivative, preferably 0.5 to 5 wt.

Bromine or iodine compounds, respectively. pure iodine which are soluble in the reaction system. More preferred are bromine compounds because bromine as a reagent is released more slowly in the system than iodine. In the case of bromine, unwanted effluents are not readily produced when released from the reaction mixture. The iodine is released more readily by oxidation of hydrogen iodide with hydrogen peroxide and is less reactive to the hydrazo derivative, leading to its sublimation from the reaction mixture.

MEX + H2SO4-ME2SO4 + 2HX (1) where

ME is Na, K

X is Br, J

2HX + H2O2 - X2 + 2H2O

R - NH - NH - R + X 2 -> R - N = N - R + 2HX (3) where

R is NH 2 -CO-

A great advantage in the use of bromine compounds is the use of medium or iron compounds over highly effective catalysts such as molybdenum or tungsten compounds. These extremely rapidly release bromine (reaction 2 J and this is not enough to react with the hydrazo derivative (reaction 3). Since reaction (2) is faster when using the compounds Mo and W as reaction (3), bromine and iodine are released from the reaction mixture. the use of the media and iron compounds is slower (2J) and is not released from the reaction mixture when bromine compounds are used.

Of the bromine-containing or iodine-containing compounds, sodium, potassium, lithium, ammonium, other water-soluble bromides or quaternary salts can be used. It is also possible to use the same salts of iodine, iodo-2,444-diacetic acid or pure iodine. These salts are applied in an amount of 0.1 to 5% by weight.

A further advantage of the process according to the invention is that the waste water from the oxidation is preferably returned to the next oxidation, in which the amount of the strong acid used, the bromine or iodine-containing compound as well as the media or iron compounds are reduced to 40%.

The oxidizing agent, hydrogen peroxide, is used at a concentration of 30 to 60% by weight. and in a molar ratio to the hydrazodicarboxamide of 1.05 to 1.5: 1.

Waste water from the oxidation can be returned to the reaction because oxidation only dilutes the reaction mixture at the expense of water released by the decomposition of hydrogen peroxide.

The oxidation is carried out in an acidic medium (pH - 0 to 0.1) in the presence of strong inorganic acids such as, in particular, hydrochloric, hydrobromic, sulfuric, but also nitric, phosphoric or organic acids, e.g. formic acid, acetic acid. The concentration of said acids in the reaction mixture ranges from 5 to 15% by weight. % HCl, HBr, H3PO4 and HNO3, 10 to 40 wt. for H2SO4 and for organic acids 5 to 20 wt. In the case of hydrobromic acid, the addition of a bromine compound is not necessary.

The optimum concentration of hydrazodicarbonamide in the oxidation mixture is 15 to 30 wt. A suitable reaction temperature is 25 to 90 ° C, preferably 45 to 70 ° C. The reaction time is directly temperature-dependent and ranges from 0.3 to 4 hours after the hydrogen peroxide feed.

Example 1

Claims (2)

To the oxidation apparatus, consisting of a three-necked flask equipped with a stirrer, a thermometer, a reflux condenser and a separating funnel, 250 ml of 8% HCl is added, 2.5 g of 97% HBr, 2 g of CuCl2 and mixed with 118 g (1 mol) of hydrazodicarbonamide. Then 125 g (1.1 mol) of a 30% hydrogen peroxide solution are metered in at a temperature of 50 to 55 ° C. The reaction mixture was warmed to 10 ° C and stirred for 2 h. It is then cooled to 30-35 [deg.] C., filtered off with suction and washed with water until neutral (washing water). After drying, 109 g of Ι, Γ-azobisformamide (94.0% yield on theory) are obtained. The purity is better than 98% by weight, the decomposition temperature is 200 to 205 ° C, the amount of gas released is 220 ml / g. Example 2 Into the oxidation apparatus of Example 1, a batch similar to Example 1 was used, instead of 2.5 g of 97% HBr, 5 g of NaBr was used. 125 g (1.1 mol) of 30 to 35% H 2 O 2 are metered in at a temperature of 50 to 55 ° C. After isolation of the product of Example 1, 110 g of 1,1-azobisformamide (94.5% of theory) of a purity of better than 98% by weight, with a decomposition temperature of 190 to 205 ° C, a gas evolution of 215 ml / g. Example 3 The oxidation is carried out in the apparatus of Example 1 using the batch and working procedure of Example 1. 2 g of FeCH together with 5 g of NaBr are used as catalyst. After isolation of the product of Example 1, 109 g of 1.1 azobisformamide (94% in theory of purity better than 96% by weight, decomposition temperature 190-205 ° C, gas evolution rate 220 ml / g) are obtained. Example 4 The oxidation is carried out in the apparatus of Example 1 with the batch and the process according to Example 1. 2 g of FeCH, followed by 5 g of NaBr are used as oxidation catalyst and then 125 g (1.1 moles) are added at 50-55 ° C. A further procedure is as in Example 1. 106 g (91.4% of theory) of 1,1'-azobisformamide of a purity of better than 96% by weight, with a decomposition temperature of 195 to 205 ° C, amount gas evolution 215 ml / g. Example 5 The oxidation is carried out in an oxidation apparatus with a batch and a process as described in Example 1. 2 g of CuSO4, followed by NaBr, are then used as the oxidation catalyst and then 125 g (1.1 g) are added at 50-55 ° C.