Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2002-06-27
2003-10-21
Vollano, Jean F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
Reexamination Certificate
active
06635785
ABSTRACT:
This application is a 371 of PCT/KR00/00180 filed Mar. 7, 2000, now WO 01/49652.
1. Technical Field
The present invention relates to a method of synthesizing hydrazodicarbonamide, and more particularly, to a method for synthesizing hydrazodicarbonamide in high yield at low cost.
2. Background Art
Hydrazodicarbonamide has been used as a source material for azodicarbonamide which is a widely used azo series foaming agent. The following reaction 1 shows that azodicarbonamide (2) can be synthesized by oxidizing hydrazodicarbonamide (1) with an appropriate oxidizing agent.
Hydrazodicarbonamide (1) is derived from a reaction of hydrazine (3) and urea (4), which is shown in the following reaction 2.
The synthesis of hydrazine, which is one of the reactants, is very expensive and complicate, while urea can be relatively easily obtained at low cost.
Typically, hydrazine is synthesized by the Raschig Process or a method using ketazine. However, hydrazine synthesized by these methods should be subjected to additional condensation or hydrolysis, and wastes huge energy and requires complicate equipment, thus increasing the manufacturing cost.
Another synthesis method of hydrazine is the urea process. According to the urea process, hydrazine is obtained by a reaction between urea and sodium hypochlorite, which is expressed as the following reaction 3.
However, such a urea process consumes excess sodium hydroxide and produces sodium carbonate as a byproduct, which must be eliminated. Due to the cost and energy required for the elimination of sodium carbonate, the production cost of hydrazine is inevitably increased, adversely affecting in an environmental aspect.
Synthesis of hydrazodicarbonamide by the urea process is expressed as the following reaction 4.
Reaction 4 shows that excess reactants, including 3 moles of urea, 4 moles of sodium hydroxide and 1 mole of chlorine (Cl
2
), are consumed for producing 1 mole of hydrazodicarbonamide.
As previously described, using hydrazine for the synthesis of hydrazodicarbonamide is an expensive and complicated process, and is undesirable in an environmental aspect.
Another approach for the synthesis of hydrazodicarbonamide is to use semicarbazide instead of the expensive hydrazine. The following reaction 5 illustrates the synthesis of semicarbazide. Urea and sodium hypochlorite are reacted to obtain monochlbrourea sodium salt as an intermediate and then reacted with excess ammonia in the presence of a catalyst to give semicarbazide.
However, the problem with this reaction is the need for excess ammonia. The amount of ammonia required is about 500 times the intermediate, monochlorourea sodium salt. Alternatively, an expensive catalyst should be used instead of reducing the amount of ammonia added for the reaction, thus raising the cost.
In addition, on more additional reaction for conversion of the obtained semicarbazide to hydrazodicarbonamide is required, which is expressed as the following reaction 6.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a method of synthesizing a great yield of hydrazodicarbonamide in a simple and inexpensive manner.
The above object of the present invention is achieved by a method for synthesizing hydrazodicarbonamide by a reaction of monohalobiuret metal salt having the formula 1 or 2, and ammonia in a solvent
where M is a metal and X is a halogen.
The above object and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof.
BEST MODE FOR CARRYING OUT THE INVENTION
An example of the synthesis of hydrazodicarbonamide (HDCA) according to the present invention is expressed as the following reaction 7.
where M is a metal and X is a halogen.
In Reaction 7, monohalobiuret metal salt as a reactant may be derived by reacting the biuret having the formula 3 below with a metal hypohalogen compound, or by reacting the biuret with a halogen element and a base.
The synthesis reaction for HDCA according to the present invention may be carried out at a temperature of 30 to 150° C.
For Reaction 7 ammonia may be liquid ammonia, gaseous ammonia or ammonia water, but liquid ammonia is preferred. If ammonia water is selected as a source of ammonia, the concentration of ammonia water may be in the range of 10 to 50%.
The amount of ammonia used may be 1 to 1000 moles, but preferably 2 to 500 moles, with respect to 1 mole of monohalobiuret metal salt.
The solvent for Reaction 7 may be water or a solvent mixture containing water and an organic solvent, but water is preferred. If the solvent mixture is selected, the organic solvent may be at least one selected from the group consisting an aprotic polar solvent and a protic polar solvent having a dielectric constant of 50 or less. For example, the organic solvent includes methanol, ethanol, propanol, isopropanol, dimethylformamide, tetrahydrofuran and acetonitrile.
Preferably, the amount of organic solvent is 0.1 to 50 times by weight, but preferably 0.2 to 3.0 times by weight based on the amount of water.
A catalyst may be further added for reduction of reaction time and reaction efficiency. The catalyst may be sulfates, chlorides, carbonates and hydroxides of transition metal or alkali metal, and heavy metal salts of carboxylic acids. The amount of catalyst added may be 0.001 to 1 moles, but preferably 0.01 to 0.5 moles, with respect to 1 mole of monohalobiuret metal salt.
Alternatively, an inorganic acid such as hydrochloric acid, sulfuric acid and nitric acid may be used as a catalyst. Preferably, the amount of inorganic catalyst is 0.5 to 3.0 moles with respect to 1 mole of monohalobiuret metal salt.
In the reactions of the present invention, preferably the metal designated M is sodium, potassium or calcium, and the halogen element designated X is fluorine, chlorine, bromine or iodine.
Hereinafter, the synthesis of HDCA according to the present invention will now be described.
Monohalobiuret metal salt having the formula 1 or 2 hereinabove, as a reactant for the synthesis of HDCA, are prepared by a variety of methods.
One of these methods is to directly react biuret with a metal hypohalogen, compound, which is expressed as the following reaction 8
where M is a metal and X is a halogen.
For example, chlorobiuret sodium salt is directly derived from biuret and sodium hypochlorite as expressed in the following reaction 9
Since Reaction 9 is a kind of exothermic reaction, it is preferable to keep the temperature of the reaction system at low temperatures. Due to thermal stability of chlorobiuret sodium salt produced, the above reaction may be carried out at room temperature, but preferably, within the range of −5 to 35° C.
As for the amount of reactants, preferably, 0.1 to 2 moles of sodium hypochlorite is added with respect to 1 mole of biuret in terms of the reaction efficiency and ease of handling. The produced chlorobiuret sodium salt may be readily used or may be reserved for use in a subsequent reaction.
As another method of preparing monohalobiuret metal salt, biuret is reacted with a halogen element (X
2
) such as chlorine (Cl
2
) or a halogen compound to obtain monohalobiuret (5), and a base, but preferably a metal hydroxide such as sodium hydroxide, potassium hydroxide or calcium hydroxide is then added to give monohalobiuret metal salt as a reactant for the synthesis of HDCA according to the present invention, which is expressed as the following reaction 10
where M is a metal and X is a halogen.
Since the halogenation of biuret for monohalobiuret 5 is also a kind of exothermic reaction, it is preferable to keep the reaction temperature at low temperatures, but more preferably, within the range of −5 to 30° C. in terms of the stability of the reaction.
As a modification of Reaction 10, biuret is mixed with a metal hydroxide and then reacted with halogen to give monohalobiuret metal salt. Since this reaction is also an exothermic reaction, it is preferable to keep the reaction temperature at low temperatures, but more preferably, within the range of −5 to 30° C.
Monoh
Han Sang-Jin
Lee Chun-Hyuk
J&J Chemical Co., Ltd.
Staas & Halsey , LLP
Vollano Jean F.
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