Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2001-06-04
2002-08-13
Ramsuer, Robert W. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
active
06433181
ABSTRACT:
BACKGROUND OF THE INVENTION
1. (Field of the Invention)
The present invention relates to a process for the preparation of 5,5′-bi-1H-tetrazolediammonium salts. (BHT.2NH
3
) which are lowly toxic, easy to handle, and are useful as gas-generating agents for air bags and as high-molecular foaming agents.
2. (Prior Art)
5,5′-Bi-1H-tetrazoles (BHT) or salts thereof have a chemical structure expressed by the following formula (1),
wherein X is a hydrogen atom or a cation pair.
The following prior arts 1 and 2 have been known for synthesizing these compounds.
(Prior Art 1) Japanese Laid-Open Patent Application No. 2000-256332, U.S. Pat. No. 6,040,453 (2000).
The present invention inventors have already proposed the synthesis of a 5,5′-bi-1H-tetrazolediammonium salt from a dicyan and an aqueous solution of sodium azide/ammonium chloride by a reaction expressed by the following formula (2),
(Prior Art 2) Japanese Laid-Open Patent Application No. 2000-191649.
The present inventors have proposed the synthesis of a 5,5′-bi-1H-tetrazolediammonium salt (BHT.2NH
3
) from hydrogen cyanide, sodium azide and aqueous hydrogen peroxide by a reaction expressed by the following formula (3),
in the presence of a catalytic amount of copper sulfate while adjusting the pH of the reaction solution to be 5 to 6 by the addition of an organic acid such as acetic acid or formic acid.
According to the prior art 1, a 5,5′-bi-1H-tetrazolediammonium salt is synthesized by the heat cyclization reaction of the dicyan as a starting material with an aqueous solution of sodium azide/ammonium chloride.
This method, however, involves such defects as toxicity, use of the dicyan which is difficult to handle as a starting material, and an additional provision of a step for synthesizing the dicyan causing the reaction apparatus to become complex.
The prior art 2 is to isolate the 5,5′-bi-1H-tetrazolediammonium salt in the form of sparingly soluble crystals by the one-pot reaction by using hydrogen cyanide and sodium azide as starting materials while using copper sulfide as a catalyst and aqueous hydrogen peroxide as an oxidizing agent.
However, the obtained course crystals exhibit a blue color due to the presence of several thousands of ppm of copper that was used as the catalyst, and are never satisfactory concerning their purity and quality.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a process for the preparation of a 5,5′-bi-1H-tetrazolediammonium salt (BHT.2NH
3
) containing very decreased amounts of impurities such as of copper from a reaction solution containing a 5,5′-bi-1H-tetrazoledisodium salt synthesized in the presence of a copper catalyst.
Another object of the present invention is to provide a method of efficiently synthesizing a highly pure 5,5′-bi-1H-tetrazolediammonium salt (BHT.2NH
3
) through a decreased number of steps, i.e., through the one-pot reaction from the starting materials that are cheaply available and are easy to handle.
According to the present invention, there is provided a process for the preparation of a highly pure 5,5′-bi-1H-tetrazolediammonium salt by adding a small amount of aqueous ammonia to a reaction solution containing a 5,5′-bi-1H-tetrazoledisodium salt synthesized in the presence of a copper catalyst, by reacting an aqueous solution of ammonium chloride with a filtrate of the 5,5′-bi-1H-tetrazoledisodium salt obtained by removing by filtration the blue insoluble components of the formed copper.ammonia.5,5′-bi-1H-tetrazole complex, and by recovering the formed highly pure ammonium salts as sparingly soluble crystals.
According to the present invention, the reaction solution containing the 5,5′-bi-1H-tetrazoledisodium salt is obtained by synthesizing a dicyan by adding, as an oxidizing agent, a aqueous hydrogen peroxide to an aqueous solution of the starting materials of which the pH has been adjusted to be 5 to 7 by the addition of a small amount of acidic substance in the presence of hydrogen cyanide or sodium cyanide, sodium azide and a catalytic amount of a copper salt, followed by the heat-cyclization reaction.
It is further allowable to form a complex by adding a small amount of aqueous hydrogen peroxide together with a small amount of aqueous ammonia to the reaction solution that contains the 5,5′-bi-1H-tetrazoledisodium salt.
It is further desired to put the filtrate obtained by removing by filtration the blue insoluble components of the formed copper.ammonia.5,5-bi-1H tetrazole complex to the treatment with a chelating resin, followed by the reaction with an aqueous solution of ammonium chloride.
It is further allowable to react the reaction solution containing the 5,5′-b-1H-tetrazoledisodium salt with the aqueous solution of ammonium chloride, separate the formed 5,5′-bi-1H-tetrazolediammonium salt as copper-containing coarse crystals, react the course diammonium salt crystals with the aqueous solution of sodium hydroxide to convert it into an aqueous solution of the 5,5′-bi-1H-tetrazoledisodium salt which is dissolved therein, and remove by filtration the blue insoluble component of the copper.ammonia.5,5′-bi-1H-tetrazole complex, followed by refining by the treatment with a chelating resin.
According to the present invention, it is desired that the molar ratio of the hydrogen peroxide water added to the aqueous solution of starting material is increased so that the catalytic amount of copper salt migrates into the coarse 5,5′-bi-1H-tetrazolediammonium salt crystals that are to be separated, that the aqueous hydrogen peroxide is added to the reaction for the synthesis of the 5,5′-bi-1H-tetrazoledisodium salt in such an amount that the molar ratio (E/A) of the aqueous hydrogen peroxide (E) to the hydrogen cyanide or the sodium cyanide (A) used for the synthesis is from 0.5 to 0.8, and that, after the reaction of synthesizing the 5,5′-bi-1H-tetrazoledisodium salt, the hydrogen peroxide water is added to the reaction in such an amount that the molar ratio (H/A) of the aqueous hydrogen peroxide (H) to the hydrogen cyanide or the sodium cyanide (A) used for the synthesis is from 0.001 to 0.20.
It is further desired that the amount of the aqueous ammonia added to the reaction solution of the 5,5′-bi-1H-tetrazoledisodium salt is such that the molar ration (G/A) of the ammonia (G) to the hydrogen cyanide or the sodium cyanide (A) used for the synthesis is from 0.01 to 0.16.
As the acidic substance, there can be used organocarboxylic acids such as actic acid and formic acid, or mineral acids such as hydrochloric acid, sulfuric acid and nitric acid.
In the present invention, it is desired that the treatment with the chelating resin is conducted at a temperature of not lower than 40° C.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, a small amount of aqueous ammonia or a smaller amount of aqueous hydrogen peroxide is added to the reaction solution containing a 5,5′-bi-1H-tetrazoledisodium salt synthesized in the presence of a copper catalyst in order to separate the copper component in the reaction solution as a blue insoluble component of the copper.ammonia.5,5′-bi-1H-tetrazole complex.
That is, copper which is the catalyst and is a chief impurity component is removed by filtration as a blue insoluble component of the copper.ammonia.5,5′-bi-1H-tetrazole complex. Thus, most of copper in the coarse or crude crystals or in the reaction solution is easily removed and, hence, the copper content is decreased to 5 to 35 ppm in the 5,5′-bi-1H-tetrazolediammonium salt (BHT.2NH
3
) crystals obtained by the reaction with the aqueous solution of ammonium chloride.
Upon conducting the operation for refining the filtrate from which the insoluble components have been removed or for refining the solution in which coarse or crude crystals have been dissolved again with the chelating resin, further, it is allowed to prepare, at a high yield, a highly pure 5,5′-bi-1H-
Hyoda Shunji
Kita Masaharu
Nemugaki Shuichi
Sato Koki
Sugino Atsushi
Japan Hydrazine Co. Ltd.
Ramsuer Robert W.
Shameem Golam M. M.
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