SE511675C2 - Methods to prepare dinitramide salts - Google Patents

Abstract

The invention relates to a method of producing organic dinitramide salts, for instance, guanidine dinitramide and guanylurea dinitramide starting from ammonium dinitramide (ADN). A concentrated aqueous solution of ADN is reacted with a concentrated aqueous solution of an organic salt, whose anion is OH<-> or CO3<2-> which is capable of taking up a proton from the ammonium ion of ADN and transferring said ion to ammonia. The formed by-products, i.e. ammonia and possibly carbonic acid, are driven off from the solution, as well as a certain amount of water to maintain a concentrated solution. The organic dinitramide salt is then precipitated, for instance by cooling the solution. The method can be carried out as a continuous or semicontinuous process in a reactor (3), to which concentrated aqueous solutions of ADN (1) and organic salt (2), respectively, are supplied in equimolecular amounts. The solution is transferred from the reactor to a precipitation tank (7) where organic dinitramide salt (16) is precipitated and a supernatant is recirculated to the reactor.

Description

511 675 2 10 15 20 25 30 35 The invention is defined by the claims.

According to the invention, the organic dinitramide salt is prepared by reacting a concentrated aqueous solution of ADN with a concentrated aqueous solution of an organic salt, the anion of which is OH 'or CO32' capable of taking up a proton from the ammonium ion of ADN and converting said ion to ammonia; that ammonia and, where appropriate, carbon dioxide are driven off from the aqueous solution and that the solution is concentrated, if necessary, by evaporation of a certain amount of water and that the organic dinitramide salt precipitates out of the aqueous solution.

During the reaction, ammonia and water are formed resp. carbon dioxide that can be easily driven off from the solution. Only a solution of the organic dinitramide salt remains, which spontaneously precipitates when the saturation limit is exceeded.

The by-products can be evaporated off by heating the solution, possibly under reduced pressure if the desired organic dinitramide salt is sensitive to heat.

In addition to ammonia and, where appropriate, carbon dioxide, a certain amount of water is driven off if necessary to give the solution a desired degree of saturation with respect to the organic dinitramide salt. The solution can then be cooled to precipitate dinitramide salt.

The process is primarily intended for the preparation of dinitramide salts which have an organic nitrogen-containing cation. These salts often have properties which in various contexts make them suitable as explosives and as component propellants, explosives and pyrotechnic compositions. It is especially preferred to use the carbonates of these nitrogen-containing compounds in the process. Some of them may also be too sensitive to alkali for hydroxides to be produced.

Guanylurea dininitramide, as described in Swedish patent application 9701897-2, and guanidine dinitramide can advantageously be prepared according to the process in which guanylurea carbonate and guanidine carbonate, respectively, are preferred as starting material.

The process can be operated as a continuous or semi-continuous process using a single coherent and substantially closed water system, which is described in the following in connection with the attached figure 10 15 20 25 30 35 511 675 Fig. 1 schematically shows an example of a process set-up for continuous or semi-continuous production of organic dinitramamide salts according to the invention.

Figure 1 shows a first storage container 1 for a concentrated aqueous solution of ADN; a second storage container 2 for a concentrated aqueous solution of an organic salt in the form of its hydroxide or carbonate; a reactor 3, which is provided with an exhaust duct 4, a heating device 5 and a stirrer 6; and a precipitation tank 7, the bay is provided with a cooling device 8 and a stirrer 9.

Via lines 10 resp. 11 and dosing pumps 12 resp. 13 equimolecular amounts of DNA solution are pumped resp. organic brine continuously or intermittently to the reactor 3 where the solutions are mixed. The basic anion of the organic salt (OH 'or CO32) reacts with the ammonium ion of ADN and ammonia and water or carbonic acid are formed. The reaction mixture is heated in the reactor with the heating device 5, whereby ammonia and, if applicable, carbon dioxide (from the carbonic acid) are driven off via the exhaust channel 4. A certain amount of water is normally also driven off so that the solution remains concentrated with respect to the organic dinitramide salt. Of the concentrated solution in the reactor 3, a certain amount is pumped continuously or intermittently via the line 14 and the pump 15 to the precipitation tank 7 where the solution is cooled with the cooling device 8. Organic dinitramide salt 16 then precipitates when the saturation limit is exceeded and can be taken out via an outlet 17. A certain amount of the concentrated supernatant in the precipitation tank is pumped continuously or intermittently via a filter 18, the line 19 and the pump 20 back to the reactor 3.

The invention will be illustrated by way of example below.

Example 1.

Solution 1: 2.0 g of ADN was dissolved in 0.7 ml of water.

Solution 2: 1.45 g of guanidine carbonate was dissolved in 4.5 ml of water.

The solutions were mixed to form a precipitate immediately. The smell of ammonia could be detected. The precipitate was filtered off, washed 3 times with ice water and dried in a friend's cupboard. The precipitate was identified by spectroscopic methods such as guanidine dinitramide.

Example 2: Solution 1: 10.0 g of ADN was dissolved in 6 ml of water Solution 2: 7.5 g of guanidine carbonate was dissolved in 20 ml of water.

Solution 2 was heated and solution 1 was added with stirring. Carbon dioxide evolution and emission of ammonia could be ascertained. Upon cooling the solution, a white precipitate of guanidine dinitramide precipitated immediately. The precipitate showed high purity.

Claims (5)

10 15 20 25 511 675 Patent claims: Process for preparing organic dinitramide salts characterized in that a concentrated aqueous solution of ADN is reacted with a concentrated aqueous solution of an organic salt, the anion of which is OH 'or CO32' capable of taking up a proton from the ammonium ion of ADN and transferring said ion to ammonia; that ammonia and, where appropriate, carbon dioxide are driven off from the aqueous solution and that the solution is concentrated, if necessary, by evaporation of a certain amount of water and that the organic dinitramide salt precipitates out of the aqueous solution. Process according to Claim 1, characterized in that the anion of the organic salt is carbonate. Process according to Claim 1, characterized in that the cation of the organic salt is a nitrogen-containing cation. A method according to claim 3, characterized in that the nitrogen-containing cation is selected from a group consisting of guanidine ion and guanyl urea ion. 5. A method according to claim 1, characterized in that the concentrated aqueous solutions of ADN resp. organic salt is mixed in a reactor (3); that the reaction mixture is heated to evaporate ammonia, ev. carbon dioxide and a certain amount of water; that the reactor is continuously or intermittently filled with concentrated aqueous solutions of ADN resp. organic salt equimolecular amounts and that solution is continuously or intermittently transferred from the reactor (3) to a precipitation step (7); that the solution is cooled in the precipitation step to obtain a precipitate (16) of the organic dinitramide salt and a supernatant concentrated on the organic dinitramide salt, and that supernatant is continuously or intermittently returned to the reactor (3).