Patent Application
20200165228
The invention relates generally to a new method of manufacturing potassium 1,1-dinitramino-5,5-bistetrazolate (“K2DNABT”) and to an explosive composition which includes K2DNABT.
K2DNABT was first synthesized in 2015 using a sophisticated synthetic process involving numerous steps as shown in
K2DNABT, however, shows a sensitivity towards impact, friction and electrostatic discharge and, to facilitate its safe handling and commercial use the product must be desensitized.
It is an objective of the invention to provide a method of making K2DNABT in a way that addresses the aforementioned shortcomings and to desensitize K2DNABT to allow practicable, safe and reliable deposition of an explosive mixture thereof onto a heating element to function as an igniter of explosives.
The invention provides a method of producing K2DNABT which includes the steps of:
Preferably, the nitrating agent is the 4:1 mixture of nitric acid with acetic anhydride.
Steps (a) and (b) may be combined in a first one-pot reaction step in which hydrazine hydrate reacts with dialkyl carbonate to form alkyl carbazate, and then glyoxal is added to produce dialkyloxy carbonyl glyoxal bishydrazone.
Steps (c) and (d) may be combined in a second one-pot reaction step in which the dialkyloxy carbonyl glyoxal bishydrazone is dissolved in a first solvent before the halogenating (step (c)) to form halogenated bishydrazone, and the azidation (step (d)) to form diazido dialkyloxycarbonylglyoxal bishydrazone.
In the step (e), the diazido dialkyloxycarbonylglyoxal bishydrazone may be dissolved in a second solvent before cyclization to produce bistetrazole intermediate.
Steps (d) and (e) may be combined in a second alternative one-pot reaction step in which halogenated bishydrazone is dissolved in a second solvent before the azidation (step (d)) to form the bistetrazole intermediate and the cyclization (step (e)) to form the nitramino intermediate.
The first solvent may be any of the following: DMF, DMSO, NMP, sulfolane, DMA, dioxane, water, EtOH, chloroform, MeOH, MeCN, THF, ethanol and water, and DMSO.
In the step (c) the halogenating agent may be N-chlorosuccinimide (NCS).
The azide in step (d) may be an earth metal azide, for example, sodium azide, lithium azide. Preferably, the azide is sodium azide.
The second solvent may be any of the following: DMF, ethanol, sulfolane, THF, MeCN, dioxane, chloroform. Preferably chloroform is used.
The ring closing electrophile may be selected from: HCl, SOCl2, POCl3, SO2Cl2, CO2Cl2, sulphuric acid and NaCl. Preferably, the electrophile is SOCl2 or HCl. The HCl, preferably, is in a 37% concentration.
The steps (f) and (g) may be combined in a third one-pot reaction step in which the bistetrazole intermediate and the nitrating agent are added to produce a reaction mixture which is then added to a solution of potassium hydroxide to produce K2DNABT.
The potassium hydroxide solution may be a 85 wt. % solution.
In the preparation of the nitrating agent of phosphorous pentoxide or nitric acid, phosphorous pentoxide may be added to nitric acid in a molar ratio 1:10 at a temperature in the range −15° C. to 5° C.
In the preparation of the nitrating agent of nitric acid with acetic anhydride, acetic anhydride may be added to nitric acid in a molar ratio between 1:3 and 1:4 at a temperature in the range −15° C. to 5° C.
In the step (a) the dialkyl carbonate may be dimethyl carbonate or diethyl carbonate. Preferably, diethyl carbonate is used.
In another aspect of the invention there is provided an explosive composition for use as an ignitable formulation which includes the following components in the following amounts:
The binder may be graphite.
The invention also extends to a method of producing the explosive composition which includes the steps of:
The binder may be graphite dust.
The energetic binder may be ethanolic nitrocellulose (NC).
The method may include an additional step, after step (d), of drying the explosive composition with a nitrogen gas stream to increase the viscosity of the composition.
The invention extends to a composition for use as an explosive igniter which includes the following components in the following amounts:
The final explosive product contains no heavy metals, and increases human safety, and decreases adverse environmental effects. The explosive has a relatively high VOD due to the high nitrogen/oxygen content.
The desensitization of the explosive product facilitates handling by lowering friction and impact sensitivity and facilitates handling of the explosive product. The liquid nature of the formulation also facilitates automated deposition of the formulation onto a heating element, for use in an explosive igniter. In contrast, a primary explosive like lead azide becomes more sensitive when combined with additives.
The invention is further described by way of examples with reference to the accompanying drawings wherein;
Methods 10A and 10B of producing K2DNABT are schematically illustrated in
The method 10A, shown in
The dimethoxy carbonyl glyoxal bishydrazone is subjected to a halogenating step 14A wherein the dimethoxy carbonyl glyoxal bishydrazone is reacted with a halogenating agent, N-chlorosuccinimide (NCS), to form dichloro dimethoxy carbonyl glyoxal bishydrazone. This step is shown in
In a step 18A (cyclization), diazido-dimethoxy carbonyl glyoxal bishydrazone is reacted with an electrophile, hydrochloric acid, to form dimethoxy carbonyl diaminobistetrazole as shown in
In a step 20A, dimethoxy carbonyl diaminobistetrazole is treated with a nitrating agent which comprises a mixture of nitric acid and acetic anhydride to form dimethoxy carbonyl dinitraminobistetrazole which is subsequently subjected to alkaline hydrolysis to form an end product, K2DNABT.
Overall the methods 10A and 10B have fewer synthesis steps than the method shown in
In a step 12A, shown in
A feature of the current invention lies in the combined steps 14A and 16A,
The above protocol, redone with a larger amount of DMF, leads to a slightly better yield of diazido-dimethoxy carbonyl glyoxal bishydrazone at 28%.
An improvement in the yield of the chloro/azido exchange, which occurs with intermediate dichloro dimethoxy carbonyl glyoxal bishydrazone, was sought by using other solvents or azido compounds. As an alternative azido compound, lithium azide could be used as a replacement to sodium azide in step 16A.
Other solvents used in the pre-halogenating step were evaluated by suspending dimethoxy carbonyl glyoxal bishydrazone in each of a variety of solvents (see Table 1) to assess if yield improved. Sodium azide was added to each of the suspensions drop by drop. The reaction mixture was stirred overnight and triple the amount of water was added. The precipitate (diazido-dimethoxy carbonyl glyoxal bishydrazone) was collected by filtration and air dried.
The highest yield obtained is with DMSO (65%), stirred overnight at room temperature. This is increased to an 80% yield with water/DSMO and the recovery of unreacted starting material.
Although DSMO produces the best yield, it is not a solvent of choice if step 14A and step 16A are combined in a one-pot reaction. Therefore a second series of tests was conducted with other solvents at temperatures between 35° C. and 100° C. (See Table 2).
This second series of tests resulted in improved yields of diazido-dimethoxy carbonyl glyoxal bishydrazone.
There are different possibilities for successful ring closing of diazido-dimethoxy carbonyl glyoxal bishydrazone to form dimethoxy carbonyl diaminobistetrazole shown in
Sulfolane, CHCl3, DMF, EtOH, amongst others, were tried as alternative solvents for the ring closing reaction to form dimethoxy carbonyl diaminobistetrazole.
In one example, the diazido-dimethoxy carbonyl glyoxal bishydrazone was suspended in chloroform and thionyl chloride was added. The mixture was heated to 55° C. for 48 hours. The dimethoxy carbonyl diaminobistetrazole was collected by suction filtration. However, ring closing worked best (yield: 90% after recrystallization) by adding 8.0 equivalents of SOCl2 (see Table 3).
Using EtOH, THF, dioxane and MeCN as alternative solvents, and SOCl2, and SO2Cl2, cyclization occurred with high yield.
Successful ring closure of diazido-dimethoxy carbonyl glyoxal bishydrazone with high yields of dimethoxy carbonyl diaminobistetrazole was also achieved using POCl3 and SO2Cl2 in chloroform—see batches 15-17 in the above Table 3.
In a preferable example, to achieve ring closure, diazido-dimethoxy carbonyl glyoxal bishydrazone is suspended in 37% HCl and heated overnight at 50° C. (batch 19). The product (dimethoxy carbonyl diaminobistetrazole) is clean and the yield is about 60%, which can be increased by a longer reaction time.
In another example, diazido-dimethoxy carbonyl glyoxal bishydrazone is suspended in sulfuric acid and sodium chloride is added incrementally. The mixture is stirred overnight at room temperature with water added. Dimethoxy carbonyl diaminobistetrazole is extracted with an organic solvent and a resulting mixture is then treated with ethyl acetate to remove the solvent and recover dimethoxy carbonyl diaminobistetrazole. The NMR spectra showed successful ring closing but with a low yield (17%) and residual starting material.
Alternatively, steps 16A and 18A can be combined in a one-pot reaction, without isolating the diazido-dimethoxy carbonyl glyoxal bishydrazone. Dichloro dimethoxy carbonyl glyoxal bishydrazone is used as a starting material and dimethoxy carbonyl diaminobistetrazole is isolated as an intermediate product.
For safety considerations, this one-pot reaction step is preferential.
The one-pot reaction step was tried with four different solvents: chloroform, ethanol, DMSO and DMF (see Table 4).
In each instance, dichloro dimethoxy carbonyl glyoxal bishydrazone is suspended in the chosen solvent and sodium azide is added at room temperature. The suspension is stirred overnight and SOCl2 is added. The reaction is heated at 55° C. for 2 days. In the case of ethanol, DMF and chloroform the solvent was removed in vacuo and the residue recrystallized in hot methanol. By using DMSO the mixture is diluted with water (150 mL) and extracted with EtOAc. The combined organic phases are dried over MgSO4 and the solvent removed.
From Table 4 it can be seen that the one-pot reaction step worked with DMSO (batch 3) and conc. HCl (batch 6). The challenge with DMSO is getting rid of the solvent which is achieved by extensive extractions with EtOAc.
The preferred example, in the one-pot step, is with HCl with a yield of 24%. This step is easy and includes cheap and readily available reagents. However, the yield is low and needs to be improved. Yield improvement may be achieved by a longer reaction time for the chloro/azido exchange or use of less concentrated hydrochloric acid.
The one-pot step is to be contrasted with a two-step process (step (b2) and step (c)) which yields of 60% for dimethoxy carbonyl diaminobistetrazole.
The scheme showed in
Dimethoxy carbonyl dinitraminobistetrazole has to be handled with care due to its sensitive behaviour towards impact (IS), friction (FS) and electrostatic discharge (ESD). Its sensitivity is similar to that of K2DNABT (see Table 5).
K2DNABT is prepared from dimethoxy carbonyl dinitraminobistetrazole by the alkaline hydrolysis of the protecting groups using a 2M potassium hydroxide solution.
The disadvantage with the prior art method (
An alternative nitrating agent is selected from nitric acid, dinitronium disulphate ((NO2)2S2O7), mixed acid (HNO3/H2SO4), nitric acid with phosphorous pentoxide (HNO3/P4O10) and nitric acid with acetic anhydride (HNO3/Ac2O). The dinitronium disulphate is prepared according to the method of Ingold et al, J. Org. Chem., 1950 using N2O5 and SO3.
Dinitronium disulphate replaces N2O5. This particular nitration agent is very similar to N2O5 and hydrolyses to one equivalent nitric acid and two equivalents of sulfuric acid upon contact with water.
In one example, dinitronium disulphate is dissolved in dry acetonitrile at 0° C. and dimethoxy carbonyl diaminobistetrazole is added. After 3 hours, a 2 M potassium hydroxide solution is added. Against all expectations, a two-phase system was obtained consisting of two solutions. Water was added until the liquid phases combined. Stirring is stopped and the solution was cooled to 0° C. After 1 hour no precipitate had formed and the synthesis attempt was a failure.
The experimental routine was repeated using 2.2 equivalents of dinitronium disulphate and the dimethyl carbonate of the reaction was doubled. This time, K2DNABT could be obtained with an unexpectedly low yield of only 19%.
Thus, (NO2)2S2O7 is unsuitable for the preparation of K2DNABT. The neutralization of 2.2 equivalents dinitronium disulphate requires excessive amounts of potassium hydroxide (2 M solution) due to the production of “mixed acid” upon contact with aqueous solutions. Large quantities of potassium sulphate are formed which is only slightly soluble at 0° C. and is less soluble than potassium nitrate. Hence, the removal of potassium sulphate requires large amounts of water. This results in the dissolution of most of the produced K2DNABT. This causes a decrease in the yield.
In another example, mixed acid comprising 1 part 100% nitric acid and 2 parts 100% sulfuric acid, is cooled to −10° C. and dimethoxy carbonyl diaminobistetrazole is added. The resulting suspension is stirred for 4 hours at an initial temperature and subsequently poured into an ice-cold solution of 85 wt.-% potassium hydroxide, comprising a necessary amount of water for the complete dissolution of formed potassium nitrate and potassium sulphate. A large amount of precipitate was formed which dissolved almost completely upon mechanical stirring. The solid material is collected by suction filtration
Setting the filter paper alight gave a loud report. This is an indication that K2DNABT is produced.
The problem with this example is that the amount of water needed for the complete dissolution of the inorganic by-products causes dissolution of K2DNABT.
The preceding example is repeated using more starting material dimethoxy carbonyl diaminobistetrazole (0.50 g, 1.76 mmol) in comparison to the amount of mixed acid (nitric acid: 14.1 mmol, 0.88 g, sulfuric acid: 28.2 mmol, 2.66 g). The work-up routine is performed in the same manner as described above. The results were the same and no solid residue could be collected after the suction filtration.
A further example uses dinitrogen pentoxide which is generated in situ by the reaction of 100% nitric acid with phosphorus pentoxide. Here, phosphorus pentoxide (0.80 g, 2.82 mmol) is added to nitric acid (1.78 g, 28.2 mmol) at 0° C. using an ice-bath. Dimethoxy carbonyl diaminobistetrazole (0.25 g, 0.88 mmol) is added to the resulting slurry and mechanically stirred for 6 hours at an initial temperature. The reaction mixture is then poured into an ice-cold solution of 85 wt.-% potassium hydroxide (4.09 g, 62.0 mmol) comprising an amount of water for the complete dissolution of formed potassium nitrate and potassium phosphate. The resulting suspension is stirred at 0° C. for 30 minutes and the remaining solid is collected using suction filtration to give K2DNABT (0.12 g, 0.36 mmol) with a yield of 43% without isolating dimethoxy carbonyl dinitraminobistetrazole.
The viscosity of the HNO3/P4O10 mixture hinders diffusion in the reaction mixture. Therefore, longer reaction times may be needed for higher yields.
Several mixtures of 100% nitric acid and acetic anhydride with varying ratios of the reactants were tested in the step 20A of dimethoxy carbonyl diaminobistetrazole.
It is considered that dinitrogen pentoxide causes the nitration which is formed in situ as follows:
HNO3+AcONO2≥AcOH+N2O5
After a screening of the various nitration agents, the following nitrating step 18A is preferred as it offers the highest yield and purity of K2DNABT.
Nitric acid (7.09 g, 0.11 mol) is cooled to −10° C. in a 25 mL round bottom flask using an ice bath. Acetic anhydride (2.84 mL, 30.03 mmol) is slowly added keeping the temperature below 0° C. Dimethoxy carbonyl diaminobistetrazole (1.00 g, 3.52 mmol) is added in small portions over a period of 10 minutes. After a reaction time of 1 hour a yellow solution is formed which turns into a yellowish suspension about 20 minutes later. After an overall reaction time of about 3 hours, the suspension is added to a solution of about 85% potassium hydroxide (11.40 g, 172.7 mmol) in 92.00 g of a 50:50 ice-water-mixture. Additional potassium hydroxide is added until pH 12 or higher is reached. A precipitate is formed which is collected by suction filtration, the precipitate is then washed with 2 mL of cold water and dried to yield 1.07 g (91° A) of K2DNABT without isolating dimethoxy carbonyl dinitraminobistetrazole.
The method 10A shown in
Following the preferred steps described above, but with a diethoxyl carbonate starting reagent, K2DNABT is successfully synthesized in this ethoxy group synthesis as shown in
Of interest are the sensitivity values (Table 8) of the azido compounds and ring closed compounds.
The sensitivity value of the diazido-dimethoxy carbonyl glyoxal bishydrazone and diazido-diethoxy carbonyl glyoxal bishydrazone differ and this is due to the protecting group. Consequently, the diazido-diethoxy carbonyl glyoxal bishydrazone is less sensitive towards friction and impact. Thus, it is easier and safer to handle. Dimethoxy carbonyl diaminobistetrazole and diethoxy carbonyl diaminobistetrazole have similar sensitivity values.
Therefore, the method 10B is preferred to the method 10A because of better yields, a less sensitive intermediate diethoxy carbonyl diaminobistetrazole, lower cost starting materials and better solubility of products.
The step 12B in the production of diethoxy carbonyl glyoxal bishydrazone (a combination of steps (a) and (b)) is illustrated in
The step 14B in the production of dichloro diethoxy carbonyl glyoxal bishydrazone is illustrated in
The step 16B in the production of diazido-diethoxy carbonyl glyoxal bishydrazone is illustrated in
In a final step 20B, illustrated in
Desensitization of the K2DNABT is necessary. Wax, graphite and silicone oil have been tested as possible desensitization agents. Experimentally, different mixtures of the respective desensitizers were added to K2DNABT and the corresponding sensitivities of the mixtures were determined (see Table 9).
The best result was achieved using graphite dust. A mixture of 30 wt.-% graphite causes a drastic decrease of the ESD sensitivity, but a mixture of 10 wt.-% graphite offers the best overlap of a decreased sensitivity and a low mixture of non-energetic material.
The mixture of K2DNABT and graphite is designated K2DNABT-G.
The loss of performance due to the mixture is estimated using the EXPLO5-code. The calculated value for K2DNABT-G (10% mixture):
Vdet.=8137 m/s, pCJ=26.97 GPa
A preferred method of desensitization is described below.
In a first step, K2DNABT (200 mg) is added to a plastic test tube and covered with 2 mL ethanol or acetone. Graphite dust (22.2 mg) is added and mechanical stirred for 2 hours. The stirring was stopped and the solvent is evaporated using a nitrogen gas stream.
In a second step, an energetic binder is applied to K2DNABT-G. K2DNABT-G is left in the plastic test tube and a pre-calculated amount of a 1 wt.-% (2468.9 mg) ethanolic nitrocellulose (NC) solution is added in order to achieve a mixture of 10 wt.-% binder. The resulting suspension is dried using a nitrogen gas stream until a viscous, sticky mass is obtained.
The mixture of K2DNABT-G thus includes the following components in the following amounts: K2DNABT: 85.50 wt.-%; graphite: 9.50 wt.-%; and Nitrocellulose NC: 5.00 wt.-%.
The method described above is varied with the addition of half of the NC-solution (1234.5 mg) in order to achieve a reduced binder content of 5 wt.-%. The obtained suspension is dried using a nitrogen gas stream until the mixture became viscous.
In this example, an optimal viscosity, for the application of the mixture is not achieved due to the reduced binder content. The degree of “polymer-swelling” is lower and the mixture is more difficult to handle.
In preparation of the ignition pill, a syringe or pipette is used to apply the sticky mass of K2DNABT-G to a series of the electronic igniters as shown in
The loaded igniters are then connected to a power supply (U=20.5 V) with an interposed capacitor. The capacitor is charged by the power supply and the corresponding energy (E=½%(CU2)) is discharged by a fire button causing an electric current in the detonator chip.
For this test, five igniters were prepared with a mixture of 10 wt.-% binder and five with a mixture of 5 wt.-% binder. Both mixtures had a 100% firing rate.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017/03279 | May 2017 | ZA | national |
This application is a U.S. national stage application of International Application No. PCT/ZA2018/050022 entitled “A METHOD FOR PRODUCING POTASSIUM 1,1-DINITRAMINO-5,5-BISTETRAZOLATE AND EXPLOSIVE COMPOSITIONS COMPRISING SAID SALT”, which has an international filing date of 10 May 2018, and which claims priority to South African Patent Application No. 2017/03279, filed 12 May 2017.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/ZA2018/050022 | 5/10/2018 | WO | 00 |
