Precipitation method and synthesis method of 2,6-diamino-3,5-dinitropyrazine-1-oxide

Abstract

A method for precipitating as particles 2,6-diamino-3,5-dinitropyrazine-1-oxide (or ANPZO) present in an acid medium, which comprises adding the acid medium to an aqueous solution and which is characterized in that the aqueous solution comprises a nitrate salt. Further disclosed is a method for synthesizing ANPZO implementing this precipitation method. The synthesis method comprises converting 2,6-diaminopyrazine-1-oxide (or DAPO) into ANPZO by nitration in an acid medium, and then precipitating as particles the ANPZO by adding the acid medium to an aqueous solution, and is characterized in that the aqueous solution comprises a nitrate salt.

Claims

1. A method for precipitating as particles 2,6-diamino-3,5-dinitropyrazine -1-oxide present in an acid medium, the medium comprising nitric acid or a nitrate salt or a mixture thereof, and at least one strong acid other than nitric acid, the method comprising adding the acid medium to an aqueous solution comprising a nitrate salt; and precipitating as particles 2,6-diamino-3,5-dinitropyrazine-1-oxide.

2. A method for synthesizing particles of 2,6-diamino-3,5-dinitropyrazine -1-oxide, comprising: converting 2,6-diaminopyrazine-1-oxide into 2,6-diamino-3,5-dinitroyrazine-1-oxide by nitrating 2,6-diaminopyrazine-1-oxyde in an acid medium comprising nitric acid or a nitrate salt or a mixture thereof, and at least one strong acid other than nitric acid, and then precipitating as particles 2,6-diamino-3,5-dinitropyrazine-1-oxide by adding the acid medium to an aqueous solution comprising a nitrate salt.

3. The method of claim 1, wherein the nitrate salt is sodium nitrate, potassium nitrate or ammonium nitrate.

4. The method of claim 1, wherein the aqueous solution comprises between 110 g and 2,500 g of the nitrate salt for 1 litre of water.

5. The method of claim 1, wherein a ratio of a volume of the aqueous solution to a volume of the acid medium is comprised between 0.5 and 10.

6. The method of claim 1, wherein the acid medium is gradually added to the aqueous solution.

7. The method of claim 1, further comprising collecting the particles, washing the particles and drying the particles.

8. The method of claim 2, wherein converting 2,6-diaminopyrazine -1-oxide into 2,6-diamino-3,5-dinitropyrazine-1-oxide comprises: forming a reaction medium by adding nitric acid or a nitrate salt or a mixture thereof to a solution comprising 2,6-diaminopyrazine-1-oxide in at least one strong acid other than nitric acid; and maintaining the reaction medium under stirring.

9. The method of claim 1, wherein the strong acid other than nitric acid is sulfuric acid.

10. The method according to claim 9, wherein the acid medium comprises nitric acid and sulfuric acid.

11. The method of claim 2, wherein the nitrate salt is sodium nitrate, potassium nitrate or ammonium nitrate.

12. The method of claim 2, wherein the aqueous solution comprises between 110 g and 2,500 g of the nitrate salt for 1 litre of water.

13. The method of claim 2, wherein a ratio of a volume of the aqueous solution to a volume of the acid medium is comprised between 0.5 and 10.

14. The method of claim 2, wherein the acid medium is gradually added to the aqueous solution.

15. The method of claim 2, further comprising collecting the particles, washing the particles and drying the particles.

16. The method of claim 2, wherein the strong acid other than nitric acid is sulfuric acid.

17. The method according to claim 16, wherein the acid medium comprises nitric acid and sulfuric acid.

Description

SHORT DESCRIPTION OF THE FIGURES

(1) FIG. 1 is an image taken with a scanning electron microscope (or SEM) showing the particles of a first ANPZO synthesized by the synthesis method of the invention.

(2) FIG. 2 is an SEM image showing the particles of a second ANPZO synthesized by the synthesis method of the invention.

(3) FIG. 3 is an SEM image showing the particles of a third ANPZO synthesized by the synthesis method of the invention.

(4) FIG. 4 illustrates the DSC thermogram for the ANPZO, the particles of which are shown in FIG. 3; the heat flux, noted as and expressed in W/g, is indicated on the axis of ordinates, while the temperature, noted as and expressed in C. is indicated on the axis of abscissas.

(5) FIG. 5 is an SEM image showing the particles of a fourth ANPZO synthesized by the synthesis method of the invention.

(6) FIG. 6 is the chromatogram obtained by high performance liquid chromatography (or HPLC) for the ANPZO, the particles of which are shown in FIG. 5; the absorbance, noted as A and expressed in milli-units of absorbance (mUA), is indicated on the axis of the ordinates, while the time, noted as t and expressed in minutes, is indicated on the axis of the abscissas.

(7) FIG. 7 is an SEM image showing the particles of a fifth ANPZO synthesized by the synthesis method of the invention.

(8) FIG. 8 is an SEM image showing the particles of a sixth ANPZO synthesized by the synthesis method of the invention.

(9) FIG. 9 is an SEM image showing the particles of a seventh ANPZO synthesized by the synthesis method of the invention.

(10) FIG. 10 is an SEM image showing as a comparison the particles of a eighth ANPZO synthesized by a synthesis method which differs from the synthesis method of the invention in that the precipitation of ANPZO was achieved by addition of a sulfonitric medium comprising ANPZO in water at 30 C.

DETAILED DISCUSSION OF PARTICULAR EMBODIMENTS

(11) Preliminary Remarks:

(12) The SEM images which are shown in FIGS. 1 to 3, 5 and 7 to 10 were obtained with a scanning electron microscope FEI Versa 3D, at a magnification of 500.

(13) The DSC thermogram which is shown in FIG. 4 as well as the initial decomposition temperatures (or .sub.onset) which are indicated in table 1 hereafter were obtained with a calorimeter TA Instruments Q100 (heating rate: 10 C./min).

(14) The HPLC chromatogram which is shown in FIG. 6 was obtained by using a column Kinetex C18 (Phenomenex SAS) and UV detection at 320 nm.

(15) The sizes of the particles which are indicated in table 1 hereafter were measured by laser diffraction particle size measurements with a granulometer Malvern Mastersizer S (lens 300 RF; 0.1-900 m). The measurements were conducted via a liquid route (water without any surfactant) and with dispersion by treatment with ultrasonic waves. On the one hand, the main modes, i.e. the sizes where the maximum frequencies of the granulometric histograms are located (the distributions being monomodal), and, on the other hand, the median sizes (d0.5) by volume are indicated in table 1. To the extent that the ANPZO particles are not spheres, these sizes correspond to the diameters which spheres having the same volume as these particles would have.

(16) The stability values in vacuo at 140 C. which are indicated in table 1 hereafter were measured by subjecting samples of ANPZO to a heating to 140 C. in vacuo for 70 hours and by measuring the total released gas volume (expressed at a pressure of 1,013 hPa and at a temperature of 0 C.) by these samples during the heating period. They are expressed in cm.sup.3 per gram of sample. The test sample is 5 g.

(17) The rates of volatile materials on dry product which are indicated in table 1 hereafter were measured by subjecting the dry ANPZO samples to heating at 120 C. in an oven for 16 hours. They are expressed in percentages obtained by the formula: [(mass before testmass after test)/mass before test]100. The test sample is 5 g.

(18) The residual nitrate ion contents (or Q.sub.NO3-) which are indicated in table 1 hereafter were determined by nuclear magnetic resonance (or NMR) with a spectrometer Advance Bruker WB (400 MHz; probe 10 mm in .sup.14N). They are expressed in mass percentages obtained by the formula 12600*(I.sub.NO3-/I.sub.N2)*[N.sub.2eq]*f/[ANPZO] wherein I.sub.NO3-/I.sub.N2 is the intensity ratio between the NO.sub.3.sup. line and the N.sub.2 line; [N.sub.2eq] is the equilibrium concentration of N.sub.2 in dimethylsulfoxide in mmol/L; f is a corrective factor and [ANPZO] is the concentration of ANPZO in the sample in mg/L.

(19) The elemental analyses for which the results are indicated in table 1 hereafter were conducted with an elemental analyzer Flash EA 1112 (Thermofischer Scientific).

(20) The thermomechanical tests for which the results are indicated in table 1 hereafter were conducted by means of a device called a press with limits. This device, which is notably described in D. Lemoine et al., Europyro 1995, Jun. 5-9, 1995, Tours, France, and in P. Reynier, Joint International Symposium on Energetic Materials Technology, Oct. 5-7, 1992, New Orleans, USA, hereafter references [6] and [7], gives the possibility of evaluating the reactive behavior of an energy material subject to heating in a confined medium. Thus are measured: 1) the temperature, noted as .sub.decomp. in table 1, at which a sample of ANPZO is broken down when it is subject to a pressure of 500 bars (temperature rise ramp: 2 C./min), and 2) the time, noted as t.sub.decomp in table 1, at the end of which a sample of ANPZO is broken down at 220 C. under a pressure of 500 bars.

Example 1: Synthesis of ANPZO by the Synthesis Method of the Invention

(21) In a flask provided with a thermometer and a stirrer, 960 mL of sulfuric acid concentrated to 95-98% and then 112.9 g of DAPO portionwise are introduced. After dissolution of the DAPO dissolved in the sulfuric medium, 169.4 g of nitric acid concentrated to 99% are added slowly while maintaining the flask at a temperature below 35 C. The reaction medium is left under stirring for 2 hours, at room temperature.

(22) This reaction medium is then added portionwise to 3.35 L of an aqueous solution comprising 600 g of ammonium nitrate for 1 L of water while maintaining the temperature of the flask at 30 C.

(23) A precipitate is formed which is recovered by filtration and which is washed on the filter with water and then with an aqueous solution saturated with sodium bicarbonate (NaHCO.sub.3) and then again with water.

(24) Thus 95 g of humid ANPZO are obtained which are divided into two batches: a first batchhereafter batch 1which is dried without subjecting it to additional washing, whereby 38.08 g of dry ANPZO are obtained, and a second batchhereafter batch 2which is subject to two additional washings, the first with water at 80 C. and the second with a water/methylethylketone mixture (1/9, v/v) at 75 C., before drying it, whereby 50.42 g of dry ANPZO are obtained.

(25) The yield of this synthesis is 46% (88.5 g).

(26) The batches 1 and 2 of ANPZO are subject to a series of analyses: SEM, DSC, particle size analyses, measurement of the stability in vacuo at 140 C., measurement of the volatile material rate on dry product, measurement of the residual nitrate content, elemental analyses and thermomechanical tests.

(27) The SEM images showing particles of both of these batches of ANPZO are illustrated in FIGS. 1 and 2 respectively, while the results of the other analyses are indicated in table 1 hereafter.

Example 2: Synthesis of ANPZO by the Synthesis Method of the Invention

(28) In a flask provided with a thermometer and a stirrer, 3.84 L of sulfuric acid concentrated to 95-98% and then 452.2 g of DAPO portionwise are introduced. After dissolution of the DAPO in the sulfuric medium, 678.8 g of nitric acid concentrated to 99% are slowly added while maintaining the flask at a temperature below 35 C. The reaction medium is left under stirring for 2 hours at room temperature.

(29) This reaction medium is then added portionwise to 12.9 L of an aqueous solution comprising 600 g of ammonium nitrate for 1 L of water while maintaining the temperature of the precipitation medium around 30 C.

(30) A precipitate is formed which is recovered by filtration and which is washed on the filter with water and then with an aqueous solution saturated with NaHCO.sub.3 and then again with water.

(31) The thereby obtained humid ANPZO is subject to two additional washes, the first with water at 80 C. and the second with a water/methylethylketone mixture (1/9, v/v) at 75 C., and then to a drying, whereby 342 g of dry ANPZO are obtained (yield: 44%).

(32) This ANPZO is subject to a series of analyses: SEM, DSC, particle size analyses, measurement of the stability in vacuo at 140 C., measurement of the volatile material rate on dry product, measurement of the residual nitrate content, elemental analyses and thermomechanical tests.

(33) The SEM image showing the particles of this ANPZO is illustrated in FIG. 3. Its thermogram is illustrated in FIG. 4 while the other analyses are indicated in table 1 hereafter.

Example 3: Synthesis of ANPZO by the Synthesis Method of the Invention

(34) The same operating protocol as the one described in Example 2 hereinbefore is followed except that the humid ANPZO is only subject to a single additional wash (instead of two), i.e. the wash with water at 80 C., whereby 356 g of dry ANPZO are obtained (yield: 46%).

(35) This ANPZO is subject to a series of analyses: SEM, DSC, particle size analyses, measurement of the stability in vacuo at 140 C., measurement of the volatile material rate on dry product, measurement of the residual nitrate content, elemental analyses and thermomechanical tests. It is further subject to a HPLC chromatography.

(36) The SEM image showing the particles of this ANPZO is illustrated in FIG. 5. Its HPLC chromatogram is illustrated in FIG. 6, while the results of the other analyses are indicated in table I hereafter.

Example 4: Synthesis of ANPZO by the Synthesis Method of the Invention

(37) In a flask provided with a thermometer and a stirrer, 4.9 L of sulfuric acid concentrated to 95-98% and then 577.3 g of DAPO portionwise are introduced. After dissolution of the DAPO in the sulfuric medium, 865.5 g of nitric acid concentrated to 99% are slowly added while maintaining the flask at a temperature below 35 C. The reaction medium is left with stirring for 2 hours, at room temperature.

(38) This reaction medium is then added portionwise to 17.1 L of an aqueous solution comprising 250 g of ammonium nitrate for 1 L of water while maintaining the temperature of the precipitation medium around 30 C.

(39) A precipitate is formed which is recovered by filtration and which is washed on the filter with water and then with an aqueous solution saturated with NaHCO.sub.3 and then again with water.

(40) The thereby obtained humid ANPZO is subject to an additional wash with water at 80 C., and then to a drying, whereby 474 g of dry ANPZO are obtained (yield: 48%).

(41) This ANPZO is subject to a series of analyses: SEM, DSC, particle size analyses, measurement of the stability in vacuo at 140 C., measurement of the volatile material rate on dry product, measurement of the residual nitrate content, elemental analyses and thermomechanical tests.

(42) The SEM image showing the particles of this ANPZO is illustrated in FIG. 7 while the results of the other analyses are indicated in table I hereafter.

Example 5: Synthesis of ANPZO by the Synthesis Method of the Invention

(43) In a flask provided with a thermometer and a stirrer, 3.84 L of sulfuric acid concentrated to 95-98% and then 452.2 g of DAPO portionwise are introduced. After dissolution of the DAPO in the sulfuric medium, 678 g of nitric acid concentrated to 99% are slowly added while maintaining the flask at a temperature below 35 C. The reaction medium is left with stirring for 2 hours, at room temperature.

(44) This reaction medium is then added portionwise to 13.4 L of an aqueous solution comprising 260 g of potassium nitrate for 1 L of water while maintaining the temperature of the precipitation medium around 30 C.

(45) A precipitate is formed which is recovered by filtration and which is washed on the filter with water and then with an aqueous solution saturated with NaHCO.sub.3 and then again with water.

(46) The thereby obtained humid ANPZO is subject to an additional wash with water at 80 C., and then to a drying, whereby 340 g of dry ANPZO are obtained (yield: 44%).

(47) This ANPZO is subject to series of analyses: SEM, DSC, particle size analyses, measurement of the stability in vacua at 140 C., measurement of the volatile material rate on dry product, measurement of the residual nitrate content, elemental analyses and thermomechanical tests.

(48) The SEM image showing the particles of this ANPZO is illustrated in FIG. 8 while the results of the other analyses are indicated in table 1 hereafter.

Example 6: Synthesis of ANPZO by the Synthesis Method of the Invention

(49) In a flask provided with a thermometer and a stirrer, 3.84 L of sulfuric acid concentrated to 95-98% and then 452.2 g of DAPO portionwise are introduced. After dissolution of the DAPO in the sulfuric medium, 678 g of concentrated nitric acid to 99% are slowly added while maintaining the flask at a temperature below 35 C. The reaction medium is left under stirring for 2 hours at room temperature.

(50) This reaction medium is then added portionwise to 13.4 L of an aqueous solution comprising 570 g of sodium nitrate for 1 L of water while maintaining the temperature of the precipitation medium around 30 C.

(51) A precipitate forms which is recovered by filtration and which is washed on the filter with water and then with an aqueous solution saturated with NaHCO.sub.3 and then again with water.

(52) The thereby obtained humid ANPZO is subject to an additional wash with water at 80 C., and then to a drying, whereby 366 g of dry ANPZO are obtained (yield: 47%).

(53) This ANPZO is subject to a series of analyses: SEM, DSC, particle size analyses, measurement of the stability in vacuo at 140 C., measurement of the volatile material rate on dry product, measurement of the residual nitrate content, elemental analyses and thermomechanical tests.

(54) The SEM image showing particles of this ANPZO is illustrated in FIG. 9 while the results of the other analyses are indicated in table 1 hereafter.

Example 7: Comparative Example

(55) In a flask provided with a thermometer and a stirrer, 3.84 L of concentrated sulfuric acid and then 451.9 g of DAPO portionwise are introduced. After dissolution of the DAPO in the sulfuric medium, 678 g of concentrated nitric acid are slowly added while maintaining the flask at a temperature below 35 C. The reaction medium is left under stirring for 2 hours, at room temperature.

(56) This reaction medium is then added portionwise to 13.4 L of water while maintaining the temperature of the flask at 30 C.

(57) A precipitate is formed which is recovered by filtration and which is washed on the filter with water and then with an aqueous solution saturated with NaHCO.sub.3 and then again with water.

(58) The thereby obtained humid ANPZO is subject to an additional wash with water at 80 C. and then to a drying, whereby 401 g of dry ANPZO are obtained (yield: 52%).

(59) This ANPZO is subject to a series of analyses: SEM, DSC, particle size analyses, measurement of the stability in vacuo at 140 C., measurement of the volatile material rate on dry product, measurement of the residual nitrate content, elemental analyses and thermomechanical tests.

(60) The SEM image showing the particles of this batch is illustrated in FIG. 10 while the results of the other analyses are indicated in table 1 hereafter.

(61) TABLE-US-00001 TABLE I Thermomechanical tests Stability Volatile t.sub.decomp. Main in vacuo material Elemental analyses* .sub.decomp. 500 bars mode d0.5 .sub.onset at 140 C. rate Q.sub.NO3 (% m/m) 500 bars 220 C. ANPZO (m) (m) ( C.) (cm.sup.3/g) (%) (%) C H N S ( C.) (min) Example 1: 71 66 350 0.05 0.04 <0.05 22.2 1.8 38.2 0 ND 107 batch 1 Example 1: 71 59 350 0.04 0.01 22.1 1.8 38.0 261 67 batch 2 Example 2 62 56 350 0.07 0.06 22.6 2.0 39.2 246 54 Example 3 62.5 59 349 0.06 0.07 22.5 1.8 39.0 270 50 Example 4 52.5 49 349 0.05 0.04 ND 22.5 1.8 38.7 260 54 Example 5 60 56 347 0.05 0.05 <0.05 22.4 1.7 38.2 265 39 Example 6 39 37 347 0.13 0.13 22.3 1.8 38.5 236 23 Comparative 25 23 350 0.11 0.10 22.4 1.8 38.4 231 17 example *Theory: C = 22.6%; H = 1.9%; N = 38.9% ND = not determined

(62) FIGS. 1 to 10 as well as this table show that the particles of synthesized ANPZO according to the invention have: an aspect ratio of no more than 2 and typically of no more than 1.4; and a median size (d0.5) by volume at least equal to 35 m and which may attain 66 m (cf. example 1, batch 2), while the median size by volume of the synthesized ANPZO particles in the comparative example is only 23 m.

(63) Table 1 also shows that these ANPZOs have: a high degree of purity objectified by their residual nitrate ion content which is less than 0.05%, by the mass percentages obtained for carbon, hydrogen, nitrogen and sulfur by the elemental analyses which are compliant with the theoretical percentages, as well as by the HPLC chromatogram of the ANPZO synthesized in example 3; and a high thermal stability objectified by their initial thermal decomposition temperature which is around 350 C.

(64) Furthermore, it is noted an increase in their decomposition temperature under pressure as well as in the time required for their decomposition under pressure and at 220 C. relatively to those of the ANPZO particles synthesized in the comparative example, which increase is particularly marked when the nitrate salt is a potassium or ammonium nitrate.

QUOTED REFERENCES

(65) [1] T. D. Tran et al., 12.sup.th International Detonation Symposium, Aug. 11-16, 2002, San Diego, USA [2] Patent application US 2009/0299067 [3] International PCT application WO 2010/123806, [4] Zuckerman et al., Intensive Munitions & Energetic Materials Technology Symposium, May 18-21, 2015, Rome, Italy [5] D. am Ende et al., Insensitive Munitions & Energetic Material Technology Symposium, May 18-21, 2015, Rome, Italy [6] D. Lemoine et al., Europyro 1995, Jun. 5-9, 1995, Tours, France [7] P. Reynier, Joint International Symposium on Energetic Materials Technology, Oct. 5-7, 1992, New Orleans, USA