George W. Nauflett Robert E. Farncomb Lalit Chordia NOTICE

Transcription

1 Serial Number Filing Date Inventr 09/ February 98 Gerge W. Nauflett Rbert E. Farncmb Lalit Chrdia NTICE The abve identified patent applicatin is available fr licensing. Requests fr infrmatin shuld be addressed t: FFICE F NAVAL RESEARCH DEPARTMENT F THE NAVY CDE CC ARLINGTN VA IDTIC QUALITY il SSPECTFiD 8

2 f. 1 Navy Case N. 78,7 PATENTS PREPARATIN F MAGNESIUM-FLURPLYMER PYRTECHNIC MATERIAL R Gerge W. Nauflett Rbert E. Farncmb 7 Lalit Chrdia 8 9 by BACKGRUND, Q This inventin relates t energetic materials and mre particularly t methds f -] i prducing energetic materials frm metals and flurplymers. 1 2 Pyrtechnics are mixtures f substances that prduce nise, light, heat, smke, r mtin when ignited. They are used in matches, incendiaries, and ther igniters; in firewrks and flares; in fuses and ther initiatrs fr primary explsives; in delay trains; and fr pwering mechanical devices. Military pyrtechnics include a wide range f devices fr illuminatin, signaling, incineratin, and gas generatin. Military pyrtechnic devices are characterized by mre rugged 1 g cnstructin and greater resistance t adverse envirnmental cnditins with cncmitant higher 1 g cst, reliability, and safety than are civilian pyrtechnics. Magnesium/Tefin/Vitn (MTV) pyrtechnics are used by the Armed Frces t 21 manufacture rcket mtr igniters and flare decys. MTV is currently manufactured using the 22 shck-gel prcess in which: (1) the Vitn binder is disslved in acetne; (2) the magnesium and 2 Tefln particles are added t the Vitn/acetne slutin t frm a slurry; () and hexane is added 24 t the slurry t shck the slurry and precipitate the Vitn ut f slutin nt the surfaces f the 25 magnesium and Tefln particles. The slvent is then decanted frm the mixture and the prcedure is repeated t ensure that all the remaining acetne is washed frm the pyrtechnic

3 J 1 material. Althugh the prcess is extremely effective in cating the magnesium and Tefln, it is a 2 lengthy batch prcess which requires an extremely large quantity f slvent (acetne and hexane) t cat the magnesium and Tefln with the Vitn binder. It takes five 55-galln drums f slvent 4 t prcess 0 punds f MTV. The cllected acetne and hexane mixture must be dispsed f 5 as hazardus waste due t the txic nature f the slvent. 6 7 It wuld be desirable t prvide an methd f prducing high quality energetic materials 8 cmpsed f a mixture f magnesium (r magnesium allys, aluminum, aluminum allys,* etc.) 9 1 particles and plytetraflurethylene (e.g., Tefln) particles in a vinylidene fluride- hexaflurprpylene cplymer (e.g., Vitn A, Flurel) binder withut generating large vlumes f hazardus waste. SUMMARY 1 4 Accrdingly, an bject f this inventin is t prvide a new prcess fr prducing 15 magnesium/flurplymer energetic materials. 16 Anther bject f this inventin is t prvide a prcess fr prducing magnesium/flurplymer energetic materials withut prducing large vlumes f hazardus waste. cmprising: These and ther bjects f this inventin are accmplished by prviding a prcess 22 (1) disslving a vinylidene fluride-hexaflurprpylene cplymer in a ketne slvent 2 that is acetne, methyl ethyl ketne, r mixtures theref; 24 (2) frming a paste by adding a mixture f plyetetraflurethylene particles and reactive 25 metal particles that are magnesium particles, magnesium ally particles, aluminum particles, aluminum ally particles, r mixtures theref t the slutin frm in step (1);.

4 J () adding liquid C2 t the paste frmed in step (2) t cause the vinylidenefiuride- hexaflurprpylene cplymer t precipitate ut f the ketne slvent and cat the plytetraflurethylene particles and the reactive metal particles while the paste is agitated; and (4) separating the vinylidenefluride-hexaflurprpylene cplymer-cated plytetraflurethylene particles and reactive metal particles frm the ketne slvent and the C The ketne slvent and the C2 are preferably separated frm each ther and reused. 9 1 BRIEF DESCRIPTIN F THE DRAWINGS A mre cmplete understanding f the inventin and many f its attendant advantages theref will be readily appreciated as the same becmes better understd by reference t the fllwing detailed descriptin when cnsidered in cnnectin with the accmpanying drawings, wherein: 1 5 FIG. 1 is a flw diagram illustrating the prcess f this inventin; and 16 FIG. 2 is a general schematic drawing f equipment which may be used in the prcess f ' ' 18 this inventin. DESCRIPTIN The prcess f the present inventin prduces energetic materials by cating a mixture f plytetraflurethylene (Tefln) particles and reactive metal particles with a cplymer 22 hexaflurprpylene and vinylidenefluride. The reactive metal particles are preferably 2 magnesium particles, magnesium ally particles, aluminum particles, aluminum ally particles, r 24 mixtures f these particles, with the magnesium particles being the mst preferred. The 9 R vinylidenefluride-hexaflurprpylene cplymers which may be used in this prcess are sluble in acetne r methyl ethyl ketne and insluble in carbn dixide (C2). The

5 J vinylidenefluride-hexafluörprpylene (70:0) cplymer is mst preferred. This cplymer is available under the tradenames VITN and FLUREL. In the preferred embdiment, this prcess is used t prduce MTV (magnesium-tefln-vitn), a pyrtechnic material used t manufacture rcket mtr igniters and flare decys. The weight percentages f the staring materials: reactive metal particles, plytetraethylene particles, and vinlidenefiuride-hexaflurprpylene cplymer are determined by the desired 8 cmpsitin f the energetic material prduct and the use it will be put t. The prcess f the 9 present inventin is a physical cating prcess which will be perable ver a wide range f relative weight percentages f these ingredients. The prcess f the present inventin cats reactive metal particles and plytetraflurethylene (Tefln) particles with a vinylidenefluride-hexaflurprpylene 1 cplymer t prduce an energetic material. A well agitated paste slurry f reactive metal 15 particles and plytetraflurethylene particles in a slutin f the vinylidene fiuride- 16 hexaflurprpylene cplymer in acetne r methyl ethyl ketne is frmed and liquid C2 is 1 ' added t the acetne r methyl ethyl ketne until all the cplymer is precipitated ut as a cating 1 R n the reactive metal particles and the plytetraflurethylene particles. The C2 and the ketne (acetne r methyl-ethyl ketne) are remved frm the prduct cplymer-cated magnesium and plytetraflurethylene particles and the free-flwing prduct is cllected. The acetne r methyl 22 ethyl ketne and C2 are separated and recycled t prepare the next batch. Prduct which des 2 nt meet specificatins is als recycled. This the prcess cnverts the raw materials int the 24 prduct withut prducing significant amunts f waste materials. 25 Fig.l is a flw diagram f the present prcess being used t prepare a MTV (magnesium- Tefln-Vitn) pyrtechnic cmpsite. First acetne and the vinylidene fluride

6 1 1 hexaflurprpylene(70:0) cplymer (Vitn r Flurel) are mixed tgether t prduce a 2 slutin f the cplymer in acetne. The slutin will preferably cmprise frm abut 9 t abut 25 and mre preferably frm 16 t weight percent f the vinylidenefluride- 4 hexaflurprpylene cplymer with the remainder f the slutin being acetne. 5 As shwn in Fig. 1, the next step is t mix magnesium particles and 7 plytetraflurethylene particles with the vinylidene fluride-hexaflurprpylene(70: 0) 8 cplymer /acetne slutin t prduce a slurry. The slurry is a paste having a cnsistency 9 similar t pured cncrete. The amunts f magnesium, plytetraflurethylene, and vinylidene fluride-hexaflurprpylene(70:0) cplymer added are the amunts required t prduce the desired energetic cmpsite. Fr instance, in the examples, 54 weight percent f magnesium particles, 0 weight percent f plytetraflurethylene (Tefln), and 16 weight percent f vinylidenefluride-hexaflurprpylene (70:0) cplymer (Vitn r Flurel) were used t 1 5 prepare a MTV pyrtechnic material. 16 Referring again t the flw chart f Fig. 1, the next step is the shck r super-shck step in '' 18 which the vinylidene fluride-hexaflurprpylene(70:0) cplymer is shcked r driven frm the acetne t precipitate as a cating n the plytetraflurethylene particles and the magnesium particles. It is critical that the slurry is vigrusly agitated (e.g., stirred) during this shck step in rder t prduce a high quality prduct. This shck precipitatin step is run in a pressure vessel 22 in which the utlet valve is clsed and nly the supercritical C0 2 inlet is pen. In the presence f 2 acetne, the critical temperature f C0 2 is raised frm 0.1 C t abut 0 C. As a result, the 24 supercritical C2 is cnverted t liquid C2 in the pressure vessel. Because C2 and acetne are 9 R infinitely sluble in each ther, the C0 2 readily disslves in the acetne t prduce a C0 2 /acetne slutin. The vinylidene fluride-hexaflurprpylene(70:0) cplymer is sluble in acetne

7 1 1 but insluble in C0 2. As a result, the C2 shcks r drives the cplymer ut f the acetne as a 2 precipitate that cats the plytetraflurethylene particles and the magnesium particles. Because, the acetne is recycled in the preferred embdiment f this inventin, it is critical that enugh 4 C0 2 is added t drive all f the vinylidene fluride-hexaflurprpylene(70:0) cplymer frm 5 the acetne. Even a small amunt f the cplymer will accumulate in the system and clg 7 valves and sensrs, making the system dangerus t perate. At 40 weight percent acetne (60 8 weight percent C2) the recvered acetne cntained n vinylidene fluride- 9 hexaflurprpylene(70:0) cplymer (Flurel). Hwever, at 80 weight percent acetne ( weight percent C0 2 ) the recvered acetne cntained 6.4 weight percent Flurel and at 54 weight percent acetne (46 weight percent C0 2 ) the recvered acetne cntained weight percent Flurel. Therefre, C0 2 is preferably added until the acetne/c0 2 slutin cntains at least 60 weight percent f C0 2 and n mre than 40 weight percent acetne. - 5 After all the vinylidene fluride-hexaflurprpylene(70:0) cplymer has been 16 precipitated frm the acetne, the acetne is remved in an extractin step (see Fig. 1). This is '' 1 R dne by pening the utlet valve in the pressure vessel and cntinuing the input f the supercritical C0 2 while the slurry is vigrusly agitated (e.g., stirred). After the acetne/c02 slutin has been flushed ut f the reactr, the critical temperature f the C0 2 drps back dwn t abut 0.1C and the supercritical C0 2 is n lnger liquefied. The input f supercritical C0 2 is 22 cntinued while slid MTV prduct is vigrusly agitated until all the acetne adhering t the 2 MTV particles is remved. After n mre acetne is detected in the supercritical C0 2 exhaust 24 leaving the pressure vessel, the supercritical C0 2 input is stpped and the slid MTV prduct is r cllected. The free-flwing slid MTV crumb prduct may then be extruded using cnventinal means.

8 r In the preferred embdiment as indicated in Fig. 1, the C0 2 and acetne flushed frm the pressure vessel are separated and then recycled. In the examples, a Cyclne separatr is used t separate the acetne as a liquid and the C2 as a gas. In the general prcess f this inventin the carbn dixide (C0 2 ) which is fed int the pressure vessel in the shck step and the extractin step (acetne r methyl ethyl ketne remval) is preferably at a pressure f frm abut 1,000 t abut,000, mre preferably frm 1,000 t 8 5,000, and still mre preferably frm 2,000 t 4,500 psi, and at a temperature r preferably frm 9 abut 15 t abut 80, mre preferably frm 1 t abut 80, and still mre preferably frm 60 t 80 C. The C0 2 will be either in the frm f a liquid r a supercritical fluid. If the C0 2 is bth at a temperature abve its critical temperature (0.1C) and at a pressure abut its critical pressure (44 psi?), the C0 2 feed will be a supercritical fluid. Hwever, in the presence f either acetne 1 r methyl ethyl ketne the critical temperature f C0 2 is raised well abve 80 C and the 1 5 supercritical C0 2 fluid is cnverted int liquid C The C0 2 readily disslves in the acetne r methyl ethyl ketne. The vinylidenefiuride- 17 plyhexaflurprpylene cplymers are sluble in acetne r methyl ethyl ketne but insluble 1 ft in C0 2. Thus, the C0 2 shcks r drives the cplymer frm the ketne slutin and the precipitating cplymer frms a cating n the plytetraflurethylene particles and the reactive metal particles. Because the acetne r methyl ethyl ketne is recycled, it is critical that all 22 vinylidenefluride-hexaflurprpylene cplymer is remved (precipitated) frm the 2 ketne/c0 2 slutin. As a result C0 2 shuld be added until the ketne (acetne, methyl ethyl 24 ketne, r mixtures theref)/c0 2 slutin preferably cntains at least 60, mre preferably at least 25 70, still mre preferably at least 80, and mst preferably at least 90 weight percent f C0 2. The cmpsitin f the ketne/c0 2 slutin is easily calculated frm the weight f ketne (acetne,

9 1 methyl ethyl ketne, r mixtures theref) used and the pressure, temperature, flw rate, and time 4 5 f flw f the C2 feed stream. Fig. 2 shws a schematic drawing f a typical apparatus set up which may be used in the present prcess where the C0 2 and the acetne are recycled. Shwn is a premix vessel in which a MTV premix 22 f magnesium particles and plytetraflurethylene (Tefln) particles -7 in a slutin f vinylidene fluride-hexaflurprpylene(70:0) cplymer in acetne is prepared. 8 The MTV premix 22 is mixed by premix agitatr blades 0 which are attached t premix agitatr 9 shaft which is driven by premix agitatr mtr. After the MTV premix 22 is prepared, the premix valve 4 is pened and the MTV premix 22 is transfer thrugh tube 6 int pressure vessel 54 where the premix is nw referred t as MTV material 62. The MTV material 62 starts ff as the MTV premix; is cnverted by the C0 2 shck prcess step t raw, acetne-cntaining MTV prduct; and is finally cnverted t the dry, acetne-free, free-flwing MTV crumb final 1 5 prduct. The MTV material 62 in pressure vessel 54 is agitated by agitatr blades 64 which are 16 attached t the pressure vessel agitatr shaft 60 which is driven by the pressure vessel agitatr ' ' 1 R mtr 58. C0 2 is fed frm line 8 int a cmpressr 40 where the C0 2 is cmpressed t a pressure f frm 1,000 t 5,000 psi and then flws thrugh a ht water heat exchanger 44 which heats the C0 2 abve the supercritical temperature. (Ht water flws in thrugh inlet 46, thrugh the heat exchanger 44, and then ut thrugh the utlet 48.) The nw supercritical C flws 22 thrugh inlet valve 52 int the reactin vessel 54. Nte that premix valve 4 and pressure 2 reductin valve 76 are clsed thus sealing the pressure vessel 54. The temperature f the pressure 24 vessel 54 is kept at the temperature f the incming supercritical C0 2 by a ht water jacket 66 which surrunds the pressure vessel 54. Ht water flws in thrugh inlet 68, thrugh the jacket 66, and ut thrugh the utlet 70. In the presence f acetne, the critical temperature f C0 2 is

10 1 greatly raised, causing the supercritical C2 t liquefy and be disslved in the acetne in the MTV material 62. After sufficient C2 has be added t shck r precipitate all the vinylidene fluride-hexaflurprpylene cplymer frm the acetne, the pressure reductin valve 76 is pened. Acetne and C2 are exhausted thrugh the exhaust line 72 as the agitatr blades 64 cntinue t mix the MTV material 62 and supercritical C2 50 cntinues t flw in thrugh the inlet valve 52. After the bulk f the liquid acetne has been remved frm the MTV material 62, 8 the critical temperature f C2 is reduced and the supercritical C2 is n lnger liquefied. The 9 agitatin f the nw dry MTV material 62 is cntinued and the flw f supercritical C2 is cntinued until acetne is n lnger detected in the exhaust supercritical C2. The acetne and C2 is remved frm the pressure vessel 54 thrugh the exhaust line 72 which feeds the pressure reductin valve 76. Frm the pressure reductin valve 76 the C2 flws (at reduced pressure) 1 thrugh ttal hydrcarbn detectr 80 (which mnitrs the C2 fr acetne) and n t a Cyclne 15 separatr 82.. The Cyclne separatr 82 separates the acetne as a liquid and the C2 as a gas. 1 6 The liquid acetne is drained frm the separatr 82 thugh a cyclne separatr valve 84 int the 17 recvered acetne line 86. The acetne is recycled fr use in a future batch. The C2 is passes 18 thrugh line 90 t a C2 purifier 92. A line 94 feeds the purified C2 t the cmpressr 40 fr reuse in the prcesses. Additin C2 may be added thrugh line 8 as needed. Finally, after all the acetne has been remved frm the dry MTV material prduct 62, the agitatr (58,60,64) is turned ff and the flw f supercritical C2 thrugh inlet valve 52 is stpped. The dry MTV 2 material prduct 62 is then cllected. 24 The general nature f the inventin having been set frth, the fllwing examples are 25 presented as specific illustratins theref. It will be understd that the inventin is nt limited t

11 1 these specific examples but is susceptible t varius mdificatins that will be recgnized by ne f rdinary skill in the art. Experimental Super-Shck Prcess MTV Prcess MTV paste was prepared in tw steps. First the acetne slutin f flurel-2175 r Vitn- A was prepared by standing vernight in a stainless steel beaker. Secndly, the magnesium (Type II) and Tefln 7C were slurried int the slutin. The paste was added t a 500-mL pressure 8 vessel equipped with a thermcuple, agitatr and tachmeter. An upward flw f carbn 9 dixide at 60 C at 16 atm (2,000 psi) quenched the mixture under agitatin (400 ± 50 RPM). The MTV crumb was cntinuusly extracted with a flw f supercritical C2 until acetne stpped cllecting in traps. Dry free flwing gray MTV was pured ut f the vessel and abut t 15% f MTV stuck t the agitatr and vessel. 1. Shwn in Table 1 is a summary f the MTV batches prepared. The Vitn-A was replaced 15 with Flurel-2175 which has the same CAS number and is used as a direct replacement in MTV 16 prductin.. 17 Efficient agitatin was fund t be essential fr the preparatin f free flwing crumb similar t that prduced by the Shck-Gel prcess. MTV Batches using ne impeller prduced free flwing crumb in 50 gram batches but nt at the 0 gram level. The need fr efficient agitatin was demnstrated when fur impeller blades were used. All the 0 t 0 grams batches f MTV crumb prduced using fur impeller blades were free flwing. 2 A parameter study was perfrmed t determine the effects f acetne cntent n MTV the 24 Super-Shck prcess. The amunt f carbn dixide needed t extract the acetne frm the MTV 25 was als investigated. The cncentratin f acetne at the start f each batch was calculated. At

12 1 40% acetne (60% C2) the recvered acetne cntained n Flurel. At 80% acetne (% Ci) 2 the recvered acetne cntained 6.4% Flurel

13 u -*-» IJL, r-l CN 1 C 1 *fr in V r^ 00 N 1 ^ CN C ^f in a) u 1 H 1 "* 1 H C "1- ^ I N CN <L> A c A A E.S % Flu,_* i ' 1 1 i i 1 i N r- CN N r " ^ N N s- T T 1 V i I i ^ N N N in * c CN "* 00 N N N N 00 N «^ <u a N T c/i a.-* C X u H < CQ CM > H s Ü m H-» X <D C -* CD IN > % u c e I 1 I I r» in CN in in m in -- in C r-h S m >n N r- r < c r- m 00 m «I C CN CN c, 1 V) ja 6^ N * Tt 'tf ^ c xr =* CN N <* >/~i CN CN "- in * S ^-s bfl N >n CN CN r- + in C C <N rt r^ -* i r t CN N N CN. r-h in C 00 m N N (N n N CN 00 C m r^ C V % u <a r > ' > ' C C C CN r i i i 1 H 1 CX CX ex ex a ex CX CX a«a, a, a, ex ex ex ex ex P P P p P p P p P P P P P P P P P Q <L> C 01 2 N N N N N c» I i-- CN,_, 00 0 s C m,, "8»"- 1 CN CN in CN ' CN > i * l ' ^f N N 00 * CN * a p S 4> 5 +i vn " +- C N T-H 1 H i t N ><i- CN I «* r-h CN \ in N N in N * C * C * m m *r in ^r ^r CJ _ m s ~s Batch size (g m m in in m in r- m «n in >n CN CN CN in * <L> ex i ~ (N c "* in N f- 00 N ^ CN C * in N r-~ 00 X w rs m

14 4-* 'S" c 'S < 4 00 C *,s « U ü 2 c et U c 4» C > 1/2 c e E _ " C d P a 4 u C "-4-» J ä -^»-' =ä *- u c c C «i > w 01 u c *-» d> ü <B Jü " u e c <L> 44 <L> c t - -» '5b G "E, e T CD 2 en (L) u Pi -4-> 00 S n 01 >. es es J G < s c " c c«>» u c c c *» u 00 ü P 00 hj cd E C 00 C -Ö U 42b "ös ^ *-g 0) * C, ^ (U cq c c c c

15 bviusly, ther mdificatins and variatins f the present inventin may be pssible in light f the freging teachings. It is therefre t be understd that - the inventin may be practiced therwise than as specifically described.

16 1 Navy Case N. 78,7 2 PREPARATIN F MAGNESIUM-FLURPLYMER PYRTECHNIC MATERIAL ABSTRACT A prcess fr preparing energetic materials by (1) disslving a vinylidenefluride- y hexaflurprpylene cplymer in a ketne that is acetne, methyl ethyl ketne, r mixtures 8 theref, (2) adding plytetraflurethylene particles and reactive metal (magnesium, aluminum, 9 r their allys) particles t frm a slurry, () adding C0 2 t the slurry t precipitate ut the cplymer which then cats the plytetraflurethylene and reactive metal particles, and (4) separating the cplymer-cated particles frm the ketne and C $

17 / ' Acetne FLUREL Mix TEFLN Mg Mix, >C0 2 Recycle C0 2 Shck 'C0 2 Recycle SC-C0 2 > Extract ' Extrude ACETNE Recycle 1 rv Ml Prc luct FIG.1

18 05 TJ