Patent Publication Number: US-5256220-A

Title: Liquid monopropellants

Description:
BACKGROUND OF THE INVENTION 
     It is well known and conventional to use Otto fuels and other liquid fuels to propel torpedoes and other solid projectiles. 
     It is likewise common in the liquid propellant art to utilize liquid propellants for guns as well as for rocket fuel. 
     There are a number of typical problems with these prior art fuels and liquid propellants including low impetus, high flame temperatures and poor gas production per unit mass of fuel. 
     Other liquid fuels and propellants are very sensitive to shock and present safety problems. Most safety problems with liquid propellants are caused by the sensitivity to temperature and pressure of the material involved. 
     It is further well known in the art that some liquid propellants are extremely sensitive to shock. In addition many conventional explosives and propellants lack sufficient thermal stability for use in high temperature environments. 
     Conventional liquid propellants are less stable and more sensitive to shock than the formulations made according to the instant invention. 
     In the Otto Fuel and Otto Fuel II formulations that are presently used by the navy as torpedo propellants there are drawbacks, primarily because these fuels are extremely corrosive and present health hazards if leakage is allowed to occur. The fumes from Otto Fuel II are extremely toxic to personnel in the area. 
     Accordingly, it is one object of the invention to formulate liquid propellants, that can be easily formulated and manufactured in commercial quantities. 
     It is also a primary object to provide Otto Fuel II formulations that combine better performance characteristics with lower toxicity. 
     It is another object of the present invention to formulate novel mixtures and compositions of liquid propellants that have improved physical and chemical properties. 
     It is a further object of this invention to incorporate and utilize several high energy ingredients in a number of conventional liquid fuels and propellants, to improve the energetic characteristics of the liquid propellants. 
     It is another object of this invention to formulate liquid propellants that have superior thermodynamic properties and characteristics that give new and unexpected results. 
     It is a further object to formulate novel propellants and other similar materials including liquid propellants so as to yield improved safety characteristics. 
     It is still a further object of this invention to formulate novel mixtures of liquid propellants with better DTA curves, improved test data and oven times and better auto-ignition times when compared with conventional propellant materials. 
     It is a still further object of this invention to formulate torpedo propellants by increasing energetic properties while decreasing toxicity. 
     It is another object of this invention to prepare formulations that are less hazardous to personnel who are in close proximity to said Otto Fuel formulations. 
     It is a still further object of this invention to formulate liquid fuels and propellants that have greatly superior cavity drop test results. 
     It is another object of this invention to prepare and use formulations of liquid propellants that have greatly lessened sensitivity to shock. 
     It is another object of this invention to produce formulations of liquid propellants that have greatly increased impetus (foot, pounds per pound) while being combined with a lower flame temperature). 
     SUMMARY OF THE INVENTION 
     The invention comprises the product of formulation of a high energy ingredient mixed together with conventional liquid fuels and propellants. The formulated product yields new and unexpected results. The high energy ingredient is a compound usually selected from the group consisting of bis(2-fluoro-2,2-dinitroethyl)amine, bis(2-fluoro-2,2-dinitroethyl)formal, and bis(2,2,2-trinitroethyl)formal. Equivalent compounds selected from Table 1 may be substituted for these components, although the results may not be the same as with each compound but will prove satisfactory. 
     In most cases the high energy ingredient is present in an amount varying between 5% and 75% of the total mixture. 
     In general, the use of a compound selected from the group consisting of bis(2-fluoro-2,2-dinitroethyl)amine, bis(2-fluoro-2,2-dinitroethyl)formal, and bis(2,2,2-trinitroethyl)formal, when mixed with well-known liquid fuels and propellants, will yield a formulated product that will have physical and chemical properties that are superior to either the high energy ingredient or the conventional fuels and propellants. 
     PREFERRED EMBODIMENT 
     There are several preferred embodiments of the invention. The operative compounds are set forth and disclosed in Table I together with some energy factors. 
     In one preferred embodiment, Otto Fuel, a well known liquid propellant used by the U. S. Navy for torpedo propulsion can be formulated with one or more compounds selected from the group consisting of bis(2-fluoro-2,2-dinitroethyl)amine, bis(2,-fluoro-2,2-dinitroethyl)formal and bis(2,2,2-trinitroethyl)formal. 
     
                       TABLE I
______________________________________
Illustrations of the High Energy Ingredient that may be
used in the Preferred Embodiment Formulations
                             H.sub.f.sup.o 298.15° K.
Abbrev. Name                 K cal/mole
______________________________________
FEFO    Bis(2-fluoro-2,2-dinitroethyl)formal
                             -179.8
BFDNA   Bis(2-fluoro-2,2-dinitroethyl)amine
                             -126.95
TEFO    Bis(2,2,2-trinitroethyl)formal
                             -96.40
______________________________________
 
    
     The resulting product of the formulation has much higher impetus than Otto Fuel II alone while increasing burning rates and combustion properties. In each instance where the high energy ingredient is used in the range of from 5 to 75% by weight of the mixture, toxicity of Otto Fuel II is decreased significantly. 
     The experimental data illustrating the results of the combination of bis(2,2,-trinitroethyl)formal, hereinafter referred to as TEFO is set forth in Tables II, III, IV, V, VI, VII and VIII. In another preferred embodiment, diethyl oxalate is formulated with a compound selected from the group consisting of bis(2-fluoro-2,2-dinitroethyl)amine, bis(2-fluoro-2,2-dinitroethyl)formal and bis(2,2,2-trinitroethyl)formal. This experimental data best illustrates the combination of mixing TEFO with diethyl oxalate and is set forth in Tables V, VI, and VII. 
     In another preferred embodiment a compound selected from the group consisting of bis(2-fluoro-2,2-dinitroethyl)amine, bis(2-fluoro-2,2-dinitroethyl)formal and bis(2,2,2-trinitroethyl)formal is mixed with acetone and methylethyl ketone. The experimental data illustrating the results of the combination of TEFO, acetone and methylethyl ketone is set forth in Table VIII. 
     High Energy Ingredients Formulated With Otto Fuel II 
     Otto Fuel II is a liquid fuel that is now used extensively by the U.S. Navy to propel torpedoes. 
     Surprisingly, it has been found that formulation of one or more of the high energy ingredients selected from Table I when mixed with Otto Fuel II will yield high energy propellants having new and unexpected properties. 
     Preparation and Testing of Otto Fuel II 
     Otto Fuel II is comprised of 2-nitrodiphenylamine prepared in accordance with MIL-N-3399; di-n-butyl sebacate; prepared to conform with DOD-B-82669; and propylene glycol dinitrate that is prepared to conform with the requirements of DOD-P-82671. 
     The chemical composition of Otto Fuel II is: A mixture of propylene glycol dinitrate, 2-nitrodiphenylamine, di-n-butyl sebacate. 
     
         ______________________________________
CHEMICAL COMPOSITION OF OTTO FUEL II
               Minimum    Maximum   Test
Component      (% by wt)  (% by wt) method
______________________________________
Propylene glycol dinitrate
               75.8       76.2      4.5.2.1
2-Nitrodiphenylamine
                1.4        1.6      4.5.2.2
Di-n-butyl sebacate
               22.2       22.8      4.5.2.3
Sodium         --          0.8      4.5.2.5
______________________________________
 
    
     The detailed method of testing the propylene glycol dinitrate for content and quality is set forth in Metail in MIL-O-82652(OS), pages 4 and 5. 
     The detailed method of testing the #2nitrodiphenylamine for content and quality is set forth in detail in MIL-O-82652(OS), pages 5, 6 and 7. 
     The detailed method of testing the di-n-butyl sebacate content and quality is set forth in MIL-0-82672(OS), pages 7 and 8. 
     The detailed method of testing the sodium content and quality set forth in OD 43852 and on page 8 of MIL-O-82672(OS). 
    
    
     EXAMPLE 1 
     TEFO is prepared by first producing trinitroethanol. In a second step trinitroethanol is reacted with paraformaldehyde and the crude product is purified. 
     Typical Laboratory Preparation 
     1. Preparation of trinitroethanol (TNEOH): 
     The following ingredients were placed in a three-neck 250 ml flask equipped with a stirrer, thermometer, dropping funnel, and a bath for heating or cooling: 
     
         ______________________________________
Aqueous nitroform (33.27% nitroform) =
                      135.7  grams   (0.30
                                     moles)
Carbon tetrachloride =
                      63.4   grams
methylene chloride =  53.4   grams
paraformaldehyde =    10.4   grams   (0.33
                                     moles)
______________________________________
 
    
     Sulfuric acid (51.5 g of 37.5% acid) was slowly added from the dropping funnel into the stirring mixture while maintaining temperature of 35° C. After a one hour reaction time, the mixture was separated into two layers, aqueous and organic, using a separatory funnel. Then the aqueous layer was extracted four times with methylene chloride (40.1 g portions) and discarded. The organic layer, containing most of the TNEO was combined with the extracts and the resulting mixture dried by azeotropic distillation. During this drying, the temperature of the solution was not allowed to exceed 50° C. A small portion of the dried TNEOH solution was used to determine the reaction yield. Vacuum removal of the diluent from the sample (14.6 g) at room temperature left 3.7g of the TNEOH (a white solid with melting point range of 58°-62° C). The TNEOH was formed in a 90% yield. 
     2. Preparation of TEFO: 
     Paraformaldehyde (3.9 g) was dissolved in reagent grade concentrated sulfuric acid (110.4 g of 96.5% H 2  SO 4 ) and then slowly dripped into the well stirred TNEOH solution (44.9 g of TNEOH) prepared in the first step, above. The temperature was maintained at 20° to 25° C. and the stirring continued for one hour. After this time interval, the sulfuric acid layer and the organic layer were separated with the aid of a separatory funnel. The acid layer was extracted once with methylene chloride (66.5 g) and then discarded. Next the extract was combined with the organic layer. This combined solution was washed twice, four times, and three times with 50 ml each of, respectively, water, 3% aqueous sodium bicarbonate and water. After removal of the diluents by using a rotary evaporator and vacuum, an off-white solid remained. This solid, having a melting point range of 59°-61° C., was obtained in a 78% yield. 
     The crude product was purified by employing a precipitation technique. It was dissolved in ethanol (100 ml) and then precipitated by adding water (100 ml). Filtration and vacuum drying resulted in a 60% total yield of a white solid, which melted at 64° C. 
     The TEFO produced was mixed with conventional Otto Fuel II at room temperature, in the proportions by weight shown in Table II. 
     The The results shown in this table indicate the melting points of the TEFO - Otto Fuel II formulations. 
     The results in Table III indicate the heats of explosion of four (4) different formulations of TEFO and Otto Fuel II. 
     In the second section of Table III cavity drop tests results are indicated for four (4) different formulations of Otto Fuel II and TEFO. 
     The results in Table IV indicate the quality of gas (Moles/100 grs), Impetus (ft-lb/lb) and ISp (lb sec/lb) for 16 different formulations of TEFO and Otto Fuel II. 
     EXAMPLE 2 
     TEFO as prepared in Example 1 is mixed with conventional diethyl oxalate at room temperature. The results shown in Table V illustrate eight (8) different formulations of diethyl oxalate and TEFO. 
     The gas generated (moles/100 grams); impetus (ft-lb/lb) and Isp (lb-sec/lb) disclosed in Table V clearly indicate new and unexpected results in chemical and physical properties flowing from the formulation of Otto Fuel II with TEFO. 
     EXAMPLE 3 
     TEFO is mixed with a number of conventional solvents including diethyl oxalate, methyethyl ketone and acetone. The results, based upon eight (8) different formulations is set forth in Table VI. The results in Table VII indicate the thermodynamic and test data on TEFO, diethyl oxalate, methyl ethyl ketone and acetone. 
     EXAMPLE 4 
     TEFO, acetone, methylethyl ketone were mixed and tested. The experimental data is set forth in Table VIII. 
     The examples are only intended to be illustrative, since obvious modifications and equivalents in the invention will be evident to those skilled in the chemical arts, and propose to be bound solely by the appended claims. 
     
                       TABLE II
______________________________________
Heats of Explosion, cavity drop Test,
Density, and Melting Point-Data
______________________________________
          Density (grs/cc)
TEFO        1.70
BFDNA       1.72
______________________________________
Ingredients
TEFO       Otto-2 Fuel
                     Melting Points (°C.)
______________________________________
--         100       -36.5
10         90        -39.5
15         85        -40.5
20         80        -42.0
25         75        -43.5
30         70        -45.0
35         65        -46.5
40         60        -47.0
______________________________________
 
    
     
                       TABLE III
______________________________________
Percent                    Heats of Explosion
Otto-2 Fuel
          TEFO        NOS 365  E.sub.c (cal/gram)
______________________________________
100       --          --       -732.8
60        40          --       942.6
50        50          --       -1083.5
40        60          --       -1204.7
--        --          100      893.2
______________________________________
                         Cavity Drop Test
Percent                  cm
Otto-II Fuel
          TEFO    NO SET**   (2 kilogram weight used)
______________________________________
100       --      --         18
40        60      --         10.4
50        50      --         3.4
--        --      100        6 to 7
______________________________________
NO SET (TEGDN = 96, Dibutylsebacate = 3% Ethyl (entralite = 1%)
       Density
BFDNA  1.72
TEFO   1.70
DITEFO 1.83
 
    
     
                                           TABLE IV
__________________________________________________________________________
TEFO, Otto-2 Fuel Formulations
__________________________________________________________________________
Ingredient
TEFO       --  5   10  15  20  25  30  35  40
Otto-II Fuel
           100 95  90  85  80  75  70  65  60
Const. Vol. T. (°K.)
           2194
               2251
                   2314
                       2383
                           2463
                               2556
                                   2671
                                       2813
                                           2979
Const. Press. T. (°K.)*
           1390
               1434
                   1503
                       1615
                           1753
                               1901
                                   2052
                                       2234
                                           2363
Gas (moles/100 g)
           5.417
               5.401
                   5.358
                       5.387
                           5.191
                               5.075
                                   4.946
                                       4.811
                                           4.671
(ft-lb/lb) 330755
               338408
                   345008
                       350703
                           355732
                               360995
                                   367656
                                       376618
                                           38740
ISP (lb-sec/lb)
           205.3
               206.9
                   208.8
                       211.3
                           214.5
                               218.3
                                   222.7
                                       227.6
                                           232.7
__________________________________________________________________________
TEFO           45   50   55    60  65  70  75
Otto-2 Fuel    55   50   45    40  35  30  25
Const. Vol. T. (°K.)
               3160 3347 3539  --  3120
                                       3229
                                           3307
Const. Press. T. (°K.)*
               2522 2681 2838  2987
                                   --  --  --
Gas (moles/100 g)
               4.533
                    4.394
                         4.258     3.994
                                       3.876
                                           3.769
(ft-lb/lb)     3989599
                    409314
                         419327
ISP (lb-sec/lb)
               237.7
                    242.5
                         247.0 251.2
                                   255 258.4
                                           261.1
__________________________________________________________________________
 *Constant pressure at 1000 psi
 
    
     
                                           TABLE V
__________________________________________________________________________
Diethyl Oxalate and TEFO Formulations
__________________________________________________________________________
Ingredient
Diethyl Oxalate
               10    30    50    70   90
TEFO           90    70    50    30   10
Const. Vol. T. (°K.)*
               4394  2866  1994  1664 1314
Const. Pre. T. (°K.)**
               3326  2291  1283  1161 1010
Gas (moles/100 grs)
               3.561 4.317 4.746 4.132
                                      3.534
IMPETUS (ft-lb/lb)
               446467
                     344124
                           268111
                                 198720
                                      126135
Isp (lb-sec/lb)
               259.1 221.3 186.8 167.7
                                      144.6
__________________________________________________________________________
metyl ethyl Ketare
           10  20  30  35  40  50  70  90
TEFO       90  80  70  65  60  50  30  10
Const. Vol. T. (°K.)*
           4154
               3032
                   2335
                       2166
                           2057
                               1867
                                   1527
                                       1145
Const. Pre. T. (°K.)**
           3249
               2407
                   1527
                       1380
                           1334
                               1258
                                   1119
                                       930
Gas (moles/100 grs)
           3.829
               4.573
                   5.333
                       5.300
                           5.174
                               4.902
                                   4.326
                                       3.785
IMPETUS (ft-lb/lb)
           445821
               385580
                   339034
                       316927
                           296880
                               254507
                                   176527
                                       114973
Isp (lb-sec/.lb)
           258.0
               232.2
                   207.3
                       202.0
                           197.5
                               188.5
                                   168.4
                                       143.3
__________________________________________________________________________
 *Chamber pressure at 50000 psi
 **Chamber pressure at 1000 psi
 
    
     
                                           TABLE VI
__________________________________________________________________________
Diethyl Oxalate and TEFO Formulations
__________________________________________________________________________
Ingredient
Diethyl Oxalate
           32  33  34  35  36  37  38  39  40
TEFO       68  67  66  65  64  63  62  61  60
Const. Vol. T. (°K.)
           2697
               2641
                   2574
                       2513
                           2457
                               2406
                                   2360
                                       2318
                                           2278
Const. Press. T. (°K.)
           2151
               2081
                   2012
                       1943
                           1875
                               1807
                                   1740
                                       1673
                                           1608
Gas (moles/100 g)
           4.408
               4.454
                   4.499
                       4.545
                           4.591
                               4.636
                                   4.682
                                       4.726
                                           4.770
IMPETUS (ft-lb.lb)
           330923
               326820
                   321659
                       316988
                           312814
                               309073
                                   305665
                                       299421
Isp (lb-sec/lb)
           216.2
               213.7
                   211.2
                       208.9
                           206.6
                               204.4
                                   202.4
                                       200.4
                                           198.6
__________________________________________________________________________
 
    
     
                                           TABLE VII
__________________________________________________________________________
 Thermodynamic and Test Data on Fuels of This Invention
__________________________________________________________________________
TEFO (% wt)    67  64  70  65  65 65  70  65
Diethyl Oxalate (% wt)
               33  36  --  --  17.5
                                  25  --  20
Methyl Ethylketone (% wt)
               --  --  30  35  17.5
                                  10  --  15
Acetone (% wt) --  --  --  --  -- --  30  --
Const. Vol. T. (°K.)
               2641
                   2457
                       2335
                           2166
                               -- 2353
                                      2393
                                          2304
Const. Press. T. (°K.)
               2081
                   1875
                       1527
                           1380
                               -- 1677
                                      1661
                                          1558
Gas (moles/100 g)
               4.545
                   4.591
                       5.333
                           5.300
                               -- 4.850
                                      5.150
                                          4.980
Impetus (ft-lb.lb)
               326820
                   312814
                       339034
                           316929
                               -- 318185
                                      338127
                                          319518
Isp (lb-sec/lb)
               216.2
                   206.6
                       207.3
                           202.0
                               -- 204.1
                                      208.6
                                          202.7
H.O.E. (cal/g) -845
                   -803
                       -816
                           --  -- --  -848
                                          -760
Cavity drop test (cm)
               10.5
                   10.5
                       49  --  -- --  50  49
(2 kg wt.)
Density (g/cc) (25° C.)
               1.308
                   1.368
                       1.247
                           --  -- --  1.257
                                          1.301
Exotherm T. (° C.)
               180 180 203 --  -- --  209 203
TEFO ppt. (°C.)
               --* --  -30 -25 -45
                                  --* --* --*
__________________________________________________________________________
 
    
     
                       TABLE VIII
______________________________________
Acetone, Methylethyl ketone and TEFO Formulations
______________________________________
Ingredient
Acetone      10      30      50    70    90
TEFO         90      70      50    30    10
Const. Vol. T. (°K.)*
             4215    2393    1882  1543  1161
Const. Pre. T. (°K.)**
             3275    1661    1258  1122  936
Gas (moles/100 g)
             3.768   5.150   4.886 4.306 3.762
Impetus (ft-lb/lb)
             446399  338127  259341
                                   180262
                                         116279
Isp (lb-sec/lb)
             258.1   208.6   188.1 168.2 143.1
______________________________________
Diethyl Oxalate  30        25       20
TEFO             65        65       65
Const. Vol. T. (°K.)
                 2424      2358     2304
Const. Press. T. (°K.)
                 1807      1677     1558
Gas (moles/100 grs)
                 4.698     4.850    4.980
Impetus (ft-lb/lb)
                 316916    318185   319518
Isp (lb-sec/.lb) 206.2     204.1    202.7
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