Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B25/00—Compositions containing a nitrated organic compound
  • C06B25/18—Compositions containing a nitrated organic compound the compound being nitrocellulose present as 10% or more by weight of the total composition
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B45/00—Compositions or products which are defined by structure or arrangement of component of product
  • C06B45/04—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive
  • C06B45/06—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive the solid solution or matrix containing an organic component
  • C06B45/10—Compositions or products which are defined by structure or arrangement of component of product comprising solid particles dispersed in solid solution or matrix not used for explosives where the matrix consists essentially of nitrated carbohydrates or a low molecular organic explosive the solid solution or matrix containing an organic component the organic component containing a resin

Definitions

• the present invention relates generally to single base propellants and, more particularly, to the reduction of environmental hazards by the elimination of the need to incorporate dinitrotoluene (DNT) in single base propellants.
• DNT dinitrotoluene
• the invention provides substitute, less energetic but more efficient, plasticizing compounds which enable the incorporation of additional relative amounts of nitrocellulose (NC) in the mix thereby maintaining overall energy levels.
• Single base propellants generally contain colloided nitrocellulose powders as the chief energetic component and this makes up about 85-99% (weight) of the propellant mix.
• the nitrocellulose is combined with a plasticizer to give the mix the desired mechanical properties so that the material can be processed into grains or other shapes utilized in, for example, 155 mm Artillery charges or 120 mm tank ammunition, or for other projectile firing purposes. Varying amounts of other stabilizing additives are added to the mix to reduce hazards sensitivity and to prolong shelf life.
• Double or multi base propellants contain the same colloided nitrocellulose component, but utilize a second, liquid energetic compound such as nitroglycerin (NC) or an equivalent energetic liquid nitrate ester as a plasticizer.
• NC nitroglycerin
• Double base powders typically contain about 80% colloided nitrocellulose with the major portion of the remaining material consisting of the nitroglycerin fraction.
• the powders of the present invention are single base propellants. They must be relatively hazard insensitive and so avoid shock or heat sensitive plasticizers .
• An example of a prior blasting composition using NC and DNT is shown in U.S. Patent No. 3,328,217.
• DNT dinitrotoluene
• Such single base propellants normally contain from about 1-10% DNT which itself is an energetic plasticizer albeit of low hazards sensitivity.
• DNT also reduces the hygroscopic properties of the nitrocellulose making the mixture more water resistant and can be used to adjust the burning rate as it reduces the burning rate of pure nitrocellulose.
• Single base propellants are produced utilizing a solvent-type process.
• a solvent-type process An example of which is found in U.S. Patent No. 4,525,313 to Muller.
• Ingredients are mixed utilizing volatile solvents or gelling agents which, as a rule, are selected from ketones, alcohols, ethers or mixtures thereof.
• volatile solvents or gelling agents which, as a rule, are selected from ketones, alcohols, ethers or mixtures thereof.
• thermoplastic shaping processes including pressing and extruding equipment enable forming to take place at relatively low working temperatures. For example, nitrocellulose that has been turned into a doughy mass can readily be extruded in desired shapes at ⁇ 50°C.
• DNT lends itself readily to such a process inasmuch as that component can be in the form of an oil, solid or an oil- solid mixture which includes all three DNT isomers (i.e., 2 , 4; 2, 5 and 2,6 DNT) and generally freezes in the range from about 20-35°C.
• the solid form is generally para or 2, 4-dinitrotoluene. This material also lends itself readily to solvent processing with the nitrocellulose.
• DNT has had a long and successful use as the major plasticizing and energy adjustment component in single base propellants and, with respect to the properties of the propellants themselves, has been quite successful.
• the DNT is normally utilized with an amount of a second plasticizer, generally dibutylphthalate (DBP) which works well in combination with the DNT.
• DBP dibutylphthalate
• DNT dinitrotoluene
• DNT has many attributes which make it a successful plasticizer and energy adjustment material for single base propellants. While successful from the standpoint of processing and use of the propellant, DNT carries with it significant environmental drawbacks which have more recently provoked increasingly important concerns. Fine particulate DNT is considered quite toxic as when dust is produced in de-milling propellant. Residue DNT has traditionally been burned to destroy the material, but this produces undesirable nitrogen oxides (NO x ) .
• Polycyclic aromatics are also given off by the combustion of DNT and these are considered quite carcinogenic.
• DNT is soluble up to about 150 PPM in water so that this presents a serious potential waste water problem.
• the material has not only been classified as a potential carcinogen, but also has been declared a hazardous waste by the EPA.
• DNT plasticizer without sacrificing performance in the propellant material and which can be processed with existing production equipment for single base propellants.
• dibubylphthalate DBP
• DBP dibubylphthalate
• DBP While not necessarily as undesirable as DNT, DBP is also considered a toxic material. It would also be advantageous to eliminate this material from the compositions as well.
• DPA diphenyl amine
• Another object of the invention is to provide a single base propellant which does not contain DNT but which can be processed using existing single base processing equipment.
• Yet another object of the invention is to provide a single base propellant which does not require DBP in the formula.
• An additional object of this invention is to provide a single base propellant which does not use DPA as the stabilizer.
• a further object of the present invention is to provide non-toxic and environmentally friendly chemical plasticizers for single base propellants that do not require DNT, DBP or DPA.
• a yet still further object of the invention is to provide new plasticizers for single base propellants which are non-toxic and environmentally safe and which can be added to the propellant utilizing the same processing solvents used for other components in existing single base processes.
• the present invention provides viable environmentally friendly substitutes for dinitrotoluene (DNT) in single base munition propellants which are compatible with existing solvent-type single base propellant manufacturing processes and which, in addition, enable propellants compatible in performance to existing DNT-containing loads.
• DNT dinitrotoluene
• certain adipate and citrate compounds can be used in relatively small quantities to sufficiently plasticize high nitrogen (N) (about 13.2% N) nitrocellulose
• NC in single base propellants.
• the required relative quantities are far less than that required using DNT, i.e., about 2-5% versus about 7-10% or more of DNT.
• these compounds are not energetic themselves, and thus, actually have a negative energy output with respect to the propellant compared to the positive energy of DNT, the lesser required amounts allow corresponding increases in the allowable percentage of NC in the propellant mix which offsets the negative energy of the plasticizers of the invention and results in an overall comparable energy yield for the propellant, typically impetus levels of up to 986 J/g.. This is comparable to prior DNT containing loads such as M14 utilized for 120 mm tank cartridges.
• the preferred compounds in accordance with the invention include certain adipate and/or citrate compounds including diisobutyl adipate (DIBA) , diisooctly adipate
• DIBA diisobutyl adipate
• DIBA diisooctly adipate
• Exemplary propellant compositions include from about 94-96% high N nitrocellulose (about 13.2% N) , about 2-4% plasticizer and the remainder dibutylphthalate (DBP) .
• the DBP provides additional plasticizing qualities.
• a small amount, nominally 1%, diphenylamine (DPA) is added to the mix as a thermal stabilizing material. Additional embodiments include up to about 10% or more
• compositions contain a lesser amount of high N nitrocellulose (about 88-90%) . These formulations may also contain ethyl cellulose as the stabilizer in place of the DPA. These compositions containing approximately 10% of the new plasticizer system result in lower energy levels that are comparable to currently produced Artillery propellants such as Ml, or approximately 930 J/g impetus.
• the propellant combination of the invention containing the environmentally friendly plasticizing materials can be processed using conventional single base solvent processing techniques including conventional solvents, presses, extrusion and cutting devices and solvent recovery techniques.
• Figure 1 shows the accelerated aging properties of certain new compositions according to the invention relative to Ml ; and Figure 2 depicts ballistic test results using a Gamma Dynagun for a composition of the invention with Ml energetics.
• plasticizing compounds which enable substitution for DNT without sacrificing overall propellant performance.
• NC N nitrocellulose
• DNT has a long history of successful prior usage and its ability to plasticize NC and create processible physical characteristics in the mix. DNT, of course, is moderately energetic and the presence of larger percentages of it does not reduce the overall energy output of the propellant material. Thus, it was quite unexpected that DNT could be replaced using a low or negative energy material without sacrificing the overall performance of the mix.
• DIBA diisobutyl adipate
• ATC acetyltriethyl citrate
• Citroflex A-4 acetyltri-n-butyl citrate
• Other citrates including triethyl citrate, available as Citroflex 2, and tributyl citrate, available as Citroflex 4, both from Morflex, Inc., of Greensboro, North Carolina, were also usable.
• DNT-free single base propellants containing from 2-10% by weight of these new plasticizers display the desirable ballistic, mechanical, thermochemical and stability properties of standard DNT-containing propellant formulations.
• An important property of these plasticizers is that they can be added to the propellant in a standard pre-mixed form with the processing solvents typically used in single base processes.
• the plasticizers are relatively non-toxic and are environmentally acceptable under current governmental regulations.
• the processing solvents for processing single base propellants include conventional solvents for NC which vary depending on the N content of the nitrocellulose.
• high grade nitrocellulose which has above about 13.15% N is practically insoluble in ether, but is readily dispersed by plasticizers and acetone. Below about 13.15% N, either can be used. In some cases, combinations of acetone or ether and other solvents such as alcohols or other ketones are preferred.
• the mixed propellant is dried by removal and recovery of some of the solvent from the mixed batch until a desired level of plasticity is achieved. Adjustment procedure steps, including drying and adding solvent, may continue until the correct plasticity is achieved and thereafter the mixer is run for a short time to allow the solvent to equalize throughout the mix.
• the material is transferred to a blocking press where it is subjected to a high pressure hydraulic ram to pressurize the material to remove occluded air, improve consolidation and form the blocks into the proper shape for the graining press.
• the blocked material is then transferred to the graining press.
• various techniques are utilized to extrude strands of propellant depending on the desired final configuration or use.
• the strands of propellant are cut to a specified length for further drying prior to final cutting into actual grain length.
• the extruded material is dried in a manner which saves and recovers as much solvent as is practical for reuse and so the first step is normally to process the load in a solvent recovery tank.
• the material is then subjected to a water-dry operation where additional solvents are extracted into the water and thereafter to an air-dry cycle where the surface moisture is removed.
• Processing of the new compositions may also be accomplished in new continuos processes where the batch operations are replaced by continuous mixers, extruders and solvent removal.
• Table 1 shows a prior formulation utilizing dinitrotoluene (DNT) as the principle plasticizer and energy adjustment compound.
• DNT dinitrotoluene
• the composition is an example of a mix generally known as M14 and nominally contains about 8% DNT. Note that the specific example contained 8.29% DNT and 2% DBP.
• Table 2A shows three examples (Example 1, Example 2 and Example 3) of percentage compositions formulated in accordance with the present invention in which lesser amounts of the material known as plasticizer "340" has been substituted for the DNT fraction and the percentage of NC increased.
• the material known as plasticizer "340” is diisobutyl adipate or (DIBA) available as Plastall DIBA from the C.P. Hall Company. TABLE 2A
• Table 2B depicts an additional example, Example 4, in which the DNT fraction is replaced by a lesser amount of a material known as plasticizer "319", which is acetyltriethyl citrate, purchased as Citroflex A-2 from Morflex, Inc.
• Figure 1 shows the accelerated aging properties of the new composition (s) relative to M14 at 150° F. Results of the long term aging show that these formulations age at a comparable rate to the standard Ml4 propellant.
• FIG 2A shows ballistic test results from the Gamma Dynagun for the new composition with M14 energetics.
• the Gamma Dynagun is an interior ballistics test device based on a 105 Howitzer that allows assessment of required charge weights to obtain comparable muzzle velocities and pressures to a standard propellant lot. It can be seen from Figure 2 that the charge weight of the new composition is within the same statistical population as the standard M14 propellant lot and a number of production lots of M14.
• the use of other materials, particularly citrate and adipate compounds, is also promising. Note that the formulation requires less plasticizer than those utilizing DNT allowing these negative energy materials to be compensated by the addition of more NC in the formula.
• Example 5 depicts in Table 5 another single base propellant that does not contain either Dinitrotoluene (DNT) or Dibutyl-phthlate (DBP) .
• DNT and DBP as indicated are the two ingredients currently used in the Ml propellant that are considered as carcinogens and toxic materials.
• Table 5 shows a comparison of the formulas of Example 5 (PAP 7993) and a batch of Ml material.
• a non-toxic, citrate type plasticizer Acetyl-triethyl-citrate (ATEC) was selected as replacement for DNT and DBP.
• the first pilot propellant sample (Example 5) was manufactured at a pilot plant using a conventional ether/alcohol solvent system. The samples were characterized for their stability, density, and burning rate characteristics.
• the Ml modified formulation PAP 7993 had similar burning characteristics to the as Ml propellant and its energy content was also comparable with relative force of 97% of the Ml reference lot RAD92C071664. It is believed that the slightly lower energy content of the composition of Example 5 (DNT, DBP, DPA free) can be compensated by increasing the charge weight in the case to give equivalent performance compared to Ml propellant.
• Table 6 shows the ballistic firing results of the new formulation PAP 7993 in the XM231 charge configuration for the 155 mm Howitzer. These data show that the new formulation meets all of the requirements for the XM231 charge.

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• 1999
  • 1999-04-14 CA CA002326133A patent/CA2326133A1/en not_active Abandoned
  • 1999-04-14 WO PCT/US1999/007737 patent/WO1999059939A2/en not_active Application Discontinuation
  • 1999-04-14 EP EP99944981A patent/EP1077910A2/de not_active Withdrawn
  • 1999-04-14 AU AU57691/99A patent/AU756188B2/en not_active Ceased

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