Classifications

• • 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
  • C06B45/02—Compositions or products which are defined by structure or arrangement of component of product comprising particles of diverse size or shape
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B21/00—Apparatus or methods for working-up explosives, e.g. forming, cutting, drying
  • C06B21/0033—Shaping the mixture
  • C06B21/0041—Shaping the mixture by compression
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B21/00—Apparatus or methods for working-up explosives, e.g. forming, cutting, drying
  • C06B21/0083—Treatment of solid structures, e.g. for coating or impregnating with a modifier
• • 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
  • C06B45/18—Compositions or products which are defined by structure or arrangement of component of product comprising a coated component

Definitions

• the present invention relates to the field of propellant charges for small and medium caliber tube weapons. More specifically, the invention relates to a process for the manufacture of temperature-resistant fragmentable propellant charges as well as the powders and charges obtained by this method.
• a fragmentable charge is obtained by compression of grains of propellant powder.
• This compression is generally carried out on grains of powder impregnated with a nitrocellulose plasticizer or with a crosslinkable binder as described for example in US patents 3,655,836 or FR 2,374,278.
• thermoplastic binder A particularly interesting energetic thermoplastic binder is found to be polyvinyl nitrate.
• a first possibility described for example in French patent 2 411 817, consists in carrying out the hot compression of a mixture of grains of powder and grains of binder composition based on polyvinyl nitrate.
• a second possibility described for example in French patent 2,436,766, consists in carrying out the hot compression of grains of powder coated with a film based on polyvinyl nitrate.
• the powder grains are coated by a coating operation during which a powder solution of polyvinyl nitrate in a volatile solvent is sprayed onto the powder grains.
• Fragmentable charges obtained from propellant powder compressed in the presence of polyvinyl nitrate are effectively energetic and fragment very well at the time of firing but they have a limit of use linked to the poor temperature resistance of polyvinyl nitrate which softens from 70 ° C.
• many current munitions have specifications for use which require good mechanical strength at least up to 100 ° C.
• the object of the invention is precisely to propose such fragmentable propellant charges as well as a process for manufacturing these charges.
• the invention therefore relates to a method for manufacturing fragmentable propellant charges for ammunition without a cartridge from propellant powder in grains, characterized in that in a first step, said grains of powder first undergo a coating operation during which a mixture containing at least one dinitropolystyrene, a stabilizer and a derivative of polvinyl alcohol chosen from the group consisting of polyvinyl nitrate and polyvinyl acetate is sprayed onto the powder grains, said mixture being in solution in a medium solvent, and in that, after evaporation of said solvent medium, in a second step, the powder grains thus obtained are compressed at a temperature between 100 ° C. and 140 ° C.
• the weight ratio between the dinitropolystyrene and the dinitropolystyrene unit-derivative of polyvinyl alcohol is between 25% and 75%.
• part of the derivative of polyvinyl alcohol is replaced by cellulose acetate.
• said solvent medium comprises at least one solvent for dinitropolystyrene chosen from the group consisting of cyclohexanone, tetraalkylureas such as tetramethylurea, nitrobenzene, butyrolactone and tetramethylene sulfone.
• the invention also relates to the fragmentable propellant charges for ammunition without a cartridge obtained by the method according to the invention.
• the invention relates in particular to the loadings in which the propellant powder in grains is a single nitrocellulose base powder.
• the invention also relates to the propellant powder grains obtained at the end of the first step of the process according to the invention which are characterized in that said grains are coated with a film of a mixture containing at least one dinitropolystyrene, a stabilizer and a polyvinyl alcohol derivative chosen from the group consisting of polyvinyl nitrate and acetate polyvinyl.
• the method according to the invention therefore consists in a first step of coating grains of propellant powder with a film of energetic thermoplastic material and in a second step of hot pressing the grains of powder thus coated.
• propellant powder it is possible to use in the context of the present invention most of the propellant powders known to those skilled in the art. It is thus possible in particular to use powders with a simple nitrocellulose base or so-called “composite" powders constituted mainly by a nitramine such as hexogen or octogen and by an organic binder such as a polyurethane, a polyester, an acetobutyrate. cellulose alone or in admixture with nitrocellulose and triethyl citrate acetate.
• composite powders constituted mainly by a nitramine such as hexogen or octogen and by an organic binder such as a polyurethane, a polyester, an acetobutyrate. cellulose alone or in admixture with nitrocellulose and triethyl citrate acetate.
• powders containing nitroglycerin or more generally a nitrated oil such as so-called “double base” powders constituted by a mixture of nitrocellulose and nitroglycerine or so-called “multibase” powders constituted by nitrocellulose, nitroglycerin and one or more nitro-energetic compounds such as nitroguanidine, hexogen, octogen, pentrite, dinitroglycolurile, etc.
• the applicant advises against the use of powders with a high level of nitroglycerin to avoid the risks of migration over time of nitroglycerin in the coating film of the powder grains, phenomenon which is likely to disturb the fragmentation of the load at the time of firing.
• the Applicant recommends not using powders with a nitroglycerin or nitrated oil content greater than 25% by weight.
• the geometry of the powder grain will depend on the dimensions and properties desired for the fragmentable load.
• the powder grains, smoothed or unsmoothed, are therefore coated with a film of an energetic thermoplastic material.
• this material is typically constituted by the mixture of at least one dinitropolystyrene, a stabilizer, and a derivative of polyvinyl alcohol chosen from the group consisting of polyvinyl nitrate and l polyvinyl acetate.
• the weight ratio between the dinitropolystyrene and the assembly constituted by the dinitropolystyrene and the derivative (s) of polyvinyl alcohol must be between 25% and 75%.
• Dinitropolystyrene is an organic polymer of formula in which the symbols C, H, O, N represent carbon, hydrogen, oxygen and nitrogen respectively and n represents an integer.
• dinitropolystyrenes of different molecular weights can be used, but those whose softening temperature is higher than 260 ° C. are preferred.
• Dinitropolystyrene is advantageously obtained by nitration of polystyrene according to the techniques described, for example, in the following works: Mémorial des Poudres, volume 35, 1953, pages 41 to 50 (Boniau, Pujo, Lang), Encyclopedia of Explosives and Relative Items, volume 8, 1978, pages 143-144, or even in US patent 3,715,323.
• the preferred stabilizer is 2-nitro-diphenylamine.
• This stabilizer will be present in the mixture at a rate of approximately 2% by weight of the total weight of the dinitropolystyrene and derivatives of polyvinyl alcohol.
• the mixture coating the powder grains therefore contains at least one derivative of polyvinyl alcohol chosen from the group consisting of polyvinyl nitrate and polyvinyl acetate. It can simultaneously contain these two derivatives.
• part of the derivatives of polyvinyl alcohol can be replaced by cellulose acetate, but this is an important condition for implementing the invention, cellulose acetate cannot completely replace derivatives of polyvinyl alcohol.
• the derivatives of polyvinyl alcohol, polyvinyl nitrate and / or polyvinyl acetate must represent at least one third by weight of the total weight of the cellulose acetate + derivatives of polyvinyl alcohol.
• the actual coating of the powder grains is carried out during a coating operation during which the coating grains sprayed in solution in a solvent medium are sprayed onto the powder grains.
• the solvent medium comprises at least one dinitropolystyrene solvent chosen from the group consisting of cyclohexanone, tetramethylurea, nitrobenzene, butyrolactone and tetramethylene sulfone still known under the trade name SULFOLANE®, so as to ensure good dissolution of the dinitropolystyrene .
• the preferred solvents for dinitropolystyrene in the context of the invention are cyclohexanone, tetramethylurea and tetramethylene sulfone.
• said solvent is used in admixture with an auxiliary solvent which is a good solvent for derivatives of polyvinyl alcohol and cellulose acetate.
• Acetone is a preferred auxiliary solvent in the context of the present invention.
• the amount of coating material deposited on the powder grains should be about two percent of the weight of the powder.
• This deposition is carried out by spraying the solution of coating material onto the powder grains, for example in a rotating bezel as for a conventional smoothing operation. After spraying the solution, the solvent medium is removed by air drying, optionally supplemented by drying in an oven, at atmospheric pressure or under vacuum.
• the powder grains thus coated are then compressed to the shape and dimensions of the desired fragmentable load.
• This compression is advantageously carried out at a temperature between 100 ° C and 140 ° C.
• a pressure close to 100 bars, or 10 replenish Pa, is generally sufficient for the usual loads intended for small and medium-caliber weapons.
• This second step of the process can take place either immediately after the first step or later in time as explained later in the description.
• the invention also relates to the fragmentable propellant charges thus obtained.
• load is meant in the sense of the present application either the propellant load in its entirety if it consists of a single element, or an element constituting the load if the latter consists of a plurality of elements.
• loads obtained by agglomeration of powder grains coated according to the invention have good mechanical strength when cold and still retain a certain mechanical strength at 100 ° C., in contrast to the loads obtained by agglomeration of powder grains coated only with polyvinyl nitrate .
• the loads according to the invention have ballistic properties comparable to those of traditional loads and in particular present, in combustion, a perfectly correct fragmentation.
• propellant charges according to the invention obtained from propellant powder with a simple nitrocellulose base will advantageously be used, this powder being the most common and the most common today. economic.
• the invention also relates to the powders constituting the loads according to the invention. More specifically, the invention relates to the propellant powder grains obtained at the end of the first step of the method according to the invention after evaporation of the solvent medium. These powder grains are coated with a film of a mixture containing at least one dinitropolystyrene, a stabilizer and a polyvinyl alcohol derivative chosen from the group consisting of polyvinyl nitrate and polyvinyl acetate.
• the invention particularly relates to coated grains obtained from a single-base nitrocellulose powder. Such powder grains keep well over time and can be easily transported. They thus make it possible to dissociate, in time and even in space, the two stages of the method according to the invention, according to the needs.
• the powder used is a conventional powder based on nitrocellulose in cylindrical grains having a central hole, web (thickness to be burned) 0.25 mm. At the start, the powder is unsmoothed and not graphitized and its potential is 4,034 joules / g, or 965 cal / g.
• the temperature of the coating solution is 60 ° C, the temperature of the bezel being 25 ° C.
• Fragmentable charges according to the invention were made from propellant powder in grains coated with a mixture of polyvinyl nitrate (NPV) and dinitropolystyrene (DNPS) in the presence of 2-nitro diphenylamine (2-NDPA) as a stabilizer.
• NPV polyvinyl nitrate
• DNPS dinitropolystyrene
• 2-NDPA 2-nitro diphenylamine
• the percentages are expressed by weight relative to the total weight of the powder.
• the dinitropolystyrene used had a nitrogen content of 14.81%, an average molecular weight of 500,000 and a softening point above 260 ° C. It is this dinitropolystyrene which was used in all the examples.
• the compression of the coated grains was carried out in a similar manner to that described in Example 1, the compression temperature being 130 ° C.
• the residual percentage of cyclohexanone is expressed by weight relative to the total weight of the load.
• a fragmentable charge was made according to the invention from propellant powder in grains coated with a mixture of polyvinyl acetate (AcPV) and dinitropolystyrene (DNPS) in the presence of 2-nitro diphenylamine (2-NDPA) as stabilizer.
• AcPV polyvinyl acetate
• DNPS dinitropolystyrene
• 2-NDPA 2-nitro diphenylamine
• a fragmentable charge according to the invention was made from propellant powder in grains coated with a mixture of dinitropolystyrene (DNPS), polyvinyl nitrate (NPV) and polyvinyl acetate (AcPV) in the presence of 2-nitro diphenylamine (2-NDPA) as a stabilizer.
• DNPS dinitropolystyrene
• NPV polyvinyl nitrate
• AcPV polyvinyl acetate
• 2-NDPA 2-nitro diphenylamine
• Examples 7 and 8 demonstrate that polyvinyl acetate can replace polyvinyl nitrate in all proportions in the context of the present invention.
• a fragmentable charge was made according to the invention from propellant powder in grains coated with a mixture of dinitropolystyrene (DNPS), polyvinyl nitrate (NPV) and cellulose acetate (AcCell) in the presence of 2-nitro diphenylamine (2-NDPA) as a stabilizer.
• DNPS dinitropolystyrene
• NPV polyvinyl nitrate
• AcCell cellulose acetate
• 2-NDPA 2-nitro diphenylamine
• a fragmentable charge according to the invention was made from propellant powder in grains coated with a mixture of dinitropolystyrene (DNPS) and polyvinyl nitrate (NPV) in the presence of 2-nitro diphenylamine (2-NDPA) as stabilizer and using nitrobenzene as solvent.
• DNPS dinitropolystyrene
• NPV polyvinyl nitrate
• a fragmentable charge according to the invention was made from propellant powder in grains coated with a mixture of dinitropolystyrene (DNPS) and polyvinyl nitrate (NPV) in the presence of 2-nitro diphenylamine (2-NDPA) as stabilizer and using tetramethylurea as solvent.
• DNPS dinitropolystyrene
• NPV polyvinyl nitrate
• a fragmentable charge according to the invention was made from propellant powder in grains coated with a mixture of dinitropolystyrene (DNPS) and polyvinyl nitrate (NPV) in the presence of 2-nitro diphenylamine (2-NDPA) as stabilizer and using butyrolactone as solvent.
• DNPS dinitropolystyrene
• NPV polyvinyl nitrate
• a fragmentable charge was made according to the invention from propellant powder in grains coated with a mixture of dinitropolystyrene (DNPS) and polyvinyl nitrate (NPV) in the presence of 2-nitro diphenylamine (2-NDPA) as stabilizer and using tetramethylene sulfone as solvent.
• DNPS dinitropolystyrene
• NPV polyvinyl nitrate
• a fragmentable charge was made according to the invention using as a propellant powder a composite powder whose composition was as follows:
• ATEC designates triethyl citrate acetate of formula:

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Crystallography & Structural Chemistry (AREA)
• Paints Or Removers (AREA)
• Medicinal Preparation (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)

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Cited By (3)

Citations (7)

• 1990
  • 1990-02-21 FR FR9002092A patent/FR2658505B1/fr not_active Expired - Lifetime
• 1991
  • 1991-02-11 DE DE1991611097 patent/DE69111097T2/de not_active Expired - Fee Related
  • 1991-02-11 EP EP19910400319 patent/EP0446085B1/de not_active Expired - Lifetime

Patent Citations (7)

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