GB1605359A - Process for the production of caseless ammunition - Google Patents

Description

(54) PROCESS FOR THE PRODUCTION OF CASHLESS AMMUNITION VWe DYNAMrr NOBEL ANoEsE11'r, a Germany Company, of 521 Troisdorf, Near Cologne, Germany do hereby declare the invention, for which Wwe pray that a patent may be granted to me/us, and the method by which it is to be performed, to be particularly described in and by the following statement This invention relates to a process for producing shaped propellent charge bodies for use as caseless ammunition, which propellent charge bodies are formed of high-temperatureresistant propellant It has long been known that nitrocellulose grains can be made porous in order to increase the rate of combustion thereof by the addition of removable fillers, for example water-soluble metal nitrates (see German Patent No. 75,822).

In this case, the degree of porosity is directly proportional to the quantity of filler added and subsequently removed. However, the fillers can only be extracted as long as the nitrocellulose is present in solvent-moist swollen form.

Caseless propellent charges have hitherto been used for a variety of purposes. They have the advantage of low weight by virtue of the absence of a metal cartridge case because of which, in addition, their production is simpler than the production of conventional cartridge ammunition. However, difficulties are liable to be encountered in the handling of caseless propellent charges in that the propellent moulding tends to disintegrate readily and form crumbs. In addition, caseless propellent charges are not sufficiently resistant to moisture.

In an attempt to overcome these disadvantages, it has been proposed in German Auslegeschrift No. 1,796,283 to increase the strength of a shaped propellent charge by forming a wet and doughy cast propellent charge based on nitrocellulose with a cellulose binder, and hardening this charge. The evaporation of added water and/or solvent imparls porosity to the propellent moulding.

Unfortunately, this process is attended by the disadvantage that it is not possible to obtain a defined porosity in such a procedure either involving solely the evaporation of water and/or solvents or the prior removal of any fillers by washing with a solvent which dissolves such fillers.

In addition to using nitrocellulose powders, it has hitherto been proposed to use secondary, finely powdered explosives having a high selfignition temperature (above about 200 C), together with desensitising binders, as propellent charge powders for caseless ammunition.

However, these explosive/binder mixtures are not adequate replacements for nitrocellulosepropellent charge mixtures as propellent charge powders in general because in no way do they even remotely approach the favourable intemalballistic burn-up properties of nitrocellulosepropellent charge mixtures.

If an excessive proportion of binder is represent, these explosive/binder mixtures possess the disadvantage that the binder possesses a desensitising effect such that burn-up comes to an almost complete standstill, with the result that there is inadequate build-up of pressure in the cartridge chamber. Another disadvantage is the fact that unacceptable quantities of sunburnt reaction products, for example soot, remain behind both in the cartridge chamber and also in the barrel of the weapon because the calorific value and oxygen value of the propellant are very seriously affected by any substantial quantities of binder present.

According to the present invention, there is provided a process for the production of caseless ammunition, which comprises shaping a mixture of a secondary explosive, a binder and a filler and dissolving the filler out from the shaped propellent body produced using a solvent for the filler which is a non-solvent for the explosive and for the binder.

Shaped propellent bodies produced in accordance with the invention are surprisingly strong enough to be used as caseless ammunition and show superior ballistic properties to shaped propellent mouldings which have not been made porous.

In contrast to the nitrocellulose shaped propellent bodies described in German Auslegeschrift No. 1,796,283, the shaped propellent bodies obtained in the course of carrying out the process of this invention do not exist in a swollen form in which they still contain solvent, but instead contain an intimate solven-frce mixture of solid propellant, fillers and binder, the binder bonding all the solid particles to one another. It has surprisingly been found that when dissolving out the fillers from this intimate mixture, no other material is lost therefrom, the propellant together with the binder adhering well to one another.

The secondary explosives which may be used as propellants when carrying out the process of this invention include organic nitro compounds, specifically of the type derived from mononuclear aromatic compounds and nitramines provided that such compounds have a decomposition point of more than 2000C.

In the context of this invention, nitro derivatives of mononuclear aromatic compounds include nitrated aromatic compounds of the type in which single aromatic nuclei are linked to one another through one or more carbon atoms and/or through one or more sulphur, oxygen or nitrogen atoms, but not compounds in which aromatic nuclei are fused to one another.

Examples of nitrated mononuclear aromatic compounds are the amino derivatives of symmetrical trinitrobenzene and their acylation products, for example 2,2', 46', 6,6'hexanitrooxanilide or 2,2', 46', 6,6'-hexanitro N,N'4iphenyl urea Other nitrated mononuclear aromatic compounds which can be used are nitration products of diphenyl, stilbene, diphenyl oxide, diphenyl sulphide, diphenyl sulphone and diphenylamine.The compounds in question also include heterocyclic compounds substituted by picryl radicals, for example thiophene, triazine or pyrimidine substituted by picryl radicals, nitrated heterocyclic compounds, for example 1,3,6,8-tetranitro-carbazole and tetranitroacridone, and also such compounds as 3,3'-azo-bis-(2,2', 46', 6,6'-hexanitrodiphenyl), 3,3'-diamino-2,2', 4.4', 6,6'-hexanitrodiphenyl, 1 ,3-bis-(2,4,6-trinitrophenylamino)-2,4,6- trinitrobenzene and tetranitrodibenzo-l, 3a,4,6a,tetraaaapentalene.

The nitramines mentioned above as the second group of propellants which may be used when carrying out the process of this invention include, in particular, 3,3'-bis-(methylnitramino)2,2', 46', 6,6'-hexanitrodiphenyl, uinito-2,4,6- phenyl methyl nitramine (tetryl)and octogen. It is preferred to use octogen.

It is best to use as binder a thermoplastic plastics material which is finely dispersed in the propellant. For example, there can be used a polymer based on a polyvinyl acetal. The aldehydes used in the acetalisation of polyvinyl alcohol to produce such polymers will usually be aliphatic aldehydes containing from 1 to 6 carbon atoms, particularly butyraldehydes.

However, polyurethanes, polyesters, polyvinyl alcohols or poly(meth) acrylales may also be used as binders. The ratio by weight of propellant to binder is preferably from 98:2 to 60:40, more preferably from 86:14 to 78:22.

The thermoplast used as binder may be disperseC in the propellant powder cither mechanically or, better still, by means of a solvent. In the latter case, the propellant grains become uniformly coatcd with binder. This mixing operation is followed by moulding and/ or compression lo form firm shaped propellent bodies.

In addition to using polymeric binders, bifunctional monomers may also be used as binder. In such a case, mixing of the binder with the propellent charge powder is accompanied by radically initiated cross-linking or by condensation with the propellent charge powder, thereby providing the propellent body obtained with a firm structure.

Any additives may be used as fillers providing they have sufficient mechanical stability during moulding or pressing and are soluble in a solvent which has little or no effect upon the propellant and binder. Thermal stability is also necessary when thermoplasts are used as binder, since the propellant is then processed at elevated temperature. The fillers are preferably used in an amount of from 1 to 20% by weight of the mixture of compounds to be shaped.

Fillers which satisfy these requirements are, for example, inorganic compounds, particularly salts, for example acetals of alkali metals or alkaline earth metals, halides or nitrates of the alkali metals, alkaline earth metals and the ammonium cation, sulphales of the alkali metals and the ammonium cation and carbonates of the alkali metals. It is also possible to use certain organic compounds which correspond to the general formula (Rl, R2, R3, R4) NX, where R', R2, R3 and R4 represent hydrogen, alkyl or aryl radicals and X represents halogen, NO3,, SO4". It is also possible to employ ammonium salts of organic carboxylic acids for example, ammonium acetate or benzoate.

A particularly preferred filler is KNO3.

The above mentioned fillers possess good solubility in water which, for this reason, is also the preferred and generally used eluant.

However, the process according to the invention may also be carried out using fillers that are insoluble in water, although in this case the propellant and binder must be insoluble in the eluanl used.

The shaped propel lent bodies according to the invention are generally produced by mixing the propellant, binder and filler in finely particulate form in an inert solvent, for example petroleum ether. The mixture is then dried, optionally after filtration, and subsequently shaped or formcd into propellent bodies.

Shaping or forming into the required shapes is gencrally carried out by compression moulding, the pressure applied amounting to from 0.4 to 4 Mp/cm2 according to the binder used. The application of too low a pressure occasionally rcsults in processing difficulties, whcreas a high pressure produces a firm structure and an optimal ballistic result after the filler has been dissolved out.

In contrast to when working with nitrocellulose-based propellant, the moulding temperature may be as high as 1500C. The moulding temperature will howevcr dcpcnd in general upon the binder used. Moulding may, on occasion, also be carried out at room temperature.

Shaping can be carried out by extrusion as well as moulding.

The grain size and quantity of the fillers may vary within wide limits. The larger the quantity of fillers, the greater the degree of porosity. In addition, the size of the pores may be influenced by the particle size of the fillers used. The larger the particle size of the fillers, the larger the pores will be.

Comparison of propellent bodies produced by the process of this invention with propellent bodies which have not been made porous shows that, in the absence of pores, incomplete combustion of the propellant occurs to leave residues in the cartridge chamber whereas such behaviour is prevented when pores are present in the produce The following Examples, in which Example 5 is a comparative example, illustrate this invention.

EXAMPLES 1 leo 5 A propellant, a binder and a filler identified in the following Table were intimately mixed, where necessary after size-reduction, mixing being effected either mechanically or by means of an inert solvent, for example, an aliphatic hydrocarbon. Where a solvent was used, the mixture was then freed from the solvent by filtration or evaporation and dried at elevated temperature before being shaped. If mixing was carried out in the absence of a solvent, shaping could be carried out immediately after mixing.

Shaping was carried out in a mould heated to 100"C in which the propellantlbinder/filler mixture was subjected for 10 to 30 seconds to a pressure of from 1.2 to 1.8 Mp/cm2 (maximum).

The filler was then dissolved out from the shaped propellent body by treatment for 48 hours with flowing water at a temperature of 35 C.

The ballistic data of caseless ammunition produced in this way are summarised in the following Table. The a-octogen mentioned in this table had an average particle size of 50 Il.

The ballistic data shows that production of the propellent body by a process in accordance with the invention always gives better results than the comparative example (Example 5), even when the particle sizes of the fillers (Examples 1 to 3) or the quantity of filler (Example 4) were varied. In all the examples in which shaped propallent bodies had been made porous, the propellent bodies bumt cleanly, whereas in Example 5 the cartridge chamber was soiled by unburnt residues of propellanL Similar results are obtained when other secondary explosive mentioned herein were used instead of a-octogen.

EXAMPLE 6 87 parts by weight of dipicryl sulphone were mixed with 13 parts by weight of polyvinyl butyral (plasticised) and 4 parts by weight of KNO3 (grain fraction > 10 < 200 u). The resulting mixture was shaped for 30 seconds at 100"C under a pressure of 1. 8 Mp/cm2 . The pressings obtained were subsequently freed from the potassium nitrate therein by treatment for 48 hours with running water having a temperature of 35"C. Firing results with the composition showed it to produce a maximum pressure of 4115 bars, have a time 2.00 ms and give a projectile velocity after 5 metres of 805 m1.

EXAMPLE 7 Following the procedure of Example 5, 87 parts by weight of 2,4,6,2',4',6' hexanitrodiphenyl ether were mixed with 13 parts by weight of polyvinyl butyral (plasticised) and 4 parts by weight of KNO3 and the resulting mixture was shaped at 100"C under a pressure TABLE

Example No.

1 2 3 4 5 Composition (% by weight) octogen 83 83 83 83 83 Polyvinyl butyral (containing 2% by weight of dicyclohexyl phthalate as plasticiser) 17 17 17 17 17 Filler. KNO3 amount added to 100 parts by weight of propellant/binder mixture (parts by weight) 4 4 4 6 Grain size (l) of the KNO3 < 45 > 45 > 100 > 10 < 63 < 200 < 200 Moulding temperature (OC) 100 100 100 100 100 Moulding pressure(Mp/cm2) 1.8 1.8 1.8 1.8 1.8 Firing resulis:: (4.7 mm calibre hand fire arms) Maximum pressure (bars) 4026 4160 3995 3934 3538 Firing time (ms) 2.04 2.33 2.04 1.71 2.18 Velocity after 5 m (m's) 920 930 928 961 910 of 1.8 Mp/cm2 to form shaped propellent bodies.

After shaping, the potassium nitrate was dissolved out with warm water. In a firing test, caseless ammunition comprising a propellent body of the type thus produced yielded a maximum pressure of 1878 bars and a projectile velocity of 409 msl.

For comparative purposes, Examples 6 and 7 were repeated but without addition of the potassium nitrate. The washing with water required after moulding was of course not carried out in this case. The caseless ammunition produced with these propellent mouldings showed a completely inadequate projectile velocity which, in some cases, was so low that the projectile did not even completely clear the barrel of the weapon. In both cases, the maximum pressure produced amounted to around 400 bars.

WHAT WE CLAIM IS: 1. A process for the production of caseless ammunition, which comprises shaping a mixture of a secondary explosive, a binder and a filler and dissolving the filler out from the shaped propellant body produced using a solvent for the filler which is a non-solvent for the explosive and for the binder.

2. A process as claimed in claim 1, wherein the filler is an inorganic salt.

3. A process as claimed in claim 2, wherein the filler is a nitrate of an alkali or allcaline earth metal or is ammonium nitrate.

4. A process as claimed in claim 2, wherein the filler is an alkali metal sulphate or ammonium sulphate or alkali metal carbonate.

5. A process as claimed in claim 1, wherein the filler is a quaternary ammonium salt of formula (Rs, R2, R), R4) NX wherein R, R2 R3 and R4 represent hydrogen, alkyl or aryl and X represents halogen, NO3, or SO4".

6. A process as claimed in any one of the preceding claims, wherein the filler constitutes from 1 to 20% by weight of the said mixture.

7. A process as claimed in any one of the preceding claims, wherein the solvent is water.

8. A process as claimed in any one of the preceding claims, wherein the secondary explosive is a mononuclear aromatic compound as defined herein or a nitramino compound, said compound having a decomposition point of more than 2000C.

9. A process as claimed in claim 8, wherein the secondary explosive is one of the compounds: 2,2', 4,4', 6,6'-hexanitrooxanilide, 2,2', 4,4', 6,6'-hexanitro-N,N'4iphenyl urea, nitration products of diphenyl, stilbene, diphenyl oxide, diphenyl sulphide, diphenyl sulphate, diphenylamine, heterocyclic compounds substituted by picryl radicals, 3,3'-azo-bis-(2,2', 4,4', 6,6'-hexanitoodiphenyl-1 ,3-bis-(2,4,6- trinitrophenylamino)-2,4,6-trinitrobenzene and tetranitrodibenzo- 1 ,3a,4,6a-tetraazapentalene.

10. A process as claimed in claim 8, wherein the secondary explosive is 3,3'-bis(methylnitramino)-2,2', 4,4', 6,6'-hexanitrodiphenyl, trinitro 2,4,6-phenyl methyl nitramine or octogen.

11. A process as claimed in any one of the preceding claims, wherein the binder is an acetalised polyvinyl alcohol.

12. A process as claimed in claim 11, wherein the binder is polyvinyl butyral.

13. A process as claimed in any one of the preceding claims, wherein the ratio by weight of secondary explosive to binder employed is from 98:2 to 60:40.

14. A process as claimed in claim 13, wherein the ratio by weight of secondary explosive to binder employed is from 86:14 to 28:22.

15. A process as claimed in any one of the preceding claims, wherein said mixture is subjected to a pressure of from 0.4 to 4 Mp/cm2 during the shaping thereof.

16. A process for the production of caseless ammunition as claimed in claim 1, substantially as described in any one of the foregoing Examples.

17. Caseless ammunition, whenever produced by the process claimed in any one of the preceding claims.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (17)

**WARNING** start of CLMS field may overlap end of DESC **. of 1.8 Mp/cm2 to form shaped propellent bodies. After shaping, the potassium nitrate was dissolved out with warm water. In a firing test, caseless ammunition comprising a propellent body of the type thus produced yielded a maximum pressure of 1878 bars and a projectile velocity of 409 msl. For comparative purposes, Examples 6 and 7 were repeated but without addition of the potassium nitrate. The washing with water required after moulding was of course not carried out in this case. The caseless ammunition produced with these propellent mouldings showed a completely inadequate projectile velocity which, in some cases, was so low that the projectile did not even completely clear the barrel of the weapon. In both cases, the maximum pressure produced amounted to around 400 bars. WHAT WE CLAIM IS:

1. A process for the production of caseless ammunition, which comprises shaping a mixture of a secondary explosive, a binder and a filler and dissolving the filler out from the shaped propellant body produced using a solvent for the filler which is a non-solvent for the explosive and for the binder.

2. A process as claimed in claim 1, wherein the filler is an inorganic salt.

3. A process as claimed in claim 2, wherein the filler is a nitrate of an alkali or allcaline earth metal or is ammonium nitrate.

4. A process as claimed in claim 2, wherein the filler is an alkali metal sulphate or ammonium sulphate or alkali metal carbonate.

5. A process as claimed in claim 1, wherein the filler is a quaternary ammonium salt of formula (Rs, R2, R), R4) NX wherein R, R2 R3 and R4 represent hydrogen, alkyl or aryl and X represents halogen, NO3, or SO4".

6. A process as claimed in any one of the preceding claims, wherein the filler constitutes from 1 to 20% by weight of the said mixture.

7. A process as claimed in any one of the preceding claims, wherein the solvent is water.

8. A process as claimed in any one of the preceding claims, wherein the secondary explosive is a mononuclear aromatic compound as defined herein or a nitramino compound, said compound having a decomposition point of more than 2000C.

9. A process as claimed in claim 8, wherein the secondary explosive is one of the compounds: 2,2', 4,4', 6,6'-hexanitrooxanilide, 2,2', 4,4', 6,6'-hexanitro-N,N'4iphenyl urea, nitration products of diphenyl, stilbene, diphenyl oxide, diphenyl sulphide, diphenyl sulphate, diphenylamine, heterocyclic compounds substituted by picryl radicals, 3,3'-azo-bis-(2,2', 4,4', 6,6'-hexanitoodiphenyl-1 ,3-bis-(2,4,6- trinitrophenylamino)-2,4,6-trinitrobenzene and tetranitrodibenzo- 1 ,3a,4,6a-tetraazapentalene.

10. A process as claimed in claim 8, wherein the secondary explosive is 3,3'-bis(methylnitramino)-2,2', 4,4', 6,6'-hexanitrodiphenyl, trinitro 2,4,6-phenyl methyl nitramine or octogen.

11. A process as claimed in any one of the preceding claims, wherein the binder is an acetalised polyvinyl alcohol.

12. A process as claimed in claim 11, wherein the binder is polyvinyl butyral.

13. A process as claimed in any one of the preceding claims, wherein the ratio by weight of secondary explosive to binder employed is from 98:2 to 60:40.

14. A process as claimed in claim 13, wherein the ratio by weight of secondary explosive to binder employed is from 86:14 to 28:22.

15. A process as claimed in any one of the preceding claims, wherein said mixture is subjected to a pressure of from 0.4 to 4 Mp/cm2 during the shaping thereof.

16. A process for the production of caseless ammunition as claimed in claim 1, substantially as described in any one of the foregoing Examples.

17. Caseless ammunition, whenever produced by the process claimed in any one of the preceding claims.