Improved compositions

Abstract

The invention relates to improved composition, there is provided an enhanced blast composition comprising the following components in the following relative proportions: component A: of from 25 to 45% by weight of a metal or metal alloy fuel, component B: of from 20% to 60% by weight of a high explosive energetic material, component C: of from 5% to 20% by weight of a polymerisable binder, component D: selected of from 0% to 30% by weight of an oxidising agent, the percentages by weight of components A, B, C, and D together with a crosslinking reagent, and minor additives, adding to 100%.

Description

[0001] Improved compositions

[0002] The invention relates to improved compositions, and yet further to enhanced blast compositions.

[0003] Typical enhanced blast compositions are used to provide a high degree of exothermic energy, in which, the event may extend beyond the duration of the detonation reaction.

[0004] According to a first aspect of the invention there is provided an enhanced blast composition comprises the following components in the following relative proportions:

[0005] component A: of from 25 to 45% by weight of a metal or metal alloy fuel, component B: of from 20% to 60% by weight of a high explosive energetic material,

[0006] component C: of from 5% to 20% by weight of a polymerisable binder, component D: selected of from 0% to 30% by weight of an oxidising agent, the percentages by weight of components A, B, C, and D together with a crosslinking reagent, and minor additives, adding to 100%.

[0007] In a highly preferred arrangement the composition may comprise component A comprises of from 35% to 45% by weight,

[0008] component B comprises of from 20% to 25% by weight,

[0009] component C comprises of from 8% to 16% by weight, and

[0010] component D comprises of from 20% to 30% by weight,

[0011] of the said composition together with a crosslinking reagent, and minor additives, adding to 100%.

[0012] Typical enhanced blast compositions comprise in the order of 20% metal fuel, such as aluminium. The use of higher metal loads is desirable, but due to large shear thickening forces, high loadings of fine metal powders may provideissues with forming homogenous mixtures, which is especially problematic when using a curable binder, as the metal powders may not be homogenously mixed with the high explosive, before the binder starts to gel and cross link.

[0013] The formulations as defined herein may provide an increase in overpressure duration (impulse) and peak overpressure compared to the same mass of explosive without a metal / metal alloy fuel and oxidiser. The increase in the duration of the overpressure allows the blast to do more work on the target.

[0014] The component A may be selected from any metal or metal alloy fuel, preferably aluminium, magnesium or aluminium alloys. Preferably the metal fuel has a particle size is in the range of from, 0.1 - 500 pm, more preferably in the range of from 0.1 to 20 pm.

[0015] Examples of preferred component B, high energy energetic filler are heteroalicyclic nitramines, such as for example RDX(cyclo-1 ,3,5-trimethylene, 2,4,6-trinitramine, cyclonite or Hexagen), HMX (cyclo-l,3,5,7-tetramethylene-2,4,6,8-tetranitramine, Octogen) or TATND (tetranitro-tetraminodecalin) and mixtures thereof. Other high energetic fillers may be TAGN, aromatic nitramines such as tetryl, ethylene dinitramine, and nitrate esters such as nitroglycerine (glycerol trinitrate), butane triol trinitrate or pentaerythrital tetranitrate. The component B may further comprise a highly IM energetic filler, such as, for example, Nitrotriazolone (NTO), Hexanitrostilbene (HNS), Nitroguanidine (Picrite), Triaminotrinitrobenzene (TATB), Guarnylureadinitramide (FOX-12), 1,1-diamino 2,2-dinitro ethylene (FOX-7).

[0016] Preferably the component B comprises at least one nitramine compound.

[0017] The composition comprises component C, a curable binder and may be selected from a non-energetic binder and / or an energetic binder. Preferably the binder is a non-energetic binder.Preferably the component C, polymerisable binder may be selected, such that it will form with the cross linking reagent polyurethanes, cellulosic materials such as cellulose acetate, polyesters, polybutadienes, polyethylenes, polyisobutylenes, PVA (polyvinyl acetate), chlorinated rubber, epoxy resins, two-pack polyurethane systems, alkyd / melanine, vinyl resins, alkyds, butadienestyrene block copolymers, and blends, copolymers and / or combinations thereof.

[0018] Examples of suitable energetic binder materials may be nitrocellulose, polyvinyl nitrate, nitroethylene, nitroallyl acetate, nitroethyl acrylate, nitroethyl methacrylate, trinitroethyl acrylate, dinitropropyl acrylate, C-nitropolystyrene and its derivatives, polyurethanes with aliphatic C- and N- nitro groups, polyesters made from dinitrocarboxylic acids and dinitrodiol and homopolymers of 3-nitrato-3 methyl oxetane (PolyNIMMO).

[0019] The component D may be any oxidiser, preferably ammonium perchlorate preferably the particle size is in the range of from, 1 - 250 pm, in a preferred arrangement the oxidiser may be bimodal or multimodal.

[0020] The use of high percentage loadings of metal or the use of high surface area reagents (small particle sizes) in compositions A to D in combination with a curable binder, leads to mixing a high viscosity composition. High viscosities may be difficult to process using bladed mixers, such as for example turbula mixers and may lead to a non-homogenous mixture. High viscosity mixes traditionally take many hours to form a homogeneous mixture, preferably to decrease the mixing time and still ensure homogeneity the composition may be mixed by non-high shear bladeless mixer, such as, for example resonant acoustic mixing (RAM).According to a further aspect of the invention there is provided a process for formulating a homogenous crosslinked polymer bonded enhanced blast explosive composition as defined herein, comprising the steps of:

[0021] i) forming a mixture of the composition as defined herein, comprising an explosive material, an oxidiser, a metal fuel, a polymerisable binder, and a cross linking reagent,

[0022] ii) causing the homogenous mixing and cure process to start of i) with a non-high shear bladeless mixer,

[0023] iii) causing the cure process to start.

[0024] Preferably step ii) is performed by applying a RAM stimulus to the mixture.

[0025] In a preferred arrangement a further step of iv) may comprise filling a munition with the admixture from step ii) or step iii).

[0026] Alternatively after step ii) the homogenous mixture the components A, B, C and D may be added to a munition or pot, and then the step iii) the cure process may be caused to start once the mixture has been transferred to the munition case or pot.

[0027] A yet further, preferred alternative may be adding the components A, B, C and D to a munition case or pot, and then causing step ii) of applying a RAM stimulus to the munition case or pot, to mix the composition in-case, (in-situ). Finally, causing the cure process to start in-munition case or pot, optionally still applying a RAM stimulus to the munition case

[0028] According to a further aspect of the invention there is provided a process for formulating a homogenous crosslinked polymer bonded enhanced blast explosive composition, as defined herein, in a munition case or pot, comprising the steps of:i i) adding an explosive material, an oxidiser, a metal or metal alloy fuel, a polymerisable binder, and a cross linking reagent to a munition case or pot, ii) applying a RAM stimulus to the munition case or pot, causing the homogenous mixing,

[0029] iii) causing the cure process to start.

[0030] A pot may be a liner or receptacle that an energetic material is filled with, which pot is then inserted into a munition case, to form a filled munition case.

[0031] The use of resonant acoustic stimulus allows for mixing and optionally mixing during curing, whilst the composition is in the munition case or pot. The munition case or pot may be individually brought into contact with a resonant acoustic stimulus, or more preferably a plurality of munition cases or pots may be arranged in a rack and the rack and hence munitions or pots, subjected to the resonant acoustic mixing stimulus, thereby providing a mixed-in-case product.

[0032] The resonant acoustic mixing stimulus cure process may be carried out under vacuum, so as to remove volatiles and degas i.e. remove air, to prevent the formation of voids in the final cured formulation.

[0033] The resonant acoustic mixing stimulus process may be affected at different frequencies, at afirstfrequency / powerthe resonant acoustic mixing stimulus may provide only homogeneous mixing of the formulation, but is insufficient to cause cure. At a second frequency / power the resonant acoustic mixing stimulus process provides both homogenous mixing of the composition and cure.

[0034] Resonant acoustic mixing is far removed from sonification (or ultrasound) techniques. Ultrasound employs very high frequencies, typically greater than 20KHz.

[0035] In a highly preferred arrangement the resonant acoustic mixing may be operated at a frequency in the range of less than 200Hz, preferably less than 100 Hz, preferably from 20 Hz to 100Hz, more preferably in the range of from 50Hzto 70Hz, yet more preferably 58Hz to 62hz. The resonant acoustic mixing occurs at very low frequencies, in the order of tens of hertz, compared to those used in sonification (ultrasound), which is tens of thousands of hertz.

[0036] Typically the resonant acoustic mixing stimulus may apply an acceleration force of up to 100g.

[0037] Resonant acoustic mixing induces microscale turbulence by propagating acoustic waves of a low frequency throughout a mixture. The resonant acoustic mixing system has a lower frequency of acoustic energy and can be more readily applied to larger scale of mixing than ultrasonic agitation. The mixing time for typical shear force mixers may be in the order of several hours to ensure homogenous mixing, in resonant acoustic mixing the stimulus may cause the time to be reduced to less than hour, more preferably less than 20 minutes or even less than 5 minutes. The period of time may depend on the size of the munition or pot that needs to be subjected to the resonant acoustic mixing stimulus.

[0038] The curing step, with the cross linking reagent, is exothermic and will generate further heat. It may be desirable to provide temperature-controlled jackets to a batch vessel or munitions (mixed in case) or pots, to ensure the mixture temperature is optimised for processing.

[0039] In a highly preferred composition the polymerisable binder is selected, such that it will from polyurethane, such that the cross linking reagent comprises an isocynate with two or more reactive sites, such as for example a diisocyanate.

[0040] Many energetic fillers, including RDX and HMX may be modified, either via stabilisers or coatings such that they have a degree of IM compliance The composition may comprise a plasticiser which may be selected from a non-energetic plasticiser and / or an energetic plasticiser. Preferably the plasticiser is a mixture of energetic and non-energetic plasticisers.

[0041] Examples of energetic plasticisers may be Butyl NENA, GAP (glycidyl azide polymer), BDNPA / F (bis-2,2-dinitropropylacetol / formal), dimethylmethylene dinitroamine, bis(2,2,2-trinitropropyl)formal, bis(2,2,2-trinitroethyl)formal, bis (2-fluoro-2,2-dinitroethyl)formal, diethylene gylcoldinitrate, glycerol trinitrate, glycol trinitrate, triethylene glycol dinitrate, tetrethylene glycol dinitrate, trimethylolethane trinitrate, butanetriol trinitrate, or 1 ,2,4-butanetriol trinitrate.

[0042] Examples of known non-energetic plasticisers may be, Di Octyl adipate(DOA), Di Octyl Sebacate (DOS), dialkyl esters or sebacic adipic, or, triacetin, tricresyl phosphate, polyalkylene glycols and their alkyl ether derivatives, eg polyethylene glycol, polypropylene gycol, and diethylene glycol butyl ether.

[0043] Examples of minor additives may for example comprise one or more stabilisers, e.g. carbamite (N,N1-diphenyl, NN1-diethylurea) or PNMA (para-nitromethylmethoxyaniline); and / or one or more ballistic modifiers, e.g. carbon black or lead salts: and / or one or more flash suppressants, e.g. one or more sodium or potassium salts, e.g. sodium or potassium sulphate or bicarbonate and one or more binder-to-energetic filler coupling agents and one or more antioxidants.

[0044] The cast explosive composition of the invention has utility both as a main charge or a booster charge in an explosive product. Often the composition will be the main charge. The composition of the invention may be used in any “energetic” application such as, for example, uses include mortar bombs and artillery shells as discussed above. Additionally, the inventive composition may be used to prepare explosives for gun-launch applications, explosive filings for bombs and warheads.

[0045] Except in the examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and / or use are to be understood as modified by the word “about.” All amounts are by weight of the final composition, unless otherwise specified. Further, the cast explosive composition may comprise, consist essentially of, or consist of any of the possible combinations ofcomponents described above and in the claims except for where otherwise specifically indicated.

[0046] Examples

[0047]

[0048] Table 1 shows the reagents used in the enhanced blast composition

[0049] An embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings of which:- Figures 1 a and 1 b shows a schematic of the fill of an HE ammunition using a resonant acoustic mixing stimulus process

[0050] Turning to fig 1 a and 1 b there is a general scheme 11 , for filling a munition 16, optionally via filling funnel 19(Fig 1b). The premix formulation, is a mixture of the explosive RDX, aluminium, ammonium perchlorate, HTBP polymerisable binder and other processing aids, optionally a catalyst and a cross linking reagent with at least two active isocyanate groups 14, are added to the premix to form the precure composition 15. The cross linking reagent may be a diisocyanate such as IPDI. The resultant precure admixture 15 in the munition is located on a platform 13, which is in mechanical contact with a resonant acoustic mixing stimulus source 17 to provide resonance at a frequency of 58 to 62 Hz. In order to secure the munitions 16 in place, they may be placed in a rack system 12, which may comprise further restraints 12a, 12b to secure the munition to the rack12 and platform 13 to ensure that the acoustic, that is vibrational energy, is transferred from the source 17 to the munitions 16 and precure composition 15.

[0051] The action of resonant acoustic mixing energy on the precure composition 15, ensures that the composition is thoroughly mixed to a homogenous state, the action of a stimulus to the mixed composition causes the cross linking reagent to react with the HTPB polymerisable binder.

[0052] During the resonant acoustic mixing process, the application of a vacuum 18, may assist to degas the curing composition, by removing trapped gases and volatiles, to reduce the instances of voids. The mixing arrangement may require additional thermal control, such as external heating or cooling to control the temperature of the composition whilst mixing.

[0053] Alternatively the composition ingredients may be dosed to a large batch mixing vessel, either volumetrically or by mass. The mixing vessel is then brought into mechanical contact with a resonant acoustic mixing stimulus source 17 to provide a batch cure process. The resulting curing composition may then be transferred to munitions or pots, in a traditional casting manner.

[0054] It should be appreciated that the compositions of the invention are capable of being incorporated in the form of a variety of embodiments, only a few of which have been illustrated and described above.

Claims

CLAIMS1. An enhanced blast composition comprises the following components in the following relative proportions:component A: of from 25 to 45% by weight of a metal or metal alloy fuel, component B: of from 20% to 60% by weight of a high explosive energetic material,component C: of from 5% to 20% by weight of a polymerisable binder, component D: selected of from 0% to 30% by weight of an oxidising agent, the percentages by weight of components A, B, C and D together with a crosslinking reagent, and minor additives, adding to 100%.

2. A composition according to claim 1 and whereincomponent A comprises of from 35% to 45% by weight,component B comprises of from 20% to 25% by weight,component C comprises of from 8% to 16% by weight, andcomponent D comprises of from 20% to 30% by weight.

3. A composition according to claim 1 or claim 2 and wherein component A is selected from magnesium or aluminium.

4. A composition according to anyone of the preceding claims, wherein component B is selected from RDX, HMX, FOX-7, TATND, HNS, TATB, NTO, HNIW, GLIDN, picrite, aromatic nitramines, tetryl, ethylene dinitramine, nitroglycerine, butane triol trinitrate, pentaerythritol tetranitrate, DNAN and trinitrotoluene.5 A composition according to claim 4, wherein the component B comprises at least one nitramine compound.6 A composition according to anyone of the preceding claims, wherein the component C polymerisable binder is selected, such that it will form with the cross linking reagent polyurethanes, cellulosic materials such as cellulose acetate, polyesters, polybutadienes, polyethylenes, polyisobutylenes, PVA, chlorinated rubber, epoxy resins, two-pack polyurethane systems, alkyd / melanine, vinyl resins, alkyds, butadiene-styrene block copolymers, polyNIMMO, polyGLYN, GAP, and blends, copolymers and / or combinations thereof.

7. A composition according to anyone of the preceding claims, wherein the component D is ammonium perchlorate.8 A process for formulating a homogenous crosslinked polymer bonded enhanced blast explosive composition as claimed in any one of the preceding claims, comprising the steps of:i) forming a mixture of the composition as claimed in any one of the preceding claims, comprising an explosive material, an oxidiser, a metal or metal alloy fuel, a polymerisable binder, and a cross linking reagent,ii) causing the homogenous mixing with a non-high shear bladeless mixer, iii) causing the cure process to start.

9. A process according to claim 8, comprising the further step of iv) filling a munition case or pot with the mixture from step ii) or step iii).

10. . A process according to any one of claims 8 to 9, wherein the homogeneous mixing is causes by applying a resonant acoustic mixing stimulus to the mixture.11 A process for formulating a homogenous crosslinked polymer bonded enhanced blast explosive composition as claimed in any one of claims 1 to 7, in a munition case or pot, comprising the steps of:i) adding an explosive material, an oxidiser, a metal or metal alloy fuel, a polymerisable binder, and a cross linking reagent to a munition case or pot, ii) applying a RAM stimulus to the munition case or pot, causing the homogenous mixing,iii) causing the cure process to start.

12. . A process according to claim 11, wherein the homogeneous mixing is caused by applying a resonant acoustic mixing stimulus to the munition case or pot.

13. A process according to any one of claims 8 to 12 wherein the cure process is caused by a thermal stimulus.

14. A process according to any one of the preceding claims, wherein the crosslinking reagent comprises an isocyanate, diisocyanate or triisocynate.

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