GB2507609A

GB2507609A - Biodegradable thermoplastic composite material

Info

Publication number: GB2507609A
Application number: GB1310121.7A
Authority: GB
Inventors: Nigel Francis Maydew; Christopher Charles Hampton; Peter David Perry
Original assignee: AP PATENTS Ltd
Current assignee: AP PATENTS Ltd
Priority date: 2011-11-04
Filing date: 2011-11-04
Publication date: 2014-05-07
Anticipated expiration: 2031-11-04
Also published as: GB2496180B; GB201119098D0; GB2496180A; GB2507609B; GB201310121D0

Abstract

An extrudable and/or injection mouldable biodegradable thermoplastic composite material 36 for use with ordnance 10, comprises: a major percentage of natural-starch polyester polymer; and a minor percentage of powdered chemically-untreated straw. The straw being untreated is essential to provide uniform solidity to the composite material 36. This allows use of the composite material 36 in conventional extruding and injection moulding, whilst being suitably dense and strong to withstand firing, along with achieving a similar flight to a live round but 10 which may break apart on landing to facilitate biodegrading and digestion by animals. The biodegradable thermoplastic composite material 36 is ideally suited for disposable practice mortar rounds 10 and obturation disks or wadding of shotgun cartridges, thus dispensing with the need for retrieval following discharge.

Description

I

Biodegradable Thermoplastic Composite Material The present invention relates to ammunition formed at least in part of a biodegradable thermoplastic composite material, and more particularly but not necessarily exclusively to ammunition which is a practice mortar round and/or an obturation disk or wad of a shotgun cartridge or shell.

It is common for the military to practice firing weapons with non-live training rounds.

For example, mortar firing practice is undertaken in large dedicated spaces with mortars which do not contain detonators or explosives. However, to achieve realism, the weight and flight must be substantially identical to a live round.

Additionally, once the practice is completed, the training rounds must be collected as they are formed from non-biodegradable materials. This is extremely time-consuming and expensive. If shattering on landing, the fragments are often consumed by animals, such as cattle. The fragments are non-digestible, and this does lead to health problems for the animal in question.

Additionally, other forms of ammunition, for example, shotgun cartridges, are often ejected by users and not collected. The plastic obturation disk or wad interposed between the charge and the shot or slug is formed from non-biodegradable material and creates Utter in many areas of countryside by being ejected along with the shot or slug.

The disk or wad is often consumed by wildlife, and again being non-digestible does lead to health problems.

In order to provide a solution to these problems, substantial research and development has been undertaken to achieve a biodegradable material which is suitably dense and strong to withstand firing whilst also, in the case of a practice mortar round, achieves a flight similar to a live round and which breaks apart on landing.

According to a first aspect of the present invention, there is provided an extrudable and/or injection mouldable biodegradable thermoplastic composite material for use with ordnance and/or a ballistic device, the composite material comprising: a major percentage of natural-starch polyester polymer; and a minor percentage of powdered chemical] y-untreated straw.

Preferable and/or optional features of the first aspect of the invention are set forth in claims 2 to 26, inclusive.

According to a second aspect of the present invention, there is provided ordnance and/or a ballistic device comprising a body having at least one part formed of an extrudable and/or injection mouldable biodegradable thermoplastic composite material in accordance with the first aspect of the invention.

Preferable andlor optional features of the second aspect of the invention are set forth in claims 28 to 31, inclusive.

According to a third aspect of the invention, there is also provided ammunition comprising a body having at least one part formed of a biodegradable thermoplastic composite material in accordance with the first aspect of the invention.

The present invention will now be more particularly described, by way of example only.

with reference to the accompanying drawings. in which Figure 1 shows a first example of ammunition, in this case being a practice mortar round, in accordance with the present invention and having a projectile body formed at least in part of a biodegradable thermoplastic composite material; and Figure 2 shows a second example of ammunition, in this case being a shotgun cartridge or shell, in accordance with the present invention and having a projectile body formed at least in part of the biodegradable thermoplastic composite material.

Referring to the drawings, there is shown in Figure 1 a longitudinal elevational view of a pracdse or training mortar projectile 10 comprising a nose 12, main body i4, tail 16 and fin assembly 18. Figure 2 shows a longitudinal cross-sectional view through a typical shotgun cartridge 20 which comprises a, typically plastics. casing 22, a metal cap or head 24, primer centrally disposed on the head 24, a crimp 28 which is opposite the head 24 and which closes the casing 22, shot or slug 30 in the casing directly beneath the crimp 28, powder charge 32 in the casing 22 at the head 24, and a substantially rigid or stiff driving obturation disk or disks 34 interposed between the shot / slug 30 and charge 32. In conjunction with the obturation disk 34, conventional felt wading 34a may also be utilised.

In the case of the practice mortar round 10, the nose 12, main body 14 and tail 16 may all be formed integrally together as one-piece, for example, by turning or milling, with the fin assembly 18 being moulded and fitted thereafter. Alternatively, the entire mortar projectile may be moulded as one-piece. or one or more of the parts may be separately formed and then engaged with each other by mechanical engagement via integrally formed screw-threads and/or bonding, for example.

At least the main body 14 of the mortar projectile 10 is formed from a biodegradable thermoplastic composite material 36 which is suitable for extrusion in a conventional manner and/or injection moulding. For use in a practise mortar projectile 10, at least the main body 14 is able to remain intact when being fired from a mortar tube and is preferably frangible on impact when retuming to ground after firing, so as to scatter. To IS this end, the composite material 36 comprises a major percentage of natural-starch polyester polymer and a minor percentage of powdered chemically-untreated straw.

Preferably, an amount of the natural-starch polyester polymer in the finished composite material 36 is 60% or greater, and an amount of the powdered chemically-untreated straw is 40% or less.

The natural-starch polyester polymer is preferably potato starch which is ow cost and together with the powdered chemically-untreated straw provides good frangibility.

Dependent on application, such as with the obuiration disk 34 of the shotgun cartridge described above, other natural starches can be considered, and although not necessarily Umited one example would be corn starch. Tn the application of mortar projectiles, corn starch is less preferable due to it providing a less frangible or more flexible composite material 36. However, such a composite material 36 would be beneficial for the obturation disk 34. Other non-limiting examples of natural starches that can be considered for various applications include Polyhydroxyalkanoate [PHA], Poly-3-Flydroxybutyrate [PHB]. polyactide [PLA].

So as to impart thermoplastic properties to the composite material 36, the natural-starch polyester polymer is not cross-linked.

To improve the frangibility and consistency of the composite material 36, the straw is utiliseci. The straw improves dimensional stability during moulding of the material, and prevents or limits shrinkage. It is essential that the straw is both powdered and chemically-untreated. It has been found that the use of chemical anti-fungal additives amongst other things is detrimenta' to the uniform solidity of the finished composite material 36, thereby making it unsuitable for use with conventional extrusion and injection moulding techniques. The consistency is also improved by utilising more finely ground powered straw. 1-lowever, arger granular powered straw can be utilised, and the term powdered' used herein and throughout is intended to encompass larger granules.

Preferably, a nucleating agent is utilised as part of the composite matenal 36. The natural-starch polyester polymer is generally crystalline and the use of a nucleating agent benefits uniform crystailisation and anti-distortion during the production process of the material. The nucleating agent preferably forms 1% or less and more preferably in this culTent embodiment 0.5% or less of the composite material 36. To maintain the compostable characteristic of the finished composite material 36, the nucleating agent may beneficially be hydrated magnesium silicate, and in this case the hydrated magnesium silicate is powdered having a crystal size in the range of five to fifty microns. However, the liner the grain size, the better the integration during production.

To improve the integration or "wettillg" of the powdered and untreated straw with the natural-starch polyester polymer, and so that there is less likelihood of moisture absorption during machining, the composite material 36 preferably includes an internal lubncant, such as a metal stearate. So that the composite material 36 remains biodegradable, the metal stearate beneficially has an eighteen or less Carbon chain.

Beneficially, the metal stearate may be at least one of Calcium stearate and Zinc stearate.

The internal lubricant, if induded. preferably forms 0.5% or less of the composite material 36.

Beneficially, a plasticiser may be utilised. Although not necessarily required for the mortar projectile 10 utilising the potato starch polymer. the use of corn starch polymer results in a much more flexible composite material 36, and if this is to be used in applications which require frangibility then it is beneficial to include the plasticiser. So that the composite material 36 retains its biodegradable characteristics, the plasticiser is prcfcrably a natural oiL and may bc at least onc of soya oil, rapc sccd oil, maizc oil and palm oil. The plasticiser, if included, preferably forms 5% or less of the composite material 36.

The composite material 36 may further include a filler, and this may function as a densifier as necessary to add suitable mass, for example, to the main body of the practice mortar round 10. This may improve flight, since the mass or density of a five mortar round can be more easily matched.

Preferably the densifier is a natural densifier so that the composite material 36 remains compostable. In this case, is at least one of calcium carbonate, barium sulphate and IS silicon dioxide.

Beneficially, the composite material 36 may also include at least one colorant. This can be useful for spotting a landing of the practice mortar round at distance, for example, in the case of using colorant or colorants which impart a distinct tonal contrast with the surrounding environment, such as yellow or orange. In the alternative, a colorant or combination of colorants which aim to blend the practice mortar round 10 into the environment following landing can be considered. In this latter case, this would be beneficial due to the discarded mortar round 10 being disposable and thus left on the range to decompose and compost.

For the obturation disk 34, similar advantages as described above are evident, particularly including being able to blend into the environment during the biodegrading process.

The or each colorant is preferably a pigment. In this case, the or each pigment forms less than one percent of the composite material 36 thereby maintaining the composite material's compostable properties.

Although the biodegradable thermoplastic composite material is ideally suited to practice mortar rounds and obturation disks or wads of shotgun cartridges, it may be used to form at least parts of other forms of ammunition, dependent on requirements, such as disposable internal components of gun cartridges or shells.

In a final modification, the aforementioned filler may be or include a fertiliser. This would be advantageous following discharge due to the part of the ammunition then biodegrading and composting in the field or on the firing range, thus providing soil nutnents.

In order for the composite material of the invention to be classified as compostable' under European Standards EN13432 and EN7W0127, the constituent part in question must form less than 1%. As such, the composite material itself is biodegradable but may utilise compostable and/or biodegradable constituent parts.

It is thus possible to provide ammunition which comprises a one-piece or multi-part body formed at least in part of a biodegradable thermoplastic composite material. The thermoplastic material is beneficially a biodegradable starch-polyester polymer composite. Advantageously, the biodegradable thermoplastic composite material utilises a minor percentage of powdered untreated straw which aids in binding the material whilst also improving its biodegradability and compostability. The biodegradable thermoplastic composite material is primarily suitable for practice rounds in the case of mortars, and more generally parts of the ammunition which are typically discarded in the field following firing. It is thus possible to reduce the environmental impact of the ammunition whilst also dispensing with the need for clean up. The part or parts of the ammunition fornmd by the biodegradable thermoplastic composite material is/are preferable compostable. and/or digestible by wildlife.

The embodiments described above are provided by way of examples only. and further modifications will be apparent to persons skilled in the field without departhig from the scope of the invention as defined by the appended claims.

Claims

Claims 1. An extrudable andlor injection mouldable biodegradable thermoplastic composite material for use with ordnance and/or a ballistic device, the composite material comprising: a major percentage of natural-starch polyester polymer; and a minor percentage of powdered chemically-untreated straw.
2. An extrudable andlor injection mouldable biodegradable thermoplastic composite material as claimed in claim 1, wherein the natural-starch polyester polymer is one of corn starch and potato starch.
3. An extrudable andlor injection mouldable biodegradable thermoplastic composite material as claimed in claim I or claim 2, wherein the natural-starch polyester polymer is not cross-linked.
4. An extrudable andlor injection mouldable biodegradable thermoplastic composite material as claimed in any one of claims 1 to 3, wherein the major percentage of the natural-starch polyester polymer is 60% or greater.
5. An extrudable andlor injection mouldable biodegradable thermoplastic composite material as claimed in any one of claims 1 to 4, wherein the minor percentage of powdered untreated straw is 40% or less.
6. An extrudable and/or injection mouldable biodegradable thermoplastic composite material as claimed in any one of claims 1 to 5, further comprising a nucleating agent.
7. An extrudable andlor injection mouldable biodegradable thermoplastic composite material as claimed in claim 6, wherein the nucleating agent is hydrated magnesium silicate.
8. An extrudable and/or injection mouldable biodegradable thermoplastic composite material as claimed in claim 7, wherein the hydrated magnesium silicate is powdered having a crystal size in the range of five to fifty microns.
9. An extrudable and/or injection mouldable biodegradable thermoplastic composite material as claimed in any one of claims 5 to 8, wherein the nucleating agent forms 0.5% or less of the composite material.
10. An extrudable andlor injection mouldable biodegradable thermoplastic composite material as claimed in any one of claims 1 to 9, further comprising an internal lubricant.
11. An extrudable and/or injection mouldable biodegradable thermoplastic composite material as claimed in claim 10, wherein the internal lubricant is a metal stearate.
12. An extrudable andlor injection mouldable biodegradable thermoplastic composite material as claimed in claim 11, wherein the metal stearate has an eighteen or less Carbon chain.
13. An extrudable and/or injection mouldable biodegradable thermoplastic composite material as claimed in claim 11 or claitn 12, wherein the metal stearate is at least one of Calcium stearate and Zinc stearate.
14. An extrudable andlor injection mouldable biodegradable thermoplastic composite material as claimed in any one of claims 10 to 13, wherein the interna' lubricant forms 0.5% or less of the composite material.
15. An extrudable andlor injection mouldable biodegradable thermoplastic composite materia' as claimed in any one of claims I to 14, further comprising a plasticizer.
16. An extrudable andlor injection mouldable biodegradable thermoplastic composite material as claimed in claim 15, wherein the plasticizer is a natural oil.
17. An extrudable and/or injection mouldable biodegradable thermoplastic composite materia' as claimed in claim 16, wherein the natural oil is at least one of soya oil, rape seed oil, maize oil and palm oil.
1 8. An extrudable and/or injection mouldable biodegradable thermoplastic composite material as claimed in any one of claims 15 to 17, wherein the plasticizer forms 5% or less of the composite material.
19. An extrudable andlor injection mouldable biodegradable thermoplastic composite material as claimed in any one of claims 1 to i8, further comprising a filler.
20. An extrudable and/or injection mouldable biodegradable thermoplastic composite material as claimed in claim 19, wherein the filler is a densifier.
21. An extrudable andlor injection mouldable biodegradable thermoplastic composite material as claimed in claim 20, wherein the densifier is a natural densifier.
22. An extrudable andlor injection mouldable biodegradable thermoplastic composite material as claimed in claim 21, wherein the natural densifier is at least one of calcium carbonate, barium sulphate and silicon dioxide.
23. An extrudable andlor injection mouldable biodegradable thermoplastic composite material as claimed in any one of claims 1 to 22, further comprising a colorant.
24. An extrudable and/or injection mouldable biodegradable thermoplastic composite material as claimed in claim 23, wherein the colorant is a pigment.
25. An extrudable and/or injection mouldable biodegradable thermoplastic composite material as claimed in claim 24, wherein a plurality of pigments are provided.
26. An extrudable andlor injection mouldable biodegradable thermoplastic composite material as claimed in claim 24 or claim 25, wherein the or each pigment forms less than one percent of the composite material.
27. Ordnance and/or a ballistic device comprising a body having at least one part formed of an extrudable and/or injection mouldable biodegradable thermoplastic composite material as claimed in any one of the preceding claims.
28. Ordnance andlor a ballistic device as claimed in claim 27, which is a practise mortar round.
29. Ordnance and/or a ballistic device as claimed in claim 27, which is an obturation disk or wad of a gun cartridge.
30. Ordnance and/or a ba'listic device as claimed in claim 29, wherein the cartridge is a shotgun cartridge.
31. Ordnance andlor a ballistic device as claimed in any one of claims of 27 to 30, which is ammunition.
32. Ordnance andlor a ballistic device substantially as hereinbefore described with reference to Figure 1 or Figure 2 of the accompanying drawings.
33. Ammunition comprising a body having at least one part formed of a biodegradable thermoplastic composite material as claimed in any one of claims ito 26.