Soil-biodegradable injection-mouldable thermoplastic composition and shooting sports and hunting ammunition produced using same

Abstract

The invention relates to a soil-biodegradable injection-mouldable thermoplastic composition, suitable for use in ammunition, especially in wads and other components of cartridges for shooting sports and hunting. The composition comprises one or more biodegradable polyesters, preferably polybutylene adipate terephthalate (PBAT) and / or polybutylene terephthalate with sebacic acid (PBTSeb), with high fluidity, and in a proportion of ≥51%, and may be complemented with plasticised starch. This composition achieves above 90% biodegradation in soil in much less than two years, together with high impact resistance, lower moisture absorption (with the associated advantages of greater dimensional stability, lower production costs and better and safer ballistics), compatibility with existing injection and production processes, and lower production costs owing to its greater fluidity.

Description

[0001] DESCRIPTION

[0002] Thermoplastic composition moldable by injection and biodegradable in soil and ammunition for hunting and sport shooting made with it

[0003] This descriptive report refers, as its title indicates, to an injection-molded and soil-biodegradable thermoplastic composition, suitable for use in ammunition, especially in wads and other components of cartridges for hunting and sport shooting, and ammunition for hunting and sport shooting manufactured with it in some of its parts, comprising one or more biodegradable polyesters, preferably PBAT (polybutylene adipate terephthalate) and / or PBTSeb (polybutylene terephthalate with sebacic acid), with high fluidity, and in a proportion >51%, and may be complemented with plasticized starch, also known as TPS (thermoplastic starch), the composition being biodegradable in soil.

[0004] Field of invention

[0005] The invention relates to the field of injection-moldable and soil-biodegradable thermoplastic compositions, especially those used for the manufacture of parts of hunting and sporting shooting cartridges, and more especially those used for the manufacture of wads for said cartridges.

[0006] Current state of the art

[0007] Within the sector of manufacturing parts for hunting and sporting shooting cartridges, and in general many similar elements, there is a clear trend towards using compositions that minimize their environmental damage after use, increasing their biodegradability, especially in the soil.

[0008] Solutions such as the one described in US patent 6565640B1, "Compositions containing starch and / or modified starch and plasticizers," are well-known. This patent describes compositions that primarily use starch and modified starch, alone or optionally mixed with other polymers, particularly biopolymers. These compositions are not specifically designed for hunting or sport shooting products, but rather for food and beverage packaging, pharmaceuticals, and temporary protective coatings for technical devices. Therefore, they do not offer the specific properties required, such as impact or moisture resistance, dimensional stability, or shot resistance, which depend on a specific polyester content. For this reason, these compositions would not be particularly suitable for manufacturing hunting or sport shooting wads.Furthermore, by primarily using starches, its main objective appears to be to achieve biodegradability in water, without posing special biodegradability needs in soil.

[0009] Solutions such as the one described in patent ES2540789 “Biodegradable ammunition for firearms” are also known, which describes a case, a base and / or a bullet, whose main material is composed of biodegradable polymers of vegetable origin, or biodegradable elastomeric polymers of vegetable origin, or biodegradable elastomeric polymers of petroleum origin, or biodegradable polymers of petroleum origin, or thermoplastics of petroleum origin with a catalyst, or by PVA polyvinyl alcohol, with a minimum of 50% of the mixtures, plus an inert and non-toxic mineral filler from the group of carbonates or mineral salts, in different mixtures and because the specific gravity of the mixtures ranges between 0.6 gr / cm 3 and 6 g / cm³ 3It is more oriented towards bullet ammunition, and although the ammunition is composed of an inert mineral charge plus one of the other options (biodegradable polymers of vegetable origin, or biodegradable elastomeric polymers of vegetable origin, or biodegradable elastomeric polymers of petroleum origin, or biodegradable polymers of petroleum origin, or thermoplastics of petroleum origin with a catalyst, or by PVA polyvinyl alcohol), it does not contemplate at any time a mixture of plasticized starch and biodegradable polyesters as proposed in this invention, so it could not achieve the combination of technical effects of both components.

[0010] Also known are mixtures such as the one described in patent GB2507609A, "Biodegradable thermoplastic composite material," which describes an extrudable and / or injection-molded biodegradable thermoplastic composite material for use in devices such as mortars. This material has a majority percentage of natural starch polyester polymer and a smaller percentage of chemically untreated straw powder. The untreated straw is essential for providing uniform strength to the composite material. This biodegradable thermoplastic composite is ideal for disposable practice mortar rounds and shotgun shell wadding or obturation discs, eliminating the need for retrieval after firing. While this composition claims to be compostable according to EN 13432, it does not provide any evidence of its biodegradability in soil according to EN 17033.It also acknowledges its frangibility, indicating that it maintains its structural integrity up to a suitable maximum load and then tends to break into small fragments once that maximum load is exceeded, without plastic deformation. Its main application with these characteristics would be for mortars or for use in cartridges where the biodegradable material is used in the obturation disc, in cartridge models that employ this element, but not for the manufacture of wads as is done in hunting or sporting cartridges, which is the primary application of this invention.

[0011] The function of a wad is solely to separate the gunpowder from the shot, while in the case of a wad, its function is to separate the gunpowder from the shot and, additionally, to prevent the shot from damaging the gun barrel, improving ballistics and reducing barrel wear, especially in the bore, thus increasing safety. Furthermore, it would not be possible to manufacture wads with the materials described in patent GB2507609A using current injection molding equipment without modifications. Even if the equipment were modified to allow injection molding, the production process would be very expensive due to its complexity and low productivity, and would not be competitive with other products on the market, making it an unsuitable mixture for biodegradable wads.

[0012] Some cartridge plugs are specifically designed to biodegrade in soil, such as the one described in patent WO2024013775, "Plug for cartridges with characteristics of biodegradability in soil." This patent describes a cartridge plug with biodegradability characteristics, produced from a mixture of biodegradable materials, including poly(butylene succinate) (PBS) and poly(butylene adipate terephthalate) (PBAT), and possibly also thermoplastic maize starch (TPS), obtained by extruding native maize starch with a plasticizer. The patent states that its plugs are biodegradable in soil according to EN 17556, which includes biodegradability tests, as does part of EN 17033. This is an advantage over compostability, as in the previous case, since used plugs do not end up in a composting facility.However, its biodegradability in soil is limited, and it has not been proven to meet the EN 17033 standard, which is much more demanding in terms of biodegradability and environmental impact. EN 17033 requires additional technical specifications and tests beyond those established by EN 17556. These additional laboratory tests determine its chemical composition, particularly for regulated metals and hazardous substances, its biodegradation in soil, and its ecotoxicity—that is, its toxic effects on plants, invertebrates, and microorganisms. One of the main criteria of EN 17033 is the requirement to achieve >90% biodegradation under aerobic conditions for the plastic—that is, the conversion of organic carbon into CO2—in natural soil at 20–28°C within two years, using a standardized test to measure CO2 respiration.

[0013] Furthermore, comparative experimental tests conducted between the wad described in WO2024013775 and wads using the composition discussed in this report show that the pressure obtained in the firearm is significantly higher with the wad described in WO2024013775 at velocities similar to the standard for polyethylene wads. This implies problems of greater internal wear on the firearm and a higher risk of damage or deformation that could affect the shooter's safety, shortening the firearm's lifespan. These comparative experimental tests also demonstrate that the impact resistance of the wad described in WO2024013775 is lower than that of wads using the composition discussed in this report, with the difference being particularly noticeable at -10°C. This indicates a particular fragility at low temperatures, which poses a problem for hunting and sport shooting in winter and in geographically cold areas.

[0014] Solutions such as the one described in patent EP4155659, "Biodegradable shotshell components," are also known. This patent describes devices and methods for shotgun cartridges with biodegradable components, where one or more of the shell components can be made of biodegradable materials. They use cellulosic fibers in a proportion >40% and wax to provide reliable gas sealing and obturation properties at high pressures. The patent states that it is biodegradable but does not specify the conditions under which it will be biodegradable. Furthermore, as in the previous case, the scope of application is different. Its primary application would be for the obturating disc, which, as previously mentioned, separates the gunpowder from the shot. However, in the case of a wad, its function is to separate the gunpowder from the shot and prevent the shot from damaging the gun barrel, as well as improve ballistics.This could not be achieved with the described mixture due to its lack of structural strength. Furthermore, as in the previous case, it would not be possible to manufacture blocks with these materials using current injection molding equipment, or, if they were modified to be injection-ready, the production process would be very expensive due to its complexity and low productivity. Patent EP4155659 describes the manufacturing process required for these components, and it is a complex, expensive process that cannot be carried out with conventional thermoplastic injection molding equipment, which is common in the industry.

[0015] It should also be noted that the use of waxes in the product compromises ballistics due to possible deposits in the barrel and their low thermal stability, which negatively affects the weapon's lifespan and the safety of its use.

[0016] Similarly, there are solutions like the one described in WO2014135289 “Wad for cartridge,” which shows a cartridge plug made of a water-soluble and compostable plastic material. After injection molding, it can be assembled into a cartridge without any further preparation, offering better conditions than a polyethylene plug. Its main objective is to achieve optimal moisture content (2-10%) directly during the injection molding process. While the material is water-soluble, it is not specified as being biodegradable in water, which creates a high risk of product accumulation in water. Although compostable if collected, the plugs, once used, do not usually end up in a composting facility but are typically discarded in nature, usually in the soil. Since they are not biodegradable in soil, they cause a significant environmental impact.

[0017] Furthermore, the material described has a moisture content between 2-10% to achieve the appropriate technical properties for the application, as stated in the document itself. This necessitates a different injection molding process than the standard dowel injection molding method, thus increasing the cost of dowel production.

[0018] Another problem with this product is that, because the material contains a high percentage of PVA, a highly hygroscopic component, the wad or manufactured product absorbs water very easily, posing risks to its technical performance. For example, the material may become too soft under its modulus, oxidation reactions may occur with the shot, vapor generation may occur, and pressure may increase. All of these negatively impact safety during cartridge use, as explained in the document itself. On the other hand, patent WO9858998, "Disposable articles for the military or pyrotechnic industries, non-folding roads, driving or walking aids made of biodegradable materials," generically describes the manufacture of biodegradable products, including products for military and pyrotechnic applications, guaranteeing that these materials have the required strength and stability for their intended use.To achieve this, they use polymer mixtures that combine TPS and polyesters, with which they attempt to achieve biodegradability according to the DIN 54900 compostability standard, but they do not indicate that their technical objective is to achieve biodegradability in soil.

[0019] Although it mentions achieving the required strength and stability, it does not specify how this is achieved, nor how these properties relate to the component proportions. Since many of the desired properties in the manufacture of components for hunting and sporting cartridges, such as high-volume, low-cost component production with excellent impact and moisture resistance, are closely linked to a specific biopolyester ratio and melt flow index, this document cannot usefully anticipate these relationships because it provides no helpful information in this regard.

[0020] Furthermore, in the manufacture of components for hunting and sporting cartridges, achieving biodegradability in soil is a key technical objective, and moreover, improved biodegradability in soil compared to the timeframes required by the EN 17033 standard. This necessitates the search for component mixtures with specific proportions, and the undertaking of experimental tests to combine these factors with high productivity and low production costs, greater moisture stability, and improved mechanical and ballistic properties. This can only be achieved with a more precise composition and the specific use of high MVR polyesters, which cannot be deduced or verified in this document.

[0021] It is clear that there is a growing social demand and legal requirement for hunting and sport shooting products, especially wads, that meet or exceed stringent regulations, such as the EN 17033 standard, to minimize the environmental impact of these activities. To achieve this, they must be biodegradable in soil, preferably within a shorter timeframe than that specified in the standard. This presents a significant technical challenge: in addition to improved soil biodegradability, a series of other technical requirements must also be met to create a product that, compared to existing solutions, combines all the desired characteristics, which are:

[0022] - High impact resistance, even at sub-zero temperatures

[0023] - Fluidity that allows the blocks to be injected at a lower temperature, with short injection cycles, increasing production and lowering its cost, all using conventional injection machines.

[0024] - Low moisture absorption.

[0025] - High dimensional stability and properties such as impact, modulus and resistance.

[0026] - Compatible with all types of shot

[0027] - High safety during ballistics, preventing accumulation of water vapor inside the weapon and high firing pressures that could affect the ballistics and even damage the weapon.

[0028] - To prevent the softening of the wadding material, which could obstruct the escape of gases generated during the gunpowder explosion, increasing the pressure.

[0029] - Safer and more economical material that does not require special conditioning, packaging, logistics or handling processes to prevent it from absorbing moisture.

[0030] A product that solves the technical problem of combining all these features into a single solution would produce a clear improvement and advance in the state of the art of the sector, not anticipated or deducible from known documents.

[0031] Description of the invention

[0032] To solve this existing problem in the manufacture of biodegradable components for hunting and sport shooting cartridges, especially for wads, by improving the current state of the art, the injection moldable and soil-biodegradable thermoplastic composition of the present invention has been devised, which comprises one or more biodegradable polyesters with a melt volume rate (MVR) greater than or equal to 1cc / 10min, measured at 190°C / 2.16Kg, in a proportion greater than or equal to 51% by weight with respect to the total, and may additionally comprise plasticized starch in a proportion less than or equal to 49% by weight with respect to the total, and other components, the composition being soil-biodegradable.

[0033] Los poliésteres biodegradables son elegidos del grupo formado por PBAT (tereftalato de adipato de polibutileno, siglas del inglés polybutylene adipate terephthalate), PBTSeb (tereftalato de polibutileno, siglas del inglés polybutylene perephthalate, con acido sebácico), PHB (polihidroxibutirato o ácido polihidroxibutírico), PHA (polihidroxialcanoato), policaprolactona, PLA (ácido poliláctico), PBS (polibutileno succinato), PBSA (polibutileno succinato adipato) y PBTS (tereftalato de polibutileno succinato) siendo preferentemente PBAT, PBTSeb o una mezcla de ambos.

[0034] Optionally biodegradable polyesters can also include monomers biobased.

[0035] These biodegradable polyesters have a flow rate with an MVR greater than or equal to 1cc / 10min, measured at 190°C / 2.16Kg., preferably with an MVR greater than or equal to 10cc / 10min, measured at 190°C / 2.16Kg, more preferably with an MVR greater than or equal to 20cc / 10min, measured at 190°C / 2.16Kg, and much more preferably with an MVR greater than or equal to 40cc / 10min, measured at 190°C / 2.16Kg.

[0036] Plasticized starch comprises one or more starches obtained from corn, potato, pea, tapioca, cassava, or any other starch-containing biomass. The starch may be native, modified, or derived from starch.

[0037] The plasticized starch also comprises one or more plasticizing agents selected from the group consisting of water, polyhydric alcohols, ethers, thioethers, their esters, or a combination thereof, as well as any other compound or polymer capable of transforming starch into thermoplastic starch. Examples of some of the usable plasticizers are: water, glycine, sorbitol, urea, polyethylene glycol, ethylene glycol, diethylene glycol, neopentyl glycol, sorbitol monoacetate, sorbitol diacetate, sorbitol monoethoxylate, ethoxylated polyglycerol, sorbitol diethoxylate, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, polyesters or polyesteretheramides, and mixtures thereof.

[0038] This thermoplastic composition is also intended to include other components selected from the group consisting of PVA (polyvinyl alcohol), PPC (polypropylene carbonate), PGA (polyglycolic acid), cellulose, modified cellulose, fibers, colorants, impact modifiers, organic and inorganic fillers, thermal stabilizers, hydrolysis stabilizers, UV stabilizers, lubricants, enzymes, biodegradability accelerators, other additives, and other biodegradable polymers. All compositions obtained according to this specification are biodegradable in soil, guaranteeing at least 90% biodegradability after a maximum of two years, meeting and exceeding the specifications of EN17033 at the time of application. It is preferable that this minimum 90% degradability be achieved in less than one year, and more preferably in less than 200 days.All products are also compostable according to EN 13432 and some of them are additionally biodegradable in water such as those containing PHA (polyhydroxyalkanoates), PHB (polyhydroxybutyrate), PVA (polyvinyl acetate), polycaprolactone, starch, cellulose, PGA (polyglycolic acid).

[0039] The preferred application of this injection-molded and biodegradable thermoplastic composition in soil is in the manufacture of ammunition for hunting and sport shooting, preferably the manufactured ammunition being a part of a shotgun cartridge, and more preferably a wad being the part of the shotgun cartridge.

[0040] Advantages of the invention

[0041] This injection-molded, soil-biodegradable thermoplastic composition offers numerous advantages over currently available materials for this application. The most significant advantage is its biodegradability in soil, guaranteeing at least 90% biodegradability after a maximum of two years, according to EN 17033 specifications at the time of application. In fact, experimental tests have shown that this minimum 90% degradability is achieved in a considerably shorter time—less than a year, or even less than 200 days. This represents a major advantage over existing water-soluble solutions, as a product's water solubility does not guarantee its biodegradability in water or soil, and over compostable products, which require collection.

[0042] It should also be noted that some products used in this thermoplastic composition are also additionally biodegradable in fresh and seawater according to ASTM D7081, ISO 14851 and ISO 14852 standards.

[0043] Another major advantage of this thermoplastic composition is the high impact resistance of products made with it, thanks to its biodegradable polyester content (>51%), allowing for very high pressure resistance at the moment of firing. It is also noteworthy that, due to the high percentage of polyesters, the final product made with this composition exhibits lower moisture absorption compared to other products on the market. This results in greater dimensional stability, greater stability of properties, especially impact, modulus, and resistance, and greater compatibility with all types of shot. The presence of moisture in the product can cause chemical and redox reactions between the product and the shot, especially with lead and steel shot, which are the most commonly used in the industry.

[0044] Another notable advantage, also due to lower moisture absorption, is the increased safety during firing. High humidity can cause water vapor to accumulate inside the firearm, leading to high pressures that can affect ballistics and even damage the weapon. Such risks have been observed in commercial products, resulting in their recall for safety reasons. Preliminary investigations and findings have shown that shot cartridges can, in some cases, cause a pressure increase in certain gun barrels, potentially leading to ejection from the barrel near the chamber. Similarly, the lower moisture absorption prevents the wad material from softening and obstructing the passage of gases generated during the gunpowder explosion, thus increasing pressure and causing the aforementioned risks.It also avoids the risks that, at low temperatures, the water absorbed by the material can freeze and weaken the wad material, negatively affecting ballistics and safety.

[0045] These characteristics of high biodegradability in soil, even in water, combined with high pressure resistance and low moisture absorption, make this composition ideal for the manufacturing processes of ammunition for hunting and sport shooting, especially shotgun cartridges, and more specifically the shotgun cartridge wad, which is the element responsible for withstanding the high pressure of the shot, and for protecting the shotgun barrel from erosion caused by the pellets during firing and for good ballistics and patterning.

[0046] Another important advantage is that this thermoplastic composition has a higher flowability than other known products, thanks to the use of high flowability polyesters (minimum MVR >1cc / 10min, preferably MVR >10cc / 10min and even more preferably MVR >20cc / 10min or even MVR >40cc / 10min). This allows the thermoplastic injection process for manufacturing the plugs, or other parts of the cartridge as the case may be, to be carried out at a lower temperature, thus reducing the cooling time and consequently the total injection cycle time, increasing production and therefore significantly reducing its economic cost.

[0047] Another advantage of the present invention is that it exhibits high impact resistance even at temperatures as low as -30°C, which provides significant advantages in ballistics for hunting and sport shooting in geographical areas with low temperatures, especially the USA and northern Europe.

[0048] Likewise, another added advantage is that, thanks to the greater flexibility of the material due to not containing PBS, and having a higher percentage of PBAT or equivalent, a greater recovery of the wad is obtained during its projection, which improves ballistics, and especially the projection of the pellets or pattern.

[0049] We must mention that experimental tests have demonstrated that wads, and other cartridge components, made with this thermoplastic composition result in lower internal pressures than wads in the examples of patent WO2024013775, which contain 50-70% PBS and 30-50% PBAT, under the same cartridge conditions, while achieving similar muzzle velocities. This translates into greater chamber life and reliability, and a reduced risk of accidents.

[0050] It is also important to highlight that this thermoplastic composition allows for the production of products that meet and exceed the specifications of EN 17033 at the time of application, a much more stringent standard than EN 17556, under which some products on the market are certified as biodegradable in soil. EN 17556 only covers biodegradability tests (percentage of organic carbon conversion to CO2), while EN 17033 requires additional, much more demanding tests, such as analyses for heavy metals and hazardous substances, and ecotoxicity in plants, invertebrates, and microorganisms.

[0051] Description of the figures

[0052] Figure 1 shows a graph of biodegradability in soil, according to ISO17556, of thermoplastic compositions according to the invention, one containing starch (TPS) and a percentage > 51% of biodegradable polyester, and another containing a percentage > 51% of biodegradable polyester, without starch (TPS), both compared with the biodegradability of cellulose as a reference in each case.

[0053] Figure 2 shows photos of different materials after being in contact with steel shot for 7 days at 90% relative humidity and 50°C temperature, to illustrate the chemical and redox reactions between the plastic material used and the shot.

[0054] Preferred embodiment of the invention

[0055] The injection-moldable, soil-biodegradable thermoplastic composition is suitable for use in ammunition, military and pyrotechnic applications and comprises one or more biodegradable polyesters with a melt volume rate (MVR) greater than or equal to 1 cc / 10 min, measured at 190°C / 2.16 kg, in a proportion greater than or equal to 51% by weight of the total, and may additionally comprise plasticized starch in a proportion less than or equal to 49% by weight of the total, and other components, the composition being soil-biodegradable.

[0056] Los poliésteres biodegradables son elegidos del grupo formado por PBAT (tereftalato de adipato de polibutileno, siglas del inglés polybutylene adipate terephthalate), PBTSeb (tereftalato de polibutileno, siglas del inglés polybutylene perephthalate, con acido sebácico), PHB (polihidroxibutirato o ácido polihidroxibutírico), PHA (polihidroxialcanoato), policaprolactona, PLA (ácido poliláctico), PBS (polibutileno succinato), PBSA (polibutileno succinato adipato) y PBTS (tereftalato de polibutileno succinato) ? being preferably PBAT, PBTSeb or a mixture of both.

[0057] Optionally biodegradable polyesters can also include monomers biobased.

[0058] These biodegradable polyesters have a flow rate (MVR) greater than or equal to 1 cc / 10 min, measured at 190°C / 2.16 kg, preferably with an MVR greater than or equal to 10 cc / 10 min, measured at 190°C / 2.16 kg, more preferably with an MVR greater than or equal to 20 cc / 10 min, measured at 190°C / 2.16 kg, and even more preferably with an MVR greater than or equal to 40 cc / 10 min, measured at 190°C / 2.16 kg. The plasticized starch comprises one or more starches obtained from corn, potato, pea, tapioca, cassava, or any other starch-containing biomass. The starch may be native, modified, or starch-derived.

[0059] The plasticized starch also comprises one or more plasticizing agents selected from the group consisting of water, polyhydric alcohols, ethers, thioethers, esters thereof, or a combination thereof, as well as any other compound or polymer capable of transforming starch into thermoplastic starch. Examples of some of the usable plasticizers are: water, glycine, sorbitol, urea, polyethylene glycol, ethylene glycol, diethylene glycol, neopentyl glycol, sorbitol monoacetate, sorbitol diacetate, sorbitol monoethoxylate, ethoxylated polyglycerol, sorbitol diethoxylate, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, polyesters or polyesteretheramides, and mixtures thereof.

[0060] This thermoplastic composition is also intended to optionally comprise other components selected from the group consisting of PVA (polyvinyl acetate), PPC (polypropylene carbonate), PGA (polyglycolic acid), cellulose, modified cellulose, fibers, colorants, impact modifiers, organic and inorganic fillers, thermal stabilizers, hydrolysis stabilizers, UV stabilizers, lubricants, enzymes, biodegradability accelerator additives, other additives and other biodegradable polymers.

[0061] All compositions obtained according to this document are biodegradable in soil, guaranteeing at least 90% biodegradability after a maximum of two years, meeting and exceeding the specifications of the EN17033 standard at the time of application. It is preferable that this minimum 90% degradability be achieved in less than one year, and more preferably in less than 200 days. Some products are also additionally biodegradable in water, such as those containing PHA (polyhydroxyalkanoates), PHB (polyhydroxybutyrate), PVA (polyvinyl acetate), polycaprolactone, starch, cellulose, PGA (polyglycolic acid), etc.

[0062] The preferred application of this injection-molded, biodegradable thermoplastic composition is in the manufacture of ammunition for hunting and sport shooting, preferably using a shotgun cartridge as part of the cartridge, and more preferably using a wad as part of the shotgun cartridge. Examples of experimental tests and their results

[0063] This composition has been subjected to intense experimental testing to determine its components, their percentages and its effect on solving the technical problem posed, of which we show some of the results as an example.

[0064] Example 1 - Biodegradability in soil according to EN17033

[0065] One of the main criteria of the EN 17033 standard is the requirement of >90% biodegradation under aerobic conditions for plastic, i.e., conversion of organic carbon into CO2, in a natural soil at 20 to 28°C within 2 years using a standardized test to measure CO2 respiration.

[0066] Figure 1 shows an example of a soil biodegradability graph, made according to EN 17033, of thermoplastic compositions according to the invention, one containing TPS starch and a percentage > 51% of biodegradable polyester (2), compared with the biodegradability of cellulose (1) as a reference ? and another containing a percentage > 51% of starch-free biodegradable polyester TPS (3), also compared to the biodegradability of cellulose (4) as a reference

[0067] The EN 17033 standard currently requires that at least 90% biodegradability be achieved after two years of testing. Figure 1 shows that the thermoplastic composition according to the invention, containing TPS starch and >51% biodegradable polyester (2), achieves the same biodegradability as cellulose (1), exceeding 90%, in 150 to 200 days. The thermoplastic composition according to the invention, containing >51% biodegradable polyester without TPS starch (3), also achieves the same biodegradability as cellulose (4), exceeding 90%, in approximately 360 days. In both cases, the biodegradability requirements of the standard are significantly exceeded.

[0068] The EN 17033 standard also requires that materials undergo laboratory testing to determine, among other things,

[0069] - its chemical composition (in particular, for regulated metals and hazardous substances),

[0070] - its biodegradation in the soil, and - its ecotoxicity (i.e., its toxic effects on plants, invertebrates, and microorganisms).

[0071] The thermoplastic composition according to the invention has also passed all these tests by a wide margin.

[0072] Example 2 - Impact resistance

[0073] The thermoplastic composition according to the invention achieves superior impact resistance compared to biodegradable compositions for hunting cartridges and wads known in the prior art. Impact resistance is crucial for proper ballistics, as the wad must withstand very high pressure at the moment of firing. This greater impact resistance is achieved primarily due to the high percentage (>51%) of biodegradable polyesters and the lower, or even negligible, starch or plasticized starch content (<49%). Table 1 shows how impact resistance decreases with the incorporation of a higher percentage of starch, as is common practice in the prior art.

[0074] Table 1 - Impact

[0075] Impact resistance is also influenced by the fact that PBS has lower impact resistance at 23°C and in cold conditions than PBAT. Therefore, the thermoplastic composition according to the invention with >51% PBAT has greater impact resistance than prior art compositions containing a maximum of 50% PBAT, especially at -10°C. This provides significant advantages in ballistics for hunting and sport shooting in geographically cold areas (such as the USA or Northern Europe).

[0076] Table 2 demonstrates this with examples:

[0077] Table 2 - Impact resistance

[0078] Example 3 - Fluency

[0079] The thermoplastic composition according to the invention achieves greater fluidity compared to biodegradable compositions for hunting cartridges and wads known in the prior art. This greater fluidity is achieved through the use of high-flow polyesters (MVR >1, preferably MVR >10, and more preferably MVR >20 and more preferably MVR >40), which allows the wads or cartridge components to be injected at a lower temperature, thus reducing the cooling time and consequently the injection cycle time, thereby increasing production and lowering its cost.

[0080] Table 3 shows examples of how flowability decreases, and therefore viscosity increases, when starch is incorporated, and how a biopolyester (in the examples, PBAT) with high MVR (high flowability, low viscosity) increases the flowability of the final product: Table 3 - Flowability Table 4 shows how replacing a PBAT with an MVR of 3-5 with one with an MVR of 20 increases the fluency of the final product:

[0081] Table 4 - Flow

[0082] Table 5 shows the increased flowability of compositions with biodegradable polyester type PBTSeb with an MVR of 20 cc / 10min measured at 190°C / 2.19Kg and how the greater flowability of the composition does not influence the mechanical properties: Table 5 - Flowability and mechanical properties

[0083] Example 4 - Moisture absorption

[0084] The thermoplastic composition according to the invention also achieves lower moisture absorption compared to biodegradable compositions for hunting cartridges and wads known in the prior art, thanks to the incorporation of polyesters at a concentration > 51%. Table 6 shows this lower moisture absorption achieved:

[0085] Table 6 - Moisture absorption It is observed that the starch-free product absorbs significantly less moisture than the starch-containing product. It is also observed that the starch-containing product, containing >50% PBAT, experiences a stabilization of absorbed moisture at around 2.2-2.5%, values ​​that do not pose a risk to the cartridge's ballistics.

[0086] As we have already discussed, lower moisture absorption brings additional advantages such as greater dimensional stability, greater stability of properties such as impact, modulus and resistance, and greater compatibility with all types of shot, since the presence of moisture in the material can cause chemical and redox reactions between the material and the shot, especially with lead and steel shot, which are the most commonly used in the current state of the art.

[0087] Tables 7 and 8 show a comparison of the moisture absorption of a thermoplastic composition according to the invention and a conventional PVA-based material. The thermoplastic composition according to the invention exhibits lower moisture absorption and greater impact resistance. For the material containing 75% PVA, the modulus and strength decrease when it absorbs 10% moisture to values ​​that could cause ballistic problems, while the thermoplastic composition according to the invention maintains its values.

[0088] Table 7 - Moisture absorption after injection Table 8 - Moisture absorption after 10 days at 60% RH / 23°C

[0089] Example 5 - Dimensional stability tests

[0090] Table 9 shows data on the dimensions of freshly injected blocks made with the thermoplastic composition according to the invention and after conditioning at 23°C and 60%RH, compared to conventional PE blocks. It can be seen that the blocks manufactured with the thermoplastic composition according to the invention absorb less moisture and change their dimensions less after conditioning:

[0091] Table 9 - Dimensional stability redox between the material and the

[0092] We have observed that the presence of moisture in the material can cause chemical and redox reactions between the material used and the shot. Figure 3 shows photographs of different materials after being in contact with steel, lead, and copper shot for 7 days at 90% relative humidity and 50°C. These materials are:

[0093] - polyethylene (5), which is the standard material in the non-biodegradable hunting cartridge market,

[0094] - a material with high moisture absorption due to PVA with a composition of 75% PVA + 25% Plasticizer (8),

[0095] - a thermoplastic composition according to the invention containing 81% PBAT + 6% PLA + 13% inorganic filler (6),

[0096] - a thermoplastic composition according to the invention containing 30% PVA + 8% Plasticizer + 62% PBAT (7) and

[0097] - a thermoplastic composition according to the invention containing 72% PBAT + 3% PLA + 25% TPS (9)

[0098] These photos show that:

[0099] - There is no reaction with the polyethylene composition pellets (5) nor with the thermoplastic composition according to the invention containing 81% PBAT + 6% PLA + 13% inorganic filler (6).

[0100] There is very little reaction with the thermoplastic composition according to the invention containing 72% PBAT + 3% PLA + 25% TPS (9), since, although it contains TPS, which is very hygroscopic, the >50% PBAT content results in hardly any reaction with the pellets. There is also very little reaction with the thermoplastic composition according to the invention containing 30% PVA + 8% Plasticizer + 62% PBAT (7), since, although it contains PVA, which is very hygroscopic, the >50% PBAT content results in hardly any reaction with the pellets.

[0101] - A strong reaction is observed with the material composed of 75% PVA + 25% plasticizer (8), due to its high percentage of PVA, which is very hygroscopic. Example 7 - Ballistics: firing pressure

[0102] The thermoplastic composition according to the invention achieves cartridges that produce lower pressures in the weapon at the moment of firing, lower than those achieved with biodegradable compositions for hunting cartridges, and for wads, known in the state of the art and with conventional cartridges.

[0103] Table 10 compares wads made with known prior art technologies, such as PE, with wads made of a material according to the thermoplastic composition of the invention, under the same conditions: 12 gauge, 1.8g of A0 gunpowder, and 32g of steel shot. The pressures generated are lower with the wads made of the thermoplastic composition of the invention, thus achieving greater safety, and the velocities reached are similar to the standard for polyethylene wads.

[0104] In Table 10, the first value corresponds to material with a composition according to the invention, and the second to a composition known in the prior art:

[0105] Table 10 - Comparative pressure on the weapon

[0106] Table 11 shows ballistic results obtained with wads according to the thermoplastic composition of the invention 72%PBAT (MVR:3-5) + 3%PLA + 25% TPS, with two different cartridge types:

[0107] Table 11 - Firing Tests Being:

[0108] V1* (m / s) - Typical speed with conventional PE cleats

[0109] P max (bar): Maximum permissible pressure. We see in Table 11 how the pressures obtained with the plugs according to the thermoplastic composition of the invention are lower than the maximum permissible pressures (<1030 bar), and the velocities are similar to those obtained with polyethylene plugs: >395 m / s or >400 m / s depending on whether the shot is lead or steel. A person skilled in the art will readily understand that it is possible to combine characteristics of different embodiments with characteristics of other possible embodiments, provided that such a combination is technically feasible.

[0110] All information relating to examples or modes of embodiment forms part of the description of the invention.

Claims

- Injection-moldable and soil-biodegradable thermoplastic composition, suitable for use in ammunition, characterized in that it comprises one or more polyesters 5 biodegradable materials, chosen from the group consisting of PBAT, PBTSeb, PHB, PHA, Polycaprolactone, PLA, with a melt flow rate (MVR) greater than or equal to 10cc / 10min measured at 190 ° C / 2.16Kg, MVR being the melt volume rate, in a proportion greater than or equal to 51% by weight with respect to the total, the composition being biodegradable in soil according to the EN17033 standard. 10 2 - Injection-moldable and soil-biodegradable thermoplastic composition, according to any of the preceding claims, characterized in that the biodegradable polyesters contain bio-based monomers. 15 3 — Injection-moldable and soil-biodegradable thermoplastic composition, according to any of the preceding claims, characterized in that the biodegradable polyesters have an MVR greater than or equal to 20cc / 10min, measured at 190 e C / 2.16Kg. 4— Injection-molded thermoplastic composition that is biodegradable in soil, according to 20 any of the above claims, characterized in that it comprises plasticized starch in a proportion less than or equal to 49% by weight with respect to the total. 5 - Injection-moldable and soil-biodegradable thermoplastic composition according to claim 4, characterized in that the plasticized starch comprises one or more vapors 25 starches originating from the group consisting of corn, potato, pea, tapioca, cassava and biomasses containing starch. 6 - Injection-moldable and soil-biodegradable thermoplastic composition according to claim 5, characterized in that the starch or starches are selected from the group 30 made up of native starches, modified starches and starch derivatives. 7 - Injection-moldable and soil-biodegradable thermoplastic composition, according to any of the preceding claims 4 to 6, characterized in that the plasticized starch comprises one or more plasticizers selected from the group consisting of water, 35 polyhydric alcohols, ethers, thioethers, the esters thereof, or a combination of them, and any other compound or polymer capable of transforming starch into thermoplastic starch. 8 - Injection-molded thermoplastic composition that is biodegradable in soil, according to 5 any of the preceding claims, characterized in that it comprises other components selected from the group consisting of PVA (polyvinyl alcohol), PPG (polypropylene carbonate), PGA (polyglycolic acid), cellulose, modified cellulose, fibers, colorants, impact modifiers, organic and inorganic fillers, thermal stabilizers, hydrolysis stabilizers, UV stabilizers, lubricants, enzymes, accelerating additives of 10 Biodegradability, other additives and other biodegradable polymers. 9 - Ammunition for hunting and sport shooting characterized by comprising one or more injection-molded elements with a composition as described in the preceding claims. 15 10— Ammunition for hunting and sport shooting, according to claim 9, characterized in that the injection-molded elements are parts of a shotgun cartridge. 11 - Ammunition for hunting and sport shooting, according to claim 10, characterized in that 20. The wad is one part of a shotgun cartridge. [0001] [0002] Explanation of the changes in the claims, a change that is presented under Article 19 PCT. [0003]In claim 1, part of the list of biodegradable polyesters that previously appeared in claim 2 has been incorporated, and the reference to the melt flow rate (MVR) greater than or equal to 10cc / 10min measured at 190 has been modified. ° C / 2.16Kg (taking it from the previous claim 4, previously in this Claim 1 it was indicated 1cc / 10 min) and reference to the EN17033 standard has been incorporated, referred to throughout the description. [0004]Original claims 2 and 4 are deleted and the remainder is renumbered.

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