Biodegradable wad for shotgun cartridges

Abstract

The present invention refers to a container wad suitable for shotgun cartridges comprising a biodegradable formulation, wherein said formulation comprises (i) a biodegradable polymer selected from a polybutylene succinate (PBS) copolymer in an amount of at least 70% by weight relative to the total weight of the formulation and (ii) a stearate salt in an amount of between 0.01 and 5% by weight relative to the total weight of the formulation. The invention further relates to a method for the manufacturing of a wad comprising said formulation and the use thereof.

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of shotgun cartridges for hunting and competition and elements thereof, and more particularly to wads, e. g., container wads, based on a biodegradable composition, manufacturing methods and uses thereof.BACKGROUND OF THE INVENTION

[0002] The use of non-biodegradable plastics presents important environmental contamination problems. In particular, in the field of hunting, after a shotgun is fired ammunition components such as wads are expelled at a substantial distance preventing their facile recovery and thus the spent wad remains abandoned leading to pollution of the soil at the area. Wads are typically made of plastic materials which do not biodegrade. Currently, the most used plastic is linear low density polyethylene (LLDPE) which may take a long time to disappear from the environment.

[0003] Various biodegradable materials have been proposed to address this issue.

[0004] Patent application WO 2015 / 033081 A1 describes hunting ammunition comprising a biodegradable thermoplastic composition with a mixture of two polyesters, namely polyalkylene succinate and polyhydroxyalkanoate, preferably along with plant fibers to facilitate breaking and degradation of polyester macromolecules.

[0005] Patent application EP 3290858 A1 discloses a shotgun cartridge manufactured from a bioplastic comprised of (i) biodegradable polymers of vegetable origin and (ii) an inert and non-toxic mineral filler. The application only includes an example, which is disclosed as preferred embodiment, and relates to a material for shotgun cartridges comprising 60% of polylactic acid (PLA), plus 39% of a biodegradable elastomeric polymer and 1% of a calcium carbonate mineral filler.

[0006] However, although several alternatives have been proposed, the materials used are either difficult to process by injection-moulding or lack the mechanical quality required to withstand extreme temperature and pressure conditions when the ammunition is fired.

[0007] Therefore, there is an ongoing need in the art to provide biodegradable ammunition components, and in particular wads such as container wads, which reach a good balance in terms of processability for ease of manufacture and at the same time meet the technical specifications for use in shotgun cartridges.BRIEF DESCRIPTION OF THE INVENTION

[0008] The authors of the present invention have surprisingly found that a biodegradable formulation, comprising a polybutylene succinate (PBS) copolymer, such as polybutylene succinate adipate (PBSA), and a filler based on a stearate salt, exhibit an improved processability for injection-moulding. Furthermore, said formulation is suitable to provide elements of shotgun cartridges for hunting and shooting sports, particularly wads, with adequate mechanical properties.

[0009] Accordingly, in a first aspect, the present invention relates to a wad for shotgun cartridges comprising a biodegradable formulation, wherein said formulation comprises: i) a biodegradable polymer selected from a polybutylene succinate (PBS) copolymer in an amount of at least 70% by weight relative to the total weight of the formulation; and ii) a stearate salt in an amount of between 0.01 and 5% by weight relative to the total weight of the formulation.

[0010] In a second aspect, the invention relates to a cartridge comprising a wad as defined in the first aspect.

[0011] In a third aspect, the invention further relates to a process for manufacturing a wad as defined in the first aspect comprising the steps of: a) providing a biodegradable polymer selected from a polybutylene succinate (PBS) copolymer and a stearate salt; b) mixing and heating the PBS copolymer and the stearate salt of step (a) to obtain a biodegradable formulation; and c) forming a wad from the biodegradable formulation of step (b) by injection-moulding.

[0012] In a fourth aspect, the invention relates to the use of a biodegradable formulation as defined in the first aspect in the manufacture of shotgun cartridges, and more particularly, in the manufacture of wads for shotgun cartridges.

[0013] These aspects and preferred embodiments thereof are additionally defined hereinafter in the detailed description and in the claims.

[0014] All the features described in this specification (including the claims, description and drawings) can be combined in any combination, with the exception of combinations of such mutually exclusive features.BRIEF DESCRIPTION OF THE FIGURES

[0015] To better understand the invention, its objects and advantages, the following figures are attached to the specification in which the following is depicted: Figure 1. Design of a typical container wad for shotgun cartridges. Figure 2. Images showing the general aspect of formulation H container wads (base thickness of 4 mm and 4.5 mm, respectively) after being fired. Figure 3. Images showing the general aspect of formulation I container wads (base thickness of 4 mm and 4.5 mm, respectively) after being fired. Figure 4. Images showing the general aspect of container wads of formulations J (a), K (b) and L (c) after being fired. Figure 5. Graph showing length measurements for formulation J container wad under different climatic exposure scenarios. Figure 6. Graph showing diameter measurements for formulation J container wad under different climatic exposure scenarios. Figure 7. Graph showing the disintegration of formulation J container wads (a, b) and petals thereof (c, d) over time. DETAILED DESCRIPTION OF THE INVENTION

[0016] Unless defined otherwise, all technical and scientific terms and expressions used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs.Wad for shotgun cartridges

[0017] A first aspect of the present invention is directed to a wad suitable for shotgun cartridges comprising or consisting of a biodegradable formulation, wherein said formulation comprises or consists of: i) a biodegradable polymer selected from a polybutylene succinate (PBS) copolymer in an amount of at least 70% by weight relative to the total weight of the formulation; and ii) a stearate salt in an amount of between 0.01 and 5% by weight relative to the total weight of the formulation.

[0018] As used herein and as is well understood in the art, the term "shotgun cartridge" or simply "cartridge" refers to the standard type of ammunition for a shotgun. It is fired after being loaded into the chamber or chambers of a shotgun. A shotgun cartridge is typically cylindrical in shape and has several parts, namely, shot (pellet-like spherical sub-projectiles), powder (it is the propellant, generating gases which produce the pressure to be transformed into impulse), and a container wad contained inside a case (or hull). The case is the external part of the cartridge basically composed of a tube (contains the shots with the wad and powder), head (metallic and more resistant part of the cartridge which mainly contains the seat of the primer and allows the cartridge housing at the base of the chamber and its extraction after firing), a base wad (element that holds the tube and the head) and the primer (responsible for initiating the powder combustion that will propel the projectiles out of the gun barrel).

[0019] The term "wad" may generally refer to a container wad and / or a base wad. As used herein and as is known in the art, the term "container wad" is meant to include a component of a shotgun cartridge used to contain the shotgun shot, separate the shot from the powder, and provide a seal that prevents gas from blowing through the shot rather than propelling the shot out of the shotgun, or a component which only provides a gas sealing function (the latter also referred to sometimes as "obturator wad"). As used herein and as is known in the art, the term "base wad" refers to an element of the case that holds the tube and the head.

[0020] The wad in the present invention may be both a container wad (including an obturator wad) and a base wad. In preferred embodiments, the wad of the present invention is a container wad.

[0021] The term "biodegradable" is known in the art and refers to polymers, compositions and formulations, such as those described herein, that are intended to degrade upon exposure to environmental conditions. The degradation of plastic products comprises a first stage involving the disintegration of the material into small particles, which can be produced by the action of the sun, water, oxidation, microorganisms or heat. In the case of compostable materials a second stage takes place within a few months (rather than decades or even centuries, as in the case of other materials) wherein the fragments of the material are converted into volatile materials, primarily in CO 2 , water and biomass due to the action of microorganisms.

[0022] In a preferred embodiment, the PBS copolymer and / or any other polymer comprised in the formulation of the present invention biodegrade up to 90% by weight within six months (i.e., 90% of their mass by weight is transformed into carbon dioxide, water and biomass within 180 days) in accordance with ISO standard UNE-EN ISO 14855.

[0023] The biodegradable formulation of the present invention comprises a PBS copolymer in an amount of at least 70% by weight relative to the total weight of the formulation. In a particular embodiment, the formulation comprises an amount of at least 71%, at least 72%, at least 73%, at least 74%, at least 75%, at least 76%, at least 77%, at least 78%, at least 79%, at least 80%, at least 81%, at least 82%, at least 83%, at least 84%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, at least 99.1 %, at least 99.2%, at least 99.3%, at least 99.4%, at least 99.5%, at least 99.6%, at least 99.7%, at least 99.8%, at least 99.9%, or at least 99.99%, by weight of a PBS copolymer relative to the total weight of the formulation.

[0024] Polybutylene succinate (PBS) and its copolymers are a family of biodegradable polymers with thermoplastic processability. A "thermoplastic" is a polymer that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. PBS may be synthesized via polycondensation of succinic acid and 1,4-butanediol. The term "polybutylene succinate copolymer" or "PBS copolymer" refers to polymers obtained by random copolymerization of PBS with other dicarboxylic acids or diols, including for example adipic acid, terephthalic acid, methyl succinic acid, 2,2-dimetyl succinic acid, benzyl succinic acid, ethylene glycol or 1,3-propanediol.

[0025] In a particular embodiment, the PBS copolymer is selected from the group consisting of polybutylene succinate-co-adipate (PBSA), polybutylene succinate-co-lactate (PBSL), polybutylene succinate-co-ε-caprolactone (PBS-co-CL), polybutylene succinate-co-carbonate (PBSC), polybutylene succinate-co-terephthalate (PBST), polybutylene succinate-co-diethylene glycol succinate (PBS-co-DEGS) and polybutylene succinate-co-furandicarboxylate (PBSF) and combinations thereof.

[0026] In a preferred embodiment, the PBS copolymer is a polybutylene succinate adipate copolymer (PBSA).

[0027] In a particular embodiment, the PBS copolymer, such as PBSA, has a melt flow rate (at 190 °C, 2.16 kg) between about 3.5 and 25 g / 10 min, as may be determined according to method ISO 1133 UNE EN ISO 1133-1:2023. A melt flow test measures the melt flow rate (MFR) and melt volume rate (MVR) of a molten polymer. Values are taken at a certain temperature and with a certain mass applied, dependent on material.

[0028] In a particular embodiment, the PBS copolymer, such as PBSA, has a tensile strength at break between about 10 and 50 MPa, preferably between about 20 and 40 MPa. The tensile strength at break may be measured according to UNE EN ISO 527-2:2012. Tensile strength (TS) at break is a measurement of the maximum stress a material can withstand while being stretched before breaking.

[0029] In a particular embodiment, the PBS copolymer, such as PBSA, has a deformation at break between about 350 and 700%, preferably between about 400 and 650%. Deformation at break may be determined according to UNE EN ISO 527-2:2012. Deformation at break is a measurement of the deformation capacity of a material before reaching its breaking point.

[0030] The biodegradable formulation of the present invention comprises an amount of between 0.01 and 5% by weight of a stearate salt relative to the total weight of the formulation. The stearate salt acts as a filler.

[0031] The authors of the present invention have found that selecting a stearate salt filler in combination with a PBS copolymer results in an unexpectedly improved processability of the formulation, particularly for injection moulding thereof.

[0032] In a particular embodiment, the stearate salt is a metal stearate salt, preferably selected from the group consisting of calcium stearate, magnesium stearate, zinc stearate, aluminum stearate, sodium stearate and combinations thereof. Preferably, the stearate salt is calcium stearate.

[0033] In a particular embodiment, the stearate salt is in an amount between 0.05 and 4% by weight relative to the total weight of the formulation, more particularly between 0.1 and 3%, between 0.1 and 2%, between 0.1 and 1% or between 0.1 and 0.5%. In a more particular embodiment, the stearate salt is in an amount of between 0.2 and 0.3% by weight relative to the total weight of the formulation.

[0034] In a particular embodiment, the stearate salt is in an amount of less than about 4%, less than about 3%, less than about 2%, less than about 1 %, less than about 0.5%, by weight relative to the total weight of the formulation.

[0035] In some embodiments, other biodegradable polymers may also be incorporated into the biodegradable formulation. However, the main (most abundant) polymer of the formulation according to the present invention is a PBS copolymer.

[0036] Non-limiting examples of further biodegradable polymers include polyesters such as poly(lactic acid) or polylactide (PLA), poly(butylene adipate-co-terephthalate) (PBAT), polyhydroxyalkanoate (PHA), polycaprolactones such as poly(£-caprolactone) (PCL), polyanhydrides, poly(ortho-esters), or poly(ester amides).

[0037] In a particular embodiment, the formulation comprises at least a second biodegradable polymer. In a more particular embodiment, the formulation comprises at least a second biodegradable polymer selected from the group of biodegradable polyesters (preferably selected from the group consisting of polylactic acid (PLA), poly(butylene adipate-co-terephthalate) (PBAT), polyhydroxyalkanoates (PHAs), polycaprolactone (PCL)) and polyvinyl alcohol (PVOH) and combinations thereof. In a preferred embodiment, the at least a second biodegradable polymer is selected from polylactic acid, poly(butylene adipate-co-terephthalate) and combinations thereof.

[0038] In a more preferred embodiment, the at least a second biodegradable polymer is a mixture of polylactic acid and poly(butylene adipate-co-terephthalate) in a weight ratio of 5:1 to 1:5, preferably in a weight ratio of 2:1 to 1:2, more preferably in a weight ratio of about 1:1 to 1:1.5.

[0039] In a particular embodiment, the at least a second biodegradable polymer is in an amount between 0.1 and 29.99% by weight relative to the total weight of the formulation, more particularly between 1 and 25%, between 1 and 20%, or between 5 and 20%. In a more particular embodiment, the at least a second biodegradable polymer is in an amount between 6 and 20% or between 8 and 19% by weight relative to the total weight of the formulation. In a more particular embodiment, the at least a second biodegradable polymer is in an amount between 11 and 18% by weight relative to the total weight of the formulation.

[0040] In a particular embodiment, the at least a second biodegradable polymer is in an amount of less than about 25%, less than about 20%, less than about 15%, less than about 10%, less than about 5%, less than about 4%, less than about 3%, less than about 2%, or less than about 1% by weight relative to the total weight of the formulation.

[0041] The disclosed amounts of second biodegradable polymer, when it is a combination of polymers, refer to the total amount of such polymers.

[0042] In a particular embodiment, the biodegradable formulation of the present invention may comprise other additives commonly used in the art such as compatibilizers, coupling agents, viscosity modifiers and / or plasticizers.

[0043] As used herein, the term "compatibilizer" refers to a polymer that, when added to an immiscible or partially miscible polymer blend, can increase the miscibility of the polymers resulting in an increased stability in the blend. Thus, when the biodegradable formulation comprises different PBS copolymers or a combination of PBS copolymer(s) and at least a second biodegradable polymer, it may be useful to include a compatibilizer.

[0044] In a particular embodiment, the biodegradable formulation comprises a compatibilizer, preferably selected from the group consisting of polyvinyl acetate copolymers, polycaprolactone, polyesters, methacrylate-terminated reactive polystyrene, polycaprolactone / poly(tetramethylene glycol) block polyols, methacrylate-based polymers, block and grafted polymers or combinations thereof. Preferably, the compatibilizer is a polyvinyl acetate copolymer. More preferably, the compatibilizer is a polyvinyl acetate-vinyl laurate copolymer, such as those commercialized under the trademark Vinnex ®< by Wacker Chemie AG.

[0045] In a particular embodiment, the compatibilizer is in an amount between 0.1 and 29.99% by weight relative to the total weight of the formulation, more particularly between 1 and 25%, between 1 and 20%, between 1 and 15% or between 5 and 15%. In a more particular embodiment, the compatibilizer is in an amount between 6 and 14% or between 7 and 13% or between 8 and 12% or between 9 and 11% by weight relative to the total weight of the formulation. In a more particular embodiment, the compatibilizer is in an amount of about 10% by weight relative to the total weight of the formulation.

[0046] In a particular embodiment, the compatibilizer is in an amount of less than about 25%, less than about 20%, less than about 15%, less than about 10%, less than about 5%, less than about 4%, less than about 3%, less than about 2%, or less than about 1% by weight relative to the total weight of the formulation.

[0047] In a particular embodiment, the sum of the amounts of all the polymers comprised in the formulation (i.e. PBS copolymer and if present the at least a second biodegradable polymer and any additive such as a compatibilizer) represents at least 71 %, at least 72%, at least 73%, at least 74%, at least 75%, at least 76%, at least 77%, at least 78%, at least 79%, at least 80%, at least 81%, at least 82%, at least 83%, at least 84%, at least 85%, at least 86%, at least 87%, at least 88%, at least 89%, at least 90%, at least 91%, at least 92%, at least 93%, at least 94%, at least 95%, at least 96%, at least 97%, at least 98%, at least 99%, at least 99.1%, at least 99.2%, at least 99.3%, at least 99.4%, at least 99.5%, at least 99.6%, at least 99.7%, at least 99.8%, at least 99.9%, or at least 99.99%, by weight relative to the total weight of the formulation. In a particular embodiment, the sum of the amounts of all the polymers comprised in the formulation represents at least 80%, at least 85%, or at least 90%, by weight relative to the total weight of the formulation.

[0048] In a particular embodiment, the biodegradable formulation comprises or consists of: i) a biodegradable polymer selected from a PBS copolymer (e.g. PBSA) in an amount of between 95 and 99.99%, and ii) a stearate salt (e.g. calcium stearate) in an amount of between 0.01 and 5% by weight; wherein the percentages by weight are relative to the total weight of the formulation.

[0049] In a particular embodiment, the biodegradable formulation comprises or consists of: i) a biodegradable polymer selected from a PBS copolymer (e.g. PBSA) in an amount of between 99 and 99.9%, and ii) a stearate salt (e.g. calcium stearate) in an amount of between 0.1 and 1% by weight; wherein the percentages by weight are relative to the total weight of the formulation.

[0050] In a particular embodiment, the biodegradable formulation comprises or consists of: i) a biodegradable polymer selected from a PBS copolymer (e.g. PBSA) in an amount of at least 70% by weight; ii) a stearate salt (e.g. calcium stearate) in an amount of between 0.01 and 5% by weight; iii) at least a second biodegradable polymer (e.g. polylactic acid, poly(butylene adipate-co-terephthalate or a combination thereof) in an amount of between 0.1 and 29.99% by weight; and iv) optionally, a compatibilizer (e.g. polyvinyl acetate-vinyl laurate copolymer) in an amount of between 0.1 and 29.99% by weight; and wherein the percentages by weight are relative to the total weight of the formulation.

[0051] In a particular embodiment, the biodegradable formulation comprises or consists of: i) a biodegradable polymer selected from a PBS copolymer (e.g. PBSA) in an amount of at least 70% by weight; ii) a stearate salt (e.g. calcium stearate) in an amount of between 0.1 and 1% by weight; iii) at least a second biodegradable polymer (e.g. polylactic acid, poly(butylene adipate-co-terephthalate or a combination thereof) in an amount of between 5 and 20% by weight; and iv) optionally, a compatibilizer (e.g. polyvinyl acetate-vinyl laurate copolymer) in an amount of between 5 and 15% by weight; and wherein the percentages by weight are relative to the total weight of the formulation.

[0052] Exemplary biodegradable formulations include: Formulations (H), (I) and (J) which comprise about 99.775% PBSA and about 0.225% calcium stearate; Formulation (K) which comprises about 72.475% PBSA, about 5.85% PLA, about 5.85% PBAT, additives comprising about 10% polyvinyl acetate-vinyl laurate copolymer, and 0.225% calcium stearate; and Formulation (L) which comprises about 72.475% PBSA, about 7.02% PLA, about 10.53% PBAT, additives comprising about 10% polyvinyl acetate-vinyl laurate copolymer, and 0.225% calcium stearate; wherein the percentages are percentages by weight relative to the total weight of the formulation.

[0053] In a particular embodiment, the wad of the present invention is a container wad having a shot cup and a sealing base. In a particular embodiment, the container wad can have pre-cut petals. In a particular embodiment, the container wad has a shot cup, a sealing base and pre-cut petals. Referring to Fig. 1, the shot cup and the sealing base correspond respectively with the cylindrical sidewall (2) and the base (3) and define a space (1). Petals (not represented in Fig. 1) are an element of the container wad provided by axial cuts, slits or slots in the shot cup designed to flare open upon firing.

[0054] In a more particular embodiment, the sealing base of the container wad has a thickness between about 3.0 and 5.0 mm, preferably between about 3.5 and 4.5 mm or between about 4.0 and 4.5 mm.

[0055] The authors of the present invention have surprisingly found that a wad with a formulation according to the present invention does not undergo significant dimensional changes with the humidity and temperature of the environment. This is of special importance in the handling and storage stage of the wad since a significant change in dimensions could cause serious problems when assembling the cartridge, generating a defective product.

[0056] In a particular embodiment, the wad has a dimensional variation in length and / or diameter of less than about 1%, preferably less than about 0.8%, more preferably less than about 0.6%, even more preferably less than about 0.5% relative to the corresponding initial dimension (i.e. length or diameter), under conditions of temperature between -20 and 50 °C and / or relative humidities (RH) of up to 95% after exposure times of at least 24 h, at least 48 h, at least 72 h, at least 96 h, at least 100 h. In a particular embodiment, the wad has a dimensional variation in length and / or diameter of less than about 1%, preferably less than about 0.8%, more preferably less than about 0.6%, even more preferably less than about 0.5% relative to the corresponding initial dimension under a sequence of steps comprising conditioning, humid heat, cold, humid heat, extreme cold, cold and conditioning, as summarized below: Conditioning: 20-25 °C, about 50% RH; Humid heat: 30-40 °C, about 85 to 95% RH; Cold: -5 to 5 °C, atmospheric RH, Extreme cold: about -10 °C, atmospheric RH, wherein the conditions of each step are maintained for a period between 24 and 96 h.

[0057] The dimensional variation can be determined applying the following equations: Δ ε l ength = 100 lt − li / li Δ ε diameter = 100 d t − d i / d i wherein l t , d t represent the length and diameter, respectively, at the measurement time point, and l i , d i represent the initial length and diameter, respectively.

[0058] Advantageously, the wads according to the present invention exhibit both mechanical properties sufficient to withstand extreme conditions of temperature and pressure when firing the ammunition and good biodegradability.

[0059] The container wads of the present invention may comply with one or more biodegradability standards.

[0060] In a particular embodiment, the wad undergoes degradation by biological processes during composting to yield carbon dioxide, water, inorganic compounds, and biomass at a rate consistent with other known compostable materials.

[0061] In some embodiments, biodegradability of the wad can be defined according to compliance with international standards.

[0062] Some standards commonly used in determining the biodegradability and / or compostability of plastic materials are the following: UNE EN ISO 17556 (Plastics - Determination of the ultimate aerobic biodegradability of plastic materials in soil by measuring the oxygen demand in a respirometer or the amount of carbon dioxide evolved); UNE-EN 14046 (Packaging - Evaluation of the ultimate aerobic biodegradability of packaging materials under controlled composting conditions - Method by analysis of released carbon dioxide) or ASTM D 5988 (Standard test method for determining aerobic biodegradation in soil of plastic materials or residual plastic materials after composting).

[0063] In a particular embodiment, the wad is biodegradable in accordance with the UNE EN ISO 17556 standard. In another particular embodiment, the wad is biodegradable in accordance with the UNE-EN 14046 standard. In a further particular embodiment, the wad is biodegradable in accordance with the ASTM D 5988 standard test method. In an embodiment, the wad is compostable in accordance with the UNE-EN 13432 standard because there exist: ▪ CO 2 formation under the action of microorganisms in 6 months, ▪ 90% decomposition in aerobic medium, and ▪ 50% decomposition in anaerobic medium. Cartridge

[0064] The invention further refers, in another aspect, to a cartridge comprising the wad as defined in the first aspect in any of its particular and preferred embodiments. Preferably, the cartridge is suitable for hunting and competition or shooting sports such as sporting clay shooting.Process for manufacturing

[0065] In another aspect, the invention relates to a process for manufacturing the wad of the invention comprising the steps of: a) providing a biodegradable polymer selected from a polybutylene succinate (PBS) copolymer and a stearate salt (and optionally at least a second biodegradable polymer and / or other additives commonly used in the art such as compatibilizers, coupling agents, viscosity modifiers and / or plasticizers); b) mixing and heating all components of step (a) to obtain a biodegradable formulation; and c) forming a wad from the biodegradable formulation of step (b) by injection moulding.

[0066] The wad of the present invention may be manufactured by injection moulding, which is a well-known manufacturing process for producing parts by injecting molten material into a mould. Briefly, material for the part is fed into a heated barrel, mixed, and injected into a mould cavity, where it cools and hardens adopting the geometry of the cavity.

[0067] In the process of the invention, the injection-moulded wad and / or the biodegradable formulation may have any of the features described above for the first aspect.

[0068] In a particular embodiment, the PBS copolymer of step a) may be provided in pelletized or powder form.

[0069] In a particular embodiment, the stearate salt, i.e. the filler, is provided in powder form. In a preferred embodiment, the stearate salt filler is provided blended with a biodegradable polymer carrier. The authors have observed that providing the stearate salt blended with a carrier may improve its handling and ensure a more homogeneous mixture.

[0070] In a particular embodiment, the stearate salt and the polymer carrier are blended in a weight ratio of 1:20 to 10:1, particularly 1:15 to 1:1, more particularly 1:12 to 1:5, even more particularly 1:10 to 1:8. In a preferred embodiment, the stearate salt and the polymer carrier are blended in a weight ratio of about 1:9.

[0071] In a particular embodiment, the carrier is a PBS copolymer. Particular and preferred embodiments for PBS copolymers are described above in the first aspect. The PBS copolymer used as polymer carrier for the stearate salt filler may be the same or different from the PBS copolymer provided in step a). Preferably, the PBS copolymer carrier is PBSA. More preferably, the PBS copolymer (e.g. PBSA) carrier for the stearate salt filler is the same as the PBS copolymer (e.g. PBSA) provided in step a). For the avoidance of doubt, when the stearate salt filler is provided in a PBS copolymer carrier, the values disclosed herein for the amount of PBS copolymer in the final biodegradable formulation correspond to the total amount of PBS copolymer, i.e. including both the main PBS copolymer and the PBS copolymer acting as carrier for the stearate salt filler.

[0072] In addition to providing a biodegradable polymer selected from a polybutylene succinate (PBS) copolymer and a stearate salt, step a) may further comprise providing at least a second biodegradable polymer and / or other additives commonly used in the art such as compatibilizers, coupling agents, viscosity modifiers and / or plasticizers In a particular embodiment, at least a second biodegradable polymer is provided in step a), preferably in pelletized or powder form. Particular and preferred embodiments for the at least a second biodegradable polymer are those as defined above in the first aspect.

[0073] In a particular embodiment, one or more additives such as compatibilizers, coupling agents, viscosity modifiers and / or plasticizers is / are provided in step a). In a preferred embodiment, a compatibilizer is provided in step a). Particular and preferred compatibilizers are those as defined above the first aspect.

[0074] All components of step a) may be fed into a continuous operation mixer such as the barrel of an injection-moulding machine, fitted with a screw. In a particular embodiment, the mixing speed, i. e., controlled rotation of the mixing screw, is in a range of about 50 to 500 rpm, preferably about 100 to 300 rpm.

[0075] Heat is also required in step b) of the process to melt and mix the polymer(s) and the filler together.

[0076] The heating of step b) is performed at a temperature sufficient to obtain a melt. In a particular embodiment, the temperature of step b) is set at a temperature between about 100 and 250 °C and the mixing performed at said temperature. The mixing time may be adjusted depending on the amounts of materials provided in step a). In a particular embodiment, the heating and mixing of step b) is performed for a period of about 3 to 10 min.

[0077] As the skilled person would understand, the exact temperature and time will depend on the particular features of the biodegradable formulation and the amount of material being used. Moreover, as some of the components are heat sensitive it is important not to allow them to degrade due to being heated for too long or allowed to go over a set temperature.

[0078] For step c), a mould may be fitted at the exit of the barrel and the biodegradable formulation obtained in step b) is injected into said mould.

[0079] In a particular embodiment, the injection temperature of the biodegradable formulation in step c) is between about 150 and 250 °C, preferably between about 180 and 210 °C.

[0080] In a particular embodiment, the injection pressure in step c) is between about 60 and 120 bar, preferably between about 80 and 100 bar.

[0081] In some embodiments, an auxiliary gas counterpressure system may be equipped to the injection moulding machine for forcing an inert gas back into the mould to counteract the biodegradable formulation melt being shot into the mould. This counterpressure is useful for ensuring that the injection shot substantially, if not completely, fills the mould cavity and prevents warping and shrinkage of the molded piece.

[0082] In a particular embodiment, a counterpressure between about 1 and 5 bar is applied in step c).

[0083] After injection, the biodegradable formulation forming the wad is allowed to cool and harden. In a particular embodiment, the cooling time is between about 5 and 25 seconds, preferably between about 10 and 20 seconds, preferably the cooling time is about 15 seconds.

[0084] The mould may be a versatile one in order to allow manufacture of different types of wads. For container wads, the mould contemplates lengths ranging from about 30 mm up to 60 mm, preferably between about 35 mm to 50 mm and a diameter between about 15 mm to 20 mm. In a particular embodiment, the container wad has a sealing base at thickness between about 3.0 to 5.0 mm, preferably about 3.5 to 4.5 mm or about 4.0 to 4.5 mm. In a particular embodiment, the container wad obtained by injection process may also have pre-cut petals.Use of a biodegradable formulation

[0085] In a further aspect, the invention relates to the use of a biodegradable formulation as defined in the first aspect in any of its particular embodiments in the manufacture of shotgun cartridges, and more particularly, in the manufacture of wads, e.g. container wads, for shotgun cartridges.

[0086] Terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. For example, as used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items and may be abbreviated as " / ".

[0087] As used herein, the term "approximately" or "about" as applied to one or more values of interest, refers to a value that is similar to a stated reference value. In certain embodiments, the term "approximately" or "about" refers to a value that can vary up to ± 20 %, preferably within ± 10 %, and more preferably within ± 5 % of the stated reference value. When "approximately" or "about" is used before a numerical range, it applies to the upper and lower range end-points.

[0088] Indeed, the skilled person knows that numerical values relating to measurements are subject to measurement errors which place limits on their accuracy. Where terms such as "about" or "approximately" are applied to a particular value (e.g. "about 200 °C" or "approximately 200 °C") or to a range (e.g. "about x to approximately y"), the value or range may be interpreted as being as accurate as the method used to measure it. Unless explicitly stated otherwise, the general convention in the scientific and technical literature may be applied so that the last digit of numerical values preferably indicates the precision of measurement. Thus, unless other error margins are given, the maximum margin is preferably ascertained by applying the rounding-off convention to the last decimal place. For instance, a value of 3.5 preferably has an error margin of 3.45 to 3.54 and a range of 2% to 10% preferably covers a range of 1.5% to 10.4%. Said variations of a specified value are understood by the skilled person and are within the context of the present invention. Further, to provide a more concise description, some of the quantitative expressions given herein are not qualified with the term "about". It is understood that, whether the term "about" is used explicitly or not, every quantity given herein is meant to refer to the actual given value, and it is also meant to refer to the approximation to such given value that would reasonably be inferred based on the ordinary skill in the art, including equivalents and approximations due to the experimental and / or measurement conditions for such given value.

[0089] Concentrations, amounts, and other numerical data may be expressed or presented herein in a range format. It is to be understood that such a range format is used merely for convenience and brevity and thus should be interpreted flexibly to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. As an illustration, a numerical range of "about 1 % to about 5 %" should be interpreted to include not only the explicitly recited values of about 1 % to about 5 %, but also include individual values and sub-ranges within the indicated range. Thus, included in this numerical range are individual values such as 2, 3 and 4 and sub-ranges such as from 1-3, from 2-4, and from 3-5, etc. This same principle applies to ranges reciting only one numerical value. It should also be understood that ranges formed by combination of any of the end points of different disclosed ranges and / or particular values therein are included in the present disclosure.

[0090] It should be understood that the scope of the present disclosure includes all the possible combinations of embodiments disclosed herein.

[0091] Any or all of the above described weight embodiments of the biodegradable formulation may be combined with each other to arrive at new embodiments. It is to be understood that the weight percentages of each component are chosen such that the total percentage does not exceed 100% with respect to the total weight of the biodegradable formulation. In certain embodiments, the weight percentages of each component are chosen such that the total percentage does not reach 100% with respect to the total weight of the biodegradable formulation, such that further components may be present. In other embodiments, the weight percentages of each component are chosen such that the total percentage totals 100% with respect to the total weight of the biodegradable formulation, such that further components are not present, in which case the biodegradable formulation consists of such components.

[0092] Unless otherwise stated, the standardization and certification systems (e.g. UNE, ISO, ASTM, etc.) mentioned herein correspond to the latest version as in force at the priority date of the present patent application.

[0093] The invention will be described by way of the following examples which are to be considered as merely illustrative and not limitative of the scope of the invention.EXAMPLES Materials:- Polymers:

[0094] BioPBS ™< PBSA 1 is bio-based and biodegradable polybutylene succinate adipate (PBSA) produced from polymerization of bio-based succinic acid, 1,4-butanediol and adipic acid by PTT Chemicals. It is suitable for injection molding articles for general purpose. It has a stress at break of 24 MPa, strain at break of 450%, Young modulus of 300 MPa, density of 1.24 g / cm 3< , and MFR (190 °C, 2.16 kg) of 22 g / 10 min.

[0095] BioPBS ™< PBSA 2 is bio-based and biodegradable polybutylene succinate adipate (PBSA) produced from polymerization of bio-based succinic acid, 1,4-butanediol and adipic acid by PTT Chemicals. It is suitable for both blown and cast film extrusion. It has a stress at break in machine direction sample tests of 32 MPa, strain at break of 600%, Young modulus of 289 MPa, density of 1.24 g / cm 3< , and MFR (190 °C, 2.16 kg) of 4 g / 10 min.

[0096] Biobatch 1884 is a bio-based, biodegradable and compostable commercial mixture of PLA and PBAT polymers manufactured by TechnoCompound GmbH. It is suitable for blown and cast film extrusion. It has a stress at break in machine direction sample tests of 48 MPa, strain at break of 380%, density of 1.23 g / cm 3< , and MFR (190 °C, 2.16 kg) of 4.5 g / 10 min.

[0097] INZEA F08 is a flexible, bio-based, biodegradable and compostable polymer based on polyesters similar to Biobatch 1884 produced by Nurel Biopolymers. It is suitable for blown and cast film extrusion. It has a stress at break in machine direction sample tests of 25 MPa, strain at break of 700 - 750 %, Young modulus of 300 MPa, density of 1.31 g / cm 3< , and MFR (190 °C, 2.16 kg) of <7 g / 10 min.- Fillers:

[0098] NCA 1 is a Calcium Stearate filler developed by Unnox Group with PBSA 1 as polymer carrier. The material composition is 91% by weight of PBSA 1 and 9% by weight of Calcium Stearate. This material is prepared by blending PBSA 1 with calcium stearate by melt extrusion, followed by cooling of the blend and mechanical granulation thereof.

[0099] NCA 2 is a Calcium Stearate filler developed by Unnox Group with PBSA 2 as polymer carrier. The material composition is 91% by weight of PBSA 2 and 9% by weight of Calcium Stearate. This material is prepared by blending PBSA 2 with calcium stearate by melt extrusion, followed by cooling of the blend and mechanical granulation thereof.

[0100] Crodamide Slip is Eucaramide powder obtained from CRODA Polymers & Aditives. Crodamide ™< .

[0101] Joncryl 4468 is an epoxy-styrene-acrylic oligomer (ESAO) filler with low epoxy equivalent weight (= low number of epoxy groups per chain) obtained from BASF.

[0102] Joncryl 4400 is an epoxy-styrene-acrylic oligomer (ESAO) with a medium epoxy equivalent weight (= medium number of epoxy groups per chain) obtained from BASF.

[0103] CESA Slip PL8041 is a process lubricant filler for the processing of thermoplastic polymers supplied by Clariant.- Other additives:

[0104] VINNEX ®< 8880 is a compatibilizer additive based on a vinyl acetate / vinyl laurate copolymer and polyvinyl acetate commercialized by Wacker Chemie AG.Example 1 - Compounding of biodegradable formulations

[0105] Polymers were dried prior to use in a dry air dehumidifier PIOVAN model HRM 100 at a temperature of 70 °C for over 5 hours.

[0106] Then, several biodegradable formulations were obtained by mixing and heating the polymer(s), filler(s) and optional additives shown in Table 1 below, and injection moulding the molten biodegradable formulations in a machine ENGEL Victory 650 / 160 spex under the conditions showed in Table 2: Table 2. Injection-moulding parametersBarrel Temp. (°C)Mould Temp. (°C)Injection Pressure (bar)Holding Pressure (bar)Counter Pressure (bar)Injection Time (s)Holding Time (s)Cooling Time (s)19220713540.941020 Example 2. Processability and mechanical properties of biodegradable formulations

[0107] The processability and mechanical properties of the injection-moulded formulations described in Example 1 were evaluated.

[0108] As regards processability, both blank PBSA formulations without filler (A and B) presented demoulding problems and required significantly increasing the demoulding or cooling time, as well as decreasing the mould temperature.

[0109] However, the incorporation of calcium stearate based fillers into the PBSA matrices (formulations H, I, J, K, L) led to a substantial improvement in the processability of the material which could be easily injected, overcoming the demoulding difficulties encountered with the pure PBSA material. By contrast, the addition of Cesa slip (formulation G) or Joncryl (formulations E, F) fillers showed no improvement, whereas all the formulations containing Crodamide slip as filler (formulations C, D) slipped excessively and made the mould injection unfeasible.

[0110] Next, the mechanical properties of the different formulations were evaluated. The formulations according to the present invention, and in particular formulations J, K and L, shown a remarkable behavior regarding the balance in modulus and Yield deformation with respect to pure PBSA material (Table 3). Table 3. Mechanical properties of injection-moulded formulations:FormulationE (MPa)Yield stress (MPa)Yield deform. (%)Tensile strength (MPa)Tensile deformation (%)Blank B333 ± 818.6 ± 0.416 ± 124.6 ± 0,2280 ± 7J283 ± 1717.5 ± 0,318 ± 122.3 ± 1485 ± 75K183 ± 711.7 ± 0.123 ± 118.3 ± 0.3611 ± 22L196 ± 912.5 ± 0.121 ± 120 ± 1721 ± 52 Example 3 - Manufacturing and testing of biodegradable container wads

[0111] Two wad designs based on a Steel 36 g wad from BIO SOFIAM having a space (1) enclosed by a cylindrical sidewall (2) and a base (3) as shown in Figure 1, with and without pre-cut petals were used. The general dimensions of the prototype were 47 mm length, 18.5 mm diameter and a base thickness of 3.0, 4.0 or 4.5 mm.

[0112] Prototype wads were prepared in a mould with the design parameters described above by injection-moulding according to the injection parameters as shown in Table 4 below, using PE DOWLEX 2552E as reference material, and the formulations based on PBSA including a calcium stearate based filler (formulations H, I,J, K and L). A. Shotgun firing tests

[0113] The biodegradable container wad prototypes were validated through shotgun firing tests, to evaluate the behavior of the wad in the presence of flame and smoke in terms of blackening, petal opening, presence of fractures and general appearance of the wad once fired. Based on preliminary firing results, container wads with base thicknesses of 4.0 and 4.5 mm were selected for validation tests.

[0114] The firing conditions are summarized in Table 5: TEMPERATURE (°C)HUMIDITY (%)STEEL SHOT N°POWDER TYPEBALÍSTIC PRESSURE (bar)Room TempAtmospheric humidity3ssb+850

[0115] Container wads based on PBSA 1 matrix added with calcium stearate filler NCA1 (Formulation H) exhibited a satisfactory behavior after being shot in all cases. Some of the 4 mm wads presented small perforations or marks in the base, and / or small perforations in the petals, whereas for the 4.5 mm base thickness wads, the petals did not open and showed no breaks nor perforations, as can be observed in Figure 2.

[0116] Regarding the behavior of container wads based on PBSA 2 added with calcium stearate NCA1 (Formulation I), they also showed satisfactory performance results. Some of the wads occasionally showed small breaks at the base without perforations or small perforations in the petals (Figure 3).

[0117] The results for container wads manufactured with the PBSA based formulations selected in Example 2 as optimal in terms of mechanical properties, i.e., Formulations J, K and L. are shown in Figure 4. These wads also presented optimal behavior after being fired, with no significant damage seen at their base other than shot marks.B. Dimensional stability

[0118] To carry out the study, the provisions of EN 1604 standard were followed, which specifies the procedure to evaluate the dimensional changes of the container wads under certain conditions of temperature, relative humidity and exposure time.

[0119] The exposure scenarios as described in Table 6 were simulated in a DYCOMETAL climatic chamber model CCK300 and applied to the container wad prototypes in sequential cycles one after another: Conditioning → Humid heat → Cold → Humid heat → Extreme cold → Cold → Conditioning. Table 6. Exposure scenariosSCENARIOTEMPERATUREHUMIDITYTIMEStart. Conditioning23 °C50% RH24 hHumid heat30 °C93% RH96 hCold-5 °CAtmospheric humidity48 hHumid heat40 °C85% RH96 hExtreme cold-10 °CAtmospheric humidity48 hCold+5 °CAtmospheric humidity96 hEnd. Conditioning23 °C50% RH24 h

[0120] A sample of 5 container wad units made from formulation J - three specimens with petals and two without petals -was used for the experiments and their dimensions (length and diameter) controlled throughout the experiment. At least 10 measurements were performed at three points of the wad for each parameter and compared with the initial values, which corresponded to those measured after conditioning the probes for 24 hours at 23 °C and 50% RH. The assessment of the length and diameter variations was performed applying the following equations: Δ ε l ength = 100 lt − li / li Δ ε diameter = 100 d t − d i / d i

[0121] Figures 5 and Figure 6 show the diameter and length measurements collected for each of the wads after every exposure scenario. The recorded limits correspond to the maximum and minimum starting values.

[0122] It was found that the most critical conditions were those of humid heat (30 °C, 93% RH), with the length of the wads being the most affected parameter. Generally, most values were within the allowed tolerance (dashed lines), although some length readings were outside the limits, with length being more sensitive than diameter. However, it can be observed that the dimensional variation observed in both diameter and length does not generally exceed 0.5% for the different blocks under the different exposure conditions.C. Biodegradability / Compostability tests

[0123] Finally, the degree of disintegration of the cartridges was determined under simulated composting conditions in a laboratory. This test does not directly measure the biodegradability rate of the material but allowed a good estimation of its behavior under the action of microorganisms.

[0124] The composting process was carried out in a polypropylene bioreactor with two 5 mm diameter holes on two sides in order to allow the transfer of gases and which contains a matrix of synthetic solid waste of a constant composition (inoculum).

[0125] The incubation is carried out in a DYCOMETAL climatic chamber model CCK300 to control constant humidity and temperature conditions.

[0126] The reactors were placed in the climatic chamber stabilized at the temperature of the thermophilic incubation process, i. e., above 55 °C. Two container wad samples and 7 cut petal samples made of formulation J were introduced in the reactor, analyzing two replicates of the sample. The temperature was maintained constant throughout the experiment and the humidity conditions were controlled in order to avoid excessive evaporation of the water content in reactor. The gas exchange between the reactor and the environment was also controlled to ensure an aerobic composting process and promote the growth of aerobic microorganisms.

[0127] The disintegration of the wads and petals due to the effect of microorganisms is shown in Figure 7 A and B, respectively. The evolution of disintegration in the petals was more pronounced than that observed for the wads. All samples taken from the inoculum were cleaned to remove any rest of inoculum attached to the material, dried in a dehumidifier and weighed. Table 7 shows the weight of the two analyzed replicates corresponding to the petal sample over time. Table 7. Petal sample replicates weights.TimeReplicate 1 Weight (g)Replicate 2 Weight (g)3 days0.49000.38007 days0.43000.410018 days0.41000.350028 days0.31000.320049 days0.26000.040060 days0.17000.1400

[0128] The evolution of material weight loss is noticeable after 7 days, being more pronounced after 28 days of testing, reaching a mean value of 64% at 60 days.

[0129] Therefore, the analyzed materials present a good balance of properties in processing, and final application (firing tests) combined with an evident biodegradable character.

Claims

1. A wad for shotgun cartridges comprising a biodegradable formulation, wherein said formulation comprises: i) a biodegradable polymer selected from a polybutylene succinate (PBS) copolymer in an amount of at least 70% by weight relative to the total weight of the formulation; and ii) a stearate salt in an amount of between 0.01 and 5% by weight relative to the total weight of the formulation.

2. The wad according to claim 1, wherein the PBS copolymer is selected from the group consisting of polybutylene succinate-co-adipate (PBSA), polybutylene succinate-co-lactate (PBSL), polybutylene succinate-co-ε-caprolactone (PBS-co-CL), polybutylene succinate-co-carbonate (PBSC), polybutylene succinate-co-terephthalate (PBST), polybutylene succinate-co-diethylene glycol succinate (PBS-co-DEGS) and polybutylene succinate-co-furandicarboxylate (PBSF) and combinations thereof, preferably polybutylene succinate-co-adipate (PBSA).

3. The wad according to any one of claims 1 or 2, wherein the stearate salt is in an amount of between 0.05 and 4%, between 0.1 and 3%, between 0.1 and 2%, or between 0.1 and 1%, by weight relative to the total weight of the formulation.

4. The wad according to any one of claims 1 to 3, wherein the stearate salt is selected from the group consisting of calcium stearate, magnesium stearate, zinc stearate, aluminum stearate, sodium stearate and combinations thereof, preferably calcium stearate.

5. The wad according to any one of claims 1 to 4, wherein the biodegradable formulation further comprises at least a second biodegradable polymer, preferably in an amount of between 0.1 and 29.99% by weight relative to the total weight of the formulation.

6. The wad according to claim 5, wherein the at least a second biodegradable polymer is selected from the group consisting of biodegradable polyesters and polyvinyl alcohol (PVOH) and combinations thereof; preferably polylactic acid (PLA), poly(butylene adipate-co-terephthalate) (PBAT), polyhydroxyalkanoates (PHAs), polycaprolactone (PCL), polyvinyl alcohol (PVOH) and combinations thereof; more preferably polylactic acid, poly(butylene adipate-co-terephthalate) and combinations thereof.

7. The wad according to any one of claims 1 to 6, wherein the biodegradable formulation further comprises a compatibilizer, preferably in an amount of between 0.1 and 29.99% by weight relative to the total weight of the formulation.

8. The wad according to claim 7, wherein the compatibilizer is selected from the group consisting of polyvinyl acetate copolymers, polycaprolactone, polyesters, methacrylate-terminated reactive polystyrene, polycaprolactone / poly(tetramethylene glycol) block polyols, methacrylate-based polymers, block and grafted polymers and combinations thereof; preferably, polyvinyl acetate copolymer; more preferably, polyvinyl acetate-vinyl laurate copolymer.

9. The wad according to any one of claims 1 to 8, wherein the biodegradable formulation is selected from: - a biodegradable formulation comprising: i) a biodegradable polymer selected from a PBS copolymer in an amount of between 99 and 99.9%, and ii) a stearate salt in an amount of between 0.1 and 1% by weight; wherein the percentages by weight are relative to the total weight of the formulation and - a biodegradable formulation comprising: i) a biodegradable polymer selected from a PBS copolymer in an amount of at least 70% by weight; ii) a stearate salt in an amount of between 0.1 and 1% by weight; iii) at least a second biodegradable polymer in an amount of between 5 and 20% by weight; and iv) optionally, a compatibilizer in an amount of between 5 and 15% by weight; wherein the percentages by weight are relative to the total weight of the formulation.

10. The wad according to any one of claims 1 to 9, wherein the biodegradable formulation is selected from: - a formulation which comprises about 99.775% PBSA and about 0.225% calcium stearate; - a formulation which comprises about 72.475% PBSA, about 5.85% PLA, about 5.85% PBAT, additives comprising about 10% polyvinyl acetate-vinyl laurate copolymer, and 0.225% calcium stearate; and - a formulation which comprises about 72.475% PBSA, about 7.02% PLA, about 10.53% PBAT, additives comprising about 10% polyvinyl acetate-vinyl laurate copolymer, and 0.225% calcium stearate; wherein the percentages by weight are relative to the total weight of the formulation.

11. The wad according to any one of claims 1 to 10, wherein the wad is a container wad.

12. The wad according to claim 11, wherein the container wad has a shot cup and a sealing base, and wherein said base has a thickness between about 3.0 and 5.0 mm.

13. A cartridge comprising the wad as defined in any one of claims 1 to 12.

14. A process for manufacturing a wad according to any one of claims 1 to 12 comprising the following steps: a) providing a biodegradable polymer selected from a polybutylene succinate (PBS) copolymer and a stearate salt, b) mixing and heating the PBS copolymer and the stearate salt of step (a) to obtain a biodegradable formulation; and c) forming a wad from the biodegradable formulation of step (b) by injection moulding.

15. Use of a biodegradable formulation comprising: i) a biodegradable polymer selected from a polybutylene succinate (PBS) copolymer in an amount of at least 70% by weight relative to the total weight of the formulation; and ii) a stearate salt in an amount of between 0.01 and 5% by weight relative to the total weight of the formulation; in the manufacture of shotgun cartridges.

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