Wad for shot or bullet cartridges, shot or bullet cartridges comprising such wad, and methods of manufacturing said wad and said cartridge

Abstract

The present invention relates to a wad (30) that is at least partially biodegradable for shot or bullet cartridges (10), made of a single piece of plastic. Said wad (30) comprises one or more polymers, including one or more polybutylene succinate polymers, and calcium carbonate. The mass fraction of said polymer(s) in said wad (30) is greater than or equal to 70%, the mass fraction of calcium carbonate in said wad (30) is greater than or equal to 6.5%, and the polybutylene succinate polymer(s) constitutes the majority by mass in said wad (30). Figure for the abstract: 1.

Description

Title of the invention: Wad for shot or bullet cartridge, shot or bullet cartridge comprising such a wad, and methods of manufacturing said wad and said cartridge Technical field

[0001] The present invention relates to the technical field of wads for shot or bullet cartridges which are partly or totally biodegradable, in particular used for shot or bullet weapons, for example used for hunting or recreational shooting.

[0002] The present invention also relates to the technical field of shot or bullet cartridges comprising such wads.

[0003] The present invention also relates to methods of manufacturing partially or totally biodegradable wads for shot or bullet cartridges, and shot or bullet cartridges comprising such wads. Prior art

[0004] A cartridge wad is generally housed in the interior volume of the case of a shot or bullet cartridge for example and separates the projectile(s), for example the shot or pellets or the bullet, from the propellant powder.

[0005] When fired, the wad transmits to the projectile(s) the energy induced by the thrust of the combustion gases of the propellant powder. The wad must thus ensure an effective and regular thrust, and this in a reproducible manner.

[0006] The wad has, among its various functions, a piston function, and undergoes very high pressure during a shot, for example reaching more than 1000 bars, over a few hundred microseconds.

[0007] The wad must therefore not break / crack in the bore of the firearm in order to avoid obstructing said bore. For safety reasons, it is thus sought that the wad remains intact during firing, and after firing during its journey in the bore (or barrel) of the weapon and after its expulsion from the weapon. Premature breakage of the wad causes gas leaks and therefore a loss of thrust pressure.

[0008] During a shot, the wad is therefore released into the environment, sometimes in several scattered debris. Materials are therefore sought that are capable of degrading in the environment under the effect of micro-organisms and / or low temperatures, for example at temperatures lower than or equal to approximately 30°C-40°C, and / or water. It is also sought that these materials can guarantee the ballistic performance assured for a conventional non-biodegradable wad, and are sufficiently resistant to guarantee compliance with user safety standards.

[0009] The following documents describing biodegradable wadding are known.

[0010] EP 3,601,937 A1 describes a wad in two pieces, the first piece receiving the propellant powder and the second piece receiving the projectile(s). The first and second pieces are in different biodegradable polyesters in the examples, the first piece comprises PBSA and the second piece comprises PHA. The wad being in two separate pieces this implies a manufacturing process with several steps, and therefore longer and more expensive.

[0011] EP 3 290 858 B1 also describes a wadding comprising a biodegradable polyester, such as PLA, optionally mixed with a biodegradable elastomer, such as polycaprolactone or PBS, with calcium carbonate. The mass fraction of calcium carbonate is low and described as being at most 5%.

[0012] Lactic acid-based polymers are not satisfactory because they are difficult to implement using a plastics processing method (for example, by injection). In addition, the resulting wads break easily.

[0013] EP 1 877 721 A1 describes a wad obtained by injecting a mixture comprising from 50% to 67% by mass of PVA, from 20% to 30% of a filler, for example calcium carbonate, from 15% to 17% of a plasticizer based on glycerin and propylene glycol, and from 1% to 2% of a binder.

[0014] However, the biodegradable wadding of the state of the art is not satisfactory and encounters numerous problems.

[0015] Many wads are made from biodegradable polymers that are water-soluble (e.g., PVA or PHA) and therefore sensitive to moisture. Their properties can thus be altered under the usual storage conditions for cartridge wads. Wads made from moisture-sensitive biodegradable polymers must therefore be manufactured under specific humidity conditions and then bagged in a waterproof bag after manufacture. Waterproof bags increase the amount of plastic used. In addition, the manufacturing process is more expensive and complex to implement since the humidity level must be controlled and bagging machines must be invested. There are also non-plastic biodegradable wads made from cellulosic material, such as cardboard. However, cardboard is also sensitive to moisture, and the properties of the cellulose can thus deteriorate during storage.In addition, it is necessary to invest in specific machines for the production of such cardboard wadding.

[0016] Finally, biodegradable wads made from biodegradable polymers do not offer satisfactory mechanical performance, for example they break / crack when fired, and therefore do not correctly perform their piston function. The shots are also not regular.

[0017] The implementation of biodegradable polymers in plastic transformation processes for the specific manufacture of wads is also complex with significant transformation times (for example injection times).

[0018] In addition, the biodegradable polymers are in contact for an extended period of time with the projectile(s) and therefore must not negatively impact the ballistic properties of the projectile(s).

[0019] Finally, some biodegradable polymers are too expensive to be used profitably in cartridge wads.

[0020] The present invention thus aims to propose wads for shot or bullet cartridges whose manufacturing process is simplified, easily storable for a long period (for example from 6 months to approximately 2 years) without loss of their properties, ensuring regular shots and good mechanical performance, at low cost, and finally biodegradable under specific conditions, that is to say at low temperatures and / or under the effect of micro-organisms present in the environment while limiting its impact on the latter. Statement of the invention

[0021] The present invention relates, according to a first aspect, to an at least partly biodegradable wad for a shot or bullet cartridge overcoming the aforementioned problems in that it comprises: a first part comprising an open end and comprising a first housing arranged to receive a determined volume of projectile(s), and a second part comprising an open end and comprising a second housing arranged to receive a determined volume of at least one propellant charge.

[0022] Advantageously, said wad is a single-piece plastic part, said wad comprises one or more polymer(s) including one or more polybutylene succinate polymer(s), said wad comprises calcium carbonate, and the mass fraction of said polymer(s) in said wad is greater than or equal to 70%, and the mass fraction of calcium carbonate in said wad is greater than or equal to 6.5%, and the polybutylene succinate polymer(s) is, or are, the majority by mass in said wad.

[0023] Advantageously, the wad according to the invention satisfies the criteria set out in the standards issued by the CIP (Permanent International Commission for the Testing of Portable Firearms), and is at least partially biodegradable, and has good firing performance: standard deviation in firing speed of around 6 m / s, deviation in pressure measured during firing of around 60 bars, and regular speed during firing measured as at least 410 m / s.

[0024] Furthermore, the stuffing according to the invention does not require storage in particular humidity conditions, and therefore bagging to preserve its properties.

[0025] Advantageously, the duration of the injection-molding cycle of the wad according to the invention is reduced, which improves the productivity of the manufacturing process of said wad.

[0026] The inventors have thus surprisingly found that the combination of calcium carbonate, present at at least 10% by mass in the wad, with polybutylene succinate present predominantly among the polymer(s), in particular representing at least 70% by mass of the wad, makes it possible to reduce the wad injection time by at least 30%, and to improve the regularity of the shots in terms of reduction of the standard deviations of speed and pressure measured during the test shots.

[0027] When the mass fraction of calcium carbonate exceeds 30%, the standard deviations of speed and pressure increase, the regularity of the thirds thus deteriorates by approximately 10%.

[0028] When the mass fraction of calcium carbonate is less than 6.5%, no improvement in the reduction of the standard deviations of speed and pressure is observed compared to a control wad without calcium carbonate.

[0029] Advantageously, the stuffing according to the invention is biodegradable in the environment under the effect of micro-organisms and at room temperature.

[0030] The biodegradation tests carried out on the wad according to the invention during burial in the earth show a biodegradation of at least 90% after more than 150 days, and under the effect of water show a biodegradation of at least 90% after more than 84 days.

[0031] In one embodiment, at least 50% by mass of the fluff is biodegradable, more preferably at least 60% or at least 70% by mass, or at least 80% by mass of the fluff is biodegradable, more preferably at least 90% by mass of the fluff is biodegradable.

[0032] Preferably, the polymer(s) that the stuffing comprises is / are biodegradable, in particular polybutylene succinate is biodegradable.

[0033] Advantageously, polybutylene succinate is a biodegradable aliphatic polyester.

[0034] Advantageously, poly(butylene succinate) (PBS), also called poly(tetramethylene succinate), is a thermoplastic polymer formed by polymerization of succinic acid, or at least one diester of succinic acid, such as dimethyl succinate, with 1,4-butanediol.

[0035] Advantageously, calcium carbonate is biodegradable.

[0036] Calcium carbonate (CaCO3) is advantageously composed of carbonate ions (CO32) and calcium ions (Ca2+).

[0037] Biodegradability, particularly in soil under aerobic conditions, can be measured using the following standards:

[0038] - ISO 17556 entitled “Plastics- Determination of the ultimate aerobic biodegra- dability in soil by measuring the oxygen demand in a respirometer or the amount of carbon dioxide released”, dating from 2019; - ISO 11266 entitled “Soil quality - Guidance on laboratory testing for biodegradation of organic Chemicals in soil under aerobic conditions”, dating from 1994; - ASTM D5988 entitled 'Standard Test Method for Determining the Aerobic Biodegradation of Plastic Materials in Soil', dated 2018.

[0039] Biodegradability in soil under aerobic conditions is preferably measured using the ISO 17556 standard cited above, dating from 2019. Preferably, the test conditions are as follows: the control article is powdered cellulose, the tested fluff is reduced in size (cryogenic grinding); the incubation temperature is kept at 25°C + / -2°C and the test lasts 4 months. The duration of the test can be increased depending on the intended purpose. Biodegradability in an aqueous medium is preferably determined using ISO 14851, “Determination of the ultimate aerobic biodegradability of plastic materials in an aqueous medium - Method by measuring the oxygen demand in a closed respirometer,” dated 2019.

[0040] The biodegradability of the fluff or of a polymer or generally of any component used in the fluff according to the invention can be determined by the ISO 14851 standard, dating from 2019, or by the ISO 17556 standard, dating from 2019.

[0041] The propellant powder is in the form of solid particles, for example it is a flake propellant powder or a tubular propellant powder.

[0042] Preferably, the first part is in the form of an elongated cup.

[0043] Preferably, the second part is cup-shaped.

[0044] Advantageously, the open end of the first part opens directly into the first housing, and the open end of the second part opens directly into the second housing.

[0045] Advantageously, the first part has a substantially cylindrical general shape.

[0046] Advantageously, the second part has a substantially cylindrical general shape.

[0047] Advantageously, the first housing comprises an open end and a bottom.

[0048] Advantageously, the second housing comprises an open end and a bottom.

[0049] Advantageously, the bottom of the second housing is substantially opposite the bottom of the first accommodation.

[0050] Advantageously, the wad comprises a longitudinal axis L, and the first and second parts extend along the longitudinal axis.

[0051] Advantageously, the stuffing is made up of the first and second parts, and a dividing wall separating said first and second parts.

[0052] Advantageously, the bottom of the first part and the bottom of the second part are separated by a separating wall, in particular having a thickness greater than or equal to 2.00 mm. More particularly, the separating wall is solid.

[0053] Advantageously, the first and second parts are aligned along the longitudinal axis of the wad.

[0054] Advantageously, the central axis of symmetry of the first part coincides with the central axis of symmetry of the second part, the central axis of symmetry being parallel to the longitudinal axis of the wad.

[0055] Advantageously, the wad is a single-piece plastic part and is therefore obtained by hot molding of a plastic mixture, in particular comprising one or more polymer(s) mixed with at least calcium carbonate, for example by injection (molding).

[0056] Advantageously, the stuffing is a single-piece plastic part.

[0057] Advantageously, the method of manufacturing the stuffing is simple and therefore the stuffing is inexpensive. In addition, there is no problem of resistance to delamination between two parts of the stuffing which would be secured to each other.

[0058] Advantageously, the stuffing does not include any other part. Definitions

[0059] In this text, biodegradable means any material (for example: fluff, a biodegradable polymer, etc.) capable of degrading / decomposing in a natural environment (for example: a forest) under the effect of micro-organisms (bacteria, fungi, algae, etc.) and / or ambient heat, possibly in combination with water. Advantageously, the result of this decomposition is the formation of water, CO2 and / or methane and possibly by-products (residues, new biomass, etc.) that are not harmful to the environment.

[0060] In the present text, the term “polymer” means any homopolymer or copolymer consisting of at least two different monomers.

[0061] In this text, the expression “at least partly biodegradable” means that the stuffing is totally or partially biodegradable.

[0062] In the present text, the value Dx is understood to mean that x% by mass of the particles (in particular of the powder) of calcium carbonate (optionally surface-treated) have a size less than the value Dx, and that (100-x)% by mass of these particles have a size greater than said value. The particle size is preferably determined using a Mastersize 2000 laser granulometer (Malvern Instrument).

[0063] By polybutylene succinate polymer(s) is understood that the fluff or the mixture i) of the process for manufacturing the fluff may comprise a polybutylene succinate polymer or several different polybutylene succinate polymers.

[0064] In the present text, the term "surface-treated calcium carbonate" means that the calcium carbonate particles have been surface-treated with a specific mixture, in particular based on acid(s) as described in the present text.

[0065] In the present text, it is understood by a polybutylene succinate polymer which is the majority by mass in the fluff that the mass fraction of this polybutylene succinate polymer in the fluff is the highest mass fraction compared to the mass fractions of the other components constituting the fluff.

[0066] In the present text, it is understood by polybutylene succinate polymers that the mass fraction of these polybutylene succinate polymers in the fluff is the highest mass fraction compared to the mass fractions of the other components constituting the fluff.

[0067] In this text, projectile(s) means shot or pellets or even a bullet.

[0068] In the present text, the term "plastic part" is understood to mean that said part is based on one or more thermoplastic polymer(s), that is to say this or these polymer(s) represent at least 50% by mass, preferably at least 60% or 70% by mass, of said plastic part.

[0069] The mass fraction of one or more component(s) (e.g. polymer or calcium carbonate) in said fluff is calculated as the ratio of the mass of said component(s) to the total mass of said fluff multiplied by 100.

[0070] In this text, the term propellant charge is understood to mean any type of propellant powder selected so that its combustion causes a strong release of gas, the pressure of which expels the wad from the weapon.

[0071] The fluff according to the invention may comprise component(s) other than calcium carbonate and polybutylene succinate polymer(s) such as one or more pigment(s), or one or more thermoplastic biodegradable polymer(s) (in particular polyester), for example PLA (lactic acid polymer) or PBSA, but the mass fraction of which is less than or equal to 15%, in particular less than or equal to 10%, in the fluff.

[0072] In one embodiment, the mass fraction of calcium carbonate and polybutylene succinate(s) in the fluff is greater than or equal to 80%, more preferably greater than or equal to 85%, preferably greater than or equal to 90% or 95%.

[0073] In one embodiment, the polymer(s) that the fluff comprises, in particular the polybutylene succinate polymer(s) that the fluff comprises, have(s) (in particular each) at least one of the characteristics chosen independently from the following characteristics:

[0074] - a density (g / cm3) greater than or equal to 1.10 and less than or equal to 1.30, in par particular greater than or equal to 1.20 and less than or equal to 1.30, in particular measured with the ISO 1183 standard; and / or

[0075] - a Hot Fluidity Index (MFR: Melt Flow Rate) measured at 190°C, under a load of 2.16 kg, in particular with the ISO 1133 standard, greater than or equal to 1 g / lOmin and less than or equal to 10 g / 10 min, in particular greater than or equal to 2 g / lOm min and less than or equal to 6 g / 10 min; and / or

[0076] - a melting temperature greater than or equal to 60°C and less than or equal to 100°C, in particular ranging from 80°C to 90°C, in particular measured with the ISO 3146 standard; and / or

[0077] - an elongation at break measured with the ISO 527-2 standard (%) greater than or equal to 200%, in particular greater than or equal to 250% or greater than or equal to 300%, more particularly greater than or equal to 350%, in particular less than or equal to 600%;

[0078] - a flexural modulus (MPa) measured with the ISO 178 standard less than or equal to 400 MPa, in particular greater than or equal to 100 MPa, more particularly less than or equal to 300 MPa, even more particularly greater than or equal to 200 MPa; and / or

[0079] - an Izod impact resistance at 23°C (KJ / m2) measured with the ISO 180 standard on greater than or equal to 20 KJ / m2, preferably greater than or equal to 30 KJ / m2 or 40 KJ / m2, in particular less than or equal to 80 KJ / m2; and / or

[0080] - a Rockwell hardness (R Scale) measured with the ISO 2039-2 standard higher than or equal to 30 and less than or equal to 100, preferably less than or equal to 80, more preferably less than or equal to 70 and greater than or equal to 40.

[0081] Preferably, the calcium carbonate is chosen from ground calcium carbonates (for example from marble, limestone, dolomite and / or chalk) and / or precipitated calcium carbonates (for example vaterite, calcite and / or aragonite) and / or calcium carbonates treated by a surface reaction (in particular designated in the present text as surface-treated calcium carbonate(s)), and / or in mixtures of the latter.

[0082] Preferably, at least 55% by number of the particles of the calcium carbonate have a size less than or equal to 2 pm.

[0083] The wads according to the invention must comply with the standards issued by the CIP relating to safety (Permanent International Commission for the Proof of Portable Firearms). This commission legislates, particularly in France, on the safety standards for ammunition and firearms.

[0084] Advantageously, the wad according to the invention is adapted to a shot or bullet cartridge.

[0085] In a non-limiting manner, a shot or bullet cartridge can be used with a hunting or sporting rifle, or even a semi-automatic rifle but also in other types of weapons, such as smoothbore or rifled weapons.

[0086] Advantageously, the wad has the function of cleaning the lumen of the firearm with each shot, and of ensuring uniform thrust on the base of the projectile(s).

[0087] Advantageously, the wad is an intermediate member arranged between a propellant powder and the projectile(s).

[0088] Advantageously, the stuffing is a skirted stuffing.

[0089] In an alternative embodiment, the calcium carbonate comprises, or is, a calcium carbonate surface-treated with a mixture of (poly)carboxylic acid(s) and / or one or more acid anhydrides of said (poly)carboxylic acid(s), and / or one or more salts of said (poly)carboxylic acid(s) and / or one or more salts of said acid anhydride(s).

[0090] In one embodiment, the calcium carbonate comprises, or is, calcium carbonate surface-treated with at least one mono-substituted succinic anhydride and / or at least one linear or branched aliphatic carboxylic acid, and / or one of its salts, comprising from 8 to 24 carbon atoms, preferably stearic acid, more preferably stearic acid at a level of at least 10% by mass.

[0091] For example, calcium carbonate can be surface treated with succinic anhydride and with a mixture of stearic acid:palmitic acid: 1:1.

[0092] In an alternative embodiment, the calcium carbonate comprises, or is, surface-treated calcium carbonate, in particular as described in the present text, in a mixture with one or more at least partly biodegradable support polymer(s), for example one or more aliphatic polyester(s), such as polybutylene adipate terephthalate (PBAT), polylactic acid (PLA) or polybutylene succinate (PBS) and mixtures thereof, in particular so as to form a primary calcium carbonate-based compound in which the calcium carbonate, in particular the surface-treated calcium carbonate, represents at least 65% by mass of said primary calcium carbonate-based compound and / or the support polymer(s) represent(s) at most 35% by mass of said primary calcium carbonate-based compound.

[0093] In particular, the support polymer(s) is / are included in the calculation of the mass fraction of polymer(s) of said fluff.

[0094] In an alternative embodiment, the stuffing comprises a primary compound comprising said calcium carbonate, in particular surface-treated.

[0095] Preferably, the fluff comprises at least 10% by mass, and at most 30% by mass of said primary compound.

[0096] The primary compound is as described in the present text.

[0097] In particular, the primary compound comprises at least 50%, or at least 60%, by mass of calcium carbonate, in particular surface-treated, and one or more biodegradable polymer(s), in particular the mass fraction of which in said primary compound is greater than or equal to 5% and less than or equal to 40%, more particularly greater than or equal to 20% and less than or equal to 40%.

[0098] In an alternative embodiment, the calcium carbonate, optionally surface-treated, comprises, or is, calcium carbonate comprising from 40% to 70% by mass, preferably from 50% to 60% by mass, of particles whose D50 is less than or equal to 2 pm.

[0099] In an alternative embodiment, the calcium carbonate, optionally surface-treated, comprises, or is, calcium carbonate whose D50 is greater than or equal to 0.1 pm and less than or equal to 7 pm, preferably greater than or equal to 0.5 pm and less than or equal to 4 pm.

[0100] In an alternative embodiment, the calcium carbonate, optionally surface-treated, comprises, or is, calcium carbonate whose D98 is less than or equal to 50 pm, preferably less than or equal to 40 pm, more preferably less than or equal to 15 pm.

[0101] In an alternative embodiment, the calcium carbonate, optionally surface-treated, comprises, or is, calcium carbonate whose specific surface area (BET) is greater than or equal to 0.5 and less than or equal to 150 m2 per gram of calcium carbonate. The specific surface area (BET) is preferably determined with the ISO 9277:2022 standard entitled “Determination of the air mass (surface area) of solids by gas adsorption - BET method”.

[0102] In an alternative embodiment, the mass fraction of calcium carbonate, optionally surface-treated, in the fluff is greater than or equal to 9.5% and less than or equal to 20%, preferably less than or equal to 16.5%, in particular is of the order of 13% to within + / - 3%.

[0103] The inventors have determined that this interval makes it possible to obtain a standard deviation on the speed VI during a reduced shot, in particular of the order of 5-6 meters / second (m / s).

[0104] In an alternative embodiment, the wad is an injection-molded part, in particular the bottom of the first part of the wad is the ejection zone of the mold and / or the bottom of the second part of the wad is the injection point zone.

[0105] In an alternative embodiment, the mass fraction of polymer(s), in particular of polybutylene succinate polymer(s), is greater than or equal to 70% and less than or equal to 95%, in particular greater than or equal to 80% and less than or equal to 95%, more particularly less than or equal to 90%.

[0106] Advantageously, the polymer(s) is / are one or more aliphatic and / or aromatic polyester(s), preferably an aliphatic polyester.

[0107] Advantageously, the polymer(s) is / are biodegradable.

[0108] In an alternative embodiment, the polybutylene succinate polymer represents at least at least 70% by mass of the fluff, preferably at least 80% by mass of the fluff, more preferably at least 90% by mass of the fluff.

[0109] In an alternative embodiment, the stuffing has a density ranging from 1.20 g / cm3 to 1.50 g / cm3.

[0110] In an alternative embodiment, the first part of the wadding is a skirt comprising longitudinal slits, in particular comprising from 2 to 6 longitudinal slits, more particularly from 3 to 5 longitudinal slits, for example 4 longitudinal slits.

[0111] Advantageously, the longitudinal slots are open on the open end of the first part of the wad.

[0112] Advantageously, the longitudinal slots extend from the open end of the first part of the wad, i.e. from its distal part, towards its proximal part, and extend over at least 50% of the height, in particular over at least 2 / 3 of the height, of the first part of the wad.

[0113] In an alternative embodiment, the first part of the wad comprises a proximal part and a distal part, and the thickness of the wall of the first part decreases from its proximal part towards its distal part.

[0114] Preferably, the wall of the first part is a radial wall.

[0115] In an alternative embodiment, the second portion of the wad comprises a proximal portion and a distal portion, and the thickness of the wall of the second portion is substantially constant from its proximal portion to its distal portion.

[0116] Preferably, the wall of the second part is a radial wall.

[0117] In an alternative embodiment, the wad comprises a separating wall separating a bottom of the first part of the wad from the bottom of the second part of the wad, said separating wall having a thickness greater than or equal to 2.00 mm.

[0118] Advantageously, said separation wall is solid.

[0119] In a variant, the height of the first part of the wad is greater than or equal to 5 times the height of the second part of the wad.

[0120] Preferably, the height of the first part of the wad is greater than or equal to 20 mm, more preferably greater than or equal to 30 mm, in particular less than or equal to 60 mm, for example from 33 mm to + / - 3 mm.

[0121] Preferably, the height of the second part of the wad is greater than or equal to 2 mm, more preferably greater than or equal to 4 mm, in particular less than or equal to 10 mm, for example from 5.50 mm to + / - 1 mm.

[0122] The present invention relates, according to a second aspect, to a shot or bullet cartridge comprising an at least partly biodegradable wad for a shot or bullet cartridge according to any one of the variant embodiments with reference to the first aspect of the invention.

[0123] The shot or bullet cartridge must satisfy the rules set out by the CIP cited above.

[0124] The cartridge is suitable for a portable pellet or bullet weapon, by way of non-limiting examples for the following portable weapons: hunting or sporting rifle, semi-automatic rifle, or can be used in other types of weapons, such as smoothbore or rifled bore weapons.

[0125] The present invention relates, according to a third aspect, to a method for manufacturing an at least partly biodegradable wad for a shot or bullet cartridge comprising the following steps: - i) preparation of a mixture comprising one or more polymer(s) including one or more polybutylene succinate polymer(s), and further comprising a primary compound comprising calcium carbonate, the mass fraction of said polymer(s) in said mixture is greater than or equal to 70%, the mass fraction of calcium carbonate in said mixture is greater than or equal to 6.5%, and the polybutylene succinate polymer(s) is, or are, the majority by mass in said mixture, -ii) implementation by heating said mixture from step i) in a single molding step for molding a primary wad for a shot or bullet cartridge with a mold assembly comprising a primary wad impression for a shot or bullet cartridge - iii) recovery of the primary wad for cartridge molded in said mixture

[0126] - optionally a step iv) of preparation of one or more longitudinal slot(s) tudinal(s) in the first part of the cartridge wad, - in particular we recover the wadding for finished cartridges.

[0127] Preferably, step iv) of preparing one or more longitudinal slit(s) comprises cutting said slit(s) in the first part.

[0128] Preferably, step ii) comprises heating the mixture on an extruder comprising an extrusion screw with several distinct heating zones, with one or more zone(s) having a heating temperature preferably greater than or equal to 150°C and less than or equal to 220°C, in particular ranging from 170°C to 200°C.

[0129] Preferably, step ii) is an extrusion-molding step and / or an injection-molding step.

[0130] In an alternative embodiment, the polybutylene succinate(s) represent(s) at least 70% by mass of said mixture of step i), preferably at least 80% by mass of said mixture of step i), in particular at most 90% by mass of said mixture of step i).

[0131] In an alternative embodiment, the calcium carbonate represents at least 6.5%, or at least 9.5%, by mass of said mixture of step i), preferably at most 20% by mass. mass of the mixture from step i), more preferably at most 16.5% by mass of said mixture from step i).

[0132] In an alternative embodiment, the calcium carbonate of the primary compound comprises, or is, calcium carbonate surface-treated with a mixture of (poly)carboxylic acid(s) and / or one or more acid anhydrides of said (poly)carboxylic acid(s), and / or one or more salts of said (poly)carboxylic acid(s) and / or one or more salts of said acid anhydride(s), and the primary compound comprises one or more biodegradable polymer(s) mixed with said calcium carbonate.

[0133] The variant embodiments concerning the description of calcium carbonate with reference to the first aspect of the invention apply to calcium carbonate used in the method of manufacturing the fluff according to a third aspect of the invention.

[0134] In an alternative embodiment, the mass fraction of calcium carbonate, in particular surface-treated, in the primary compound is greater than or equal to 50%, preferably greater than or equal to 65%, in particular less than or equal to 90%, in particular of the order of 65% to within + / - 5%.

[0135] In an alternative embodiment, the mass fraction of at least partly biodegradable support polymer(s) in the primary compound, said support polymer(s) being mixed with the calcium carbonate (optionally surface-treated), is greater than or equal to 5% and less than or equal to 40%, in particular greater than or equal to 20%, in particular of the order of 35% to within + / - 5%.

[0136] In an alternative embodiment, the mass fraction of at least partly biodegradable support polymer(s) in the mixture of step i) is greater than 0%, in particular greater than or equal to 3.5%, and less than or equal to 15%, in particular less than or equal to 10.5%, for example of the order of 7.5% to within + / - 3%.

[0137] In an alternative embodiment, the volume density of the primary compound comprising calcium carbonate is greater than or equal to 1.5 g / cm3 and less than or equal to 1.8 g / cm3, in particular greater than or equal to 1.6 g / cm3 and less than or equal to 1.7 g / cm3.

[0138] In an alternative embodiment, the primary compound has a hot melt index greater than or equal to 5g / 10 min, in particular greater than or equal to 7g / 10 min and less than or equal to 20g / 10m min, measured at a temperature of 190°C, under a mass of 2.16 kg, and according to the ISO 1133-1 standard, in particular dating from 2022.

[0139] Preferably, the melt flow index is greater than or equal to 7 g / 10 min and less than or equal to 17 g / 10 min, in particular greater than or equal to 8 g / 10 min and less than or equal to 15 g / 10 min.

[0140] In an alternative embodiment, at least one of the polybutylene succinate(s), or each of the polybutylene succinates has a tensile modulus measured in the machine direction on a 20 μm thick extruded blown film with the ISO 527-3:2018 standard greater than or equal to 200 MPa.

[0141] In an alternative embodiment, at least one of the polybutylene succinate(s), or each of the polybutylene succinates, has a Melt Flow Index greater than or equal to 1 g / 10 min and less than or equal to 10 g / 10 min, in particular greater than or equal to 2 g / 10 min and less than or equal to 6 g / 10 min, measured at a temperature of 190°C, under a mass of 2.16 kg, and according to the ISO 1133-1 standard, in particular dating from 2022.

[0142] In particular, the ISO 1133-1 standard, dating from 2022, is entitled “Plastics — Determination of the melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics — Part 1: Standard method”.

[0143] Preferably, the polybutylene succinate polymer(s) has(have) at least one of the characteristics chosen independently from the following characteristics:

[0144] - a density (g / cm3) greater than or equal to 1.10 and less than or equal to 1.30, in par particular greater than or equal to 1.20 and less than or equal to 1.30, in particular measured with the ISO 1183 standard; and / or

[0145] - a Hot Fluidity Index (MFR: Melt Flow Rate) measured at 190°C, under a load of 2.16 kg, in particular with the ISO 1133 standard, greater than or equal to 1 g / lOmin and less than or equal to 10 g / 10 min, in particular greater than or equal to 2 g / lOm min and less than or equal to 6 g / 10 min; and / or

[0146] - a melting temperature greater than or equal to 60°C and less than or equal to 100°C, in particular ranging from 80°C to 90°C, in particular measured with the ISO 3146 standard; and / or

[0147] - an elongation at break measured with the ISO 527-2 standard (%) greater than or equal to 200%, in particular greater than or equal to 250% or greater than or equal to 300%, more particularly greater than or equal to 350%, in particular less than or equal to 600%;

[0148] - a flexural modulus (MPa) measured with the ISO 178 standard less than or equal to 400 MPa, in particular greater than or equal to 100 MPa, more particularly less than or equal to 300 MPa, even more particularly greater than or equal to 200 MPa; and / or

[0149] - an Izod impact resistance at 23°C (KJ / m2) measured with the ISO 180 standard su greater than or equal to 20 KJ / m2, preferably greater than or equal to 30 KJ / m2 or 40 KJ / m2, in particular less than or equal to 80 KJ / m2; and / or

[0150] - a Rockwell hardness (R Scale) measured with the ISO 2039-2 standard higher than or equal to 30 and less than or equal to 100, preferably less than or equal to 80, more preferably less than or equal to 70 and greater than or equal to 40.

[0151] The present invention relates, according to a fourth aspect, to a method of fa manufacturing a shot or bullet cartridge according to a second aspect of the invention, comprising the following steps: - providing a wad for a shot or bullet cartridge according to any one of the embodiments with reference to the first aspect of the invention and a cartridge comprising a case, said case comprising a primer, - placing a determined volume of a propellant charge inside the case, - placing the wad for a shot or bullet cartridge in the case, - placing one or more projectiles in the case, - crimping the cartridge, and - recover the cartridge obtained.

[0152] The features and variant embodiments with reference to the first aspect of the invention may be combined with each other independently of each other, and with any of the variant embodiments with reference to the second aspect or the third aspect or fourth aspect of the invention. Description of the drawings

[0153] The invention will be better understood on reading the following description of the embodiments of the invention given as non-limiting examples, with reference to the appended drawings, in which:

[0154] [Fig-1] [Fig.l] is a schematic representation in longitudinal section of a first example of a shot cartridge according to the invention;

[0155] [Fig.2] [Fig.2] schematically represents the stuffing shown in [Fig.l] Description of the embodiments

[0156] The cartridge 10 shown in [Fig.l] comprises a case 20 having a distal end 22 and a proximal end 24, said case 20 receiving in its interior volume 26 a wad 30 according to the invention. The cartridge 10 further comprises a base 15 and a primer 17 mounted on the bottom 16 of the base 15. The base 15 is mounted on the open proximal end 24 of the case 20 and closes it. The cartridge 10 comprises a reinforcement 40 in the form of an open cup secured to the primer 15 and receiving a portion of the propellant charge 50. The distal end 22 of the case 20 is folded back on itself in order to close it and thus forms a pleated closure 28.

[0157] Advantageously, the wad 30 comprises a first part 31 having an open end, and comprising a first housing 32 arranged to receive a determined volume of projectile(s), here shot 50, and a second part 33 having an open end, and comprising a second housing 34 arranged to receive a determined volume of at least one propellant charge 60.

[0158] Advantageously, the wadding 30 is a single-piece plastic part. The wadding 30 is shown in detail in [Fig.2].

[0159] Advantageously, the height H1 of the first part 31 is greater than or equal to 5 times, in particular greater than or equal to 6 times, the height H2 of the second part 32. For example, H1 is approximately 33.00 mm and H2 is approximately 5.50 mm.

[0160] Advantageously, the bottom 35 of the first part 31 is substantially flat.

[0161] Advantageously, the bottom 36 of the second part 33 is substantially arched, i.e. in bow.

[0162] Advantageously, the thickness eint of the separation wall 37 separating the bottom 35 of the first part 31 from the bottom 36 of the second part 33 is greater than or equal to 2.00 mm, in particular greater than or equal to 2.50 mm to within + / - 10%.

[0163] The first part 31 comprises a proximal part 31a and a distal part 31b, and the thickness of the wall 31c, in particular of the radial wall 31c, of the first part 31 decreases from its proximal part 31a towards its distal part 31b.

[0164] For example, the thickness e31a of the wall 31c of the first part 31 in its proximal part 31a is 1.16 mm while the thickness e31b of the wall 31c of the first part 31 in its distal part 31b is 0.60 mm. The thickness of the wall 31c of the first part 31 thus decreases substantially by half progressively between its proximal part 31a and its distal part 31b.

[0165] Advantageously, the external diameter De of the wad 30 varies according to the caliber of the weapon, for example it can be 18 mm.

[0166] Advantageously, the thickness e33 of the wall 33c of the second part 33 is substantially constant, for example of the order of 0.57 mm.

[0167] Advantageously, the wad 30 comprises a longitudinal axis L along which the first and second parts (31, 33) extend, and a transverse axis T substantially perpendicular to the axis L.

[0168] Advantageously, the first part 31 is a skirt comprising longitudinal slits (not visible), in particular comprising from 2 to 6 longitudinal slits, in particular 4 longitudinal slits distributed in a substantially equidistant manner. Preferably, a longitudinal slit opens onto the open end of the distal part 31 and extends from the latter over at least half of the height H1, in particular over at least 2 / 3 of the height HL

[0169] Advantageously, the access opening to the housing 32 of the first part 31 is opposite the access opening to the housing 34 of the second part 33.

[0170] Advantageously, the first and second parts (31, 33) are aligned along the longitudinal axis of the wad 30.

[0171] Advantageously, the central axis of symmetry SI of the first part 31 coincides with the central axis of symmetry S2 of the second part 33, the axis of symmetry central SI or S2 being parallel to the longitudinal axis L of the wad 30.

[0172] Advantageously, the wad 30 is manufactured by implementing an injection molding step using a mold comprising a molding impression of said wad 30 without longitudinal slots. Advantageously, a mixture comprising approximately 70% to 90% by mass of one or more polybutylene succinate (PBS) polymer(s), and approximately 6.5% to 30% by mass of calcium carbonate, in particular a surface-treated calcium carbonate, in particular a primary compound based on calcium carbonate, is extruded on a screw with several heating zones, for example 5 separate heating zones, then the molten mixture is injected into the mold. Those skilled in the art know how to adapt the heating and injection parameters of the mixture to obtain an injection-molded part. The injected mixture is allowed to cool, then the injected part forming an intermediate wad is removed from the mold.The longitudinal slots are then made in the first part in a finishing step but without adding any other part(s) to the intermediate wad to finalize the latter and obtain the wad according to the invention, for example wad 30.

[0173] The precise dimensions indicated for the wad and the cartridge are given here as non-limiting examples for a given volume of projectile(s), i.e. approximately 32g of shot and a given volume of propellant charge. These dimensions vary depending on the volume of projectile(s), for example 35g or 28g, the volume of the propellant charge, and the diameter or caliber of the weapon. However, these dimensions preferably remain in the same proportions with regard to the ratio of the heights H1 and H2, or the thickness of the separating wall or the variability of the thickness of the radial wall of the first part of the wad or the constancy of the thickness of the radial wall of the second part of the wad.

[0174] Description of comparative examples and according to the invention

[0175] Test cartridges are prepared with 32g of shot, the test cartridges correspond to that described in Figures 1 and 2 but without the decrease in the thickness of the wall 31c, without the higher thickness eint (here for the comparative examples eint is approximately 1 mm), and without the curved bottom of the second part 33. These latter structural parameters are present only on the tests according to the invention because they were provided to improve the performance of the wad according to the invention.

[0176] Comparative example 1:

[0177] A wad comprising 32g of shot, with 100% by mass of polybutylene succinate (PBS), in particular of the FZ71 (PM / PB) grade marketed by the company Biochem Company Ltd, is injected in a single piece, 4 longitudinal slots are made. The flexural modulus (measured with the ISO 178 standard) is approximately 630 MPa. The wad is placed in a test cartridge as described above, and firing tests are carried out. The average firing speed is 402.9 m / s, with a minimum of 389 m / s and a maximum of 433.5 m / s. The pressure exerted and measured is approximately 698.4 bars with a minimum of 545.1 bars and a maximum of 948 bars. The standard deviation of speed measured on VI (m / s) is 14.5 m / s while that which the inventors seek to achieve is approximately 6 m / s at most, and the standard deviation of pressure PI (bars) is 130 bars while the inventors seek to achieve approximately 60 bars and at most. In addition, the wad breaks / fragments as it leaves the barrel of the weapon. The wad therefore does not meet the standards set by the CIP.

[0178] Comparative example 2:

[0179] The same test as Comparative Example 1 is carried out with the only difference that the polybutylene succinate is replaced by a more flexible grade FD92 (PM / PB) from BioChem Company Ltd, in particular having a flexural modulus (ISO 178) of approximately 250 MPa.

[0180] The standard deviation of speed measured on VI (m / s) is 8.6 m / s, and the standard deviation of pressure PI (bars) is 57.5 bars. In addition, the wad does not fragment at the exit of the barrel of the weapon. Nevertheless, the standard deviation on speed VI is still too high.

[0181] Example according to the invention 1:

[0182] The same test as comparative example 2 is carried out with the difference that the injected mixture comprises 10% by mass of a primary compound comprising calcium carbonate, in particular comprising a surface-treated calcium carbonate, such as Carbomax®Bio marketed by the company Cabamix®, and 90% by mass of the PBS FD92 (PM / PB) grade used in the example.

[0183] The primary compound comprises 65% by mass of surface-treated calcium carbonate, such as Smartfill® OM 55 calcium carbonate marketed by OMYA®, in a mixture with approximately 35% by mass of a biodegradable aliphatic polyester, in particular PBS, preferably of the same grade as that tested and marketed by BioChem Company Ltd.

[0184] The standard deviation on pressure PI (bars) remains at around 60 bars. The wad does not fragment when fired into the barrel or when exiting it. A reduction in the standard deviation on the speed of around 11% and a reduction in the injection time are observed.

[0185] Example according to the invention 2:

[0186] The same test as example according to the invention 1 is carried out with the difference that the injected mixture comprises 20% by mass of said primary compound comprising calcium carbonate, in particular Carbomax®Bio marketed by the company Cabamix®, and 80% by mass of the PBS FD92 grade (PM / PB) used in comparative example 2.

[0187] The standard deviation on PI pressure (bars) remains around 60 bars. The wad does not does not fragment when fired into or out of the barrel. There is a reduction in the standard deviation on the speed of approximately 22% and a very significant reduction in the injection time.

[0188] Example invention 3:

[0189] The same test as the example according to the invention 1 is carried out with the difference that the injected mixture comprises 30% by mass of the primary compound based on calcium carbonate, in particular Carbomax®Bio marketed by the company Cabamix®, and 70% by mass of the PBS FD92 grade (PM / PB) used in comparative example 2. The standard deviation on pressure PI (bars) remains around 60 bars. The wad does not fragment when fired into the barrel or at the exit thereof. A standard deviation on the speed is observed to be maintained at around 8 m / s (therefore no improvement compared to comparative example 2) and a reduction in the injection time.

[0190] Comparative example 3:

[0191] The same test as the example according to the invention 1 is carried out with the difference that the injected mixture comprises 40% by mass of the primary compound based on calcium carbonate, in particular Carbomax®Bio marketed by the company Cabamix®, and 60% by mass of the PBS FD92 grade (PM / PB) used in comparative example 2. The standard deviation on pressure PI (bars) remains around 60 bars. The wad does not fragment when fired in the barrel or at the exit of the latter. A deterioration of the standard deviation on the speed of approximately 10% is observed compared to that obtained for comparative example 2, and an injection time similar to that of comparative example 2. There are therefore no improvements in the ballistic performances of the wad, nor of the injection process.

[0192] Biodegradability was measured on the fluff of example 2 according to the invention by burial in the earth according to the ISO 17556 standard dating from 2019. It is observed that 90% by mass of the fluff is biodegraded after 151 days.

[0193] Biodegradability was also measured on the fluff of example 2 according to the invention in an aqueous medium according to the ISO 14851 standard dating from 2019. It is observed that 90% by mass of the fluff is biodegraded after 84 days.

[0194] The wad according to the invention thus makes it possible to offer improved and regular ballistic performance, while being biodegradable.

[0195] The stuffing according to the invention can also be obtained by a simple injection-molding process and the productivity of which is even improved with regard to the injection time reduced by approximately 22%. In addition, the stuffing according to the invention does not require special storage conditions, nor bagging to protect it from humidity.

Claims

Claims

1. At least partly biodegradable wad (30) for a shot or bullet cartridge (10) comprising a first part (31) having an open end and comprising a first housing (32) arranged to receive a determined volume of projectile(s) (50), and a second part (33) having an open end and comprising a second housing (34) arranged to receive a determined volume of at least one propellant charge (60), characterized in that said wad (30) is a single-piece plastic part, in that said wad (30) comprises one or more polymer(s) including one or more polybutylene succinate polymer(s), in that said wad (30) comprises calcium carbonate, in that the mass fraction of said polymer(s) in said wad (30) is greater than or equal to 70%, in that the mass fraction of calcium carbonate in said wad (30) is greater than or equal to 6.5%,and in that the polybutylene succinate polymer(s) is / are the majority by mass in said fluff (30).,

2. Filler (30) according to claim 1, characterized in that the mass fraction of polymer(s) is greater than or equal to 70% and less than or equal to 90%.

3. A wad (30) according to either of claims 1 and 2, characterized in that the polybutylene succinate polymer(s) represents(s) at least 70% by mass of the wad (30).

4. A filler (30) according to any one of claims 1 to 3, characterized in that the calcium carbonate comprises calcium carbonate surface-treated with a mixture of (poly)carboxylic acid(s) and / or one or more acid anhydrides of said (poly)carboxylic acid(s), and / or one or more salts of said (poly)carboxylic acid(s) and / or one or more salts of said acid anhydride(s).

5. A wad (30) according to any one of claims 1 to 4, characterized in that the wad has a density ranging from 1.20 g / cm3 to 1.50 g / cm3.

6. Padding (30) according to any one of claims 1 to 5, characterized in that the first part (31) is a skirt comprising longitudinal slots.

7. A wad (30) according to any one of claims 1 to 6, ca- characterized in that the first part (31) comprises a proximal part (31a) and a distal part (31b), and in that the thickness of the wall (31c) of the first part (31) decreases from its proximal part (31a) towards its distal part (31b).

8. A wad (30) according to any one of claims 1 to 7, characterized in that the wad (30) comprises a separating wall (37) separating a bottom (35) of the first part (31) of the wad (30) from a bottom (36) of the second part (33) of the wad (30), said separating wall (37) having a thickness (eint) greater than or equal to 2.00 mm.

9. Wadding (30) according to any one of claims 1 to 8, characterized in that the height (H1) of the first part (31) is greater than or equal to 5 times the height (H2) of the second part (33).

10. Shot or bullet cartridge (10) comprising an at least partly biodegradable wad (30) for shot or bullet cartridge according to any one of claims 1 to 9.

11. A method of manufacturing an at least partly biodegradable wad (30) for a shot or bullet cartridge, characterized in that it comprises the following steps: - i) preparing a mixture comprising one or more polymer(s) including one or more polybutylene succinate polymer(s), and further comprising a primary compound comprising calcium carbonate, the mass fraction of said polymer(s) in said mixture is greater than or equal to 70%, the mass fraction of calcium carbonate in said mixture is greater than or equal to 6.5%, and the polybutylene succinate polymer(s) is / are the majority by mass in said mixture; -ii) implementing by heating said mixture from step i) in a single molding step for molding a primary wad for a shot or bullet cartridge with a mold assembly comprising a primary wad imprint for a shot or bullet cartridge;- iii) recovery of the primary cartridge wad molded from said mixture; - optionally a step iv) of preparing one or more longitudinal slot(s) in the first part of the primary cartridge wad.;

12. Method according to claim 11, characterized in that the polybutylene succinate polymer(s) represent(s) at least 70% by mass of the mixture from step i).

13. Method according to either of claims 11 and 12, characterized in that the polybutylene succinate polymer(s) has, or each has, a flexural modulus, measured with the ISO 178:2019 standard, less than or equal to 400 MPa.

14. Manufacturing method according to any one of claims 11 to 13, characterized in that the polybutylene succinate polymer(s) has, or each has, a Hot Melt Index greater than or equal to 1 g / 10 min and less than or equal to 10 g / 10 min, measured at a temperature of 190°C, under a mass of 2.16 kg, and according to standard ISO 1133:2011.

15. Manufacturing method according to any one of claims 11 to 14, characterized in that the calcium carbonate of the primary compound comprises calcium carbonate surface-treated with a mixture of (poly)carboxylic acid(s) and / or one or more acid anhydrides of said (poly)carboxylic acid(s), and / or one or more salts of said (poly)carboxylic acid(s) and / or one or more salts of said acid anhydride(s), and in that the primary compound comprises one or more biodegradable polymer(s) mixed with said calcium carbonate.

16. A method of manufacturing a shot or bullet cartridge (10) according to claim 10, characterized in that it comprises the following steps: - providing a wad (30) for a cartridge according to any one of claims 1 to 9 and a cartridge (10) comprising a case (20), said case (20) comprising a primer (17), - placing a determined volume of a propellant charge (50) inside the case (20), - placing the wad (30) for a shot or bullet cartridge in the case (20), - placing one or more projectiles (50) in the case (20), - crimping the cartridge (10), and - recovering the resulting cartridge (10).

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