FR3146479A1 - Biodegradable composite thermoplastic material with fibrous reinforcement based on casein and/or caseinate - Google Patents

Abstract

Biodegradable composite thermoplastic material with fibrous reinforcement that can be used industrially, possibly in the form of granules and possibly edible, as well as its manufacturing process, comprising: a) between 80% and 99.6% or between 25% and 50% of casein and/or caseinate and/or their mixtures; b) between 0.1% and 4% of water; c) between 0.1% and 25% of at least one plasticizer c) different from b); d) between 0.1% and 15%, or between 0.1% and 40% of at least one reinforcement derived from the plant kingdom or a compound of the plant kingdom or derived from the animal kingdom or a compound of the animal kingdom or derived from the mineral kingdom or a compound of the mineral kingdom or their mixtures; (e) between 0.1% and 7% of at least one additive chosen from colorants, protein coagulants, anti-caking agents, glidants, or mixtures thereof.

Description

Biodegradable composite thermoplastic material with fibrous reinforcement based on casein and/or caseinate

The field of the invention is that of composite, biodegradable thermoplastic materials based on casein and/or caseinate.

1. entre 80% et 99,6% de caséine et/ou de caséinate et/ou leurs mélanges, de préférence entre 85% et 93% ;
2. entre 0,1% et 4% d’eau, de préférence entre 1,5% et 3% ;
3. entre 0,1% et 25% d’au moins un plastifiant différent de b), de préférence entre 10% et 15% ;
4. entre 0,1% et 15% d’au moins un renfort issu du règne végétal ou du règne animal ou du règne minéral ou leurs mélanges, de préférence entre 5% et 10,5% ;
5. entre 0,1% et 7% d’au moins un additif, de préférence entre 2% et 5,5%.

In particular, the present invention relates to a biodegradable composite thermoplastic material with fibrous reinforcement called “first typical composition” comprising:

1. between 80% and 99.6% of casein and/or caseinate and/or their mixtures, preferably between 85% and 93%;
2. between 0.1% and 4% water, preferably between 1.5% and 3%;
3. between 0.1% and 25% of at least one plasticizer different from b), preferably between 10% and 15%;
4. between 0.1% and 15% of at least one reinforcement from the plant kingdom or the animal kingdom or the mineral kingdom or their mixtures, preferably between 5% and 10.5%;
5. between 0.1% and 7% of at least one additive, preferably between 2% and 5.5%.

1. entre 25% et 50% de caséine et/ou de caséinate et/ou leurs mélanges, de préférence entre 35% et 40% ;
2. entre 0,1% et 4% d’eau, de préférence entre 1,5% et 3% ;
3. entre 0,1% et 25% d’au moins un plastifiant différent de b), de préférence entre 10 et 15% ;
4. entre 0,1% et 40% d’au moins un renfort issu du règne végétal ou du règne animal ou du règne minéral ou leurs mélanges, de préférence entre 7% et 33% ;
5. entre 0,1% et 7% d’au moins un additif, de préférence entre 2% et 5,5%.

The invention also relates to a biodegradable composite thermoplastic material with fibrous reinforcement called “second type composition” comprising:

1. between 25% and 50% casein and/or caseinate and/or their mixtures, preferably between 35% and 40%;
2. between 0.1% and 4% water, preferably between 1.5% and 3%;
3. between 0.1% and 25% of at least one plasticizer different from b), preferably between 10 and 15%;
4. between 0.1% and 40% of at least one reinforcement from the plant kingdom or the animal kingdom or the mineral kingdom or their mixtures, preferably between 7% and 33%;
5. between 0.1% and 7% of at least one additive, preferably between 2% and 5.5%.

The invention also relates to the biodegradable composite thermoplastic material with fibrous reinforcement in different forms, in particular in the form of granules constituting a raw material for its transformation into various products and objects, such as molded articles, etc.

The invention finally relates to a method for manufacturing a biodegradable composite thermoplastic material with fibrous reinforcement.

Technological background

The planned end of non-renewable resources and the negative impact of their use on the environment require the rapid development of non-polluting alternative solutions.

In the field of plastics, new biodegradable materials are being developed. These new materials can be made from polymers of natural origin. For example, plant proteins, such as corn or soy proteins, or animal proteins, such as casein, can be used. Casein stands out because this protein from milk is available in large quantities and has good biodegradability.

Furthermore, the need for fibre-reinforced composite materials is growing, particularly due to the performance, particularly resistance, that these materials offer in relation to their low weight.

However, due to costs and implementation difficulties, the integration of biodegradable fibrous reinforcement, in long, short or loaded fibres, in biodegradable thermoplastic composites, is not developed on an industrial level.

Goals

In this context, the present invention aims to provide a biodegradable composite thermoplastic material with fibrous reinforcement, based on casein and/or caseinate which can be exploited industrially, that is to say in particular transformable into a semi-finished product or into a finished product, simple or complex shape, by techniques such as flat die extrusion, extrusion-blow molding, extrusion-inflation, pultrusion, infusion, solvent route, calendering, injection, thermoforming, sintering, molding (of all types), stamping, draping, spinning, filament winding or machining.

Brief description of the invention

1. entre 80% et 99,6% de caséine et/ou de caséinate et/ou leurs mélanges, de préférence entre 82% et 96%, et, plus préférentiellement encore, entre 85% et 93% ;
2. entre 0,1 % et 4% d’eau, de préférence entre 1% et 3,5%, et, plus préférentiellement encore, entre 1,5% et 3% ;
3. entre 0,1% et 25% d’au moins un plastifiant différent de b), de préférence entre 5% et 20%, et, plus préférentiellement encore, entre 10% et 15% ;
4. entre 0,1% et 15% d’au moins un renfort issu du règne végétal ou du règne animal ou du règne minéral ou leurs mélanges, de préférence entre 2% et 13,5% et, plus préférentiellement encore, entre 5% et 10,5% ;
5. entre 0,1% et 7% d’au moins un additif, de préférence entre 1% et 6,5%, et, plus préférentiellement encore, entre 2% et 5,5%.

The invention relates firstly to a biodegradable composite thermoplastic material with fibrous reinforcement called “first typical composition” characterized in that it comprises:

1. between 80% and 99.6% of casein and/or caseinate and/or their mixtures, preferably between 82% and 96%, and, more preferably still, between 85% and 93%;
2. between 0.1% and 4% water, preferably between 1% and 3.5%, and, more preferably still, between 1.5% and 3%;
3. between 0.1% and 25% of at least one plasticizer different from b), preferably between 5% and 20%, and, more preferably still, between 10% and 15%;
4. between 0.1% and 15% of at least one reinforcement from the plant kingdom or the animal kingdom or the mineral kingdom or their mixtures, preferably between 2% and 13.5% and, even more preferably, between 5% and 10.5%;
5. between 0.1% and 7% of at least one additive, preferably between 1% and 6.5%, and, more preferably still, between 2% and 5.5%.

1. entre 25% et 50% de caséine et/ou de caséinate et/ou leurs mélanges, de préférence entre 30% et 45%, et, plus préférentiellement encore, entre 35% et 40% ;
2. entre 0,1 % et 4% d’eau, de préférence entre 1% et 3,5%, et, plus préférentiellement encore, entre 1,5% et 3% ;
3. entre 0,1% et 25% d’au moins un plastifiant différent de b), de préférence entre 5% et 20%, et, plus préférentiellement encore, entre 10% et 15% ;
4. entre 0,1% et 40% d’au moins un renfort issu du règne végétal ou du règne animal ou du règne minéral ou leurs mélanges, de préférence entre 5% et 35% et, plus préférentiellement encore, entre 7% et 33% ;
5. entre 0,1% et 7% d’au moins un additif, de préférence entre 1% et 6,5%, et, plus préférentiellement encore, entre 2% et 5,5%.

The invention secondly relates to a biodegradable composite thermoplastic material with fibrous reinforcement called “second type composition” characterized in that it comprises:

1. between 25% and 50% of casein and/or caseinate and/or their mixtures, preferably between 30% and 45%, and, more preferably still, between 35% and 40%;
2. between 0.1% and 4% water, preferably between 1% and 3.5%, and, more preferably still, between 1.5% and 3%;
3. between 0.1% and 25% of at least one plasticizer different from b), preferably between 5% and 20%, and, more preferably still, between 10% and 15%;
4. between 0.1% and 40% of at least one reinforcement from the plant kingdom or the animal kingdom or the mineral kingdom or their mixtures, preferably between 5% and 35% and, even more preferably, between 7% and 33%;
5. between 0.1% and 7% of at least one additive, preferably between 1% and 6.5%, and, more preferably still, between 2% and 5.5%.

The invention finally relates to a method for manufacturing a biodegradable composite thermoplastic material with fibrous reinforcement.

Definitions

By " thermoplastic " we mean, for example, a material which becomes malleable and pliable above a given temperature, the glass transition temperature Tg, but which becomes hard again below this Tg, these transformations being reversible.

By " composite " is meant, for example, a material composed of at least one immiscible material different from the main material and whose mechanical properties complement each other advantageously for certain uses.

By " biodegradable " we mean, for example, a material that can be decomposed by the action of micro-organisms (bacteria, fungi, algae, etc.). The result of this decomposition is the formation of water, CO₂ and/or methane and possibly by-products (residues, new biomass) that are non-toxic to the environment. This is, for example, a biodegradable material according to the French and European standard NF EN 13432.

By " reinforcement " we mean, for example, the reinforcement taking up most of the mechanical forces composed of long or continuous fibers or short fibers or fillers or their mixtures.

By " between x and y " we mean, for example, that the limits x and y are included in the interval [ x, y ].

By " caseinate " is meant, for example, a water-soluble compound, preferably of calcium, potassium, ammonium, sodium or magnesium, obtained by drying a basic solution of casein.

By " compound " we mean, for example, a chemical species formed by the combination of two or more elements.

By " water-soluble " we mean, for example, that which dissolves in water.

By " granule " we mean, for example, pieces of material of small dimensions, that is to say with a diameter of less than 1 cm and a length not exceeding 3 cm.

By " plasticizer " we mean, for example, a substance that lowers the glass transition temperature Tg of the material.

By " edible " we mean, for example, that which can be eaten without risk to humans.

By " hydrophilic " is meant, for example, a compound having an affinity for water and tending to dissolve in it. Typically, this is a compound having polar groups capable of forming hydrogen bonds.

By " mixer " we mean, for example, a device used to mix different substances.

By " doser " we mean, for example, a powder or liquid filling machine.

By " sintering " we mean, for example, the consolidation by the action of heat of a granular agglomerate consisting of powder and more or less compact, with or without fusion of one or more of its constituents.

The proportions of the various constituents a), b), c), d) and e) are expressed as a percentage (%) by mass relative to the total mass of the thermoplastic material at room temperature.

Detailed description of the invention

The biodegradable composite thermoplastic material with fibrous reinforcement known as the “first typical composition” comprises a) between 80% and 99.6%, preferably between 82% and 96%, and, more preferably still, between 85% and 93%, of casein and/or caseinate or their mixtures.

Casein is a protein derived from milk that is poorly soluble in water. It is mainly obtained by precipitation by adding an acid (acid casein) or rennet (rennet casein) to milk. Casein consists of a mixture of α-casein, β-casein and κ-casein with molar masses between 19,000 and 25,000 g/mol.

According to one embodiment of the biodegradable composite thermoplastic material with fibrous reinforcement called “first typical composition”, a) comprises at least one casein or a mixture of caseins.

According to another embodiment of the biodegradable composite thermoplastic material with fibrous reinforcement called “first typical composition”, a) comprises at least one caseinate, for example a sodium caseinate, or a mixture of caseinates.

According to another embodiment of the biodegradable composite thermoplastic material with fibrous reinforcement called “first typical composition”, a) comprises a casein or a mixture of caseins and at least one caseinate or a mixture of caseinates.

The biodegradable composite thermoplastic material with fibrous reinforcement called “first typical composition” comprises b) between 0.1% and 4%, preferably between 1% and 3.5%, and, more preferably still, between 1.5 and 3%, of water. The water acts as a plasticizer which must be distinguished from the plasticizer c) entering into the composition of the biodegradable composite thermoplastic material with fibrous reinforcement called “first typical composition” according to the invention.

The latter in fact comprises c) between 0.1% and 25%, preferably between 5% and 20%, and, even more preferably, between 10% and 15%, of at least one plasticizer c) different from b).

This plasticizer c) may be chosen from polyols, glycerol acetates, glycerol propionates and mixtures thereof. Examples of polyols include glycerol, hexanetriol, glycols, including ethylene glycol, and sugars and their derivatives. Examples of sugars include disaccharides, such as maltose, lactose, sucrose and monosaccharides such as fructose. Sugar derivatives include their hydrogenated derivatives, such as sorbitol, maltitol, mannitol and xylitol, or the transformation products of these hydrogenated derivatives, such as sorbitan.

According to one embodiment of the biodegradable composite thermoplastic material with fibrous reinforcement called “first typical composition”, the plasticizer c) is chosen from glycerol, sorbitol, mannitol, ethylene glycol and their mixtures. Preferably, the plasticizer c) is glycerol. The plasticizer c) may contain residual water. The plasticizer c) makes it possible to reduce the viscosity of the product by increasing the mobility of the molecular chains. Advantageously, the plasticizer c) is a hydrophilic plasticizer.

The biodegradable composite thermoplastic material with fibrous reinforcement called “first typical composition” comprises d) between 0.1% and 15%, preferably between 2% and 13.5%, and, even more preferably, between 5% and 10.5%, of at least one reinforcement from the plant kingdom or the animal kingdom or the mineral kingdom or their mixtures. Among the reinforcements from the plant kingdom, mention may be made of fibers which may come from bast fiber plants (such as flax and hemp), leaves (such as sisal), fruits (such as coir), grasses (such as arundo donax), straw (such as wheat), wood (such as that of conifers and hardwoods) and pseudo-stems (such as banana trees). Among the reinforcements from the animal kingdom, mention may be made of fibers from hair (such as animal fleece) and secretions (such as silk). Among the reinforcements from the mineral kingdom, we can cite fibers mainly made up of silica or basalt.

According to one embodiment of the biodegradable composite thermoplastic material with fibrous reinforcement called “first typical composition”, the reinforcement d) is derived from a compound of the plant kingdom, or derived from a compound of the animal kingdom, or derived from a compound of the mineral kingdom, or their mixtures.

The biodegradable composite thermoplastic material with fiber reinforcement called “first typical composition” comprises e) between 0.1% and 7%, preferably between 1% and 6.5%, and, even more preferably, between 2% and 5.5%, of at least one additive chosen from dyes, protein coagulants, anti-caking agents, slip agents and mixtures thereof. Among the coagulants, mention may be made of citric acid and acetic acid. Among the anti-caking agents, mention may be made of colloidal silica. Among the slip agents, mention may be made of polyethylene glycols. Among the release agents, mention may be made of polyvinyl alcohol.

The biodegradable composite thermoplastic material with fiber reinforcement called "second type composition" comprises a) between 25% and 50%, preferably between 30% and 45%, and, more preferably still, between 35% and 40%, of casein and/or caseinate or their mixtures. The casein consists of a mixture of α-casein, β-casein and κ-casein having molar masses of between 19,000 and 25,000 g/mol.

According to one embodiment of the biodegradable composite thermoplastic material with fibrous reinforcement called “second typical composition”, a) comprises at least one casein or a mixture of caseins.

According to another embodiment of the biodegradable composite thermoplastic material with fibrous reinforcement called “second typical composition”, a) comprises at least one caseinate, for example a sodium caseinate, or a mixture of caseinates.

According to another embodiment of the biodegradable composite thermoplastic material with fibrous reinforcement called “second typical composition”, a) comprises a casein or a mixture of caseins and at least one caseinate or a mixture of caseinates.

The biodegradable composite thermoplastic material with fibrous reinforcement called “second typical composition” comprises b) between 0.1% and 4%, preferably between 1% and 3.5%, and, more preferably still, between 1.5 and 3%, of water. The water acts as a plasticizer which must be distinguished from the plasticizer c) entering into the composition of the biodegradable composite thermoplastic material with fibrous reinforcement called “second typical composition” according to the invention.

The latter in fact comprises c) between 0.1% and 25%, preferably between 5% and 20%, and, even more preferably, between 10% and 15%, of at least one plasticizer c) different from b).

This plasticizer c) may be chosen from polyols, glycerol acetates, glycerol propionates and mixtures thereof. Examples of polyols include glycerol, hexanetriol, glycols, including ethylene glycol, and sugars and their derivatives. Examples of sugars include disaccharides, such as maltose, lactose, sucrose and monosaccharides such as fructose. Sugar derivatives include their hydrogenated derivatives, such as sorbitol, maltitol, mannitol and xylitol, or the transformation products of these hydrogenated derivatives, such as sorbitan.

According to one embodiment of the biodegradable composite thermoplastic material with fiber reinforcement called “second standard composition”, the plasticizer c) is chosen from glycerol, sorbitol, mannitol, ethylene glycol and their mixtures. Preferably, the plasticizer c) is glycerol. The plasticizer c) may contain residual water. The plasticizer c) makes it possible to reduce the viscosity of the product by increasing the mobility of the molecular chains. Advantageously, the plasticizer c) is a hydrophilic plasticizer.

The biodegradable composite thermoplastic material with fibrous reinforcement known as the “second standard composition” comprises d) between 0.1% and 40%, preferably between 5% and 35%, and, even more preferably, between 7% and 33%, of at least one reinforcement from the plant kingdom or the animal kingdom or the mineral kingdom or their mixtures. Among the reinforcements from the plant kingdom, mention may be made of fibers which may come from bast fiber plants (such as flax and hemp), leaves (such as sisal), fruits (such as coir), grasses (such as arundo donax), straw (such as wheat), wood (such as that of conifers and broadleaf trees) and pseudo-stems (such as banana trees). Among the reinforcements from the animal kingdom, mention may be made of fibers from hair (such as animal fleece) and secretions (such as silk). Among the reinforcements from the mineral kingdom, we can cite fibers mainly made up of silica or basalt.

According to one embodiment of the biodegradable composite thermoplastic material with fibrous reinforcement known as the “second typical composition”, the reinforcement d) is derived from a compound of the plant kingdom, or from a compound of the animal kingdom, or from a compound of the mineral kingdom, or their mixtures.

The biodegradable composite thermoplastic material with fiber reinforcement called “second typical composition” comprises e) between 0.1% and 7%, preferably between 1% and 6.5%, and, even more preferably, between 2% and 5.5%, of at least one additive chosen from dyes, protein coagulants, anti-caking agents, slip agents and mixtures thereof. Among the coagulants, mention may be made of citric acid and acetic acid. Among the anti-caking agents, mention may be made of colloidal silica. Among the slip agents, mention may be made of polyethylene glycols. Among the release agents, mention may be made of polyvinyl alcohol.

1. de caséine et/ou caséinate,
2. d’eau,
3. de glycérol,
4. de fibre d’acacia,
5. d’acide oléique,

According to a particular embodiment, the biodegradable composite thermoplastic material with fibrous reinforcement called "first type composition" or "second type composition" is composed solely of components that can be used in the agri-food industry, i.e. components included in the Codex Alimentarius. In this case, the biodegradable composite material with fibrous reinforcement is edible. For example, when the biodegradable composite thermoplastic material with fibrous reinforcement is composed of:

1. of casein and/or caseinate,
2. of water,
3. of glycerol,
4. of acacia fiber,
5. oleic acid,

The biodegradable composite thermoplastic material with fiber reinforcement is edible.

The biodegradable composite thermoplastic material with fibrous reinforcement called “first type composition” or “second type composition” may be in the form of granules. The invention therefore also relates to the granules of the biodegradable composite thermoplastic material with fibrous reinforcement called “first type composition” or “second type composition” described above which, in a particular embodiment as described above, may be edible.

The invention also relates to a product or object that can be obtained after transformation by flat die extrusion, extrusion-blow molding, extrusion-inflation, pultrusion, infusion, solvent route, calendering, injection, thermoforming, sintering, molding (of all types), stamping, draping, spinning, filament winding or machining of the biodegradable composite thermoplastic material with fiber reinforcement called "first type composition" or "second type composition" as described above.

According to another of its aspects, the invention relates to a method of manufacturing the biodegradable composite material with fibrous reinforcement called “first type composition” or “second type composition” as described above.

This method preferably comprises the following steps:

E1. implementation of a mixer;

E2. introduction of compounds a) to e) into the mixer;

E3. introduction of the mixture obtained into a dosing device;

E4. compaction of the dosed mixture;

E5. sintering of the compacted mixture;

E6. possibly surface treatment of the sintered material;

E7. possibly grinding or cutting the sintered material into granules.

Advantageously, step E1 consists of operating the mixer with the following parameters: rotation speed between 60 and 180 rpm, at a temperature between 10 and 40°C.

Step E2 preferably consists in introducing, at the same time or successively, preferably successively, in a first step, at least a portion of compounds a) to e), in solid form, advantageously in powder form, and, in a second step, at least a portion of compounds a) to e), in liquid form. In a preferred embodiment, the compounds in solid form, advantageously in powder form, are compounds a), d) and e); while the compounds in liquid form are compounds b) and c).

Step E3 consists of pouring the contents of the mixing bowl into the dosing hopper one or more times.

Step E4 consists of recovering the measured mixture and subjecting it to a pressure force, using a press for example, to eliminate some of the air it may contain. The more air that needs to be expelled, the higher the pressure force will need to be.

Claims (10)

Biodegradable composite thermoplastic material with fibrous reinforcement (first typical composition) comprising:
(a) between 80% and 99.6%, preferably between 82% and 96%, and, more preferably still, between 85% and 93%, of casein or caseinate or of a mixture of casein or of a mixture of caseinates;
b) between 0.1% and 4%, preferably between 1% and 3.5%, and, more preferably still, between 1.5 and 3%, of water;
c) between 0.1% and 25%, preferably between 5% and 20%, and, more preferably still, between 10% and 15%, of at least one plasticizer c) different from b);
(d) between 0.1% and 15%, preferably between 2% and 13.5%, and, more preferably still, between 5% and 10.5%, of at least one reinforcement from the plant kingdom or the animal kingdom or the mineral kingdom or their mixtures;
e) between 0.1% and 7%, preferably between 1% and 6.5%, and, more preferably still, between 2% and 5.5%, of at least one additive chosen from colorants, protein coagulants, anti-caking agents, slip agents, or mixtures thereof.
The proportions of the various constituents a), b), c), d) and e) are expressed as a percentage (%) by mass relative to the total mass of the thermoplastic material at room temperature. Biodegradable composite thermoplastic material with fibrous reinforcement (second typical composition) comprising:
(a) between 25% and 50%, preferably between 30% and 45%, and, even more preferably, between 35% and 40%, of casein or caseinate or of a mixture of casein or of a mixture of caseinates;
b) between 0.1% and 4%, preferably between 1% and 3.5%, and, more preferably still, between 1.5 and 3%, of water;
c) between 0.1% and 25%, preferably between 5% and 20%, and, more preferably still, between 10% and 15%, of at least one plasticizer c) different from b);
(d) between 0.1% and 40%, preferably between 5% and 35%, and, even more preferably, between 7% and 33% of at least one reinforcement from the plant kingdom or the animal kingdom or the mineral kingdom or their mixtures;
e) between 0.1% and 7%, preferably between 1% and 6.5%, and, more preferably still, between 2% and 5.5%, of at least one additive chosen from colorants, protein coagulants, anti-caking agents, slip agents, or mixtures thereof.
The proportions of the various constituents a), b), c), d) and e) are expressed as a percentage (%) by mass relative to the total mass of the thermoplastic material at room temperature. Material according to claim 1 or 2 characterized in that a) comprises at least one casein and at least one caseinate or a mixture of caseinates. Material according to claim 1 or 2 characterized in that a) comprises a mixture of casein and at least one caseinate or a mixture of caseinates. Material according to claim 1 or 2, characterized in that the plasticizer c) is chosen from polyols, glycerol acetates, glycerol propionates, and their mixtures, with c) preferably being glycerol. Material according to claim 1 or 2, characterized in that the reinforcement d) comes from a compound of the plant kingdom, or from a compound of the animal kingdom, or from a compound of the mineral kingdom, or their mixtures, the compound being a chemical species, formed of at least two chemical elements. Material according to one of claims 1 to 6, in that it is edible. Granules of the material according to one of claims 1 to 7, in particular for the manufacture of products or objects. Product or object capable of being obtained after transformation by flat die extrusion, extrusion-blow molding, extrusion-inflation, pultrusion, infusion, solvent route, calendering, injection, thermoforming, sintering, molding (of all types), stamping, draping, spinning, filament winding or machining of the biodegradable composite thermoplastic material with fiber reinforcement according to any one of claims 1 to 7, or of the granules according to claim 8. Method for manufacturing a biodegradable composite thermoplastic material with fibrous reinforcement according to any one of claims 1 to 7, characterized in that it comprises the following steps:
E1. implementation of a mixer;
E2. introduction of compounds a) to e) into the mixer;
E3. introduction of the mixture obtained into a dosing device;
E4. compaction of the dosed mixture;
E5. sintering of the compacted mixture;
E6. possibly surface treatment of the sintered material;
E7. possibly grinding or cutting the sintered material into granules;
step E2 preferably consisting in introducing, at the same time or successively, preferably successively, in a first step, at least a portion of compounds a) to e), in solid form, advantageously in powder form, and, in a second step, at least a portion of compounds a) to e), in liquid form.