WO2002046295A1

WO2002046295A1 - Expanded product made of biodegradable material and method and installation for continuously making same

Info

Publication number: WO2002046295A1
Application number: PCT/FR2001/003861
Authority: WO
Inventors: Daniel Durand; Gilles Souveton; Pascal Tabouillot; Pierre Reynes
Original assignee: Clextral; Ulice
Priority date: 2000-12-06
Filing date: 2001-12-06
Publication date: 2002-06-13
Also published as: AU2002216190A1

Abstract

The invention concerns an expanded product made of biodegradable material designed for other than food purposes, characterised in that it is obtained by extrusion cooking of a ground native plant vegetable material whereof the average particle size ranges between 1 νm and 1.5 mm and whereof the amylose/amylopectin ratio is not more than 30 %. The invention also concerns a method and an installation for continuously making such an expanded product from biodegradable material, such as for example a cushioning or isolating material.

Description

Expanded product in biodegradable material and process and installation for continuous manufacturing of such a product.

The present invention relates to an expanded product made of biodegradable material intended for use other than for food use, such as, for example, a cushioning product intended for packaging or an insulation product.

The invention also relates to a method and an installation for manufacturing such a product.

In the field of packaging, many cushioning and / or insulation products are used for example to hold and protect objects in cases and these products are in the form of washers or chips in the form of S or eight or in the form of small cylinders. Generally, this type of product is made of expanded polystyrene, that is to say a non-biodegradable material which has major drawbacks for the environment.

In fact, these products induce significant visual pollution since expanded polystyrene is not at all assimilated by the environment and this expanded polystyrene comes from petrochemicals and therefore from non-renewable energy.

To avoid these drawbacks, processes for the production of biodegradable stalling products obtained from plants are known.

US-A-5,153,037 describes a biodegradable expanded product made from a modified flour containing at least 40% by weight of amylose and at least 2% by weight of an inorganic salt soluble in it. water. This flour is modified by the addition of 10% propylene oxide and 2% of a metal salt. The mixture is extruded at a temperature between 150 and 250 ° C and has a rate of 21% of total humidity. The flours used in this process require transformation, for example by esterification, etherification, oxidation or acid hydrolysis and, in addition, the incorporation of alkali or alkaline earth metal salts.

EP-A-0436 689 also discloses a process for the preparation of a biodegradable expanded material obtained from the mixture between a synthetic polymer and a material comprising starch. This mixture is carried out in proportions varying from 1/9 to 9/1 and there is also added an expanding agent such as for example a sodium bicarbonate and a plasticizer, respectively in the proportions of 8 to 30%. The product obtained has a closed pore structure and a density of between 0.1 and 0.3 g / cm ³ .

Also known from US-A-5,208,267 is a process for developing a biodegradable expanded material based on starch. The starch is extruded in the presence of polyethylene glycol and a nucleating agent such as silica, the role of which is to promote the appearance of starch pores which will be created around the silica grains, thereby facilitating expansion.

These different processes cause chemical modifications of the raw material and therefore require the addition of elements to the basic product, such as for example blowing agents and metal salts to modify the flour.

The object of the invention is to provide an expanded product made of biodegradable material intended for use other than food use as well as a process and an installation for the continuous production of this type of product which avoid the drawbacks mentioned above.

The subject of the invention is therefore an expanded product made of biodegradable material intended for use other than food use, characterized in that it is obtained by cooking-extrusion of a native ground vegetable material whose average particle size is between 1μm and 1.5mm and whose amylose to amylopectin ratio is less than or equal to 30%.

According to other characteristics of the invention:

- the average particle size of the ground plant material is preferably between 1 and 500 μm, - the ground plant material consists of flour and / or cereal semolina,

the product has a density less than or equal to 100 g / l, preferably 30 g / l and advantageously between 9 and 15 g / l,

- the product has a resilience greater than 50%, in particular at least 85%, the product has a starchy material content of between approximately 70 and 100% by weight, in particular between approximately 55 and 94% by weight and more particularly between approximately 88 and 93% by weight,

- Extrusion cooking is carried out in an extrusion machine fitted with at least one screw driven in rotation at a speed greater than or equal to 600 rpm.

The subject of the invention is also a process for the continuous production of an expanded product made of biodegradable material intended for use other than for food use, characterized in that: - a baking-extrusion machine is introduced, comprising minus a screw driven in rotation, a native ground vegetable material whose average particle size is between 1 μm and 1.5 mm and whose amylose to amylopectin ratio is less than or equal to 30%, and

- At least one thermomechanical working step is carried out on the plant material by driving said screw in rotation at a speed greater than or equal to 600 rpm to obtain said product.

According to another characteristic of the invention, said thermomechanical working step comprises:

- at least one phase of feeding and transfer of the crushed plant material,

- at least one intermediate kneading phase with shearing of the plant material, mixing and cooking of this plant material at a temperature below or equal to 220 ° C.,

- a compression phase, and, - a product extrusion and expansion phase.

The subject of the invention is also a plant for the continuous production of an expanded product made of biodegradable material intended for use other than food use, characterized in that it comprises a cooking-extrusion machine for plant material milled native whose average particle size is between 1 μm and 1.5 mm and whose amylose to amylopectin ratio is less than or equal to 30%, said cooking-extrusion machine comprising at least one screw driven in rotation in a sheath of allon shape gée at a speed greater than or equal to 600 rpm and determining at least one thermomechanical working zone of the plant material to obtain said product.

Other characteristics and advantages of the invention will appear during the description which follows, given by way of example and made with reference to the appended drawings, in which:

- Fig. 1 is a schematic view of an installation for the continuous production of an expanded product made of biodegradable material, in accordance with the invention, - FIG. 2 is a view in longitudinal section of a cooking-extrusion machine of the manufacturing installation according to the invention,

- Fig. 3 is a sectional view along line 3-3 of FIG. 2

- Fig. 4 represents curves showing the relationship between the speed of rotation of the screws and the apparent density of the product obtained, - FIG. 5 shows a view of a wedging product in the form of

S. The installation shown schematically in the figures is intended for the continuous manufacture of an expanded product made of biodegradable material for use other than for food use, such as for example a cushioning or insulation product, used in particular for maintaining and protecting objects in crates.

In general, the wedging products are in the form of washers or S-shaped crisps (see Fig. 5) or eight or in the form of small cylinders. The insulation products are in the form of plates. The biodegradable product according to the invention is obtained by cooking-extrusion in an extrusion machine provided with at least one screw driven in rotation at a speed greater than or equal to 600 rpm from a native ground vegetable material, the average particle size is between 1 μm and 1.5 mm and the amylose to amylopectin ratio is less than or equal to 30%. Preferably, the average particle size of the ground vegetable material is between 1 and 500 μm and the product obtained has a mass volume less than or equal to 100g / l, preferably less than 30g / l and advantageously between 9 and 15g / l.

This product has a resilience greater than 50%, in particular at least 85%. In addition, the product has a starch content between about 70 and 100% by weight, especially between about 85 and 94% by weight and more particularly between about 88 and 93% by weight.

Preferably, the plant material is a cereal material derived from one or more of the following cereals: wheat, corn, rice, millet, millet, buckwheat, rye, oats, spelled or barley and in particular a flour and / or a semolina cereal.

The plant material used to obtain the expanded product of the invention may be a non-cereal plant material obtained in particular from potato, lupine, cassava, soybeans, peas, quinoa or a mixture one or more of these plants.

In the following description, a cereal material based on wheat and / or corn will be used as vegetable material, another cereal or non-cereal material that can be used to obtain the setting product according to the invention. It should be noted that the term biodegradable expanded product based on flour and / or starch, a product whose content by weight of vegetable raw materials (flour and / or starch) is greater than 70%.

By starchy material is meant the dry vegetable matter resulting from the transformation by the process, of flour and / or starch. This ^“” term of starchy material, cereal or not, will be used to define the composition of the biodegradable expanded cushioning product of the invention obtained at the end of the manufacturing process. .

Wheat or corn flour and semolina differ mainly in their particle size, but also by that nature of certain constituents and by way of example, wheat or corn flour or semolina has the following weight composition:

- 0 to 20% water - 0 to 85% of carbohydrate compounds,

- 0 to 30% protein,

- 0 to 10% fatty acids,

- 0 to 5% of minerals, 5 - 0 to 20% of fibers.

In general, the method consists in introducing into a cooking-extrusion machine comprising at least one screw driven in rotation, the native ground vegetable material mentioned above and in carrying out at least one thermomechanical working step on the vegetable material by 0 driving said screw in rotation at a speed greater than 600 rpm to obtain the product.

As shown in Figures 1 to 3, the thermomechanical working step of the native crushed plant material is carried out in a machine designated as a whole by the reference 1. 5 In the embodiment shown in the figures, the machine 1 of cooking-extrusion is a machine with two screws, this machine can also be constituted by a single-screw driven in rotation inside a sheath of elongated shape.

The extrusion machine 1 is of the type with two co-rotating and 0 co-penetrating screws and comprises two screws 11 and 12 driven in rotation around their axes by a motor and a reduction gear, not shown, inside An elongated enclosure forming a sheath 13 which envelops them.

Generally, the screws 11 and 12 are provided with helical threads which mesh with one another and the internal wall of the sheath 5 13 forms two intersecting cylindrical lobes, respectively 11a and 12a, with an internal diameter slightly greater than the external diameter of the threads of the screws 11 and 12.

These threads are nested one inside the other and the two screws 11 and 12 are driven at the same speed of rotation and in the same direction of o so that the two screws. are identical, the threads being simply offset from each other. The screws 11 and 12 shown in FIG. 3 advantageously consist of splined shafts, 14 and 15 respectively, on which the screw sections are stacked.

The internal bore of these screw sections is provided with grooves corresponding to those of the shaft and the external part is provided with helical threads, the pitch of which differs according to the section considered for the transfer and treatment of the cereal material introduced into the upstream end of the sheath 13 of the extrusion machine 10.

It is thus possible to have a fairly large number of sections making it possible to vary the pitch, the depth, the number of threads and the length of each zone.

The extrusion machine determines a thermomechanical working area which includes:

- at least one feeding zone and at least one plant material transfer zone,

at least one intermediate kneading zone with shearing of the plant material, mixing and cooking of this plant material at a temperature less than or equal to 220 ° C.,

- a compression zone, and - a product extrusion and expansion zone.

In the embodiment shown in the figures, the machine 1 comprises:

- a zone A for feeding the cereal material,

- a zone B for transfer and compression of the cereal material,

a zone C for kneading the cereal material,

- a zone D for transferring the cereal material,

- a shear zone E of this cereal material, and

- a zone F for compressing this plant material, and - a zone G for extruding and expanding the product.

In the feed and transfer zone A, the sheath 13 is pierced, at its upstream end relative to the direction of flow of the material, of a supply orifice 16 connected to a gravimetric metering system for the cereal material constituted for example by a doser 2 with variable speed screw.

In this zone A, the screws 11 and 12 are provided with threads 17 with wide pitch in order to transport the cereal material introduced by the orifice 16 and which opens widely on the two screws 11 and 12 in order to distribute said material in these nets.

In this zone A, the sheath 13 of the machine 1 is equipped with heating means 18 for gradually bringing the cereal material from ambient temperature to a temperature of the order of 50 ° C, that is to say between 25 ° C and 75 ° C.

Thus, the cereal material constituted by of. the flour or semolina of wheat and / or corn is heated and transported downstream of the machine 1, that is to say to the zone B of transfer and compression.

In this zone B, the screws 11 and 12 comprise threads 19 with a tight pitch so as to compress the cereal material.

During its transfer to zone B, the cereal material is gradually brought to a temperature of the order of 120 ° C, that is to say between approximately 100 ° C and 130 ° C by heating means 20.

The cereal material then passes into the shear zone C.

In this zone C, the screws 11 and 12 consist of two-lobe mixing discs 21, as shown in FIG. 3. These mixing discs

21 allow a controlled passage downstream of the cereal material with a kneading and shearing effect on the one hand between the discs 21 and on the other hand between the discs and the internal wall of the sleeve 13.

Conventionally, these kneading discs 21 are formed by bi-lobe elements in the shape of a diamond and the vertices of which are truncated to achieve a controlled passage of the material and these bi-lobe elements of each screw are offset by 90 ° one compared to others. In addition, the two-lobe elements of the two screws overlap each other. Then, the cereal material thus sheared is transferred to the transfer zone D in which the screws 11 and 12 are provided with threads 22 with wide pitch.

During the transfer of the cereal material in zones C and D, this material is gradually brought to a temperature of the order of 140 ° C, that is to say between 120 ° C and 150 ° C by heating means 23.

In zone E, the screws 11 and 12 are provided with counter-threads 24, that is to say threads with reverse pitch, which have openings 25 extending radially from the axis of the screw to the periphery of the net and regularly distributed around the axis.

In this way, the flow rate of the cereal material which passes through zone E is controlled, which determines braking in this zone and, therefore, compression in the upstream part of the cooking-extrusion machine. This results in an intense kneading effect of the material. In this zone E, the material is gradually brought to a temperature of the order of 180 ° C, that is to say between 160 ° C and 190 ° C using heating means 26.

In the compression zone F, the screws 11 and 12 include threads 28 with a tight pitch so as to compress the cereal material and the sheath 13 in this zone F is equipped with heating means 29 to bring the temperature of this material to a temperature of the order of 120 ° C.

The heating means 18, 20, 23 and 26 are constituted for example by electrical resistances arranged around the sheath 13 or by circuits for circulation of a heat-transfer fluid, arranged in the sheath 13 to gradually heat the cereal material to the temperature ambient at the inlet of the cooking-extrusion machine 1 up to a temperature of the order of 180 ° C. at the outlet of said machine 1. The extrusion temperature can be between 160 ° C. and 250 ° C. .

In general, the heating means 18, 20, 23 and 26 optionally provide additional heating to the material in addition to its self-heating caused by the work carried out on the material by the screws. Thus, the cooking-extrusion machine 1 makes it possible to carry out, thanks to the composition of the sections of the screws 11 and 12 and to the heating means, various operations, such as for example transfer, kneading, plasticization, shearing, pressurization of the cereal material by the combination of elements adaptable according to the mechanical work to be subjected to said material.

By way of example, the speed of rotation of the screws 11 and 12 is greater than or equal to 600 rpm and advantageously between 600 and 1200 rpm.

According to a variant, the sheath 13 of the cooking-extrusion machine 1 is provided in zone A for supply and transfer with at least one orifice 27 for introducing water and or additives.

This water and these additives are introduced inside the sheath 13 for example by metering pumps 27a with piston or membrane.

The percentage of additives is between 0 and 30% by weight and preferably between 0 and 5% and are chosen among others from the following elements: plasticizers in particular glycerol, oils, surfactants, natural pigments, dyes, bactericides, repellents against animals, and also among two or more of these elements.

The area G for extruding and expanding the product consists of a die 30 comprising several outlet channels 31, the shape and dimensions of which are determined as a function of the final shape desired for the product.

At the outlet of the die 30 are arranged means 35 for cutting the product formed for example by a granulator knife allowing, thanks to a variable speed and a suitable number of cutting blades, to give the products the desired dimensions.

The pressure on the material during the extrusion of the product is between 10 and 300 bars and preferably between 50 and 150 bars and the volume expansion rate of the product is between 1 and 30 and preferably between 10 and 20. . . ^'

During the extrusion of the product, the vapor contained in this product causes a flash which makes it possible to obtain an expanded product. During the continuous production of the product, the specific mechanical energy which is supplied to this product by the extruder, has a value between 100 and 300 kWh / T and preferably between 150 and 200 kWh / T.

After cutting, the product conveyed for example by a pneumatic conveyor and a suitable device makes it possible to recover the vapor from the flash during extrusion, so that the product can be stored and rebalanced in moisture.

The additional injection of water into the extrusion cooking machine 1 makes it possible to adjust the humidity of the product inside this machine so that by varying this humidity and the speed of rotation. screws 11 and 12 and the grain size of the cereal material, a product with a desired texture and density is obtained for a given flow rate.

Thus, the higher the speed of the screws 11 and 12 and the lower the humidity, the lower the density of the product. This is directly related to the rate of expansion of the product which is a function of the shape of the die chosen.

By way of example, several cereal materials having different characteristics, as mentioned in the table below, were used in an installation according to the invention.

With regard to starch, it can be derived from cereal plant materials or from non-cereal plant materials.

An important element of a flour, starch is made up of a mixture of two glucose polymers - Tamylose and Amylopectin. The ratio between these two molecules is different according to their plant origin, in particular according to cereals and varieties as shown in the table below for wheat and corn native to two types of corn variety.

^the o It should be noted that the ratio amylose / amylopectin can be modified by genetic transformations from natural strains.

Tests have shown that the density of the product obtained decreases first when the speed of the screws increases and secondly when the grain size of the cereal material decreases. The curves shown in FIG. 4 clearly show the influence on the final apparent density of the biodegradable product not only of the speed of the screws, but also the physicochemical properties of the cereal material.

In order to produce a light expanded cushioning or insulation product, therefore, a flour with an average particle size of less than 500 μm is preferably used.

This flour is preferably treated at screw speeds greater than 900 rpm.

The expanded biodegradable product of the invention therefore consists of: - a starchy material based on a vegetable material,

- water and

- possibly one or more additive (s) without expanding properties. The weight content of starchy material in the biodegradable expanded dunnage of the invention can vary from about 70% to about 95%. Advantageously, it is between approximately 85% and approximately 94%, and more particularly between approximately 88% and approximately 93%. The expanded setting product obtained by the process according to the invention has a density greater than or equal to 2 g / l and preferably between 9 and 15 g / l and a humidity level between 0 and 30% and preferably between 6 and 12%.

Finally, this expanded wedging product has a resilience greater than 50% and preferably of the order of 85%.

By way of example, the expanded wedging product of cylindrical shape obtained by the process according to the invention has the following characteristics:

- humidity: 8.53% - resilience 50%: 85%

- density: 13.3 g / l with a specific mechanical energy of the extruder of 177 kWh / T and the expanded S-shaped product has the following characteristics: - humidity: 8.98%

- resilience 50%: 86.3%

- density: 12g / l with a specific mechanical energy of the extruder of 159 kWh / T. Below we will describe in detail two embodiments of a setting product. Example 1:

The cereal material used is a corn flour sold by the company Maïs Center Technologie under the title "Safrane 15.05". The average diameter (or. D50) of this flour is of the order of

190μm. The humidity of this flour is measured at around 14%. The extrusion machine as described above is supplied with flour at the rate of 450 kg / h and with water at the rate of 9 l / h.

In other words, in the sheath, the mixture has a water content of about 16% by weight and a dry matter content of around 84%. The screw rotation speed is 1050 rpm.

The temperature in zone A of the barrel is around 25 ° C, zone B at around 50 ° C, zone C at around 120 ° C, zone D at around 140 ° C and zones E and F at 185 ° C about,

The specific mechanical energy (EMS) supplied to the mixture is of the order of 177 kWh / t, and the pressure at the time of extrusion is of the order of 52 bars.

The industry used is made up of 4 cylindrical inserts 3mm in diameter.

Finally, the speed of the knives formed from two movable blades is of the order of 3500 rpm.

The biodegradable expanded setting product according to the invention consisting of a set of expanded biodegradable particles has an apparent density of the order of 13.3 g / l, and a water content after stabilization of the product, of the order of 8%, and therefore an amylated matter content of approximately 92%.

The biodegradable expanded particle obtained has a cylindrical shape of 42mm in length and about 16mm in diameter.

By compressing a biodegradable expanded particle between two pistons, it is possible to measure the force necessary to reach 50% of the thickness (denoted F ₅₀ % in Newton (N)) of this particle, as well as its capacity to find or not its initial thickness. In this case, the compression was not maintained.

We therefore define that a particle has a resilience of 100% if it fully regains its initial thickness after compression of 50% of its initial thickness and after relaxation of the compression force.

The particle in this example presents a _. F _50% , of the order of 28.5N and a resilience of the order of 85%. Example 2

The cereal material used is the same as that of the previous example.

A plant according to the invention is supplied with flour at the rate of 450 kg / h and with water at the rate of 25 l / h. A green pigment is added. In other words, in the sheath there is a starting formula of approximately 81% of dry matter, approximately 18% of water and less than 1% of green pigment.

The screw rotation speed is 900 rpm.

The temperature in zone A of the barrel is around 25 ° C, zone B at around 50 ° C, zone C at around 120 ° C, zone D at around 135 ° C and zones E and F at 180 ° C approx.

The specific mechanical energy (EMS) supplied to the mixture is of the order of 160 kWh / t and the pressure at the time of extrusion is of the order of 150 bars. The die used has four inserts in the shape of a "large S" with a surface area of 7mm ² (Fig. 5).

Finally, the speed of monobloc knives with four blades is around 4000 rpm.

The expanded product obtained has an apparent density of the order of 15 g / l, and a water content after stabilization of the product, of the order of 8.5%, and therefore a starch content of l '' of 91.5%.

The expanded biodegradable particle obtained has an "S" shape of 20mm in length and about 13mm in width.

The particle of this example has an F ₅₀ % of the order of 22N and a resilience of the order of 89%.

Other pigments or dyes could be used so that the product obtained at the outlet of the extruder has different colors.

Furthermore, the product can be single-color or multi-color depending on the type of object to be packaged. By way of comparison, the table below summarizes a few characteristics of different wedging products made of expanded and biodegradable polystyrene of the invention according to Example 1.

The manufacturing process according to the invention makes it possible to subject a raw material of plant origin to an intense thermomechanical treatment in a cooking-extrusion machine with two co-rotating screws, thus leading to macromolecular degradation of the starch contained in this cereal material and giving the product obtained a very expanded structure.

The expanded wedging product according to the invention therefore has the advantage of being biodegradable and of using as material a material derived from renewable and inexpensive energy.

In addition, no expanding agent being used during manufacture, the wedging product thus obtained protects the environment.

Claims

1. Expanded product in biodegradable material intended for use other than for food use, characterized in that it is obtained by cooking- extrusion of a native ground vegetable material whose average particle size is between 1 μm and 1.5 mm and whose amylose to amylopectin ratio is less than or equal to 30%.

2. Product according to claim 1, characterized in that the ground vegetable material consists of flour and / or cereal semolina.

3. Product according to claim 1 or 2, characterized in that the average particle size of the ground vegetable material is preferably between 1 and 500 μm.

4. Product according to any one of claims 1 to 3, characterized in that it has a density less than or equal to 100g / l, preferably less than 30g / l and advantageously between 9 and 15 g / l.

5. Product according to any one of claims 1 to 4, characterized in that it has a resilience greater than 50%, in particular at least 85%.

6. Product according to any one of claims 1 to 5, characterized in that it has a content of starchy material of between approximately 70 and 100% by weight, in particular between approximately 85 and 94% by weight and more particularly between approximately 88 and 93% by weight.

7. Product according to any one of claims 1 to 6, characterized in that the cooking-extrusion is carried out in an extrusion machine provided with at least one screw driven in rotation at a speed greater than or equal to 600 rev / min.

8. Product according to any one of claims 1 to 7, characterized in that the ground vegetable material comes from one or more of the following cereals: wheat, corn, rice, millet, millet, buckwheat , rye, spelled or barley.

9. Product according to any one of claims 1 to 7, characterized in that the ground vegetable material comes from the potato, lupine, cassava, soybeans, peas, quinoa or a mixture of one or more plants.

10. Product according to any one of claims 1 to 9, characterized in that it comprises at least one additive, the percentage by weight

5 is between 0 and 30% and preferably between 0 and 5%.

11. Product according to claim 10, characterized in that the additive (s) are chosen from: glycerol or other plasticizers, oils, surfactants, natural pigments, dyes, bactericides, repellents against animals.

12. Process for the continuous production of an expanded product made of biodegradable material intended for use other than for food use, characterized in that:

- Introduced into a baking-extrusion machine comprising at least one screw driven in rotation, a native ground vegetable material whose average particle size is between 1 μm and 1.5 mm and whose ratio 5 amylose to amylopectin is less than or equal to 30%, and

13. Method according to claim 11, characterized in that the said thermomechanical working step comprises:

- at least one phase of feeding and transfer of the crushed plant material,

at least one intermediate kneading phase with shearing of the plant material, mixing and cooking of this plant material 5 at a temperature less than or equal to 220 ° C.,

- a compression phase, and

- a product extrusion and expansion phase.

14. Method according to claim 13, characterized in that during the feeding and transfer phase, heating of the o plant material is carried out at a temperature of the order of 50 ° C.

15. The method of claim 13, characterized in that during the compression phase, heating of the plant material is carried out at a temperature of about 120 ° C.

16. Method according to claim 13, characterized in that the expanded product is cut at the outlet of the cooking-extrusion machine (1).

17. The method of claim 13, characterized in that during the feeding and transfer phase, water or additives chosen from the following elements are introduced: plasticizers, in particular glycerol, oils, surfactants, natural pigments, dyes, bacteria, repellents against animals or additives chosen from combinations of two or more of these elements.

18. The method of claim 17, characterized in that the percentage of additives is between 0 and 30% by weight and preferably between 0 and .5% by weight.

19. The method of claim 12, characterized in that the ground vegetable material comes from one or more of the following cereals: wheat, corn, rice, millet, millet, buckwheat, rye, oats, spelled or barley.

20. Method according to claim 19, characterized in that the cereal or cereals have the following weight composition:

- 0 to 20% water

- 0 to 85% of carbohydrate compounds,

- 0 to 30% protein,

- 0 to 10% fatty acids, - 0 to 5% minerals,

- 0 to 20% fiber.

21. The method of claim 12, characterized in that the vegetable material is derived from one or more of the following materials: potato, lupine, cassava, soybeans, peas, quinoa.

22. Installation for the continuous production of an expanded product made of biodegradable material intended for use other than for food use, characterized in that it comprises a machine (1) for. baking-extruding a native ground vegetable material with an average particle size of between 1 μm and 1.5 mm and with an amylose to amylopectin ratio of less than or equal to 30%, said cooking-extrusion machine comprising at least one screw driven in rotation in a sheath (13 ) of elongated shape at a speed greater than or equal to 600 rpm and determining at least one thermomechanical working zone of the plant material to obtain said product.

23. Installation according to claim 22, characterized in that the cooking-extrusion machine (1) is formed by two co-rotating and co-penetrating screws (11, 12), driven in rotation about axes parallel to the inside the scabbard.

24. Installation according to claim 22 or 23, characterized in that said thermomechanical working zone comprises:

- at least one zone A for feeding and at least one zone B for transferring the plant material, - at least one zone C, D, E intermediate kneading with shearing of the plant material, mixing and cooking of this material vegetable at a temperature less than or equal to 220 ° C.,

- a compression zone F, and

- a zone G for extruding and expanding the product.

25. Installation according to claim 24, characterized in that said supply and transfer zones A, B are provided with means (18) for heating said plant material to a temperature of the order of 50 ° C.

26. Installation according to claim 24, characterized in that the compression zone F is provided with means (27) for heating said plant material to a temperature of the order of 120 ° C.

27. Installation according to any one of claims 22 to 26, characterized in that it comprises, at the outlet of the machine (1) for cooking -extrusion, means (35) for cutting the product.

28. Installation according to any one of claims 22 to 26, characterized in that the sheath (13) of the. cooking-extrusion machine (1) is provided in zone A for supply and transfer of at least one orifice (27) for introducing water and / or additives chosen from the following elements Vants: plasticizers, in particular glycerol, oils, surfactants, natural pigments, dyes, bactericides, repellents against animals or additives chosen from combinations of two or more of these elements.

29. Installation according to any one of claims 22 to

28, characterized in that the pressure on the material during extrusion is between 10 and 300 bars and preferably between 50 and 150 bars.

30. Installation according to any one of claims 22 to

29, characterized in that the volume expansion rate of the product is between 1 and 30 and preferably between 10 and 20.