EP4351983A2

EP4351983A2 - Stable biodegradable container, and method for manufacturing same

Info

Publication number: EP4351983A2
Application number: EP22733358.0A
Authority: EP
Inventors: Tahsin Dag
Original assignee: Papacks Sales GmbH
Current assignee: Papacks Sales GmbH
Priority date: 2021-06-08
Filing date: 2022-06-08
Publication date: 2024-04-17
Also published as: DE102021114743A1; CN117460677A; WO2022258696A3; CA3222071A1; WO2022258696A2

Abstract

The invention relates to a container (1) having a vessel (2) which comprises at least one opening (7) and a bottom (3) and is made of fibrous material, and having a cover (10) for the opening (7), wherein the vessel (2) has a biodegradable coating. The invention also relates to a method for producing the container (1). The aim of the invention is to provide a container (1) which is formed exclusively by biodegradable components, has high gas-tightness and high mechanical stability, and the production of which is particularly flexible and economical. The aim is achieved in that the vessel (2) comprises a biodegradable, cured impregnation which has an at least locally structurally reinforcing effect on the vessel (2).

Description

Stable biodegradable container

description

The invention relates to a container with a container made of fibrous material, having at least one opening and a bottom, and a cover for the opening, the container having a biodegradable coating. The invention also relates to a method for manufacturing the container.

A method for producing coated substrates is known from WO 2020/216719 A1, in which a flowable, biodegradable first coating that increases gas tightness is applied to a cellulose-containing substrate and this is solidified to form a coating. In order to achieve packaging that is primarily made of natural raw materials and has good gas and water tightness, a second watertight coating made of animal and/or vegetable waxes and/or lipids is applied to the first coating.

WO 2006/0591 12 A2 discloses a method for producing a biodegradable composite material from plant material. The plant material may be in the form of a pulp and used to make a container. By immersing such a composite container in hot wax, the container can be coated with biodegradable wax. WO 2006/059112 A2 also discloses that the coated substrate can be hot pressed.

GB 2567418 a biodegradable and compostable coffee capsule made of fiber is known, which is provided on the inside and / or the outside with a biodegradable plastic layer. the Coating can be thicker, particularly in the area of a flange/ring at the top of the capsule where it can cause mechanical reinforcement.

A biodegradable portion pack (e.g. a coffee capsule) is also known from EP 2 218 653 A1, which is formed, for example, from a gas-impermeable material. The sachet can be fully or partially surface treated and/or coated. It can also have a local reinforcement made of a fiber layer. A closure membrane is provided for closing the portion pack, which membrane is connected to the portion pack in an airtight manner, in particular by means of diligent sealing.

The containers known from the prior art are either not made up exclusively of biodegradable components, or they have comparatively low mechanical stability.

The object of the invention is therefore to provide a container that is made exclusively from biodegradable components, that is highly gas-tight and highly mechanically stable, and whose opening position is particularly flexible and inexpensive.

The object is achieved by a container and a method having the features of the independent patent claims.

The container comprises a fibrous container having at least one opening and a bottom and a cover for the opening, the container having a biodegradable coating.

The pulp container is made from an aqueous pulp containing cellulosic fibers. The cellulose fibers are brought into a shape by a simple scooping process using a suction mold. The water is sucked off through pores in the suction mold and the cellulose fibers deposit on the porous surface of the suction mold. In the transfer process, the shaped body formed by the suction mold is transferred to a transfer mold so that it is shaped from both sides. Additional thermal processing methods and pressing methods can be used, which increase the surface quality of the shaped body. The shaped bodies made of fibrous material are solid and dimensionally stable.

The pulp container thus produced has an opening, a bottom opposite the opening, and a peripheral wall surrounding the opening and the bottom. For example, the opening and the bottom can be round, oval or polygonal. A cover is attached or attachable to the opening of the container, by means of which the opening of the container is closed or can be closed. The cover interacts with the container in such a way that the interior of the container is closed or can be closed with respect to the environment. The cover is also biodegradable.

Pulp without a coating has some gas and water permeability. The fibrous container described herein has a biodegradable coating which increases its gas and water tightness, particularly when the cover cooperates with the container. The strength of the container can also be increased by the coating. The coating of fibrous material is basically known from the prior art. Coatings can be sprayed on, for example. Alternatively or additionally, a coating can be carried out by immersing a fibrous material in a coating bath and then drying it. For example, the applicant's publication WO 2020/216719 A1 discloses a biodegradable barrier layer for a cellulose substrate which is well suited for coating the fibrous material containers described here. To solve the above problem, the container has a biodegradable, hardened impregnation that at least locally reinforces the structure of the container.

In other words, a biodegradable agent is proposed which interacts with the fibrous material of the container in such a way that it at least locally strengthens the container structurally and gives it greater strength when it has hardened. In addition, the impregnation can be resistant to moisture.

In general, the term impregnation refers to the impregnation of a porous material with an agent. The selected agent thus penetrates into the pores and increases the strength of the porous material through hardening. The impregnation chosen can be a moisture repellant, also referred to as a hydrophobic agent. When such agents are wetted with a drop of water, the so-called wetting angle between the surface of the hydrophobic agent and the drop of water is large. In particular, no moisture can penetrate the impregnation.

Fibrous bodies made of fibrous material, such as the fibrous material container described here, regularly contain pores into which moisture, water or other liquids can penetrate. Such porous fibrous material containers, which are usually made of cellulose-containing fibrous material, usually have limited strength, especially if they are soaked. In order to increase durability, the pores can be sealed with the hardening impregnation, at least in selected areas. For this purpose, the impregnation can penetrate, for example, into the pores of the fibrous material container and fill them out. Since the impregnation itself, as mentioned above, preferably does not absorb any moisture, the impregnated fibrous material not only becomes firmer but also absorbs little or no moisture with the filled pores. In the case of the container described here, complete soaking of the fibrous material is not absolutely necessary. It is sufficient if at least the pores of a locally limited area are filled by the impregnation and/or if at least the pores of the fiber material close to the surface are closed by the impregnation. In order to close the pores, the pores do not have to be completely filled with the impregnation. It is sufficient if these are at least partially filled and/or partially closed.

The impregnation described here can have at least two aggregate states. It is liquid during application and has hardened in the intended condition as an impregnation. In particular, it can be thermoplastic for this purpose. By this is meant that the impregnation is flowable in a heated state and solidifies when cooled. Such a change in the state of aggregation is reversible in ther moplastic materials. Alternatively, it is also possible that the impregnation is flowable only during the impregnation and hardens irreversibly in the intended state as an impregnation in the type of duromers or elastomers.

In the hardened state, the impregnation has a higher strength than the fibrous material from which the container is formed. The strength of the impregnation can also be higher than the strength of the sealing coating of the fibrous material. After impregnation, the container can thus absorb higher mechanical stresses than the container with a coating without impregnation. Since the impregnation is biolo cally degradable, the entire container consists exclusively of biodegradable materials. Biodegradable means that the materials can be decomposed under certain anaerobic or aerobic conditions.

In practice, the impregnation can be compostable. Compostable means that the impregnation is made of organic material, which is broken down by soil organisms under the influence of atmospheric oxygen, i.e. under aerobic conditions. Preferably, not only the impregnation is compostable, but all components of the container are compostable. In practice, the container and in particular the impregnation can be compostable without industrially defined conditions. This means that composting is also possible without an industrial composting plant. Even if the container is not disposed of with the sorted compost waste but is released into the environment, it can decompose within a few months. In contrast, the vast majority of compostable, mechanically reinforced containers can usually only be composted under industrially defined conditions or over long periods of several years. The ecological footprint of the container described here is therefore significantly reduced compared to containers made of many other materials with similar mechanical stability.

In practice, the impregnation can be applied in the area of the opening and/or in the area of the bottom. These areas are often exposed to particularly high mechanical stresses, so mechanical reinforcement of the container material in these areas is particularly useful.

In practice, the impregnation can be applied to a surface (the inside) of the container facing towards the interior of the container. Additionally or alternatively, the impregnation can be applied to the outwardly facing surface (the outside) of the container or completely saturate the container wall. As mentioned above, it may be sufficient to apply the impregnation only locally.

The impregnation can form a primer for the coating of the container age. If the impregnation is only applied to one side of the container (i.e. either on the inside or on the outside), the coating can alternatively or additionally be applied to that side of the container. ters be applied to which the impregnation is not applied.

If the container is locally provided with the impregnation, the coating can be partly applied on the impregnation and partly directly on the fibrous material.

In practice, the coating may contain at least one of the following components:

- cellulose fibers,

- casein,

- whey,

- Agar Agar,

- psyllium husks.

As mentioned above, the coating increases the gas-tightness of the container and can also increase its strength.

For example, cellulose nanofibrils or microfibrils can be dissolved in water and can be sprayed onto the container. Nanocellulose has cellulose microfibrils with a median diameter in a range of 30 to 100 nm and/or cellulose nanofibrils with a median diameter in a range of 5 to 20 nm. Industrially sold cellulose fibrils are often a mixture of microfibrils and nanofibrils. In practice, a mixture of 2% by weight of nanocellulose in 98% by weight of water has proven itself for the primer. Choosing a higher cellulose content can reduce or avoid deformation of the container due to moisture and the drying time of the primer can be shortened. In practice, a cellulose content of the priming solution of 2 to 10% by weight is suitable.

There are other organic materials which, in a coating, increase the tightness of a container against the passage of gas. For example, casein powder can be mixed with water and denatured with calcium hydroxide. The casein increases the tightness and the mechanical nical strength of the container. Casein denatured with calcium hydroxide also becomes water repellent to some extent. It is also possible to denature the casein with baking soda, but it does not make it water-repellent.

In practice, 30 g of casein powder was swollen with 100 ml of water for about 8 to 10 hours, 30 g of calcium hydroxide was added and stirred. After another addition of 50 ml of water, the solution was sieved and used for coating. This coating can be applied after coating with cellulosic fibers or as an alternative to coating with cellulosic fibers. The coating can also contain both cellulosic fibers and casein.

Whey is also suitable as a component of the coating. Whey can be denatured by heat (90°-100°C). Whey as a component of the coating also increases the strength of the coated container. The whey coating itself is not water-repellent, but can be made waterproof with a second coating.

Finally, gel-forming components such as agar agar (gelatine from algae) or psyllium husks (seed husks of the plantain species Plantago indica, Plantago afra) are suitable for addition to the coating. For this purpose, agar agar powder is mixed with water and denatured for 1 minute at 100°C. As it cools, it hardens and gels. The gel can be applied to the container and forms a thin layer that seals the unclosed pores of the fiber, increasing strength and repelling water.

A similar effect is achieved if ground psyllium husks are soaked in water and applied to the container after they have swelled for around 20 minutes. As mentioned, the components of the coating can be dissolved in water and applied as a mixture at the same time. However, it is also possible to apply the coating to the container as several layers with different components. All of the above possible components of the primer are biodegradable.

In practice, the impregnation can be formed from carnauba wax. Carnauba wax is a very hard, tropical wax with a high melting point (approx. 85-89°C). It has hardly any smell or taste of its own and is waterproof. It is very brittle when dry and hardens within seconds. Due to its hardness, it is also very stable against abrasion. It is approved for food packaging and has long been used as a coating to increase the shelf life of e.g. B. mangoes, sweets, etc. used. In addition, the impregnation can contain beeswax or other natural waxes. Combinations of biologically degradable and, if possible, also compostable waxes can be used for the impregnation, which impart the desired strength to the molded fiber and are particularly suitable for use with the packaged food. In addition to carnauba wax and beeswax, shellac and sugar cane wax, for example, are also suitable for use in the agent with which the molded fiber body of the container is impregnated.

Beeswax is a wax produced in Europe, among other places, that is less hard than carnauba wax. In a mixture with carnauba wax, beeswax helps reduce brittleness. It also has hardly any smell or taste of its own and is approved for use in connection with food. Its melting point is around 65°C.

In practice, the container can also have a flange and this flange can be provided with the impregnation. The flange is formed integrally with the container from coated fibrous material. In particular, the flange at the upper end of the peripheral wall in the region of the opening protrude radially outwards. As a result, a large area is available to which the cover can be attached. This design of the container is particularly well suited, for example, as a portion pack for powdered beverages, in particular as a coffee capsule. By impregnating the flange, the flange and the area of the container adjoining it are mechanically reinforced. Such ampli effect is particularly advantageous for coffee capsules with a container made of fibrous material, since a gripping mechanism of coffee machines for coffee capsules engages the flange to move the coffee capsule from a first position to a second position. The impregnation of the flange gives the fiber coffee capsules the necessary strength and resistance to moisture.

A coffee portion pack in the form of a capsule consisting of the container described here has a high degree of tightness, which is much higher than with conventional coffee pods made of uncoated cellulose fibers, and better environmental compatibility than conventional coffee capsules made of aluminum. As a result, you can keep the coffee for a long time without producing a lot of waste. The coffee capsule described here consists solely of natural raw materials and can be easily biodegraded and/or composted.

However, the container described here can also be provided for other purposes. It can be used as a transport container, in particular a one-way transport container, for any foodstuffs in solid or liquid form and as bulk goods. The container may be in the form of a bottle. The impregnation allows structural reinforcement of the upper portion which has the contour of an external thread. A screw cap can be screwed onto this external thread. Furthermore, the impregnation can structurally strengthen the bottom of the bottle. The container can be a yoghurt cup closed with sealing foil. The container can also be used as packaging for products other than food, especially when these Products are to be protected against drying out or against gas exchange with the environment.

In practice, the cover of the container can be in the form of a sealing foil. Sealing films can consist of densely coated fibrous material. They are thin, flexible and gas-tight at the same time. The coating of the sealing film can in particular be identical to the coating of the container. However, it can also have a different composition. If the coating of the cover is identical to the coating of the container and/or these two coatings can be dissolved by the same solvent, the container and the cover can be connected to one another particularly simply and securely by means of a material connection. For example, the coated and not yet completely dried cover can be placed against the opening of the container in such a way that the opening is completely covered. The container and cover can then be pressed together, whereby the coating of the container is dissolved and later dries in connection with the coating of the cover. With such a cover and connection, the container has a minimal use of materials and only a few different materials, which is advantageous for biodegradability and/or compostability.

The invention also relates to a method for producing a container with a container made of fibrous material and having at least one opening and a bottom; a cover for the opening; a biodegradable coating; and a biodegradable, hardened impregnation at least locally reinforcing the container. The procedure comprises the procedural steps:

- sucking fibrous material from a pulp through a suction mold and compacting the fibrous material to the container;

- dewatering and drying of the container; - Impregnating at least part of the container with the impregnation;

- hardening of the impregnation;

- coating the container with the coating;

- Attaching the cover.

Conventionally, the container is made by first forming a pulp with fibrous material. The fibrous material can be scooped out of the pulp and/or sucked in through a suction mold and compacted, for example by pressing with a counter-mold, into a shaped body made of fibrous material. In a subsequent step, the shaped body can be dewatered, for example by renewed pressing, and dried, for example, by heating in an oven, before the fibrous material container produced in this way is at least locally provided with a liquid impregnation. For example, only the bottom and/or only the area with the opening is impregnated. The impregnation can then harden so that it becomes solid and the strength and possibly the moisture resistance of the impregnated fibrous material container area is increased. Curing can take place, for example, in an oven at elevated temperature.

In a further step, the impregnated container can be coated, which increases its tightness against the passage of gases or liquids. The sealing coating is applied in particular to the inside of the container in order to securely and tightly accommodate the food contained therein.

After filling, the cover can be attached to the cast fiber container, so that the opening of the container is closed and a closed, gas-tight, at least locally reinforced and locally water-repellent container is formed. With regard to further details of the respective method steps, reference is also made to the above description of the features generated thereby. The advantages mentioned in connection with these features apply accordingly to the method.

As mentioned above, the container can be hot-pressed at least after the impregnation has been applied, whereby the impregnation penetrates the pulp better. As a result, a particularly high geometric precision of the container and flat surfaces can also be achieved. Additionally or alternatively, the hot pressing can take place after the dewatering and drying of the fibrous shaped body. In this case, residual moisture can also be removed from the fibrous material. Finally, after coating and before filling, the container can be hot pressed.

In practice, the impregnation can be applied by immersing the container in a warm bath. Dipping in a warm bath is a particularly easy, quick and cost-effective way to apply the impregnation. In addition, the coating can be applied locally and in particular in the area of the bottom and/or in the area of the opening of the container (possibly with the flange, if this is provided). The applied impregnation can then harden.

The impregnation can also be sprayed on and, if necessary, then hot-pressed. Finally, it is possible to place the wax in the areas of a hot stamping mold where the impregnation is to be made. In this case, the hot press mold must be heated to a temperature above the melting temperature of the impregnation.

In practice, the coating can be applied by spraying onto the container. Spraying on the coating described above is a particularly simple, quick and cost-effective option. speed to apply the coating to the fibrous body. Furthermore, spraying allows a particularly homogeneous and/or thin coating to be formed.

Further practical embodiments and advantages of the invention are described below in connection with the drawings. Show it:

1 shows the container according to the invention in an embodiment as a coffee capsule in a vertical sectional view;

FIG. 2 shows the container according to the invention from FIG. 1 without a cover in a view obliquely from above;

FIG. 3 shows the container according to the invention from FIG. 1 in a view obliquely from below; FIG.

4 shows a method of opening the container according to the invention.

Figures 1 to 3 show a container 1, which is designed as a coffee capsule. The container 1 has a container 2 and is essentially rotationally symmetrical. It has a base 3 and a peripheral wall 4 surrounding the base 3 . In the base 3 there is a central and rotationally symmetrical depression 5 with a perforation area 6 which is likewise arranged in a rotationally symmetrical and centrally manner. The perforation area is pierced by at least one needle to allow liquid fed into the container 1 under pressure to escape. The recess 5 is oriented in the direction of the interior of the container, ie in the direction of an opening 7 of the container 2 opposite the bottom 3 . Of the Flange 8 points radially outwards from the peripheral wall 4 and is oriented essentially parallel to the bottom 3 .

The container 2 with the bottom 3, the peripheral wall 4 and the flange 8 is formed in one piece from fibrous material. A coating (not shown) is applied to the inside 9 of the container 2 pointing into the interior of the container and to the surface of the flange 8 pointing upwards. The coating can be formed from cellulose and casein, for example, and is therefore biodegradable. In addition or as an alternative, it can also contain other biodegradable components, for example whey, agar agar and/or psyllium husks. The coating increases the gas tightness and the mechanical stability of the container 2.

The opening 7 can be covered with the cover 10 shown in FIG. 1 at a distance above the container 2 for a better overview and is designed as a sealing foil. The sealing film 10 is flexible and gas-tight at the same time. Intended for it is fixed resting on the flange 8 and thus closes the container interior from the environment. For fixing on the flange, the sealing film 10 has the same coating (not shown) on the surface oriented in the direction of the flange 8 as the container inside 9 and the upward-facing surface of the flange 8. The coatings of the sealing film 10 and the flange 8 are materially connected to each other.

In the area of the bottom 3 and the opening 7, the container 1 has an impregnated area 11a, 11b. In the sectional representation in FIG. 1, the impregnated areas 11a, 11b are highlighted by cross-hatching. In FIGS. 2 and 3, the surfaces of the impregnated areas 11a, 11b are highlighted with dots. In both areas 1 1 a and 1 1 b, the impregnation consists of the same strength-enhancing material that hardens on cooling. This material can be, for example, carnauba wax or a mixture of carnauba wax and beeswax. The impregnated areas 1 1 a, 11b completely penetrate the fibrous material from which the container 2 is formed. In this respect, all or almost all pores of the fibrous material in the areas of the bottom 3 and the opening 7 described here are completely or almost completely filled with the impregnation over the entire wall thickness of the container. The immersion not only fills the pores of the fibrous material, but at least also covers the fibers located on the outside of the container with the impregnation. Thus, the impregnation also forms a primer for a coating applied thereto.

FIG. 4 shows a possible method of opening the container according to the invention with method steps A to F1.

According to this manufacturing process, in a first process step A, a pulp with fibrous material is formed. The fiber material is sucked out of the pulp by a suction mold and then compacted by pressing with a transfer mold into the container 2 made of pulp. In a further process step B, the container 2 is passed from the transfer form into a counter-mold in which the container 2 is dewatered by renewed, stronger pressing. It is then transferred to an oven chamber and dried there at an elevated temperature of, for example, 180°C. In a further process step C, the dried fibrous material container is hot-pressed in order to increase the dimensional stability and to remove the last moisture. In a further method step D, wax is applied locally to the container 2 in order to form the impregnated areas 11a, 11b. The wax can be applied by first immersing the container 2 with the bottom 3 up to a predefined immersion depth in a hot bath made of the wax. The container 2 is then turned over and the area of the opening 7 is immersed in the same warm bath. Of course, a different warm bath, possibly also with a different impregnation, can also be used for the second area of the impregnation. Subsequently (method step E), the impregnated container 2 is hot-pressed again in order to maintain its shape to improve further and to be able to bring the impregnation better into the pores of the fiber.

As an alternative to applying the impregnation in a hot bath, the press mold for hot pressing can also be filled with the agent to be applied. Process step D can then be omitted.

After the hot pressing, the container 2 is transferred in method step F to another furnace. In this additional oven, the wax can penetrate deeper into the pores of the fiber material. This treatment can take place at 90°C, for example.

In a subsequent process step G, the coating is applied to the inside 9 of the pulp container 2 and the upward-facing side of the flange 8 by spraying on. In a final process step F1, the sealing film 10 is coated with the same aqueous coating as the inside of the fiber container and the top of the flange and the sealing film 10 is glued to the upward-facing side of the flange 8 with the coating still wet, so that a cover is formed, which closes the opening of the container gas-tight.

As a result, the container 1 described here has a biodegradable, hardened impregnation which penetrates the container wall in the region of the bottom 3 and the opening 7 of the container 2 . In addition, the container 1 has a flat, biodegradable and gas-tight coating over the entire inside 9 of the container 2 and the side of the cover 10 pointing in the direction of the interior of the container. In the area of the opening 7 of the container 2, the coating is applied to the first applied impregnation. In this area, on the inside 9 of the container 2, there is thus a multi-layer system consisting of the impregnation located directly on the inside 9 and the coating formed thereon. The features of the invention disclosed in the present description, in the drawings and in the claims can be essential both individually and in any combination for the realization of the invention in its various embodiments. The invention is not limited to the embodiments described. It can be varied within the scope of the claims and taking into account the knowledge of the person skilled in the art.

reference list

1 container, coffee capsule

2 containers

3 floor

4 perimeter wall

5 deepening

6 perforation area

7 Container opening

8 flange

9 inside

10 cover, sealing film

11a impregnated area

11b impregnated area

A Process step (suction of fibrous material from a pulp by a suction mold and compaction of the fibrous material to the container

B Process step (dewatering and drying of the container)

C Process step (hot pressing of the container)

D Process step (immersing part of the container in

warm bath from a means for impregnation)

E Process step (hot pressing of the impregnated container)

F Process step (hardening of the impregnation) G Process step (coating the container with the coating by spraying it on)

H Procedure (Attaching the cover)

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Claims

patent claims

1. Container (1) with at least one opening (7) and a bottom (3) having a container (2) made of fibrous material and a cover (10) for the opening (7), wherein the container (2) has a biodegradable Coating, characterized in that the container (2) has a biodegradable, cured impregnation which at least locally structurally reinforces the container (2).

2. Container (1) according to claim 1, characterized in that the impregnation is applied in the area of the opening (7) and/or in the area of the bottom (3).

3. Container (1) according to one of claims 1 or 2, characterized in that the coating contains at least one of the following components:

- cellulose fibers;

- casein;

- whey;

- Agar Agar;

- psyllium husks.

4. Container (1) according to any one of claims 1 to 3, characterized in that the impregnation contains at least one of the following components:

- carnauba wax;

- beeswax;

- shellac;

- Sugar cane wax.

5. Container (1) according to any one of claims 1 to 4, characterized in that the container (2) has a flange (8) and this flange is provided with the impregnation.

6. Container (1) according to any one of claims 1 to 5, characterized in that the cover (10) is designed as a sealing film.

7. Method for the production of a container (1) with a container (2) made of fibrous material having at least one opening (7) and a base (3); a cover (10) for the opening (7); a biodegradable coating; and a biodegradable, hardened impregnation that at least locally reinforces the structure of the container, the method comprising the following method steps:

- Suction of fibrous material from a pulp through a suction mold and compaction of the fibrous material into a shaped body, (A);

- Dewatering and drying of the shaped body, so that the container ter (2) is formed (B);

- impregnating at least part of the container (2) with the impregnation (D);

- curing of the impregnation, (F);

- coating the container (2) with the coating (G);

- Fit the cover (10), (Fl).

8. The method according to claim 7, characterized in that the container (2) is hot-pressed at least once (C, E).

9. The method according to any one of claims 7 or 8, characterized in that the impregnation is applied by immersing the container (2) in a warm bath, (D).

10. The method according to any one of claims 7 to 9, characterized in that the coating is applied by spraying onto the container (2), (G).

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