Stable biodegradable container

Abstract

The present invention relates to a container (1) having at least one opening (7) and a bottom (3), a containment (2) of a fibrous material having a biodegradable coating, and a cover (10) for the opening (7). The present invention further relates to a method for manufacturing the container (1). The underlying problem of the present invention is to provide a container (1) which is made exclusively from biodegradable components, has high gas impermeability and high mechanical stability, and whose manufacture is particularly flexible and cost-effective. To solve that problem, the container (2) comprises a biodegradable hardened impregnation that at least locally strengthens the structure of the container (2).

Description

[Technical field]

[0001] The present invention relates to a receptacle having a fibrous container with at least one opening and a bottom, and a cover for the opening, the receptacle having a biodegradable coating. The present invention further relates to a method for manufacturing the container. [Background technology]

[0002] WO2020 / 216719A1 discloses a method for the production of coated substrates, in which a flowable, biodegradable first coating that increases gas impermeability is applied to a cellulose-containing substrate, which solidifies to form a coating. To achieve packaging made primarily from natural raw materials with good gas and water impermeability, a second waterproof coating of animal and / or vegetable waxes and / or lipids is applied to the first coating.

[0003] WO2006 / 059112A2 discloses a method for producing a biodegradable composite material from plant material. The plant material may be in the form of pulp, which can be used to manufacture a housing. Such a composite housing can be coated with a biodegradable wax by immersing the housing in hot wax. WO2006 / 059112A2 also discloses that the coated substrate can be hot pressed.

[0004] GB2567418 discloses a coffee capsule made of a biodegradable and compostable fibrous material, which is provided with an internal and / or external biodegradable plastic coating. The coating can be thicker, especially in the area of ​​the flange / ring at the top of the capsule, and can cause mechanical strengthening in that area.

[0005] Biodegradable portion packs (e.g. coffee capsules) are also known from EP 2 218 653 A1, which packs are for example made from a gas-impermeable material. The portion packs may be fully or partly surface treated and / or coated. They may also have local reinforcements consisting of fibre layers. A sealing membrane is provided for sealing the portion pack, which sealing membrane is joined to the portion pack in an air-tight manner, in particular by heat sealing.

[0006] The containers known in the state of the art are not made exclusively from biodegradable components and their mechanical stability is relatively low.

[0007] The underlying problem of the present invention is to provide a container which is made exclusively from biodegradable components, has high gas impermeability and high mechanical stability, and whose manufacture is particularly flexible and cost-effective.

[0008] This problem is solved according to the invention by a container and a method having the features of the independent claims. Summary of the Invention

[0009] The container includes a fibrous material housing having at least one opening and a bottom, and a cover for the opening, the housing having a biodegradable coating.

[0010] The fiber container is made from an aqueous pulp with cellulose fibers. The cellulose fibers are shaped by a simple screening process using a suction mold. Water is sucked out through the holes of the suction mold, and the cellulose fibers are deposited on the surface of the suction mold with holes. The molded product formed by the suction mold is transferred to a transfer mold so that it is molded from both sides in a transfer process. Further heat treatment and pressure processes can be used to improve the surface quality of the molded product. The molded product of the fibrous material thus formed is sturdy and dimensionally stable.

[0011] The resulting fiber material container has an opening, a bottom opposite the opening, and a peripheral wall surrounding the opening and the bottom. The opening and the bottom may be, for example, circular, elliptical or polygonal. The cover is attached or can be attached to the opening of the container, with which the opening of the container is closed or can be closed. The cover interacts with the container such that the interior of the container is closed or can be closed from the environment. The cover is also biodegradable.

[0012] A fibrous material without a coating has a certain gas and water permeability. The fibrous containment described herein has a biodegradable coating that increases its gas and water impermeability, especially when the cover interacts with the containment. The coating can also increase the strength of the containment. Coatings of fibrous materials are generally known from the prior art. The coating can be, for example, sprayed. Alternatively or additionally, the coating can be applied by immersing the fibrous material in a coating bath and then drying it. For example, the applicant's International Publication WO2020 / 216719A1 discloses a biodegradable barrier coating for cellulose substrates, which coating is well suited for coating the fibrous containment described herein.

[0013] To solve the above problems, the container comprises a biodegradable hardened impregnation which at least locally strengthens the structure of the container.

[0014] In other words, a biodegradable agent is proposed that interacts with the fibrous material of the enclosure so as to structurally strengthen the enclosure at least locally, giving it greater strength upon hardening. In addition, the impregnation may be resistant to moisture.

[0015] In general, the term impregnation refers to soaking a porous material with an agent. The selected agent therefore increases the strength of the porous material by penetrating the pores and hardening. The selected impregnation can be a waterproofing agent, also known as a hydrophobic agent. When such an agent is wetted by a water droplet, the so-called wetting angle between the surface of the hydrophobic agent and the water droplet becomes large. In particular, moisture cannot penetrate the impregnation.

[0016] Textile products made from fibrous materials, such as the fibrous containments described herein, contain pores at regular intervals through which moisture, water or other liquids can penetrate. Such porous fibrous containments, usually made from cellulose-containing fibrous materials, usually have limited strength, especially when soaked. To increase resistance, the pores can be sealed with a hardening impregnating material, at least in selected areas. For example, the impregnating material can penetrate and fill the pores of the fibrous containment. The impregnating material, as mentioned above, preferably does not absorb any moisture itself, so that the impregnated fibrous material is not only stronger, but also absorbs little or no moisture in the filled pores.

[0017] In the containment described herein, complete impregnation of the fiber material is not absolutely necessary. It is sufficient that at least the pores in a locally limited area are filled with the impregnating agent and / or at least the pores near the surface of the fiber material are sealed by the impregnating agent. To seal the pores, they do not have to be completely filled with the impregnating agent. It is sufficient that the pores are at least partially filled and / or partially sealed.

[0018] The impregnants described herein can have at least two cohesive states. They are liquid during application and when they are cured, they are in their intended state. In particular, they can be thermoplastic for this purpose. This means that they are fluid when heated and solidify when cooled. Such a change is reversible in the thermoplastic cohesive state. Alternatively, they can simply be fluid during impregnation and irreversibly harden in their intended state as impregnated in the form of their duromers or elastomers.

[0019] The impregnation, once cured, has a higher strength than the textile material forming the enclosure. The strength of the impregnation may even be higher than the strength of the seal coating of the textile material. The enclosure can therefore withstand higher mechanical stresses after impregnation than an enclosure having a coating without the impregnation. The impregnation is biodegradable, so that the entire container is made only from biodegradable materials. Biodegradable means that the material can decompose under certain anaerobic or aerobic conditions.

[0020] In practice, the impregnated material may be compostable. Compostable means that the impregnated material is formed from organic material that is decomposed by soil organisms under the influence of atmospheric oxygen, i.e. under aerobic conditions. Preferably, not only is the impregnated material compostable, but all components of the container are compostable. In fact, the container and especially the impregnated material may be compostable without industrially defined conditions. This also means that composting is possible without industrial composting plants. Even if a container containing sorted compost waste is not disposed of and is released into the environment, the container can decompose within a few months. In contrast, the majority of compostable mechanically reinforced containers are usually only compostable under industrially defined conditions or over a long period of time, usually as long as several years. The ecological footprint of the container described herein is therefore significantly smaller than that of containers made from many other materials with similar mechanical stability.

[0021] In fact, the impregnation can be applied in the region of the opening and / or in the region of the bottom, these regions being often exposed to particularly high mechanical stresses and therefore mechanical reinforcement of the container material in these regions is particularly useful.

[0022] In fact, the impregnation can be applied to the surface facing the interior of the enclosure (inside). Additionally or alternatively, the impregnation can be applied to the surface facing the exterior of the enclosure (outside) or can be completely impregnated into the enclosure wall. As mentioned above, it may be sufficient to apply the impregnation only locally.

[0023] The impregnation can form a primer for the coating of the housing. If the impregnation is applied to only one side of the housing (i.e. either the inside or the outside), the coating may alternatively or additionally be applied to the side of the housing to which the impregnation is not applied. If the housing is provided with a localized impregnation, the coating can be applied partly on the impregnation and partly directly on the fibrous material.

[0024] In fact, the coating is made up of the following components: - cellulose fibres, - Casein, - whey, - Agar, - Psyllium Husk It may contain at least one of the following.

[0025] As previously mentioned, the coating increases the gas impermeability of the enclosure and may also increase its strength.

[0026] The cellulose nanofibrils or microfibrils can be dissolved, for example, in water and sprayed onto the housing. Nanocellulose has cellulose microfibrils with a median diameter in the range of 30-100 nm and / or cellulose nanofibrils with a median diameter in the range of 5-20 nm. Industrially sold cellulose fibrils are often a mixture of microfibrils and nanofibrils. In fact, a mixture of 2% by weight of nanocellulose in 98% by weight of water has proven effective for primers. If a higher percentage of cellulose is selected, deformation of the housing due to moisture can be reduced or avoided and the drying time of the primer can be shortened. In fact, it is preferred that the cellulose content of the primer solution is 2-10% by weight.

[0027] There are other organic materials that can be used for coating to increase the impermeability of the container to gas transmission. For example, casein powder can be mixed with water and modified using calcium hydroxide. The casein increases the impermeability and mechanical strength of the container. Casein modified with calcium hydroxide also becomes water repellent to a certain extent. It is also possible to modify casein with sodium bicarbonate, but the casein does not become water repellent.

[0028] In practice, 30 g of casein powder was allowed to swell in 100 ml of water for about 8-10 hours, 30 g of calcium hydroxide was added and stirred. After adding another 50 ml of water, the solution was sieved and used for coating. This coating can be applied after coating with cellulose fibers or as an alternative to coating with cellulose fibers. The coating may also contain both cellulose fibers and casein.

[0029] Whey is also suitable as a coating component. Whey can be denatured by heat (90-100°C). Whey as a coating component also increases the strength of the coated container. Whey coating itself is not water repellent, but can be made waterproof with a second coating.

[0030] Finally, gel-forming ingredients, such as agar (gelatin from algae) or psyllium husk (seed husks of Plantago indica and Plantago afra), are suitable for addition to the coating. Agar powder, for example, is mixed with water for this purpose and denatured at 100°C for 1 minute. It solidifies and gels when it cools. The gel can be applied to the containment and forms a thin layer that seals the not yet sealed pores of the fibrous material, increases its strength and repels water.

[0031] A similar effect can be achieved if ground psyllium husk is soaked in water and allowed to swell for about 20 minutes before being applied to the container.

[0032] As mentioned above, the components of the coating can be dissolved simultaneously in water and applied as a mixture. However, it is also possible that the coating can be applied to the container in several layers containing different components. All possible components of the primer mentioned above are biodegradable.

[0033] In fact, the impregnation can be composed of carnauba wax. Carnauba wax is a very hard tropical wax with a high melting temperature (about 85-89°C). Carnauba wax has almost no odor or taste by itself and is waterproof. Carnauba wax is very brittle when it dries and solidifies within a few seconds. Due to its hardness, it is also very resistant to friction. Carnauba wax is approved for food packaging and has long been used as a coating to increase the shelf life of mangoes, sweets, etc. In addition, the impregnation can contain beeswax or other natural waxes. A combination of a biodegradable wax and preferably also a compostable wax can be used for the impregnation, such a combination gives the molded textile product the desired strength and is particularly suitable for use with packaged foods. In addition to carnauba wax and beeswax, for example, shellac and sugarcane wax are also suitable for use in the agent for impregnating the molded textile body of the container.

[0034] Beeswax is a wax that is produced in Europe, among other places, and is less hard than carnauba wax. Beeswax helps reduce brittleness in mixtures with carnauba wax. Beeswax is also odorless and tasteless by itself and is approved for use in combination with food. The melting point of beeswax is about 65°C.

[0035] In fact, the container can further comprise a flange, which can be provided with an impregnation. The flange is formed integrally with the container of coated fiber material. In particular, the flange can project radially outwards at the upper end of the peripheral wall in the region of the opening. This increases the surface on which the cover can be attached. This design of the container is particularly well suited, for example as beverage powder portion packaging, in particular as a coffee capsule. By impregnating the flange, the flange and the region of the container adjacent to the flange are mechanically strengthened. Such strengthening is particularly advantageous for coffee capsules with a container made of fiber material, since the gripping mechanism of the coffee machine for the coffee capsule engages with the flange to move the coffee capsule from the first position to the second position. The impregnation of the flange gives the fiber coffee capsule the necessary strength and moisture resistance.

[0036] The coffee portion packaging in the form of a capsule made of the container described herein has a high degree of impermeability, much higher than conventional coffee pods made of uncoated cellulose fibers, and is more environmentally friendly than conventional coffee capsules made of aluminum. As a result, coffee can be stored for long periods of time without generating large amounts of waste. The coffee capsules described herein are made exclusively of natural raw materials and can easily biodegrade and / or decompose.

[0037] However, the containers described herein can also be used for other purposes. They can be used as transport containers for any foodstuff in solid or liquid form and for bulk products, in particular disposable transport containers. The containers can have the shape of a bottle. The impregnation can structurally reinforce the top with a male thread profile. Onto this male thread a screw cap can be screwed. Furthermore, the bottle bottom can be structurally reinforced by the impregnation. The container can also be a yogurt pot sealed with a sealing film. The container can also be used as packaging for non-food products, especially when these products should be protected against drying or against gas exchange with the environment.

[0038] In fact, the cover of the container may be designed as a sealing film. The sealing film may consist of a densely coated fiber material. The sealing film is thin, flexible and at the same time airtight. In particular, the coating of the sealing film may be identical to the coating of the container. It may 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 in the same solvent, the container and the cover can be joined together particularly easily and reliably by material adhesion. For example, the coated and not yet completely dried cover can be placed on the opening of the container so as to completely cover the opening. The container and the cover can then be pressed together, which causes the coating of the container to dissolve together with the coating of the cover and is later dried. By covering and joining in this way, the material consumption of the container is minimized, with only a few different materials, which is favorable for biodegradability and / or compostability.

[0039] The invention also relates to a method for producing a container comprising a textile receptacle having at least one opening and a bottom, a cover for the opening, a biodegradable coating and a biodegradable hardened impregnation that at least locally reinforces the receptacle, the method comprising the steps of: - sucking the fibrous material from the pulp using a suction mold and compressing the fibrous material into a recess; - Dehydrating and drying the storage compartment; - impregnating at least a portion of the storage section with an impregnating material; - curing the impregnation; - coating the housing with a coating; - The process of attaching the cover Includes.

[0040] The receptacles are conventionally produced by first forming a pulp with the fibrous material. The fibrous material can be sieved from the pulp and / or sucked out by using a suction mold and compressed, for example by pressing with a counter mold, to form a moulded part made of the fibrous material. In a subsequent step, the moulded part can be dewatered, for example by pressing again, and dried, for example by heating in an oven, before the resulting fibre receptacle is at least locally impregnated with a liquid impregnation. For example, only the bottom and / or only the areas with openings are impregnated. The impregnation can then be cured, so that it becomes solid and increases the strength and possibly moisture resistance of the impregnated areas of the fibre receptacle. Curing can take place, for example, in an oven at elevated temperature.

[0041] In a further step, the impregnated enclosure can be coated, thereby increasing the impermeability of the enclosure to the passage of gas or liquid. A seal coating is applied specifically to the inside of the enclosure to safely and securely contain the foodstuff therein.

[0042] After filling, a cover can be attached to the molded fiber container, so that the opening of the container is closed and a closed, airtight, at least locally reinforced and locally water repellent container is formed.

[0043] For further details of the respective method steps, reference is also made to the above description of the features thus obtained, and the advantages mentioned in connection with these features therefore apply to the present method.

[0044] As mentioned above, the container can be hot pressed at least after the impregnating agent has been applied, in order to allow the impregnating agent to penetrate the fibrous material better. This also allows a particularly high geometrical precision and a flat surface of the container to be achieved. Additionally or alternatively, hot pressing can be carried out after dewatering and drying of the fibrous material product. In this case, residual moisture can also be removed from the fibrous material. Finally, the container can be hot pressed after coating and before filling.

[0045] In practice, the impregnation can be applied by immersing the housing in a hot bath. Immersion in a hot bath is a particularly simple, fast and cost-effective way of applying the impregnation. In addition, the coating can be applied locally, in particular to the bottom area of ​​the housing and / or to the opening area (optionally with the flange, if a flange is provided). The applied impregnation can then be cured.

[0046] The impregnation can also be sprayed and then hot pressed if necessary. Finally, it is possible to introduce wax into the area of ​​the hot press mold where the impregnation is to be produced. In this case, the hot press mold is heated to a temperature above the melting temperature of the impregnation.

[0047] In practice, the coating can be applied to the container by spraying. Spraying the coating is a particularly simple, fast and cost-effective way of applying a coating to a textile product. Furthermore, spraying allows the formation of a particularly homogeneous and / or thin coating.

[0048] Further practical embodiments and advantages of the present invention will be described below with reference to the drawings. [Brief description of the drawings]

[0049] [Figure 1] 1 shows a container according to the invention in an embodiment as a coffee capsule in vertical section. [Diagram 2] 2 shows an oblique view from above of the container according to the invention of FIG. 1 without the cover. [Diagram 3] 2 shows an oblique view from below of the container according to the invention of FIG. 1. [Figure 4] 4 shows a manufacturing method for producing a container according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] In the figures 1 to 3 a container 1 is shown which is designed as a coffee capsule. The container 1 has a storage part 2 and is essentially rotationally symmetric. The container 1 has a bottom 3 and a peripheral wall 4 which surrounds the bottom 3. A central rotationally symmetric recess 5 is formed in the bottom 3, including a perforated area 6 which is also rotationally symmetric and which is arranged in the center of the recess. The perforated area is to be perforated by at least one needle so that the liquid supplied to the container 1 flows out under pressure. The recess 5 is oriented towards the interior of the storage part, i.e. towards an opening 7 on the side of the storage part 2 opposite the bottom 3. At the opening 7 the storage part 2 has a flange 8 and a peripheral wall 4 which surround the opening 7 in a rotationally symmetric manner. The flange 8 is oriented radially outwards from the peripheral wall 4 and essentially parallel to the bottom 3.

[0051] The housing 2, including the base 3, the peripheral wall 4 and the flange 8, is integrally formed from a fibrous material. A coating (not shown) is applied to the inside 9 of the housing 2, facing the interior of the housing, and to the upwardly facing surface of the flange 8. The coating can be made, for example, from cellulose and casein, and is therefore biodegradable. However, the coating can additionally or alternatively contain other biodegradable components, for example whey, agar and / or psyllium husk. The coating increases the gas impermeability and mechanical stability of the housing 2.

[0052] The opening 7 can be covered with a cover 10 designed as a sealing film, which in FIG. 1 is shown at a distance above the housing 2 for a better overview. The sealing film 10 is flexible and at the same time airtight. As intended, the sealing film 10 is fixed in place on the flange 8, thus sealing the housing interior from the environment. To be fixed on the flange, the sealing film 10 has on its surface oriented towards the flange 8 the same coating as on the inside 9 of the housing and on the upwardly facing surface of the flange 8 (not shown). The coatings of the sealing film 10 and the flange 8 adhere to each other.

[0053] The container 1 has impregnated areas 11a, 11b both in the region of the bottom 3 and in the region of the opening 7. In the cross-sectional view of 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 by dots. In both the regions 11a and 11b, the impregnation consists of a similar strength-enhancing material that solidifies on cooling. This material may be, for example, carnauba wax or a mixture of carnauba wax and beeswax. The impregnated areas 11a, 11b completely penetrate the fiber material forming the container 2. In this regard, all or almost all of the pores of the fiber material in the region of the bottom 3 and the opening 7 described herein are completely or almost completely filled with the impregnation, throughout the entire wall thickness of the container. The impregnation not only fills the pores of the fiber material, but also covers at least the outer fibers of the container with the impregnation. The impregnation therefore also forms a primer for the coating that is applied on top.

[0054] FIG. 4 shows a manufacturing method by which the container according to the invention can be manufactured using method steps AH.

[0055] According to this manufacturing method, in a first method step A, a pulp containing fibrous material is formed. The fibrous material is sucked from the pulp using a suction mould and then compressed by pressing with a transfer mould to form a container 2 made of fibrous material. In a further method step B, the container 2 is transferred from the transfer mould to a counter mould in which it is dewatered by a new, stronger pressing. The container 2 is then transferred to an oven chamber where it is dried at an increased temperature, for example 180° C. In a further method step C, the dried fibre container is hot pressed in order to increase the dimensional stability of the container and to remove any remaining moisture. In a further method step D, wax is locally applied to the container 2 to form impregnated areas 11a, 11b. The wax can be applied by first immersing the bottom 3 of the container 2 in a hot bath of wax to a predefined immersion depth. The container 2 is then turned over and the area of ​​the opening 7 is immersed in the same hot bath. Of course, a different hot bath can also be used for the second region of the impregnation, possibly with a different impregnation. Afterwards (method step E), the impregnated reservoir 2 can be hot-pressed again in order to further improve the dimensional stability of the reservoir and to allow a better introduction of the impregnation into the pores of the fibrous material.

[0056] As an alternative to applying the impregnation to a hot bath, the mold for hot pressing can also be filled with the agent to be applied. Then, method step D can be omitted.

[0057] After hot pressing, the container 2 is transferred to another oven in method step F. In this further oven the wax can be penetrated deeper into the pores of the fibre material. This treatment can be carried out at e.g. 90°C.

[0058] In a subsequent method step G, a coating is applied by spraying to the inside 9 of the fiber container 2 and to the upward side of the flange 8. In a final method step H, a sealing film 10 is coated with the same aqueous coating as the inside of the fiber container and the upper side of the flange and the sealing film 10 are adhered to the upward side of the flange 8 while the coating is still wet, so that a cover is formed which closes the opening of the container in an airtight manner.

[0059] As a result, the container 1 described herein has a biodegradable hardened impregnation that permeates the bottom 3 of the container 2 and the container wall in the area of ​​the opening 7. In addition, the container 1 has a biodegradable airtight coating that covers the entire inside 9 of the container 2 and the side of the cover 10 that faces the inside of the container. In the area of ​​the opening 7 of the container 2, the coating is applied to the impregnation that was applied first. Therefore, in this area, there is on the inside 9 of the container 2 a multi-layer system consisting of the impregnation located directly on the inside 9 and the coating formed thereon.

[0060] The features of the invention disclosed in the specification, the figures and the claims may be essential either individually or in any combination to realize the invention in its various embodiments. The invention is not limited to the described embodiments. The invention may vary within the scope of the claims, taking into account the knowledge of a person skilled in the art. [Explanation of symbols]

[0061] 1 container, coffee capsules 2 Storage area 3 bottom 4 Peripheral wall 5. Depression 6 Drilling area 7 Storage compartment opening 8 Flanges 9. Inside 10 Cover, sealing foil 11a Impregnated area 11b Impregnated area A method step (using a suction mold to suck the fiber material from the pulp and compress the fiber material into a container) B Method Step (Dehydrate and dry the container) C. Method Step (Hot Pressing of the Storage Section) D Method step (immersing part of the container in a hot bath of the impregnation agent) E. Method step (hot pressing of the impregnated container) F. Method step (hardening of the impregnated material) G. Method step (coating the container with a coating by spraying) H Method Steps (Install the Cover)

Claims

1. A container (1) having at least one opening (7) and a bottom (3), and a storage part (2) of fibrous material having a biodegradable coating, and a cover (10) for the opening (7), wherein the storage part (2) has a biodegradable hardened impregnation, and the impregnation structurally reinforces the storage part (2) at least locally.

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

3. The coating comprises the following components: - cellulose fibers, - casein, - whey, - agar, - psyllium husk The container (1) according to any one of claims 1 or 2, characterized in that it contains at least one of them.

4. The impregnation comprises the following components: - carnauba wax, - beeswax, - shellac, - sugar cane wax The container (1) according to claim 1 or 2, characterized in that it contains at least one of them.

5. The container (1) according to claim 1 or 2, characterized in that the storage part (2) has a flange (8), and the flange is provided with the impregnation.

6. The container (1) according to claim 1 or 2, characterized in that the cover (10) is designed as a sealing film.

7. A method for manufacturing a container (1) having at least one opening (7) and a bottom (3), a storage part (2) of fibrous material, a cover (10) for the opening (7), a biodegradable coating, and a biodegradable impregnation that structurally reinforces the storage part at least locally and is hardened, comprising: - a step (A) of sucking fibrous material from pulp using a suction mold and compressing the fibrous material to form a molded body; - a step (B) of dehydrating and drying the molded article, as a result, forming the storage part (2); - a step (D) of impregnating at least a part of the storage part (2) with the impregnation; - a step (F) of hardening the impregnation; - a step (G) of coating the storage part (2) with the coating; - a step (H) of attaching the cover (10) The method comprising.

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

9. The method according to any one of claims 7 or 8, characterized in that (D) the impregnated material is applied by immersing the storage part (2) in a high-temperature bath.

10. The method according to claim 7 or 8, characterized in that (G) the coating is applied to the storage part (2) by spraying.

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