Method for coating powder briquettes, in particular for preparing capsules containing beverage powder

Abstract

The invention relates to a method for coating powder briquettes, in particular for producing capsules containing beverage powder, the invention relates to a method for producing a coating liquid, comprising the following steps: i) providing a powder compact comprising a powder of at least one polysaccharide, ii) providing a container having a container wall made of a perforated material enclosing a cavity wherein the container has an inlet opening for introducing the coating liquid into the cavity, iii) introducing the powder compact into the cavity of the container, the powder compact being smaller than the volume of the cavity, (iv) introducing a coating liquid comprising a coating material into the cavity via the inlet opening, v) immersing the container filled with the powder compact and the coating material in a hardener liquid comprising a hardener compound wherein the viscosity of the hardener liquid is lower than the viscosity of the coating liquid, and vi) removing the container from the hardener liquid and removing the coated powder compact from the container.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 202180026800.9, entitled “Method for Coating Powder Compactor, In particular for Preparing Capsules Containing Beverage Powder”, with a priority date of April 20, 2020, a filing date of April 20, 2021, and an application number of 202180026800.9.

[0002] The present invention relates to a method for coating powder briquettes, particularly for manufacturing capsules containing beverage powders suitable for preparing beverages such as cocoa, tea or coffee.

[0003] In recent years, in addition to coffee packets, coffee capsules, typically made of stainless steel, aluminum, or plastic, have been increasingly used for serving beverages, especially brewed coffee. These capsules allow coffee powder to be stored for longer periods without losing aroma. Furthermore, by inserting a capsule with the desired coffee type into a suitable coffee machine, where hot water is forced through the capsule to create brewed coffee, these capsules allow for quick and user-friendly preparation of coffee portions with the desired flavor. However, these capsules are relatively expensive, partly due to the materials used and the intensive manufacturing process. Moreover, these capsules present environmental problems. Firstly, they are not recyclable and are typically disposed of as residual waste by consumers after use. Therefore, coffee capsule recycling is practically nonexistent, which is particularly concerning in the case of aluminum-based coffee capsules, as aluminum production is very energy-intensive, resulting in a particularly poor CO2 balance. Another major drawback is that these capsules are not biodegradable and therefore cannot be biologically processed. This is a serious problem, considering that well over 2 billion coffee capsules are consumed annually in Germany alone.

[0004] Capsules made from alternative materials have been proposed to at least partially circumvent the aforementioned problems.

[0005] For example, from WO 2010 / 006979 A1, a capsule filled with coffee or tea and comprising a capsule wall, which, in addition to the capsule contents, also contains water as a structural component. However, in order to form a stable capsule wall, the capsule needs to be cooled below the freezing point of the structural component, because the structural component melts and wets the capsule contents above its freezing point. This naturally greatly limits the use of such capsules.

[0006] WO 2009 / 053811 A2 describes a capsule that may contain ground coffee, cappuccino powder, chocolate powder, milk powder, or tea powder. The capsule comprises two halves forming the capsule wall. Here, the capsule wall is made of a material soluble in water and dissolves during brewing. In this concept, the capsule wall material dissolves during brewing and thus becomes part of the prepared beverage, which can have an undesirable impact on the taste. Furthermore, the manufacture of such a capsule is complex and expensive.

[0007] To overcome the aforementioned drawbacks, EP 3 115 316 A1 has also proposed a capsule particularly suitable for manufacturing coffee, comprising a briquette containing at least one polysaccharide, such as coffee powder, coated with at least one coating comprising a cross-linked polysaccharide. Preferably, the coating is composed of alginate and is obtained by immersing the briquette in an alkali metal alginate solution, followed by immersing the thus-treated briquette in an alkaline earth metal salt solution. In this process, alkaline earth metal ions act as cross-linking agents because they form coordination or ionic bonds with the groups of the alginate. This provides a water-insoluble coating that does not affect the taste of the beverage made from the capsule and provides sufficient capsule stability to ensure protection during transport and handling without significant loss of flavor of the capsule contents. Due to the relatively high viscosity of the alkali metal alginate solution, the coating material adheres poorly to the hydrophobic coffee powder briquette. This makes it difficult to transfer the powder briquette from the alkali metal alginate solution and immerse it in the alkaline earth metal salt solution. Even when done carefully and with the aid of specially designed jigs, achieving a sufficiently uniform coating thickness on powder briquettes is difficult, if possible.

[0008] Based on this, the objective of this invention is to provide a method for coating powder briquettes, particularly for manufacturing capsules containing beverage powders, which are used to prepare beverages from beverage powders such as cocoa, tea and coffee, and to obtain coated powder briquettes with uniform coating thickness simply and reliably using this method.

[0009] According to the present invention, this task is solved by a method for coating powder briquettes, particularly for manufacturing capsules containing beverage powder, the method comprising the following steps:

[0010] i) Providing a powder compact containing at least one polysaccharide powder,

[0011] ii) A container with a closed cavity and a wall made of a perforated material, wherein the container has an inlet opening for introducing a coating liquid into the cavity.

[0012] iii) Place the powder briquettes into the cavity of the container, wherein the powder briquettes are smaller than the volume of the cavity.

[0013] (iv) Introduce a coating liquid containing the coating material into the chamber through the inlet opening.

[0014] v) Immersing a container filled with powder briquettes and coating material into a curing agent liquid containing a curing agent compound, wherein the viscosity of the curing agent liquid is lower than the viscosity of the coating liquid, and

[0015] vi) Remove the container from the hardener liquid and remove the coated powder briquettes from the container.

[0016] This solution is based on the knowledge that by using a container with a closed cavity wall made of perforated material, and an inlet opening for introducing a coating liquid, powder blocks can be easily and reliably coated while obtaining a coating of uniform thickness. Since the volume of the powder block introduced into the cavity of the container in step iii) is smaller than the cavity's volume, the powder block adapts to the cavity, forming a space between the powder block and the inner side of the perforated material container wall defining the cavity. In step iv), this space can be filled with the coating liquid by introducing it. Due to the perforations and the inlet opening, the air initially present in the intermediate space is displaced by the coating liquid, allowing the entire intermediate space to be completely filled with the coating liquid in step iv). Because the powder block floats on the introduced coating liquid, it is surrounded by a uniformly thick layer of coating liquid when the gap space is completely filled. A uniform coating thickness is easily and reliably obtained by immersing the container filled with the powder block and coating material into a hardener liquid. Because the viscosity of the hardener liquid is lower than that of the coating liquid, during step v), the hardener liquid can rapidly and uniformly enter the container through the perforated material, i.e., through its pores, and thus contact the coating liquid, while the coating liquid, due to its higher viscosity, will not leave the container through the perforated material. Therefore, this method readily and reliably yields coated powder briquettes with a uniform coating thickness.

[0017] For the purposes of this invention, a perforated material refers to a material having a plurality of small holes that are regularly arranged in the material and each hole has at least substantially the same shape and size.

[0018] The present invention does not impose any particular limitation on the polysaccharide-containing material in the powder compact provided in step i). In particular, good results have been obtained when the powder compact comprises, or preferably comprises, a material selected from, coffee powder, tea powder, drinking chocolate powder, cocoa powder, and milk powder. Especially good results have been obtained when the powder compact is composed of ground coffee powder.

[0019] For the purposes of this invention, powder briquettes are understood to be compressed powder. Good results are obtained particularly when the powder briquettes prepared in step i) are manufactured by pressing powder, especially coffee powder, at a pressure of 1 to 100 MPa, particularly preferably 5 to 50 MPa, and very particularly preferably 15 to 30 MPa. This provides sufficient compaction to ensure that the powder briquettes can be firmly coated and achieve good oxygen barrier properties. At lower pressures, cohesion is insufficient, while at higher pressures, over-compaction occurs, and in some cases, this can lead to damage to the capsules after removal from the press and subsequent relaxation.

[0020] In principle, the powder briquettes can have any shape. Preferably, the powder briquettes are spherical. In particular, good results are obtained when the diameter of the spherical powder briquettes is 1 to 10 cm, preferably 1 to 5 cm, particularly preferably 2 to 4 cm, and most preferably 2.7 to 3.7 cm.

[0021] In line with this, it is preferred that the cavity of the container is also spherical, that is, the inner surface of the container is spherical.

[0022] In a further development of the invention, it is suggested that the diameter of the cavity in the container be 0.5 to 10.0 mm larger than the diameter of the spherical powder compact used, preferably 1.0 to 8.0 mm larger, and particularly preferably 3.0 to 6.0 mm larger.

[0023] According to a particularly preferred embodiment of the invention, the perforated material constituting the container wall is a wire mesh. For the purposes of this invention, the wire mesh is understood as a flat structure with regularly arranged, hole-like structures, formed by the intersection of warp and weft threads at right angles. On the one hand, wire mesh is relatively inexpensive and easy to process or shape; on the other hand, the holes contained therein are arranged in a particularly regular manner and have the same shape and size.

[0024] Preferably, the porous material, preferably a wire mesh, has pores of such size or mesh size that when the container is immersed in the hardener fluid, the more viscous coating fluid does not pass through the perforated material, preferably the wire mesh, and exit the container cavity, thus leaving the container, but the less viscous hardener fluid passes through the perforated material, preferably the wire mesh, and enters the container quickly and uniformly on the container surface.

[0025] In particular, good results were obtained when the diameter of the pores in the porous material of the container wall or the mesh size of the wire mesh was 0.01 to 0.30 mm, preferably 0.02 to 0.21 mm, more preferably 0.04 to 0.08 mm, even more preferably 0.05 to 0.075 mm, most preferably 0.058 to 0.068 mm, such as about 0.063 mm.

[0026] As described above, it is preferable to use wire mesh as the porous material for the container wall. Preferably, the wire mesh is made of steel or stainless steel. In a further development of the inventive concept, it is suggested that the wire mesh has a wire thickness of 0.01 to 0.30 mm, preferably 0.02 to 0.20 mm, particularly preferably 0.03 to 0.10 mm, most preferably 0.04 to 0.06 mm, and most preferably 0.045 to 0.055 mm.

[0027] According to the invention, the container provided in step ii) includes an inlet opening for introducing the coating liquid into the cavity. In order to enable the coating liquid to be well introduced into the cavity of the container through the inlet opening, according to a further preferred embodiment, it is recommended to provide a tube above the inlet opening of the container, the tube being fixedly connected to the container, and preferably arranged such that its longitudinal axis is radially located on the container wall.

[0028] In principle, the pipe can be made of any material, such as the same material as the container, preferably steel or stainless steel. However, the pipe is preferably unperforated.

[0029] In principle, the present invention does not limit the shape of the tube. For example, the tube can have a rectangular, square, circular, elliptical, oval, or polygonal cross-section. Preferably, the tube is a rectangular or circular tube with a length of 1.0 to 5.0 cm, more preferably 2.0 to 4.0 cm. In particular, good results are obtained using a circular tube with an inner diameter of 0.1 to 5.0 mm, preferably 0.5 to 2.5 mm, more preferably 0.75 to 1.25 mm, most preferably 0.9 to 1.1 mm, and most preferably 0.95 to 1.05 mm.

[0030] To facilitate the easy introduction and removal of the coated powder into the container cavity, a further development of the invention proposes that the container be constructed of two halves connected to each other by connecting elements such as hinges, thus allowing for easy assembly to form a closed container. In the case of a preferred spherical construction of the container, the container preferably has two hemispheres connected to each other via hinges. The two hemispheres preferably each have the same dimensions and are each formed of the same perforated material. If each of the two hemispheres is placed on top of the other, and their equators precisely align, they define a spherical cavity except for an inlet opening, which is preferably formed only in one of the two hemispheres. Good results are particularly obtained if the inlet opening is located at the extreme point of one of the two hemispheres.

[0031] As can be seen from the cross-section, the radius of curvature of the lower part of the two semi-dots, near the mid-latitude region, may also be slightly different from that of the upper part.

[0032] To make it easier to place the two semi-domes accurately and completely on top of each other, each semi-dome can have an outward-facing collar at the mid-latitude, which encircles each semi-dome in a circular shape.

[0033] In principle, the present invention does not limit the shape of the inlet opening. For example, the inlet opening may have a rectangular, square, circular, elliptical, oval, or polygonal cross-section. Preferably, the inlet opening has a circular cross-section, wherein the diameter of the inlet opening is preferably 0.1 to 5.0 mm, more preferably 0.5 to 2.5 mm, more preferably 0.75 to 1.25 mm, even more preferably 0.9 to 1.1 mm, and most preferably 0.95 to 1.05 mm.

[0034] To facilitate the easy and rapid simultaneous or parallel coating of several powder briquettes, the process can also be carried out using multiple containers, whereby the containers designed as described above are connected to one or more other containers of the same size in a support. In this way, multiple containers can be simultaneously immersed in the hardener liquid bath in a single step. In this embodiment, the support preferably comprises 2 to 100, particularly 5 to 50 containers.

[0035] In principle, there are no particular limitations on the chemical properties of the coating material contained in the coating liquid and the hardener compound contained in the hardener liquid, provided that the hardener liquid has a lower viscosity than the coating liquid. Examples of suitable coating materials include those selected from starch, cellulose, chitin, carrageenan, agar, and alginate.

[0036] Preferably, the viscosity of the hardener liquid is 0.01 to 100 mPa. . s, more preferably 0.1 to 20 mPa . s, with an optimal value of 0.5 to 10.0 mPa . s, such as 1 mPa . The viscosity of the coating liquid is preferably greater than 100 to 10000 mPa. . s, preferably 200 to 5000 mPa . s, optimal value 300 to 1000 mPa . s, such as 500 mPa . s.

[0037] Choose a hardening compound to preferably crosslink the coating material via i) covalent bonds or ii) ionic bonds and / or coordination bonds.

[0038] According to a very particularly preferred embodiment of the invention, alginate is used as a coating material in the method. This has the advantage of easily and rapidly forming a uniform coating through crosslinking with alkaline earth metal ions, i.e., without compromising the flavor of the water-insoluble coating of beverages such as coffee made from the coated powder briquettes. Additionally, this provides sufficient stability to the coated powder briquettes to ensure protection during transport and handling without any perceptible loss of flavor to their contents. Furthermore, calcium alginate has excellent biodegradability. Another advantage is that calcium alginate is an approved food additive, E number E405, meaning it is harmless to health.

[0039] Therefore, it is particularly preferred to use a coating liquid containing alkali metal alginate (especially sodium alginate) as a coating material, and a curing agent liquid containing alkaline earth metal salt (especially calcium salt, such as calcium chloride) as a curing compound.

[0040] For example, if an alkali metal alginate solution is used as a coating liquid, preferably an aqueous alkali metal alginate solution of 0.5 to 5 wt%, and particularly preferably an aqueous sodium alginate solution of 0.5 to 5 wt%, is used as the coating liquid, and an alkaline earth metal salt solution, preferably an aqueous alkaline earth metal salt solution of 1 to 7 wt%, and particularly preferably an aqueous calcium chloride solution of 1 to 7 wt%, is used as the hardener liquid, good results are obtained.

[0041] According to another very particularly preferred embodiment of the present invention, the method includes the following steps:

[0042] i) Providing a powder compact containing at least one polysaccharide powder,

[0043] ii) A container with a wall made of wire mesh having a closed cavity, wherein the container has an inlet opening for introducing a coating liquid into the cavity, and the wire mesh has a mesh size of 0.01 to 0.30 mm, preferably 0.02 to 0.021 mm, more preferably 0.04 to 0.08 mm, even more preferably 0.05 to 0.075 mm, and most preferably 0.058 to 0.068 mm.

[0044] iii) Place the powder briquettes into the cavity of the container, wherein the powder briquettes are smaller than the volume of the cavity.

[0045] (iv) A coating liquid containing alkali metal alginate is introduced into the cavity through the inlet opening.

[0046] v) Immersing a container filled with powdered briquettes and coating material into a hardening agent liquid containing an alkaline earth metal salt, wherein the viscosity of the hardening agent liquid is lower than that of the coating liquid, and

[0047] vi) Remove the container from the hardener liquid and remove the coated powder briquettes from the container.

[0048] In any of the above embodiments, steps i) to vi) can be performed in the order described above. Similarly, step ii) can be performed before or simultaneously with step i).

[0049] In addition to the steps described above, the method may also include, as step vii), drying the coated powder briquettes obtained in step vi).

[0050] According to a further preferred embodiment, the coating thickness of the dried coated powder briquettes is 10 to 600 μm, particularly preferably 20 to 40 μm.

[0051] The invention will now be explained with reference to the illustrative and non-limiting accompanying drawings.

[0052] It shows:

[0053] Figure 1 A container suitable for the method of the present invention, in the open state according to an embodiment of the invention, has a container wall made of a perforated material.

[0054] Figure 2 In a closed state Figure 1 The container shown.

[0055] Applicable to the method according to the invention Figure 1 The container 10 shown includes two semi-domes 12, 12' connected to each other by hinges 14. Each of the two semi-domes 12, 12' has the same dimensions and is formed of the same perforated material, preferably stainless steel wire mesh. The mid-latitude lines 16, 16' of each of the two semi-domes 12, 12' each have radially outwardly projecting collars 18, 18', which in each case annularly surround the semi-dome 12, 12'. An inlet opening 20 is located at the extreme point of the upper semi-dome 12', and a tube 22 fixedly connected to the container is provided above the inlet opening 20. The two semi-domes 12, 12' form the container wall 24.

[0056] exist Figure 1 In the open state shown, according to method step iii), the powder compact can be easily introduced into the cavity 26 of the container 10, and according to method step v), the coated powder compact can be easily removed from the cavity 26 of the container 10. Figure 2 As shown, by folding the two semi-domes 12, 12' together via hinge 14, the two semi-domes 12, 12' can be assembled and closed in a manner that precisely matches their mid-latitude lines. In this state, according to method step iv), the coating liquid can be introduced into the cavity 26 of the container via pipe 22 and inlet opening 20, and according to method step v), the container 10 filled with powder briquettes and coating material can be immersed in the hardener liquid container.

[0057] Other aspects of the invention are described in the following numbered clauses:

[0058] Clause 1. A method for coating powder briquettes, particularly for manufacturing capsules containing beverage powder, comprising the following steps:

[0059] i) Providing a powder compact containing at least one polysaccharide powder,

[0060] ii) A container (10) having a closed cavity (26) and a container wall (24) made of a perforated material, wherein the container (10) has an inlet opening (20) for introducing a coating liquid into the cavity (26),

[0061] iii) Place the powder compact into the cavity (26) of the container (10), wherein the powder compact is smaller than the volume of the cavity (26).

[0062] iv) The coating liquid containing the coating material is introduced into the chamber (26) through the inlet opening (20).

[0063] v) Immerse the container (10) filled with powder compacts and coating material into a curing agent liquid containing a curing agent compound, wherein the viscosity of the curing agent liquid is lower than that of the coating liquid, and

[0064] vi) Remove the container (10) from the hardener liquid and remove the coated powder block from the container (10).

[0065] Clause 2. The method according to Clause 1, characterized in that the powder compact is spherical and is made by pressing a powder of a substance selected from coffee powder, tea powder, drinking chocolate powder, cocoa powder and milk powder under a pressure of 0.01 to 1000 MPa, preferably 0.05 to 500 MPa, more preferably 0.1 to 100 MPa, further preferably 0.5 to 100 MPa, even more preferably 1 to 100 MPa, even more preferably 5 to 50 MPa, and most preferably 15 to 30 MPa.

[0066] Clause 3. The method according to Clause 1 or 2 is characterized in that the container (10) has a spherical cavity (26).

[0067] Clause 4. The method according to any of the preceding clauses is characterized in that the perforated material of the container wall (24) is a metal wire mesh with a mesh size of 0.01 to 0.30 mm, preferably 0.02 to 0.21 mm, more preferably 0.04 to 0.08 mm, even more preferably 0.05 to 0.075 mm, and most preferably 0.058 to 0.068 mm.

[0068] Clause 5. The method according to Clause 4, characterized in that the wire mesh is made of stainless steel and the wire thickness is 0.01 to 0.30 mm, preferably 0.02 to 0.20 mm, more preferably 0.03 to 0.10 mm, most preferably 0.04 to 0.06 mm, and most preferably 0.045 to 0.055 mm.

[0069] Clause 6. The method according to any of the preceding clauses is characterized in that the tube (22) securely connected to the container (10) is arranged above the inlet opening (20) of the container (10).

[0070] Clause 7. The method according to Clause 6, characterized in that the tube (22) is a rectangular tube (22) or a circular tube (22) with a length of 1.0 to 5.0 cm, preferably 2.0 to 4.0 cm.

[0071] Clause 8. The method according to Clause 6 or 7, characterized in that the tube (22) is a circular tube (22) having an inner diameter of 0.1 to 5.0 mm, preferably 0.5 to 2.5 mm, more preferably 0.75 to 1.25 mm, even more preferably 0.9 to 1.1 mm, and most preferably 0.95 to 1.05 mm.

[0072] Clause 9. The method according to any of the preceding clauses is characterized in that the container (10) comprises two hemispheres (12, 12'), each hemisphere (12, 12') having the same size and each hemisphere (12, 12') being formed of a perforated material, which are connected by a hinge (14) and when the two hemispheres (12, 12') are stacked on top of each other in such a way that their mid-latitudes (16, 16') are precisely matched, the hemispheres (12, 12') enclose a spherical cavity (26), and one of the hemispheres (12, 12') has an inlet opening (20) at its pole.

[0073] Clause 10. The method according to any of the preceding clauses is characterized in that the inlet opening (20) has a circular cross-section with a diameter of 0.1 to 5.0 mm, preferably 0.5 to 2.5 mm, more preferably 0.75 to 1.25 mm, even more preferably 0.9 to 1.1 mm, and most preferably 0.95 to 1.05 mm.

[0074] Clause 11. The method according to any of the preceding clauses is characterized in that the container (10) is connected in a support to one or more other containers (10) of the same size, such that multiple powder compacts can be coated simultaneously.

[0075] Clause 12. The method according to any of the preceding clauses is characterized by using a coating liquid comprising a coating material selected from starch, cellulose, chitin, carrageenan, agar, and alginate.

[0076] Clause 13. The method according to any one of the preceding clauses is characterized in that a curing liquid comprising a curing compound is used, said curing compound being crosslinked with the coating material via i) covalent bonds or ii) ionic bonds and / or coordination bonds.

[0077] Clause 14. The method according to any one of the preceding clauses is characterized in that a coating liquid containing an alkali metal alginate as a coating material is used, and a hardening liquid containing an alkaline earth metal salt as a hardening compound is used.

[0078] Clause 15. The method according to Clause 14, characterized in that an alkali metal alginate solution, preferably an aqueous 0.5 to 5 wt% alkali metal alginate solution, particularly preferably an aqueous 0.5 to 5 wt% sodium alginate solution, is used as the coating liquid, and an alkaline earth metal salt solution, preferably an aqueous 1 to 7 wt% alkaline earth metal salt solution, particularly preferably an aqueous 1 to 7 wt% calcium chloride solution, is used as the hardener liquid.

Claims

1. A method for coating powder briquettes, particularly for manufacturing capsules containing beverage powder, comprising the following steps: i) Providing a powder compact containing at least one polysaccharide powder, ii) A container (10) having a closed cavity (26) and a container wall (24) made of a perforated material, wherein the container (10) has an inlet opening (20) for introducing a coating liquid into the cavity (26), iii) The powder block is placed into the cavity (26) of the container (10), wherein the powder block is smaller than the volume of the cavity (26), and an intermediate space is formed between the cavity of the container and the powder block. iv) A coating liquid containing the coating material is introduced into the cavity (26) via the inlet opening (20), wherein the intermediate space is filled with the coating liquid. v) Immersing a container (10) filled with powder compacts and coating material into a curing agent liquid containing a curing agent compound, wherein the curing agent liquid enters the container through the perforated material of the container wall, wherein the viscosity of the curing agent liquid is lower than that of the coating liquid, and vi) Remove the container (10) from the hardener liquid and remove the coated powder block from the container (10).

2. The method according to claim 1, characterized in that, The powder compact is spherical and is made by pressing a powder selected from coffee powder, tea powder, drinking chocolate powder, cocoa powder and milk powder under a pressure of 0.01 to 1000 MPa, preferably 0.05 to 500 MPa, more preferably 0.1 to 100 MPa, further preferably 0.5 to 100 MPa, even more preferably 1 to 100 MPa, even more preferably 5 to 50 MPa, and most preferably 15 to 30 MPa.

3. The method according to claim 1 or 2, characterized in that, The container (10) has a spherical cavity (26).

4. The method according to any one of the preceding claims, characterized in that, The perforated material of the container wall (24) is a metal wire mesh with a mesh size of 0.01 to 0.30 mm, preferably 0.02 to 0.21 mm, more preferably 0.04 to 0.08 mm, even more preferably 0.05 to 0.075 mm, and most preferably 0.058 to 0.068 mm.

5. The method according to claim 4, characterized in that, The wire mesh is made of stainless steel, and the thickness of its wires is 0.01 to 0.30 mm, preferably 0.02 to 0.20 mm, more preferably 0.03 to 0.10 mm, most preferably 0.04 to 0.06 mm, and most preferably 0.045 to 0.055 mm.

6. The method according to any one of the preceding claims, characterized in that, A tube (22) securely connected to the container (10) is arranged above the inlet opening (20) of the container (10).

7. The method according to claim 6, characterized in that, The tube (22) is a rectangular tube (22) or a circular tube (22), and its length is 1.0 to 5.0 cm, preferably 2.0 to 4.0 cm.

8. The method according to claim 6 or 7, characterized in that, The tube (22) is a circular tube (22) with an inner diameter of 0.1 to 5.0 mm, preferably 0.5 to 2.5 mm, more preferably 0.75 to 1.25 mm, even more preferably 0.9 to 1.1 mm, and most preferably 0.95 to 1.05 mm.

9. The method according to any one of the preceding claims, characterized in that, The container (10) comprises two hemispheres (12, 12'), each hemisphere (12, 12') having the same size and each hemisphere (12, 12') being formed of perforated material. They are connected by a hinge (14). When the two hemispheres (12, 12') are stacked on top of each other in such a way that their mid-latitudes (16, 16') fit precisely together, the hemispheres (12, 12') enclose a spherical cavity (26). One of the hemispheres (12, 12') has an inlet opening (20) at its pole.

10. The method according to any one of the preceding claims, characterized in that, The inlet opening (20) has a circular cross-section with a diameter of 0.1 to 5.0 mm, preferably 0.5 to 2.5 mm, more preferably 0.75 to 1.25 mm, even more preferably 0.9 to 1.1 mm, and most preferably 0.95 to 1.05 mm.

11. The method according to any one of the preceding claims, characterized in that, The container (10) is connected in a support to one or more other containers (10) of the same size, so that multiple powder blocks can be coated simultaneously.

12. The method according to any one of the preceding claims, characterized in that, Use a coating liquid containing coating materials selected from starch, cellulose, chitin, carrageenan, agar, and alginate.

13. The method according to any one of the preceding claims, characterized in that, A curing liquid containing a curing compound is used to coat the material via i) covalent bonds or ii) ionic bonds and / or coordination bonds.

14. The method according to any one of the preceding claims, characterized in that, A coating liquid containing alkali metal alginate as a coating material is used, and a hardening liquid containing alkaline earth metal salt as a hardening compound is used.

15. The method according to claim 14, characterized in that, An alkali metal alginate solution, preferably an aqueous 0.5 to 5 wt% alkali metal alginate solution, particularly preferably an aqueous 0.5 to 5 wt% sodium alginate solution, is used as a coating liquid, and an alkaline earth metal salt solution, preferably an aqueous 1 to 7 wt% alkaline earth metal salt solution, particularly preferably an aqueous 1 to 7 wt% calcium chloride solution, is used as a hardener liquid.

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