Compression mold for receiving a fiber-based blank

Abstract

The invention relates to a compression mold (20) for receiving a fiber-based blank for use in a microwave compartment. The compression mold (20) is microwave-permeable. The compression mold (20) has a multi-layer design and has at least a first, cavity-limiting, porous layer (21) and a second, steam-tight layer (22).

Description

[0001] Press mold for holding a fiber-based blank

[0002] The present invention relates to a press mold for receiving a fiber-based blank, in particular for receiving a container or a fiber-based closure element, according to the preamble of the independent claims.

[0003] A fiber-based blank in the form of a container was disclosed in WO 2012 / 139590 A1. To produce this container, so-called pulp is injected into an upside-down mold and pressed against a corresponding wall using a flexible balloon in this mold, thereby compressing it accordingly. The pulp is compressed and heated to a temperature of approximately 180°C to dry the container. It is also known to produce closure elements for containers from pulp.

[0004] Pulp is a mixture of fibers and water, especially natural fibers such as hemp fibers, cellulose fibers, or flax fibers, or a mixture thereof. The pulp may contain additives that, for example, improve the hardening of the compressed pulp, influence its final appearance, or generally alter the properties of the pulp or the final container.

[0005] The aforementioned process is time-consuming and energy-intensive. It has therefore already been proposed to improve it. WO 2018 / 020219 A1 discloses another process for drying wet, fiber-based blanks. Here, too, the blanks are containers. Here, the wet pulp is also pressed together inside the mold using a flexible balloon. The pre-processed container is then demolded together with the balloon inside and placed on a conveyor belt. The balloon is removed from the cold-formed container. The container is then exposed to microwaves to dry it. Before drying, the blank is very sensitive to the effects of force and must be handled very carefully.During the drying process, the container may become deformed, for example due to uneven drying or a non-uniform layer thickness, or it may be damaged by external influences.

[0006] It has also been proposed, for example in WO 2011 / 158000 A1, to leave the containers to be dried within a microwave-permeable mold while being exposed to microwaves. The microwave-permeable mold is also heated up immediately. This makes the process slow and requires a high level of energy.

[0007] It is therefore an object of the invention to remedy one or more disadvantages of the prior art. In particular, a mold is to be provided which makes it possible to make the process more efficient and / or to increase the drying performance.

[0008] This problem is solved by the device defined in the independent claim. Further embodiments emerge from the dependent patent claims.

[0009] A device according to the invention is provided by a mold for receiving a fiber-based blank. The fiber-based blank can be, in particular, a container or a fiber-based closure element for a container. The mold is intended for use in a microwave chamber. For this purpose, the mold is microwave-permeable.

[0010] The mold has a multi-layer structure and comprises at least a first, cavity-defining, porous layer and a second, vapor-tight layer. A desired strength of the mold can be achieved through a multi-layer structure. The different properties of the individual layers—the porous layer on the one hand and the vapor-tight layer on the other—can be used to adjust the distribution of water or water vapor within the mold.

[0011] Because the first layer defines the cavity, it provides the final shape of the blank, and the blank adheres to this layer during the drying process. The cavity is the negative mold of the final product.

[0012] In a porous mold, water or steam accumulates until saturation occurs. This results in at least a portion of the microwave energy being inadvertently introduced into the mold, heating it and reducing drying performance. However, if the mold is constructed with multiple layers and only the first layer is porous, the volume in which water and steam can accumulate is reduced. This means that less energy is required to dry a blank.

[0013] The vapor-tight layer prevents water or water vapor from penetrating deeper into the press mold.

[0014] In particular, it can be provided that the vapor-tight layer completely encloses the porous layer. This results in the blow molding tool being constructed as follows: A vapor-tight layer encloses a porous layer and the porous layer forms a cavity with a negative of the blank to be formed. Complete enclosing does not mean, however, that the porous layer is hermetically sealed from the environment, but rather that, for example, in the area of ​​a container opening, the porous layer is open to the outside so that, for example, water vapor can escape. It is not essential that the porous layer is directly adjacent to the vapor-tight layer or connected to it.

[0015] In particular, it can be provided that the mold has at least a third layer. The third layer is formed adjacent to the first layer and has discharge channels.

[0016] Such an arrangement enables water or water vapor to diffuse from the inside to the outside of the porous layer and be discharged through the discharge channels.

[0017] In particular, the third layer is arranged between the first layer and the second layer and spaced these two layers.

[0018] In particular, it can be provided that the third layer is also vapor-tight. This prevents water from entering the third layer and thus also prevents or at least reduces energy penetration.

[0019] In this case, vapor-tight means that the respective layer is made of a material or has a structural design which cannot absorb water and / or vapor.

[0020] Alternatively, the third layer can be porous. This allows the first layer to absorb moisture substantially evenly across its entire surface and also to release it substantially evenly, since the moisture can escape unhindered from the first layer.

[0021] Preferably, the discharge channels are arranged such that they open into a common suction channel. This makes it possible, for example, to force a targeted flow within the discharge channels or, if necessary, to provide a negative pressure so that water and / or water vapor can be discharged from the first porous layer independently or under force.

[0022] The mold may have an additional layer to provide the mold with an interface for connection to a corresponding machine. This layer may, for example, be a layer with a corresponding flange or stop surfaces that interact with and can be screwed to a corresponding counterpart, such as a mold support plate.

[0023] The mold can be constructed in several parts. It comprises, in particular, a first mold half and a second mold half, and preferably a mold base.

[0024] The multi-part design of the mold makes it easy to load the mold and remove the dried blank.

[0025] In particular, it can be provided that all discharge channels open into the press mold base and open into a common suction channel within the press mold base.

[0026] The mold can be made of polyetherimide, amorphous polyimide (PEI), or cycloolefin copolymer (COC), for example. These are microwave-permeable materials that are well suited for mold making.

[0027] In particular, the first layer and, if present, the third layer are made of polyimide (PEI).

[0028] In a preferred embodiment, the second layer and, if present, the further layer, are formed from cyclo-olefin copolymer (COC).

[0029] The combination of these two materials for the respective layers makes it possible to keep microwave absorption low while maintaining high dimensional stability. The thermal properties of both materials are comparable, so there are only minor differences in the behavior of the materials under different process conditions. This not only increases the service life of the mold but also its accuracy across different temperature ranges.

[0030] In particular, it can be provided that at least the first layer and the second layer are manufactured together using a 3D printing process and are thus formed as a single piece. This results in high stability, since these layers are firmly connected to one another by the 3D printing process.

[0031] To ensure that a first layer can be formed as a porous layer and a second layer as a vapor-tight layer, the corresponding parameters for the printing process can be adjusted. For example, a plastic filament is processed in the porous layer area in such a way that, for example, a fill setting (i.e., a print density) of only 80% is used, while in the vapor-tight layer area, a fill setting of 100% is used.

[0032] Alternatively, it can be provided that at least the first layer, the second layer, and the third layer are manufactured together using a 3D printing process and are thus formed in one piece. In particular, it can be provided that the press mold is manufactured entirely using a 3D printing process and is thus formed in one piece.

[0033] On the one hand, this allows for increased strength, since individual layers are no longer physically separated from one another. On the other hand, it allows for very specific design of the areas where the mold is porous and those where it is not. Furthermore, this type of manufacturing also makes it possible to produce the mold cost-effectively for more complex geometries and, in particular, to arrange drainage channels in preferred positions and, for example, even in a curved manner in space.

[0034] It goes without saying that the one-piece nature of such a production refers to the individual parts of the press mould, for example to a single press mould half or to the press mould base.

[0035] If a common material is chosen for the first and third layers, such as PEI, and a common material for the second and subsequent layers, such as COC, as explained above, it is also advisable to manufacture these elements using a single 3D printing process, particularly a single 3D printing process. This means that the first and third layers are manufactured as a single piece.

[0036] At the same time, with such a subdivision of the mold, it is advisable to mill the second and, if necessary, subsequent layers from an extrusion-compressed sheet. This way, the second and subsequent layers are manufactured as a single piece.

[0037] When manufactured using 3D printing, components are typically manufactured with an oversize so that the final dimension can be milled. This also makes it possible, for example, to achieve the desired surface finish.

[0038] The structure of a press mold is explained using schematic figures. It shows:

[0039] Figure 1 : A press form with partially hidden elements;

[0040] Figure 2 : a perspective sectional view of a mold half;

[0041] Figure 3: a perspective view of a press mold base; Figure 4: a perspective view of a sectional view from Figure 3.

[0042] Figure 1 shows a mold 20 with partially hidden elements. The mold 20 comprises a first mold half 20A and a second mold half 20B, as well as a mold base 20C. The mold half 20B is hidden in this case, so that the interior of the mold 20, i.e., the cavity, is visible.

[0043] Figure 2 shows a specific sectional view of a mold half 20A. As can be seen, the mold half 20A, and thus also the mold 20, is constructed in multiple layers. The innermost first layer 21 defines a cavity and is porous. A second layer 22 completely surrounds the first layer 21. Between the first layer 21 and the second layer 22, a third layer

[0044] 23. The third layer 23 provides drainage channels 231. The third layer 23 borders the first layer 21 and the second layer 22. In other words, the drainage channels 231 are formed between the first layer 21 and the second layer 22. These three layers 21 to 23 are encased by a further layer 24. The layer 24 provides an interface to a corresponding receptacle of a machine and additionally serves to reinforce and support the other layers. All layers are microwave-permeable and consist of the same material. The layers are manufactured in one piece using a 3D printing process. The first layer 21 is porous, and the second layer 22 and the third layer 23 are vapor-tight. The further layer 24 is also vapor-tight in the present case, but this is not absolutely necessary, since the second layer 22 prevents the penetration of water and / or water vapor into the further layer.

[0045] 24 is prevented.

[0046] Figure 3 shows a perspective view of a press mold base 20C. As can be seen, all discharge channels 231 from the press mold halves 20A and 20B open into corresponding discharge channels 231 within the press mold base 20C.

[0047] Figure 4 shows a perspective view of a sectional view from Figure 3. As can be seen, the discharge channels 231 nestle along the inner contour of the press mold base 20C and all open into a common suction channel 30, which can be subjected to negative pressure, for example, during the drying process, so that moisture can be discharged from the first layer 21 via the discharge channels 231 and accordingly the suction channel 30.

Claims

Patent claims 1. A compression mold (20) for receiving a fiber-based blank, in particular a container (100, 100', 100'') or a fiber-based closure element (300) for a container (100), for use in a microwave chamber, wherein the compression mold (20) is microwave-permeable, characterized in that the compression mold (20) has a multi-layer structure and has at least a first, cavity-defining, porous layer (21) and a second, vapor-tight layer (22).

2. Press mold (20) according to claim 1, characterized in that the vapor-tight layer (22) completely encloses the porous layer (21).

3. Press mold (20) according to claim 1 or 2, characterized in that the press mold (20) has at least a third layer (23), wherein the third layer (23) is formed adjacent to the first layer (21) and has discharge channels (231).

4. Press mold (20) according to claim 3, characterized in that the third layer is also vapor-tight.

5. Press mold (20) according to claim 3, characterized in that the third layer is porous.

6. Press mold (20) according to one of claims 3 to 5, characterized in that the discharge channels (231) open into a common suction channel (30).

7. Press mold (20) according to one of claims 1 to 6, characterized in that it has a further layer (24) in order to provide the press mold with an interface for connection to a corresponding machine.

8. Press mold (20) according to one of claims 1 to 7, characterized in that it is designed in several parts and a first mold half (20A), a second mold half (20B) and a mold bottom (20C).

9. Press mold (20) according to one of claims 1 to 8, characterized in that it is made of polyetherimide, amorphous polyimide (PEI) or cyclo-olefin copolymer (COC).

10. Press mold (20) according to one of claims 1 to 9, characterized in that at least the first layer (21) and the second layer (22) are manufactured together in a 3D printing process and are thus formed in one piece.

11. Press mold (20) according to one of claims 2 to 10, characterized in that the first layer (21) and the second layer (22) and the third layer (23) are manufactured together in a 3D printing process and are thus formed in one piece.

12. Press mold (20) according to one of claims 1 to 11, characterized in that the press mold (20) is completely manufactured using a 3D printing process and is thus formed in one piece.

13. Press mold (20) according to one of claims 3 to 9, characterized in that at least the first layer (21) and the third layer (23) are manufactured together in a 3D printing process and are thus formed in one piece.

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