Method for molding products from fibrous material and molding device

Abstract

A method for forming products from fibrous material and a forming device for forming products from a fibrous material are described, wherein a multi-stage pressing of preforms made of fibrous material takes place in order to improve the properties of products made therefrom and to have a significant influence on the production time.

Description

Technical area

[0001] A method for forming products from fibrous material and a forming device for forming products from a fibrous material are described.

[0002] Fibrous materials are increasingly being used to produce packaging for food (e.g., trays, capsules, boxes, etc.) and consumer goods (e.g., electronic devices, etc.), as well as beverage containers. These fibrous materials generally contain natural fibers, which are obtained, for example, from renewable resources or waste paper. The natural fibers are mixed with water and, if necessary, other additives such as starch in a so-called pulp. Additives can also affect the color, barrier properties, and mechanical properties. This pulp can contain natural fibers of, for example, 0.2 to 10 wt.%. The proportion of natural fibers varies depending on the process used to manufacture the packaging, etc., and the properties of the product to be manufactured. Fibrous materials that can be processed in a dry state are also increasingly being used.These include, for example, airlaid, fluff pulp, crepe, paper, cardboard, etc. background

[0003] The production of fiber-containing products from pulp generally takes place in several work steps. For this purpose, a fiber processing facility has several stations or forming stations. In a forming station, for example, fibers can be sucked into a cavity of a suction tool, whereby a preform is shaped or formed. For this purpose, the pulp is provided in a pulp supply, and the suction tool, with at least one suction cavity whose geometry essentially corresponds to the product to be manufactured, is at least partially immersed in the pulp. During immersion, suction occurs via openings in the suction cavity, which are connected to a corresponding suction device, with fibers from the pulp collecting on the surface of the suction cavity. The sucked-in fibers or a preform can then be transferred via the suction tool into a pre-pressing tool, where the preform is pre-pressed.For this purpose, elastic molds can be used, for example, which are inflated for compression, exerting pressure on the preforms. During this pre-compression process, the fibers in the preform are compressed and the water content of the preform is reduced. Alternatively, preforms can be prepared by scooping, in which a scooping tool is immersed in the pulp, and fibers are deposited on the molded parts of the scooping tool as it is raised.

[0004] The preforms are then pressed into finished molded parts in a hot-pressing device. Preforms are placed into a hot-pressing tool, which may have a heated lower and upper mold half. Within the hot-pressing tool, the preforms are pressed in a cavity under heat. The pressure and heat remove residual moisture, reducing the moisture content of the preforms from approximately 60% by weight before hot-pressing to, for example, 1-10% by weight after hot-pressing. The steam generated during hot-pressing is extracted through openings in the cavities and channels in the hot-pressing tool.

[0005] A manufacturing method and a fiber processing device for this purpose are known, for example, from DE 10 2019 127 562 A1.

[0006] During hot pressing, it is crucial to heat the preforms, which have a relatively high water content, sufficiently and press them for a sufficient time to achieve the desired residual moisture content in the finished product and to compress the fibers so that a finished product with the desired geometries can be manufactured. The geometry or shape of the manufactured products is subject to limitations because a relatively large deformation of a moist preform cannot be performed without damage. This results in a long cycle time, which has a detrimental impact on the entire manufacturing process and production costs.

[0007] Furthermore, it has not yet been possible to sustainably influence the shape and formation of products made from fibrous material during the hot-pressing process. Deformations such as embossing, etc., cannot be achieved, or only with great effort, because the fibrous material shrinks when the water it contains evaporates. State-of-the-art molds for producing complex geometries generally feature movable mold surfaces. Such tools are expensive to purchase and prone to failure. Furthermore, an additional control system for the movable mold surfaces is required, which increases the complexity of such a tool.

[0008] Furthermore, it has been shown that previous attempts to achieve barrier properties in products made of a fiber-containing material are either very complex and costly, not recyclable or not sufficiently impermeable. Task

[0009] The objective is therefore to provide a solution for the production of products made of fibrous material, allowing products with complex geometries to be manufactured and eliminating the disadvantages of the prior art. Furthermore, a solution is to be provided that does not require movable mold surfaces for a tool. Another objective is to achieve improved barrier properties in products made of a fibrous material. Solution

[0010] The above-mentioned object is achieved by a method for forming products from a fibrous material, which comprises at least the following steps: Providing a preform made of a fibrous material, wherein the preform has a moisture content of at most 75 wt.%, first pressing of the preform with simultaneous heat input in a first pressing device, and at least a second pressing of the preform previously pre-pressed in the first pressing device with simultaneous heat input in a second pressing device, wherein the temperature introduced during the first pressing in the first pressing device and the temperature introduced during the at least one second pressing in the second pressing device are different.

[0011] By using a two-stage pressing process, the pressing time per pressing device can be kept relatively short, so that the production time is kept low or reduced even for complex geometries and for products or preforms with a high water content and large wall thicknesses (> 1 mm). Pressing at high temperatures, which would otherwise be carried out in a pressing device as in the state of the art, can take a very long time depending on the complexity, geometry, and moisture content of the preforms, meaning that upstream and downstream processing steps must be paused. The solution presented here, in contrast, enables adaptation to, for example, the shortest processing time at an additional station (e.g., suction station, pre-press station, etc.).

[0012] Furthermore, in one of the pressing devices, additional deformation can be achieved in addition to drying ("hot pressing"). To achieve this, the temperature in the first pressing device can be higher or lower than in the at least one second pressing device. The temperature differences also enable controllable water discharge, thus avoiding damage to preforms if, for example, initial drying occurs and thus the maximum heating power is not applied. It has also been shown that the temperature difference achieves a better bonding of the fibers, whereas two pressing processes at essentially the same temperature do not achieve the desired bonding of the fibers and can even negatively influence the bond.

[0013] Additionally, the pressing force in the first pressing device can be higher, lower, or essentially the same as in at least one second pressing device. Finally, the pressing duration and the duration of the heat exposure via the first pressing device and at least one second pressing device can also differ between the at least two pressing devices.

[0014] This not only reduces the cycle time during hot pressing, but also allows the preforms to be shaped and their barrier properties to be improved. After an initial pressing, a preform can, for example, be sufficiently stable so that no additional shrinkage occurs during embossing, in which, for example, wall or base areas partially achieve a reduced wall thickness. To this end, the pressing devices can, for example, have cavities with adapted forming surfaces and geometries that differ in the first and at least one second pressing device in order to take shrinkage or deformation into account, for example. By pressing in at least two stages, the surface quality on the inside and / or outside of preforms or products can be significantly influenced. This includes embossing, for example toto introduce patterns or structures onto a surface, as well as a thermal and pressure-specific effect, which can vary in at least two pressing steps (first pressing, second pressing). Through thermal and pressure-specific effect, the surfaces in particular can be compressed more intensively, so that a barrier against liquids, gases, odors and pollutants can be achieved solely through the fiber-containing material without further additives. In further versions, definable temperature ranges and different pressures can be used to activate or strengthen the binding of additives or supplements that are mixed into the fiber-containing material in order to achieve a barrier effect. The advantage of the two-stage process can be used here, for example.In a first step, the water content of a preform is significantly reduced, so that this preform can be pressed in the at least one second pressing device during a second pressing process with higher forces and temperatures to "close" a corresponding surface. The small remaining water content can be removed from the preform via the opposite surface. Since the moisture content has already been significantly reduced beforehand, damage, etc., to the preform or product is excluded.

[0015] The first pressing and the at least one second pressing are components of a hot-pressing process, which, compared to known methods, is divided into at least two hot-pressing process steps. Preliminary pressing of moist fibrous material, as known, for example, from DE 10 2019 127 562 A1 mentioned above, differs from a hot-pressing process. Such pre-pressing can be performed additionally, especially with moist materials. During pre-pressing, however, the water is only squeezed out of the fibrous material, whereby hydrogen bonds cannot yet fully form. As is known, the water is therefore only squeezed out during pre-pressing at relatively low temperatures (e.g., < 100 °C). Dividing the hot-pressing process into at least two hot-pressing steps offers several advantages, as explained above.

[0016] Furthermore, the process is not limited to the production of products from a fibrous material in a so-called wet process, but can also be used in the production or shaping of products in a so-called dry process.

[0017] In further embodiments, the temperature introduced during the second pressing in the second pressing device can be higher than the temperature introduced during the first pressing in the first pressing device, or the temperature introduced during the second pressing in the second pressing device can be lower than the temperature introduced during the first pressing in the first pressing device. If the temperature is increased, pressing can cause an increasing release of water and an increasing bonding of the fibers (e.g. through hydrogen bonding) and thus an increase in the mechanical properties of the product to be manufactured or of the preform. If the temperature decreases, the surface of the preform or product can be reworked and, for example, refined by the at least one second pressing, whereby the required strength and the release of water have already been achieved.

[0018] In other versions, surface finishing can also be achieved by applying a higher temperature during a subsequent, at least a second pressing process. In even further versions, for example, during three pressing processes, the temperature can be applied in a high-low-high or low-high-low sequence.

[0019] In further embodiments, the first pressing (as hot pressing) can be carried out in a temperature range of 70 to 120 °C and / or the at least one second pressing (as hot pressing) can be carried out in a temperature range of 160 to 250 °C, or the first pressing can be carried out in a temperature range of 160 to 250 °C and / or the at least one second pressing can be carried out in a temperature range of 70 to 120 °C. In further embodiments, the hot pressing can be carried out, for example, at approximately 100 °C and the hot pressing at approximately 220 °C. The temperature range for hot pressing enables a reduction in the residual moisture of the preform and the formation of a relatively stable preform for further hot pressing while at the same time maintaining sufficient deformability.

[0020] The first pressing step is not a so-called pre-pressing step, which can be optionally provided in other designs. During pre-pressing, water is typically pressed out of the filter cake of the drawn-in fibers at ambient temperature (+ / - 20 degrees Celsius) to obtain a preform with, for example, a water content of 60% by weight. However, pre-pressing is generally not performed at temperatures above 100°C.

[0021] In further embodiments, first pressing tools of the first pressing device can be heated to 70 to 120 °C and / or second pressing tools of the second pressing device can be heated to 160 to 250 °C, or first pressing tools of the first pressing device can be heated to 160 to 250 °C and / or second pressing tools of the second pressing device can be heated to 70 to 120 °C. The heating can be carried out directly or indirectly, and appropriate heating devices can be provided.

[0022] In further embodiments, the moisture content of the preform can be reduced to 30 to 50 wt.% during the first pressing step in order to achieve the required formability while maintaining sufficient strength. Strength refers to the properties of the preform, which relate to the cohesion of the material used. After the first pressing step at a lower temperature ("hot pressing"), the individual fibers of the preform are at least partially bonded, so that the material is essentially stable but still sufficiently deformable. This prevents "tearing" or similar phenomena during deformation, particularly during forming or embossing, since the geometry of a preform is already essentially predetermined during the first pressing step.Excessive residual moisture in the preform would prevent deformation because compression / stretching could cause the fibers to "flow" or the material to tear in the deformed area, which would damage the preform.

[0023] The reduction in moisture content can be determined based on the temperature in the pressing equipment, the pressing duration, and the pressure. It has been shown that adjustments to the parameters temperature, pressure, and dwell time (pressing time) have different effects on the result of each pressing step, so that the reduction in moisture content and surface quality can be specifically influenced by appropriate selection of parameters.

[0024] Temperature control during hot pressing and hot pressing makes it possible to take into account different fibers, pulp compositions, geometries of the products to be manufactured, and wall thicknesses, etc., and to provide the appropriate temperatures. For example, different fibers may require a different hot pressing temperature to achieve the desired formability. Furthermore, a different hot pressing temperature may be required, particularly for thicker preform walls than for thinner ones. The pressing force and pressing time during hot pressing and hot pressing can also vary and / or be adjusted depending on the material used (pulp, fibers, etc.) and the geometry and dimensions of a preform or product.

[0025] In further embodiments, the moisture content of the preform can be reduced to 1 to 30 wt.% during the second pressing.

[0026] In other versions, the desired residual moisture content in the preform can be achieved during the first pressing or, if more than three pressing processes are performed, during at least one second pressing. During at least one further pressing, pressing then takes place in a dry process, as is known, for example, from the forming of paper or the deep drawing of crepe or airlaid. This means that a combination of wet forming and dry forming takes place during hot pressing. In even more versions, a final forming can take place in the dry-hot pressing step.

[0027] In further embodiments, not only can different temperatures be used during the first pressing and at least one second pressing, but the first and second pressing tools can also be heated to different degrees at different locations on the preform. For example, this can ensure that during the first pressing, a first region of a preform is heated more intensely than a second region of the preform, so that during the subsequent second pressing, the second region is still sufficiently flexible for forming and / or embossing, but the first region is already correspondingly deeply formed, or at least more deeply formed than the second region.

[0028] In further embodiments, at least one embossing of the preform previously pre-pressed in the first pressing device can take place between and / or during the first pressing and the second pressing, wherein the embossing can include the introduction of contours, grooves, etc. In particular, the embossing cannot be understood as pressing as in the first and at least second pressing step. In further embodiments, the embossing takes place during a first or at least a second pressing. The embossing does not represent the application of coatings, but can serve as a preparatory measure or for the subsequent compaction of previously applied layers / barrier layers.

[0029] In further embodiments, at least one coating of the preform previously pre-pressed in the first pressing device can take place between the first pressing and the at least one second pressing.

[0030] In further embodiments, an additional coating can be carried out before the first pressing and / or after at least one second pressing.

[0031] In further embodiments, the coating may comprise at least a partial application of at least one additional layer by spraying, dipping, scooping, laminating, and / or printing. During the coating process, additives (such as SiOx) may be applied to a surface of a preform and / or product. After the coating has been applied, a second pressing step may take place to subject the surface to a stronger bond with the coating or to insert the coating into the surface of the fibrous material ("press in"). Furthermore, for example, at least one additional layer of fibers, nanofibers, or so-called MFC (microfibrillated cellulose) may be applied after a first pressing step and before a second pressing step.After the first pressing, the surface of the preform still contains sufficient moisture to bond with the fibers of the preform located beneath the coating during the second pressing ("fibril aggregation"). The applied fiber layer is bonded to the surface of the preform in the at least one second pressing step, forming, for example, a barrier layer and / or imparting a special, usually very fine, smooth finish to the surface.

[0032] The application of different additives or fibers enables the provision of different properties. The layers can be applied in various ways. In further embodiments, several different layers can be applied to at least part of an inner and / or outer surface of a preform and / or product. In still further embodiments, coating steps can be performed before a first compression, between a first and a second compression, and / or after a second compression.

[0033] In further embodiments, the first pressing and the at least one second pressing may be part of a hot pressing process as described above, which applies to all embodiments disclosed herein.

[0034] In other versions, pre-pressing can take place before the first pressing, whereby water is pressed out of the preform.

[0035] In further embodiments, the at least one second pressing can result in a surface finishing of the preform previously pre-pressed in the first pressing device. Surface finishing can, for example, include the creation of a smooth surface ("high-gloss surface"). Conventional products made of a fibrous material, in particular those from a wet-molding process, have small elevations on their surface that result from pores in the cavities in a hot-pressing tool (pressing tool, molding tool), through which water vapor is extracted during pressing. During surface finishing, these elevations can be pressed "smoothly." For this purpose, the surfaces in the cavities of a second pressing tool or molding tool can be smooth, so that the elevations are pressed and the surface of the preforms or molded bodies is smooth.In further embodiments, at least one pressing tool of the at least one second pressing device or at least one second molding tool can have steam holes located at a different location than the steam holes of a first pressing tool of the first pressing device, so that the previously created elevations are pressed flat, and no elevations are formed at the steam holes of the at least one second molding tool due to the low moisture content in the preform, because the material is already over-compacted and dried. Such steam holes in cavities of a second molding tool can, for example, dissipate escaping residual moisture.

[0036] Surface finishing can also include embossing, for example, where patterns or structures are embossed. Embossing compresses the fibrous material, which has already been pressed, improving strength and other material properties. In particular, the surface exhibits a significantly better surface quality (visual and tactile).

[0037] In further embodiments, functional and / or design areas can be reinforced during at least one second pressing step. For example, undercuts or edges, etc., can be re-pressed to make them more stable (e.g., by embossing and introducing structures that further compact the material). Furthermore, the reinforcement can result in the final formation of the functional and / or design areas, although the formed functional and / or design areas may previously have been only partially formed.

[0038] In further embodiments, punching can occur during the first pressing and the at least one second pressing, with the punching occurring to a different extent during the first pressing and the at least one second pressing. Pre-punching can thus occur first, with areas of the preform being only partially pre-punched, i.e., both in terms of punching depth and punching extent (length, width), and can be finally or additionally punched after or during the at least one second pressing. Punching can, for example, take place in the mold, which can have additional punching tools (blades, etc.).

[0039] Products manufactured using the aforementioned processes can include, for example, food packaging (e.g., trays, capsules, boxes, lids, etc.) and packaging for consumer goods (e.g., electronic devices, hygiene products, tools, cutlery, etc.), as well as beverage containers and lids for these. They can also include containers for plants (e.g., flower pots, etc.) and decorative elements.

[0040] The above-mentioned object is also achieved by a device for forming products from a fibrous material according to one of the methods specified above, at least comprising a first pressing device with first pressing tools, and at least one second pressing device with second pressing tools.

[0041] The technical teaching presented herein enables the production of products from a fibrous material that is provided as a preform with a relatively high residual moisture content of at most 75 wt.%, e.g., approximately 60 wt.%, whereby the product exhibits no defects, such as cracks, etc., after compression. The technical teaching also enables the production of products from fibrous material with a relatively low residual moisture content, whereby, compared to known dry forming, a special surface quality and the creation / improvement of special design elements (functional: e.g., undercut) are enabled.

[0042] For example, complex geometries, e.g. in the area of ​​an edge, can be created by two-stage pressing, with second pressing tools being designed accordingly for the formation of an edge.

[0043] In further embodiments, the first pressing tools and / or the second pressing tools can be heated, thus further improving the two-stage process for producing a product, such as a container, with a rim. For example, in a first step, a preform of the product can be pre-pressed using the first pressing tools in accordance with the final geometry in the area of ​​its main body and in the area of ​​the rim. By applying heat, the moisture content of a main body and an rim can be reduced in the first pressing device, and the fibers can be bonded to one another.It is crucial that the preform is only heated to a certain extent in the first pressing device so that the preform is still sufficiently flexible after pressing in the first pressing device to be able to be deformed in the edge region in the second pressing device when the second pressing tools are closed. The final production by hot pressing in at least one second pressing device with the second pressing tools closed can take place at a higher temperature than the heating in the first pressing device, whereby the water bound in the fibers evaporates and the preform is hot-pressed into the finished product. Alternatively, certain effects can be achieved by applying the opposite temperature to the fiber-containing material, as described above.

[0044] The first pressing tools and / or the at least one second pressing tool can be heated to the required temperatures for pressing using heating devices. Such heating devices can, for example, be electrical or hydraulic heating devices and, for example, have heating elements. Electrical heating elements can, for example, be heating cartridges, the temperature of which can be regulated according to the provided supply current. The pressing tools can thus be heated directly via the heating cartridges. Hydraulic heating devices can, for example, have channels running through the pressing tools, with a temperature-controlled oil circulating in the channels. The heating of the pressing tools can occur directly by heating the pressing tools or indirectly by heating a tool plate on / to which the pressing tools are attached.In further embodiments, temperature detection means can be provided which detect the temperature of the pressing tools and / or the tool plate in order to regulate the temperature of the pressing tools in accordance with the detected values.

[0045] In further embodiments, the size of cavities in the first pressing device and the second pressing device can be different, taking into account the shrinkage of the volume of the product or preform between the first pressing in the first pressing device and a second pressing in the second pressing device.

[0046] The device can further comprise units for coating before a first pressing, between a first and a second pressing, and / or after a second pressing. In the device for molding products from a fibrous material, after the at least two-stage pressing, the finished products can be subjected to further processing steps, such as filling, sealing, etc.

[0047] Further features, embodiments and advantages emerge from the following presentation of embodiments with reference to the figures. Short description of the characters

[0048] In the drawings shows: Fig. 1 is a schematic representation of a process for producing products from a fibrous material; and Fig. 2 is a schematic representation of a fiber processing device with a hot-pressing station with at least two pressing devices. Detailed description of implementation examples

[0049] The following figures illustrate exemplary embodiments of the technical teaching described herein with reference to the figures. The same reference numerals are used for identical components, parts, and processes in the description of the figures. Components, parts, and processes that are not essential to the technical teaching disclosed herein or that would be obvious to a person skilled in the art are not explicitly shown. Features stated in the singular are also included in the plural, unless explicitly stated otherwise. This applies in particular to statements such as "a" or "an."

[0050] Fig. 1shows a process sequence for the production of products from a fibrous material, wherein preforms made of a fibrous material are first prepared, which are then pressed under thermal influence. The preparation of the preforms can be carried out as described above, whereby fibers are sucked from an aqueous solution (pulp) and three-dimensional preforms are formed, which essentially already have the shape of the products to be manufactured. In addition, additives and supplements, such as starch, chemical additives, wax, etc., can be added to a pulp in order to determine the properties of the products to be manufactured (e.g.

[0051] Barrier properties) and processability. The fibers can be, for example, natural fibers, such as cellulose fibers, or fibers from a fibrous source material (e.g. waste paper). For example, biodegradable cups, capsules, bowls, plates and other shaped and / or packaging parts (e.g. as holder / support structures for electronic devices) can be manufactured. Since a fibrous pulp with natural fibers can be used as the starting material for these products, the manufactured products can themselves be used as starting material for the production of similar products after their use or can be composted because they can generally be completely decomposed and do not contain any harmful, environmentally hazardous substances.

[0052] In further embodiments, the preforms can be subjected to a pre-pressing step. The preforms are then pressed into three-dimensional products in a hot-pressing device under pressure and heat. Unlike known methods for forming such products, the pressing (hot pressing) here takes place in at least two steps: a first pressing step and at least a second pressing step. In further embodiments, a second pressing step can be followed by at least a third pressing step, and so on. Each pressing step can specifically influence various properties of the preforms or products.

[0053] First, at least one preform is provided. The preform may, for example, have been subjected to pre-pressing to remove water. However, pre-forming is not mandatory. For the molding process, the preform has, for example, a residual moisture content of no more than 75 wt.%. The preform is then introduced into a first pressing device. For this purpose, the preform is placed or inserted onto a contact surface of the cavity of the first pressing device. The first pressing device is open, with two first pressing tool halves displaced relative to one another. After the preform has been introduced, the first pressing tool halves are displaced relative to one another until the first pressing device is closed and forms a closed cavity for the preform.In the first press, a first pressing ("hot pressing") is then carried out at a relatively lower temperature than the pressing in a second press. During hot pressing, the moisture content of the preform is reduced and the preform is preformed.

[0054] After the preform has been hot-pressed, the first pressing device is opened by relative displacement of the first two pressing tools, and the hot-pressed preform is removed from the first pressing device. The hot-pressed preform is then fed to the second pressing device. The hot-pressed preform is placed or inserted onto a contact surface of a cavity of the second pressing device. The first pressing device is open, with two first pressing tool halves displaced relative to one another. After the preform has been inserted, the second pressing tool halves are displaced relative to one another until the second pressing device is closed, forming a closed cavity for the preform. A second pressing process ("hot pressing") is then carried out in the second pressing device at a higher temperature than the pressing in the first pressing device.During the second pressing step, the moisture content of the preform is further reduced, and the previously hot-formed preform is pressed into a product. The resulting product is essentially no longer deformable and has a relatively low residual moisture content (1-20 wt.% water). After the hot pressing, the second pressing device is opened by relative displacement of the second pressing tools, and the hot-pressed product is removed.

[0055] The first pressing tools and the second pressing tools have contact surfaces on molding devices, which can be moved relative to one another to form a molding space (cavity). The molding devices are designed such that the molding devices on one pressing tool half are essentially formed as negatives, and the molding devices opposite on the other pressing tool half are essentially formed as positives of the products to be formed. The molding devices can be provided as an integral component of the tool plates of the pressing tool halves or can be interchangeably connected (e.g., screwed) to the tool plates of the pressing tool halves.

[0056] Furthermore, the first pressing devices and the second pressing devices can in particular have a plurality of cavities or mold spaces and molding devices.

[0057] Furthermore, the mold cavities of the first pressing device can have a different extension and configuration than the mold cavities of the second pressing device, both to accommodate shrinkage of the preforms after the first pressing and to introduce structures or similar features into the surface of already hot-formed preforms. For this purpose, for example, the molding devices of the second pressing device can have a patterned or structured surface on their contact surfaces in order to apply a pattern or structuring to the surface of a hot-formed preform during the second pressing.

[0058] In further embodiments, embossing of patterns or the like can take place between the first pressing in the first pressing device and the second pressing in the second pressing device. For this purpose, the preforms are already sufficiently stable after the first pressing and can then be embossed with a pattern (e.g. brand, slogan, etc.). For this purpose, an embossing device (e.g. embossing station) is arranged between the first pressing device and the second pressing device. The tools for embossing can be designed similarly to the forming devices of the first pressing device and the second pressing device. In further embodiments, embossing means (e.g. punches or the like) can act only on one area of ​​a hot-formed preform.In further embodiments, embossing can also take place with the first or second pressing devices open, with the hot-formed preforms resting with their inner or outer surface on a contact surface of a forming device of the first pressing device or the second pressing device. Embossing then takes place after the first pressing in the first pressing device or before the second pressing in the second pressing device with the respective pressing tool halves open. For this purpose, embossing tools can, for example, be moved relative to the pressing tool halves with the preforms. The embossing tools then press from this position against the preforms for embossing. In further embodiments, the pressure can be exerted via the opposite pressing tool half, which is moved with less pressure and a shorter stroke than in a regular first or second pressing.Subsequently, embossed and thermoformed preforms can be hot-pressed in a second pressing step in order to cure the previously applied embossing by drying the entire preform during the hot pressing step.

[0059] In addition, the different design of the cavities or molding devices for the press tool halves allows for more intensive compression at high pressure after hot pressing or the initial pressing. This allows the wall thickness, already reduced by drying during hot pressing, to be further reduced, making the finished product very stable and strong. Furthermore, this can significantly influence the surface properties. For example, very high surface compaction can be achieved, which can improve or even provide barrier properties (moisture, gas, and odor permeability).

[0060] In further embodiments, coating with additives, fibers, etc. can take place before the first pressing, between the first pressing and the second pressing, as well as after the second pressing, in order to influence the surface quality and barrier properties. A first and / or second pressing after coating can, for example, lead to the activation of additives contained in the fiber-containing material. In addition to pressure, the behavior and bonding ability of materials with one another or with fibers can also be influenced using heated molding equipment. In further embodiments, coating between two pressing steps can be used to achieve a targeted layer build-up, wherein the connection area between at least one coating layer and the adjacent layer (e.g. fiber layer) is relatively small.In further embodiments, several layers can be applied between the first pressing and the second pressing, whereby the hot-pressed preform is hot-pressed again after coating.

[0061] Dividing the pressing process into at least a first pressing and at least a second pressing allows preforms to be pressed for a sufficiently long time and at a sufficiently high temperature, while significantly reducing the time required for pressing under pressure and simultaneous exposure to temperature. It is clear that with additional pressing devices (third pressing device, fourth pressing device, etc.), the time required for each pressing device can be reduced even further.

[0062] By dividing the system into multiple presses, each of which can perform pressing at different temperatures, pressures, and durations, the quality of the products manufactured in this way can be significantly improved. Furthermore, barrier properties can be significantly improved. It is particularly important to note that an optimal fiber bonding effect cannot be achieved in a single press station due to the limitation to a single temperature range for pressing.

[0063] The first and second pressing devices have appropriate temperature control devices for the temperature effect, which can provide the temperature to the contact surfaces of the cavities or mold devices in a controlled manner via a controller and, if necessary, additional units. For example, electrically controllable heating elements are provided in the tool plates and / or mold devices, which can be easily controlled via a controller.

[0064] In further embodiments, the temperature during a first pressing can be higher than during at least a second pressing, wherein the bonding of the fibers of the fibrous material is thus largely completed during the at least one second pressing. Furthermore, embossing of the preforms can also take place in the molding tools themselves, wherein the molding tools have a corresponding surface in the cavities. Furthermore, the molding tools can have punching tools which punch the preforms or products differently in the pressing devices when the tool halves of pressing devices are closed. In still further embodiments, punching stations can be provided which are arranged downstream of the pressing devices. It is also possible to provide only one punching station, wherein pre-punching can take place beforehand in at least one pressing device.

[0065] Furthermore, with regard to the design of a fiber processing device 10 in Fig. 2 Multi-stage hot pressing can be carried out on preforms that have a low moisture content and are made from a relatively dry material (e.g. Airlaid etc.).

[0066] In particular, the processes described herein can also include surface treatment through at least a two-stage hot-pressing process in different hot-pressing tools (pressing devices), which provides compaction and / or smoothing of surfaces. Furthermore, the introduction of fine structures, e.g., intersecting lines, etc., can achieve homogeneous compaction, which is generally not possible in a single-stage process because the fibrous material lacks the necessary bond for compaction. Without pre-compaction during the initial pressing, fibrous material could adhere ("stick") to the cavity surface during embossing. This is prevented by the solution described here.

[0067] Fig. 2shows a schematic representation of a fiber processing device 10 with a hot-pressing station 30 with at least two pressing devices 32, 34. In the exemplary embodiment shown, the hot-pressing station 30 of the fiber processing device 10 has a first pressing device 32 for pressing preforms made of fibrous material with a high water content of, for example, 50 to 70 wt. % (for example, approximately 60 wt. %), as described above. The first pressing in the first pressing device 32 takes place in a temperature range of 70 to 120 °C. For this purpose, the pressing tools or pressing tool halves as well as the molding devices can be heated via at least one temperature control device 40. The temperature control device 40 can, for example, comprise electrically controllable heating cartridges which are accommodated in tool bodies of the pressing device 32 or in the associated molding devices.

[0068] The hot-pressing station 30 further comprises a second pressing device 34 for pressing preforms previously pressed in the first pressing device 32 at a lower temperature. After the first pressing, the previously pressed preforms have, for example, a water content of 30 to 50 wt. %, for example 35 to 50 wt. %, in particular 40-50 wt. %, and are thus sufficiently flexible and formable so that, for example, edge, bottom and / or side forming of the preforms can take place without them being damaged or destroyed. For this purpose, the forming device of the second pressing device 34 has an appropriate geometry. The second pressing can be carried out for final drying in a temperature range of 160 to 250°C. For this purpose, the pressing tools or pressing tool halves as well as the forming devices are heated accordingly via the at least one temperature control device 40. The second pressing tools orPress tool halves as well as the forming devices of the second pressing device 34 can be heated to 160 to 250 °C for this purpose.

[0069] In further embodiments, the first pressing in the first pressing device 32 and the second pressing in the second pressing device 34 can take place at substantially the same temperatures. In still further embodiments, the first pressing in the first pressing device 32 can take place at higher temperatures than the second pressing in the second pressing device 34. For example, the surface of the preforms or a previously applied coating can be specifically thermally bonded or treated with a bonding layer / surface of the fibrous material.

[0070] The fiber processing device 10 further comprises a controller 20 which is used to control the Fig. 2 shown components and other components of the fiber processing device 10.

[0071] The fiber processing device 10 can, for example, have supply units, for example interfaces for the supply of media (e.g. water, pulp, compressed air, gas, etc.) and energy (power supply), at least one suction device, line systems for the various media, pumps, valves, lines, sensors, measuring devices, a BUS system, etc. as well as interfaces for bidirectional communication via a wired and / or wireless data connection. Instead of a wired data connection, a data connection via a fiber optic cable can also exist. The data connection can, for example, exist between the controller 20 and a central controller for several fiber processing devices 10, to a fiber processing plant, to a service point and / or other devices. The fiber processing device 10 can also be controlled via a mobile device, such as aa smartphone, tablet computer, or the like. Furthermore, the controller 20 can be in bidirectional communication with an HMI (Human-Machine Interface) panel via a bus system or a data connection. Additionally or alternatively, additional input devices, such as a keyboard, a joystick, a keypad, etc., can be provided on an HMI panel for operator input. These can be used to change settings and influence the operation of the fiber processing device 10.

[0072] In further embodiments, the fiber processing device 10 can comprise devices for preforming and sucking fibers to form preforms from a pulp. Furthermore, the fiber processing device 10 can comprise additional upstream and downstream processing stations. Furthermore, as already explained above, the fiber processing device 10 can comprise coating stations at various points in the production process, wherein material (fibers, SiOx, additives, wax, etc.) for coating can be supplied to these stations via additional devices. List of reference symbols

[0073] 10Fiber processing device 20Control system 30Hot pressing station 32First pressing device 34Second pressing device 40Temperature control device

Claims

1. A method for forming products from a fibrous material, comprising at least the following steps: - providing a preform made from a fibrous material, wherein the preform has a moisture content of at most 75% by weight, - first pressing of the preform with simultaneous introduction of heat in a first pressing device, and - at least a second pressing of the preform previously pre-pressed in the first pressing device with simultaneous introduction of heat in a second pressing device, wherein - the temperature introduced during the first pressing in the first pressing device and the temperature introduced during the at least one second pressing in the second pressing device are different.

2. The method according to claim 1, wherein - the temperature introduced during the second pressing in the second pressing device is higher than the temperature introduced during the first pressing in the first pressing device, or - the temperature introduced during the second pressing in the second pressing device is lower than the temperature introduced during the first pressing in the first pressing device.

3. The method according to claim 1 or 2, wherein - the first pressing is carried out in a temperature range of 70 to 120 °C and / or the at least one second pressing is carried out in a temperature range of 160 to 250 °C, or - the first pressing is carried out in a temperature range of 160 to 250 °C and / or the at least one second pressing is carried out in a temperature range of 70 to 120 °C.

4. Method according to one of claims 1 to 3, wherein - first pressing tools of the first pressing device are heated to 70 to 120 °C and / or second pressing tools of the second pressing device are heated to 160 to 250 °C, or - first pressing tools of the first pressing device are heated to 160 to 250 °C and / or second pressing tools of the second pressing device are heated to 70 to 120 °C.

5. A method according to any one of claims 1 to 4, wherein during the first pressing the moisture content of the preform is reduced to 30 to 50 wt.%.

6. A method according to any one of claims 1 to 5, wherein during the second pressing the moisture content of the preform is reduced to 1 to 30 wt.%.

7. Method according to one of claims 1 to 6, wherein between and / or during the first pressing and the at least one second pressing, at least one embossing of the preform previously pre-pressed in the first pressing device takes place.

8. Method according to one of claims 1 to 7, wherein between the first pressing and the at least one second pressing, at least one coating of the preform previously pre-pressed in the first pressing device takes place.

9. Method according to one of claims 1 to 8, wherein an additional coating is carried out before the first pressing and / or after the at least one second pressing.

10. The method according to claim 8 or 9, wherein the coating comprises at least a partial application of at least one additional layer by spraying, dipping, scooping, laminating and / or printing.

11. The method according to any one of claims 1 to 10, wherein the first pressing and the at least one second pressing are part of a hot pressing process.

12. The method according to any one of claims 1 to 11, wherein pre-pressing is carried out before the first pressing, wherein water is pressed out of the preform.

13. Method according to one of claims 1 to 12, wherein the at least one second pressing results in a surface finishing of the preform previously pre-pressed in the first pressing device.

14. Method according to one of claims 1 to 13, wherein functional and / or design areas are reinforced during the at least one second pressing.

15. The method according to any one of claims 1 to 14, wherein punching occurs during the first pressing and the at least one second pressing, wherein the punching occurs to a different extent during the first pressing and the at least one second pressing.

16. Apparatus for forming products from a fibrous material according to one of the methods according to claims 1 to 15, comprising at least - a first pressing device with first pressing tools, and - at least one second pressing device with second pressing tools.

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