Method for manufacturing molded products from multilayer paper, molded products made of paper, and devices for manufacturing the same.

Abstract

The present invention relates to a method for producing molded products from multi-layer paper, which eliminates a subsequent drying step and also makes it possible to produce molded products that are fully compostable and are not limited to only flat angles between flat areas in terms of their shape. The present invention further relates to the corresponding molded products made of paper, and to a device for carrying out the method.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a molded product from multi-layer paper that enables the production of a completely compostable molded product that omits the subsequent drying step and is not limited to only flat angles between flat regions with respect to its shape. The present invention further relates to a corresponding molded product made of paper and a device for performing the method.

Background Art

[0002] Due to the increasing international mail-order trade of all kinds of goods, the demand for packaging materials is also increasing. In addition to thermoformed packaging made from thermoplastic plastics, packaging materials that are compostable for environmental protection are also becoming increasingly important. Boxes for transporting fragile eggs are usually made of cardboard and meet the criteria for compostability. These egg boxes are manufactured using a process known as fiber casting, where the first step usually involves dissolving unwanted paper from cardboard in water for the purpose of preparing the paper fibers to be defibrillated into a new shape, except for small fibers of the paper fibers. In the second step, a first forming tool is immersed in a container having a fiber pulp, and excess water is sucked out from below the container, so that the paper fibers are collected on the formed top side of the tool. Then, a second forming tool forms the top side of the fiber pulp deposited on the first forming tool, where both tools are removed from the container above, together with the fiber pulp between the two tools. In the final step, the preformed fiber pulp is placed in a drying oven, where the fibers adhere tightly together so that no glue needs to be added. After the drying step, the molded part is ready for use. The disadvantages of this method are, on the one hand, that the high water content of this method consumes energy and requires a drying step, and on the other hand, that the production speed enabled by this method is slow. Therefore, the ecological footprint of the molded products manufactured in this way is significantly worse than what many users think.

[0003] Many types of packaging materials are intended only to give the impression of meeting environmental protection requirements, as shown in, for example, patent specification DE102013103743B4. One drawback of plastic packaging materials manufactured using thermoforming is that they are immediately recognizable as being made of plastic, which is undesirable in many applications today, for example, because the products contained within such packaging materials may have environmental protection aspects, or the packaging materials must at least give an environmentally friendly impression for other purposes. This patent document also mentions the limitations of cardboard packaging materials as an alternative due to the inability to freely define their shape. The object of the invention presented therein is to create a thermoformed packaging material that, on the one hand, consists of a thermoformed plastic body, and on the other hand, consists of an insert made of another material, such as paper, which is a glue-free integral part of the packaging material that can be separated from the plastic body without problems after use. This represents a further advancement in thermoformed plastic packaging materials, which are later flocked using paper fibers to give them the appearance of packaging made from paper materials. However, it unfortunately does not allow for the separation of components with reasonable effort during disposal.

[0004] Utility model DE202018104061U1 also addresses the environmental protection aspect of packaging materials. According to this utility model, there are numerous types of packaging materials available that are made of plastic or bleached paper / cardboard and printed to resemble paper. In some cases, the use of special varnish can give them a feel that is very similar to paper. The aim is to provide consumers with the naturalness of the "look and feel of paper" that they expect, but this is not actually sustainable. The purpose described in this utility model specification is to provide a collapsible box for frozen foods, which can be oil-treated or coated with wax or silicone. So-called kraft paper is used here. The drawback of this is that it is also limited in shape, and it is mainly possible to provide only collapsible boxes.

[0005] Simply pressing multilayer paper, such as paper plates with a typical corrugated edge, into a molded product is limited in its molding process due to the insufficient elasticity of the paper and the fact that it can only achieve very flat angles between flat areas or shallow corrugations. Such products further require the addition of glue to ensure tight adhesion between individual paper layers. However, this hinders complete compostability. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] DE102013103743B4 [Patent Document 2] DE202018104061U1 [Overview of the project] [Problems that the invention aims to solve]

[0007] Therefore, the object of the present invention is to provide a fully compostable, elastomer- and glue-free molded product made of paper that can be manufactured by a method that is faster and more energy-efficient than conventional fiber casting methods, while having fewer constraints on its molding compared to molded products manufactured by methods other than fiber casting that require the use of glue. At the same time, a method for manufacturing such a molded product made of paper is presented, and furthermore, a device for carrying out such a method is provided. [Means for solving the problem]

[0008] The problems mentioned are solved by the method according to claim 1, the molded product according to claim 13, and the device according to claim 14, and hereby advantageous embodiments are obtained from each of the subordinate claims.

[0009] According to claim 1, the present invention relates to a method for producing a molded product from multilayer paper, wherein each paper layer has a plurality of free fiber ends on its surface. These fiber ends are important in the method because they are oriented laterally to the paper layers to ensure close adhesion to one another while the paper layers are pressed to form a desired molded product. Accordingly, the method includes a first step in which a plurality of paper layers arranged vertically are fed between a positive mold and a negative mold complementary to the positive mold of a pressing tool. In a second step, the free fiber ends, which are oriented laterally to the paper layers, are aligned, here in which a gas or gas mixture, preferably ambient air, is drawn through and through the paper layers, here in which the flow direction of the gas or gas mixture corresponds to the desired alignment of the fiber ends, ideally laterally to the top and bottom sides of the paper layers. The fiber ends are aligned upstream of the pressing tool or preferably within the pressing tool, i.e., between the positive and negative molds of the pressing tool. In the third step, individual paper layers are pressed to form molded products corresponding to positive and negative molds and removed from the pressing tool without requiring any other steps, such as an energy-intensive drying step, apart from the separation and cutting during the suitable feeding of continuous paper layers in the first method step.

[0010] It is advantageous that the second method step is performed between the positive and negative molds of the pressing tool. Preferably, a pressing tool is used which has at least one pressing surface that is gas permeable or porous in at least some areas, so that gas or a gas mixture is drawn in or supplied through one or more such pressing surfaces to align the fiber ends. In this way, the flow direction comes to correspond to a vector oriented perpendicular to the desired shape.

[0011] To form the intended molded parts using this method, it is advantageous to use crepe-processed cellulose-containing tissue paper that is expandable by 20% or more in at least a partial area. Since the outer paper layer expands and contracts more than the inner paper layer when the orientation changes within the mold, it is advantageous to crepe the paper used so that it can expand and contract by 50% or more in at least a partial area, for example, when two flat areas of the molded part are formed at an angle of approximately 90 degrees. For example, 20% expandability means that a paper layer of, for example, 100 cm in length can be expanded to a length of 120 cm without tearing.

[0012] Preferably, by aspirating a gas or gas mixture in the second method step, a negative pressure relative to the ambient pressure is created for at least a short time because the fiber ends are very well aligned in this case, which is advantageous for adhering the individual paper layers to each other after the third method step. Furthermore, it is advantageous to localize the solvent or solvent mixture, specifically water, on most of the surface of the paper layers by spraying or evaporating it at a slightly earlier stage, or doing both simultaneously, so as not to penetrate deep into the individual paper layers, because the solvent or solvent mixture can evaporate more rapidly as a result of aspirating or supplying the gas or gas mixture acting in the second step compared to the case where the same amount of solvent or solvent mixture permeates the individual paper layers uniformly and completely. During accelerated evaporation, the fiber ends are straightened in the desired manner in the transverse direction to the surface of the paper layers.

[0013] In a preferred implementation of this method, the solvent or solvent mixture content is reduced to less than 5% of the initial content by raising the ambient temperature, which can be achieved by aspirating a gas or gas mixture, and, unless the solvent or solvent mixture is water, by heating the pressing tool to 100°C to 350°C. When water is used, which is advantageous in terms of safety in this method, the moisture content of the ambient air at 20°C, 50% relative humidity, and a periodic air pressure of 1000 hPa is reduced to at least equilibrated or beyond in the second and third method steps, because, under the conditions described, and in practice, paper does not completely eliminate water. Equilibration does not mean that the ambient air and the molded part have the same water content, but rather that equilibration is achieved according to their respective absorption capacities. Substitutes for water as a solvent include, for example, azeotropic ethanol / water mixtures, isopropanol / water mixtures, or solvent mixtures that evaporate more quickly than water, such as isopropanol.

[0014] As already mentioned, it is advantageous to spray or evaporate a solvent or solvent mixture onto individual paper layers. This is advantageous to do so between at least two spaced-apart paper layers, preferably between vertically arranged paper layers. Spacing can be created with the assistance of a separation device during the principle continuous feeding of paper layers from the paper roll, which is paused only briefly for pressing treatment, and this spacing allows for the insertion of a spray head or evaporation nozzle between the paper layers. However, such effort can be avoided by using paper layers with an appropriately adjusted solvent or solvent mixture content from the start, in which case a compromise may be made regarding the adhesion quality between individual paper layers in the finished molded product.

[0015] The pressure applied in the third method step to press the paper layer for the purpose of forming molded products corresponding to the positive and negative molds of the pressing tool is preferably at least 100 kg per square centimeter. Of course, higher pressure may be applied if necessary depending on the shape. During pressing, it is advantageous to process using a high-temperature pressing tool having a temperature of 100°C to 350°C, because this promotes the desired evaporation of the solvent or solvent mixture, and thus promotes the alignment of the fiber ends.

[0016] The method described is advantageous in that paper can be used as a starting material, and that it is not necessary to add glue to the method, for example, to enhance the adhesion between individual paper layers. This means that the molded products produced using this method are fully compostable and, of course, recyclable.

[0017] Against the background of the presented method, it is possible to provide a molded product made from multilayer paper that, by crepe processing alone, has an elasticity of 20% or more, preferably 50% or more, in at least some areas, is fully compostable, and has directly adjacent flat regions that form angles greater than 90° and less than 150°. Furthermore, this makes it possible to clearly distinguish such a molded product from commercially available egg cartons manufactured using, for example, fiber casting, because in cases such as fiber casting, the elasticity unrelated to the crepe processing of the paper is not definitive.

[0018] Finally, a device for manufacturing a molded product from multi-layer paper is briefly presented, having a roller configuration for feeding paper to a pressing tool having a positive mold and a complementary negative mold, where the pressing tool can be heated from 100°C to 350°C, at least one of the pressing surfaces is gas-permeable or porous in at least some regions, and is connected via a hose to a compressor or vacuum pump for sucking or supplying a gas or gas mixture, preferably ambient air, through the pressing surface.

[0019] It is advantageous that an outlet for a solvent or solvent mixture, preferably water, designed to atomize or evaporate the solvent or solvent mixture is arranged upstream of the pressing tool, where an outlet, which can be, for example, a spray head, a spray multi-head, or an evaporation nozzle, or an evaporation multi-nozzle, for a transfer device for individual paper webs is configured to be arranged between the paper layers.

[0020] The present invention will be described in more detail below with reference to the drawings, but the present invention is not limited only to the examples shown.

Brief Description of the Drawings

[0021] [Figure 1] FIG. 1 shows a sketch of a device for manufacturing a molded product from multi-layer paper. [Figure 2] FIG. 2 shows an example of a molded product manufactured from multi-layer paper.

Embodiments for Carrying Out the Invention

[0022] Figure 1 shows a sketch of a device for manufacturing a molded product from multi-layer paper. It is not necessarily arranged on the side of the pressing tool (7) as shown, and a roller configuration can also be arranged above the pressing tool (7) to utilize the force of gravity, for example, when feeding the paper. Here, individual paper layers (3) can be seen, which are separated from each other in a simple manner by an outlet (4) for a solvent or solvent mixture. The individual paper layers (3) can also be separated from each other by an additional separating device (not shown) arranged upstream of the outlet (4). The multi-layer paper fed above the outlet is guided to the pressing tool (7), and the positive mold (5) of the pressing tool (7) engages with the pressure within the complementary negative mold (6), thereby enabling the formation of the fed paper into the desired shape, which can be a very schematic molded product (8) here, and is separated as individual parts by being cut along a cutting edge (9) as schematically depicted by the previously formed molded product (10). The pressing surfaces (5a, 6a) have perforations (not shown), and through these perforations, a gas or gas mixture, which is ambient air in this case, is sucked even during the pressing process. Thereby, a negative pressure with respect to the ambient pressure is created, at least for a short time. The hoses connecting these perforations to a vacuum pump (not shown) preferably pass through the depicted cover of the pressing tool. For simplicity, the supply of a solvent or solvent mixture intended to moisten the paper layers is not shown either.

[0023] Figure 2 shows an example of a somewhat more complex molded product manufactured from multi-layer paper by the method described above. Further, on the end face of the molded product (11), two directly adjacent flat regions (12, 13) forming an angle slightly greater than 90° but less than 150° are shown. This is possible without adding an elastomer only when, in the case of manufacturing from multi-layer paper, the paper used has a stretchability of 20% or more (in this case, 50% or more) in at least some regions due to creping, in contrast to manufacturing by fiber casting.

Explanation of Reference Numerals

[0024] 1. Device for manufacturing molded products from multilayer paper. 2-roller configuration 3 paper layers 4 exit 5 Positive mold 5a Pressing surface of positive mold 6 Negative molds 6a Pressing surface of negative mold 7 Pressing Tools 8. Molded products (also connected) 9 cutting edge 10 Molded products (separated) 11 Molded products 12 First flat region 13. Second flat region

Claims

1. A method for manufacturing molded products from multilayer paper, i) A step of feeding a plurality of paper layers arranged vertically between a positive mold and a complementary negative mold of a pressing tool having a pressing surface, wherein each of the plurality of paper layers has a plurality of fiber ends on the surface of each of the plurality of paper layers, ii) A step of aligning the fiber ends, which are perpendicular to the top or bottom side of the paper layer, by aspirating or supplying a gas or gas mixture, wherein the flow direction of the gas or gas mixture corresponds to the desired alignment. iii) The step of pressing the paper layer with the pressing tool to form molded products corresponding to the positive mold and the complementary negative mold, A method that includes [a certain feature].

2. At least one pressing surface is gas permeable or porous in at least some areas, and suction or supply according to step ii) is performed through at least one pressing surface. The method according to claim 1.

3. The multilayer paper is, in at least a partial area, a crepe-processed cellulose-containing paper that is stretchable by 20% or more. The method according to claim 1.

4. In step ii), aspirating the gas or gas mixture creates a negative pressure with respect to the ambient pressure between the positive mold and the complementary negative mold for at least a short period of time. The method according to claim 1.

5. The paper layer has a solvent or solvent mixture in at least step ii), The method according to claim 1.

6. The solvent or solvent mixture evaporates at a very high rate as a result of aspirating or supplying the gas or gas mixture in step ii). The method according to claim 5.

7. In steps ii) and iii), the content of the solvent or solvent mixture is reduced to less than 5% of the initial content, or, if the solvent is water, the content of the molded product is reduced to a level that is below or equal to the moisture equilibrium between the molded product and ambient air at 20°C, 50% relative humidity, and a periodic air pressure of 1000 hPa. The method according to claim 5.

8. During feeding in step i), at least two of the paper layers are separated from each other. The method according to claim 5.

9. During the feeding of the paper layers in step i), the solvent or solvent mixture is sprayed, evaporated, or both sprayed and evaporated between the paper layers which are spaced apart from each other. The method according to claim 8.

10. The pressure during pressing in step iii) is at least 100 kg / cm². The method according to claim 1.

11. In step iii), the temperature of the pressing tool is between 100°C and 350°C. The method according to claim 1.

12. The composition of the multilayer paper does not contain elastomer additives, and the molded product is fully compostable. The method according to claim 1.

13. A device (1) for manufacturing molded products (8, 10) from multilayer paper, comprising a roller configuration (2) for feeding multilayer paper to a pressing tool (7) having a positive mold (5) and a complementary negative mold (6) each exhibiting pressing surfaces (5a, 6a), The pressing tool (7) is heatable from 100°C to 350°C, at least one of the pressing surfaces (5a, 6a) is gas permeable or porous in at least some areas, and is connected via a hose to a compressor or vacuum pump for aspirating or supplying gas or a gas mixture through the pressing surfaces (5a, 6a), and the pressing surfaces (5a, 6a) are for aligning fiber ends that are perpendicular to the top or bottom side of the paper layer by aspirating or supplying gas or a gas mixture, and the flow direction of the gas or gas mixture corresponds to the desired alignment. Device (1).

14. An outlet (4) for a solvent or solvent mixture, designed to atomize or evaporate the solvent or solvent mixture, is configured to be located upstream of the pressing tool (7), and a transfer device for individual paper layers (3) is configured such that the outlet (4) can be positioned between the individual paper layers (3). The device (1) according to claim 13.

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