Process for the manufacture of three-dimensional cellulose products

Abstract

A method for producing three-dimensional cellulose products, comprising the following steps: • Providing a web-shaped nonwoven fabric (web material) based on cellulose fibers, • Transporting the web material through successive processing stations, • Pre-cutting the contours of the cellulose products in the web material in a first processing station, • Compression forming of the cellulose products within the pre-cut contours in the web material in a second processing station, and • Die-cutting of the compression-formed cellulose products from the web material in a third processing station.

Description

[0001] The invention relates to a method for producing three-dimensional cellulose products.

[0002] The three-dimensional cellulose product includes, for example, bowls, plates, cups or other containers, spoons, forks, knives or other disposable eating utensils, inserts for outer packaging, holders for writing instruments or other products for technical applications.

[0003] EP 4 043 353 A1 describes a process for manufacturing a cellulose product, comprising the steps of dry forming a cellulose blank in a dry forming unit, arranging the cellulose blank in a forming tool, heating the cellulose blank to a forming temperature in the range of 100 °C to 200 °C, and pressing the cellulose blank in the forming tool with a forming pressure of at least 1 MPa. In the dry forming unit, a cellulose raw material is dissolved into cellulose fibers. From the dissolved cellulose fibers, a web of cellulose fibers (airlaid) is produced by laying air onto an air-permeable, vacuum-assisted conveyor belt, and this web is compacted or calendered. The web-shaped cellulose blank produced in this way is fed intermittently to the forming tool via a feeding unit. In the forming tool, the cellulose product is formed and die-cut from the web.In practical implementation, the process involves applying a tissue to the web-shaped cellulose blank, spraying on AKD as a water barrier, and drying it in an oven for approximately 15 minutes. Because the production of the web-shaped cellulose blank and the cellulose product are carried out inline, the system is complex and the production speed is limited. Applying and drying a water barrier further increases the system complexity and restricts cycle times and throughput. The forming tool is highly complex, prone to wear and tear, and susceptible to malfunctions because it simultaneously forms and die-cuts the product.

[0004] Based on this, the invention aims to provide a less complex, less wear-prone and less prone to malfunctions, as well as a method for producing three-dimensional cellulose products that enables higher cycle rates and throughputs.

[0005] The problem is solved by a method according to claim 1. Advantageous embodiments of the method are specified in the dependent claims and in the description.

[0006] The inventive method for producing three-dimensional cellulose products comprises the following steps: Providing a web-shaped nonwoven fabric (web material) based on cellulose fibers, transporting the web material through successive processing stations, pre-cutting the contours of the cellulose products in the web material in a first processing station, pressing the cellulose products within the pre-cut contours in the web material in a second processing station, and punching out the press-formed cellulose products from the web material in a third processing station.

[0007] In the process according to the invention, the cellulose products are manufactured from a web-shaped nonwoven fabric based on cellulose fibers. The production of the cellulose products is divided into three steps, which are carried out in three successive processing stations through which the web material is transported. In a first step, the contours of the cellulose products are pre-cut in the web material at a first processing station. In a second step, the cellulose products are press-molded within the pre-cut contours in the web material at a second processing station. In a third step, the press-molded cellulose products are die-cut from the web material at a third processing station. By dividing the forming of the cellulose products into three successive steps, the complexity of the tools in the various processing stations can be kept comparatively low.This reduces the effort required for the technical implementation of the process. The relatively simple tools exhibit low wear and are less prone to malfunctions. Because only a portion of the cellulose product forming process is carried out at each of the various processing stations, higher cycle rates and throughputs can be achieved.

[0008] Pre-cutting the contours of the cellulose products in the web material before compression molding reduces the effort required for compression molding and enables particularly deep and precise compression molding of the web material. For example, drinking cups with a depth of 8 cm can be compression molded (deep-drawn). Furthermore, pre-cutting has the advantage that the wall thickness of the cellulose product is nearly uniform across its entire cross-section.

[0009] By dividing the forming of the cellulose products into three steps, the use of web material with a comparatively high density is made possible, which exhibits sufficient integrity for winding and supplying as roll material. Unlike the conventional prior art process, in which the web material is supplied as loose fluff on a conveyor belt, it is not necessary to carry out the production of the web material inline with the forming of the cellulose products. This enables particularly economical production of the web material in a high-performance plant that supplies the feedstock for the forming of cellulose products in multiple plants. Supplying the web material as roll material allows for buffering to compensate for fluctuations in the throughput during the forming of the cellulose products.Separating the production of the raw material from the forming of the cellulose products also simplifies the operation of the equipment for producing the web material and forming the cellulose products. Furthermore, providing a web material with comparatively high density and integrity allows for the use of simple transport systems to move the web material through successive processing stations. For example, the web material can be transported using chain guides that grip the web material at its edges and transport it through the processing stations.

[0010] According to one embodiment of the invention, the web material comprises several superimposed layers of nonwoven fabric. These layers can be made of the same material or of different materials. Superimposing multiple layers of nonwoven fabric facilitates the production of web materials with high homogeneity, as well as web materials with advantageous properties due to the superimposed layers of different materials. High material homogeneity reduces process variations and the associated costs of defects caused by weaknesses in the product resulting from an inhomogeneous distribution of the fibers. Furthermore, superimposing multiple layers of nonwoven fabric facilitates the production of web materials with advantageous properties due to the superimposed layers of different materials.According to another design, the web material has a layer of virgin fibers on one or both sides and a layer of recycled fibers in between. The side with the virgin fiber layer is particularly suitable for contact with food.

[0011] According to another embodiment, the web material has a barrier fabric and / or a barrier film on one or both sides. The barrier fabric and / or barrier film layer can be designed to prevent or reduce the penetration of moisture, especially water or grease. The barrier fabric and / or barrier film layer can also serve as an aroma and / or water vapor barrier. Web material with such a barrier layer is particularly suitable for the production of cellulose products for food packaging.

[0012] Tissue is an absorbent, finely creped material made entirely or predominantly from cellulose fibers, as defined in DIN 6730. Tissue is typically used in multi-ply form for kitchen paper, paper napkins, facial tissues, and toilet paper. For the barrier tissue, either this type of tissue or a tissue-like material can be used. A tissue-like material is defined as one that is produced using a different drying process compared to tissue. DIN 6730 provides further details on tissue-like materials. The barrier tissue is coated with a moisture-repellent material, such as AKD (alkylated ketene dimers). AKD is used, for example, to make papers and containers made of cellulose fibers water-repellent for liquids.

[0013] According to another design, a barrier film made of PHA, cellophane, PLA or PP is used.

[0014] The supplied web material may already be coated with the barrier fabric and / or barrier film on one or both sides. The barrier fabric and / or barrier film may also be applied to the supplied web material subsequently. Furthermore, web material may be supplied that is already coated with a barrier fabric or barrier film on one side and is subsequently coated with a barrier fabric or barrier film on the other side.

[0015] According to another embodiment, the web material is provided with a barrier fabric and / or at least one barrier film on one or both sides during transport to the processing stations. During transport, the barrier fabric and / or barrier film can be heated by a heating unit, which, for example, generates hot air or includes heating coils, and then pressed firmly onto the three-dimensional cellulose products during compression molding.

[0016] In another embodiment, the web material comprises starch, thermoplastic fibers, and / or another additive that contributes to the strengthening of the cellulose products. The additive can be added in powder and / or fiber form before the web-like nonwoven fabric is laid down to achieve optimal homogenization of the additive within the web material. As a result, the cellulose products exhibit uniform strength across their entire cross-section. The additive can be added dry, thus minimizing moisture ingress and enabling shorter pressing times and faster cycle times for forming the cellulose products.

[0017] According to another embodiment, the web material comprises at least one layer consisting essentially of cellulose fibers. According to another embodiment, the web material comprises at least one layer consisting exclusively of cellulose fibers.

[0018] According to another embodiment, the web material is produced by dry-laying one or more layers containing cellulose fibers onto a vacuum conveyor belt, suctioning the at least one layer onto the top of the vacuum conveyor belt, and compacting the at least one layer between at least one roller and the vacuum conveyor belt or another substrate. According to yet another embodiment, the web material is formed from at least one layer containing cellulose fibers and compacted by means of at least one roller in such a way that the web material has sufficient density and integrity to be wound up and supplied as roll material.

[0019] In another version, the web material is supplied as roll material. This allows for buffering to compensate for fluctuations in throughput during the forming of the cellulose products.

[0020] According to another embodiment, the web material is provided with a barrier fabric or barrier film on at least one side and / or the web material is provided with a layer of barrier fabric or barrier film on at least one side during transport to the first processing station. This allows the same raw material to be used for different products, which are provided with or without an additional layer of barrier fabric or barrier film, depending on the requirements.

[0021] In another method, the web material is provided in a dry state. A dry state is defined as a condition in which the moisture content of the web material is in equilibrium with the ambient humidity. Providing the web material in a dry state enables shorter pressing times and faster cycle times.

[0022] According to another embodiment, the web material is moistened in at least one processing station before processing. This moistening increases the degree to which the web material can be deformed during compression molding without tearing.

[0023] According to another design, when pre-cutting the contours of the cellulose products in the first processing station, connecting areas that join the pre-cut contours to the rest of the web material are not severed until the cellulose products are die-cut in the third processing station. This ensures that the cellulose products are transported through the various processing stations along with the web material, thus promoting short cycle times and high throughput, and preventing disruptions caused by detached cellulose products.

[0024] According to another design, only sections of the contours of the cellulose products are pre-cut, so that connecting areas remain between adjacent pre-cut sections of the contours and the rest of the web material, which connect the pre-cut contours with the rest of the web material.

[0025] According to another embodiment, the connecting areas are strip-shaped. After compression forming, these strip-shaped areas connect the cellulose products to the rest of the web material, bridging the gap between the outer edge of the cellulose products and the inner edge of the surrounding web material.

[0026] According to another design, the strip-shaped connecting areas have a zigzag pattern in the web material. This allows for the bridging of particularly large gaps between the press-molded cellulose products and the web material to which they are connected via the strip-shaped areas.

[0027] According to another embodiment, the web material in the area of ​​the contours of the cellulose products is only partially cut perpendicular to its main expansion surface during pre-cutting, so that the pre-cut cellulose products are connected to the rest of the web material via the uncut areas of the cross-section.

[0028] In another embodiment, the web material is lightly pre-pressed into a three-dimensional shape within the pre-cut contours at the second processing station using a (disc) pin. The three-dimensional cellulose product is then pressed between a positive and a negative part of the mold. Pre-pressing the web material facilitates the compression molding of particularly deep cellulose products and ensures a uniform wall thickness across the entire cross-section.

[0029] According to another embodiment, in the second processing station, the web material is pressed within the pre-cut contours between a positive and a negative part of the forming tool, with the negative part (negative mold) being subjected to a vacuum. Applying a vacuum to the negative mold of the forming tool has the following advantages in particular: applying the vacuum shortly before the mold closes causes the material to be "drawn" into the negative cavity. Applying the vacuum during the pressing process accelerates the removal of moisture from the web material.

[0030] According to another embodiment, after compression molding, the cellulose products are ejected from the positive and / or negative part of the mold by means of a (disc) pin. The (disc) pin is used to release the cellulose products from the mold, thus achieving simple and reliable separation of the cellulose products from the mold. This can be the same (disc) pin used for pre-pressing.

[0031] According to another embodiment, the web material is press-molded at a temperature of 80 °C to 180 °C. This allows the web material to be deformed to a particularly high degree, resulting in exceptionally high strength of the cellulose product. Furthermore, press-molding at these temperatures is advantageous for forming a barrier layer of barrier tissue and / or barrier film. Preferably, the web material is press-molded at a temperature of 140 °C to 150 °C.

[0032] According to another method, when the cellulose products are die-cut from the web material, the connecting areas are separated from the contours of the cellulose products. This separates the cellulose products from the rest of the web material during the die-cutting process.

[0033] According to another embodiment, the third processing station has a centering device for high-precision punching with a punching knife that has an internal shape which is a positive image of the external three-dimensional shape of the cellulose product.

[0034] In another embodiment, the cellulose products are heated after die-cutting using a curing device. This improves the barrier properties of the three-dimensional cellulose products. In another embodiment, the cellulose products are heated between two heated plates. In yet another embodiment, the cellulose products are heated using an infrared heater.

[0035] According to another embodiment, a first press exerts a pressure of approximately 1 to 50 tons on a table surface of 800 × 800 mm² during pre-cutting. According to another embodiment, the first press exerts a pressure of 50 tons.

[0036] According to another embodiment, a second press exerts a pressure of approximately 1 to 500 tons on a table surface of 800 × 800 mm² during the pressing process. According to yet another embodiment, the second press exerts a pressure of 500 tons.

[0037] According to another embodiment, a third press exerts a pressure of 1 to 50 t on a table surface of 800 × 800 mm² during the punching process. According to yet another embodiment, the third press exerts a pressure of 50 t.

[0038] In another design, the web material is transported through the processing stations by means of a chain or clamp / clip guide. This enables the transport of the web material with particularly low plant engineering requirements.

[0039] According to another embodiment, the die-cut grid remaining after the cellulose products have been punched out of the web material is recycled, preferably by being fed back into the production of the web material.

[0040] The invention is explained in more detail below with reference to the accompanying drawings of an exemplary embodiment. The drawings show: Fig. 1 a plant for producing a web material in a rough schematic view; Fig. 2a, b the web material between lateral chain guides with pre-cut, press-formed and punched sections and a press tool in a second processing station in the closed state (Fig. 2a ) and in the open state ( Fig. 2b ); Fig. 3 the cellulose products and the die-cutting grid of the web material behind the third processing station in a rough schematic view.

[0041] According to Fig. 1 A plant for the production of a web-shaped nonwoven fabric (nonwoven fabric plant 1) comprises two hammer mills 2, 3 in which raw material is crushed.

[0042] Furthermore, the nonwoven fabric plant 1 includes a horizontally oriented vacuum conveyor belt 4. This belt comprises an air-permeable vacuum belt 5 (screen belt) which is guided over rollers 6, 7 and has an upper run 8 and a lower run 9. One of the rollers 6, 7 is driven by a drive motor.

[0043] In the transport direction of the upper run of the vacuum conveyor belt 4, which is in Fig. 1 Running from left to right, four forming stations 10, 11, 12, 13 are arranged in succession. Each of these has a forming head 14, 15, 16, 17 above the upper run 8. Below the upper run 7, forming stations 10, 11, 12, 13 have extraction devices 18, 19, 20, 21, which are connected to a fan.

[0044] The hammer mills are connected to the forming heads 14, 15, 16, 17 via pipelines 22, 23. The pipelines 22, 23 have pneumatic transport systems for transporting the crushed raw materials to the forming heads 14, 15, 16, 17.

[0045] Heated rollers 24, 25 of a compactor 26 are arranged in the transport direction of the vacuum conveyor belt 4 behind the forming stations 10, 11, 12, 13.

[0046] A layer of barrier fabric 26.2 is fed to the upper run 8 of the vacuum conveyor belt 4 from a rotatably mounted bearing roller 26.1. The bearing roller 26.1 is in Fig. 1 located to the left of the vacuum conveyor belt 6.

[0047] The hammer mills 2, 3 are supplied with pulp and, if necessary, starch (in powder form) and, if necessary, one or more additives as raw material.

[0048] In the hammer mills 2 and 3, the supplied materials are crushed and mixed. The materials are then conveyed through the pipelines 22 and 23 to the forming heads 14, 15, 16, and 17.

[0049] Four layers 27, 28, 29, 30 of the shredded raw material are successively applied to the barrier fabric 26.2 on the upper run 8 via the forming heads 14, 15, 16, 17 and drawn in by the vacuum applied to the underside of the upper run 8. Downstream of the forming heads 14, 15, 16, 17, the material deposited on the upper run 8 is compacted by the rollers 24, 25 of the compactor 26. Downstream of the vacuum conveyor belt 4, the compacted web-like nonwoven fabric 31 (web material), which comprises the barrier fabric 26.2 and the layers 27, 28, 29, 30 of shredded raw material, is wound into a roll.

[0050] Fig. 2 Figure 1 shows a section of the web material 31 unwound from the roll, which is transported by means of two laterally acting chain guides 32, 33. The transport direction is in Fig. 2 From right to left. The first section 31.1 of the railway material 31 in the direction of transport has not yet been processed.

[0051] The second section 31.2, preceding the first in the transport direction, is located in a first processing station 34, where contours 35 of cellulose products and contours 36 of connection areas, which connect the contours 35 to the remaining web material 31, are pre-cut in the web material 31 by means of a pre-cutting device. The contours 35 of the cellulose products are circular. The contours 36 of the connection areas are strip-shaped and have a zigzag pattern. The first processing station 34 has a pre-cutting device in the form of a first press with cutting blades. The pre-cutting device is not shown for clarity.

[0052] In the third section 31.3 of the web material 31, which precedes the transport direction, the cellulose products 37 are press-formed in a second processing station 38. The second processing station 38 has a forming tool 39 in the form of a second press with a positive and a negative tool part 40, 41, which correspond to the inner and outer contours of the cellulose products 37. Fig. 2 The cellulose products 37 are shells. Preferably, the barrier fabric 26.2 covers the inner surfaces of the shells.

[0053] During compression molding, the diameter of the circular contours 35 at the upper edges of the cellulose products decreases, creating spaces 42 between these contours 35 and the adjacent areas of the web material 31. These spaces form the connection areas 43. Fig. 2b The upper edges of the press-molded cellulose products 37 are connected to the inner edges of the remaining web material 31 via the connecting areas 43. The strip-shaped connecting areas 43 are slightly pulled apart due to their zigzag shape. The connecting areas 43 hold the press-molded cellulose products 37 in place within the web material 31 during further transport.

[0054] The forming tool 39 has a (disc) pin for pre-pressing the three-dimensional shape of the cellulose products 37 into the web material 31 and for pressing the cellulose products 37 out of the forming tool 39 after compression molding. These are not shown for clarity.

[0055] The fourth section 31.4 of the web material 31, which precedes it in the transport direction, is located in a third processing station 44, in which a device for punching out the press-molded cellulose products 35 from the web material 31 is provided. The punching device is a third press that has corresponding cutting dies. The cutting die of the punching device preferably has an internal positive image of the three-dimensional shape of the cellulose product 35 so that it can be punched out with an accuracy of up to 1 / 10 mm. The punching device is not shown for the sake of clarity.

[0056] In Fig. 2a The press-molded cellulose products 37 are still connected to the rest of the web material 31 via the connection areas 49. In Fig. 2b The connecting areas 43 are cut through and the cellulose products 37 are separated from the rest of the web material 31, which is referred to as the die-cut grid 45.

[0057] The punch grid 45 is recycled by feeding it, together with the raw material, to the hammer mills 2, 3.

[0058] The stacked cellulose products 37 and the recycling of the punched grid 45 are in Fig. 3 shown.

[0059] Pre-cutting, pressing, and die-cutting the cellulose products 37 result in short cycle times, high throughput, and simple tools with long service life and low downtime. Pre-cutting and pre-pressing allow for the production of particularly deep cellulose products 37. Reference number list

[0060] 1 Nonwoven fabric plant 2, 3 Hammer mill 4 Vacuum conveyor belt 5 Air-permeable vacuum belt 6, 7 Rollers 8 Upper run 9 Lower run 10-13 Forming station 14-17 Forming head 18-21 Extraction device 22, 23 Piping 24, 25 Heated roller 26 Compactor 26.1 Bearing roller 26.2 Barrier fabric 27-30 Position of the shredded raw material 31 Web material 31.1 First section 31.2 Second section 31.3 Third section 31.4 Fourth section 32, 33 Chain guide 34 First processing station 35 Contour of a cellulose product 36 Contour of a joining area 37 Cellulose product 38 Second processing station 39 Forming tool 40 Positive tool part 41 Negative tool part 42 Clearance 43 Connection area 44 Third processing station 45 Punch grid

Claims

1. A method for producing three-dimensional cellulose products, comprising the following steps: • Providing a web-shaped nonwoven fabric (web material) based on cellulose fibers, • Transporting the web material through successive processing stations, • Pre-cutting the contours of the cellulose products in the web material in a first processing station, • Compression forming of the cellulose products within the pre-cut contours in the web material in a second processing station, and • Die-cutting of the compression-formed cellulose products from the web material in a third processing station.

2. The method according to claim 1, wherein the web material comprises several superimposed layers of nonwoven fabric and / or wherein the web material has a barrier fabric and / or a barrier film on one side or on both sides.

3. Method according to one of claims 1 or 2, wherein the web material comprises starch, thermoplastic fibers and / or another additive which contributes to strengthening the cellulose products.

4. Method according to any one of claims 1 to 3, wherein the web material comprises at least one layer consisting substantially or exclusively of cellulose fibers.

5. Method according to any one of claims 1 to 4, wherein the web material is produced by dry depositing one or more layers containing cellulose fibers onto a vacuum conveyor belt, suctioning the at least one layer onto the top of the vacuum conveyor belt and compacting the at least one layer between at least one roller and the vacuum conveyor belt or another substrate.

6. Method according to any one of claims 1 to 5, wherein the web material is provided as roll material.

7. Method according to any one of claims 2 to 6, wherein a web material is provided with a layer of a barrier fabric or a barrier film on at least one side and / or wherein the web material is provided with a layer of a barrier fabric or a barrier film on at least one side during transport to the first processing station.

8. Method according to any one of claims 1 to 7, wherein the web material is provided in a dry state and / or wherein the web material is moistened before processing in at least one processing station.

9. Method according to any one of claims 1 to 8, wherein, during pre-cutting of the contours of the cellulose products in the first processing station, connecting areas are not cut through which connect the pre-cut contours with the remaining web material until the cellulose products are punched out in the third processing station.

10. Method according to any one of claims 1 to 9, comprising one or more of the following features: • in the first processing station, only sections of the contours of the cellulose products are pre-cut, such that connection areas exist between adjacent pre-cut sections of the contours of the cellulose products and the remaining web material, • the connection areas are strip-shaped, • the strip-shaped connection areas have a zigzag pattern in the web material, • the web material is only partially cut perpendicular to its main expansion surface in the area of ​​the contours of the cellulose products during pre-cutting.

11. Method according to any one of claims 1 to 10, wherein in the second processing station the web material is lightly pre-pressed into a three-dimensional shape within the pre-cut contours by means of a (disc) pin and subsequently the three-dimensional cellulose products are pressed between a positive and a negative tool part of the forming tool and / or wherein the cellulose products are pushed out of the positive and / or the negative tool part of the forming tool after compression forming by means of a (disc) pin.

12. Method according to any one of claims 1 to 11, wherein the web material is pressed in the second processing station within the pre-cut contours between a positive and a negative tool part of the forming tool, wherein the negative tool part is subjected to a vacuum.

13. Method according to any one of claims 1 to 12, wherein the third processing station comprises a device for punching with a punching blade which has an internal shape that is a positive image of the external three-dimensional shape of the cellulose product.

14. A method according to any one of claims 1 to 13, comprising one or more of the following features: • the web material is press-formed at a temperature of 80° to 180°C, • the barrier layers of the cellulose products are heat-treated after die-cutting in a curing device by means of a heating device, • a first press exerts a pressure of about 1 to 50 t during pre-cutting, based on a table surface of 800 × 800 mm 2 • a second press exerts a pressure of approximately 1 to 500 t during press forming, based on a table surface of 800 × 800 mm 2 • a third press exerts a pressure of approximately 1 to 50 t during the die-cutting process, based on a table surface of 800 × 800 m2 out of.

15. Method according to any one of claims 1 to 14, comprising one or the following features: • when punching out the cellulose products from the web material, the connecting areas are separated from the contours of the cellulose products, • the web material is transported through the processing stations by means of a chain or clamp / clip guide, • after punching out the cellulose products from the web material, the remaining die-cut grid is recycled, preferably by being fed back into the production of the web material.

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