Method for press molding a fiber product, a press molding device for press molding a fiber product and a fiber product

Abstract

The invention relates to a method and device for press molding a 3D-formed fiber product. A substantially flat blank of fiber material is positioned between a mold cavity and a mold core provided with at least one protrusion member. The protrusion member pushes the blank into the cavity and crumples it, and is then at least partially retracted into the mold core when a predetermined pressure is reached. The mold core and cavity are subsequently pressed together to form the product. The retractable protrusion members improve utilization of the fiber blank and enable controlled distribution of material. As a result, the molded fiber product exhibits varying densities in different regions, with a difference of at least 0.2 g / cm³ between the lowest and highest density. In preferred embodiments, some regions achieve a density of at least 1.2 g / cm³, providing improved strength and stiffness while maintaining efficient material use.

Description

[0001] METHOD FOR PRESS MOLDING A FIBER PRODUCT , A PRESS MOLDING

[0002] DEVICE FOR PRESS MOLDING A FIBER PRODUCT AND A FIBER

[0003] PRODUCT

[0004] TECHNICAL FIELD

[0005] The present invention relates to a method for press molding a 3D- formed fiber product using a press molding device .

[0006] The invention further relates to press molding device for producing a 3D- formed fiber product from a substantially flat blank made of a fiber material .

[0007] The invention also relates to a press molded 3D- formed fiber product .

[0008] TECHNICAL BACKGROUND

[0009] Press molding of dry fiber material made of cellulose , often referred to as dry forming, is a technique used to shape lightweight products from cellulose-based fibers without the use of water or slurry . This method is particularly useful for producing recyclable and sustainable products , such as packaging materials or structural components , where moisture is minimi zed during the process .

[0010] The starting material is dry cellulose fibers sourced from wood pulp, recycled paper, or other plant-based materials .

[0011] These fibers are processed in a dry state (without adding water or forming a slurry) and may be pre-mixed with binders ( e . g . , starches , resins , or synthetic fibers ) to enhance bonding, strength, or moldability during pressing .

[0012] The dry fibers are often formed into sheets , felt , or mats . The sheet made of dry fibers is cut into a blank prior to press molding .

[0013] The fiber-based blank fiber is placed in the mold cavity . Once the mold is filled with dry fibers , the mold core moves into the mold cavity, compressing the cellulose fibers under high pressure . Pressure plays a key role in compacting the fibers and giving them the desired shape . The level of pressure is carefully controlled to avoid crushing the fibers while ensuring suf ficient bonding .

[0014] The applied pressure compacts the fibers , aligning them and increasing their density, which is crucial for strength and dimensional stability of the final product .

[0015] A problem with the established dry forming process is that excess fiber material is generated after press molding, necessitating disposal or recycling, both of which are costly .

[0016] Another problem with established press molding methods is that it results in end products with limited material properties .

[0017] OBJECTIVE OF THE INVENTION

[0018] A primary obj ective of the invention is to optimi ze the utili zation of fiber material , thereby minimi zing waste during the press molding of a fiber product . Another obj ective is to press-mold a fiber product from a fiber material , such that the produced fiber product has di f ferent material properties in di f ferent parts of the product .

[0019] SUMMARY OF THE INVENTION

[0020] The inventive method comprising the following steps :

[0021] - providing a substantially flat blank made of a fiber material ,

[0022] - positioning the blank between the mold cavity and the mold core ,

[0023] - pushing the blank into the mold cavity using at least one protrusion member, said protrusion member extending from the mold core and moving in unison with it , so that the blank is crumpled into the cavity by the protrusion member,

[0024] - at least partially retracting the protrusion member into the mold core when a predetermined pressure on the protrusion member is reached, and

[0025] - pressing the mold core and mold cavity against each other with a predetermined force , wherein the crumpled blank is pressed between the core and cavity, whereby the 3D- formed fiber product is produced .

[0026] A press molding device is provided, comprising a mold core with at least one protrusion member, which extends out from the mold core and is configured to push and / or crumple the blank into the mold cavity, wherein the protrusion member is arranged to at least partially retract into the mold core when a predetermined pressure on the protrusion member is reached . The inventive 3D- formed fiber product is characteri zed in that the fiber product has been press-molded from a blank made of a fiber material , the fiber product having varying densities in di f ferent parts of the product , with the di f ference between the lowest density and the highest density being at least 0 . 2 g / cm3, and wherein the product has a dry solids content of between 90 wt% and 100 wt% , preferably between 95 wt% and 100 wt% , of plant-based and / or cellulose-based material . In some embodiments , at least one region of the product has a local density of at least 1 . 2 g / cm3.

[0027] The inventive protrusion members allow for the optimi zation of fiber material utili zation, thereby minimi zing waste during the press molding process of a fiber product .

[0028] Moreover, the inventive protrusion members enable the press molding of a fiber product from fiber material in such a way that the resulting product exhibits di f ferent material properties in various parts of the product .

[0029] DETAILED DESCRIPTION OF THE INVENTION

[0030] The invention will now be described in greater detail with reference to Figures 1-4 .

[0031] Figure 1 illustrates the principal functions of a press molding device in cross-section, highlighting the protrusion members and a blank .

[0032] Figures 2a-2d disclose an embodiment of the inventive press molding steps . Figure 3 discloses a perspective view of the press molding device.

[0033] Figure 4 discloses a perspective view of the mold core with protrusion members.

[0034] The innovative method involves press molding a blank 4, made of a fiber material, to create a 3D-formed fiber product using a press molding device 1.

[0035] The 3D-formed product can be cutlery items such as forks, knives, or spoons. It may also include lids, such as screw caps for jars or bottles, as well as lids for disposable cups, such as coffee lids. Additionally, the product can encompass various types of trays. A skilled person will recognize that other products are also possible within the scope of the invention.

[0036] The fiber material for press molding in the device 1 has a dry solids content of 90-100 wt%, preferably 95-100 wt%, of plant-based and / or cellulose-based material.

[0037] In some embodiments, the fiber material may also contain strength agents, selected from the group consisting of alkyl ketene dimer (AKD) , rosin, alkenyl succinic anhydride (ASA) , starches, polyvinyl alcohol (PVA) , carboxymethyl cellulose (CMC) , polyacrylamides (PAM) , guar gum, urea-formaldehyde resins, melamine-formaldehyde resins, polyamide-epichlorohydrin (PAE) resins, latex ( styrene-butadiene ) , polyvinyl acetate (PVA) , calcium carbonate, silanes, ethylene vinyl acetate (EVA) , polyurethane adhesives, phthalates, glycerol, polyethylene glycol (PEG) , isocyanates, melamine, formaldehyde resins, polymer latexes and bicomponent fiber, or a combination thereof. The skilled person understands that the strength agents composition are not limited to those listed here.

[0038] In some embodiments, the fiber material also contain strength agents selected from the group consisting of alkyl ketene dimer (AKD) , rosin, alkenyl succinic anhydride (ASA) , starches, polyvinyl alcohol (PVA) , carboxymethyl cellulose (CMC) , polyacrylamides (PAM) , guar gum, urea-formaldehyde resins, melamine-formaldehyde resins, polyamide-epichlorohydrin (PAE) resins, latex ( styrene-butadiene ) , polyvinyl acetate (PVA) , calcium carbonate, silanes, ethylene vinyl acetate (EVA) , polyurethane adhesives, phthalates, glycerol, polyethylene glycol (PEG) , isocyanates, melamine, formaldehyde resins, polymer latexes, bicomponent fiber, or a combination thereof. It is understood by those skilled in the art that the composition of strength agents is not limited to those listed here.

[0039] In some embodiments, the fiber material contains hydrophobization agents selected from the group consisting of silanes, siloxanes, fluoropolymers, wax emulsions, stearates, paraffins, alkyl ketene dimers (AKD) , alkenyl succinic anhydrides (ASA) , polymer latexes, resins, or combinations thereof. It is understood by those skilled in the art that the composition of hydrophobization agents is not limited to those listed here. The strength and hydrophobi zation agents mentioned above may be incorporated into the fiber material , sprayed onto the material before press molding, and / or applied to the final 3D- formed product after the press molding process .

[0040] Optionally, the moisture content in the fiber material is between 3 wt% and 50 wt% , preferably between 4 wt% and 20 wt% . Excessively low moisture content can result in weak bonding, while excessively high moisture content may lead to steam explosions caused by hydrostatic pressure buildup .

[0041] The fiber material for molding is preferably in sheet form, typically stored on a roll .

[0042] The sheet is cut into a substantially flat blank 4 with a predetermined shape , suitable for press molding and forming the final product . The preferred cutting method is die-cutting, ideally using a punching device 6 or a similar kni fe-like tool that doesn ' t shear the sheet material . The cutting step of the sheet into blanks 4 occurs either before or simultaneously with the insertion of the blank 4 into the mold cavity 2 ( see below) .

[0043] The blank 4 is cut to , or near, a simple geometric shape ( triangle , square , or higher-degree polygon) or a shape that allows perfect or near-perfect nesting, such as sel f-similar or fractal-like shapes , including but not limited to the Sierpinski triangle and Koch snowflake . A skilled person understands that various blank shapes are possible depending on the application . Preferably, the cutting is performed between two adj acent blanks , with a shared cutting line , optimi zing the use of sheet material .

[0044] While the figures disclose only a single press molding device , a skilled person recogni zes that multiple press molding devices can be arranged in a line along the width of the sheet .

[0045] Optionally, the blank is delaminated before being pushed into the mold cavity . The delamination creates multiple creases on the blank, facilitating its subsequent forming ( see below) .

[0046] The delamination step may be performed simultaneously with the cutting step .

[0047] The delamination may be performed using the same tool as the cutting .

[0048] The press molding device 1 comprises two primary components : a mold cavity 2 ( female part ) and a mold core 3 (male part ) . These two components work together to shape the blank 4 into a desired form under pressure and optionally heat .

[0049] The mold cavity 2 has a hollow shape that defines the outer contour of the final product . It serves as the receiver for the blank 4 and determines the external geometry of the final product .

[0050] The cavity 2 is precisely machined or shaped to match the external contours and surface details of the part being molded. For example, if molding a tray, the cavity would form the outer walls and base.

[0051] The mold cavity 2 further comprises conventional ejection mechanisms for removing the finished product without causing damage to the product and / or the molding process. Two common methods used for ejecting molded fiber products include ejection pins 8 and compressed gas channels 9.

[0052] The ejection pins 8 are mechanical devices integrated into the mold to push the finished product out of the cavity after molding. Strategically placed to avoid affecting the product's appearance or structure, the pins extend outward once the mold opens, dislodging the fiber product. They are typically spring-loaded or hydraulically activated, with the number and placement determined by the product's shape and complexity to ensure even force and prevent damage.

[0053] Compressed gas ejection channels 9 use air as a noncontact method to gently remove fiber products from the mold, ideal for delicate or complex parts where mechanical ejection could cause damage. Channels are placed in non-visible areas, and once the product has cooled, compressed gas is introduced to create a cushion that lifts the product out. In some designs, gas channels work alongside ejection pins to enhance the process, with the gas pressure carefully controlled to prevent damage while overcoming friction or adhesion.

[0054] The invention may use either ejection pins 8 and / or compressed gas ejection channels 9. In many advanced mold designs , a combination of ej ection pins and compressed gas channels is used to ensure the safest and most ef fective product removal . Ej ection pins provide targeted mechanical force , while compressed gas ensures uni form li fting across more delicate or intricate areas .

[0055] Optionally, the mold cavity comprises venting channels (not shown in figure ) to allow release of air and gases during the compression .

[0056] The mold core is the complementary part of the mold, which fits into the cavity and determines the inner and upper contour of the product . It compresses the fiber material against the cavity wall during the forming process .

[0057] In accordance with the present invention, the mold core is equipped with at least one protrusion member 5 that extends outward from the core 3 . The protrusion member 5 moves in unison with the mold core , meaning it moves simultaneously whenever the mold core moves . Moreover, the protrusion member 5 is movable relative to the mold core 3 , allowing the member to retract into the core when necessary . The position of the protrusion member relative to the mold core is controlled by at least one spring 7 mechanism . Figure 1 shows an embodiment where each protrusion member 5 is controlled by a respective spring 7 . Figures 2a-2d show an embodiment where several protrusion members 5 are controlled by two springs 7 . When a predetermined pressure is applied to the protrusion member, it is either at least partially or fully retracted into the mold core . Figure 1 illustrates a first embodiment , featuring several protrusion members in the form of straight fingers . The protrusion members can take various forms , such as blades as shown in figure 4 , depending on the application . In use , the multiple protrusion members may contact the blank either sequentially or simultaneously . Preferably, the protrusion member pushes all parts of the blank below the rim of the opening of the mold cavity . Additionally, the protrusion members extending from the mold core may vary in length, as shown in the figures . At least one protrusion member may feature a needle-shaped tip, allowing it to pierce and hold the blank as it is pushed into the mold cavity .

[0058] The clearance between the mold core and the mold cavity, in cross-section, is less than 200 pm, preferably less than 50 pm, to ensure optimal utili zation of all blank material when pushed down .

[0059] In an optional embodiment , the mold core 3 and / or mold cavity 2 is heated to a temperature between 100 ° C and 250 ° C, preferably between 150 ° C and 220 ° C, to facilitate the molding process .

[0060] The mold core 3 and mold cavity 2 are pressed together with a predetermined force , ensuring the blank fully covers the bottom of the mold cavity 2 . This action compresses the crumpled blank 4 between the core and cavity, resulting in the formation of the 3D-shaped product . The bottom and sides of the mold cavity, along with the bottom edge of the mold core and protrusion members , collectively define the 3D geometry of the pressed fiber product . For clarity, the blank has a first area (Al) , the opening of the mold cavity has a second area (A2) , the protrusion member has a third area (A3) for pressing the blank, and the mold core has a fourth area (A4) for pressing the blank, where Al > A2 > (A3 + A4 ) .

[0061] The maximum pressure during the pressing step ranges from 50 bar to 10,000 bar, preferably between 200 bar and 2,000 bar. During this cycle, the protrusion member and mold core function as a single unit when exposed to maximum pressure. The distance between the mold core and mold cavity is at least 30 pm when the blank is positioned between them at maximum pressure. The holding time during the pressing / molding operation is typically set between 0.1 and 5 seconds, preferably between 0.3 and 2 seconds. When heat is applied, a holding time that is too short may prevent the fibers from sintering properly, while a holding time that is too long could lead to steam explosions or carbonization of the product.

[0062] After the pressing / molding is complete, the mold core is retracted to its starting position above the mold cavity opening, and the pressed fiber product is ejected from the mold cavity using any of the previously described ejection mechanisms, such as ejector pins 8 and / or compressed air through channels 9.

[0063] Optionally, the 3D-formed product is cured after being ejected from the mold cavity. A preferred curing process involves heating the product at a temperature of 70-250°C for a duration of 5-120 minutes. For example, if the blank has been treated with a hydrophobic agent such as AKD, the curing temperature is approximately 70 °C for at least 30 minutes.

[0064] Optionally, the 3D-formed product can be painted or printed. Possible painting methods include spraying, powder coating, and dip coating. A skilled person will recognize that other painting and printing methods are also feasible within the scope of the invention.

[0065] A major benefit of the invention is that the protrusion members enable the crumpled blank to be positioned within the mold cavity in such a way that the pressed fiber product can achieve varying densities in different areas. The density of the pressed fiber product ranges from 0.5 to 1.4 g / cm3, typically between 0.7 and 1.25 g / cm3.

[0066] The inventive 3D-formed fiber product is distinguished by having varying densities in different parts, with the difference between the lowest and highest density being at least 0.2 g / cm3. Furthermore, the product has a dry solids content of between 90 wt% and 100 wt%, preferably between 95 wt% and 100 wt%, composed of plant-based and / or cellulose-based materials. In some embodiments, at least one local region of the product has a density of at least 1.2 g / cm3. In other embodiments, the local density may range from 0.5 to 1.4 g / cm3, typically between 0.7 and 1.25 g / cm3. Thus, the invention encompasses both products with lower-density regions and products where certain regions are particularly dense (hl.2 g / cm3) .

[0067] The ability to achieve different local densities allows the product to also have varying local stiffness moduli in different areas. In some embodiments, the stiffness modulus exceeds 30 GPa in speci fic regions of the product .

[0068] Preferably, the final product has a hydrophobicity in the range of 5-30 g / m2, more preferably between 5- 10 g / m2, as measured according to ISO 535 .

[0069] The high pressure and lack of shrinkage result in a smooth surface for the product . Preferably, the 3D- formed fiber product has a surface roughness of less than 5 pm, as measured according to ISO 8791-4 .

[0070] Example of an embodiment for forming a tray Figures 2a-2d illustrate a preferred embodiment of the inventive method for forming a tray .

[0071] In Figure 2a, the blank 4 is positioned in the press molding device between the mold core 3 with protrusion members 5 and the mold cavity 2 . The protrusion members are in their outward position relative to the core . The outer edges of the protrusion members 5 are positioned above the blank 4 .

[0072] In Figure 2b, the blank 4 has been pushed and / or crumpled into the cavity by the protrusion members 5 , which move in unison with the mold core 3 . The protrusion members are in contact with the blank 4 and remain in their outward position .

[0073] In Figure 2c, the protrusion members 5 have been retracted into the mold core 3 , and the bottom of the tray is pressed by both the mold core and the protrusion members 5 . In Figure 2d, the mold core presses the outer edge of the tray. In this position, the mold core and the protrusion members function as a single unit during the pressing process .

[0074] Some benefits of the invention

[0075] A major benefit of the invention is that the protrusion members enable the crumpled blank to be positioned within the mold cavity such that the pressed fiber product can achieve different local densities. This may involve relatively low-density regions for material savings, or relatively high-density regions (hl.2 g / cm3) for strength and stiffness, depending on the application.

[0076] Efficient Material Utilization: The design of the protrusion members optimizes the use of fiber material, reducing waste during the molding process.

[0077] Controlled Forming: The protrusion members enable precise control over the pushing and crumpling of the blank, ensuring uniformity, and reducing the likelihood of defects .

[0078] Variable Material Properties: The ability to achieve different local densities allows for variations in material properties, enabling the production of customized products tailored to specific applications.

[0079] In the preceding description, the invention has been presented through specific embodiments. However, a skilled person will recognize that other embodiments and variations are possible within the scope of the following claims .

Claims

C L A I M S1. Method for press molding a 3D-formed fiber product using a press molding device (1) , the device comprising a mold cavity (2) (female part) and a mold core (3) (male part) , the method comprising the following steps:- providing a sheet (4) made of a fiber material, wherein the dry solids content of the fiber material is between 90 wt% and 100 wt%, preferably between 95 wt% and 100 wt%, of plant-based and / or cellulose-based material,- positioning the sheet between the mold cavity and the mold core,- die cutting the sheet of fiber material with a punching device (6) to form a blank (4) , either prior to or simultaneously with pushing the blank into the mold cavity,- pushing the blank into the mold cavity using at least one protrusion member (5) , said protrusion member extending from the mold core (3) and moving in unison with it, so that the blank is crumpled into the cavity by the protrusion member,- at least partially retracting the protrusion member into the mold core when a predetermined pressure on the protrusion member is reached, and- pressing the mold core and mold cavity against each other with a predetermined force, wherein the crumpled blank is pressed between the core and cavity, thereby producing the 3D-formed product.

2. Method according to claim 1, wherein several protrusion members (5) are used, and the protrusion members contact the blank (4) either sequentially or simultaneously .

3. Method according to any one of claims 1-2, wherein the cutting is performed between two adjacent blanks (4) , such that the cutting line is common to both blanks.

4. Method according to any one of the preceding claims, further comprising the step of delaminating the blank prior to pushing it into the mold cavity, wherein the delamination creates a plurality of creases on the blank.

5. Method according to any one of the preceding claims, wherein the delaminating is performed simultaneously with the cutting.

6. Method according to any one of claims 4-5, wherein the delaminating is performed using the same tool as the cutting .

7. Method according to any one of the preceding claims, wherein the blank has a first area (Al) , the opening of the mold cavity has a second area (A2) , the protrusion member has a third area (A3) , and the mold core has a fourth area (A4) , where Al > A2 > (A3 + A4 ) .

8. Method according to any one of the preceding claims, wherein the protrusion members (5) extending from the mold core (3) have different lengths.

9. Method according to any one of the preceding claims, wherein the protrusion member is partially and / or fully retracted .

10. Method according to any one of the preceding claims, wherein at least one protrusion member has a needle- shaped tip, enabling the protrusion member to pierce and hold the blank when pushed down.

11. Method according to any one of the preceding claims, wherein the protrusion member pushes all parts of the blank below the rim of the opening of the mold cavity.

12. Method according to any one of the preceding claims, wherein the clearance between the mold core and the mold cavity is less than 200 pm, preferably less than 50 pm.

13. Method according to any one of the preceding claims, wherein the mold core and / or mold cavity is heated to a temperature between 100°C and 250°C, preferably between 150°C and 220°C.

14. Method according to any one of the preceding claims, wherein the moisture content of the fiber material in the blank is between 3 wt% and 50 wt%, preferably between 4 wt% and 20 wt%.

15. Method according to any one of the preceding claims, wherein the maximum pressure during the pressing step is between 50 bar and 10000 bar, preferably between 200 bar and 2000 bar.16 . Method according to any one of the preceding claims , wherein the position of the protrusion member relative to the mold core is controlled by at least one spring mechanism ( 7 ) .17 . Method according to any one of the preceding claims , wherein the protrusion member and the mold core act as a single unit when exposed to the maximum pressure during the pressing cycle .18 . Method according to any one of the preceding claims , wherein the distance between the mold core and the mold cavity is at least 30 pm when they are separated by the blank at maximum pressure .19 . Method according to any one of the preceding claims , wherein the blank covers the entire bottom of the mold cavity when pressed between the mold core and the mold cavity .20 . Method according to any one of the preceding claims , wherein the bottom and sides of the mold cavity, along with the bottom of the mold core and at least one protrusion member, define the 3D geometry of the pressed fiber product .21 . Method according to any one of the preceding claims , wherein the crumpled blank is arranged inside the mold cavity such that the pressed fiber product can have varying densities in di f ferent parts of the product .

22. Method according to the preceding claim, wherein the density of the pressed fiber product varies between 0.5 and 1.4 g / cm3, typically between 0.7 and 1.25 g / cm3.

23. Method according to any one of the preceding claims, further comprising the step of ejecting the produced 3D- formed fiber product from the mold cavity.

24. Method according to the preceding claim, wherein the ejection is accomplished using ejection pins (8) and / or channels (9) that allow compressed gas to eject the fiber product .

25. Method according to any one of the preceding claims, wherein the holding time during the pressing / molding operation is set between 0.1-5 seconds, preferably between 0.3-2 seconds.

26. Method according to any one of the preceding claims, further comprising a step of curing the produced 3D- formed fiber product, wherein the fiber product is cured at a temperature of 70-250°C for a duration of 5-120 minutes .

27. A press molding device (1) for producing a 3D-formed fiber product from a substantially flat blank (4) made of a fiber material, the device comprising:- a mold cavity (2) (female part) ,- a mold core (3) (male part) , which comprises at least one protrusion member (5) , which extends out from the mold core and is configured to push and / or crumple the blank into the mold cavity, wherein the protrusion member is arranged to at least partially retract into the moldcore when a predetermined pressure on the protrusion member is reached, and- a punching device (6) wherein the punching device is arranged to die cut a sheet to form the blank (4) prior to or simultaneously with the blank being pushed and / or crumpled into the mold cavity.

28. A 3D-formed fiber product produced by the method according to any one of claims 1-26, wherein the fiber product has been press-molded from a blank made of a fiber material, wherein the fiber product has varying densities in different parts, with the difference between the lowest and highest density being at least 0.2 g / cm3, and wherein the product has a dry solids content between 90 wt% and 100 wt%, preferably between 95 wt% and 100 wt%, of plant-based and / or cellulose-based material.

29. The 3D-formed fiber product according to claim 28, wherein at least one region of the product has a local density of at least 1.2 g / cm3.

30. The 3D-formed fiber product according to any one of claims 28-29, wherein the final product has a hydrophobicity in the range of 5-30 g / m2, preferably 5-10 g / m2, as measured according to ISO 535.

31. The 3D-formed fiber product according to any one of claims 28-30, wherein the final product has a surface roughness less than 5 pm, as measured according toISO 8791-4.

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