Tools and methods for producing 3D molded pulp products

Abstract

This document relates to a tool for producing a 3D-shaped product from a pulp slurry, comprising a pair of dies having respective product faces facing each other and configured to press a pulp layer therebetween, the product faces providing a 3D shape for forming the 3D-shaped product, the product faces presenting respective outer product end faces and defining the outermost limits of the forming area of ​​the die. At least one of the product faces presents, when viewed inward from the product end face toward the center of gravity of the product face, an outer zone (Z1) that is virtually free of porosity and an inner zone (Z4) having a porosity of 40 to 75%, and a first intermediate zone (Z2) disposed between the outer zone (Z1) and the inner zone (Z4) that has a porosity greater than that of the outer zone (Z1) but less than that of the inner zone (Z4).

Description

[Technical Field]

[0001] The present disclosure relates to tools and methods for producing molded pulp products. The methods are particularly suited for 3D molding of products from pulp slurries. Such products may include trays, cups, plates, and various containers for packaging. [Background technology]

[0002] From WO 2016101976 it is known a method of producing a product from a pulp slurry by applying a layer of slurry to a porous mould and removing water from the slurry by simultaneously heating and pressing the layer of slurry while drawing a vacuum through a mould wall on the opposite side of which is in contact with the layer of slurry.

[0003] As disclosed in WO2016101976, the forming process may be carried out in two or more successive press steps, which is advantageous as it reduces the cycle time compared to a single press step process, thus increasing the throughput of the manufacturing process.

[0004] The production of pulp products using porous molds is associated with a variety of challenges due to the behavior of the pulp when interacting with the porous mold.

[0005] One particular problem addressed here is the formation of "whiskers" on the interior corners of the mold. These "whiskers" are the result of the accumulation of excessive amounts of pulp. These whiskers have a negative impact on subsequent forming steps as well as the appearance of the final product.

[0006] There is a need to reduce this "whisker formation." [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2016101976 Brochure Summary of the Invention

[0008] It is an object of the present disclosure to provide improved tools and methods for forming 3D molded pulp products.

[0009] The invention is defined by the accompanying independent claims, and embodiments are set out in the accompanying dependent claims, as well as the following description and drawings.

[0010] According to a first aspect, there is provided a tool for producing a 3D molded product from a pulp slurry, the tool comprising a pair of dies having respective product faces facing each other and configured to press a pulp layer therebetween, the product faces providing a 3D shape for forming the 3D molded product, the product faces presenting respective outer product end faces and defining the outermost limits of the forming areas of at least one, preferably both, of the dies, at least one of the product faces presenting, viewed inward from the product end face towards the center of gravity of the product face, an outer zone having virtually no porosity and an inner zone having a porosity of 40 to 75%, and a first intermediate zone disposed between the outer and inner zones and having a porosity greater than that of the outer zone and less than that of the inner zone.

[0011] The term "porosity" is defined as the ratio of the pore surface to the total area of ​​a given region of a zone.

[0012] By gradually reducing the porosity in the edge region, the vacuum created in the outermost portion of the mold is gradually reduced, thus preventing or eliminating the accumulation of excessive amounts of pulp in the outermost portion of the mold.

[0013] The outer zone may exhibit a porosity of less than 1%, preferably less than 0.5% or less than 0.1%.

[0014] The first intermediate zone may exhibit a porosity that is 25 to 75% of the porosity of the inner zone.

[0015] The product surface may exhibit a second intermediate zone having a porosity greater than that of the first intermediate zone but less than that of the inner zone.

[0016] The second intermediate zone may exhibit a porosity of 40 to 85% of the porosity of the inner zone.

[0017] The porous product surface may exhibit pores having a maximum cross-sectional width of 0.1 to 0.7 mm, preferably 0.25 to 0.6 mm.

[0018] The first intermediate zone may exhibit pores having an average maximum cross-sectional area that is smaller than the pores exhibited by the inner zone.

[0019] The second intermediate zone may exhibit pores having a larger average maximum cross-sectional area than the pores exhibited by the first intermediate zone.

[0020] The mold may have an edge portion extending around the periphery of the mold and presenting an angle of more than 60 degrees, preferably more than 75 degrees, or 85-90 degrees to the direction of relative movement of the mold.

[0021] The outer zone may be formed at the edge portion.

[0022] The outer zone may be bounded on the outside by a wall extending at an angle of less than 50 degrees, preferably less than 30 degrees, or between 0 and 10 degrees, relative to the direction of relative movement of the molds.

[0023] The outer zone may extend inwardly from the imaginary intersection between the wall and the edge portion a distance of less than 0.5 mm, preferably less than 0.3 mm.

[0024] Thus, there may be a soft transition between the wall and the edge portion of the mold.

[0025] An "imaginary intersection" is defined as the point where an imaginary line along the wall intersects with an imaginary line along the edge portion when viewed in a cut plane perpendicular to the wall and edge portion.

[0026] According to a second aspect of the present disclosure, there is provided a method for producing a 3D molded product from a pulp slurry, the method comprising: applying a pulp slurry layer to a porous product surface of a first mold; and, in a first forming step, heating the pulp slurry layer and pressing the pulp slurry layer against the porous product surface of the first mold while drawing a vacuum through the porous forming surface of the first mold, wherein the vacuum drawn through the porous product surface of the first mold gradually decreases toward an outer product end surface defining the outermost limit of the forming area of ​​the tool, the decrease being achieved through a gradual decrease in porosity of the porous forming surface.

[0027] The first mold may form part of a mold set in accordance with what has been described above.

[0028] The method may further include transferring the pulp slurry layer to a porous forming surface of a second mold and, in a second subsequent forming step, heating the pulp slurry layer and pressing the pulp slurry layer against the porous mold of the second mold while drawing a vacuum through the porous forming surface of the second mold.

[0029] In the first forming step, the forming surface of the first mold can be heated to about 150 to 400°C, preferably 200 to 300°C.

[0030] In the first forming step, the pulp slurry layer can be pressed against the forming surface of the first mold at a pressure of about 390 to 1570 kPa, preferably 580 to 1170 kPa.

[0031] In the first forming step, the pulp slurry layer can be pressed against the forming surface of the first die for a first pressing time of 0.1 to 4.0 seconds, preferably 0.5 to 2.0 seconds.

[0032] In the first forming step, the initial moisture content of the pulp slurry layer may be 70-90% by weight, and the final moisture content may be 45-65% by weight, preferably about 50-60% by weight.

[0033] The vacuum level behind the forming surface of the second mold may be 50 to 99 kPa, preferably 65 to 85 kPa.

[0034] The method may further include transferring the pulp slurry layer to a porous forming surface of a third mold and, in a third subsequent forming step, heating the pulp slurry layer and pressing the pulp slurry layer against the porous forming surface of the third mold while drawing a vacuum through the porous forming surface of the third mold, wherein the vacuum level in the second forming step is higher than the vacuum level in the third forming step.

[0035] The third vacuum level behind the forming surface of the third mold can be 50 to 99 kPa, preferably 65 to 85 kPa.

[0036] In the third forming step, the forming surface of the third mold can be heated to about 100 to 300°C, preferably 200 to 280°C.

[0037] In the third forming step, the pulp slurry layer can be pressed against the forming surface of the third die at a pressure of about 390 to 1570 kPa, preferably 580 to 1170 kPa.

[0038] In the third forming step, the pulp slurry layer can be pressed against the forming surface of the third die for a third pressing time of 0.1 to 4.0 seconds, preferably 0.5 to 2.0 seconds.

[0039] In the third forming step, the initial moisture content of the pulp slurry layer may be about 25 to 45% by weight or 25 to 40% by weight, preferably about 30 to 40% by weight or 30 to 35% by weight, and the final moisture content may be less than about 5% by weight, preferably less than about 1% by weight.

[0040] The first die may be a pick-up die to which the pulp slurry is applied from a liquid state, the pulp slurry having a pulp consistency of less than 0.5% by weight, preferably less than 0.49%, or 0.005 to 0.025%. [Brief explanation of the drawings]

[0041] [Figure 1a] FIG. 2 is a schematic diagram showing a molding device. [Figure 1b] FIG. 2 is a schematic diagram showing a molding device. [Figure 1c] FIG. 2 is a schematic diagram showing a molding device. [Figure 2] 1 is a schematic diagram showing a manufacturing process. [Figure 3] 1 is a schematic diagram showing the edge portions of a pair of molds 30, 40. FIG. [Figure 4] 10 is an enlarged schematic view of the edge portion of the female mold 40. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0042] 1a schematically shows a pick-up tool 10 partially immersed in a container 1 holding a pulp slurry 2. The pick-up tool is mounted on a tool holder 11, which together with the pick-up tool define a vacuum chamber 12 connected to a pressure regulator P1. The pressure regulator may be capable of selectively generating at least a partial vacuum (i.e., an air pressure less than ambient air pressure) and / or an air pressure greater than ambient air pressure.

[0043] While the pick-up tool is immersed in the pulp slurry 2, a pressure regulator P1 may create a vacuum to adhere the pulp fibers 3 to the product surface of the pick-up tool 10.

[0044] 1b shows a schematic diagram of a pickup tool 10 transferring pulp fibers 3 to a transfer tool 20. The transfer tool may be connected to a second pressure regulator P2, which may generate a vacuum or air pressure. The transfer tool may also be mounted to a transfer tool holder 21 to define a vacuum chamber 22 connected to the second pressure regulator.

[0045] During the transfer of the pulp fibers 3 from the pick-up tool to the transfer tool, an air pressure higher than ambient pressure can be generated by the first pressure regulator P1 to release the pulp fibers from the pick-up tool.

[0046] Alternatively, or additionally, a vacuum may be created by a second pressure regulator P2 such that the pulp fibers are received by the transfer tool 20.

[0047] Figure 1c shows a schematic representation of a press arrangement comprising a male press tool 30 and a female press tool 40. One or both of the press tools may be mounted in a respective tool holder 31, 41 and connected to a respective vacuum chamber 32, 42. The vacuum chambers may be connected to respective pressure regulators P3, P4.

[0048] One or both of the press tools may be provided with heating elements 33, 43, energized by energy sources E1, E2 and optionally controlled by a controller C. Heating may be achieved by hot air or liquid, or by electric heating elements such as induction.

[0049] The press tools, and their associated tool holders, may be movable relative to one another between an open position in which a partially formed pulp product may be inserted, and a press position in which the press tools are forced towards one another, thereby pressing the product 3'' between the product faces of the respective tools 30, 40.

[0050] When in the pressing position, heat may be supplied by one or both of heaters 33, 43.

[0051] During the pressing step, one or both pressure regulators P3, P4 may provide a vacuum to assist in the evacuation of water vapor from the product 3''.

[0052] Alternatively, one of the pressure regulators may provide a vacuum and the other may provide a pressure higher than ambient air pressure.

[0053] Optionally, hot air or steam may be introduced through the mold during the pressing process (FIG. 1c).

[0054] It should be noted that two or more successive pressing steps may be used, for example, to gradually form all or part of product 3'' and / or to apply additional features to the product, such as coatings, decorations, etc.

[0055] In one embodiment, steps are performed according to what is described with respect to Figures 1a, 1b, and 1c.

[0056] The manufacturing process will now be described with reference to FIG.

[0057] In a first step 101, a layer of pulp slurry is provided, for example as described with reference to FIG. 1a, and a porous pick-up tool may be submerged in the pulp slurry while applying a vacuum to the backside of the pick-up tool.

[0058] Alternatively, the pulp slurry may be applied to the pick-up tool by a coating operation, such as spray coating.

[0059] In a second step 102, the pulp slurry layer is transferred from the pick-up tool to the first press tool. The transfer can be performed by the pick-up tool or by a separate transfer tool, which can have porous transfer tool wall portions. During the transfer step, a vacuum can be applied to the back side of the transfer tool wall to hold the pulp slurry layer to the transfer tool wall. Alternatively, pressurized air can be applied to the back side of the transfer tool wall to release the pulp slurry layer from the transfer tool wall.

[0060] Alternatively, the pulp slurry layer may be applied directly to the first press tool. That is, the pulp slurry layer may be formed directly on the first press tool by applying the pulp slurry to the porous forming surface of the first press tool. The pulp slurry layer may be applied directly to the first press tool by submerging a tool part of the first press tool exhibiting a porous wall portion in the pulp slurry while applying a vacuum to the backside of the porous wall portion. Alternatively, the pulp slurry may be applied to the porous forming surface of the first press tool by a coating operation, such as spray coating.

[0061] In a third step 103, the pulp slurry layer can be pressed in a first press tool, which may include a pair of mating tool parts, one of which may have a porous wall portion in contact with the pulp slurry layer and through which a vacuum can be drawn.

[0062] In this first pressing step 103, a pressure lower than the surrounding ambient pressure is applied to the backside of the porous wall portion, thus creating a vacuum behind the porous wall portion and drawing solvent vapors, such as steam, through the tool.

[0063] The pressure applied to the backside of the porous wall portion may be a low or medium vacuum, i.e., the pressure may be higher than 1 Pa but lower than ambient pressure. Preferably, the pressure may be between 1 kPa and ambient pressure.

[0064] In the first pressing step, the first vacuum level behind the forming surface of the first mold may be about 50 to 99 kPa, typically 65 to 85 kPa.

[0065] In the first pressing step, the first pressure behind the forming surface of the first mold may be 200 to 900 mbarA (millibar absolute), preferably 300 to 800 mbarA.

[0066] The forming surface of the first mold can be heated to about 150 to 500° C., preferably 150 to 400° C., 200 to 500° C., 200 to 400° C., or 200 to 300° C., and in most cases 240 to 280° C. Typically, all mold surfaces that come into contact with the pulp slurry are heated.

[0067] The pressing pressure between the die surfaces can be about 390 to 1570 kPa, and in most cases about 580 to 1170 kPa.

[0068] The pressing pressure may be applied for a first pressing time of 0.1 to 4.0 seconds, preferably 0.5 to 2.0 seconds. In most settings, a pressing time of about 0.5 to 1.5 seconds is sufficient, and in many cases, 0.5 to 1.0 seconds is also acceptable.

[0069] Typically, in this first step, the initial moisture content of the pulp slurry layer is 70-90% by weight, and after the pressing step is performed, the final moisture content may be 45-65% by weight, typically about 50-60% by weight.

[0070] After the first pressing step 103, the pulp slurry layer, now having had a substantial amount of its solvent removed, can be transferred 104 to a second press tool. Transfer 104 can be performed in the same manner and with similar equipment as the first transfer step 102. The second press tool can be designed essentially as the first press tool.

[0071] In a second pressing step 105, the pulp slurry layer can be pressed in a second pressing tool, which may include a pair of mating tool parts, one of which may have a porous wall portion in contact with the pulp slurry layer and through which a vacuum can be drawn.

[0072] In this second pressing step 105, a pressure lower than the surrounding ambient pressure is applied to the backside of the porous wall portion, thus creating a vacuum behind the porous wall portion and drawing solvent vapors, such as steam, through the tool.

[0073] In the second pressing step, the second vacuum level behind the forming surface of the second mold can be about 50-99 kPa, typically 65-85 kPa, but always a lower vacuum level than in the first pressing step.

[0074] In the second pressing step, the second pressure behind the forming surface of the second mold may be 200 to 900 mbarA (millibar absolute), preferably 300 to 800 mbarA.

[0075] The forming surface of the second mold can be heated to about 110 to 500° C., preferably 110 to 400° C., 150 to 500° C., 150 to 400° C., 200 to 500° C., 200 to 400° C., or 200 to 300° C., and in most cases 240 to 280° C. Typically, all mold surfaces that constitute the second mold and come into contact with the pulp slurry layer can be heated.

[0076] The pressing pressure between the die surfaces can be about 390 to 1570 kPa, and in most cases about 580 to 1170 kPa.

[0077] The pressing pressure may be applied for a second pressing time of 0.1 to 4.0 seconds, preferably 0.5 to 2.0 seconds. In most settings, a pressing time of about 0.5 to 1.5 seconds is sufficient, and in many cases, 0.5 to 1.0 second is also acceptable.

[0078] Typically, in this second pressing step, the initial moisture content of the pulp slurry layer can be about 45 to 65% by weight, typically about 50 to 60% by weight.

[0079] The final moisture content may be about 25-40% by weight, preferably about 30-35% by weight.

[0080] After the second press step 105, the pulp slurry layer, now having had a substantial amount of its solvent removed, may be transferred 106 to a third press tool. Transfer 106 may be performed in the same manner and with similar equipment as the first transfer step 102 and / or the second transfer step 104. The third press tool may be designed essentially as the first press tool.

[0081] In a third press step 107, the pulp slurry layer can be pressed in a third press tool, which may include a pair of mating tool parts, one of which may have a porous wall portion in contact with the pulp slurry layer and through which a vacuum can be drawn.

[0082] In this third pressing step 107, a pressure lower than the surrounding ambient pressure is applied to the backside of the porous wall portion, thus creating a vacuum behind the porous wall portion and drawing solvent vapors, such as steam, through the tool.

[0083] In the third pressing step, the third vacuum level behind the forming surface of the third mold can be about 50 to 99 kPa, typically 65 to 85 kPa, but always a lower vacuum level than in the second pressing step.

[0084] In the third pressing step, the third pressure behind the forming surface of the third mold may be 200 to 900 mbarA (millibar absolute), preferably 300 to 800 mbarA.

[0085] The forming surface of the third mold can be heated to about 100 to 400° C., preferably 100 to 300° C., 150 to 400° C., 150 to 300° C., 200 to 300° C., or 200 to 280° C., and in most cases 240 to 280° C. Typically, all mold surfaces that make up the third mold and come into contact with the pulp slurry layer can be heated.

[0086] The pressing pressure between the die surfaces can be about 390 to 1570 kPa, and in most cases about 580 to 1170 kPa.

[0087] The pressing pressure may be applied for a third pressing time of 0.1 to 4.0 seconds, preferably 0.5 to 2.0 seconds. In most settings, a pressing time of about 0.5 to 1.5 seconds is sufficient, and in many cases, 0.5 to 1.0 second is also acceptable.

[0088] Typically, in this third pressing step, the initial moisture content of the pulp slurry layer can be about 25-45% by weight or 25-40% by weight, preferably about 30-40% by weight or 30-35% by weight, and the final moisture content can be less than about 5% by weight, preferably less than about 1% by weight.

[0089] After the third pressing step 107, the pulp slurry layer, now freed of most of its solvent, can be transported 108 from the machine.

[0090] Optionally, additional steps may be performed on this essentially dried product, such as surface treatment, cutting, or printing, etc. The product may then be packaged, stored, and shipped.

[0091] It should be noted that the third pressing step 107, and thus its associated transfer step 106, is also optional. Thus, the process may end after the second pressing step 105, which is immediately followed by the output step 108.

[0092] Therefore, in the first pressing step, the initial moisture content of the pulp slurry layer may be 70-90% by weight, and the final moisture content may be 25-50% by weight, preferably about 30-35% by weight.

[0093] In the second pressing step, the initial moisture content of the pulp slurry layer may be about 25 to 50% by weight, preferably about 30 to 35% by weight, and the final moisture content may be less than about 5% by weight, preferably less than about 1% by weight.

[0094] 3 and 4, an edge portion of a tool set is shown.

[0095] 3 shows male mold 30 and female mold 40 having respective out-of-plane portions 301, 401 and respective edge portions 302, 402 surrounding the respective out-of-plane portions 301, 401. The edge portions may, but do not necessarily, also include respective outer edge walls 303, 403 formed on the outermost portions of the edges 302, 402.

[0096] The edges 302, 402 may be substantially planar and may surround the out-of-plane portions 301, 401.

[0097] The edge portions may be substantially planar and extend substantially perpendicular to the direction of relative movement of the dies during the final part of the pressing operation, while the edge walls 303, 403 may extend substantially perpendicular to the edge portions 302, 402.

[0098] In practice, the edge portions 302, 402 may extend at an angle of 60-90 degrees, preferably 75-90 degrees, 85-90 degrees, or 89-90 degrees to the direction of movement.

[0099] Similarly, the wall portions 303, 403 may extend at an angle of 0 to 60 degrees relative to the direction of movement, preferably 0 to 45 degrees, 0 to 30 degrees, 0 to 15 degrees, 0 to 5 degrees, or 0 to 1 degree.

[0100] The edge portions may extend from an imaginary intersection between the surfaces of the wall portions 303, 403 and the edge portions 302, 402. Thus, for each mold, there may be a soft transition between the wall 303, 403 and the edge portions 302, 402, respectively, the "imaginary intersection" being the point where an imaginary line along the wall intersects with an imaginary line along the edge portion when viewed in a cutting plane perpendicular to the wall and the edge portions.

[0101] The edge portions may range from 1 to 15 mm in total, with each zone extending over less than 1 mm, preferably less than 0.5 mm, or less than 0.3 mm.

[0102] As noted above, one or both of the molds 30, 40 may have a porous forming surface. In the illustrated example, the female mold 40 is shown as having a porous forming surface, but this may also or instead be the male mold 30 having a porous forming surface.

[0103] The central portion of the mold 30, 40 may have a predetermined nominal porosity, which may be constant or may vary across the central portion.

[0104] The central portion may be anything inside the edge portion or any transition from the edge portion to the wall.

[0105] The edge portion 402 may have a gradually decreasing porosity, resulting in zero porosity at the outermost portion of the edge portion 402 .

[0106] In the illustrated example, the edge portion 402 is divided into three zones: a first zone Z1 having zero or very low porosity, a second zone Z2 having a higher porosity, a third zone Z3 optionally having an even higher porosity than the second zone Z2, and then an inner zone Z4 having a nominal porosity. The inventions described in the original claims of this application are set forth below. [1] 1. A tool for producing a 3D shaped product from a pulp slurry, comprising: a pair of dies having respective product surfaces facing each other and configured to press the pulp layer therebetween; the product surface provides a 3D shape for forming the 3D molded product; the product surfaces present respective outer product edge surfaces and define the outermost limits of the forming regions of at least one of the molds; At least one of the product faces, looking inward from the product end face toward the center of gravity of the product face, an outer zone (Z1) that is virtually free of porosity; an inner zone (Z4) with a porosity of 40-75%; Presenting, A tool characterized by a first intermediate zone (Z2) disposed between said outer zone (Z1) and said inner zone (Z4), said first intermediate zone (Z2) having a porosity higher than that of said outer zone (Z1) and lower than that of said inner zone (Z4). [2] 10. The tool according to claim 1, wherein the outer zone (Z1) exhibits a porosity of less than 1%, preferably less than 0.5% or less than 0.1%. [3] The tool according to [1] or [2], wherein the first intermediate zone (Z2) exhibits a porosity of 25 to 75% of the porosity of the inner zone. [4] The tool according to any one of [1] to [3], wherein the product surface presents a second intermediate zone (Z3) having a porosity higher than the porosity of the first intermediate zone but lower than the porosity of the inner zone. [5] The tool according to [4], wherein the second intermediate zone (Z3) exhibits a porosity of 40 to 85% of the porosity of the inner zone. [6] The tool according to any one of [1] to [5], wherein the porous product surface exhibits pores having a maximum cross-sectional width of 0.1 to 0.7 mm, preferably 0.25 to 0.6 mm. [7] [6] The tool according to [6], wherein the first intermediate zone (Z2) exhibits pores having an average maximum cross-sectional area smaller than the pores exhibited by the inner zone (Z4). [8] [7] The tool according to [7], wherein the second intermediate zone (Z3) exhibits pores having an average maximum cross-sectional area greater than the pores exhibited by the first intermediate zone (Z2). [9] 10. The tool according to any one of [1] to [8], wherein the mold has an edge portion (302, 402) extending around the periphery of the mold and presenting an angle of more than 60 degrees, preferably more than 75 degrees, or 85 to 90 degrees with respect to the direction of relative movement of the mold.

[10] The tool according to [9], wherein the outer zone (Z1) is formed in the edge portion (302, 402).

[11] The tool according to [9] or

[10] , wherein the outer zone (Z1) is bounded on the outside by a wall (303, 403) extending at an angle of less than 50 degrees, preferably less than 30 degrees, or 0 to 10 degrees, relative to the direction of relative movement of the mold.

[12] The tool according to any one of [9] to

[11] , wherein the outer zone (Z1) extends inward from a virtual intersection between the wall (303, 403) and the edge portion (302, 402) by a distance of less than 0.5 mm, preferably less than 0.3 mm.

[13] 1. A method for producing a 3D shaped product from a pulp slurry, comprising: applying a layer of pulp slurry to the porous product surface of the first mold; a first forming step of heating the pulp slurry layer and pressing the pulp slurry layer against the porous product surface of the first die while drawing a vacuum through the porous product surface of the first die; Equipped with the vacuum drawn through the porous product surface of the first mold is gradually reduced toward an outer product end surface defining the outermost limit of the forming area of ​​the tool; The method wherein said reduction is achieved through a gradual decrease in porosity of said porous product surface.

[14] transferring the pulp slurry layer to a porous forming surface of a second mold; in a second subsequent forming step, heating the pulp slurry layer and pressing the pulp slurry layer against the porous forming surface of the second mold while drawing a vacuum through the porous forming surface of the second mold; The method according to

[13] , further comprising:

[15] The method according to

[13] or

[14] , wherein in the first forming step, the forming surface of the first mold is heated to about 150 to 400°C, preferably 200 to 300°C.

[16]

[16] The method according to any one of

[13] to

[15] , wherein in the first forming step, the pulp slurry layer is pressed against the forming surface of the first mold at a pressure of about 390 to 1570 kPa, preferably 580 to 1170 kPa.

[17]

[16] . The method according to any one of

[13] to

[16] , wherein in the first forming step, the pulp slurry layer is pressed against the forming surface of the first mold for a first pressing time of 0.1 to 4.0 seconds, preferably 0.5 to 2.0 seconds.

[18]

[13] to

[17] , wherein in the first forming step, the initial moisture content of the pulp slurry layer is 70 to 90% by weight, and the final moisture content is 45 to 65% by weight, preferably about 50 to 60% by weight.

[19] The method according to any one of

[14] to

[18] , wherein the vacuum level on the back side of the forming surface of the second mold is 50 to 99 kPa, preferably 65 to 85 kPa.

[20]

[14] to

[19] , further comprising the steps of: transferring the pulp slurry layer to a porous forming surface of a third mold; and in a third subsequent forming step, heating the pulp slurry layer and pressing the pulp slurry layer against the porous forming surface of the third mold while drawing a vacuum through the porous forming surface of the third mold, wherein the vacuum level in the second forming step is higher than the vacuum level in the third forming step.

[21]

[20] The method according to

[20] , wherein the third vacuum level on the back side of the forming surface of the third mold is 50 to 99 kPa, preferably 65 to 85 kPa.

[22] The method according to

[20] or

[21] , wherein in the third forming step, the forming surface of the third mold is heated to about 100 to 300°C, preferably 200 to 280°C.

[23]

[20] The method according to any one of

[20] to

[22] , wherein in the third forming step, the pulp slurry layer is pressed against the forming surface of the third mold at a pressure of about 390 to 1570 kPa, preferably 580 to 1170 kPa.

[24]

[20] to

[23] , wherein in the third forming step, the pulp slurry layer is pressed against the forming surface of the third mold for a third pressing time of 0.1 to 4.0 seconds, preferably 0.5 to 2.0 seconds.

[25]

[20] The method according to any one of

[20] to

[24] , wherein in the third forming step, the initial moisture content of the pulp slurry layer is about 25 to 45% by weight or 25 to 40% by weight, preferably about 30 to 40% by weight or 30 to 35% by weight, and the final moisture content is less than about 5% by weight, preferably less than about 1% by weight.

[26] The method according to any one of

[20] to

[25] , wherein the first mold is a pick-up mold to which the pulp slurry is applied from a liquid state, and the pulp slurry has a pulp concentration of less than 0.5% by weight, preferably less than 0.49%, or 0.005 to 0.025%.

Claims

1. 1. A method for producing a 3D shaped product from a pulp slurry, comprising: a pair of dies having respective product surfaces facing each other and configured to press the pulp layer therebetween; the product surface provides a 3D shape for forming the 3D molded product; the product surfaces present respective outer product edge surfaces and define the outermost limits of the forming regions of at least one of the molds; At least one of the product faces, looking inward from the product end face toward a center of gravity of the product face, an outer zone (Z1) that is virtually free of porosity; an inner zone (Z4) having a porosity of 40-75%; a first intermediate zone (Z2) disposed between the outer zone (Z1) and the inner zone (Z4), the first intermediate zone (Z2) having a porosity higher than that of the outer zone (Z1) and lower than that of the inner zone (Z4); The method comprises: applying a layer of pulp slurry to the porous product surface of a first die of said tool; further comprising pressing the pulp slurry layer to form the three-dimensional shaped product in at least one forming step; The method comprises: a first forming step comprising pressing the pulp slurry layer against the porous product surface of the first mold while heating the pulp slurry layer; method.

2. the pressing is performed while drawing a vacuum through the porous product surface of the first mold; the vacuum drawn through the porous product surface of the first mold is gradually reduced toward the outer product end surface defining the outermost limit of the forming area of ​​the first mold; The method of claim 1 , wherein the reduction is achieved through a gradual decrease in porosity of the porous product surface of the first mold.

3. transferring the pulp slurry layer to a porous forming surface of a second mold; in a second subsequent forming step, heating the pulp slurry layer and pressing the pulp slurry layer against the porous forming surface of the second mold while drawing a vacuum through the porous forming surface of the second mold; The method of claim 1 or 2, further comprising:

4. The method described in claim 3, wherein the vacuum level on the back side of the forming surface of the second mold is 50 to 99 kPa.

5. 5. The method according to claim 1, wherein in the first forming step, the forming surface of the first mold is heated to about 150 to 400°C.

6. The method of any one of claims 1 to 5, wherein in the first forming step, the pulp slurry layer is pressed against the forming surface of the first mold at a pressure of about 390 to 1570 kPa.

7. 7. The method according to claim 1, wherein in the first forming step, the pulp slurry layer is pressed against the forming surface of the first die for a first pressing time of 0.1 to 4.0 seconds.

8. 8. The method according to claim 1, wherein in the first forming step, the pulp slurry layer has an initial moisture content of 70 to 90% by weight and a final moisture content of 45 to 65% by weight.

9. 9. The method of claim 3, further comprising the steps of: transferring the pulp slurry layer to a porous forming surface of a third mold; and in a third subsequent forming step, heating the pulp slurry layer and pressing the pulp slurry layer against the porous forming surface of the third mold while drawing a vacuum through the porous forming surface of the third mold, wherein the vacuum level in the second forming step is higher than the vacuum level in the third forming step.

10. 10. The method of claim 9, wherein a third vacuum level behind the forming surface of the third mold is between 50 and 99 kPa.

11. 11. The method according to claim 9, wherein in the third forming step, the forming surface of the third mold is heated to about 100 to 300°C.

12. 12. The method of claim 9, wherein in the third forming step, the pulp slurry layer is pressed against the forming surface of the third mold at a pressure of about 390 to 1570 kPa.

13. 13. The method according to claim 9, wherein in the third forming step, the pulp slurry layer is pressed against the forming surface of the third die for a third pressing time of 0.1 to 4.0 seconds.

14. 14. The method according to claim 9, wherein in the third forming step, the initial moisture content of the pulp slurry layer is about 25 to 45% by weight or 25 to 40% by weight, and the final moisture content is less than about 5% by weight.

15. 15. The method of any one of claims 9 to 14, wherein the first die is a pick-up die to which a pulp slurry is applied from a liquid state, the pulp slurry having a pulp consistency of less than 0.5% by weight.

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