DEVICE AND METHOD FOR PRODUCING A 3D MOLDED PULP PRODUCT

Abstract

The document relates to a device for producing a 3D molded product from a pulp slurry, comprising a pair of cooperating press tools, each having a respective product face. The press tools are movable relative each other between a closed press position, wherein the product faces are sufficiently close to press the pulp product there between, and an open transfer position, wherein the pulp product can be removed from the product face of one of the press tools. At least one of the product faces is porous. The device further comprises a radiation heater, which is adapted to radiate heat towards the product face of the porous press tool, when the porous press tool is in its open position.

Claims

1-45. (canceled)

46. A device for producing a 3D molded product from a pulp slurry, comprising: a pair of cooperating press tools, each having a respective product face, the press tools being movable relative each other between a closed press position, wherein the product faces are sufficiently close to press the pulp product there between, and an open transfer position, wherein the pulp product can be removed from the product face of one of the press tools, wherein at least one of the product faces is porous, and wherein the device further comprises a radiation heater, which is adapted to radiate heat from a front side of the porous press tool towards the product face of the porous press tool, when the porous press tool is in its open position.

47. The device according to claim 46, wherein the radiation heater is movable between a heating position and a passive position, wherein the movable radiation heater is adapted to be in the heating position when the press tools are in their open position, and adapted to be in the passive position when the press tools are in their closed position.

48. The device according to claim 47, wherein the movable radiation heater, in its heating position, is configured to be inserted at a preset distance from the product face of the porous press tool.

49. The device according to claim 46, wherein the radiation heater is external such that the radiation heater is arranged externally in relation to the pair of cooperating press tools as seen when arranged in their respective tool holders.

50. The device according to claim 49, further comprising a tool transport member, adapted to move the porous press tool to the external radiation heater for heating of the product face of the porous press tool.

51. The device according to claim 46, comprising at least two porous press tools.

52. The device according to claim 50, wherein the device further comprises a changing device, adapted to, in-between two subsequent pressing operations of the pair of press tools, change between the at least two porous press tools, such that one of the at least two porous press tool is used in a first pressing operation and another one is used in a second, subsequent pressing operation.

53. The device according to claim 51, wherein the changing device further is adapted to move one porous press tool from a tool holder of the porous press tool to the external radiation heater, and move another heated porous press tool from the external radiation heater to the tool holder.

54. The device according to claim 46, wherein the device further comprises a second pair of cooperating press tools, each having a respective product face, the second pair of cooperating press tools being movable relative each other between a closed press position, wherein the product faces are sufficiently close to press the pulp product there between, and an open transfer position, wherein the pulp product can be removed from the product face of one of the press tools of the second pair of cooperating press tools, wherein at least one of the product faces of the second pair of cooperating press tools is porous, and wherein the device further comprises a second radiation heater which is adapted to radiate heat towards the product face of the porous press tool of the second pair of press tools, when the porous press tool is in its open position.

55. The device according to claim 53, wherein the device further comprises a third pair of cooperating press tools, each having a respective product face, the third pair of cooperating press tools being movable relative each other between a closed press position, wherein the product faces are sufficiently close to press the pulp product there between, and an open transfer position, wherein the pulp product can be removed from the product face of one of the press tools of the third pair of cooperating press tools, wherein at least one of the product faces of the third pair of cooperating press tools is porous, and wherein the device further comprises a third radiation heater which is adapted to radiate heat towards the product face of the porous press tool of the third pair of press tools, when the porous press tool is in its open position.

56. A method of producing a 3D molded product from a pulp slurry comprising: providing a first and a second pair of cooperating press tools, each press tool having a respective product face, wherein at least one of the product faces of each pair of tools is porous, applying a pulp slurry layer to one of the product faces of the first pair of press tools, in a first forming step, pressing the pulp slurry layer between the first pair of press tools, while heating the pulp slurry layer and drawing a vacuum through the product face of the porous press tool, transferring the pulp slurry layer to a product face of the second pair of press tools, in a second, subsequent, forming step, pressing the pulp slurry layer between the second pair of press tools, while heating the pulp slurry layer and drawing a vacuum through the product face of the porous press tool, wherein the method further comprises: heating the product face of at least one of the porous press tools by radiating heat from a radiation heater from a front side of the porous press tool towards the product face of the porous press tool.

57. The method as claimed in claim 56, wherein the step of heating the product face of each porous press tool comprises inserting the radiation heater at a preset distance from the product face of the porous press tool, heating the product face by radiating heat from the radiation heater towards the product face, and withdrawing the radiation heater.

58. The method as claimed in claim 56, wherein the step of heating the product face of each porous press tool comprises moving the porous press tool from a tool holder of the porous press tool to the radiation heater, heating the product face by radiating heat from the radiation heater towards the product face, and moving the porous press tool from the radiation heater to the tool holder.

59. The method as claimed in claim 56, further comprising providing at least two porous press tools for each pair of cooperating press tools.

60. The method as claimed in claim 59, wherein, in-between two subsequent pressing operations of each pair of press tools, a change is performed between the at least two porous press tools, such that one of the at least two porous press tools is used in a first pressing operation and another one is used in a second, subsequent pressing operation.

61. The method as claimed in claim 59, wherein one of the at least two porous press tools for each pair of cooperating press tools is heated simultaneously as another one is used for pressing in the corresponding forming step.

62. The method as claimed in claim 59, wherein each pair of cooperating press tools comprises one press tool presenting a porous product face and one press tool presenting a less porous product face.

63. The method as claimed in claim 59, wherein each pair of cooperating press tools comprises one press tool presenting a porous product face and one press tool presenting a non-porous product face.

64. The method as claimed in claim 62, wherein the product face of the less porous press tool is heated to a higher temperature than the porous press tool.

65. The method as claimed in claim 62, wherein the product face of the porous press tool is heated to a temperature corresponding to 20-80% of the temperature of the less porous press tool.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0094] Embodiments of the present solution will now be described, by way of example, with reference to the accompanying schematic drawings in which:

[0095] FIGS. 1a-1b schematically illustrate one embodiment of a molding device comprising a movable radiation heater.

[0096] FIG. 1c-1d schematically illustrate one embodiment of a molding device comprising an external radiation heater.

[0097] FIG. 2a-c schematically illustrate one embodiment of a molding device comprising at least two porous press tools.

[0098] FIG. 3 schematically illustrate one embodiment of a molding device.

[0099] FIG. 4 schematically illustrates a production process.

DESCRIPTION OF EMBODIMENTS

[0100] FIG. 1a-1b, FIG. 1c-1d and FIG. 2a-2c schematically illustrate a device for producing a 3D molded product from a pulp slurry. The device comprises a pair of cooperating press tools 30, 40.

[0101] One, or both, of the pressing tools may be mounted on a respective tool holder 31, 41. One, or both, of the pressing tools may be connected to a respective vacuum chamber 32, 42. The vacuum chambers may be connected to a respective pressure regulator P3, P4.

[0102] The pressure regulator may have the capability of selectively generating an at least partial vacuum (i.e. air pressure lower than ambient air pressure) and/or an air pressure greater than ambient pressure.

[0103] Each of the press tools 30, 40 has a respective product face. At least one of the product faces is porous. Consequently, the pair of cooperating press tools 30, 40 comprises at least one porous press tool.

[0104] The other press tool of the cooperating press tools may have a porous product face or a non-porous product face, or a partly non-porous product face. For example, some portions may be non-porous, e.g. such portions where a specific surface structure is desired.

[0105] The at least one porous press tool can be self-supporting, meaning that a tool wall portion of the tool is sufficiently rigid and has a melting point that is sufficiently high for the tool wall portion not to require any support structure for maintaining its shape during operation.

[0106] In the illustrated example, press tool 40 is a porous press tool.

[0107] In the illustrated example, press tool 30 is a less porous press tool, as compared with the porous press tool 40.

[0108] The press tools 30, 40 and their associated tool holders 31, 41 is movable relative each other between a closed press position and an open transfer position. In the closed position the product faces of the respective tool 30, 40 are sufficiently close to press a pulp product 3′ 3″ there between. In the open position, a pulp slurry layer or pulp product 3′, 3″ may be inserted or removed from the product face of one of the press tools.

[0109] One of the press tools 30, 40, preferably the less porous press tool, may be provided with a heating element, energized by an energy supply E1 and optionally controlled by a controller C.

[0110] Alternatively, a rear radiation heater (not illustrated) may be provided at a rear side of one of the press tools 30, 40, preferably the less porous press tool. The rear radiation heater is adapted to heat radiate heat from the rear side of the press tool towards the product face of the press tool. Consequently, heat is being conducted from the rear side of the press tool, through a body of said tool, and to the product face of said tool.

[0111] In the illustrated example of FIG. 1a-1d and FIG. 2a-2c, the less porous press tool 30 is provided with a heating element 33, adapted to supply heat to the product face of the tool 30, when in the closed press position of the press tools. The heating may be achieved by electric heating elements, hot air or liquid or induction, or any combination thereof.

[0112] The device according to the present invention further comprises a radiation heater 50, 60. The radiation heater 50,60 is adapted to radiate heat towards the product face of the at least one porous press tool of the cooperating press tools.

[0113] In the illustrated example of FIG. 1a-1d and FIG. 2a-2c, the radiation heater 50, 60 is adapted to heat radiate heat from a front side of the porous press tool 40 towards the product face of the porous press tool 40, when the porous press tool 40 is in its open position.

[0114] The radiation heater and the porous press tool may be movable relative each other between a heating position and a passive position. When the radiation heater is in a passive position, the porous press tool may be in a molding position, i.e. used for pressing.

[0115] The radiation heater can be a movable radiation heater 50, see FIG. 1a-1b. Alternatively, the radiation heater can be an external radiation heater 60, see FIG. 1c-1d.

[0116] FIG. 1a-1b schematically illustrates one possible embodiment of the device for producing a 3D molded product from a pulp slurry, wherein the radiation heater is a movable radiation heater 50. The radiation heater 50 is movable between a heating position (see FIG. 1a) and a passive position (see FIG. 1b).

[0117] The movable radiation heater 50 may be adapted to be in the heating position when the press tools 30, 40 are in their open position, and adapted to be in the passive position when the press tools 30, 40 are in their closed position.

[0118] The movable radiation heater can, in its heating position, be inserted at a front side of the porous press tool 40, at a preset distance from the product face of the porous press tool 40, see FIG. 1a.

[0119] The product face of the porous press tool 40 may be heated in-between two subsequent pressing operations of the press tools 30, 40. Consequently, the movable radiation heater 50 may be configured to be moved into the heating position in-between two subsequent pressing operations, i.e. at the open position of the press tools 30,40, whereby the product face of the porous press tool 40 is heated to a preset temperature by the movable radiation heater radiating heat towards the product face. After the heating, the movable radiation heater 50 may also be configured to be withdrawn from the porous tool 40.

[0120] FIG. 1c-1d schematically illustrates an alternative embodiment of the device for producing a 3D molded product from a pulp slurry, wherein the radiation heater is an external radiation heater 60.

[0121] The device can further comprise a tool transport member 80. The tool transport member 80 can be adapted to move the porous press tool 40 to the external radiation heater 60 for heating of the product face of the porous press tool 40.

[0122] Consequently, the tool transport member can be configured to move the porous press tool 40 from the tool holder 41 of the porous press tool to the external radiation heater 60. The tool transport member can further be configured to move the porous press tool 40 from the external radiation heater 60 to the tool holder 41 of the porous press tool. Alternatively, a second tool transport member (not illustrated) can be configured to move the porous press tool 40 from the external radiation heater 60 to the tool holder 41.

[0123] FIG. 1c illustrates the press tools 30, 40 in their open position, wherein the porous press tool 40 has been moved to the radiation heater for heating of the product face of the press tool.

[0124] FIG. 1d illustrates the press tools 30, 40 in their closed position.

[0125] The product face of the porous press tool 40 may be heated in-between two subsequent pressing operations of the press tools 30, 40. Consequently, the tool transport member 80 may be configured to move the porous press tool 40 from its tool holder 41 to the external radiation heater 60 in-between two subsequent pressing operations, i.e. at the open position of the press tools 30, 40, whereby the product face of the porous press tool 40 is heated to a preset temperature by the external radiation heater 60, see FIG. 1c. The tool transport member 80 can also be configured to move the porous press tool 40 from the external radiation heater 60 to the tool holder 41 of the porous press tool.

[0126] The device according to the invention may comprise at least two porous press tools 40a, 40b, which is illustrated in FIG. 2a-2c.

[0127] The device may further comprise a changing device 70, see FIG. 2b.

[0128] The changing device 70 can be adapted to, in-between two subsequent pressing operations of the pair of press tools 30, 40, change between the at least two porous press tools 40a, 40b. In that way, one of the at least two porous press tool 40a can be used in a first pressing operation and another one 40b can be used in a second, subsequent pressing operation, see FIG. 2a-2c.

[0129] The changing device 70 can further be adapted to move one porous press tool from a tool holder 41 of the porous press tool to the external radiation heater 60, and move another heated porous press tool from the external radiation heater 60 to the tool holder 41.

[0130] Consequently, according to one possible embodiment, the changing device 70 can both act as a tool transport member and change which of the at least two porous press tool 40a, 40b is used for pressing.

[0131] The changing device 70 can move one porous press tool from the external radiation heater 60 simultaneously as another porous press tool is moved to the external radiation heater 60.

[0132] It is noted that the device according to the invention, can comprise a plurality of pair of cooperating press tools which can be used in subsequent pressing steps. The plurality of pair of cooperating press tools can be designed essentially as the first pair of cooperating press tools as described above.

[0133] The device can also comprise a plurality of radiation heaters.

[0134] The product faces of the at least one porous press tool of each pair of press tool may be heated by the same radiation heater, or by different radiation heaters.

[0135] The device can further comprise a pick-up tool and one or several transfer tools which will be described in more detail in relation to FIGS. 3a and 3b.

[0136] In relation to FIG. 3a-3c and FIG. 4, a method for producing a 3D molded pulp product will now be described.

[0137] FIG. 3a schematically illustrates a pickup tool 10 which is partially immersed in a container 1 holding a pulp slurry 2. The pickup tool is mounted to a tool holder 11, which together with the pickup tool defines a vacuum chamber 12 that is connected to a pressure regulator P1. The pressure regulator may have the capability of selectively generating an at least partial vacuum (i.e. air pressure lower than ambient air pressure) and/or an air pressure greater than ambient air pressure.

[0138] While the pickup tool is immersed in the pulp slurry 2, the pressure regulator P1 may generate a vacuum, causing pulp fibers 3 to stick to a product face of the pickup tool 10.

[0139] FIG. 3b schematically illustrates the pickup tool 10 transferring the pulp fibers 3 to a transfer tool 20. The transfer tool may be connected to a second pressure regulator P2, which is capable of generating a vacuum or an air pressure. The transfer tool may also be mounted on a transfer tool holder 21 so as to define a vacuum chamber 22, which is connected to the second pressure regulator.

[0140] During the transfer of the pulp fibers 3 from the pickup tool to the transfer tool, an air pressure greater than ambient pressure may be generated by the first pressure regulator P1 to cause the pulp fibers to release from the pickup tool.

[0141] Alternatively, or as a supplement, a vacuum may be generated by the second pressure regulator P2, causing the pulp fibers to be received by the transfer tool 20.

[0142] FIG. 3c schematically illustrates a pressing arrangement in a closed pressing position, wherein the pressing arrangement comprises a pair of cooperating press tools, in similar with the pair of press tools described in relation to FIG. 1a-1d and FIG. 2a-2c. The cooperating press tools 30, 40 each presents a product face. At least one of the product faces is porous.

[0143] When in the pressing position, the pulp product 3″ may be heated by at least one of the product faces of the press tools 30, 40. Preferably, all product faces contacting the pulp slurry layer are heated.

[0144] The product face of the press tool 30 can be heated by suppling heat from the heating element 33. Alternatively, it may be heated by a rear radiation heater radiating heat at a rear side of the tool.

[0145] The product face of the porous press tool 40 can be heated by a radiation heater as described above in relation to FIG. 1a-1b, FIG. 1c-1d or FIG. 2a-2c. The heating of the product face of the porous press tool 40 may be performed before the pressing step, when the porous press tool 40 is in its open position.

[0146] Alternatively, at least two porous press tools 40a, 40b can be provided and the heating of one of the porous press tools can be performed simultaneously as another already heated porous press tool is used for pressing.

[0147] 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″.

[0148] As an alternative, one of the pressure regulators may provide a vacuum while the other one provides a pressure greater than the ambient air pressure.

[0149] Optionally, hot air or steam may be introduced through the molds during the pressing process (FIG. 3c).

[0150] It is noted that two or more successive pressing steps may be used, e.g. to gradually form all or parts of the product 3″ and/or to apply additional features to the product, such as coatings, decors and the like.

[0151] In one embodiment, steps are performed in accordance with what has been described with respect to FIGS. 3a, 3b and 3c.

[0152] Referring to FIG. 4, a production process will now be described.

[0153] In a first step 101, a pulp slurry layer is provided, e.g. as described with reference to FIG. 3a, wherein a porous pickup tool may be submerged in a pulp slurry with vacuum being applied to a rear side of the pickup tool.

[0154] Alternatively, the pulp slurry may be applied to the pickup tool by a coating operation, such as spray coating or pouring.

[0155] The porous wall portion of the pickup tool may have a surface porosity of 10-90%. A plurality of channel openings, or slots, or holes of the porous product face may be of the sizes 0.1-0.7 mm in diameter, preferably 0.25-0.6 mm.

[0156] In a second step 102, the pulp slurry layer is transferred from the pickup tool to a product face of a first pair of cooperating press tools. The transfer may be performed by the pickup tool, or by means of a separate transfer tool, which may have a transfer tool wall portion that is porous. During the transfer step, a vacuum may be applied to the rear side of the transferring tool wall, such that the pulp slurry layer is held to the transferring tool wall. In order to release the pulp slurry layer from the transferring tool wall, it is possible to instead apply pressurized air to the rear side of the transferring tool wall.

[0157] Alternatively, the pulp slurry layer may be applied directly to the product face of one of the first pair of press tools. That is, the pulp slurry layer may be formed directly on one of the first pair of press tools by application of the pulp slurry to a porous product face of one of the first pair of press tools. The pulp slurry layer may be applied directly to said press tool by submerging the tool presenting a porous wall portion in a pulp slurry with vacuum being applied to a rear side of the porous wall portion. Alternatively, the pulp slurry may be applied to the porous product face of said press tool by a coating operation, such as spray coating.

[0158] In a third step 103, the pulp slurry layer may be pressed between the first pair of press tools. At least one of the press tools may have a porous wall portion, which contacts the pulp slurry layer, and through which a vacuum can be drawn.

[0159] The first pair of cooperating press tools may comprise one press tool presenting a porous product face and one press tool presenting a less porous product face.

[0160] In this first pressing step 103a, a pressure lower than the surrounding ambient pressure is applied at a rear side of the porous wall portion, thus resulting in a vacuum at the rear side of the porous wall portion, causing solvent vapor, such as steam, to be drawn through the tool.

[0161] The porous wall portion of the porous press tool of the first pair of press tools may have a surface porosity of 10-90% with hole sizes 0.1-0.7 mm, preferably 0.25-0.6 mm.

[0162] The pressure applied to the rear side of the porous wall portion may be on the order of low or medium level vacuum. That is, a first pressure may be 200-900 mbarA (millibar absolute), preferably 300-800 mbarA.

[0163] In the first pressing step 103a, typically, all product faces contacting the pulp slurry layer are heated.

[0164] The product face of the porous press tool of the first pair of press tools can be preheated by a radiation heater, as described in relation to FIG. 1a-1b, FIG. 1c-d, or FIG. 2a-2c, such that an initial pressing temperature of the product face of the porous press tool is about 100-300° C., preferably 150-250° C., and more preferably 160-240° C.

[0165] After the pressing, the temperature of the product face of porous press tool can be 25-75% of the initial pressing temperature.

[0166] Consequently, the step of heating the product face of the porous press tool can comprise inserting the radiation heater at a front side of the product face of the porous press tool, at a preset distance from the product face of the porous press tool and heating the product face to a preset temperature, by radiating heat from the radiation heater towards the product face. The heating step can further comprise withdrawing the radiation heater from the porous press tool.

[0167] Alternatively, the step of heating the product face of the porous press tool can comprise moving the porous press tool from a tool holder of the porous press tool to the radiation heater and heating the product face to a preset temperature, by radiating heat from the radiation heater towards the product face. The heating step can further comprise moving the porous press tool from the radiation heater back to the tool holder.

[0168] The heating of the product face of the porous press tool by a radiation heater may be performed before step 103a, i.e. before or during step 101 and 102, or alternatively as an additional step between 102 and 103a.

[0169] As an alternative, at least two porous press tools can be provided for the first pair of cooperating press tools.

[0170] Consequently, at least one of the at least two porous press tools can be heated simultaneously 103b as another one is used for pressing in the corresponding pressing step 103a.

[0171] Then, in-between two subsequent pressing operations of the first pair of press tools, a change can be performed between the at least two porous press tools, such that one of the at least two porous press tool can be used in a first pressing operation and another one can be used in a second, subsequent pressing operation of the first pair of press tools.

[0172] Further, in the first pressing step 103a, the product face of the less porous press tool may be heated to about 200-500° C., preferably 300-400° C.

[0173] The product face of the less porous press tool may be heated to a higher temperature than the porous press tool.

[0174] The porous press tool may be heated to a temperature corresponding to 20-80% of the temperature of the less porous press tool, preferably 25-50%.

[0175] A pressing pressure between the first pair press tools may be on the order of about 390-1570 kPa, and in most cases 580-1170 kPa.

[0176] The pressing pressure may be applied during a first pressing time of 0.1-4.0 second, preferably 0.5-2.0 second. In most settings, a pressing time on the order of 0.5-1.5 second is sufficient, and often also 0.5-1 second.

[0177] Typically, in this first step, an initial water content of the pulp slurry layer is 70-90% by weight and after the pressing step has been performed, a final water content may be 45-65% by weight, typically about 50-60% by weight.

[0178] After the first pressing step 103a, the pulp slurry layer, now with a substantial amount of its solvent removed, may be transferred 104 to a product face of a second pair of cooperating press tools. The transfer 104 may be performed in the same manner as the first transfer step 102, and with similar equipment. The second pair of press tools may be designed essentially as the first pair of cooperating press tools.

[0179] In a second pressing step 105a, the pulp slurry layer may be pressed between the second pair of press tools. At least one of the press tools may have a porous wall portion, which contacts the pulp slurry layer, and through which a vacuum can be drawn.

[0180] The pair of cooperating press tools may comprise one press tool presenting a porous product face and one press tool presenting a less porous product face.

[0181] In this second pressing step 105a, a pressure lower than the surrounding ambient pressure is applied at a rear side of the porous wall portion, thus resulting in a vacuum at the rear side of the porous wall portion, causing solvent vapor, such as steam, to be drawn through the tool.

[0182] The porous wall portion of the porous press tool of the second pair of press tools may have a surface porosity of 25-50% with hole sizes 0.1-1.2 mm, preferably 0.25-1.0 mm.

[0183] However, in the second pressing step 105a, the pressure applied at the rear side of the porous wall portion may be higher than that provided in the first pressing step 103a.

[0184] In particular, the pressure provided in the first pressing step 103a may be 1-99% of that provided in the second pressing step 105a, preferably 50-99%, 90-99%, 95-99% or 99-99.9%.

[0185] In the second pressing step, the absolute pressure applied to the rear side of the product face of the porous tool may be 200-900 mbarA, preferably 300-800 mbarA, but always greater than in the first pressing step.

[0186] In the second pressing step, typically, all product faces contacting the pulp slurry layer may be heated.

[0187] The product face of the porous press tool of the second pair of press tools can be preheated by a radiation heater, as described in relation to FIG. 1a-1b, FIG. 1c-d, or FIG. 2a-2c, such that an initial pressing temperature of the product face of the porous press tool is about 100-300° C., preferably 150-250° C., and more preferably 160-240° C.

[0188] After the pressing, the temperature of the product face of porous press tool can be 25-75% of the initial pressing temperature.

[0189] Consequently, the step of heating the product face of the porous press tool can comprise inserting the radiation heater at a front side of the product face of the porous press tool, at a preset distance from the product face of the porous press tool and heating the product face to a preset temperature, by radiating heat from the radiation heater towards the product face. The heating step can further comprise withdrawing the radiation heater from the porous press tool.

[0190] Alternatively, the step of heating the product face of the porous press tool can comprise moving the porous press tool from a tool holder of the porous press tool to the radiation heater and heating the product face to a preset temperature, by radiating heat from the radiation heater towards the product face. The heating step can further comprise moving the porous press tool from the radiation heater to the tool holder.

[0191] The heating of the porous press tool of the second pair of press tools may be performed after step 103a and before step 105a.

[0192] As an alternative, at least two porous press tools can be provided for the second pair of cooperating press tools.

[0193] Consequently, at least one of the at least two porous press tools can be heated simultaneously 105b as another one is used for pressing in the corresponding pressing step 105a.

[0194] Then, in-between two subsequent pressing operations of the second pair of press tools, a change can be performed between the at least two porous press tools, such that one of the at least two porous press tool can be used in a first pressing operation and another one can be used in a second, subsequent pressing operation of the second pair of press tools.

[0195] Further, in the second pressing step 105a, the product face of the less porous press tool may be heated to about 200-500° C., preferably 300-400° C.

[0196] The product face of the less porous press tool may be heated to a higher temperature than the porous press tool.

[0197] The porous press tool may be heated to a temperature corresponding to 20-80% of the temperature of the less porous press tool, preferably 25-50%.

[0198] In the second pressing step 105a, a pressing pressure between the product faces of the second pair of press tools may be on the order of about 390-1570 kPa, and in most cases 580-1170 kPa.

[0199] The pressing pressure may be applied during a second pressing time of 0.1-4.0 second, preferably 0.5-2.0 second. In most settings, a pressing time on the order of 0.5-1.5 second is sufficient, and often also 0.5-1 second.

[0200] Typically, in this second pressing step, an initial water content of the pulp slurry layer may be about 45-65%, typically about 50-60% by weight.

[0201] A final water content may be about 25-40% by weight, preferably about 30-35% by weight.

[0202] After the second pressing step 105a, the pulp slurry layer, now with a substantial amount of its solvent removed, may be transferred 106 to a third pair of cooperating press tools. The transfer 106 may be performed in the same manner as the first transfer step 102 and/or the second transfer step 104, and with similar equipment. The third pair of press tools may be designed essentially as the first and/or second pair of press tools.

[0203] In a third pressing step 107a, the pulp slurry layer may be pressed between the third pair of press tools. At least one of the press tools may have a porous wall portion, which contacts the pulp slurry layer, and through which a vacuum can be drawn.

[0204] The third pair of cooperating press tools may comprise one press tool presenting a porous product face and one press tool presenting a less porous product face.

[0205] In this third pressing step 107a, a pressure lower than the surrounding ambient pressure is applied at a rear side of the porous wall portion, thus resulting in a vacuum at the rear side of the porous wall portion, causing solvent vapor, such as steam, to be drawn through the tool.

[0206] The porous wall portion of the porous tool of the third pair of press tools may have a surface porosity of 25-50% with hole sizes 0.1-1.2 mm, preferably 0.25-1.0 mm.

[0207] However, in the third pressing step 107a, the pressure applied at the rear side of the porous wall portion may be higher than that provided in the second pressing step 105a.

[0208] In particular, the pressure provided in the second pressing step 105a may be 1-99% of that provided in the third pressing step 107a, preferably 50-99%, 90-99%, 95-99% or 99-99.9%.

[0209] In the third pressing step, an absolute pressure provided at the rear of the porous wall portion of the porous press tool of the third pair of press tools may be 200-900 mbarA, preferably 300-800 mbarA, but always greater than in the second pressing step.

[0210] In the third pressing step, typically, all product faces contacting the pulp slurry layer are heated.

[0211] The product face of the porous press tool of the third pair of press tools can be preheated by a radiation heater, as described in relation to FIG. 1a-1b, FIG. 1c-d, or FIG. 2a-2c, such that an initial pressing temperature of the product face of the porous press tool is about 100-300° C., preferably 150-250° C., and more preferably 160-240° C.

[0212] After the pressing, the temperature of the product face of porous press tool can be 25-75% of the initial pressing temperature.

[0213] Consequently, the step of heating the product face of the porous press tool can comprise inserting the radiation heater at a front side of the product face of the porous press tool, a preset distance from the product face of the porous press tool and heating the product face to a preset temperature, by radiating heat from the radiation heater towards the product face. The heating step can further comprise withdrawing the radiation heater from the porous press tool.

[0214] Alternatively, the step of heating the product face of the porous press tool can comprise moving the porous press tool from a tool holder of the porous press tool to the radiation heater and heating the product face to a preset temperature, by radiating heat from the radiation heater towards the product face. The heating step can further comprise moving the porous press tool from the radiation heater to the tool holder.

[0215] The heating of the porous press tool by a radiation heater may be performed after step 105a and before step 107a.

[0216] As an alternative, at least two porous press tools can be provided for the third pair of cooperating press tools.

[0217] Consequently, at least one of the at least two porous press tools can be heated simultaneously 107b as another one is used for pressing in the corresponding pressing step 107a.

[0218] Then, in-between two subsequent pressing operations of the third pair of press tools, a change can be performed between the at least two porous press tools, such that one of the at least two porous press tool can be used in a first pressing operation and another one can be used in a second, subsequent pressing operation of the third pair of press tools.

[0219] Further, in the third pressing step 107a, the product face of the less porous press tool may be heated to about 200-500° C., preferably 300-400° C.

[0220] The product face of the less porous press tool may be heated to a higher temperature than the porous press tool.

[0221] The porous press tool may be heated to a temperature corresponding to 20-80% of the temperature of the less porous press tool, preferably 25-50%.

[0222] A pressing pressure between product faces of the third pair of press tools may be on the order of about 390-1570 kPa, and in most cases 580-1170 kPa.

[0223] The pressing pressure may be applied during a third pressing time of 0.1-4.0 second, preferably 0.5-2.0 second. In most settings, a pressing time on the order of 0.5-1.5 second is sufficient, and often also 0.5-1 second.

[0224] Typically, in this third pressing step, an initial water content of the pulp slurry layer may be about 25-45% or 25-40% by weight, preferably about 30-40% or 30-35% by weight, and a final water content may be less than about 5% by weight, preferably less than about 1% by weight.

[0225] After the third pressing step 107a, the pulp slurry layer, now with most of its solvent removed, may be transferred 108 out of the machine.

[0226] Optionally, additional steps, such as surface treatment, cutting or printing may be performed on the thus essentially dry product. The product may then be packaged, stored and shipped.

[0227] It is noted that the third pressing step 107a, and thus also its related transfer step 106, is optional. Hence, the process may be finished after the second pressing step 105a with the output step 108 following immediately.

[0228] Thus, in the first pressing step, an initial water content of the pulp slurry layer may be 70-90% by weight and a final water content may be 25-50% by weight, preferably about 30-35% by weight.

[0229] In the second pressing step, an initial water content of the pulp slurry layer may be about 25-50%, preferably about 30-35% by weight, and a final water content may be less than about 5% by weight, preferably less than about 1% by weight.

[0230] It is noted that the vacuum sources provided must be dimensioned so as to provide a flow that is sufficient to evacuate the amount of steam generated during the heating/pressing steps, and also to accommodate the liquid water that is drawn out by the vacuum applied to the respective pair of press tools.