Method and product forming unit for dry manufacturing rigid cellulose products

Abstract

The present invention relates to a method and a product forming unit for dry manufacturing rigid cellulose products (2) having essentially non-flat general shape from a cellulose blank. The product forming unit comprising a moulding tool having a first mould part (15) and a second mould part (16), wherein at least one of the first mould part (15) and the second mould part (16) is displaceable in the axial direction in relation to the other in order to press the cellulose blank therebetween into final shape by applying a predetermined pressure P in the axial direction of the moulding tool. The nominal distance (T) between the first mould part (15) and the second mould part (16) is in the range 0,3-2,0 millimetres. The first mould part (15) comprises a projection (30) that has a height (H) equal to or less than 15% of said nominal distance (T), in order to provide a debossing pattern (31) on the pressed cellulose product (2), and a recess (32) that has a depth (D) equal to or less than 15% of said nominal distance (T), in order to provide an embossing pattern (33) on the pressed cellulose product (2), wherein the essentially even principal surface (29) of the second mould part (16) is opposite said projection (30) and said recess (32) of the first mould part (15).

Description

Technical field of the Invention

[0001] The present invention relates in general to the field of method and apparatus for dry manufacturing of rigid cellulose products having essentially non-flat general shape from a cellulose blank. The cellulose products may be used for packaging, storing, transporting and / or displaying other products such as electronics, tools, jewelry, food, dairy products, cosmetics, etc., and / or may be used as single / multiple use disposable articles. The method and product forming unit are especially defined to provide rigid cellulose products having decorative and / or functional small-pattern on the pressed surface(s) of thinn cellulose products. The term cellulose products means products that mainly consists of the cellulose part of organic matter.

[0002] The present invention relates specifically to a product forming unit and a method for dry manufacturing rigid cellulose products, the product forming unit comprising a moulding tool having a first mould part and a second mould part, wherein at least one of the first mould part and the second mould part is displaceable in the axial direction in relation to the other in order to press the cellulose blank therebetween into final shape by applying a predetermined pressure P in the axial direction of the moulding tool, wherein the first mould part comprises a product press-surface having an essentially even principal surface and the second mould part comprises a product press-surface having an essentially even principal surface, and wherein a nominal distance (T) between the principal surface of the first mould part and the principal surface of the second mould part, when located in a press-position during pressing of the cellulose blank, is in the range 0,3-2,0 millimetres.Background of the Invention

[0003] There are many situations where it is desirable to provide two-dimensional (2D) or three-dimensional (3D) shaped objects made of sustainable materials, such as biomaterials, instead of using plastic / polymer materials. A biomaterial commonly used for packaging and disposable articles is wet moulded pulp based on cellulose fibres. Such wet moulded pulp has the advantage of being considered as a sustainable material, since it is produced from biomaterials and can be recycled after use. Wet moulded pulp comprises more or less only water and separated cellulose fibers, and consequently, wet moulded pulp has been popular to use for primary packaging applications (packaging next to the article), for secondary packaging applications (assembly of such primary packages), as well as for manufacturing of disposable articles / products.

[0004] One advantage of using wet-forming techniques is that the moulding tool is usually made of a wire netting / cloth that is filled with a wet cellulose slurry and thereafter the cellulose slurry is dried and obtains the general shape of the moulding tool.

[0005] However, a common disadvantage with all wet-forming techniques is the need for large amounts of water during the preparations of the cellulose pulp and the need for drying during the manufacturing / moulding of the cellulose product, which is a time and energy consuming step leading to low production speed and substantial high investment cost in machines and tooling. Meaning that the wet-forming techniques are not feasible to replace fossil-based alternatives neither in small nor large scale production of rigid cellulose products. Thereto, the aesthetical and mechanical properties of a wet-moulded cellulose product are hard to control with desirable precision, due to un-uniform cellulose pulp and due to the wet moulding manufacturing technique per se. Thus, the cellulose product obtains a debossing pattern from the wire netting / cloth on the entire surface of one of the sides of the cellulose product, and the opposite side of the cellulose product is quite rough and un-even.

[0006] Therefore many actors / companies, starting a few decades ago, have changed their focus and investments towards dry-forming techniques wherein rigid cellulose products are manufactured from separated cellulose fibres that are introduced into a product forming unit in the shape of a cellulose blank / web, wherein the cellulose blank is moulded / formed into the shape of the intended cellulose product and wherein the cellulose fibres are bonded to each other using heat and pressure. The dry-forming techniques comprises different steps of generating an air-laid cellulose blank, that is fed into a product forming unit, i.e. a thermo-forming press.

[0007] The technical field of dry manufacturing rigid cellulose products having non-flat general shape, such as trays, lids, or the like, i.e. wherein the forming / pressing is performed in one step using a moulding tool having a first mould part and a second mould part configured to cooperate with each other, is well known. However, the technical field of dry manufacturing rigid cellulose products having non-flat general shape and decorative and / or functional small-pattern on the pressed surface(s) of thin cellulose products, such as trays, plates, cups, packaging, or the like, is still exposed to challenges.

[0008] During moulding / pressing of the rigid cellulose product having essentially non-flat general shape from cellulose blank, there is a correlation between the pressing force and the material characteristics of the pressed cellulose product. On the one hand, a too high pressing force entails that the pressed cellulose product will become brittle / plastic and thereto the final cellulose product obtains a yellow tone, i.e. too high density. On the other hand, a too low pressing force entails that the pressed cellulose product becomes insufficiently moulded, i.e. the internal bonding between the cellulose fibres becomes inadequate, and there will be a great degree of fibre release from the surfaces, i.e. too low density. The applied pressure and the surface weight of the cellulose blank, provides a nominal thickness of the pressed cellulose product having an optimal density.

[0009] Thus, in order to provide pattern on the surface(s) of pressed cellulose product, the male mould part and the female mould part has to have co-operating design, i.e. one of the mould parts comprises a local projection and the other mould part comprises a local recess, in order to obtain the nominal thickness and thereby the correct material characteristics over the entire cellulose product. However, there is an obvious drawback that the pattern has to be wide / broad enough such that the projection and the recess of the mould parts may cooperate.

[0010] Known attempts to provide decorative and / or functional small-pattern on the surfaces of pressed cellulose products, i.e. pattern having less width and / or pattern appearing only on one side of the cellulose product, has not been successful since they are subject to the above-mentioned drawbacks due to too high local press force or too low local press force. The pattern becomes yellow and brittle, or suffer from fibre release, i.e. the appearance and material characteristics of the pressed cellulose product is not satisfactory.

[0011] Thus, there is still a need in the art for a reliable, cheap and unharmful dry-forming technique / process for dry manufacturing rigid cellulose products having non-flat general shape and a considerable depth.Object of the Invention

[0012] The present invention aims at obviating the aforementioned and other disadvantages and failings of previously known methods and devices for dry manufacturing rigid cellulose products, and at providing an improved method and product forming unit for dry manufacturing rigid cellulose products having non-flat general shape and decorative and / or functional small-pattern.

[0013] A primary object of the present invention is to provide an improved product forming unit and method for dry forming / manufacturing rigid cellulose products having non-flat general shape and decorative and / or functional small-pattern, wherein the environmental benefits as well as time and energy saving benefits of conventional dry-forming techniques are maintained. It is another object of the present invention to provide an improved product forming unit and method for dry forming / manufacturing rigid cellulose products having non-flat general shape, wherein the pressed cellulose product has uniform material characteristics.Summary of the Invention

[0014] According to the invention at least the primary object is attained by means of the initially defined product forming unit and method having the features defined in the independent claim. Preferred embodiments of the present invention are further defined in the dependent claims. According to a first aspect of the present invention, there is provided a product forming unit of the initially defined type, wherein the first mould part comprises: a projection that is provided to the essentially even principal surface and has a height (H) in relation to surrounding parts of the principal surface of the first mould part that is equal to or less than 15% of said nominal distance (T) between the principal surface of the first mould part and the principal surface of the second mould part, in order to provide a debossing pattern on the pressed cellulose product, and a recess that is provided to the essentially even principal surface and has a depth (D) in relation to surrounding parts of the principal surface of the first mould part that is equal to or less than 15% of said nominal distance (T) between the principal surface of the first mould part and the principal surface of the second mould part, in order to provide an embossing pattern on the pressed cellulose product, wherein the essentially even principal surface of the second mould part is opposite said projection and said recess of the first mould part.

[0015] According to a second aspect of the present invention, there is provided a method for dry manufacturing rigid cellulose products having essentially non-flat general shape from a cellulose blank using a product forming unit as defined herein above, wherein the method comprises the steps of: providing the cellulose blank into the moulding tool between the first mould part and the second mould part, displacing at least one of the first mould part and the second mould part in the axial direction towards each other, wherein a nominal distance (T) between the principal surface of the first mould part and the principal surface of the second mould part, when located in a press-position during pressing of the cellulose blank, is in the range 0,3-2 millimetres, and providing a debossing pattern on the pressed cellulose product during the pressing of the cellulose product by means of the projection of the first mould part, and providing an embossing pattern on the pressed cellulose product during the pressing of the cellulose product by means of the recess of the first mould part.

[0016] Thus, the present invention is based on the insight that the height and depth of the pattern in relation to the principal surface of the pressed cellulose product may only differ up to 15% of the nominal thickness of the pressed cellulose product, in order not to suffer from fibre release and yellow tone, respectively. Thus, the inventor has realized that there is a correlation between the nominal thickness of the pressed cellulose product and the possible height and depth of the pattern. These findings are based on the understanding that there is an optimal density of all pressed cellulose products within the current / given range of nominal thickness, and different surface weights of the cellulose blanks will thereby provide different nominal thickness of the pressed cellulose products. Thereby, by having both projections and recesses on one of the mould parts the total amplitude of the final pattern of the pressed cellulose product may be twice as high compared to only having debossing or embossing, without suffering from fibre release and / or yellow tone.

[0017] According to various example embodiments of the present invention, the height (H) of the projection is equal to or more than 0,02 millimetres, and / or, the depth (D) of the recess is equal to or more than 0,02 millimetres. Thus, less height or less depth will not be perceived and may be said as unintentional and / or only part of the general surface roughness of the pressed cellulose product.

[0018] According to various example embodiments of the present invention, said predetermined pressure P used during pressing of the cellulose blank is configured to generate a density of the pressed cellulose product that is equal to or more than 1035 kg / m 3< and equal to or less than 1265 kg / m 3< . Thereby, the pressed cellulose product will not suffer from yellow tone and / or fibre release.

[0019] According to various example embodiments of the present invention, the height (H) of the projection of the first mould part is equal to or less than the smaller of 15% of the nominal distance (T) and 0,2 millimetres, and / or, the depth (D) of the recess of the first mould part is equal to or less than the smaller of 15% of the nominal distance (T) and 0,2 millimetres. Thus, for cellulose products having a thickness in the upper region of the given thickness range, the maximum height and depth of the pattern is given by a specific metric dimension instead of a percentage.

[0020] Further advantages with and features of the invention will be apparent from the following detailed description of preferred embodiments.Brief description of the drawings

[0021] A more complete understanding of the abovementioned and other features and advantages of the present invention will be apparent from the following detailed description of preferred embodiments in conjunction with the appended drawings, wherein: Fig. 1is a schematic illustration of a production line or apparatus for dry manufacturing rigid cellulose products, Fig. 2is a schematic illustration of a moulding tool, wherein a cellulose blank is provided into the moulding tool between the first / female mould part and the second / male mould part, Fig. 3is a schematic illustration of the moulding tool according to figure 2 during forming / pressing of the cellulose product, Fig. 4is a schematic illustration of the moulding tool according to figures 2 and 3 after the forming / pressing step and the pressed cellulose product is removed from the moulding tool, Fig. 5is a schematic illustration of the moulding tool according to figures 2-4, the pressed cellulose product being removed from the moulding tool, Fig. 6is a schematic enlargement of the first / female mould part disclosed in figures 2-4, and Fig. 7is a schematic enlargement of a second / male mould part. Detailed description of preferred embodiments of the invention

[0022] As used herein, the term "air / dry moulding / forming or air / dry laying / laid" means a well-known method according to which separated cellulose fibres are formed into a cellulose blank / sheet.

[0023] In air-laying technique, small / short fibres having a normal length in the range of 0,5 to 70 mm, for instance 1 to 50 mm, are separated and captured by an air stream / flow, and then laid on / applied to a forming mesh / surface, usually using an under-pressure at the other side of the mesh / surface. The general terms "air / dry laying" and "air / dry moulding" are used interchangeably herein. The cellulose fibre carrying air flow may be generated by suitable device located upstream and / or downstream the forming mesh / surface.

[0024] Reference is initially made to figures 1 and 5, wherein figure 1 disclose a schematic illustration of a generic production line / apparatus, generally designated 1, for dry manufacturing rigid cellulose products. The production line 1 is configured for manufacturing rigid cellulose products, generally designated 2, having essentially non-flat general shape from separated cellulose fibres. Such a production line / apparatus 1 may be arranged and set-up according to different well-known ways. Figure 5 disclose an example of a rigid cellulose product / tray 2. The apparatus 1 may have automatic transfer / handling between the different process steps, and / or may have manual transfer / handling between the different process steps, and thereto the apparatus 1 may have intermediate storing and / or additional process steps between the disclosed process steps, and / or the process steps may be located at different sites.

[0025] Figure 5 disclose one example of a rigid cellulose product 2 constituted by a rectangular container / tray, wherein the tray is formed using the inventive method. The cellulose product 2 comprises an inclined circumferential wall 3 and an opening 4 defined by a circumferential rim / brim 5 connected to the upper / free end of the wall 3. According to figure 5 embodiment the brim 5 has an angled shape having an essentially radially extending upper surface and a turned-down outer edge, however it shall be pointed out that the cross-section of the brim 5 may have other shapes. The tray 2 may have truncated cone shape having straight wall 3, narrowing in the direction away from the opening 4, in accordance with figure 5 embodiment. The tray 2 may for instance have curved-shaped wall 3 seen in the axial plane. By having inclined walls 3 multiple trays 2 are stackable one inside the other when they are empty. The tray could also be a mug / cup, a lid, packaging or the like container / product. The cross section of the wall 3 in the radial plane may have any suitable shape, circular, oval, rectangular, polygonal, etc., and may differ in shape and / or dimension along the axial extension of the tray 2. The tray 2 may comprise a bottom 6, wherein the bottom 6 is entirely flat or the bottom may comprise local ribs, projections, etc., for strength and rigidity of the cellulose product. The bottom 6 may be located at the very lower end of the wall 3, according to figure 5 embodiment, and / or be partly located at a distance from the lower end of the wall 3, or a combination thereof. The circumferential wall 3 is connected to and extends in the axial direction upwards from the bottom portion 6.

[0026] Cellulose raw material 7, i.e. comprising mainly the cellulose part of organic matter, is provided to the production line, and is fed to a separating / disintegrating unit 8 in order to obtain individualized / separated cellulose fibres. The separated cellulose fibres are thereafter transported by an air stream / flow to a dispenser of a cellulose blank / sheet forming unit 9. The cellulose fibres are laid by the dispenser on a moving or stationary perforated surface of the cellulose blank forming unit 9. The cellulose fibre carrying air flow may be generated by suitable device located upstream and / or downstream the perforated surface. Thereafter the generated cellulose blank, generally designated 10, is transported / transferred to a product forming unit 11, whereby rigid cellulose products 2 are formed and discharged from the product forming unit 11.

[0027] The cellulose blank forming unit 9 may be configured to generate a continuous cellulose blank 10 and / or discontinuous / discrete cellulose blanks 10. Preferably discontinuous / discrete cellulose blanks 10 are fed into the product forming unit 11.

[0028] The cellulose raw material 7 may be in the form of reeled pulp or paper, bale of cellulose pulp, paper, etc. and / or sheets of paper, cellulose pulp, etc. In case said cellulose raw material 7 is in the form of sheets and / or reeled pulp or paper, it can be fed directly into the separating unit 8. However, in case said cellulose raw material 7 is in the form of a bale or compact stacks of sheets, etc. one or more shredders and / or one or more additional separating / disintegrating units 8 may be necessary to be used for separating and dosing said cellulose raw material 7 from said bale or sheets in smaller quantities. The shredder(s) prepare cellulose raw material 7 to be accepted by said separating unit 8. The separating unit 8 disintegrates the cellulose raw material 7 into separated cellulose fibres. Said one or plurality of shredder(s) are arranged before said one or a plurality of separating unit(s) 8, so that an output of one of said shredder is connected to an input of one of said separating units 8. The shredders may be arranged in parallel to each other or in series with each other, and the disintegrating units 8 may be arranged in parallel to each other or in series with each other. The shredders and the disintegrating units 8 together constitute a cellulose fibre separating unit, arranged upstream the cellulose blank forming unit 9.

[0029] Said cellulose raw material 7 may be constituted by virgin cellulose fibres and / or recycled cellulose fibres and may originate from wood pulps such as kraft pulp, sulphite pulp, mechanical pulp, thermomechanical pulp (TMP), chemical treated mechanical pulp, chemi-thermomechanical pulp (CTMP), and / or from non-wood pulps such as bagasse, bamboo, abaca, hemp, flax, cotton.

[0030] The separating unit 8 may according to various embodiments be constituted by a hammer mill. In said separating unit 8 the cellulose raw material is separated into fibres having a normal length in the range of 0,5-70 mm, preferably less than 10 mm. The length of said fibres may be customized by adjusting the internal properties of the separating unit 8 and / or by choosing a different separating unit 8 and / or choosing different cellulose raw material 7. The fibre length for wood pulp is according to various embodiments in the range 0,5-4 mm, preferably in the range 1,7-3,6 mm. According to various embodiments the fibre length for non-wood pulp is in the range 0,5-70 mm.

[0031] The production line 1 may comprise a pre-compression and / or imprinting unit 12, located downstream the cellulose blank forming unit 9 and upstream the product forming unit 11. In the pre-compression and / or imprinting unit 12, an air-laid fluffy cellulose blank 10 having a first thickness may be compressed into a cellulose blank 10 having a second thickness, wherein said second thickness is thinner than said first thickness, and / or may be provided with an imprinting pattern. During the pre-compression / imprinting the cellulose blank is made more coherent and easier to handle, since the pre-compression / imprinting generates internal bindings between individual cellulose fibres preventing mutual separation of the cellulose fibres.

[0032] The product forming unit 11 comprises a press unit 13, and may optionally comprise a pre-heating unit 14 arranged upstream the press unit 13. According to various example embodiments said cellulose blank 10 may be heated to an elevated temperature before being fed into the press unit 13 of the product forming unit 11. In such embodiment(s) where the cellulose blank 10 is preheated before being fed into the press unit 13, said press unit 13 may or may not comprise heating. According to various example embodiment said press unit 13 may be a heated press unit 13 for heating said cellulose blank 10 during pressing. In the case of a heated press unit 13, preheating of said cellulose blank 10 using a pre-heating unit 14 is optional. According to various example embodiments preheating of the cellulose blank 10 in said pre-heating unit 14 may be combined with a heated press unit 13. Having a pre-heating unit 14 in combination with a heated press unit 13 will speed up the manufacturing process in the product forming unit 11, and improve the quality / rigidity of the final rigid cellulose product 2. In the product forming unit 11 the cellulose blank 10 is heated to a temperature in the range 120 - 200 °C in order to obtain adequate rigidity and strength in the final cellulose product 2.

[0033] Reference is now made to figures 2-4, disclosing an example embodiment of the present invention. The press unit 13 comprises a moulding tool having a first mould part 15 and a second mould part 16 having co-operating designs, wherein at least one of the first mould part 15 and the second mould part 16 is / are displaceable in the axial direction in relation to the other, i.e. reciprocating back and forth in relation to each other, in order to exert pressure to the cellulose blank 10 loaded therebetween. In the figures the mutual displacement is disclosed as being vertical, however the mutual displacement may be horizontal or any other suitable angle. The cellulose blank 10 loaded into the moulding tool, is preferably constituted by an air-laid cellulose blank. The cellulose blank 10 may be generated upstream the product forming unit 11 in the same apparatus / production line and provided / transferred to the product forming unit 11, or may be generated at a separate location and provided / transferred to the product forming unit 11 via intermediate handling and storage.

[0034] According to the disclosed example embodiment, the first mould part 15 of the moulding tool is a female mould part, i.e. having a main recess 17 for receiving a major part of the cellulose blank 10, and the second mould part 16 of the moulding tool is a male mould part, i.e. having a main protrusion 18 for cooperation with said recess 17 of the female mould part by being inserted therein, such that the cellulose blank 10 is pressed into a final rigid non-flat shape by applying a predetermined pressure P in the axial direction of the moulding tool. According to the disclosed first embodiment of figures 2-4 the male / second mould part 16 is located above the female / first mould part 15, i.e. the pressed cellulose product 2 is intended to be collected from the female / first mould part 15 after the pressing of the cellulose blank 10. However, according to an alternative to the first embodiment the female / first mould part 15 may be located above the male / second mould part 16, i.e. the pressed cellulose product 2 is intended to be collected from the male / second mould part 15 after the pressing of the cellulose blank 10. According to various embodiments, the first mould part is constituted by a male mould part and the second mould part is constituted by a female mould part.

[0035] The second mould part 16 comprises a product press-surface and a scrap press-surface 19 adjacent said product press-surface. In the disclosed example embodiment, the product press-surface of the second mould part 16 comprises a bottom surface 20, a wall surface 21 connected to the bottom surface 20 and extending essentially in the axial direction, and a brim surface 22 connected to the wall surface 21 and extending essentially in the transversal / radial direction. According to various embodiments, the scrap press-surface 19 of the second mould part 16 surrounds the entire product press-surface. According to other embodiments, the scrap press-surface 19 of the second mould part 16 is only located at some locations around the product press-surface. The first mould part 15 comprises a product press-surface and a scrap press-surface 23 adjacent said product press-surface. In the disclosed example embodiment, the product press-surface of the first mould part 15 comprises a bottom surface 24, a wall surface 25 connected to the bottom surface 24 and extending essentially in the axial direction, and a brim surface 26 connected to the wall surface 25 and extending essentially in the transversal / radial direction. According to various embodiments, the scrap press-surface 23 of the first mould part 15 surrounds the entire product press-surface. According to other embodiments, the scrap press-surface 23 of the first mould part 15 is only located at some locations around the product press-surface.

[0036] According to various embodiments, some moulding tools does not comprise scrap press-surfaces, but the cellulose product 2 is formed in its final design without need for cutting / trimming.

[0037] The scrap press-surface 23 of the first mould part 15 is arranged opposite the scrap press-surface 19 of the second mould part 16, and the product press-surface of the first mould part 15 is arranged opposite the product press-surface of the second mould part 16.

[0038] The cellulose blank 10 is pressed between the surfaces of the male / second mould part 16 and the surfaces of the female / first mould part 15 into final shape. The mutual distance, taken perpendicular to the surface in question, between the product press-surface of the female / first mould part 15 and the product press-surface of the male / second mould part 16 during the pressing of the cellulose blank 10 is T millimetres, wherein T preferably is in the range 0,3-2,0 millimetres, i.e. equal to the thickness of the bottom 6 of the pressed cellulose product 2. Preferably T is in the range 0,3-1,5 millimetres, and most preferably below 1,0 millimetres in order to save raw material. The wall surfaces 21, 25 of the moulding tool has to be inclined in order to obtain a release angle for the cellulose product, and in order to obtain adequate press force to the wall region 3 of the cellulose product 2.

[0039] At the scrap area of the moulding tool, the mutual distance between the scrap press-surface 23 of the first mould part 15 and the scrap press-surface 19 of the second mould part 16 is equal to or more than the mutual distance between the product press-surface of the first mould part 15 and the product press-surface of the second mould part 16. The part of the cellulose blank 10 located at the scrap area may be left entirely uncompressed in the moulding tool, be partially compressed by applying a predetermined partial pressure less than said predetermined pressure P, or be fully compressed by applying said predetermined pressure P. Thus, radially outside the final rigid cellulose product 2, the cellulose blank 10 comprises a scrap area intended to be cut off. In figure 4 the cellulose product 2 is released and schematically removed from the moulding tool by opening the moulding tool. Figure 5 disclose a schematic illustration of a cellulose tray 2 wherein the scrap 27 is cut off from the cellulose tray 2. According to various embodiments, the scrap 27 may be removed in a separate step in the moulding tool, in a subsequent step outside the moulding tool after the pressing of the cellulose blank 10, or in a step concurrent with the pressing of the cellulose blank 10.

[0040] According to various embodiments. When the compartment of the rigid cellulose tray 2 is filled with objects, a film / cover / lid may be attached to the circumferential rim / brim 5 of the cellulose tray 2, for instance using heat lamination. The lid film may be constituted by a multilayer film comprising polymer, metal, and / or paper.

[0041] According to various embodiments. Before any items are placed in the compartment of the rigid cellulose tray, the rigid cellulose tray 2 may be provided with a liner film adhered to at least to the circumferential rim / brim 5, and preferably also to the wall 3 and / or the bottom 6 of the cellulose tray 2. The liner film may be constituted by a multilayer film comprising polymer and / or metal. The adhesion of the liner film to the tray is preferably heat activated.

[0042] According to various embodiments, the cellulose blank 10 may comprise barrier additives and / or material property enhancing additives, etc., such that the rigid cellulose tray 2 withstand grease, fat, water, vapour, etc. The additives are preferably provided to the cellulose fibers upstream the disintegrating unit 8 or between the disintegrating unit 8 and the product forming unit 11.

[0043] The predetermined pressure P is in the range 40-10000N / cm 2< , preferably in the range 100-4000N / cm 2< . According to various embodiments said predetermined pressures are above 1000 N / cm 2< , and according to various embodiments said predetermined pressures are below 2500 N / cm 2< . The holding time during the pressing step is in equal to or more than 0,5 seconds and equal to or less than 10 seconds, preferably less than 5 seconds, and most preferably less than 3 seconds.

[0044] Reference is now especially made to figure 6 disclosing a first schematic embodiment of the present invention, wherein the female mould part is the first mould part 15, and to figure 7 disclosing a second schematic embodiment of the present invention, wherein the male mould part is the first mould part 15. The figures are not drawn to scale.

[0045] The product press-surface of the first mould part 15 has an essentially even / smooth principal / main surface 28 and the product press-surface of the second mould part 16 has an essentially even / smooth principal / main surface 29. Thus, the principal surfaces 28, 29 of the two mould parts are appropriately machined / polished in order to obtain the requested surface roughness / smoothness of the pressed cellulose product 2. Thus, the principal surfaces 28, 29 of the mould parts does not need to be a flat surface, but may as well be a single curved or double curved surface. As described above, the nominal distance (T) between the principal surface 28 of the first mould part 15 and the principal surface 29 of the second mould part 16, when located in a press-position during pressing of the cellulose blank 10, is in the range 0,3-2,0 millimetres, preferably in the range 0,3-1,5 millimetres, and most preferably less than 1,0 millimetres. Thus, the thickness of the pressed cellulose product 2 is equal to said nominal distance (T), and it is preferred to have as thin cellulose product 2 as possible in order to save cellulose raw material, as long as the mechanical characteristics of the cellulose product 2 are fulfilled.

[0046] The first mould part 15 comprise at least one projection 30 that is provided to the principal surface 28 and has a height (H) measured in relation to the surrounding parts of the principal surface 28 of the first mould part 15. The height (H) of the at least one projection 30 is equal to or less than 15% of the nominal distance (T) between the principal surface 28 of the first mould part 15 and the principal surface 29 of the second mould part 16, when located in a press-position during pressing of the cellulose blank 10. During pressing of the cellulose blank 10, said at least one projection 30 provides a debossing pattern 31 on the pressed cellulose product 2. Thus, the depth of the debossing is equal to or less than 15% of the nominal thickness (T) of the pressed cellulose product 2. Thereby, it is secured that the cellulose product 2 is not over-pressed at the location of the debossing pattern 31. Preferably, the height (H) of the at least one projection 30 is equal to or less than 10% of the nominal distance (T) between the principal surface 28 of the first mould part 15 and the principal surface 29 of the second mould part 16. Thereby, it is by margin secured that the cellulose product 2 is not over-pressed at the location of the debossing pattern 31.

[0047] Thereto, the first mould part 15 comprise at least one recess 32 that is provided to the principal surface 28 and has a depth (D) measured in relation to the surrounding parts of the principal surface 28 of the first mould part 15. The depth (D) of the at least one recess 32 is equal to or less than 15% of the nominal distance (T) between the principal surface 28 of the first mould part 15 and the principal surface 29 of the second mould part 16, when located in a press-position during pressing of the cellulose blank 10. During pressing of the cellulose blank 10, said at least one recess 32 provides an embossing pattern 33 on the pressed cellulose product 2. Thus, the height of the embossing is equal to or less than 15% of the nominal thickness (T) of the pressed cellulose product 2. Thereby, it is secured that the cellulose product 2 is not under-pressed at the location of the embossing pattern 33. Preferably, the depth (D) of the at least one recess 32 is equal to or less than 10% of the nominal distance (T) between the principal surface 28 of the first mould part 15 and the principal surface 29 of the second mould part 16. Thereby, it is by margin secured that the cellulose product 2 is not under-pressed at the location of the embossing pattern 33.

[0048] Thus, although each of the debossing pattern 31 and the embossing pattern 33 is small, the total pattern on the pressed cellulose product 2 has the amplitude of the sum of the height (H) of the debossing pattern 31 and the depth (D) of the embossing pattern 33, at the same time as optimal pressing of the cellulose product 2 is provided also at the locations of the total pattern. The total pattern may be decorative / figurative and / or functional / informative.

[0049] According to the invention, the essentially even principal surface 29 of the second mould part 16 is opposite said projection 30 of the first mould part 15 and opposite said recess 32 of the first mould part 15. Thus, the total pattern is provided by the projection 30 and recess 32 as such, without any corresponding design features on the second mould part 16.

[0050] According to figure 6 embodiment, i.e. the first mould part 15 is a female mould part, the debossing pattern 31 and the embossing pattern 33 of the cellulose product 2 are located on the lower side of the bottom 6 of the cellulose product 2. According to figure 7 embodiment, i.e. the first mould part 15 is a male mould part, the debossing pattern 31 and the embossing pattern 33 of the cellulose product 2 are located on the upper side of the bottom 5 of the cellulose product 2.

[0051] According to various embodiments, the height (H) of the at least one projection 30 is equal to or more than 0,02 millimetres. This will result in a debossing pattern 31 that is visible by the naked eye, and provides a clear and distinct difference in relation to general surface roughness of the principal surface 28 of the first mould part 15.

[0052] According to various embodiments, the depth (D) of the at least one recess 32 is equal to or more than 0,02 millimetres. This will result in an embossing pattern 33 that is visible by the naked eye, and provides a clear and distinct difference in relation to general surface roughness of the principal surface 28 of the first mould part 15.

[0053] The nominal thickness (T) of the pressed cellulose product 2 is related to the grammage of the cellulose blank 10 and the predetermined pressure P used during pressing of the cellulose blank 10. According to various embodiments, irrespective the grammage of the cellulose blank 10, the predetermined pressure P used during pressing of the cellulose blank 10 is configured to generate a density of the pressed cellulose product 2 that is equal to or more than 1035 kg / m 3< and equal to or less than 1265 kg / m 3< . Thereby it is secured that no part of the cellulose product 2 is over-pressed or under-pressed, including the debossing pattern 31 and the embossing pattern 33 generated by the projection 30 and recess 32 of the first mould part 15.

[0054] Preferably the generated density of the pressed cellulose product 2 is equal to or more than 1100 kg / m 3< and equal to or less than 1200 kg / m 3< , and the target density is 1150 kg / m 3< . Thereby, it is by margin secured that no part of the cellulose product 2 is over-pressed or under-pressed, including the debossing pattern 31 and the embossing pattern 33 generated by the projection 30 and recess 32 of the first mould part 15.

[0055] According to various embodiments, the principal surface 28 of the first mould part 15 is made of metal and the principal surface 29 of the second mould part 16 is made of an elastic material, such as rubber. According to other various embodiments, both the principal surface 28 of the first mould part 15 and the principal surface 29 of the second mould part 16 are made of metal.

[0056] According to various embodiments, at least 50 % of the product press-surface of the first mould part 15 is constituted by the principal / main surface 28, i.e. free from projections 30 and recesses 32.

[0057] According to various embodiments, the principal surface 28 of the first mould part 15 is located between and separates the projection 30 of the first mould part 15 and the recess 32 of the first mould part 15, i.e. the debossing pattern 31 and the embossing pattern 33 are not directly adjacent each other.

[0058] According to various embodiments, the height (H) of the at least one projection 30 of the first mould part 15 is equal to or less than the smaller of 15% of the nominal distance (T) and 0,2 millimetres. Thus, when the nominal thickness (T) of the pressed cellulose product 2 is in the upper region of the range, the height (H) of the at least one projection 30 is delimited to 0,2 millimetres, in order to secure that the cellulose product 2 is not over-pressed at the location of the debossing pattern 31.

[0059] According to various embodiments, the depth (D) of the at least one recess 32 of the first mould part 15 is equal to or less than the smaller of 15% of the nominal distance (T) and 0,2 millimetres. Thus, when the nominal thickness (T) of the pressed cellulose product 2 is in the upper region of the range, the depth (D) of the at least one recess 32 is delimited to 0,2 millimetres, in order to secure that the cellulose product 2 is not under-pressed at the location of the embossing pattern 33.

[0060] According to various embodiments, non-disclosed, also the second mould part 16 comprises at least one projection and / or at least one recess provided to the principal surface 29 of the second mould part 16. In such embodiments, the essentially even principal surface 28 of the first mould part 15 is opposite such projections of the second mould part 16 and / or opposite such recesses of the second mould part 16. Such projections and recesses of the second mould part 16 are configured in accordance with the projections 30 and recesses 32 of the first mould part 15.

[0061] Thus, according to the inventive method for dry manufacturing rigid cellulose products 2 having essentially non-flat general shape from a cellulose blank 10, using a product forming unit 11 comprising a moulding tool according to the above, the method comprising the steps of: providing the cellulose blank 10 into the moulding tool between the first mould part 15 and the second mould part 16, displacing at least one of the first mould part 15 and the second mould part 16 in the axial direction towards each other, wherein a nominal distance (T) between the principal surface 28 of the first mould part 15 and the principal surface 29 of the second mould part 16, when located in a press-position during pressing of the cellulose blank 10, is in the range 0,3-2 millimetres, and providing a debossing pattern 31 on the pressed cellulose product 2 during the pressing of the cellulose product 2 by means of the projection 30 of the first mould part 15, and providing an embossing pattern 33 on the pressed cellulose product 2 during the pressing of the cellulose product 2 by means of the recess 32 of the first mould part 15.

[0062] Preferably the method comprises the steps of: displacing at least one of the second mould part 16 and the first mould part 15 in the axial direction away from each other, and removing the pressed cellulose product 2 from the moulding tool. Feasible modifications of the Invention

[0063] The invention is not limited only to the embodiments described above and shown in the drawings, which primarily have an illustrative and exemplifying purpose. This patent application is intended to cover all adjustments and variants of the preferred embodiments described herein, thus the present invention is defined by the wording of the appended claims and the equivalents thereof. Thus, the equipment may be modified in all kinds of ways within the scope of the appended claims.

[0064] Throughout this specification and the claims which follows, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or steps or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0065] It shall also be pointed out that it shall be considered understood that features from a specific embodiment disclosed herein can be combined with and / or exchanged by features from another embodiment and the combination obvious, even though not expressly taught, when the combination and / or exchange is possible.

Examples

Embodiment Construction

[0022]As used herein, the term "air / dry moulding / forming or air / dry laying / laid" means a well-known method according to which separated cellulose fibres are formed into a cellulose blank / sheet.

[0023]In air-laying technique, small / short fibres having a normal length in the range of 0,5 to 70 mm, for instance 1 to 50 mm, are separated and captured by an air stream / flow, and then laid on / applied to a forming mesh / surface, usually using an under-pressure at the other side of the mesh / surface. The general terms "air / dry laying" and "air / dry moulding" are used interchangeably herein. The cellulose fibre carrying air flow may be generated by suitable device located upstream and / or downstream the forming mesh / surface.

[0024]Reference is initially made to figures 1 and 5, wherein figure 1 disclose a schematic illustration of a generic production line / apparatus, generally designated 1, for dry manufacturing rigid cellulose products. The production line 1 is configured for manufacturing rigid c...

Technical field of the Invention

[0001] The present invention relates in general to the field of method and apparatus for dry manufacturing of rigid cellulose products having essentially non-flat general shape from a cellulose blank. The cellulose products may be used for packaging, storing, transporting and / or displaying other products such as electronics, tools, jewelry, food, dairy products, cosmetics, etc., and / or may be used as single / multiple use disposable articles. The method and product forming unit are especially defined to provide rigid cellulose products having decorative and / or functional small-pattern on the pressed surface(s) of thinn cellulose products. The term cellulose products means products that mainly consists of the cellulose part of organic matter.

[0002] The present invention relates specifically to a product forming unit and a method for dry manufacturing rigid cellulose products, the product forming unit comprising a moulding tool having a first mould part and a second mould part, wherein at least one of the first mould part and the second mould part is displaceable in the axial direction in relation to the other in order to press the cellulose blank therebetween into final shape by applying a predetermined pressure P in the axial direction of the moulding tool, wherein the first mould part comprises a product press-surface having an essentially even principal surface and the second mould part comprises a product press-surface having an essentially even principal surface, and wherein a nominal distance (T) between the principal surface of the first mould part and the principal surface of the second mould part, when located in a press-position during pressing of the cellulose blank, is in the range 0,3-2,0 millimetres.Background of the Invention

[0003] There are many situations where it is desirable to provide two-dimensional (2D) or three-dimensional (3D) shaped objects made of sustainable materials, such as biomaterials, instead of using plastic / polymer materials. A biomaterial commonly used for packaging and disposable articles is wet moulded pulp based on cellulose fibres. Such wet moulded pulp has the advantage of being considered as a sustainable material, since it is produced from biomaterials and can be recycled after use. Wet moulded pulp comprises more or less only water and separated cellulose fibers, and consequently, wet moulded pulp has been popular to use for primary packaging applications (packaging next to the article), for secondary packaging applications (assembly of such primary packages), as well as for manufacturing of disposable articles / products.

[0004] One advantage of using wet-forming techniques is that the moulding tool is usually made of a wire netting / cloth that is filled with a wet cellulose slurry and thereafter the cellulose slurry is dried and obtains the general shape of the moulding tool.

[0005] However, a common disadvantage with all wet-forming techniques is the need for large amounts of water during the preparations of the cellulose pulp and the need for drying during the manufacturing / moulding of the cellulose product, which is a time and energy consuming step leading to low production speed and substantial high investment cost in machines and tooling. Meaning that the wet-forming techniques are not feasible to replace fossil-based alternatives neither in small nor large scale production of rigid cellulose products. Thereto, the aesthetical and mechanical properties of a wet-moulded cellulose product are hard to control with desirable precision, due to un-uniform cellulose pulp and due to the wet moulding manufacturing technique per se. Thus, the cellulose product obtains a debossing pattern from the wire netting / cloth on the entire surface of one of the sides of the cellulose product, and the opposite side of the cellulose product is quite rough and un-even.

[0006] Therefore many actors / companies, starting a few decades ago, have changed their focus and investments towards dry-forming techniques wherein rigid cellulose products are manufactured from separated cellulose fibres that are introduced into a product forming unit in the shape of a cellulose blank / web, wherein the cellulose blank is moulded / formed into the shape of the intended cellulose product and wherein the cellulose fibres are bonded to each other using heat and pressure. The dry-forming techniques comprises different steps of generating an air-laid cellulose blank, that is fed into a product forming unit, i.e. a thermo-forming press.

[0007] The technical field of dry manufacturing rigid cellulose products having non-flat general shape, such as trays, lids, or the like, i.e. wherein the forming / pressing is performed in one step using a moulding tool having a first mould part and a second mould part configured to cooperate with each other, is well known. However, the technical field of dry manufacturing rigid cellulose products having non-flat general shape and decorative and / or functional small-pattern on the pressed surface(s) of thin cellulose products, such as trays, plates, cups, packaging, or the like, is still exposed to challenges.

[0008] During moulding / pressing of the rigid cellulose product having essentially non-flat general shape from cellulose blank, there is a correlation between the pressing force and the material characteristics of the pressed cellulose product. On the one hand, a too high pressing force entails that the pressed cellulose product will become brittle / plastic and thereto the final cellulose product obtains a yellow tone, i.e. too high density. On the other hand, a too low pressing force entails that the pressed cellulose product becomes insufficiently moulded, i.e. the internal bonding between the cellulose fibres becomes inadequate, and there will be a great degree of fibre release from the surfaces, i.e. too low density. The applied pressure and the surface weight of the cellulose blank, provides a nominal thickness of the pressed cellulose product having an optimal density.

[0009] Thus, in order to provide pattern on the surface(s) of pressed cellulose product, the male mould part and the female mould part has to have co-operating design, i.e. one of the mould parts comprises a local projection and the other mould part comprises a local recess, in order to obtain the nominal thickness and thereby the correct material characteristics over the entire cellulose product. However, there is an obvious drawback that the pattern has to be wide / broad enough such that the projection and the recess of the mould parts may cooperate.

[0010] Known attempts to provide decorative and / or functional small-pattern on the surfaces of pressed cellulose products, i.e. pattern having less width and / or pattern appearing only on one side of the cellulose product, has not been successful since they are subject to the above-mentioned drawbacks due to too high local press force or too low local press force. The pattern becomes yellow and brittle, or suffer from fibre release, i.e. the appearance and material characteristics of the pressed cellulose product is not satisfactory.

[0011] Thus, there is still a need in the art for a reliable, cheap and unharmful dry-forming technique / process for dry manufacturing rigid cellulose products having non-flat general shape and a considerable depth.Object of the Invention

[0012] The present invention aims at obviating the aforementioned and other disadvantages and failings of previously known methods and devices for dry manufacturing rigid cellulose products, and at providing an improved method and product forming unit for dry manufacturing rigid cellulose products having non-flat general shape and decorative and / or functional small-pattern.

[0013] A primary object of the present invention is to provide an improved product forming unit and method for dry forming / manufacturing rigid cellulose products having non-flat general shape and decorative and / or functional small-pattern, wherein the environmental benefits as well as time and energy saving benefits of conventional dry-forming techniques are maintained. It is another object of the present invention to provide an improved product forming unit and method for dry forming / manufacturing rigid cellulose products having non-flat general shape, wherein the pressed cellulose product has uniform material characteristics.Summary of the Invention

[0014] According to the invention at least the primary object is attained by means of the initially defined product forming unit and method having the features defined in the independent claim. Preferred embodiments of the present invention are further defined in the dependent claims. According to a first aspect of the present invention, there is provided a product forming unit of the initially defined type, wherein the first mould part comprises: a projection that is provided to the essentially even principal surface and has a height (H) in relation to surrounding parts of the principal surface of the first mould part that is equal to or less than 15% of said nominal distance (T) between the principal surface of the first mould part and the principal surface of the second mould part, in order to provide a debossing pattern on the pressed cellulose product, and a recess that is provided to the essentially even principal surface and has a depth (D) in relation to surrounding parts of the principal surface of the first mould part that is equal to or less than 15% of said nominal distance (T) between the principal surface of the first mould part and the principal surface of the second mould part, in order to provide an embossing pattern on the pressed cellulose product, wherein the essentially even principal surface of the second mould part is opposite said projection and said recess of the first mould part.

[0015] According to a second aspect of the present invention, there is provided a method for dry manufacturing rigid cellulose products having essentially non-flat general shape from a cellulose blank using a product forming unit as defined herein above, wherein the method comprises the steps of: providing the cellulose blank into the moulding tool between the first mould part and the second mould part, displacing at least one of the first mould part and the second mould part in the axial direction towards each other, wherein a nominal distance (T) between the principal surface of the first mould part and the principal surface of the second mould part, when located in a press-position during pressing of the cellulose blank, is in the range 0,3-2 millimetres, and providing a debossing pattern on the pressed cellulose product during the pressing of the cellulose product by means of the projection of the first mould part, and providing an embossing pattern on the pressed cellulose product during the pressing of the cellulose product by means of the recess of the first mould part.

[0016] Thus, the present invention is based on the insight that the height and depth of the pattern in relation to the principal surface of the pressed cellulose product may only differ up to 15% of the nominal thickness of the pressed cellulose product, in order not to suffer from fibre release and yellow tone, respectively. Thus, the inventor has realized that there is a correlation between the nominal thickness of the pressed cellulose product and the possible height and depth of the pattern. These findings are based on the understanding that there is an optimal density of all pressed cellulose products within the current / given range of nominal thickness, and different surface weights of the cellulose blanks will thereby provide different nominal thickness of the pressed cellulose products. Thereby, by having both projections and recesses on one of the mould parts the total amplitude of the final pattern of the pressed cellulose product may be twice as high compared to only having debossing or embossing, without suffering from fibre release and / or yellow tone.

[0017] According to various example embodiments of the present invention, the height (H) of the projection is equal to or more than 0,02 millimetres, and / or, the depth (D) of the recess is equal to or more than 0,02 millimetres. Thus, less height or less depth will not be perceived and may be said as unintentional and / or only part of the general surface roughness of the pressed cellulose product.

[0018] According to various example embodiments of the present invention, said predetermined pressure P used during pressing of the cellulose blank is configured to generate a density of the pressed cellulose product that is equal to or more than 1035 kg / m 3< and equal to or less than 1265 kg / m 3< . Thereby, the pressed cellulose product will not suffer from yellow tone and / or fibre release.

[0019] According to various example embodiments of the present invention, the height (H) of the projection of the first mould part is equal to or less than the smaller of 15% of the nominal distance (T) and 0,2 millimetres, and / or, the depth (D) of the recess of the first mould part is equal to or less than the smaller of 15% of the nominal distance (T) and 0,2 millimetres. Thus, for cellulose products having a thickness in the upper region of the given thickness range, the maximum height and depth of the pattern is given by a specific metric dimension instead of a percentage.

[0020] Further advantages with and features of the invention will be apparent from the following detailed description of preferred embodiments.Brief description of the drawings

[0021] A more complete understanding of the abovementioned and other features and advantages of the present invention will be apparent from the following detailed description of preferred embodiments in conjunction with the appended drawings, wherein: Fig. 1is a schematic illustration of a production line or apparatus for dry manufacturing rigid cellulose products, Fig. 2is a schematic illustration of a moulding tool, wherein a cellulose blank is provided into the moulding tool between the first / female mould part and the second / male mould part, Fig. 3is a schematic illustration of the moulding tool according to figure 2 during forming / pressing of the cellulose product, Fig. 4is a schematic illustration of the moulding tool according to figures 2 and 3 after the forming / pressing step and the pressed cellulose product is removed from the moulding tool, Fig. 5is a schematic illustration of the moulding tool according to figures 2-4, the pressed cellulose product being removed from the moulding tool, Fig. 6is a schematic enlargement of the first / female mould part disclosed in figures 2-4, and Fig. 7is a schematic enlargement of a second / male mould part. Detailed description of preferred embodiments of the invention

[0022] As used herein, the term "air / dry moulding / forming or air / dry laying / laid" means a well-known method according to which separated cellulose fibres are formed into a cellulose blank / sheet.

[0023] In air-laying technique, small / short fibres having a normal length in the range of 0,5 to 70 mm, for instance 1 to 50 mm, are separated and captured by an air stream / flow, and then laid on / applied to a forming mesh / surface, usually using an under-pressure at the other side of the mesh / surface. The general terms "air / dry laying" and "air / dry moulding" are used interchangeably herein. The cellulose fibre carrying air flow may be generated by suitable device located upstream and / or downstream the forming mesh / surface.

[0024] Reference is initially made to figures 1 and 5, wherein figure 1 disclose a schematic illustration of a generic production line / apparatus, generally designated 1, for dry manufacturing rigid cellulose products. The production line 1 is configured for manufacturing rigid cellulose products, generally designated 2, having essentially non-flat general shape from separated cellulose fibres. Such a production line / apparatus 1 may be arranged and set-up according to different well-known ways. Figure 5 disclose an example of a rigid cellulose product / tray 2. The apparatus 1 may have automatic transfer / handling between the different process steps, and / or may have manual transfer / handling between the different process steps, and thereto the apparatus 1 may have intermediate storing and / or additional process steps between the disclosed process steps, and / or the process steps may be located at different sites.

[0025] Figure 5 disclose one example of a rigid cellulose product 2 constituted by a rectangular container / tray, wherein the tray is formed using the inventive method. The cellulose product 2 comprises an inclined circumferential wall 3 and an opening 4 defined by a circumferential rim / brim 5 connected to the upper / free end of the wall 3. According to figure 5 embodiment the brim 5 has an angled shape having an essentially radially extending upper surface and a turned-down outer edge, however it shall be pointed out that the cross-section of the brim 5 may have other shapes. The tray 2 may have truncated cone shape having straight wall 3, narrowing in the direction away from the opening 4, in accordance with figure 5 embodiment. The tray 2 may for instance have curved-shaped wall 3 seen in the axial plane. By having inclined walls 3 multiple trays 2 are stackable one inside the other when they are empty. The tray could also be a mug / cup, a lid, packaging or the like container / product. The cross section of the wall 3 in the radial plane may have any suitable shape, circular, oval, rectangular, polygonal, etc., and may differ in shape and / or dimension along the axial extension of the tray 2. The tray 2 may comprise a bottom 6, wherein the bottom 6 is entirely flat or the bottom may comprise local ribs, projections, etc., for strength and rigidity of the cellulose product. The bottom 6 may be located at the very lower end of the wall 3, according to figure 5 embodiment, and / or be partly located at a distance from the lower end of the wall 3, or a combination thereof. The circumferential wall 3 is connected to and extends in the axial direction upwards from the bottom portion 6.

[0026] Cellulose raw material 7, i.e. comprising mainly the cellulose part of organic matter, is provided to the production line, and is fed to a separating / disintegrating unit 8 in order to obtain individualized / separated cellulose fibres. The separated cellulose fibres are thereafter transported by an air stream / flow to a dispenser of a cellulose blank / sheet forming unit 9. The cellulose fibres are laid by the dispenser on a moving or stationary perforated surface of the cellulose blank forming unit 9. The cellulose fibre carrying air flow may be generated by suitable device located upstream and / or downstream the perforated surface. Thereafter the generated cellulose blank, generally designated 10, is transported / transferred to a product forming unit 11, whereby rigid cellulose products 2 are formed and discharged from the product forming unit 11.

[0027] The cellulose blank forming unit 9 may be configured to generate a continuous cellulose blank 10 and / or discontinuous / discrete cellulose blanks 10. Preferably discontinuous / discrete cellulose blanks 10 are fed into the product forming unit 11.

[0028] The cellulose raw material 7 may be in the form of reeled pulp or paper, bale of cellulose pulp, paper, etc. and / or sheets of paper, cellulose pulp, etc. In case said cellulose raw material 7 is in the form of sheets and / or reeled pulp or paper, it can be fed directly into the separating unit 8. However, in case said cellulose raw material 7 is in the form of a bale or compact stacks of sheets, etc. one or more shredders and / or one or more additional separating / disintegrating units 8 may be necessary to be used for separating and dosing said cellulose raw material 7 from said bale or sheets in smaller quantities. The shredder(s) prepare cellulose raw material 7 to be accepted by said separating unit 8. The separating unit 8 disintegrates the cellulose raw material 7 into separated cellulose fibres. Said one or plurality of shredder(s) are arranged before said one or a plurality of separating unit(s) 8, so that an output of one of said shredder is connected to an input of one of said separating units 8. The shredders may be arranged in parallel to each other or in series with each other, and the disintegrating units 8 may be arranged in parallel to each other or in series with each other. The shredders and the disintegrating units 8 together constitute a cellulose fibre separating unit, arranged upstream the cellulose blank forming unit 9.

[0029] Said cellulose raw material 7 may be constituted by virgin cellulose fibres and / or recycled cellulose fibres and may originate from wood pulps such as kraft pulp, sulphite pulp, mechanical pulp, thermomechanical pulp (TMP), chemical treated mechanical pulp, chemi-thermomechanical pulp (CTMP), and / or from non-wood pulps such as bagasse, bamboo, abaca, hemp, flax, cotton.

[0030] The separating unit 8 may according to various embodiments be constituted by a hammer mill. In said separating unit 8 the cellulose raw material is separated into fibres having a normal length in the range of 0,5-70 mm, preferably less than 10 mm. The length of said fibres may be customized by adjusting the internal properties of the separating unit 8 and / or by choosing a different separating unit 8 and / or choosing different cellulose raw material 7. The fibre length for wood pulp is according to various embodiments in the range 0,5-4 mm, preferably in the range 1,7-3,6 mm. According to various embodiments the fibre length for non-wood pulp is in the range 0,5-70 mm.

[0031] The production line 1 may comprise a pre-compression and / or imprinting unit 12, located downstream the cellulose blank forming unit 9 and upstream the product forming unit 11. In the pre-compression and / or imprinting unit 12, an air-laid fluffy cellulose blank 10 having a first thickness may be compressed into a cellulose blank 10 having a second thickness, wherein said second thickness is thinner than said first thickness, and / or may be provided with an imprinting pattern. During the pre-compression / imprinting the cellulose blank is made more coherent and easier to handle, since the pre-compression / imprinting generates internal bindings between individual cellulose fibres preventing mutual separation of the cellulose fibres.

[0032] The product forming unit 11 comprises a press unit 13, and may optionally comprise a pre-heating unit 14 arranged upstream the press unit 13. According to various example embodiments said cellulose blank 10 may be heated to an elevated temperature before being fed into the press unit 13 of the product forming unit 11. In such embodiment(s) where the cellulose blank 10 is preheated before being fed into the press unit 13, said press unit 13 may or may not comprise heating. According to various example embodiment said press unit 13 may be a heated press unit 13 for heating said cellulose blank 10 during pressing. In the case of a heated press unit 13, preheating of said cellulose blank 10 using a pre-heating unit 14 is optional. According to various example embodiments preheating of the cellulose blank 10 in said pre-heating unit 14 may be combined with a heated press unit 13. Having a pre-heating unit 14 in combination with a heated press unit 13 will speed up the manufacturing process in the product forming unit 11, and improve the quality / rigidity of the final rigid cellulose product 2. In the product forming unit 11 the cellulose blank 10 is heated to a temperature in the range 120 - 200 °C in order to obtain adequate rigidity and strength in the final cellulose product 2.

[0033] Reference is now made to figures 2-4, disclosing an example embodiment of the present invention. The press unit 13 comprises a moulding tool having a first mould part 15 and a second mould part 16 having co-operating designs, wherein at least one of the first mould part 15 and the second mould part 16 is / are displaceable in the axial direction in relation to the other, i.e. reciprocating back and forth in relation to each other, in order to exert pressure to the cellulose blank 10 loaded therebetween. In the figures the mutual displacement is disclosed as being vertical, however the mutual displacement may be horizontal or any other suitable angle. The cellulose blank 10 loaded into the moulding tool, is preferably constituted by an air-laid cellulose blank. The cellulose blank 10 may be generated upstream the product forming unit 11 in the same apparatus / production line and provided / transferred to the product forming unit 11, or may be generated at a separate location and provided / transferred to the product forming unit 11 via intermediate handling and storage.

[0034] According to the disclosed example embodiment, the first mould part 15 of the moulding tool is a female mould part, i.e. having a main recess 17 for receiving a major part of the cellulose blank 10, and the second mould part 16 of the moulding tool is a male mould part, i.e. having a main protrusion 18 for cooperation with said recess 17 of the female mould part by being inserted therein, such that the cellulose blank 10 is pressed into a final rigid non-flat shape by applying a predetermined pressure P in the axial direction of the moulding tool. According to the disclosed first embodiment of figures 2-4 the male / second mould part 16 is located above the female / first mould part 15, i.e. the pressed cellulose product 2 is intended to be collected from the female / first mould part 15 after the pressing of the cellulose blank 10. However, according to an alternative to the first embodiment the female / first mould part 15 may be located above the male / second mould part 16, i.e. the pressed cellulose product 2 is intended to be collected from the male / second mould part 15 after the pressing of the cellulose blank 10. According to various embodiments, the first mould part is constituted by a male mould part and the second mould part is constituted by a female mould part.

[0035] The second mould part 16 comprises a product press-surface and a scrap press-surface 19 adjacent said product press-surface. In the disclosed example embodiment, the product press-surface of the second mould part 16 comprises a bottom surface 20, a wall surface 21 connected to the bottom surface 20 and extending essentially in the axial direction, and a brim surface 22 connected to the wall surface 21 and extending essentially in the transversal / radial direction. According to various embodiments, the scrap press-surface 19 of the second mould part 16 surrounds the entire product press-surface. According to other embodiments, the scrap press-surface 19 of the second mould part 16 is only located at some locations around the product press-surface. The first mould part 15 comprises a product press-surface and a scrap press-surface 23 adjacent said product press-surface. In the disclosed example embodiment, the product press-surface of the first mould part 15 comprises a bottom surface 24, a wall surface 25 connected to the bottom surface 24 and extending essentially in the axial direction, and a brim surface 26 connected to the wall surface 25 and extending essentially in the transversal / radial direction. According to various embodiments, the scrap press-surface 23 of the first mould part 15 surrounds the entire product press-surface. According to other embodiments, the scrap press-surface 23 of the first mould part 15 is only located at some locations around the product press-surface.

[0036] According to various embodiments, some moulding tools does not comprise scrap press-surfaces, but the cellulose product 2 is formed in its final design without need for cutting / trimming.

[0037] The scrap press-surface 23 of the first mould part 15 is arranged opposite the scrap press-surface 19 of the second mould part 16, and the product press-surface of the first mould part 15 is arranged opposite the product press-surface of the second mould part 16.

[0038] The cellulose blank 10 is pressed between the surfaces of the male / second mould part 16 and the surfaces of the female / first mould part 15 into final shape. The mutual distance, taken perpendicular to the surface in question, between the product press-surface of the female / first mould part 15 and the product press-surface of the male / second mould part 16 during the pressing of the cellulose blank 10 is T millimetres, wherein T preferably is in the range 0,3-2,0 millimetres, i.e. equal to the thickness of the bottom 6 of the pressed cellulose product 2. Preferably T is in the range 0,3-1,5 millimetres, and most preferably below 1,0 millimetres in order to save raw material. The wall surfaces 21, 25 of the moulding tool has to be inclined in order to obtain a release angle for the cellulose product, and in order to obtain adequate press force to the wall region 3 of the cellulose product 2.

[0039] At the scrap area of the moulding tool, the mutual distance between the scrap press-surface 23 of the first mould part 15 and the scrap press-surface 19 of the second mould part 16 is equal to or more than the mutual distance between the product press-surface of the first mould part 15 and the product press-surface of the second mould part 16. The part of the cellulose blank 10 located at the scrap area may be left entirely uncompressed in the moulding tool, be partially compressed by applying a predetermined partial pressure less than said predetermined pressure P, or be fully compressed by applying said predetermined pressure P. Thus, radially outside the final rigid cellulose product 2, the cellulose blank 10 comprises a scrap area intended to be cut off. In figure 4 the cellulose product 2 is released and schematically removed from the moulding tool by opening the moulding tool. Figure 5 disclose a schematic illustration of a cellulose tray 2 wherein the scrap 27 is cut off from the cellulose tray 2. According to various embodiments, the scrap 27 may be removed in a separate step in the moulding tool, in a subsequent step outside the moulding tool after the pressing of the cellulose blank 10, or in a step concurrent with the pressing of the cellulose blank 10.

[0040] According to various embodiments. When the compartment of the rigid cellulose tray 2 is filled with objects, a film / cover / lid may be attached to the circumferential rim / brim 5 of the cellulose tray 2, for instance using heat lamination. The lid film may be constituted by a multilayer film comprising polymer, metal, and / or paper.

[0041] According to various embodiments. Before any items are placed in the compartment of the rigid cellulose tray, the rigid cellulose tray 2 may be provided with a liner film adhered to at least to the circumferential rim / brim 5, and preferably also to the wall 3 and / or the bottom 6 of the cellulose tray 2. The liner film may be constituted by a multilayer film comprising polymer and / or metal. The adhesion of the liner film to the tray is preferably heat activated.

[0042] According to various embodiments, the cellulose blank 10 may comprise barrier additives and / or material property enhancing additives, etc., such that the rigid cellulose tray 2 withstand grease, fat, water, vapour, etc. The additives are preferably provided to the cellulose fibers upstream the disintegrating unit 8 or between the disintegrating unit 8 and the product forming unit 11.

[0043] The predetermined pressure P is in the range 40-10000N / cm 2< , preferably in the range 100-4000N / cm 2< . According to various embodiments said predetermined pressures are above 1000 N / cm 2< , and according to various embodiments said predetermined pressures are below 2500 N / cm 2< . The holding time during the pressing step is in equal to or more than 0,5 seconds and equal to or less than 10 seconds, preferably less than 5 seconds, and most preferably less than 3 seconds.

[0044] Reference is now especially made to figure 6 disclosing a first schematic embodiment of the present invention, wherein the female mould part is the first mould part 15, and to figure 7 disclosing a second schematic embodiment of the present invention, wherein the male mould part is the first mould part 15. The figures are not drawn to scale.

[0045] The product press-surface of the first mould part 15 has an essentially even / smooth principal / main surface 28 and the product press-surface of the second mould part 16 has an essentially even / smooth principal / main surface 29. Thus, the principal surfaces 28, 29 of the two mould parts are appropriately machined / polished in order to obtain the requested surface roughness / smoothness of the pressed cellulose product 2. Thus, the principal surfaces 28, 29 of the mould parts does not need to be a flat surface, but may as well be a single curved or double curved surface. As described above, the nominal distance (T) between the principal surface 28 of the first mould part 15 and the principal surface 29 of the second mould part 16, when located in a press-position during pressing of the cellulose blank 10, is in the range 0,3-2,0 millimetres, preferably in the range 0,3-1,5 millimetres, and most preferably less than 1,0 millimetres. Thus, the thickness of the pressed cellulose product 2 is equal to said nominal distance (T), and it is preferred to have as thin cellulose product 2 as possible in order to save cellulose raw material, as long as the mechanical characteristics of the cellulose product 2 are fulfilled.

[0046] The first mould part 15 comprise at least one projection 30 that is provided to the principal surface 28 and has a height (H) measured in relation to the surrounding parts of the principal surface 28 of the first mould part 15. The height (H) of the at least one projection 30 is equal to or less than 15% of the nominal distance (T) between the principal surface 28 of the first mould part 15 and the principal surface 29 of the second mould part 16, when located in a press-position during pressing of the cellulose blank 10. During pressing of the cellulose blank 10, said at least one projection 30 provides a debossing pattern 31 on the pressed cellulose product 2. Thus, the depth of the debossing is equal to or less than 15% of the nominal thickness (T) of the pressed cellulose product 2. Thereby, it is secured that the cellulose product 2 is not over-pressed at the location of the debossing pattern 31. Preferably, the height (H) of the at least one projection 30 is equal to or less than 10% of the nominal distance (T) between the principal surface 28 of the first mould part 15 and the principal surface 29 of the second mould part 16. Thereby, it is by margin secured that the cellulose product 2 is not over-pressed at the location of the debossing pattern 31.

[0047] Thereto, the first mould part 15 comprise at least one recess 32 that is provided to the principal surface 28 and has a depth (D) measured in relation to the surrounding parts of the principal surface 28 of the first mould part 15. The depth (D) of the at least one recess 32 is equal to or less than 15% of the nominal distance (T) between the principal surface 28 of the first mould part 15 and the principal surface 29 of the second mould part 16, when located in a press-position during pressing of the cellulose blank 10. During pressing of the cellulose blank 10, said at least one recess 32 provides an embossing pattern 33 on the pressed cellulose product 2. Thus, the height of the embossing is equal to or less than 15% of the nominal thickness (T) of the pressed cellulose product 2. Thereby, it is secured that the cellulose product 2 is not under-pressed at the location of the embossing pattern 33. Preferably, the depth (D) of the at least one recess 32 is equal to or less than 10% of the nominal distance (T) between the principal surface 28 of the first mould part 15 and the principal surface 29 of the second mould part 16. Thereby, it is by margin secured that the cellulose product 2 is not under-pressed at the location of the embossing pattern 33.

[0048] Thus, although each of the debossing pattern 31 and the embossing pattern 33 is small, the total pattern on the pressed cellulose product 2 has the amplitude of the sum of the height (H) of the debossing pattern 31 and the depth (D) of the embossing pattern 33, at the same time as optimal pressing of the cellulose product 2 is provided also at the locations of the total pattern. The total pattern may be decorative / figurative and / or functional / informative.

[0049] According to the invention, the essentially even principal surface 29 of the second mould part 16 is opposite said projection 30 of the first mould part 15 and opposite said recess 32 of the first mould part 15. Thus, the total pattern is provided by the projection 30 and recess 32 as such, without any corresponding design features on the second mould part 16.

[0050] According to figure 6 embodiment, i.e. the first mould part 15 is a female mould part, the debossing pattern 31 and the embossing pattern 33 of the cellulose product 2 are located on the lower side of the bottom 6 of the cellulose product 2. According to figure 7 embodiment, i.e. the first mould part 15 is a male mould part, the debossing pattern 31 and the embossing pattern 33 of the cellulose product 2 are located on the upper side of the bottom 5 of the cellulose product 2.

[0051] According to various embodiments, the height (H) of the at least one projection 30 is equal to or more than 0,02 millimetres. This will result in a debossing pattern 31 that is visible by the naked eye, and provides a clear and distinct difference in relation to general surface roughness of the principal surface 28 of the first mould part 15.

[0052] According to various embodiments, the depth (D) of the at least one recess 32 is equal to or more than 0,02 millimetres. This will result in an embossing pattern 33 that is visible by the naked eye, and provides a clear and distinct difference in relation to general surface roughness of the principal surface 28 of the first mould part 15.

[0053] The nominal thickness (T) of the pressed cellulose product 2 is related to the grammage of the cellulose blank 10 and the predetermined pressure P used during pressing of the cellulose blank 10. According to various embodiments, irrespective the grammage of the cellulose blank 10, the predetermined pressure P used during pressing of the cellulose blank 10 is configured to generate a density of the pressed cellulose product 2 that is equal to or more than 1035 kg / m 3< and equal to or less than 1265 kg / m 3< . Thereby it is secured that no part of the cellulose product 2 is over-pressed or under-pressed, including the debossing pattern 31 and the embossing pattern 33 generated by the projection 30 and recess 32 of the first mould part 15.

[0054] Preferably the generated density of the pressed cellulose product 2 is equal to or more than 1100 kg / m 3< and equal to or less than 1200 kg / m 3< , and the target density is 1150 kg / m 3< . Thereby, it is by margin secured that no part of the cellulose product 2 is over-pressed or under-pressed, including the debossing pattern 31 and the embossing pattern 33 generated by the projection 30 and recess 32 of the first mould part 15.

[0055] According to various embodiments, the principal surface 28 of the first mould part 15 is made of metal and the principal surface 29 of the second mould part 16 is made of an elastic material, such as rubber. According to other various embodiments, both the principal surface 28 of the first mould part 15 and the principal surface 29 of the second mould part 16 are made of metal.

[0056] According to various embodiments, at least 50 % of the product press-surface of the first mould part 15 is constituted by the principal / main surface 28, i.e. free from projections 30 and recesses 32.

[0057] According to various embodiments, the principal surface 28 of the first mould part 15 is located between and separates the projection 30 of the first mould part 15 and the recess 32 of the first mould part 15, i.e. the debossing pattern 31 and the embossing pattern 33 are not directly adjacent each other.

[0058] According to various embodiments, the height (H) of the at least one projection 30 of the first mould part 15 is equal to or less than the smaller of 15% of the nominal distance (T) and 0,2 millimetres. Thus, when the nominal thickness (T) of the pressed cellulose product 2 is in the upper region of the range, the height (H) of the at least one projection 30 is delimited to 0,2 millimetres, in order to secure that the cellulose product 2 is not over-pressed at the location of the debossing pattern 31.

[0059] According to various embodiments, the depth (D) of the at least one recess 32 of the first mould part 15 is equal to or less than the smaller of 15% of the nominal distance (T) and 0,2 millimetres. Thus, when the nominal thickness (T) of the pressed cellulose product 2 is in the upper region of the range, the depth (D) of the at least one recess 32 is delimited to 0,2 millimetres, in order to secure that the cellulose product 2 is not under-pressed at the location of the embossing pattern 33.

[0060] According to various embodiments, non-disclosed, also the second mould part 16 comprises at least one projection and / or at least one recess provided to the principal surface 29 of the second mould part 16. In such embodiments, the essentially even principal surface 28 of the first mould part 15 is opposite such projections of the second mould part 16 and / or opposite such recesses of the second mould part 16. Such projections and recesses of the second mould part 16 are configured in accordance with the projections 30 and recesses 32 of the first mould part 15.

[0061] Thus, according to the inventive method for dry manufacturing rigid cellulose products 2 having essentially non-flat general shape from a cellulose blank 10, using a product forming unit 11 comprising a moulding tool according to the above, the method comprising the steps of: providing the cellulose blank 10 into the moulding tool between the first mould part 15 and the second mould part 16, displacing at least one of the first mould part 15 and the second mould part 16 in the axial direction towards each other, wherein a nominal distance (T) between the principal surface 28 of the first mould part 15 and the principal surface 29 of the second mould part 16, when located in a press-position during pressing of the cellulose blank 10, is in the range 0,3-2 millimetres, and providing a debossing pattern 31 on the pressed cellulose product 2 during the pressing of the cellulose product 2 by means of the projection 30 of the first mould part 15, and providing an embossing pattern 33 on the pressed cellulose product 2 during the pressing of the cellulose product 2 by means of the recess 32 of the first mould part 15.

[0062] Preferably the method comprises the steps of: displacing at least one of the second mould part 16 and the first mould part 15 in the axial direction away from each other, and removing the pressed cellulose product 2 from the moulding tool. Feasible modifications of the Invention

[0063] The invention is not limited only to the embodiments described above and shown in the drawings, which primarily have an illustrative and exemplifying purpose. This patent application is intended to cover all adjustments and variants of the preferred embodiments described herein, thus the present invention is defined by the wording of the appended claims and the equivalents thereof. Thus, the equipment may be modified in all kinds of ways within the scope of the appended claims.

[0064] Throughout this specification and the claims which follows, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or steps or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0065] It shall also be pointed out that it shall be considered understood that features from a specific embodiment disclosed herein can be combined with and / or exchanged by features from another embodiment and the combination obvious, even though not expressly taught, when the combination and / or exchange is possible.

Examples

Embodiment Construction

[0022]As used herein, the term "air / dry moulding / forming or air / dry laying / laid" means a well-known method according to which separated cellulose fibres are formed into a cellulose blank / sheet.

[0023]In air-laying technique, small / short fibres having a normal length in the range of 0,5 to 70 mm, for instance 1 to 50 mm, are separated and captured by an air stream / flow, and then laid on / applied to a forming mesh / surface, usually using an under-pressure at the other side of the mesh / surface. The general terms "air / dry laying" and "air / dry moulding" are used interchangeably herein. The cellulose fibre carrying air flow may be generated by suitable device located upstream and / or downstream the forming mesh / surface.

[0024]Reference is initially made to figures 1 and 5, wherein figure 1 disclose a schematic illustration of a generic production line / apparatus, generally designated 1, for dry manufacturing rigid cellulose products. The production line 1 is configured for manufacturing rigid c...

Claims

1. Product forming unit (11) for dry manufacturing rigid cellulose products (2) having essentially non-flat general shape from a cellulose blank (10), the product forming unit (11) comprising a moulding tool having a first mould part (15) and a second mould part (16), wherein at least one of the first mould part (15) and the second mould part (16) is displaceable in the axial direction in relation to the other in order to press the cellulose blank (10) therebetween into final shape by applying a predetermined pressure P in the axial direction of the moulding tool, wherein the first mould part (15) comprises a product press-surface having an essentially even principal surface (28) and the second mould part (16) comprises a product press-surface having an essentially even principal surface (29), and wherein a nominal distance (T) between the principal surface (28) of the first mould part (15) and the principal surface (29) of the second mould part (16), when located in a press-position during pressing of the cellulose blank (10), is in the range 0,3-2,0 millimetres, characterized in that the first mould part (15) comprises: - a projection (30) that is provided to the essentially even principal surface (28) and has a height (H) in relation to surrounding parts of the principal surface (28) of the first mould part (15) that is equal to or less than 15% of said nominal distance (T) between the principal surface (28) of the first mould part (15) and the principal surface (29) of the second mould part (16), in order to provide a debossing pattern (31) on the pressed cellulose product (2), and - a recess (32) that is provided to the essentially even principal surface (28) and has a depth (D) in relation to surrounding parts of the principal surface (28) of the first mould part (15) that is equal to or less than 15% of said nominal distance (T) between the principal surface (28) of the first mould part (15) and the principal surface (29) of the second mould part (16), in order to provide an embossing pattern (33) on the pressed cellulose product (2), wherein the essentially even principal surface (29) of the second mould part (16) is opposite said projection (30) and said recess (32) of the first mould part (15).

2. The product forming unit (11) according to claim 1, wherein the height (H) of the projection (30) is equal to or more than 0,02 millimetres.

3. The product forming unit (11) according to claim 1 or 2, wherein the depth (D) of the recess (32) is equal to or more than 0,02 millimetres.

4. The product forming unit (11) according to any preceding claim, wherein said predetermined pressure P used during pressing of the cellulose blank (10) is configured to generate a density of the pressed cellulose product (2) that is equal to or more than 1035 kg / m3 and equal to or less than 1265 kg / m3.

5. The product forming unit (11) according to any preceding claim, wherein the principal surface (28) of the first mould part (15) is made of metal and the principal surface (29) of the second mould part (16) is made of an elastic material, such as rubber.

6. The product forming unit (11) according to any preceding claim, wherein at least 50 % of the product press-surface of the first mould part (15) is constituted by the principal surface (28).

7. The product forming unit (11) according to any preceding claim, wherein the principal surface (28) of the first mould part (15) is located between and separates the projection (30) of the first mould part (15) and the recess (32) of the first mould part (15).

8. The product forming unit (11) according to any preceding claim, wherein the height (H) of the projection (30) of the first mould part (15) is equal to or less than the smaller of 15% of the nominal distance (T) and 0,2 millimetres.

9. The product forming unit (11) according to any preceding claim, wherein the depth (D) of the recess (32) of the first mould part (15) is equal to or less than the smaller of 15% of the nominal distance (T) and 0,2 millimetres.

10. The product forming unit (11) according to any preceding claim, wherein the cellulose blank (10) is composed of an air-laid cellulose blank.

11. Method for dry manufacturing rigid cellulose products (2) from a cellulose blank (10) using a moulding tool having a first mould part (15) and a second mould part (16), wherein at least one of the first mould part (15) and the second mould part (16) is displaceable in the axial direction in relation to the other in order to press the cellulose blank (10) therebetween into final shape by applying a predetermined pressure P in the axial direction of the moulding tool, wherein the first mould part (15) comprises a product press-surface having an essentially even principal surface (28) and the second mould part (16) comprises a product press-surface having an essentially even principal surface (29), wherein the first mould part (15) comprises: - a projection (30) that is provided to the essentially even principal surface (28) and has a height (H) in relation to surrounding parts of the principal surface (28) of the first mould part (15) that is equal to or less than 15% of a nominal distance (T) between the principal surface (28) of the first mould part (15) and the principal surface (29) of the second mould part (16) during pressing of the cellulose blank (10), and - a recess (32) that is provided to the principal surface (28) and has a depth (D) in relation to the surrounding parts of the principal surface (28) of the first mould part (15) that is equal to or less than15% of said nominal distance (T) between the principal surface (28) of the first mould part (15) and the principal surface (29) of the second mould part (16), wherein the essentially even principal surface (29) of the second mould part (16) is opposite said projection (30) and said recess (32) of the first mould part (15), the method comprising the steps of: - providing the cellulose blank (10) into the moulding tool between the first mould part (15) and the second mould part (16), - displacing at least one of the first mould part (15) and the second mould part (16) in the axial direction towards each other, wherein a nominal distance (T) between the principal surface (28) of the first mould part (15) and the principal surface (29) of the second mould part (16), when located in a press-position during pressing of the cellulose blank (10), is in the range 0,3-2 millimetres, and - providing a debossing pattern (31) on the pressed cellulose product (2) during the pressing of the cellulose product (2) by means of the projection (30) of the first mould part (15), and providing an embossing pattern (33) on the pressed cellulose product (2) during the pressing of the cellulose product (2) by means of the recess (32) of the first mould part (15).

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