A method for producing a cellulose product with an opening and a cellulose product with an opening

Abstract

A method for producing a cellulose product (1) comprising an opening (4) with a forming mould (5), where the forming mould (5) comprises a first cutting edge (10) and a second cutting edge (12), wherein the method comprises the steps of; forming the cellulose blank structure (2) from a dry-formed cellulose fibres 5 layer (3); positioning the cellulose blank structure (2) in the forming mould (5) when the forming mould (5) is in an idle state (27); cutting a slit (13) in the cellulose blank structure (2) when the forming mould (5) is in an intermediate state (28); and forming the cellulose product (1) from the cellulose blank structure (2) in the forming mould (5) by positioning the forming mould (5) in 10 the pressing state (29), where the opening (4) is formed between a first cut edge (19) and a second cut edge (20) of the cellulose blank structure (2) when the forming mould (5) moves from the intermediate state (28) to the pressing state (29), and where the opening (4) is perpendicular to the pressing direction of the forming mould (5).

Description

[0001] A METHOD FOR PRODUCING A CELLULOSE PRODUCT WITH AN

[0002] OPENING AND A CELLULOSE PRODUCT WITH AN OPENING

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to a method for producing a three-dimensional shaped cellulose product comprising an opening from a layer of dry-formed cellulose fibres. The present disclosure also relates to a three-dimensional shaped cellulose product comprising an opening. The present disclosure also relates to a forming mould to be used for producing a three-dimensional shaped cellulose product comprising an opening.

[0005] BACKGROUND

[0006] Cellulose fibres are often used as raw material for producing or manufacturing products. Products formed of cellulose fibres can be used in many different situations where there is a need for having sustainable products of flat or essentially non-flat shapes. A flat shape may refer to a generally two- dimensional shape and essentially non-flat shapes may refer to any suitable three-dimensional object shape. There is a wide range of products that can be produced from cellulose fibres and a few examples are disposable plates and cups, blank structures and packaging materials. Packages produced from cellulose fibres may for example be used for packaging of liquids, dry materials and other types of goods, where the packaging may be made in a three- dimensional shape or formed into a three-dimensional shape from a two- dimensional sheet material.

[0007] A low price material commonly used for cellulose fibre products is wet moulded pulp. Wet moulded pulp has the advantage of being considered as a sustainable packaging material, since it is produced from biomaterials and can be recycled after use. Consequently, wet moulded pulp has been quickly increasing in popularity for different applications. Wet moulded pulp articles are generally formed by immersing a suction mould into a liquid or semi liquid pulp suspension or slurry, while suction is applied, whereby a body of pulp is formed with the shape of the desired product by fibre deposition. The suction mould is then withdrawn from the suspension and the suction is generally continued to compact the deposited fibres while exhausting residual liquid. With all wet-forming techniques there is a need for drying of the wet moulded product, where the drying is a very time and energy consuming part of the production. The demands on aesthetical, chemical and mechanical properties of products are increasing, and due to the properties of wet-formed cellulose products, the mechanical strength, flexibility, and chemical properties are limited. It is also difficult in the wet-forming process to control the mechanical properties of the products with high precision.

[0008] Cellulose products may also be produced using a dry-formed cellulose fibres layer, where the dry-formed cellulose fibres layer is formed in a dry-forming process in which the cellulose fibres are carried and formed to the fibre layer structure by air as carrying medium. The cellulose fibres layer is then pressed in a forming mould having a shape corresponding to the shape of the desired cellulose product. The forming of the cellulose product is preferably performed by heating the cellulose fibres layer and / or the mould. One problem with heating the mould is that the tolerances between the upper mould part and the lower mould part may change in dependency of the heat.

[0009] Some tolerances between the mould parts are not very critical. This includes the sections in which the cellulose product is formed, where the distance between the upper and lower parts of the mould is in the region of e.g., 0,5 to 1 ,5 mm, which corresponds to the thickness of the cellulose product. A slight variation of the distance between two press surfaces will not affect the performance of the final product. Other sections of the mould parts are more critical, e.g. a cutting part of the mould. The desired distance between the cutting edges of an upper cutting part and a lower cutting part arranged for shear cutting may be in the region of less than 0,05 mm and down to 0,01 mm. With such small tolerances, great care must be taken to ensure that the cutting parts can move freely and that they do not overlap, which will destroy the mould if the two parts collides. The cutting tool may cut the entire circumference of the cellulose product and / or may cut an opening in the cellulose product. A short distance between the cutting edges is required in order to ensure a reliable shear cutting with a clean cut where the fibres are cut and not tom apart.

[0010] A further problem when cutting an opening in a layer of dry-formed cellulose fibres in a mould is that the cut-away part must be removed separately from the mould. The cut-away part may e.g. be removed by a separate compressed airflow that blows away the cut-away part. The advantage of using pressurized air is that the blowing nozzle can be positioned out of the way for the pressing mould. Such a removal will however spread the cut-away parts in an uncontrolled manner. It is also possible to use a suction means to remove the cut-away parts in a more controlled manner. Such a suction means must however be positioned close to the cut-away parts, e.g. arranged on a movable holder of some kind.

[0011] There is thus a need for an improved cellulose products having an opening, where the opening is produced in an efficient and cost-efficient way.

[0012] SUMMARY

[0013] An object of the present disclosure is to provide a method for producing a cellulose product comprising an opening. This object is at least partly achieved by the features of the independent claim. The dependent claims contain further developments of the method for producing a cellulose product comprising an opening. Another object of the present disclosure is to provide a three- dimensional shaped cellulose product provided with an opening and a forming mould arranged for creating an opening in a cellulose product.

[0014] The disclosure concerns a method for producing a cellulose product comprising an opening from a cellulose blank structure with a forming mould, where the forming mould comprises an upper mould part and a lower mould part, where the upper mould part comprises a first cutting edge and the lower mould part comprises a second cutting edge, where the forming mould comprises an idle state in which the upper mould part and the lower mould part are spaced apart, an intermediate state and a pressing state, wherein the method comprises the steps of; forming the cellulose blank structure from a dry-formed cellulose fibres layer; positioning the cellulose blank structure between the upper mould part and the lower mould part when the forming mould is in the idle state; cutting a slit in the cellulose blank structure with the first cutting edge and the second cutting edge when the forming mould is in the intermediate state, in which the first cutting edge and the second cutting edge are positioned adjacent each other, thereby creating the slit which is delimited by a first cut edge and a second cut edge in the cellulose blank structure; and forming the cellulose product from the cellulose blank structure in the forming mould by positioning the forming mould in the pressing state, in which the cellulose blank structure is pressed with a forming pressure of at least 1 MPa, preferably 4-20 MPa, wherein the cellulose blank structure is shaped into the three-dimensional cellulose product, and wherein the opening is formed between the first cut edge and the second cut edge of the cellulose blank structure when the forming mould moves from the intermediate state to the pressing state.

[0015] With the inventive method, an opening in a cellulose product is provided in a simple manner without creating any residue from the cutting operation. The opening is created between a first cut edge and a second cut edge of the cellulose blank structure. The opening will be perpendicular to the pressing direction of the forming mould and will thus be oriented in a horizontal direction when the pressing direction is in a vertical direction. The width of the opening depends on the width of the cutting edge. The height of the opening depends on the forming mould.

[0016] The opening is created by cutting a slit in the cellulose blank structure. The slit is cut in the forming mould before the cellulose product is pressed. In this way, the cut edges of the cellulose blank structure will be pressed in the forming mould when the cellulose product is pressed. Since the distance between the first cutting edge of the upper mould part and the corresponding second cutting edge of the lower mould part is relatively large due to the relative large tolerance used, the shear cutting will not be perfect, but since both cut edges of the slit will be pressed after the slit is cut when the cellulose product is formed in the forming mould, this will not affect the function of the finished cellulose product. A smaller tolerance will achieve a cleaner cut. Further, since the cellulose product is a disposable product that will be used once, a somewhat inferior cutting is acceptable. In this way, the production of a cellulose product with an opening is greatly simplified since no cut-away material must be handled and since the tolerances can be relatively large.

[0017] The distance between the first cutting edge of the upper mould part and the second cutting edge of the lower mould part is preferably at least 0,1 mm, and may be in the range between 0,10 and 0,20 mm. This range gives an enough tolerance for the forming mould and still allows for good enough cutting of the slit. With a smaller distance, e.g. below 0,05 mm, the tolerance for the forming mould will make the instalment and use of the forming mould more complicated and time consuming, and with a larger distance, e.g. above 0,3 mm, the cellulose blank structure will not be cut but will be tom apart, which will give a non-acceptable end result. An acceptable cutting distance for shear cutting is normally considered to be below 0,05 mm and preferably below 0,03 mm in order to provide a clean cut.

[0018] The first cutting edge is in one example 90 degrees, and since the first cutting edge will cut the slit in the cellulose blank structure when it moves towards the second cutting edge, the first cutting edge should be relatively sharp. The first cutting edge will catch the cellulose blank structure and will cut a slit during the movement towards the second cutting edge. When the first cutting edge is adjacent the second cutting edge, the slit is cut. The angle between the front side and the pressure side adjacent the first cutting edge is in one example 90 degrees, but may be in the region between 40 to 120 degrees. The first cutting edge is in one example arranged on a first cutting part that can be removed from the forming mould, such that the first cutting edge can be replaced when it is worn. In this way, the complete forming mould must not be replaced when the first cutting edge is dull. The first cutting part also comprises a pressing surface that is part of the complete pressing surface of the forming mould. In this way, the first cutting edge will be more robust than a thin cutting blade. It is also possible to replace the first cutting part if the size or shape of the opening should be changed.

[0019] The second cutting edge is in the shown example blunt and is around 30 degrees. The angle of the second cutting angle is in the shown example determined on the shape of the cellulose product and the position of the opening that is to be created. In the shown example, the opening is positioned in a rim of a container, where the angle of the second cutting edge corresponds to the inclination of the rim. The second cutting angle may be sharp with an angle up to 90 degrees.

[0020] The second cutting edge is in one example arranged on a second cutting part that can be removed from the forming mould, such that the second cutting part can be replaced when the second cutting edge is worn. It is also possible to replace the second cutting part if the first cutting part is replaced, e.g. if the size or shape of the opening should be changed. In this way, the complete forming mould must not be replaced when the second cutting edge should be replaced. The second cutting part also comprises a pressing surface that is part of the complete pressing surface of the forming mould.

[0021] By replacing both the first cutting part and the second cutting part, the size and shape of the opening can be varied, and it is also possible to use parts that do not cut at all, such that a cellulose product without an opening is formed. This may e.g. be advantageous if a forming mould is used for several different types of containers, both with and without openings. In one example, the opening is arranged in a side wall of a cellulose product, e.g. at the rim of a clamshell container, where the opening is used as a locking opening in cooperation with a tab. In another example, the opening is arranged in the lid of a container, e.g. as a ventilation opening. The ventilation opening will allow steam or vapour to escape the container, e.g. a clamshell container holding a hamburger. An opening may also be arranged in e.g. a coffee lid.

[0022] Advantages with these features are that the method provides an efficient manufacturing process for a cellulose product having at least one opening in the cellulose product material, where the cellulose product can be manufactured in an efficient manner. The method also provides a cost-efficient and rational production of cellulose products having at least one opening through its few simple steps compared to traditional production methods. The opening is created in the forming mould, before the cellulose product is pressed, and the opening is created without any cut-away material that must be removed separately.

[0023] The cellulose blank structure comprises a dry-formed cellulose fibres layer preferably having a fibre composition of 95-100% cellulose fibres or natural cellulose fibres. The cellulose blank structure may further be provided with a first tissue layer applied on one side of the formed cellulose fibres layer and a second tissue layer applied on the other side of the formed cellulose fibres layer. The first tissue layer and the second tissue layer preferably have a fibre composition of 95-100% cellulose fibres or natural cellulose fibres.

[0024] The dry-formed cellulose fibres layer is formed in a dry-forming process where the cellulose fibres are carried and formed to the fibre layer structure by air as carrying medium.

[0025] The cellulose product is formed in the forming mould during a forming time period in the range of 0,1 to 20 seconds, and preferably 1 to 10 seconds. The forming time together with the forming temperature and the forming pressure are important parameters in the forming of the cellulose product. The first tissue layer and / or the second tissue layer and / or the dry-formed cellulose fibres layer may comprise one or more additives that are altering the mechanical, hydrophobic, and / or oleophobic properties of the cellulose product. The one or more additives of the first tissue layer and / or the second tissue layer may be starch compounds, rosin compounds, butanetetracarboxylic acid, gelatine compounds, alkyl ketene dimer (AKD), Alkenyl Succinic Anhydride (ASA), and / or fluorocarbons. By using additives, the properties of the cellulose product can be efficiently steered and controlled. The additives can alter the mechanical, hydrophobic, and / or oleophobic properties so that the cellulose product can be used for different purposes. For example, it can be possible to create a scratch free surface by the use of a starch compound as an additive. It should be noted that the list of additives is not exhaustive in the meaning that other additives and / or chemical substances can be added for a designed property of the final product.

[0026] The cellulose product according to the invention is provided with a base layer made from air-laid dry-formed cellulose fibres that forms a dry-formed cellulose fibres layer. The cellulose product further comprises a first tissue layer arranged on a first side of the dry-formed cellulose fibres layer and a second tissue layer arranged on a second side of the dry-formed cellulose fibres layer.

[0027] According to an aspect of the disclosure, the cellulose blank structure is heated in the forming mould. This provides an efficient heating of the multi-layer cellulose blank structure.

[0028] According to another aspect of the disclosure, the cellulose product is shaped into a three-dimensional structure from the cellulose blank structure during the forming in the forming mould. During the forming of the cellulose product in the forming mould, the cellulose product will achieve its three-dimensional shape.

[0029] BRIEF DESCRIPTION OF DRAWINGS

[0030] The disclosure will be described in greater detail in the following, with reference to the attached drawings, in which Fig. 1 shows schematically, an apparatus for producing a cellulose product from a cellulose blank structure according to the disclosure,

[0031] Figs. 2a-d show schematically the cutting steps for the opening in the cellulose product produced from a cellulose blank structure according to the disclosure,

[0032] Fig. 3 shows a view of the cutting tool, and

[0033] Fig. 4 shows an example of a cellulose product comprising an opening according to the invention.

[0034] DESCRIPTION OF EXAMPLE EMBODIMENTS

[0035] Various aspects of the disclosure will hereinafter be described in conjunction with the appended drawings to illustrate and not to limit the disclosure, wherein like designations denote like elements, and variations of the described aspects are not restricted to the specifically shown embodiments, but are applicable on other variations of the disclosure.

[0036] In the present detailed description, a method for producing a cellulose product from a cellulose blank structure will be described.

[0037] Embodiments of sheet materials or blanks according to the disclosure are mainly discussed with reference to a cellulose blank structure placed in position for forming in a forming mould, where the cellulose blank structure has a flat shape. It should be noted that this will not limit the scope of the present disclosure, which for example may include, a cellulose blank structure preshaped into a three-dimensional shape. The cellulose blank structure may be presented to the forming mould in a shape similar to the desired final shape of the object if desired. A cellulose product according to the disclosure may be made in a three- dimensional shape or formed into a three-dimensional shape from a two- dimensional blank or sheet material.

[0038] Figure 1 schematically shows a machine for producing a cellulose product 1 from a cellulose blank structure 2, where the cellulose blank structure 2 comprises a dry-formed cellulose fibres layer 3, a first tissue layer 14 and a second tissue layer 15.

[0039] With a dry-formed cellulose fibres layer is meant a cellulose fibre layer that is formed in a dry-forming process in which cellulose fibres are air-laid to form the cellulose fibre layer. When forming the cellulose fibre layer in the air-laid process, the cellulose fibres are carried and formed to the fibre layer structure by air as carrying medium. In the air-laid process, small amounts of water or other substances may if desired be added to the cellulose fibres in order to change the properties of the cellulose product, but air is still used as carrying medium in the forming process. The layer of dry-formed cellulose fibres may have a dryness that is mainly corresponding to the ambient humidity in the atmosphere surrounding the layer of dry-formed cellulose fibres.

[0040] To produce the cellulose products, the cellulose blank structure may be arranged as a layered continuous web. The continuous web may be formed from the layers in a continuous process step, where the continuous web is fed to the forming mould to form the cellulose products.

[0041] In the embodiment shown in Fig. 1 , the dry-formed cellulose fibres layer 3 is produced from loose and separated fibres produced in a mill 16 in a known manner, where defibrated fibres are fed by air as a carrying medium from the mill to a suitable substrate (not shown) to form the dry-formed cellulose fibres layer. The first tissue layer 14 is provided on a first tissue roll 17 and the second tissue layer 15 is provided on a second tissue roll 18.

[0042] A first pair of pressure feed rollers may be used for compacting the dry-formed cellulose fibres layer 3 if required. A second set of pressure feed rollers may be used to compact the cellulose blank structure and to unwind the first tissue layer 14 and the second tissue layer 15.

[0043] In this embodiment the first tissue layer 14 is arranged below the dry-formed cellulose fibres layer 3, and the second tissue layer 15 are arranged above the dry-formed cellulose fibres layer 3, but the layers may suitably be arranged in the opposite order, depending on the used forming mould.

[0044] The second pair of pressure feed rollers may be arranged so that the rollers are pushed against each other with a force Fi , and when the layers are passing between the second pair of pressure feed rollers, the layers are compacted and forming the cellulose blank structure 2. The force Fi may be chosen so that a desired compacting of the cellulose blank structure is achieved.

[0045] As a non-limiting example, in order to achieve a desired compacting of the cellulose blank structure, the force Fi of the second pair of pressure feed rollers may be in the range 2000 N to 17000 N, and the cellulose blank structure may have a width of 0,6 m. The second pair of pressure feed rollers may be heated, for example to a temperature in the range of 70°C to 170°C, so that the cellulose blank structure is heated during the compression in the second pair of pressure feed rollers. The heating of the cellulose blank structure during compression will form a compressed ductile web structure that is suitable for being transported to and formed in the forming mould.

[0046] Further according to the method, the cellulose blank structure is arranged in the forming mould 5. The forming mould comprises an upper mould part 6 and a lower mould part 7. The cellulose blank structure may be arranged in the forming mould in any suitable way, and as an example, the cellulose blank structure may be manually fed to and arranged in the forming mould. The forming mould is provided with an idle state 27, an intermediate state 28 and a pressing state 29. In the idle state, the upper mould part 6 and the lower mould part 7 are separated, in this example with the lower mould part fixed on a lower base part of the press 30, and with the upper mould part 6 attached to the movable upper part of the press 30. When the forming mould is in the idle state, the cellulose blank structure can be positioned in the forming mould.

[0047] The cellulose blank structure could as an alternative be intermittently fed to the forming mould by a suitable feeding unit if the cellulose blank structure is arranged as a continuous web transported with a constant speed, and the forming of the cellulose products in the forming mould may take place in intermittent process steps.

[0048] In the embodiment shown in figure 1 , the cellulose blank structure 2 is heated and formed into the cellulose product 1 , where the cellulose product 1 is having a three-dimensional bowl-shaped product configuration. However, as described above, the cellulose product 1 may have any desired three- dimensional shape. The first tissue layer 14 and the second tissue layer 15 are unwound from the first tissue roll 17 and the second tissue roll 18 respectively, and the layers may be compressed by the second set of pressure feed rollers. In this way, the cellulose blank structure 2 is formed.

[0049] In order to form the cellulose product, the cellulose blank structure 2 is positioned in the forming mould 5 when the forming mould Is in the idle state. The cellulose blank structure 2 is heated to a forming temperature in the range of 100°C to 300°C and then pressed in the forming mould 5 with a forming pressure of at least 1 MPa, preferably 4-20 MPa. The heating of the cellulose blank structure 2 may take place before arranging the cellulose blank structure 2 in the forming mould 5 or at least partly before the pressing in the forming mould 5. This may for example be accomplished through arranging a suitable heating unit in the manufacturing process. As an alternative, the heating of the cellulose blank structure 2 may take place in the forming mould 5 when being pressed. The heating of the cellulose blank structure 2 may for example be accomplished through heating the forming mould 5 before pressing the cellulose blank structure 2. When the cellulose fibres of the cellulose blank structure is pressed in the forming mould, the cellulose fibres will be bonded to each other in a way so that the resulting cellulose product will have good mechanical properties. Tests have shown that higher forming temperatures will give stronger bonding between the cellulose fibres when being pressed at a specific forming pressure. With forming temperatures above 100°C together with a forming pressure of at least 1 MPa, preferably 4-20 MPa, the cellulose fibres will be strongly bonded to each other with hydrogen bonds. At temperatures higher than 300°C, the cellulose fibres will be thermally degraded and therefore temperatures above 300°C should be avoided. The forming pressure and the forming temperature may be chosen to be suitable for the specific cellulose product to be produced.

[0050] Tests have shown that when forming the cellulose product suitable pressure levels are, in the range of 1 -100 MPa, and suitable temperature levels are in the range of 100°C to 300°C. However, pressure levels in the range of 4-20 MPa, and temperature levels in the range of 140°C to 200°C are often sufficient in order to achieve cellulose products with desired properties.

[0051] An example of a cellulose product 1 is shown in Fig. 4. In this embodiment, the cellulose product is a food tray, here a clamshell container. The food tray comprises a lower part 21 having a bottom, side walls and a rim section 22. The food tray further comprises a lid 23 provided with a tab 24, where the lid is connected to the lower part with a hinge. An opening 4 in the form of a locking opening 25 is arranged in the rim section and is here used for a locking function in cooperation with the tab 24 arranged on the lid 23. A further opening 4 is also provided in the lid of the food tray. Here, the opening function as a ventilation opening 26 that will let out vapour or steam from a hot food product placed in a closed food tray.

[0052] An example of a cutting tool 8 that is to be mounted in a forming mould 5, shown in Fig. 3, comprises a first cutting part 9 provided with a first cutting edge 10, and a second cutting part 11 provided with a second cutting edge 12. The first cutting part 9 is mounted in the upper mould part 6 and the second cutting part 11 is mounted in the lower mould part 7. The first cutting part 9 and the second cutting part 11 are referred to as a cutting tool 8. The first cutting edge will interact with the second cutting edge before the cellulose product is pressed.

[0053] Figs. 2a - 2d show the steps of cutting a slit 13 in the cellulose blank structure 2 and to create an opening in the cellulose product. Fig. 2a shows a cellulose blank structure 2 arranged in the forming mould 5 between the first cutting part 9 and the second cutting part 11 when the forming mould is in the idle state 27. In Fig. 2b, the first cutting part 9 with the first cutting edge 10 is moving towards the second cutting edge 12 and starts to compress the cellulose blank structure and to cut the cellulose blank structure. In Fig. 2c, the first cutting edge 10 has reached the position of the second cutting edge 12 and the cutting of a slit 13 in the cellulose blank structure is finalized. The forming mould is here in an intermediate state 28, in which the first cutting edge 10 is adjacent the second cutting edge 12. The sideway distance between the first cutting edge 10 and the second cutting edge 12, i.e. the distance perpendicular to the pressing direction, is preferably greater than 0,10 mm, and may be in the region between 0,10 to 0,20 mm.

[0054] In the intermediate state, the slit 13 in the cellulose blank structure has been cut completely and is delimited by a first cut edge 19 and a second cut edge 20. The slit is shear cut between the first cutting edge and the second cutting edge. When the slit is cut, the upper mould part continues towards the pressing state. This movement will create the opening between the first cut edge and the second cut edge, since the first cut edge and the second cut edge will be pressed by the forming mould. The first cut edge 19 will be held and pressed at the second cutting part and the second cut edge 20 will be moved downwards and will be pressed by the first cutting part.

[0055] In Fig. 2d, the forming mould is in the pressing state 29 and the cellulose product is pressed by the forming mould. The opening is formed between the first cut edge 19 of the cellulose blank structure and the second cut edge 20 of the cellulose blank structure. When the cellulose blank structure with the cut edges are pressed, the opening is created between the cut edges.

[0056] The opening 4 will be perpendicular to the cutting direction of the cutting tool and to the pressing direction of the forming tool. By cutting a slit in the cellulose blank structure and by pressing the cut edges of the cellulose blank structure, an opening is created in the cellulose product without having to cut away a part of the cellulose blank structure. When an opening is created in a conventional product, a part of the product is cut away from the product, where the cut-away part corresponds to the shape of the opening. One example is hole punching in paper boards. By forming an opening in a cellulose product at the same time as the cellulose product is pressed, a separate hole punch operation is not necessary. By cutting a slit in the cellulose blank structure and then by pressing the cut edges, there is no need to remove any cut-away material from the forming mould.

[0057] In the example shown in Fig. 4, one opening is formed as a locking opening 25 in a rim section of the container. The container is in the shown example a clamshell container having a lower part 21 and a lid 23 connected by a hinge of some sort. The opening is in this case used for a locking function in cooperation with a tab 24 arranged on the lid 23.

[0058] In the shown example, an opening is formed in a flat surface, here in the upper part of the lid. Such an opening may be used as a ventilation opening 26 that will let out steam from a hot food product from the clamshell when the clamshell is closed. The height and width of the opening is determined by the cutting tool.

[0059] In another example (not shown), the cellulose product is a coffee lid having a substantially flat upper surface and a rim section, where the rim is provided with an inwardly extending edge section arranged to lock to a coffee container with a snap-action. The upper surface is provided with at least one opening, where the opening is used as a ventilation opening that will let out steam from a hot beverage in the container, and that will allow air to enter the container such that an underpressure in the container is prevented when a user drinks from a drinking opening in the lid.

[0060] Other types of openings may also be created in a cellulose product. Since the slit used to create the opening is cut in a direction parallel to the pressing direction, an opening can only be created in a surface that is inclined to the pressing direction of the forming mould, or that is perpendicular to the pressing direction.

[0061] The first cutting part 9 may be integrated in the upper mould part 6 and the second cutting part 11 may be integrated in the lower mould part 7. In one example, both the first cutting part and the second cutting part are mounted in a removable manner. In this way, the cutting part may be replaced when the cutting edge is worn, such that the complete upper mould part must not be replaced. The anvil part may also be replaced. By replacing both the cutting part and the anvil part, the size and shape of the opening can be varied. In one example, the cutting part and the anvil part may be replaced with parts that do not cut a slit in the cellulose blank structure. In this case, a cellulose product without an opening may be produced. This may e.g. be advantageous when the same forming mould is used for hot food products that require a ventilation opening and for cold food products that do not require a ventilation opening.

[0062] It will be appreciated that the above description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. While specific examples have been described in the specification and illustrated in the drawings, it will be understood by those of ordinary skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure as defined in the claims. Furthermore, modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure is not limited to the particular examples illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out the teachings of the present disclosure, but that the scope of the present disclosure will include any embodiments falling within the foregoing description and the appended claims. Reference signs mentioned in the claims should not be seen as limiting the extent of the matter protected by the claims, and their sole function is to make claims easier to understand.

[0063] REFERENCE SIGNS

[0064] 1 : Cellulose product

[0065] 2: Cellulose blank structure

[0066] 3: Dry-formed cellulose fibres layer

[0067] 4: Opening

[0068] 5: Forming mould

[0069] 6: Upper mould part

[0070] 7: Lower mould part

[0071] 8: Cutting tool

[0072] 9: First cutting part

[0073] 10: First cutting edge

[0074] 11 : Second cutting part

[0075] 12: Second cutting edge

[0076] 13: Slit

[0077] 14: First tissue

[0078] 15: Second tissue

[0079] 16: Mill

[0080] 17: First tissue roll

[0081] 18: Second tissue roll

[0082] 19: First cut edge

[0083] 20: Second cut edge

[0084] 21 : Lower part

[0085] 22: Rim section

[0086] 23: Lid

[0087] 24: Tab

[0088] 25: Locking opening

[0089] 26: Ventilation opening

[0090] 27: Idle state

[0091] 28: Intermediate state

[0092] 29: Pressing state

[0093] 30: Press

Claims

CLAIMS1 . A method for producing a cellulose product (1 ) comprising an opening (4) from a cellulose blank structure (2) with a forming mould (5), where the forming mould (5) comprises an upper mould part (6) and a lower mould part (7), where the upper mould part (6) comprises a first cutting edge (10) and the lower mould part (7) comprises a second cutting edge (12), where the forming mould (5) comprises an idle state (27) in which the upper mould part (6) and the lower mould part (7) are spaced apart, an intermediate state (28) and a pressing state (29), wherein the method comprises the steps of; forming the cellulose blank structure (2) from a dry-formed cellulose fibres layer (3); positioning the cellulose blank structure (2) between the upper mould part (6) and the lower mould part (7) when the forming mould (5) is in the idle state (27); cutting a slit (13) in the cellulose blank structure (2) with the first cutting edge (10) and the second cutting edge (12) when the forming mould (5) is in the intermediate state (28), in which the first cutting edge (10) and the second cutting edge (12) are positioned adjacent each other, thereby creating the slit (13) which is delimited by a first cut edge (19) and a second cut edge (20) in the cellulose blank structure (2); and forming the cellulose product (1 ) from the cellulose blank structure (2) in the forming mould (5) by positioning the forming mould (5) in the pressing state (29), in which the cellulose blank structure (2) is pressed with a forming pressure of at least 1 MPa, preferably 4-20 MPa, where the cellulose blank structure (2) is shaped into the three-dimensional cellulose product (1 ), and where the opening (4) is formed between the first cut edge (19) and the second cut edge (20) of the cellulose blank structure (2) when the forming mould (5) moves from the intermediate state (28) to the pressing state (29), and where the opening (4) is perpendicular to the pressing direction of the forming mould (5).

2. A method according to claim 1 , wherein the cellulose blank structure (2) is heated to a forming temperature in the range of 100°C to 300°C.

3. A method according to any of the preceding claims, wherein the distance between the first cutting edge (10) and the second cutting edge (12) is greater than 0,10 mm when the forming mould is in the intermediate state (28).

4. A method according to any of the preceding claims, wherein the cellulose product (1 ) is formed in the forming mould (5) during a forming time period in the range of 1 to 10 seconds.

5. A forming mould (5) to be used to form a cellulose product (1 ) comprising an opening (4) from a cellulose blank structure (2), where the forming mould (5) comprises an upper mould part (6) and a lower mould part (7), c h a r a c t e r i z e d i n that the upper mould part (6) comprises a first cutting edge (10) and that the lower mould part (7) comprises a second cutting edge (12), where the first cutting edge (10) and the second cutting edge (12) are arranged to cut a slit (13) in the cellulose blank structure (2) when the forming mould is in an intermediate state (28), and where the forming mould (5) is arranged to form an opening (4), where the opening (4) is perpendicular to the pressing direction of the forming mould (5), in the cellulose product (1 ) from the slit (13) when the forming mould (5) is moved from the intermediate state (28) to the pressing state (29).

6. A forming mould (5) according to claim 5, wherein the first cutting edge (10) is arranged on a first cutting part (9) and the second cutting edge (12) is arranged on a second cutting part (11 ).

7. A forming mould (5) according to claim 6, wherein the first cutting part (9) and the second cutting part (11 ) are replaceable.

8. A forming mould (5) according to any of claims 5 to 7, wherein the distance between the first cutting edge (10) and the second cutting edge (12) is greater than 0,10 mm when the forming mould is in an intermediate state (28).

9. A cellulose product (1 ) formed from a cellulose blank structure (2) where the cellulose blank structure (2) comprises a dry-formed cellulose fibres layer (3), c h a r a c t e r i z e d i n that the cellulose product (1 ) comprises an opening (4) that is perpendicular to the pressing direction in which the cellulose product (1 ) is pressed.

10. A cellulose product (1 ) according to claim 9, wherein the opening (4) is provided in a side wall of the cellulose product (1 ).

11. A cellulose product (1 ) according to claim 9, wherein the opening (4) is provided in an upper part (23) of the cellulose product (1 ).

12. A cellulose product (1 ) according to claim 9 to 11 , wherein the cellulose product (1 ) is a clamshell tray having a lower part (21 ) and a lid (23), where the lower part comprises a rim section (22), and where the lid (23) is provided with a tab (24), where the rim section (22) is provided with an opening (25) arranged to cooperate with the tab (24) to provide a locking function for the clamshell tray.

13. A cellulose product (1 ) according to claim 12, wherein the lid (23) is provided with at least one ventilation opening (26).

14. A cellulose product (1 ) according to claim 9, wherein the cellulose product (1 ) is a coffee lid.

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