A method for producing a cellulose product and a cellulose product

Abstract

A cellulose three-dimensional deep drawn cellulose Dry Moulded Fibre (DMF) product (1) and a method for producing a three-dimensional deep drawn cellulose Dry Moulded Fibre (DMF) product (1) having a bottom portion (3) and a side wall portion (4) from a cellulose blank structure (2) wherein the method comprises the steps of; heating a forming mould (7) to a forming temperature in the range of 100°C to 300°C; arranging the cellulose blank structure in the forming mould (7); and forming the cellulose product (1) from the cellulose blank structure (2) in the heated forming mould (7), by pressing the cellulose blank structure (2) with a forming pressure between 1 to 100 MPa, where the forming mould (7) comprises a first mould part (8) and a second mould part (9), and where a distance (D1) between a first side wall part (12) of the first mould part (8) and a second side wall part (13) of the second mould part (9) at an upper mould part (17) of the forming mould (7) in a closed state is greater than a distance (D2) between the first side wall part (12) of the first mould part (8) and the second side wall part (13) of the second mould part (9) at a lower mould part (17) of the forming mould (7) in the closed state.

Description

[0001] A METHOD FOR PRODUCING A CELLULOSE PRODUCT AND A

[0002] CELLULOSE PRODUCT

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to a method for producing a three-dimensional shaped dry moulded fibre (DMF) cellulose product from a cellulose material.

[0005] BACKGROUND

[0006] Cellulose fibres are often used as raw material for producing or manufacturing various products. Products formed of cellulose fibres can be used in many different situations where there is a need for having sustainable products of essentially non-flat shapes. An 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. Such products are often laminated with different films in order for the product to withstand liquids, grease, heat etc.

[0007] Cellulose fibres are obtained by separating the cellulose fibres from a pulp derived from e.g. wood or other plants. Pulp is a lignocellulosic fibrous material that can be prepared either mechanically or chemically by separating cellulose fibres from wood or other plants. Wood pulp is e.g. obtained by grinding timber or trees in some kind of mill, e.g. a disc refiner, where the wood is ground to wood pulp. The pulp contains water, cellulose fibres, lignin and hemicelluloses. For some products, e.g. where the strength is not a key factor and / or when a low price is important, a lignocellulosic material, i.e. fibres where the lignin is not removed, can be used. There are different processes that can separate wood fibres. When preparing mechanical pulp, thermomechanical pulp or chemo-thermomechanical pulp, the fibres are separated but the lignin is not removed from the cellulose fibres. In a chemical pulp process, the lignin and some of the hemicelluloses is removed more or less completely from the pulp, leaving substantially pure cellulose fibres.

[0008] One material commonly used for cellulose fibre products is wet moulded pulp. The pulp used for wet forming is often obtained from recycled paper boards and newspaper, where the cellulose fibres comprise lignin. This lowers the cost. Wet moulded pulp has the advantage of being considered as a sustainable packaging material, since it is produced from biomaterials and can often be recycled or composted 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, which is costly. Further, this method requires a large quantity of water. 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.

[0009] Another known method for producing products from cellulose material is by pressing loose cellulose fibres in a dry state, known as Dry Moulded Fibres (DMF). These products can be made in a cost-efficient way without using water as a cellulose fibre bearer and with a reduced energy need. Such products are well suited to replace disposable plastic products.

[0010] In a DMF process, cellulose fibres are formed with a forming pressure between 10-20 MPa in a regular compression mould. In such forming, the cellulose fibres arranged in a cellulose blank structure are drawn apart somewhat when a non-flat shape is created. If the shape is complicated or the height is large, the cellulose blank structure may be torn, which makes it difficult to produce deep drawn dry moulded fibre products. Since the cellulose blank structure does not float or stretch, it is difficult to fold and press a cellulose blank structure into the forming mould such that the cellulose blank structure is evenly distributed in the forming mould, which may cause irregularities in the thickness of the side walls and which may cause the tissue to wrinkle.

[0011] One method that can be used to facilitate the moulding of deep drawn products is to precut the cellulose blank structure to a shape that corresponds to the actual forming mould. Overlapping parts of the cellulose blank structure can be cut away before the cellulose blank structure is positioned in the forming mould, such that only small edge portions overlap. The overlapping edge portions are then bounded to each other during the moulding of the cellulose product.

[0012] This method may work well for some products, but each cut-out cellulose blank structure must be handled individually, which requires a more complicated feeding system to the forming mould. Further, the excess portion next to the rim of the cellulose product that is cut away to provide a clean rim must also be handled individually and cannot be recycled in the same process as the cellulose blank structure mat.

[0013] There is thus a need for improved sustainable cellulose products, where the cellulose products are having improved mechanical and chemical properties, can be manufactured with high precision, and where the production is costefficient and rational. SUMMARY

[0014] An object of the present disclosure is to provide a method for producing a cellulose product where the previously mentioned problems are avoided. 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. Another object of the present disclosure is to provide a three- dimensional shaped cellulose product.

[0015] The disclosure concerns a method for producing a deep drawn three- dimensional cellulose dry moulded fibre (DMF) product having a bottom portion and a side wall from a cellulose material, wherein the method comprises the steps of; heating a forming mould to a forming temperature in the range of 100°C to 300°C; arranging the cellulose material in the forming mould; and forming the cellulose product from the cellulose material in the heated forming mould by pressing the cellulose material with a forming pressure between 1 to 100 MPa, where the forming mould comprises a first mould part and a second mould part, and where a distance between a first side wall part of the first mould part and a second side wall part of the second mould part at an upper mould part of the forming mould in a closed state is greater than a distance between the first side wall part of the first mould part and the second side wall part of the second mould part at a lower mould part of the forming mould in the closed state.

[0016] Advantages with these features are that the method provides an efficient manufacturing process for deep drawn cellulose DMF products with improved mechanical and chemical properties. The advantage with this method is that deep drawn cellulose products can be moulded from a cellulose blank structure arranged as a continuous mat, where the mat is forwarded to the forming mould in an intermittent manner. The forming mould comprises a first mould part and a second mould part between which the cellulose product is formed. The forming mould comprises a bottom part arranged between a first bottom part of the first mould part and a second bottom part of the second mould part. The bottom portion of the cellulose product is formed between the first bottom part and the second bottom part. The distance between the first bottom part and the second bottom part defines the thickness of the bottom portion of the cellulose product, and is preferably relatively equal. Some smaller regions may have a different thickness, e.g. to provide a marking, a rotational stop position, etc. The thickness of the bottom portion may e.g. be in the region between 0,4-1 ,2 mm thick.

[0017] The forming mould further comprises a side wall part arranged between a first side wall part of the first mould part and a second side wall part of the second mould part. The side wall portion of the cellulose product is formed between the first side wall part and the second side wall part. The distance between the first side wall part and the second side wall part defines the thickness of the side wall portion of the cellulose product. In the inventive method, the distance between the first side wall part and the second side wall part differs over the height of the forming mould.

[0018] At a lower mould part of the forming mould, close to the bottom part of the forming mould, the distance between the first side wall part and the second side wall part is in one example equal to the distance between the first bottom part and the second bottom part. In this example, a lower portion of the cellulose product will have the same thickness as the bottom portion of the cellulose product. Some variation in the distance is possible, but with a given weight of the cellulose blank structure, a predefined thickness is obtained. In one example, a cellulose blank structure having a weight of 400 GSM gives a suitable thickness of e.g. between 0.4-0.9 mm in order to obtain a desired strength of the cellulose product.

[0019] The distance between the first side wall part and the second side wall part increases towards the upper mould part of the forming mould. The distance variation is preferably linear. At the upper mould part, the distance is the greatest, and may e.g. be twice as large as the distance at the lower mould part. The distance between the first side wall part and the second side wall part is measured in a horizontal direction, and may be measured when the forming mould is in a closed state.

[0020] The purpose of having a greater distance between the first side wall part and the second side wall part at the upper mould part is to be able to fit more cellulose material between the first mould part and the second mould part. When a cellulose product is formed from a flat cellulose blank structure, the cellulose blank structure must be pushed down into the forming mould. Since the cellulose blank structure does not float or can be drawn apart in a controlled manner, it is difficult to push down a flat cellulose blank structure into a deep mould. One problem is that there will be excessive material at the upper portion of the cellulose product when compared to the lower portion. For a square cup, there will be twice the required amount of cellulose material at the upper portion of the cup. For a circular cup, the same applies, depending on the width and height of the cup. By pre-cutting the cellulose blank structure such that the excessive material is cut away, the cellulose material can be pushed into a forming mould having the same distance between the first mould part and the second mould part, and a cellulose product can be formed in the forming mould. If the cellulose blank structure is not pre-cut, the excessive material at the upper portion will prevent the first mould part to enter deep enough into the second mould part such that the cellulose product is not formed correctly with the applied forming pressure.

[0021] It would be possible to raise the forming pressure such that the excessive material is compressed to a greater extent, and such that the first mould part can enter deep enough into the second mould part to also press the bottom portion of the cellulose product with a sufficiently high forming pressure. However, a higher forming pressure adds a cost to the cellulose product. This means that in the same press with the same rated forming pressure, fewer and / or smaller cellulose products can be produced with the same forming pressure. There is thus a need to optimize the used forming pressure to the desired properties of the cellulose product. It has been shown that a forming pressure between 4-20 MPa will provide a deep drawn cellulose product with a sufficient high strength when a forming mould with a varying distance between the side wall parts is used.

[0022] By using a forming mould where the distance varies between the first mould part and the second mould part, a flat cellulose blank structure can be pushed into the forming mould and the forming mould will be able to form a cellulose product without the problems that arises with a forming mould having the same distance between the first mould part and the second mould part. The side wall portion of the cellulose product will thus have a varying thickness corresponding to the distance between the first mould part and the second mould part, with a similar density and thus strength over the complete side wall portion. By adapting the distance between the first mould part and the second mould part to the size and shape of the cellulose product, it is possible to produce deep drawn cellulose products without having to pre-cut the cellulose blank structure.

[0023] In one example, the distance between the first side wall part of the first mould part and the second side wall part of the second mould part at the upper mould part is at least 1 ,7 times greater than the distance between the first side wall part of the first mould part and the second side wall part of the second mould part at the lower mould part.

[0024] In another example, the distance between the first side wall part of the first mould part and the second side wall part of the second mould part at the upper mould part is at least 2,0 times greater than the distance between the first side wall part of the first mould part and the second side wall part of the second mould part at the lower mould part, and may be up to 2,6 times greater.

[0025] In one example, a draw ratio defined as the height of the cellulose product divided with the smallest width of the cellulose product is less than 0,8. The draw ratio may be less than 0,7. In one example, a draft angle, i.e. the inclination, of the side wall portion is greater than 10 degrees in relation to a centre axis of the cellulose product.

[0026] In one example, a deep drawn cellulose product in the form of a circular container having a width of around 8 cm and a height of around 6 cm is produced. The width at the lower portion is in this example 7 cm and the width at the upper portion is 9 cm. The thickness of the bottom portion is here 0,5 mm and the thickness of the lower portion of the side wall is also 0,5 mm. The thickness of the upper portion of the side wall is here 1 ,0 mm. Other dimensions and thickness variations are of course possible depending e.g. on the actual cellulose product and the weight of the cellulose blank structure. The deep drawn cellulose container can in this example be formed in a forming mould having a first mould part and a second mould part, where the first mould part may be a male mould part and the second mould part may be a female mould part. Both the first mould part and the second mould part are made from steel or another stiff material such that they are non-flexible. The forming mould may also comprise one or more sections with a solid flexible material, such as silicone, at some regions of the forming mould.

[0027] When the flat cellulose blank structure is pushed down into the second mould part by the first mould part, the cellulose blank structure arranged at the first bottom part of the first mould part will retain its shape and position in the final cellulose product. The cellulose blank structure arranged around the first bottom part will be folded such that it will fit into the second side wall part of the second mould part. Since there is excessive cellulose material for the side wall portion, some of the cellulose material will be folded and will overlap. By lowering the first mould part further into the second mould part, the cellulose container will be formed with a forming pressure between 1 -100 MPa, preferably between 4-20 MPa. With the greater distance between the first mould part and the second mould part at the upper mould part of the forming mould, all sections of the cellulose container will be formed with substantially the same forming pressure, since the excessive cellulose material will not prevent the first mould part to reach its predefined moulding position in which a substantially equal forming pressure is applied to the cellulose blank structure.

[0028] In another example, a small deep drawn coffee pod is produced. The height of the coffee pod is in this example 25 mm, the width at the lower portion is 23 mm and the width at the upper portion of the side wall is 30 mm. The coffee pod also comprises a rim portion extending outwards from the upper portion of the side wall. The thickness of the side wall at the lower portion is 0.8 mm and the thickness of the side wall at the upper portion is 1 ,6 mm. The dimensions of the forming mould correspond to these measures of the coffee pod. The thickness of the rim section is 1 ,0 mm. The bottom portion of the coffee pod may have one or more indentations, grooves or the like.

[0029] The forming mould is preferably also provided with cutting means that are arranged to cut out the cellulose product from the cellulose blank structure when the cellulose product has been formed. This will give the cellulose product a clean-cut rim section. The cutting means is arranged in the forming mould and may be arranged to perform either shear cutting or burst cutting.

[0030] It is also possible to cut a pattern outside of the product section of the cellulose blank structure. The purpose of the cut pattern is to allow the product section to move freely such that it can be pushed into the forming mould without being restricted by the remaining cellulose blank structure. This is especially of advantage when a multi-cavity forming mould is used, in which several cellulose products are formed at the same time. With no cut pattern, there will be competition between the product sections of each cellulose product. By cutting a pattern e.g. in a maze-shape, a labyrinth shape or similar, the different product sections can move independently from each other, such that all product sections can be pushed into their respective forming mould.

[0031] The advantage of such a cut pattern is that all sections of the complete cellulose blank structure are interconnected to each other, which will simplify the handling of the cellulose blank structure remaining when all products have been formed. In this way, there is no need to handle separate small cut-out parts. The remaining cellulose blank structure can e.g. be fed to a mill such that the remaining cellulose blank structure can be recycled and thus be used to form a new air-laid cellulose blank structure. If two forming moulds are used next to each other, the cellulose blank structure can also be split in half in order to avoid competition between the two forming moulds.

[0032] The cellulose product is formed in a forming mould which in one example comprises a first positive mould part and a second negative mould part. The forming mould parts are stiff and non-flexible, preferably made from steel or another stiff material, and may be heated to the desired forming temperature. The forming mould is in one example heated with integrated heating elements, preferably electrical heating elements, but also liquid heating is possible. The forming mould is preferably closed, such that the cellulose material is completely enclosed in the mould during moulding of the cellulose DMF product.

[0033] In the shown example, the starting material is an air-laid cellulose blank structure as is commonly used for dry moulded fibre products. In this example, the cellulose material is a cellulose blank structure comprising loose cellulose fibres having a weight of the cellulose blank structure that is between 400-600 GSM (grams per square metre). In the description, a dry-formed cellulose blank structure is sometimes referred to as an air-laid cellulose blank structure. With such a material, a DMF product with a density between 1 ,00-1 ,20 g / cm3can be obtained when moulded with a forming pressure below 100 MPa, and in one example between 4-20 MPa.

[0034] The cellulose material is preferably made from chemical pulp where most of the lignin and hemicellulose has been removed. The cellulose material may also comprise some additives, where the additives are used to decrease the liquid and / or gas permeability of the cellulose product and to increase the resistance to e.g. hot and cold liquids, grease, oil etc. Such additives may also be applied to the surface of the cellulose product after the cellulose product is formed. In one example, the cellulose material comprises at least 90% cellulose fibres by dry weight. The additives used are additives adapted to alter the permeability of the cellulose material, and should not function as a binder material to bind the cellulose material together. By using untreated cellulose fibres, the cellulose fibres are bound together by hydrogen bonds and Van der Vaals bonds. Additives may decrease the possibility for hydrogen bonds, and binder material will definitely reduce the possible hydrogen bonds.

[0035] The cellulose DMF product is formed in the forming mould during a cycle time period in the range of 0,1 to 10 seconds, and preferably less than 5,0 seconds. A suitable holding time for the product in the forming mould is less than a second, and may be e.g. 0,3-0, 7 seconds. The holding time together with the forming temperature and the forming pressure are important parameters in the forming of the cellulose product.

[0036] BRIEF DESCRIPTION OF DRAWINGS

[0037] The disclosure will be described in greater detail in the following, with reference to the attached drawings, in which

[0038] Fig. 1 shows schematically a method for producing a cellulose DMF product from a cellulose blank structure according to the disclosure,

[0039] Figs. 2a-b show schematically an example of a forming mould to be used for producing a cellulose DMF product from a cellulose blank structure according to the disclosure,

[0040] Fig. 3 show schematically a further example of a forming mould to be used for producing a cellulose DMF product from a cellulose blank structure according to the disclosure,

[0041] Fig. 4 shows schematically an example of a cellulose DMF product according to the disclosure, Fig. 5 shows schematically a further example of a cellulose DMF product according to the disclosure, and

[0042] Fig. 6 shows schematically a further example of a cellulose DMF product according to the disclosure.

[0043] DESCRIPTION OF EXAMPLE EMBODIMENTS

[0044] 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.

[0045] In the present detailed description, a method for producing a deep drawn cellulose DMF product from a cellulose material will be described. The method is suitable for different products referred to as deep drawn products, such as cups, pods, spoons etc, where the draw ratio is less than 0,8. The draw ratio is defined as the ratio between the width of a product and the height of the product. A cup with a maximal diameter of 95 mm and a height of 76 mm has a draw ratio of 0.8. A draft angle a, i.e. the inclination angle of a side wall of the cup should in one example be greater than 10 degrees when compared to a centre axis 33 of a cellulose product, where the side wall is inclined outwards form the centre axis. These values are estimates and may differ some depending on the actual cellulose product, but can be used as a rule of thumb. The draft angle a may e.g. be reduced some for a smaller product such as a coffee pod or the like.

[0046] The cellulose material used to form the cellulose DMF product is a substantially pure cellulose material containing cellulose where most of the lignin and hemicellulose are removed. Such a material is produced from chemical pulp where most of the lignin and the hemicellulose has been removed. Additives may also be added to the cellulose material, where the additives are used to decrease the liquid and / or gas permeability of the cellulose product and to increase the resistance to e.g. hot and cold liquids, grease, oil etc. In one example, the cellulose material comprises at least 90% cellulose fibres by dry weight and at the most 10% additives by weight. The cellulose material will also comprise some water, e.g. between 6% to 20% by weight. Water is not seen as an additive, it is necessary to create hydrogen bounds between the cellulose fibres but will evaporate when the cellulose product is heated in an oven.

[0047] When forming the cellulose blank structure in an air-laid process, the cellulose fibres are carried and formed to the cellulose blank 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 material 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 the dry-formed cellulose blank structure may have a dryness that is mainly corresponding to the ambient humidity in the atmosphere surrounding the cellulose blank structure. Additional water may be added to the cellulose blank structure, such that a water content of between 6 to 20% by weight is reached. A lower water content is possible, but may be difficult to reach due to the moisture in the ambient air.

[0048] In Fig. 1 , a method for manufacturing a deep drawn cellulose DMF product in a cellulose product forming apparatus 20 is schematically shown, where a cellulose blank structure 2 is dry formed in a dry forming unit 21 , arranged in a forming mould 7, heated to a forming temperature and pressed in the forming mould 7 with a forming pressure. In a first step, the cellulose blank structure 2 is dry formed in the dry forming unit 21. The dry forming unit 21 is in Fig. 1 schematically illustrated with a dotted line and comprises a separating unit 22, a forming box 23, a forming wire 24 and a compacting unit 25. The cellulose blank structure 2 is in the method formed into a deep drawn three-dimensional cellulose product 1 .

[0049] In the separating unit 22, cellulose is separated into detached cellulose fibres.

[0050] The cellulose material used in the separating unit 22 is preferably a substantially pure cellulose material, such as for example fluff pulp or the like, containing a high degree of cellulose fibres. As an example, the separating unit 22 may be a conventional hammer mill. Standard virgin fluff pulp may be used as cellulose raw material and can for example be purchased on the open market in rolls 26. In Fig. 1 , a roll 26 of fluff pulp is used as raw material, which is fed into the separating unit 22.

[0051] The cellulose fibres 27 are arranged onto the forming wire 24 in a conventional way within the dry forming unit 21 . The detached cellulose fibres 27 is drawn from the separating unit 22 by a centrifugal fan 28 and blown into the forming box 23 arranged above the forming wire 24. A vacuum box 29 may be arranged underneath the upper part of the forming wire 24. The forming box 23 may comprise a number of fibre separating rollers 30 arranged in the forming box housing to distribute the cellulose fibres 27 evenly onto the forming wire 24. The cellulose fibres 27 are drawn by the vacuum in the vacuum box 29 onto the forming wire 24 in order to form a cellulose blank structure which is transported by the forming wire 24 to the compacting unit 25. The forming wire 24 may be arranged in a conventional way as an endless belt made for example from a woven mesh structure, which endless belt can be moved continuously with a constant speed when forming the cellulose blank structure. The density of the cellulose blank structure may be chosen so that it is suitable for the cellulose product to be formed.

[0052] In order to form the cellulose blank structure 2, the cellulose fibres 27 are preferably compacted or calendared in the compacting unit 25. As an example, a compacting roll may be arranged above the forming wire, so that the compacting roll is applying a compacting pressure on the cellulose blank structure formed in the dry forming process. In this way, the cellulose blank structure 2 is formed as a continuous cellulose blank structure 2 in the dry forming unit 21. The dry forming of the cellulose blank structure 2 may take place as a separate process step, in which the cellulose blank structure may be stacked in sheets or arranged as a rolled web, before forming of the cellulose product. As an alternative, the dry forming of the cellulose blank structure 2 may be part of a continuous process, as shown in Fig. 1 , in which the cellulose product is manufactured in the cellulose product forming apparatus.

[0053] In order to form the cellulose product, the cellulose blank structure 2 is arranged in the forming mould 7, where the cellulose blank structure 2 thereafter is heated to a forming temperature in the range of 100°C to 300°C and pressed in the forming mould 7 with a forming pressure of at least 1 MPa. Tests have shown that suitable pressure levels may be in the range of 1 -100 MPa, and may be in the range between 4-20 MPa. The heating of the cellulose blank structure 2 is preferably taking place in the forming mould 7 when being pressed by the pressing unit 32.

[0054] When pressing the cellulose fibres with a forming pressure of at least of 1 MPa with a forming temperature in the range of 100°C to 300°C, the cellulose fibres 27 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 27 when being pressed at a specific forming pressure. With forming temperatures above 100°C together with a forming pressure of 1-100 MPa, the cellulose fibres 27 will be strongly bonded to each other with hydrogen bonds. A higher forming temperature will increase the fibril aggregation, water resistance, Young’s modulus and the mechanical properties of the final cellulose product. A high forming pressure is important for fibril aggregation between the cellulose fibres 27 in the cellulose product. At temperatures higher than 300°C, the cellulose fibres 27 will 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.

[0055] The cellulose blank structure 2 may be arranged into the forming mould 7 in any suitable way, and as an example, the cellulose blank structure 2 may be manually arranged in the forming mould 7. Another alternative is to arrange a feeding unit 31 for the cellulose blank structure 2, which is transporting the cellulose blank structure 2 to the forming mould. The feeding unit could for example be a conveyor belt, an industrial robot, or any other suitable manufacturing equipment. If the dry forming of the cellulose blank structure 2 is part of a continuous manufacturing process in which the cellulose product is produced, as shown in Fig. 1 , the cellulose blank structure may be fed to the forming mould 7 from the dry forming unit 21 with the forming wire 24. More specifically, the cellulose blank structure 2 could be intermittently fed to the forming mould 7 by a feeding unit 31 if the forming wire 24 is moving with a constant speed through the dry forming unit 21 and the forming of the cellulose products in the forming mould 7 is taking place in intermittent process steps. The cellulose blank structure may, as an example, be intermittently fed to the forming mould via a feeding unit 31 in the form of a buffer zone arrangement, as shown in Fig. 1 .

[0056] As described above, the cellulose product 1 is manufactured from cellulose fibres 27, and the cellulose product may comprise at least 90 weight percent cellulose fibres. Sizing agents or other suitable additives may be applied to the cellulose fibres 27 to increase the hydrophobic properties, mechanical strength and / or other properties of the cellulose blank structure 2. As an example, the cellulose product may comprise 90-98 weight percent cellulose fibres and 2- 10 weight percent other substances, such as starch, sizing agents, and / or other suitable additives and substances. In order to secure that the cellulose product can be recycled after use, the added substances may be biodegradable or suitable for recycling.

[0057] As described above in relation to Fig. 1 , the cellulose product forming apparatus 20 comprises a dry forming unit 21 for forming the cellulose blank structure 2 and a forming mould 7 for forming the cellulose product. The feeding unit 31 is arranged after the dry forming unit so that the cellulose blank structure 2 can be intermittently fed to the forming mould 7 by the feeding unit 31.

[0058] Fig. 2a shows an example of a forming mould 7 to be used to form a deep draw cellulose DMF product 1 in an open state, and Fig. 2b shows an example of the forming mould 7 in a closed state. The forming mould is shown as a cut side view. The forming mould 7 comprises a first mould part 8 and a second mould part 9 between which the cellulose product 1 is formed. In this example, the first mould part 8 is a male mould part arranged as an upper mould part, and the second mould part 9 is a female mould part arranged as a lower mould part. In the shown example, the first mould part will be moved down and up by the pressing unit 32 during the forming of the cellulose product.

[0059] The forming mould 7 comprises a bottom part 14 arranged between a first bottom part 10 of the first mould part 8 and a second bottom part 11 of the second mould part 9. The bottom portion 3 of the cellulose product 1 is formed between the first bottom part 10 and the second bottom part 11. The distance between the first bottom part and the second bottom part defines the thickness of the bottom portion 3 of the cellulose product, and is preferably relatively equal. Some smaller regions may have a different thickness, e.g. to provide a marking, a rotational stop position, etc. The thickness of the bottom portion may e.g. be in the region between 0,4 - 1 ,2 mm thick.

[0060] The forming mould 7 further comprises a side wall part 15 arranged between a first side wall part 12 of the first mould part 8 and a second side wall part 13 of the second mould part 9. The side wall portion 4 of the cellulose product 1 is formed between the first side wall part 12 and the second side wall part 13. The distance between the first side wall part and the second side wall part defines the thickness of the side wall portion 3 of the cellulose product. In the inventive method, the distance between the first side wall part and the second side wall part differs over the height of the forming mould 7. At a lower mould part 16 of the forming mould 7, close to the bottom part 14 of the forming mould 7, the distance D2 between the first side wall part 12 and the second side wall part 13 is in one example equal to the distance between the first bottom part and the second bottom part. In this example, a lower portion 6 of the cellulose product 1 will have the same thickness as the bottom portion 3 of the cellulose product. Some variation in the distance is possible, but with a given weight of the cellulose blank structure, a predefined thickness is obtained. In one example, a cellulose blank structure having a weight of 400 GSM gives a suitable thickness of e.g. between 0.4-0.9 mm in order to obtain a desired strength of the cellulose product.

[0061] The distance between the first side wall part 12 and the second side wall part 13 increases towards the upper mould part 17 of the forming mould 7. The distance variation is preferably linear. At the upper mould part 17, the distance D1 is the greatest, and may e.g. be twice as large as the distance D2 at the lower mould part 16 when the forming mould is in a closed state.

[0062] Figure 2b schematically shows an example where the distance D1 between the first side wall part 12 of the first mould part 8 and the second side wall part 13 of the second mould part 9 at the upper mould part 17 of the forming mould 7 in a closed state is greater than the distance D2 between the first side wall part 12 of the first mould part 8 and the second side wall part 13 of the second mould part 9 at the lower mould part 17 of the forming mould 7 in a closed state.

[0063] According to one example, D1 is at least 1 ,7 times greater than D2, i.e. D1 divided by D2 is at least 1 ,7.

[0064] According to another example, D1 is at least 2,0 times greater than D2, i.e. D1 divided by D2 is at least 2,0, and may be up to 2,6.

[0065] The purpose of having a greater distance at the upper mould part 17 is to be able to fit more cellulose material between the first mould part 8 and the second mould part 9. When a cellulose product is formed from a flat cellulose blank structure, the cellulose blank structure must be pushed down into the forming mould 7. Since the cellulose blank structure does not float or can be drawn apart in a controlled manner, it is difficult to push down a flat cellulose blank structure into a deep mould. One problem is that there will be excessive material at the upper portion 5 of the cellulose product 1 when compared to the lower portion 6. For a square cup, there will be twice the required amount of cellulose material at the upper portion of the cup. For a circular cup, a similar ratio applies, depending on the width and height of the cup. By pre-cutting the cellulose blank structure such that the excessive material is cut away, the cellulose material can be pushed into a forming mould having the same distance between the first mould part and the second mould part, and a cellulose product can be formed in the forming mould. If the cellulose blank structure is not pre-cut, the excessive material at the upper portion will prevent the first mould part to enter deep enough into the second mould part such that the cellulose product is not formed correctly with the applied forming pressure.

[0066] It would be possible to raise the forming pressure such that the excessive material is compressed to a greater extent, and such that the first mould part can enter deep enough into the second mould part to also press the bottom portion of the cellulose product with a sufficiently high forming pressure. However, a higher forming pressure adds a cost to the cellulose product. This means that in the same press with the same rated forming pressure, fewer and / or smaller cellulose products can be produced with the same forming pressure. There is thus a need to optimize the used forming pressure to the desired properties of the cellulose product. It has been shown that a forming pressure between 4-20 MPa will provide a deep drawn cellulose product with a sufficient high strength when a forming mould with a varying distance between the side wall parts is used and when the cellulose product is formed from a flat cellulose blank structure.

[0067] By using a forming mould where the distance varies between the first mould part and the second mould part, a flat cellulose blank structure can be pushed into the forming mould and the forming mould will be able to form a cellulose product without the problems that arises with a forming mould having the same distance between the first mould part and the second mould part. The side wall portion of the cellulose product will thus have a varying thickness corresponding to the distance between the first mould part and the second mould part, with a similar density and thus strength over the complete side wall portion. By adapting the distance between the first mould part and the second mould part to the size and shape of the cellulose product, it is possible to produce deep drawn cellulose DMF products without having to pre-cut the cellulose blank structure.

[0068] Fig. 3 show a further example of a forming mould 7 to be used to form a deep draw cellulose DMF product 1 . The forming mould 7 comprises in this example a support plate 34 arranged above the cellulose blank structure 2 and above the second mould part 9. The support plate 34 is provided with an opening 35 which is slightly larger than the outer edges of the cellulose product that is to be moulded. For a circular container, the diameter of the opening may e.g. be 5-10% larger than the outer diameter of the cellulose product. It is important that the opening is larger than the first mould part 8, such that the support plate does not interfere with the moulding of a cellulose product. The purpose of the support plate is to create smaller and more evenly spread folds in the cellulose blank structure when the cellulose blank structure is pushed down into the second mould part. In this way, the cellulose blank structure will be distributed more evenly in the upper mould part 17 of the forming mould 7, which will improve the production of deep drawn cellulose products.

[0069] Without a support plate, the cellulose blank structure may fold in several undefined places around the forming mould, which will cause uneven material distribution which results in an uneven wall thickness. If a cellulose blank structure is allowed to fold freely when the cellulose blank structure is pushed down into the forming mould when a deep drawn cellulose product is produced, the cellulose blank structure will start to fold at some positions. For a deep drawn product, the small folds of the material at some positions will quickly escalate into a big fold at some positions of the cellulose blank structure, as well as several smaller folds. With a support plate, the free folding of the cellulose blank structure is held back and the folds are not allowed to grow, providing a larger amount of small, evenly distributed folds spread out around the cellulose product.

[0070] A few large folds may affect both product specification, product appearance and product performance. In a steel-steel tool, where the upper mould part and the lower mould art are both made of steel, this uneven thickness, where a fold may contain three times as much material as an unfolded area, may result in over-compression of the cellulose material at the folded positions and little to no compression at unfolded positions, resulting in cellulose products not meeting specifications.

[0071] The support plate 35 is arranged above the cellulose blank structure 2. The distance between the support plate and the cellulose blank structure will depend e.g. on the actual cellulose product, the weight, i.e. the GSM, of the cellulose blank structure and the precompression of the cellulose blank structure. The distance will further depend on the size and shape of the forming mould, e.g. the draw ratio, the height and the draft angle a.

[0072] The support plate may also be treated in order to minimize the friction between the support plate and the cellulose blank structure. The support plate may e.g. be treated with a low friction layer of some sort, e.g. Teflon, or the surface of the support plate may be etched with a low friction pattern.

[0073] Fig. 4 shows an example of a deep drawn cellulose DMF product 1 in the form of a circular container having a width of around 80 mm and a height of 76 mm, e.g. a yogurt cup. The circular container is shown as a cut side view. In this example, the cup-shaped product is circular with a frustoconical shape, but other shapes are possible, such as an elliptical shape, a rectangular shape, a shape with six, eight or more side walls, etc. The width at the lower portion 6 is in this example 75 mm and the width at the upper portion 5 is 95 mm. This gives a draw ration of 0,8. The thickness of the bottom portion 3 is here 0,5 mm and the thickness of the lower portion 6 of the side wall is also 0,5 mm. The thickness of the upper portion 5 of the side wall is here 1 ,0 mm. Other dimensions and thickness variations are of course possible depending e.g. on the actual cellulose product and the weight of the used cellulose blank structure. The deep drawn cellulose container can in this example be formed in a forming mould 7 having a first mould part 8 and a second mould part 9, where the first mould part may be a male mould part and the second mould part may be a female mould part. Both the first mould part and the second mould part are made from steel or another stiff material such that they are nonflexible.

[0074] Figure 4 schematically shows that the cellulose product comprises the bottom portion 3 and the side wall portion 4, wherein the upper portion 5 of the side wall portion 4 has a thickness D11 thicker than a thickness D22 of the lower portion 6 of the side wall portion 4.

[0075] According to one example, the upper portion 5 of the side wall portion 4 is at least 1 ,7 times thicker than the lower portion (6) of the side wall portion 4, i.e. D11 divided by D22 is at least 1 ,7.

[0076] According to one example, the upper portion 5 of the side wall portion 4 is at least 2,0 times thicker than the lower portion 6 of the side wall portion 4, i.e. D11 divided by D22 is at least 2,0, and may be up to 2,6.

[0077] When the flat cellulose blank structure 2 is pushed down into the second mould part 9 by the first mould part 8, the cellulose blank structure arranged at the first bottom part 10 of the first mould part 8 will retain its shape and position in the final cellulose product. The cellulose blank structure arranged around the first bottom part 10 will be folded such that it will fit into the second side wall part of the second mould part. Since there is excessive cellulose material for the side wall portion 4, some of the cellulose material will be folded and will overlap. By lowering the first mould part 8 further into the second mould part 9, the cellulose container 1 will be formed with a forming pressure between 1- 100 MPa, preferably between 4-20 MPa. With the greater distance between the first mould part and the second mould part at the upper mould part of the forming mould, all portions of the cellulose container will be formed with substantially the same forming pressure, since the excessive cellulose material will not prevent the first mould part to reach its predefined moulding position in which a substantially equal forming pressure is applied to the cellulose blank structure.

[0078] Fig. 5 shows another example of a deep drawn cellulose DMF product 1 , here as a small deep drawn coffee pod. The coffee pod is shown as a cut side view. The height of the coffee pod is in this example 24 mm, the width at the lower portion 6 is 23 mm and the width at the upper portion 5 of the side wall is 30 mm. This gives a draw ration of 0,8. The coffee pod also comprises a rim portion 18 extending outwards from the upper portion 5 of the side wall 4. The thickness of the side wall at the lower portion is 0.8 mm and the thickness of the side wall at the upper portion is 1 ,6 mm. The dimensions of the forming mould correspond to these measures of the coffee pod. The thickness of the rim section is 1 ,0 mm. The bottom portion 3 of the coffee pod may have one or more indentations, grooves or the like.

[0079] Fig. 6 shows another example of a deep drawn cellulose DMF product 1 , here as a small deep drawn spoon that may e.g. be used for washing powder. The spoon is shown as a cut side view. The spoon is in this example rectangular having a bottom surface with a width of 25 mm and a length of 45 mm. For a rectangular deep drawn cellulose DMF product, the draw ration is calculated with the smallest width value. Here, the draw ration is approximately 0,7. The spoon is further provided with a handle 19. The height of the spoon is in this example 35 mm. The thickness of the side wall at the lower portion 6 is 0,7 mm and the thickness of the side wall at the upper portion 5 is 1 ,5 mm. The dimensions of the forming mould correspond to these measures of the spoon.

[0080] The thickness of the handle is here 1 ,0 mm.

[0081] The forming mould 7 is preferably also provided with cutting means that are arranged to cut out the cellulose product 1 from the cellulose blank structure 2 when the cellulose product is being formed in the forming mould 7. This will give the cellulose product a clean-cut rim portion. The cutting means is arranged in the forming mould and may be arranged to perform either shear cutting or burst cutting.

[0082] It is also possible to cut a pattern outside of the product section of the cellulose blank structure. The purpose of the cut pattern is to allow the product section to move freely such that it can be pushed into the forming mould without being restricted by the remaining cellulose blank structure. This is especially of advantage when a multi-cavity forming mould is used, in which several cellulose products are formed at the same time in a plurality of forming moulds. With no cut pattern, there will be competition between the product sections of each cellulose product between the different forming moulds. By cutting a pattern e.g. in a maze-shape, a labyrinth shape or similar, the different product sections can move independently from each other, such that all product sections can be pushed into their respective forming mould.

[0083] The advantage of such a cut pattern is that all sections of the complete cellulose blank structure are interconnected to each other, which will simplify the handling of the cellulose blank structure remaining when all products have been formed. In this way, there is no need to handle separate small cut-out parts. The remaining cellulose blank structure can e.g. be fed to a mill such that the remaining cellulose blank structure can be recycled and thus be used to form a new air-laid cellulose blank structure. If two forming moulds are used next to each other, the cellulose blank structure can also be split in half in order to avoid competition between the two forming moulds. The cellulose product is formed in a forming mould which in one example comprises a first positive mould part and a second negative mould part. The forming mould parts are stiff and non-flexible, preferably made from steel or another stiff material, and may be heated to the desired forming temperature. The forming mould is in one example heated with integrated heating elements, preferably electrical heating elements, but also liquid heating is possible. The forming mould is preferably closed, such that the cellulose material is completely enclosed in the mould during moulding of the cellulose DMF product.

[0084] In the shown example, the starting material is an air-laid cellulose blank structure as is commonly used for dry moulded fibre products. In this example, the cellulose material is an air-laid cellulose blank comprising loose cellulose fibres having a weight of the cellulose blank structure that is between 400-600 GSM. With such a material, a DMF product with a density between 1 ,00-1 ,10 g / cm3can be obtained when moulded with a forming pressure between 4-20 MPa.

[0085] The cellulose material is preferably made from chemical pulp where most of the lignin and hemicellulose has been removed. The cellulose material may also comprise some additives, where the additives are used to decrease the liquid and / or gas permeability of the cellulose product and to increase the resistance to e.g. hot and cold liquids, grease, oil etc. Such additives may also be applied to the surface of the cellulose product after the cellulose product is formed. In one example, the cellulose material comprises at least 90% cellulose fibres by dry weight. The additives used are additives adapted to alter the permeability of the cellulose material, and should not function as a binder material to bind the cellulose material together. By using untreated cellulose fibres, the cellulose fibres are bound together by hydrogen bonds and Van der Vaals bonds. Additives may decrease the possibility for hydrogen bonds, and binder material will definitely reduce the possible hydrogen bonds. The cellulose DMF product is formed in the forming mould during a cycle time period in the range of 0,1 to 10 seconds, and preferably less than 5,0 seconds. A suitable holding time for the product in the forming mould is less than a second, and may be e.g. 0,3-0, 7 seconds. The holding time together with the forming temperature and the forming pressure are important parameters in the forming of the cellulose product.

[0086] 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 not be 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.

[0087] REFERENCE SIGNS

[0088] 1 : Cellulose product

[0089] 2: Cellulose blank structure

[0090] 3: Bottom portion

[0091] 4: Side wall portion

[0092] 5: Upper portion

[0093] 6: Lower portion

[0094] 7: Forming mould

[0095] 8: First mould part

[0096] 9: Second mould part

[0097] 10: First bottom part

[0098] 11 : Second bottom part

[0099] 12: First side wall part

[0100] 13: Second side wall part

[0101] 14: Bottom part of forming mould

[0102] 15: Side wall part of forming mould

[0103] 16: Lower mould part of forming mould

[0104] 17: Upper mould part of forming mould

[0105] 18: Rim portion

[0106] 19: Handle

[0107] 20: Cellulose product forming apparatus

[0108] 21 : Dry forming unit

[0109] 22: Separating unit

[0110] 23: Forming box

[0111] 24: Forming wire

[0112] 25: Compacting unit

[0113] 26: Roll

[0114] 27: Cellulose fibres

[0115] 28: Fan

[0116] 29: Vacuum box

[0117] 30: Separating rollers 31 : Feeding unit

[0118] 32: Pressing unit

[0119] 33: Centre axis

[0120] 34: Support plate 35: Opening

[0121] D1 : Distance between the first side wall part of the first mould part and the second side wall part of the second mould part at the upper mould part of the forming mould

[0122] D2 Distance between the first side wall part of the first mould part and the second side wall part of the second mould part at the lower mould part of the forming mould

[0123] D11 : Thickness of the cellulose product at the upper portion of the side wall portion 4

[0124] D12: Thickness of the cellulose product at the lower portion of the side wall portion a: Draft angle

Claims

CLAIMS1. A method for producing a three-dimensional deep drawn cellulose Dry Moulded Fibre product (1 ) having a bottom portion (3) and a side wall portion (4) from a cellulose blank structure (2) wherein the method comprises the steps of; heating a forming mould (7) to a forming temperature in the range of 100°C to 300°C; arranging the cellulose blank structure in the forming mould (7); and forming the cellulose product (1 ) from the cellulose blank structure (2) in the heated forming mould (7), by pressing the cellulose blank structure (2) with a forming pressure between 1 to 100 MPa, where the forming mould (7) comprises a first mould part (8) and a second mould part (9), and where a distance (D1 ) between a first side wall part (12) of the first mould part (8) and a second side wall part (13) of the second mould part (9) at an upper mould part (17) of the forming mould (7) in a closed state is greater than a distance (D2) between the first side wall part (12) of the first mould part (8) and the second side wall part (13) of the second mould part (9) at a lower mould part (17) of the forming mould (7) in the closed state, wherein the distance (D1 ) between the first side wall part (12) of the first mould part (8) and the second side wall part (13) of the second mould part (9) at the upper mould part (17) is at least 1 ,7 times greater than the distance (D2) between the first side wall part (12) of the first mould part (8) and the second side wall part (13) of the second mould part (9) at the lower mould part (17).

2. A method according to claim 1 , wherein the distance (D1 ) between the first side wall part (12) of the first mould part (8) and the second side wall part (13) of the second mould part (9) at the upper mould part (17) is at least 2,0 times greater than the distance (D2) between the first side wall part (12) of the first mouldpart (8) and the second side wall part (13) of the second mould part (9) at the lower mould part (17).

3. A method according to claim 2, wherein the distance (D1 ) between the first side wall part (12) of the first mould part (8) and the second side wall part (13) of the second mould part (9) at the upper mould part (17) is at least 2,6 times greater than the distance (D2) between the first side wall part (12) of the first mould part (8) and the second side wall part (13) of the second mould part (9) at the lower mould part (17).

4. A method according to any of claims 1 to 3, wherein a draw ratio defined as the height (h) of the cellulose product (1 ) divided with the smallest width (w) of the cellulose product (1 ) is less than 0,8.

5. A method according to claim 4, wherein the draw ratio is less than 0,7.

6. A method according to any of the preceding claims, wherein a draft angle (a) of the side wall portion (4) is greater than 10 degrees in relation to a centre axis (33) of the cellulose product.

7. A method according to any of the preceding claims, wherein the cellulose material is a cellulose blank structure (2) formed in a dry-forming process where cellulose fibres are carried and formed to the cellulose blank structure (2) by air as carrying medium.

8. A method according to any of the preceding claims, wherein the cellulose material comprises at least 90% cellulose fibres by dry weight.

9. A method according to any of claims 1 to 8, wherein the forming mould (7) comprises a support plate (34) arranged between the first mould part (8) and the second mould part (9), and above the cellulose blank structure (2).

10. A three-dimensional deep drawn cellulose Dry Moulded Fibre product (1 ) formed from a cellulose blank structure (2), where the cellulose product (1 ) comprises a bottom portion (3) and a side wall portion (4), c h a r a c t e r i z e d i n that an upper portion (5) of the side wall portion (4) is thicker than a lower portion (6) of the side wall portion (4), wherein the upper portion (5) of the side wall portion (4) is at least 1 ,7 times thicker than the lower portion (6) of the side wall portion (4).11 . A product according to claim 10, wherein the upper portion (5) of the side wall portion (4) is at least 2,0 times thicker than the lower portion (6) of the side wall portion (4).

12. A product according to claim 10 or 11 , wherein the upper portion (5) of the side wall portion (4) is at least 2,6 times thicker than the lower portion (6) of the side wall portion (4).

13. A product according to any of claims 10 to 12, wherein the thickness of the bottom portion (3) is equal to the thickness of the lower portion (6) of the side wall portion (4).

14. A product according to any of claims 10 to 13, wherein the cellulose product comprises a handle (19).

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