A method for producing a high density dry moulded fibre cellulose product and a cellulose product forming system

Abstract

A cellulose three-dimensional cellulose High Density Dry Moulded Fibre (HD-DMF) product (1) and a method for producing a three-dimensional cellulose High Density Dry Moulded Fibre (HD-DMF) product (1) from a cellulose material (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 material in the forming mould (7), and forming the cellulose product (1) from the cellulose material in the heated forming mould (7), by moulding the cellulose material (2) with a forming pressure and by inducing vibrations to obtain a density of the cellulose product (1) greater than 1,20 g / cm3.

Description

The present disclosure relates to a method for producing a three-dimensional shaped high density dry moulded fibre (HD-DMF) cellulose product from a cellulose material.BACKGROUNDCellulose 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.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.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.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 can be used to replace disposable plastic products, but are somewhat limited when it comes to strength and the possibility to vary the thickness of a product to a great extent. A Dry Moulded Fibres product is produced from an air-laid cellulose fibre structure where the cellulose fibre structure is pressed in a forming mould to a three-dimensional cellulose product.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 fluff blank are drawn apart somewhat when a non-flat shape is created. If the shape or height difference is too large, the cellulose blank may be torn, which is one reason why deep drawn dry moulded fibre products are difficult to produce. Since the cellulose blank does not float or stretch, it is also difficult to produce dry moulded cellulose products where the difference in thickness varies over the cellulose product. DMF products can be produced at the same cost as disposable plastic products.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.SUMMARYAn 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 threedimensional shaped cellulose product.The disclosure concerns a method for producing a three-dimensional cellulose high density dry moulded fibre (HD-DMF) product from a cellulose material, wherein the method comprises the steps of; heating a forming mould comprising a male mould part and a female mould part 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, and by vibrating at least one mould part of the forming mould, to obtain a density of the cellulose product greater than 1,20 g / cm3. The cellulose material comprises at least 50% cellulose fibres.Advantages with these features are that the method provides an efficient manufacturing process for cellulose products with improved mechanical and chemical properties, where a cellulose product is a high density dry moulded fibre (HD-DMF) product. The advantage with this method is that high density dry moulded fibre products are provided, having a higher strength than regular dry moulded fibre (DMF) products that are moulded with a forming pressure of 10-20 MPa. The HD-DMF product may also have an uneven wall thickness. The forming pressure is greater than 100 MPa, preferably greater than 150 MPa, and preferably greater than 200 MPa or more.With a sufficiently high forming pressure and with sufficient vibrations, the cellulose material will be subjected to shear forces during the pressing action, such that the cellulose material will be able to flow in the forming mould. In this way, cellulose products having more complicated shapes that are not possible to obtain by regular dry moulded fibres forming can be produced. It is e.g. possible to provide cellulose products having a wall thickness that varies with more than 200%. One example of such a cellulose product is a screw cap for a beverage bottle, where the cap comprises an internal thread adapted to interact with a thread of a bottle neck. Another product suitable to produce with the inventive method is a coffee capsule, where the coffee capsule is deep drawn. Due to the pseudo-plastic behaviour of the cellulose material, a thin, deep cellulose capsule can be obtained. The inventive method further allows for cellulose products having sections with different thicknesses, such that the rim of the capsule may be thicker than the side wall, and such that the bottom of the capsule may comprise thinner sections that are easier to penetrate. In a screw cap, the thickness of a threaded section is around twice as a nonthreaded section.A further advantage of the inventive method is that the forming mould must not be filled evenly with cellulose material, as is the case with the regular dry moulded fibres method. Due to the high shear forces acting on the cellulose material during the pressing action, the cellulose material will flow into all regions of the forming mould, filling the forming mould evenly with cellulose material. In one example, cellulose material is only positioned in the bottom of the forming mould and will fill the forming mould completely during the pressing action. In another example, cellulose material is distributed randomly in the forming mould. The exact positioning of the cellulose material is not very important with the inventive method.The moulding of a HD-DMF product is performed in a closed mould, where the cellulose material is completely enclosed by the mould. During a moulding action with a high forming pressure, where the forming pressure exceeds 100 MPa, the forces acting on the cellulose fibres will not only provide a compressing force but also a shear force on the cellulose fibres when a threedimensional product is moulded, since the cellulose fibres will be displaced somewhat relative each other. The shear forces acting on the cellulose fibres will to some extent transform some of the cellulose fibres to micro fibrils and nano-cellulose. This process will be accelerated by introducing vibrations to the cellulose material through one or both forming mould parts during the pressing action. The high pressure and the vibrations will allow the cellulose material to flow and to fill the forming mould completely. In this way, relatively complicated cellulose product shapes can be obtained. It would e.g. be possible to produce a dry moulded cellulose product having an inner dividing wall. By vibrating one or both forming mould parts, the cellulose material in the forming mould will be exposed to shear forces that allows the cellulose fibres to flow.In one example, the forming pressure is higher than 150 MPa and may be higher than 200 MPa or higher, depending on the produced cellulose product. The forming pressure may be up to 500 MPa or even up to 1000 MPa or more, depending on the intended use and the actual cellulose product. If various additives are used in the cellulose material, this may also impact the most suitable forming pressure. The density of the moulded cellulose product is greater than 1,20 g / cm3 and may be up to 1,30 g / cm3 or even higher. Tests have shown that a density of a high density dry moulded cellulose product greater than 1,40 g / cm3 or more is possible to achieve.A higher forming pressure will give a cellulose product with a higher strength and a higher density. By exposing the cellulose material to vibrations by vibrating one of the forming mould parts during the pressing action, a cellulose product having the same properties can be achieved with a reduced forming pressure. The vibrations are in one example axial in the pressing direction, where a vibration device is comprised in at least one of the forming mould parts of the forming mould. In another example, the vibrations are rotational, i.e. at least one of the forming mould parts of the forming mould is exposed to rotational vibration movements. It is also possible to vibrate one or both forming mould parts in one or both translation directions, i.e. sideways. A combination of different vibrations is also possible. If both forming mould parts are vibrated, it is important that the vibrations are different in direction or frequency, such that the cellulose fibres are exposed to shear forces.The vibrations introduced to the forming mould are in one example created by a vibration device integrated in one of the mould parts of the forming mould. The vibration device may be integrated directly into the forming mould part, may be positioned in the holder plate for the forming mould part or may be arranged at the forming press, e.g. by controlling the hydraulic press cylinder. By positioning the vibration device in the holder plate or at the forming press, the same vibration device can be used for different forming moulds, where a forming mould part is attached to the holder plate. A further advantage of positioning the vibration device to the holder plate or at the forming press is that the vibration device must not be exposed to the heat of the forming mould. There is an insulation between the holder plate and the forming mould. A further advantage is that forming moulds of different sizes and shapes can be attached to the same holder plate, which reduces the need for several vibration devices.For relatively low frequency vibration, typically below 100 Hz, servohydraulic or electrohydraulic devices can be used. For frequencies typically between 1 Hz to 2000 Hz, electrodynamic devices can be used. In one example, the vibrations have a relatively low frequency, in the range between a few Hertz up to 100 Hertz. The vibrations are superimposed on the regular forming pressure, where the initial forming pressure preferably is above 100 MPa or more. The waveform of the vibrations is not crucial, and a sinusoidal waveform or a triangular waveform may be used. The stroke of the vibration device may be relatively short, from parts of a mm up to a few mm. The total energy of the vibrations is a combination of pressure, frequency and stroke length.The temperature of the cellulose material is preferably above 100 degrees Celsius during the pressing action. The temperature should not exceed 300 degrees Celsius. Lower temperatures may be possible to use, but will give reduced properties regarding strength etc.The material used for the cellulose product preferably comprises natural cellulose fibres and may further comprise other substances. If the material is wood, the material comprises cellulose fibres, lignin and hemicellulose. The material is in one example wood pulp, a fibrous lignocellulosic material prepared from wood or other plants by chemically, semi-chemically or mechanically treatment of the material. Such a material may e.g. comprise between 50-99% cellulose fibres.The material used may also comprise cellulose fibres and some additives, such as different barrier materials that are intended to increase the resistance of the cellulose product to withstand liquids, grease, oil, heat etc. The additives are preferably mixed into the cellulose material such that the cellulose material comprises a homogenous mixture of the different ingredients. Other additives that may be used could be additives that increase the strength of the cellulose product, or additives that increase the flowability of the material during the pressing action.The cellulose material will also comprise some water. A water content between 2-20% may be used, depending on the actual cellulose material used. A too low water content will reduce the possibility to form hydrogen bonds between the cellulose fibres.It is of advantage that the forming pressure is as low as possible to obtain a cellulose product with the required parameters. By using vibrations in combination with a high forming pressure, the forming pressure can be reduced when compared to a pressing action without vibrations. The vibrations will increase the shear forces between the cellulose fibres in the cellulose material, which will allow the cellulose material to flow and to fill the forming mould completely, even if the shape of the forming mould is relatively complicated with varying wall thickness, threads, gripping surfaces etc. This is opposed to regular dry moulded fibre forming, where an air-formed cellulose mat structure is pressed in a forming mould. In such a method, the cellulose mat structure is compacted to a cellulose product having substantially the same wall thickness and having a density below 1,20 g / cm3.The cellulose product may be formed in a closed mould having a specified volume, where a predefined amount of material will be inserted and pressed. This will give a cellulose product having a predefined volume, shape and density. By selecting the pressing parameters correctly, a cellulose product having a density higher than 1,20 g / cm3 is obtained. It is important that the correct amount of material is used in such a forming mould in order to obtain a cellulose product with the desired density. With a too low material content, there will not be enough shear forces acting on the cellulose fibres. When enough material is used in the forming mould, the material will flow, which will give a cellulose product with a density of at least 1,20 g / cm3. More material will give a higher density, up to a maximal value, depending on the used forming pressure and the amount of induced vibrations.The preferred forming pressure is a forming pressure where the desired parameters for the cellulose product are met, without exceeding these parameters. A higher forming pressure adds a cost to the cellulose product. This means that in the same press with the same rated pressure, fewer and / or smaller cellulose products can be made 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 exceeding approximately 100 MPa will allow the cellulose material to flow, which allows for a HD-DMF product having a more complicated shape and a varying wall thickness. By inducing vibrations to the forming mould, the used forming pressure can be reduced.One advantage with a higher forming pressure where the cellulose material will flow is that complicated shapes can be obtained, which are difficult to obtain with regular moulding of DMF products. With the inventive method, more complicated product such as a lid having internal threads and a smooth outer surface can be produced, where the wall thickness of the lid varies with up to 300-400% or more.The cellulose product is formed in a forming mould which comprises a first male mould part and a second female mould part. The forming mould parts are non-flexible, preferably made from steel, 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 in one example provided with a closed volume, such that the density depends on the used amount of cellulose material. In another example, the forming mould is pressure controlled, such that the density depends on the forming pressure and not on the amount of cellulose material. In one example, the second mould part consists of two or more sections such that the second mould part can be opened and closed before and after the pressing action.The cellulose material is in one example an air-laid cellulose blank structure used for regular dry moulded fibre products. Here, the cellulose material may be pre-pressed in a pre-forming mould with a low pre-forming pressure in the range between 1-10 MPa. The purpose of the pre-forming is to compress the cellulose material to a smaller volume such that it will be easier to insert the pre-formed cellulose material into the forming mould.In another example, the cellulose starting material is a cellulose cardboard paper or pulp sheet containing either substantially only cellulose fibres or cellulose fibres and additives. The cardboard paper or pulp sheet may be stacked in several layers in order to obtain a desired amount if cellulose material. The cellulose material may also be cellulose particles or cellulose granules containing either substantially only cellulose fibres or cellulose fibres and additives. The granules or particles may be inserted directly into the forming mould. The cellulose material may also be a single pod comprising the required amount of cellulose fibres and additives.During the moulding of a three-dimensional HD-DMF cellulose product, different forces will act on the cellulose material. By vibrating one or both of the forming mould parts, shear forces will act on the cellulose material. The shear forces, together with the high forming pressure will allow the cellulose fibres to flow in the forming mould.The cellulose material may be made from mechanical pulp, thermochemical pulp or chemical pulp comprising at least some lignin and / or hemicellulose, also referred to as a lignocellulosic raw material. The cellulose material may in one example comprise more than 0,5% lignin. The cellulose material may also be a lignocellulosic material comprising both lignin and hemicellulose, e.g. made from mechanical pulp. The cellulose material may also include 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 bounds and Van der Vaals bounds. Additives may decrease the possibility for hydrogen bounds, and binder material will definitely reduce the possible hydrogen bounds.One suitable product made from cellulose HD-DMF is a screw cap for a bottle. The screw cap is provided with a top section and a concentric side wall having an inner surface and an outer surface, where the inner surface is provided with at least one internal thread section and where the circumferential outer surface is substantially even. Such a cellulose HD-DMF screw cap will resemble a regular plastic screw cap used for e.g. PET plastic bottles. The internal thread section may be a single thread or may comprise several thread sections that constitutes a screw thread. With the inventive method, a cellulose HD-DMF product where the thickness of the product varies with at least 200% can be obtained. A thickness variation up to 300-400% or more is possible if desired. In this way, it is possible to provide an internal thread on the inner surface of the screw cap, while the outer surface can be substantially smooth and even. It is of course also possible to provide the outer surface of the screw cap with some kind of gripping surface, a gripping rim and / or a tamper proof fixation rim. Another suitable product is a flip-lid used on containers that are not provided with a thread.The cellulose HD-DMF product is formed in the forming mould during a cycle time period in the range of 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. 0,1 -0,7 seconds. The holding time together with the forming temperature, the forming pressure and the vibrations are important parameters in the forming of the HD-DMF cellulose product.BRIEF DESCRIPTION OF DRAWINGSThe disclosure will be described in greater detail in the following, with reference to the attached drawings, in whichFigs. 1a-d show schematically a first example of a method for producing a cellulose HD-DMF product from a cellulose material according to the disclosure,Figs. 2a-e show schematically another example of a method for producing a cellulose HD-DMF product from a cellulose material according to the disclosure, andFigs. 3a-d show schematically another example of a method for producing a cellulose HD-DMF product from a cellulose material according to the disclosure,Figs. 4a-f show schematically a further example of a method for producing a cellulose HD-DMF product from a cellulose material according to the disclosure,Figs. 5a-d show schematically a further example of a method for producing a cellulose HD-DMF product from a cellulose material according to the disclosure,Fig. 6 shows schematically examples of forming pressures for producing a cellulose HD-DMF product according to the disclosure,Fig. 7 shows schematically an example of a cellulose HD-DMF product according to the disclosure,Fig. 8 shows schematically a further example of a cellulose HD-DMF product according to the disclosure,Fig. 9 shows schematically a further example of a cellulose HD-DMF product according to the disclosure, andFig. 10 shows schematically a further example of a cellulose HD-DMF product according to the disclosure.DESCRIPTION OF EXAMPLE EMBODIMENTSVarious 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.In the present detailed description, a method for producing a cellulose High Density Dry Moulded Fibre (HD-DMF) product from a cellulose material will be described. The method is suitable for different products that should exhibit a higher strength and a higher density than regular Dry Moulded Fibre (DMF) products, and that may have a more complicated shape with varying thickness. Such products may be relatively small with a volume of e.g. a few cm3 due to the required high forming pressure, which is costly. It would of course also be possible to produce larger cellulose HD-DMF products if desired. The cellulose HD-DMF products are disposable, but may be used several times, depending on the actual product and actual post treatment of the product. The cellulose HD-DMF products may be recyclable and / or compostable.Examples of such cellulose HD-DMF products are e.g. screw caps, flip caps, coffee capsules, golf pegs, toys, candy enclosures, flowerpots, medical devices and packaging, such as blister packs. In one shown example, a screw cap is used as an example of a cellulose HD-DMF product.The cellulose material used to form the cellulose HD-DMF product is a cellulose material comprising cellulose fibres and that may also comprise at least some lignin and hemicellulose. Such a material is produced from mechanical pulp, thermochemical pulp or chemical pulp where some of the lignin and the hemicelluloses can be 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% lignin or additives by weight. The cellulose material may also be a lignocellulosic material comprising both lignin and hemicellulose, e.g. made from mechanical pulp. The cellulose material will also comprise some water, e.g. between 2% 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.Figs. 1a-d show schematically a method for producing a cellulose HD-DMF product 1 from a cellulose material 2. The cellulose material may have different shapes and densities. Flere, the cellulose material is a pre-compressed pod comprising cellulose fibres and some additives, where the cellulose material and the additives are mixed to a homogenous mixture. The cellulose pod may have a dryness that is mainly corresponding to the ambient humidity in the atmosphere surrounding the cellulose material. Additional water may be added to the cellulose material, 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. In Fig. 1a, a pod of cellulose material 2 is inserted into a forming mould 7. The cellulose material may also be air-laid directly in the required size and shape.A schematic forming mould 7 is shown in Fig. 1a, where the forming mould comprises a first male mould part 8 and a second female mould part 9. The first mould part 8 is a circular mandrel and is in the shown example provided with a threaded section 10 at the lower end of the first mould part. The first mould part 8 is further provided with a vibration device 18, which is adapted to induce vibrations to the cellulose fibres through the first mould part 8. The vibrations are in the shown example induced in an axial direction, parallel with the pressing direction of the cellulose product. The vibration device is here shown as a device mounted on the first mould part, but the vibration device may be arranged at any position of the forming press acting on the first mould part. The outer diameter of the first mould part is R, which corresponds to the inner diameter of the second mould part 9, which is provided with a hollow shape that corresponds to the outer shape of the final cellulose product 1. The cellulose material 2 is inserted into the second mould part 9 of the forming mould 7.Fig. 1b shows a cut view of the cellulose material 2 and the forming mould 7. The first mould part 8 is lowered towards the second mould part 9, and starts to press on the cellulose material. In Fig. 1c, the first mould part has reached its lowermost position. In this example, an upper stop surface of the first mould part bears on the second mould part. In this way, a predefined volume of the cavity is created, in which the cellulose fibres can flow and which will allow the complete cavity to be filled. The amount of cellulose fibres compressed in the forming mould will determine the density of the cellulose product. For a given volume, more cellulose fibres will create a higher density of the cellulose product. Since the cellulose material will flow during the moulding process, the shape and size of the forming mould may be designed to compensate for a slight flexibility of the pressed cellulose material, since the cellulose material may spring back some when the forming pressure is released.The forming pressure is now at least 100 MPa, and may be up to 200 MPa or more, depending on the required parameters of the cellulose product 1. During moulding of the cellulose HD-DMF product, the cellulose material 2 is exposed to the high forming pressure and to the vibrations of the vibration device. The high pressure and the vibrations will induce shear forces to the cellulose fibres, which will bring the cellulose fibres to flow. Heat will increase the forming of hydrogen bonds between the cellulose fibres during the pressing action. The cellulose fibres will displace in the forming mould and will fill the forming mould completely. This will allow the cellulose fibres to fill the forming mould evenly.It is also possible to use a forming mould where the volume of the mould cavity is not predefined, i.e. where the upper mould part is not provided with a stop surface. In this case, the forming pressure will set the actual volume and thus density of the cellulose product. A given amount of cellulose fibres and a given forming pressure will thus give a desired density of the cellulose product. In this way, the forming pressure can be used to alter the actual density of the cellulose product if similar cellulose products with differing densities are to be produced. This may be of advantage since the exact amount of cellulose material must not be used. A slight variation of the amount of cellulose material will give cellulose products with the desired density but with a small variation in volume. In a forming mould having a closed predefined volume, a slight variation of the amount of cellulose material will give cellulose products with varying density but with an equal volume.By exposing the cellulose material to vibrations by vibrating at least one of the forming mould parts during the pressing action, a cellulose product having required properties can be achieved with a reduced forming pressure, or a cellulose product having increased properties can be achieved with the same forming pressure. The vibrations are in the shown example axial in the pressing direction, parallel to the centre axis 11, where the vibration device 18 is comprised in one of the forming mould parts of the forming mould, here in the first mould part 8.For relatively low frequency vibrations, typically below 100 Hz, a servohydraulic or electro-hydraulic device can be used. For vibration frequencies typically between 1 Hz to 2000 Hz, an electrodynamic device can be used. In one example, the vibrations have a relatively low frequency, in the range between a few Hertz up to 100 Hertz. The vibrations are superimposed on the regular forming pressure, where the initial forming pressure preferably is above 100 MPa or more. The waveform of the vibrations is not crucial, and a sinusoidal waveform or a triangular waveform may be used. The stroke of the vibration device may be relatively short, from parts of a mm up to a few mm. The total energy of the vibrations is a combination of pressure, frequency and stroke length. The vibrations are preferably induced when the forming pressure is relatively high, e.g. exceeding 100 MPa. The vibrations may be induced during the closing stroke of the forming mould, preferably at the end of the closing stroke, and / or when the forming mould is closed.Fig. 6 shows a relationship between different forming pressures. Graph a shows a typical forming pressure for a regular cellulose DMF product formed from an air-laid cellulose pulp sheet. Graph b shows a typical forming pressure for a cellulose HD-DMF product. Graph c shows a forming pressure for a cellulose HD-DMF product where the cellulose fibres are exposed to vibrations during the pressing action, with a frequency f and an amplitude A. The vibrations are superimposed to the regular forming pressure. In the shown example, a relatively low vibration frequency is used, in the range below 100 Flz. It is e.g. possible to use a valve to alter the forming pressure of the hydraulic pressure cylinder of the forming press, or use an electromechanical vibration device arranged at e.g. the first mould part. One advantage of using a relatively low vibration frequency, e.g. by using the hydraulic pressure of the forming press, is that it is easier to introduce the vibrations to the first mould part. A separate vibration device arranged in series with the forming press must be able to produce vibrations with a high pressure due to the high forming pressure used. Using the hydraulic pressure of the forming press will also allow a good control of the amplitude of the vibrations. For some cellulose products, a lower frequency and a higher amplitude may be of advantage, and for other cellulose products, a higher frequency and a lower amplitude may be more suitable. The used frequency and amplitude may also be affected by the used cellulose material and the used additives.It is also possible to position a vibration device at the lower end of the first forming mould part such that it can act directly on the cellulose fibres, e.g. a piezo device. Such a device is capable of producing vibration frequencies of up to 20 kHz or more. The used vibration frequency and the used amplitude will depend on the size and shape of the cellulose product. A higher frequency and / or higher amplitude may e.g. be required for cellulose products having thinner side walls. The vibrations may be introduced to the cellulose fibres during the closing stroke of the pressing action and / or when the forming mould is closed. The vibrations may continue during the holding time of the pressing cycle, but are shut off during the opening stroke of the pressing action. The direction of the vibrations may also vary, and may be axial, rotational, translational or a combination of these.The vibrations introduced to the forming mould are in one example created by a vibration device integrated in one of the mould parts of the forming mould, in the shown example in the first mould part. The vibration device may be integrated directly into the forming mould part, may be positioned in the holder plate for the forming mould part or may be arranged at the forming press, e.g. by controlling the hydraulic press cylinder. By positioning the vibration device in the holder plate or at the forming press, the same vibration device can be used for different forming moulds, where a forming mould part is attached to the holder plate. A further advantage of positioning the vibration device at the holder plate or at the forming press is that the vibration device must not be exposed to the heat of the forming mould. There is an insulation between the holder plate and the forming mould. A further advantage is that forming moulds of different sizes and shapes can be attached to the same holder plate, which reduces the need for several vibration devices.The high pressure and the shear forces acting on the cellulose fibres due to the induced vibrations allows the cellulose fibres to flow in the forming mould. This may be referred to as burst flow. After a specified holding time, which may be very low, the cellulose product is ready and can be removed from the forming mould.In Fig. 1d, the cellulose product 1 is removed from the forming mould by raising the first mould part 8 from the second part 9. The cellulose HD-DMF product 1 in the form of a screw cap with internal threads is removed from the threaded section of the first mould part by rotation, as is known from injection moulding of plastic screw caps. At the same time, the outer surface of the screw cap has been finalized, since the inner surface of the second mould part is provided with the desired shape and look of the screw cap.Figs. 2a-e show schematically an example of a method where the cellulose HD-DMF product is made from a cellulose material in the form of a paper sheet, such as a cardboard sheet or a pulp sheet, as a starting material. The paper sheet is formed into a small tube comprising the required amount of cellulose material. The paper tube has an outer diameter R which corresponds to the inner diameter of the forming mould. This will make it easy to insert the paper tube into the forming mould.In Fig. 2a, the paper tube 2 is inserted into the forming mould 7. A schematic forming mould 7 is shown in Fig. 2a, where the forming mould comprises a first male mould part 8 and a second female mould part 9. The first mould part 8 is a circular mandrel and is in the shown example provided with a threaded section 10 at the lower end of the mandrel. The outer diameter of the first mould part is R, which corresponds to the inner diameter of the second mould part 9, which is provided with a hollow shape that corresponds to the outer shape of the final cellulose product 1. The paper tube 2 is inserted into the second mould part 9 of the forming mould 7.Fig. 2b shows in a cut view the paper tube 2 and the forming mould 7, where the first mould part 8 is lowered towards the second mould part 9, and where the first mould part starts to press on the paper tube. The paper tube will displace and parts of the paper tube will be pushed down, towards the bottom of the second mould part 9. This is shown in more detail in Fig. 2c, where most of the paper tube has been compressed. The first mould part is pushed down with a pressing force F until the first mould part has reached its lowermost position, as is shown in Fig. 2d. The forming pressure is preferably at least 100 MPa, and may be up to 200 MPa or more, depending on the required parameters of the cellulose HD-DMF product 1. During moulding of the cellulose HD-DMF product, the paper tube is exposed to the high forming pressure and to the vibrations from the vibration device 18, such that the cellulose fibres will displace in the forming mould, filling the forming mould completely since the cellulose fibres will flow. As disclosed above, the vibrations will enhance the flowability of the cellulose fibres. After a specified holding time, the cellulose HD-DMF product is ready and can be removed from the forming mould.In Fig. 2e, the completed cellulose HD-DMF product is removed from the forming mould by raising the first mould part 8 from the second mould part 9. The cellulose HD-DMF product in the form of a screw cap with internal threads is removed from the threaded section of the first mould part by rotation, as is known from injection moulding of plastic screw caps. At the same time, the outer surface of the screw cap has been finalized, since the inner surface of the second mould part is provided with the desired shape and look of the screw cap.In a third example, shown in Figs. 3a-d, the cellulose HD-DMF product 1 is produced from a cellulose material in the form of a granular cellulose material as a starting material. The granular cellulose material may e.g. be cellulose granules or other smaller cellulose particles, such as cellulose pellets, cellulose fluff, saw dust, flakes from bale pulp, or separate cellulose fibres which may be more or less pre-compressed in order to be easier to handle. The granular material may have a dryness that is mainly corresponding to the ambient humidity in the atmosphere surrounding the granules. Additional water may be added to the granular material, up to a water content of between 6% to 20% by weight.In Fig. 3a, the granular material 2 is inserted into the forming mould 7. The schematic forming mould 7 shown in Fig. 3a comprises a first mould part 8 and a second mould part 9. The first mould part 8 is a circular mandrel and is in the shown example provided with a threaded section 10 at the lower end of the mandrel and comprising a vibration device 18. The outer diameter of the first mould part corresponds to the inner diameter of the second mould part 9, which is provided with a hollow shape that corresponds to the outer shape of the final cellulose product 1. The granular material is inserted into the second mould part 9 of the forming mould 7.When the granular material has been inserted into the second mould part of the forming mould, the first mould part 8 is lowered towards the second mould part 9, as is shown in Fig. 3b, and the first mould part starts to press on the granular material, and at the same time the vibration device introduces vibrations to the first mould part, such that the cellulose material is compressed. The vibrations may be introduced to the cellulose fibres during the closing stroke of the pressing action and / or when the forming mould is closed. The vibrations may continue during the holding time of the pressing cycle.In Fig. 3c, the first mould part has reached its lowermost position The forming pressure is now preferably at least 100 MPa, and may be up to 200 MPa or more, depending on the required parameters of the cellulose product 1. During moulding of the cellulose product, the granular material is exposed to the high forming pressure and to the vibrations, and the cellulose fibres flow due to the high forming pressure and the shear forces acting on the cellulose fibres in the forming mould, filling the forming mould completely. After a specified holding time, the cellulose product is ready and can be removed from the forming mould.In Fig. 3d, the cellulose product is removed from the forming mould by raising the first mould part 8 from the second mould part 9. The cellulose HD-DMF product in the form of a screw cap with internal threads is removed from the threaded section of the first mould part by rotation, as is known from injection moulding of plastic screw caps. At the same time, the outer surface of the screw cap has been finalized, since the inner surface of the second mould part is provided with the desired shape and look of the screw cap.Figs. 4a-f shows an example of a method for producing a cellulose HD-DMF product, in this case a cup-shaped product. In the 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. In the shown example, a cellulose material 2 is cut from an air-laid cellulose blank structure or from a fluff pulp roll, where the shape of the cellulose blank section corresponds somewhat to the final periphery of the desired cellulose HD-DMF product. The shape of the cellulose blank section may be somewhat larger than the final periphery of the desired cellulose FID-DMF such that the cellulose blank sections overlap somewhat.In the example shown in Fig. 4a, a cellulose section having a sidewall preform part 16 corresponding to a side wall 4 of the final cellulose product and a bottom preform part 17 corresponding to a bottom 3 of the final cellulose product is cut out from the cellulose blank structure or the fluff pulp roll. Other cutting pattern are also possible, as long as the cut-out parts corresponds to the periphery of the final cellulose HD-DMF product, preferably with some overlap. It is an advantage to let the parts adhere to each other, which will simplify the handling of the cellulose blank section. Fig. 4b shows the cellulose blank section folded to a preform shape resembling the final cellulose product.In Fig. 4c, the folded cellulose blank section is inserted into a forming mould 7. The forming mould comprises a first mould part 8 and a second mould part 9. The first mould part 8 is in the shown example a circular frustoconical shaped mandrel having a shape corresponding to the inner side of the final cellulose product and is comprising a vibration device 18. The second mould part 9 is provided with a hollow shape that corresponds to the outer shape of the final cellulose product. The folded cellulose blank section 2 is inserted into the second mould part 9 of the forming mould 7.Fig. 4d shows in a cut view the folded cellulose blank section 2 and the forming mould 7, where the first mould part 8 is lowered towards the second mould part 9. The first mould part 8 is provided with a hollow section 15 extending around the periphery of the first mould part, which is arranged to form a rim on the final cellulose product. When the first mould part 8 is lowered, the cellulose blank section will be pressed against the inner sides of the second mould part and will displace some. The first mould part is pushed down with a pressing force F until the first mould part has reached its lowermost position and an upper stop surface of the first mould part bears on the second lower mould part, as is shown in Fig. 4e. With a sufficient amount of cellulose fibres in the forming mould, the forming pressure will be at least 100 MPa, and may be up to 200 MPa or more, depending on the required parameters of the cellulose HD-DMF product 1. During moulding of the cellulose HD-DMF product, the folded cellulose blank section is exposed to the high forming pressure and to vibrations induced by the vibration device, and the cellulose fibres will flow due to the high forming pressure and the shear forces acting on the cellulose fibres, filling the forming mould completely since the cellulose fibres will flow into all areas of the forming mould. The rim 13 will be formed by the hollow section 15, where cellulose fibres will fill the hollow section completely. The rim 13 is in the shown example provided with a thickness t2 and is thicker than the side wall of the final cellulose product, where the side wall has a thickness t1. The cellulose fibres will fill the forming mould evenly.The high pressure and the vibrations create shear forces that acts on the cellulose fibres and thus allows the cellulose fibres to flow. After a specified holding time, the cellulose HD-DMF product is ready and can be removed from the forming mould. In Fig. 4f, the completed cellulose HD-DMF product 1 is removed from the forming mould by raising the first mould part 8 from the second mould part 9.Figs. 5a-d shows a further example of a method for producing a cellulose HD-DMF product, in this case a cup-shaped product. In the example, the cupshaped product is circular with a frustoconical shape, but other circular shapes are also possible. In the shown example, the cellulose material 2 may be an air-laid cellulose blank structure, a section of a fluff pulp roll or a precompressed cellulose material pod.In the example shown in Fig. 5a, the first mould part 8 is provided with a vibration device arranged to induce rotational vibrations to the cellulose fibres through the first mould part. The vibration device will vibrate with a vibration frequency in the range between a few Hz up to 2000 Hz, and in one example below 100 Flz. The vibration device will induce angular rotational vibrations ranging over a rotational angle a, where a is in the range between less than a degree up to e.g. 10 degrees. The rotational angle is also dependent on the frequency, a small rotational angle allows for a higher frequency and a larger rotational angle requires a lower frequency.The vibration device may be a servo-hydraulic or electro-hydraulic device. The vibrations are superimposed on the regular forming pressure, where the initial forming pressure preferably is above 100 MPa or more. The waveform of the vibrations is not crucial, and a sinusoidal waveform or a triangular waveform may be used. The total energy of the vibrations is a combination of pressure, frequency and rotational angle.Fig. 5b shows in a cut view the cellulose material 2 and the forming mould 7, where the first mould part 8 is lowered towards the second mould part 9. The first mould part 8 is provided with a hollow section 15 extending around the periphery of the first mould part, which is arranged to form a rim on the final cellulose product. When the first mould part 8 is lowered, the cellulose material will be exposed to a high forming pressure and to rotational vibrations from the vibration device which will allow the cellulose fibres to flow from the bottom section of the forming mould up to the side walls such that the forming mould is filled completely. The first mould part is pushed down with a pressing force F until the first mould part has reached its lowermost position and an upper stop surface of the first mould part bears on the second lower mould part, as is shown in Fig. 5c.With a sufficient amount of cellulose fibres in the forming mould, the forming pressure will be at least 100 MPa, and may be up to 200 MPa or more, depending on the required parameters of the cellulose HD-DMF product 1. During moulding of the cellulose HD-DMF product, cellulose material is exposed to the high forming pressure and to the rotational vibrations induced by the vibration device, such that the cellulose fibres will flow due to the high forming pressure and the shear forces acting on the cellulose fibres, filling the forming mould completely. The rim 13 will be formed by the hollow section 15, where cellulose fibres will fill the hollow section completely. The rim 13 is in the shown example thicker than the side wall of the final cellulose product. The rim has a thickness t2 and side wall has a thickness t1.The high pressure and the rotational vibrations create shear forces that acts on the cellulose fibres and that allows the cellulose fibres to flow. The rotational vibrations may be introduced to the cellulose fibres during the closing stroke of the pressing action and / or during the holding time when the forming mould is closed. The vibrations may continue during the holding time of the pressing cycle. After a specified holding time, which may be very low or even zero, the cellulose HD-DMF product is ready and can be removed from the forming mould. In Fig. 5d, the completed cellulose HD-DMF product 1 is removed from the forming mould by raising the first mould part 8 from the second mould part 9.The three-dimensional cellulose HD-DMF product is formed in a cellulose product forming system from a cellulose material 2, wherein the product forming system comprises a heated forming mould 7 having a first mould part 8 and a second mould part 9. The product forming system is configured to press the cellulose material 2 with a forming pressure to obtain a density of the cellulose product 1 greater than 1,20 g / cm3 and where the product forming system includes a vibration device 18 configured to vibrate the first mould part 8 and / or the second mould part 9 of the heated forming mould 7 during the pressing action.In one shown example, a screw cap for a bottle is used as an example of a cellulose HD-DMF product, as shown in Fig. 7. The screw cap comprises a bottom section 3 and a circular side wall 4 having an outer surface 6 and an inner surface 5. The inner surface is in one example provided with a protruding element 12 in the form of a threaded section comprising one or more protruding elements formed as the threaded section. The screw cap may also comprise a snap lock having a rim section that is arranged to snap to a rim of a container. A screw cap is a product well suited to be produced with the inventive method, since it is relatively small and has a relatively complicated shape that requires varying wall thickness of the product.Fig. 8 shows a coffee capsule, another product that is well suited to be produced with the inventive method. The coffee capsule comprises a bottom section 3 and a circular side wall 4 having an outer surface 6 and an inner surface 5. The coffee capsule further comprises a rim 13, where the thickness of the rim is several times thicker than the side wall. The side wall thickness of the coffee capsule may in one example be thinner than 0,8 mm. A thickness difference of 300-400% or more is possible to achieve with the inventive method. The bottom section 3 is also provided with one or more penetration regions 14 which are thinner than the rest of the bottom section. The penetration sections are intended to be penetrated by the coffee machine when coffee is brewed. Some sections of the coffee capsule can be made thinner than surrounding sections. A further advantage of the inventive method is that a deep drawn coffee capsule can be produced. A coffee capsule may also be provided with some sections having a different thickness, such as a bottom of the coffee capsule having thinner areas where the bottom is to be penetrated, or a thicker rim section. Figs. 9 and 10 shows examples of cuplike cellulose products having protruding elements. The cup-like cellulose product comprises a bottom section 3 and a circular side wall 4 having an outer surface 6 and an inner surface 5. The bottom section and the side wall may have the same thickness or the thickness may vary. The cellulose product may be circular, square or may have another shape.Fig. 9 shows a cup-like product having protruding elements 12 arranged at the inner surface 5 of the cellulose product. The shape of the protruding elements may vary. A protruding element may in one example be spiral shaped such that it can be removed from the forming mould by rotation.Fig. 10 shows a cup-like product having protruding elements 12 arranged at the outer surface 6 of the cellulose product. The shape and the number of the protruding elements may vary. A cellulose product having one or more protruding element arranged on the outer surface is preferably made in a forming mould having several sections for the negative second mould part.Tests have shown that when forming a cellulose HD-DMF product, a suitable forming pressure level is at least 100 MPa and may be up to 200 MPa or more, depending on the desired properties of the actual cellulose HD-DMF product and the induced vibrations. A suitable moulding temperature level is in the range of 100°C to 300°C.The vibrations may be induced from one forming mould part or from both forming mould parts. If both forming moulds are used, it is important that the induced vibrations differ in frequency and / or direction, such that the cellulose fibres are exposed to high shear forces. The vibrations are in one example axial, in another example rotational, and in another example translational. The vibrations may also be a combination of these. Translational vibrations may e.g. be suitable for rectangular cellulose products, such as food trays.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.REFERENCE SIGNS1: Cellulose product 2: Cellulose material 3: Bottom section 4: Side wall5: Inner surface6: Outer surface7: Forming mould 8: First mould part 9: Second mould part 10: Threaded section 11: Centre axis12: Protruding element 13: Rim14: Penetration region 15: Hollow section 16: Preform side wall 17: Preform bottom 18: Vibration device

Claims

1. A method for producing a three-dimensional cellulose High Density Dry Moulded Fibre product (1) from a cellulose material (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, where the forming mould (7) comprises a first mould part (8) and a second mould part (9),arranging the cellulose material in the forming mould (7); and forming the cellulose product (1) from the cellulose material (2) in the heated forming mould (7), by pressing the cellulose material (2) with a forming pressure to obtain a density of the cellulose product (1) greater than 1,20 g / cm3,where the pressing of the cellulose material (2) includes vibrating the first mould part (8) and / or the second mould part (9) of the heated forming mould (7) during the pressing action.

2. A method according to claim 1,wherein the forming pressure is at least 100 MPa.

3. A method according to claim 1 or 2,wherein the forming pressure is at least 150 MPa.

4. A method according to any of claims 1 to 3,wherein the forming pressure is at least 200 MPa.

5. A method according to any of claims 1 to 4,wherein the vibration of the first mould part (8) and / or the second mould part (9) takes place during the closing stroke of the pressing action.

6. A method according to any of claims 1 to 4,wherein the vibration of the first mould part (8) and / or the second mould part (9) takes place when the forming mould (7) is fully closed.

7. A method according to any of claims 1 to 6,wherein the first mould part (8) and / or the second mould part (9) is vibrated with a frequency of less than 20 Hz.

8. A method according to any of claims 1 to 6,wherein the first mould part (8) and / or the second mould part (9) is vibrated with a frequency between 20 to 2000 Hz.

9. A method according to any of claims 1 to 6,wherein the first mould part (8) and / or the second mould part (9) is vibrated with a frequency above 10 kHz.

10. A method according to any of claims 1 to 9,wherein the first mould part (8) and / or the second mould part (9) is vibrated with an axial vibration directed in the pressing direction.

11. A method according to any of claims 1 to 10,wherein the vibrations are superimposed to the forming pressure.

12. A method according to any of claims 1 to 11,wherein the vibration amplitude is between 0,01 mm to 2 mm.

13. A method according to any of claims 1 to 12,wherein the vibration waveform is sinusoidal.

14. A method according to any of claims 1 to 13,wherein the first mould part (8) is vibrated in an axial direction and the second mould part (9) is vibrated in a rotational direction.

15. A method according to any of claims 1 to 14,wherein the first mould part (8) and / or the second mould part (9) is vibrated with at least 10 vibrations at a frequency between 1 to 2000 Hz.

16. A method according to any of claims 1 to 14,wherein the first mould part (8) and / or the second mould part (9) is vibrated for at least 0,5 seconds at a frequency above 10 kHz.

17. A method according to any of the preceding claims,wherein the cellulose material (2) contains less than 20% water.

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

19. A method according to any of the preceding claims,wherein the cellulose material comprises cellulose fibres and at least one additive.

20. A cellulose product forming system for dry-forming a three-dimensional cellulose High Density Dry Moulded Fibre product (1) from a cellulose material (2), wherein the product forming unit comprises a heated forming mould (7) having a first mould part (8) and a second mould part (9), characterized in that the product forming unit is configured to press the cellulose material (2) with a forming pressure to obtain a density of the cellulose product (1) greater than 1,20 g / cm3 and that the product forming unit includes a vibration device (18) configured to vibrate the first mould part (8) and / or the second mould part (9) of the heated forming mould (7) during the pressing action.

21. A three-dimensional cellulose High Density Dry Moulded Fibre product (1) formed from a cellulose material (2), characterized in that the cellulose product (1) has a density greater than 1,20 g / cm3.

22. A product according to claim 21, wherein the density is greater than 1,30 g / cm3.

23. A product according to claim 21 or 22, wherein the density is greater than 1,40 g / cm3.

24. A product according to any of claims 21 to 23, wherein a wall thickness of the cellulose product (1) varies with at least 200%.

25. A product according to any of claims 21 to 24, wherein the cellulose product (1) comprises a bottom section (3) and a circular side wall (4) having an outer surface (6) and an inner surface (5), where the inner surface (5) is provided with at least one protruding element (12), and where the outer surface (6) is substantially even.

26. A product according to any of claims 21 to 25, wherein the cellulose product (1) comprises a bottom section (3) and a circular side wall (4) having an outer surface (6) and an inner surface (5), where the outer surface (6) is provided with at least one protruding element (12), and where the inner surface (5) is substantially even.

27. A product according to any of claims 21 to 26, wherein a side wall thickness of the cellulose product is thinner than 0,8 mm.