WO2025104300A1

WO2025104300A1 - A method for producing a cellulose product and a cellulose product

Info

Publication number: WO2025104300A1
Application number: PCT/EP2024/082582
Authority: WO
Inventors: Ove Larsson
Original assignee: Pulpac AB
Current assignee: Pulpac AB
Priority date: 2023-11-15
Filing date: 2024-11-15
Publication date: 2025-05-22
Anticipated expiration: 2026-05-15
Also published as: SE2351306A1

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 high purity cellulose material comprising at least 95% cellulose fibres (2; 17; 19), 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 high purity cellulose material in the forming mould (7), and forming the cellulose product (1) from the high purity cellulose material in the heated forming mould (7), by moulding the high purity cellulose material (2; 17; 19) with a forming pressure of at least 100 MPa to obtain a density of the cellulose product (1) greater than 1,30 g/cm3

Description

A METHOD FOR PRODUCING A CELLULOSE PRODUCT AND A

CELLULOSE PRODUCT

TECHNICAL FIELD

The present disclosure relates to a method for producing a three-dimensional shaped high density dry moulded fibre (HD-DMF) cellulose product from a material comprising at least 90% cellulose fibres.

BACKGROUND

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.

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 extend.

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.

SUMMARY

An object of the present disclosure is to provide a method for producing a three-dimensional 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 three-dimensional cellulose product. Another object of the present disclosure is to provide a three-dimensional shaped cellulose product.

The disclosure concerns a method for producing a cellulose high density dry moulded fibre (HD-DMF) product from a cellulose material comprising at least 90% cellulose fibres, 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 high purity 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 greater than 100 MPa to obtain a density of the cellulose product greater than 1 ,30 g/cm³

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 in a range between 10-20 MPa. The forming pressure is greater than 100 MPa, preferably greater than 150 MPa, and preferably greater than 200 MPa or more. A cellulose material comprising at least 90% cellulose fibres and preferably at least 95% cellulose fibres may be referred to as a high purity cellulose material, where the material consists substantially of only cellulose fibres without any or almost any lignin or hemicellulose.

With a sufficiently high forming pressure, the high purity cellulose material will become pseudo-plastic during the pressing action, which means that at least parts of the high purity cellulose material comprising substantially only cellulose fibres will assume liquid-like properties during the moulding action. The moulding of a HD-DMF product is in one example performed in a closed mould, where the high purity 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 three-dimensional product is moulded, since the cellulose fibres will be displaced somewhat. The shear forces acting on the cellulose fibres will to some extent transform some of the cellulose fibres to micro fibrils and nanocellulose. The shear forces may be increased by movement of one or both forming moulds during the moulding action, e.g. by vibrations and/or rotations of one or both forming moulds. 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 high purity cellulose material, this may also impact the most suitable forming pressure. The density of the moulded cellulose product is greater than 1 ,30 g/cm³ and may be up to 1 ,40 g/cm³ or even higher. Tests have shown that a density of a moulded cellulose product greater than 1 ,40 g/cm³ is possible to achieve, and densities can come close to the upper limit of 1 .6 g/cm³ for crystalline cellulose.

Even though a higher forming pressure will give a cellulose product with a higher strength and a higher density, 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 start to give the cellulose material pseudo-plastic properties, which allows for a HD-DMF product having a more complicated shape and a varying thickness.

One advantage with a higher forming pressure where the high purity cellulose material assume pseudo-plastic properties 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 thickness of the lid varies with up to 300-400%. The method can also be used for e.g. the neck of a dry moulded cellulose fibre bottle, where the neck is provided with an external thread and a smooth inner surface. The rest of the bottle can be produced with a regular forming pressure of e.g. 10-20 MPa in order to save cost.

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 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 preferably closed, such that the high purity cellulose material is completely enclosed in the mould during moulding of the HD-DMF cellulose product.

In one example, the starting material is an air-laid cellulose blank structure used for regular dry moulded fibre products. Here, the high purity 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 order to provide a cellulose HD-DMF product, more cellulose material will be needed for a cellulose HD-DMF product having desired dimensions, e.g. a desired thickness. If e.g. an air-laid cellulose blank material is used as starting material, a weight of between 1000-3000 GSM may be required, as compared to 400- 600 GSM for a regular DMF product. Such a starting material may be difficult to insert in a forming mould without pre-forming it.

In another example, the starting material is a cellulose fluff pulp sheet or a cardboard sheet containing substantially only cellulose fibres. The fluff pulp sheet or the cardboard sheet may be stacked in several layers in order to obtain a desired starting material. With such a material consisting of stacked fluff pulp or cardboard sheets, a pre-forming may not be necessary, depending on how it is inserted into the forming mould. The starting material may also be cellulose particles or cellulose granules containing substantially only cellulose fibres. The granules or particles may be inserted directly into the forming mould.

During the moulding of a three-dimensional HD-DMF cellulose product, different forces will act on the high purity cellulose material. When a flat two- dimensional cellulose product is moulded, all forming pressure forces acting on the high purity cellulose material will be in the same direction as the forming pressure direction, i.e. perpendicular to the mould surfaces. When a three- dimensional cellulose product is moulded, some of the forces will not be parallel to the direction of the forming pressure, but will be perpendicular to the mould surface. Since the high purity cellulose material does not float at lower pressures, the high purity cellulose material will be pulled apart somewhat in order to correspond to the three-dimensional shape of the mould, and this small displacement of the high purity cellulose material will, together with the high forming pressure, induce some shear forces on the high purity cellulose material, at least at some regions of the high purity cellulose material. Together with the high forming pressure, these shear forces will not be neglectable and will help to create some local pseudo-plastic regions where the high purity cellulose material will assume liquid-like properties. The shear forces may be increased by movement of one or both forming moulds during the moulding action, e.g. by vibrations and/or rotations of one or both forming moulds.

In one example, the high purity cellulose material is an air-laid cellulose blank comprising loose cellulose fibres. When an air-laid cellulose blank is used, the weight of the cellulose blank is preferably higher than the cellulose blank used for a regular DMF product, and may be in the region between 1000-3000 GSM. With such a material, a strong cellulose HD-DMF product with a density exceeding 1 ,30 g/cm³ can be obtained when moulded with a sufficiently high forming pressure.

In another example, the cellulose material is fluff pulp sheet or a cardboard sheet comprising compacted cellulose fibres. When fluff pulp sheet is used, preferably arranged as a roll of fluff pulp, the weight of the fluff pulp may be in the region between 300-800 GSM, and the thickness of a fluff pulp sheet may be between 2-4 mm thick, having a density of e.g. around 0,50 g/cm³ With such a standardized fluff pulp sheet, several layers of fluff pulp sheets may be stacked on each other one by one or rolled together in order to obtain a desired starting material. By stacking several layers of fluff pulp sheets, a strong cellulose HD-DMF product with a density exceeding 1 ,30 g/cm³ can be obtained when moulded with a sufficiently high forming pressure.

In another example, the cellulose material is a granular cellulose material containing substantially only cellulose fibres particles, where the cellulose fibres particles are more or less compacted. When a granular cellulose material is used, the density of the granules may be lower than the density of the formed cellulose product, and may be in the region between 0,4-0, 8 g/cm³. With such a material, a strong cellulose HD-DMF product with a density exceeding 1 ,30 g/cm³ can be obtained when moulded with a sufficiently high forming pressure.

The high purity cellulose material consists substantially of only cellulose fibres without any additives. With a high purity cellulose material is meant a material containing substantially only cellulose fibres, where as much as possible of the lignin is removed. Since it is practically impossible to remove all lignin, a small amount of lignin will remain in the cellulose material, where the lignin content is below 0,5%. The high purity cellulose material may also be referred to as lignin-free. Such a material is produced from chemical pulp where most of the lignin and the hemicelluloses are removed, leaving substantially only cellulose fibres. The high purity cellulose material will thus comprise at least 90% cellulose fibres, preferably at least 95% cellulose fibres and up to 98% cellulose fibres or more.

The high purity 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 high purity cellulose material comprises at least 95% 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 a binder material will definitely reduce the number of hydrogen bonds.

One suitable product made from cellulose HD-DMF is a screw lid for a bottle. The screw lid 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 lid will resemble a regular plastic screw lid 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% is possible if desired. In this way, it is possible to provide an internal thread on the inner surface of the screw lid, while the outer surface can be substantially smooth and even. It is of course also possible to provide the outer surface of the screw lid 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.

Another suitable cellulose HD-DMF product is a neck of a dry moulded cellulose fibre bottle, where the neck is provided with an external thread and a smooth inner surface. The rest of the bottle can be produced with a regular DMF forming pressure of 10-20 MPa in order to save cost.

The cellulose HD-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.

BRIEF DESCRIPTION OF DRAWINGS

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

Figs. 1 a-j show schematically a method for producing a cellulose HD-DMF product from an air-laid cellulose blank structure according to the disclosure,

Figs. 2a-f show schematically a method for producing a cellulose HD-DMF product from a paper pulp sheet according to the disclosure, and

Figs. 3a-d show schematically a method for producing a cellulose HD-DMF product from cellulose granules according to the disclosure,

Fig. 4 shows schematically a further method for producing a cellulose HD-DMF product according to the disclosure,

Fig. 5 shows schematically an example of a cellulose HD-DMF product according to the disclosure,

Fig. 6 shows schematically a method for producing a cellulose HD-DMF product using a rotary press according to the disclosure,

Fig. 7 shows schematically an example of a cellulose HD-DMF product produced by a rotary press according to the disclosure,

Fig. 8a-f shows schematically an example of a method for producing a cellulose HD-DMF product according to the disclosure, Fig. 9 shows schematically an example of a cellulose HD-DMF product according to the disclosure,

Fig. 10 shows schematically a further example of a cellulose HD-DMF product according to the disclosure,

Fig. 11 shows schematically a further example of a cellulose HD-DMF product according to the disclosure, and

Fig. 12 shows schematically a further example of a cellulose HD-DMF product according to the disclosure.

DESCRIPTION OF EXAMPLE EMBODIMENTS

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.

In the present detailed description, a method for producing a cellulose HD- DMF product from a high purity cellulose material will be described. The method is suitable for different products that should exhibit a higher strength and a higher density than regular 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 pods, golf pegs, toys, candy enclosures, flower pots, 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 high purity cellulose material used to form the cellulose HD-DMF product is a cellulose material containing substantially only cellulose fibres. With a high purity cellulose material is meant a material containing substantially only cellulose fibres. Such a material is produced from chemical pulp where most of the lignin and the hemicelluloses are removed, leaving substantially only cellulose fibres. Additives may also be added to the high purity 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 high purity cellulose material comprises at least 95% cellulose fibres by dry weight and at the most 5% additives by weight. The high purity cellulose material will also comprise some water, e.g. between 6% to 25% by weight. Water is not seen as an additive, it is necessary to create hydrogen bounds between the cellulose fibres but most will evaporate when the cellulose product is heated in an oven.

Figs. 1 a-j show schematically a method for producing a cellulose HD-DMF product from an air-laid cellulose blank. When forming the cellulose blank in the 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 high purity 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 may have a dryness that is mainly corresponding to the ambient humidity in the atmosphere surrounding the cellulose blank. Additional water may be added to the cellulose blank, such that a water content of between 6 to 25% by weight is reached. A lower water content is possible, but may be difficult to reach due to the humidity in the ambient air. In one example, the water content of the cellulose blank is in the region around 20%. A higher water content in combination with shear forces will increase the flowability of the cellulose fibres.

In Fig. 1 a, a section 2 of cellulose material that is cut out from the cellulose blank is inserted into a pre-forming mould 3. The cellulose blank section 2 may also be air-laid directly in the required size and shape. The basis weight of the cellulose blank section 2 may e.g. be 1000 GSM (gram per square meter). The pre-forming mould 3 comprises a first part 4, here a male mould part, and a second part 5, here a female mould part. The first male part 4 is in the shown example a fixed cylindrical mandrel arranged to pre-form the inner part of the pre-form. The second female part 5 is in the shown example circular and is provided with a variable size, such that the diameter of the second female mould part can be changed. A spraying nozzle 11 may spray some water on the cellulose blank section before or after the cellulose blank section is inserted into the pre-form mould if required.

In the described example, the second female part 5 is a bent steel belt 12 where the inner end 13 of the steel belt is fixed to the bottom of the pre-form mould. By pulling or pushing the outer end 14 of the steel belt, the diameter of the second female part can be varied. The second female part may also have other designs, where the inner size of the mould part can be changed, e.g. a female part having movable sections.

In Fig. 1 b, the pre-forming of the pre-form 6 has started by compressing the cellulose blank section 2 with the steel belt 12. In one example, the cellulose blank section may be compressed to a weight of 2000 GSM by pulling the outer end 14 of the steel belt 12 with a pulling force F1. When the cellulose blank section is compressed to a suitable weight, the pre-forming of the pre-form continues with lowering the first male part 4 into the cellulose blank section, as shown in Fig. 1 c. The first male part is pressed into the cellulose blank section with a pre-forming pressure F2. The outer diameter t2 of the first male part 4 corresponds more or less to the inner diameter of the cellulose product 1 . The first male part is lowered with a distance such that the thickness L2 of the bottom of the pre-form 6 is reached.

When the end position of the first male part 4 is reached and the desired thickness of the bottom 15 of the pre-form is reached, the side walls 16 of the cellulose blank section are further compressed by pulling the steel belt with a pulling force F3, as shown in Fig. 1 d. The weight of the cellulose blank section may now be raised to e.g. 3000 GSM, which may be a desired weight for the pre-form. The weight and thus the density of the bottom 15 and the side wall 16 of the pre-form 6 may be similar, but the main purpose of the pre-forming of the cellulose blank section is to reduce the size of the pre-form such that it is easier to insert into the forming mould and such that it will be easier to handle the pre-form. The pre-form may e.g. be produced at a remote location.

In Fig. 1 e, the pre-form is ready and released from the pre-forming mould 3 by raising the first male part 4 and pushing the steel belt back to the starting position. The pre-form 6 is provided with a height L1 , the outer diameter of the pre-form is R3, the inner diameter is t2, and the thickness of the bottom 15 is L2. The thickness of the side wall 16 is (R3-t2)/2.

In order to produce the cellulose product 1 , the pre-form 6 is inserted into the forming mould 7. A schematic forming mould 7 is shown in Fig. 1f, 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 mandrel is R3, 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 pre-form 6 is inserted into the second mould part 9 of the forming mould 7. Since the pre-form has been pre-formed in the pre-forming mould, the pre-form fits easily in the forming mould. Fig. 1g shows a cut view of the pre-form 6 and the forming mould 7. The mandrel 8 is lowered towards the second mould part 9, and in Fig. 1 h, the mandrel starts to press on the pre-form. In Fig. 1 i, the mandrel has reached its lowermost position, and an upper stop surface of the mandrel bears on the second lower mould part. In this way, a predefined volume of the cavity is created, in which the liquid-like cellulose fibres can float and which will allow the complete cavity to be filled. The amount of cellulose fibres compressed in the mould will at least partly 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 assumes liquid-like properties 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 pre-form is exposed to the high forming pressure, and the cellulose fibres will become pseudo-plastic due to the high forming pressure and some shear forces. The cellulose fibres will displace in the forming mould and will fill the forming mould completely since the cellulose fibres will assume liquid-like properties. The pseudo-plastic behaviour 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 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. The high forming pressure and the fact that the cellulose fibres must be displaced some from the position in the pre-form to the position in the cellulose product, thus creating some shear forces on the cellulose material, adds to the pseudo-plastic state of the cellulose fibres. The high pressure and the shear forces acting on the cellulose fibres creates the pseudo-plastic state. After a specified holding time, the cellulose product is ready and can be removed from the forming mould.

In Fig. 1 j, the cellulose product 1 is removed from the forming mould by raising the mandrel 8 from the second mould 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 mandrel 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, pattern and look of the screw cap.

Figs. 2a-f show schematically an example of a method where the cellulose HD- DMF product is made from a fluff pulp sheet as a starting material, where the fluff pulp contains substantially only cellulose fibres. The starting material may also be a cardboard sheet containing substantially only cellulose fibres. The fluff pulp sheet is in the example stored on a large fluff pulp roll 17. In Fig. 2a, smaller pre-formed rolls 18 of fluff pulp are cut from the roll of fluff pulp. The fluff pulp may be sprayed with water by a spraying nozzle 11 in order to control the desired humidity of the pre-formed roll. Additional water may be added to the fluff pulp, such that a humidity of between 6% to 25% by weight is reached. In the shown example, the large fluff pulp roll 17 is cut lengthwise into strips having a width L1 in a continuous manner. The strips are then cut to the desired length and are rolled to a pre-formed roll 18, having an outer diameter R3 which corresponds to the inner diameter of the forming mould. This will make it easy to insert the pre-formed roll into the forming mould.

The weight of the fluff pulp is in one example 700 GSM, which means that three turns of such a strip gives a pre-formed roll of approximately 2000 GSM. The width of the strip, i.e. the height of a pre-formed roll is determined based on the desired cellulose fibre content in the final cellulose HD-DMF product. Since the pre-formed roll does not have a bottom part, the height or the thickness of the pre-formed roll must compensate for the lack of a bottom, such that the required amount of cellulose fibres in the final cellulose HD-DMF product is obtained.

In Fig. 2b, the pre-formed roll 18 is inserted into the forming mould 7. The forming mould may be the same as described above, where a cellulose HD- DMF product is moulded from an air-laid cellulose blank, or may be adapted to the fluff pulp roll method. But since the final cellulose HD-DMF product is the same, a similar forming mould may be used.

A schematic forming mould 7 is shown in Fig. 2b, 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 mandrel is R3, 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 pre-formed roll 18 is inserted into the second mould part 9 of the forming mould 7.

Fig. 2c shows in a cut view the pre-formed roll 18 and the forming mould 7, where the mandrel 8 is lowered towards the second mould part 9, and where the mandrel starts to press on the pre-formed roll. The pre-formed roll will displace and parts of the pre-formed roll will be pushed down, towards the bottom of the second mould part 9. This is shown in more detail in Fig. 2d, where most of the pre-formed roll has been compressed. The mandrel is pushed down with a pressing force F4 until the mandrel has reached its lowermost position and an upper stop surface of the mandrel bears on the second lower mould part, as is shown in Fig. 2e. With a sufficient amount of cellulose fibres in the 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 pre-formed roll is exposed to the high forming pressure, and the cellulose fibres will become pseudo-plastic due to the high forming pressure and shear forces and the cellulose fibres will displace in the forming mould, filling the forming mould completely since the cellulose fibres will assume liquid-like properties. The pseudo-plastic behaviour will allow the cellulose fibres to fill the forming mould evenly.

The high forming pressure and the fact that the cellulose fibres are displaced from the position in the pre-formed roll to the position in the final cellulose HD- DMF product adds to the pseudo-plastic state of the cellulose fibres. The high pressure and the shear forces acting on the cellulose fibres creates the pseudo-plastic state. After a specified holding time, the cellulose HD-DMF product is ready and can be removed from the forming mould.

In Fig. 2f, the completed cellulose HD-DMF product is removed from the forming mould by raising the mandrel 8 from the second 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 mandrel 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 part is provided with the desired shape, pattern 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 granular high purity cellulose material containing substantially only cellulose fibres as a starting material. The granular high purity cellulose material may e.g. be cellulose granules or other smaller cellulose particles, such as cellulose pellets .cellulose fluff or separate cellulose fibres which may be more or less pre-compressed in order to be easier to handle. The granular cellulose material may comprise additives that will increase the resistance of the cellulose product to withstand liquids, grease, oil, heat etc. 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 25% by weight.

In Fig. 3a, the granular material 19 is inserted into the forming mould 7. The schematic forming mould 7 shown in Fig. 3a 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 mandrel is R3, 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 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 mandrel 8 is lowered towards the second mould part 9, as is shown in Fig. 3b, and the mandrel starts to press on the granular material, which is compressed. In Fig. 3c, the mandrel has reached its lowermost position and an upper stop surface of the mandrel bears on the second lower mould part. 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 product, the granular material is exposed to the high forming pressure, and the cellulose fibres will become pseudo-plastic due to the high forming pressure, shear forces acting on the cellulose fibres and the displacement of the cellulose fibres in the forming mould, filling the forming mould completely since the cellulose fibres will assume liquid-like properties. The pseudo-plastic behaviour will allow the cellulose fibres to fill the forming mould evenly.

The high forming pressure and the fact that the cellulose fibres are displaced from the position in the granular cellulose material to the position in the cellulose product adds to the pseudo-plastic state of the cellulose fibres. The high pressure and the shear forces acting on the cellulose fibres creates the pseudo-plastic state. 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 mandrel 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 mandrel 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 part is provided with the desired shape, pattern and look of the screw cap.

Fig. 4 shows a further example of a method for producing a cellulose HD-DMF product, in the shown example a bottle neck, as shown in Fig. 5. The bottle neck comprises a threaded section 10 arranged on the outer surface 23 of the bottle neck, where the inner surface 22 of the bottle neck is smooth and even. In the method, a cellulose blank section 2 is placed in the forming mould 7. The forming mould 7 comprises in the shown example an inner mould part 27, in this case a circular rod, and an outer mould part 28, comprising one or more movable parts. The cellulose blank section is in one example shaped as a long tubular section, where the part that is to be formed as a bottle neck is placed in the forming mould. The remainder of the tubular section may be formed to a cellulose bottle in a further forming step. The cellulose blank section may be placed directly in the forming mould, or may be pre-formed in a pre-forming mould, as described above. The cellulose blank section 2 is placed around an inner mould part 27, which will form the inner surface 22 of the bottle neck. In the shown example, the inner mould part 27 is smooth and even, such that a smooth inner surface of the bottle neck is obtained.

When the cellulose blank section is positioned around the inner mould part, the movable parts of the outer mould part 28 are moved towards the inner mould part 27, thereby compressing the cellulose blank section. The amount of cellulose fibres in the cellulose blank section together with the dimensions of the forming mould is selected such that the density of the bottle neck is greater than 1 ,30 g/cm³ or more. To reach such a density, a forming pressure exceeding 100 MPa or more is used to form the bottle neck. With such a high forming pressure, the cellulose fibres will assume liquid-like properties such that the cellulose fibres will fill all the threaded portions of the outer mould part. When the bottle neck is formed, the forming mould is opened and the bottle neck is removed from the forming mould and may be positioned in a further forming mould where the bottle is formed as a regular DMF product formed with a forming pressure of e.g. 4-20 MPa.

As shown in Fig. 5, the thickness of the side wall 21 of the bottle neck is t1 , and the thickness of the widest thread section is t2. The difference between t1 and t2 may be at least 200%, and may be up to 300-400%. In the example shown in Fig. 5, the threaded section comprises two thread sections having flat intermediate sections without thread sections. This will simplify the required tooling of the forming mould.

Fig. 6 shows an example where a cellulose HD-DMF product is formed in a rotary press 29. The rotary press 29 comprises a first base mould structure 30 and a second base mould structure 31 , where the first base mould structure and the second mould base structure are embodied as forming wheels having essentially circular peripheral shapes. The first base mould structure is provided with a plurality of first mould parts 32 arranged on the outer periphery of the first mould base structure and the second base mould structure is provided with a plurality of second mould parts 33 arranged on the outer peripheries of the second mould base structure. The first mould parts and the second mould parts are rotatably arranged in relation to each other, and arranged as discrete mould parts that are interacting with each other during the forming of the three-dimensional cellulose products.

The first mould parts 32 and the second mould parts 33 thus have mould shapes corresponding to the three-dimensional shape of the cellulose products to be produced. As an example shown in Fig. 6, the first mould parts 32 may be shaped as male moulds and the second mould parts 33 may be shaped as corresponding female moulds. Alternatively, the first mould parts 32 may be shaped as female moulds and the second mould parts 33 may be shaped as corresponding male moulds. The first mould parts 32 and the second mould parts 33 may also each have both male and female mould sections, depending on the shape of the three-dimensional cellulose products to be produced.

The first base mould structure 30 is configured for rotating around a first rotational axis in a first rotational direction, and the second bas mould structure 31 is configured for rotating around a second rotational axis in a second rotational direction. The cellulose blank section 2 is inserted in the rotating press, between the rotating first base mould structure and the second base mould structure, in order to form the cellulose HD-DMF product.

During forming of the three-dimensional cellulose products, the rotary press 29 is configured to heat the cellulose blank section 2 to a forming temperature in the range of 100°C to 300°C with suitable heating means, e.g. integrated electrical heating means. The rotary press is further configured to forming the cellulose products from the cellulose blank section 2 in the rotary press by pressing the heated cellulose blank section 2 with a forming pressure of at least 100 MPa, or preferably at least 150 MPa or more, between a first mould part 32 and a second mould part 33. With the high forming pressure together with a predefined relationship between the distance between the first and the second mould part and the weight of the cellulose blank section, a density greater than 1 ,30 g/cm³ and preferably greater than 1 ,40 g/cm³ or more of the cellulose product can be obtained.

Fig. 7 shows an example of a cellulose HD-DMF product produced in a rotary press. The shown example is a blister pack that may be used to store single pills or the like, such as medicine or candy. The storage sections of the blister pack are closed with a rupturable film that protects the pills from the environment. Figs. 8a-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 blank section 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.

In the example shown in Fig. 8a, a cellulose section having a sidewall preform part 36 corresponding to a side wall 21 of the final cellulose product and a bottom preform part 37 corresponding to a bottom 20 of the final cellulose product is cut out from the cellulose blank structure of the fluff pulp roll. Other cutting pattern are also possible, as long as the cut out parts corresponds somewhat to the periphery of the final cellulose HD-DMF product. It is an advantage to let the parts adhere to each other, which will simplify the handling of the cellulose blank section. Fig. 8b shows the cellulose blank section folded to a preform shape resembling the final cellulose product.

In Fig. 8c, the folded cellulose blank section is inserted into a forming mould 7. The forming mould comprises a first male mould part 8 and a second female 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. 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. 8d shows in a cut view the folded cellulose blank section 2 and the forming mould 7, where the mandrel 8 is lowered towards the second mould part 9. The mandrel 8 is provided with a hollow section 38 extending around the periphery of the mandrel, which is arranged to form a rim on the final cellulose product. When the mandrel 8 is lowered, the cellulose blank section will be pressed against the inner sides of the second mould part and will displace some. The mandrel is pushed down with a pressing force F until the mandrel has reached its lowermost position and an upper stop surface of the mandrel bears on the second lower mould part, as is shown in Fig. 8e. 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 the cellulose fibres will become pseudo-plastic due to the high forming pressure and the cellulose fibres will displace in the forming mould, filling the forming mould completely since the cellulose fibres will assume liquid-like properties. The rim 25 will be formed by the hollow section 38, where cellulose fibres will fill the hollow section completely. The rim 25 is in the shown example thicker than the side wall of the final cellulose product. The pseudo-plastic behaviour will allow the cellulose fibres to fill the forming mould evenly.

The high forming pressure and the fact that the cellulose fibres are displaced some from the position in the folded cellulose blank section to the position in the final cellulose HD-DMF product adds to the pseudo-plastic state of the cellulose fibres. The high pressure and the shear forces acting on the cellulose fibres creates the pseudo-plastic state. After a specified holding time, the cellulose HD-DMF product is ready and can be removed from the forming mould. In Fig. 8f, the completed cellulose HD-DMF product 1 is removed from the forming mould by raising the mandrel 8 from the second part 9.

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. 9. The cap comprises a bottom section 20 and a circular side wall 21 having an outer surface 23 and an inner surface 22. The inner surface is in one example provided with a protruding element 24 in the form of a threaded section 10 comprising one or more protruding elements formed as the threaded section. The cap may also comprise a snap lock having a rim section that is arranged to snap to a rim of a container. A cap is a product well suited to be produced with the inventive method, since it is relatively small and has a relatively difficult shape that requires varying wall thickness of the product.

Fig. 10 shows a coffee pod, another product that is well suited to be produced with the inventive method. The coffee pod comprises a bottom section 20 and a circular side wall 21 having an outer surface 23 and an inner surface 22. The coffee pod further comprises a rim 25, where the thickness of the rim is several times thicker than the side wall. A thickness difference of 300-400% is possible to achieve with the inventive method. The bottom section 20 is also provided with one or more penetration regions 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 pod can be made thinner than surrounding sections. A further advantage of the inventive method is that a deep drawn coffee pod can be produced, due to the pseudoplastic behaviour of the high purity cellulose material under the high forming pressure. A coffee pod may also be provided with some sections having a different thickness, such as a bottom of the coffee pod having thinner areas where the bottom is to be penetrated, or a thicker rim section. Figs. 6 and 7 shows examples of cup-like cellulose products having protruding elements. The cup-like cellulose product comprises a bottom section 20 and a circular side wall 21 having an outer surface 23 and an inner surface 22. 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. 11 shows a cup-like product having protruding elements arranged at the inner surface of the 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. 12 shows a cup-like product having protruding elements arranged at the outer surface of the product. The shape and the number of the protruding elements may vary. A cellulose product having one or more protruding elements arranged on the outer surface is preferably made in a forming mould having several sections for the negative form 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. A suitable moulding temperature level is in the range of 100°C to 300°C.

It will be appreciated that the above description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. While specific examples have been described in the specification and illustrated in the drawings, it will be understood by those of ordinary skill in the art that various changes may be made, and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure as defined in the claims. Furthermore, modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure is not limited to the 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 SIGNS

1 : Cellulose product

2: Cellulose blank section

3: Pre-forming mould

4: First part

5: Second part

6: Pre-form

7: Forming mould

8: First mould part

9: Second mould part

10: Threaded section

11 : Spraying nozzle

12: Steel belt

13: Inner belt end

14: Outer belt end

15: Pre-form bottom

16: Pre-form side wall

17: Fluff pulp roll

18: Pre-formed roll

19: Granular material

20: Bottom section

21 : Side wall

22: Inner surface

23: Outer surface

24: Protruding element

25: Rim

26: Penetration region

27: Inner mould part

28: Outer mould part

29: Rotary press

30: First base mould structure 31 : Second base mould structure

32: First mould part

33: Second mould part

34: Blister pack 35: Film

36: Preform side wall

37: Preform bottom

38: Hollow section

Claims

1. A method for producing a three-dimensional cellulose High Density Dry Moulded Fibre product (1 ) from a high purity cellulose material (2; 17; 19) comprising at least 95% cellulose fibres, 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 high purity cellulose material in the forming mould (7); and forming the cellulose product (1 ) from the high purity cellulose material in the heated forming mould (7), by pressing the high purity cellulose material (2; 17; 19) with a forming pressure of at least 100 MPa to obtain a density of the cellulose product (1 ) greater than 1 ,30 g/cm³

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

3. A method according to claim 1 or 2, wherein the forming pressure is at least 200 MPa.

4. A method according to any of claims 1 to 3, wherein the cellulose product (1 ) is formed by compression moulding.

5. A method according to any of claims 1 to 3, wherein the cellulose product (1 ) is formed by rotary moulding.

6. A method according to any of the preceding claims, wherein the high purity cellulose material (2; 17; 19) contains less than 25% water.

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

8. A method according to any of claims 1 to 6, wherein the high purity cellulose material is fluff pulp or cardboard (17).

9. A method according to any of claims 1 to 6, wherein the high purity cellulose material is a granular material (19.

10. A method according to any of the preceding claims, wherein the high purity cellulose material comprises at least 98% cellulose fibres by dry weight.

11 . A three-dimensional cellulose High Density Dry Moulded Fibre product (1 ) formed from a high purity cellulose material (2) comprising at least 95% cellulose fibres, c h a r a c t e r i z e d i n that the cellulose product (1 ) has a density greater than 1 ,30 g/cm³

12. A product according to claim 11 , wherein the density is greater than 1 ,40 g/cm³.

13. A product according to claim 11 or 12, wherein the wall thickness of the cellulose product (1 ) varies with at least 200%.

14. A product according to any of claims 11 to 13, wherein the cellulose product (1 ) comprises a bottom section (20) and a circular side wall (21 ) having an outer surface (23) and an inner surface (22), where the inner surface (22) is provided with at least one protruding element (24), and where the outer surface (23) is substantially even.

15. A product according to any of claims 11 to 13, wherein the cellulose product (1) comprises a bottom section (20) and a circular side wall (21 ) having an outer surface (23) and an inner surface (22), where the outer surface (23) is provided with at least one protruding element (24), and where the inner surface (23) is substantially even.

16. A product according to any of claims 11 to 15, wherein the cellulose product is formed with a forming pressure exceeding 100 MPa.