A method for producing a cellulose product and a cellulose product

Abstract

A method for producing a cellulose product and a cellulose product (1) formed from a multi-layer cellulose blank structure (2), where the cellulose product (1) is formed in a heated forming mould (7) by pressing the multi-layer cellulose blank structure (2) with a forming pressure of at least 1 MPa, where the cellulose product (1) comprises a first tissue layer (4) arranged on a first side of a dry-formed cellulose fibres layer (3), a plastic layer (6) arranged on a second side of the dry-formed cellulose fibres layer (3) and a second tissue layer (5) arranged on the plastic layer (6).

Description

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

[0002] CELLULOSE PRODUCT

[0003] TECHNICAL FIELD

[0004] The present disclosure relates to a method for producing a three-dimensional shaped cellulose product from a first tissue layer, a layer of dry-formed cellulose fibres, a plastic layer and a second tissue layer. The present disclosure also relates to a three-dimensional shaped cellulose product.

[0005] BACKGROUND

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

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

[0008] 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.

[0009] SUMMARY

[0010] An object of the present disclosure is to provide a method for producing a cellulose product where the previously mentioned problems are avoided. This object is at least partly achieved by the features of the independent claim. The dependent claims contain further developments of the method for producing a cellulose product. Another object of the present disclosure is to provide a three- dimensional shaped cellulose product.

[0011] The disclosure concerns a method for producing a cellulose product from a first tissue layer, a layer of dry-formed cellulose fibres, a plastic layer and a second tissue layer, wherein the method comprises the steps of; forming a cellulose blank structure from a dry-formed cellulose fibres layer; arranging a first tissue layer on a first side of the dry-formed cellulose fibres layer; arranging a plastic layer on a second side of the dry-formed cellulose fibres layer; arranging a second tissue layer on the plastic layer; and heating the multi-layer cellulose blank structure to a forming temperature in the range of 100°C to 300°C, forming the cellulose product from the multi-layer cellulose blank structure in a forming mould, by pressing the heated multi-layer cellulose blank structure with a forming pressure of at least 1 MPa, preferably 4-20 MPa, wherein the multi-layer cellulose blank structure is shaped into the three- dimensional cellulose product.

[0012] Advantages with these features are that the method provides an efficient manufacturing process for cellulose products with improved mechanical and chemical properties, where the cellulose products can be manufactured with high precision. The method also provides a cost-efficient and rational production of cellulose products through its few simple steps compared to traditional production methods. By the use of a plastic layer between the dry- formed cellulose fibres layer and the second tissue layer, a resulting cellulose product that is resistant to e.g. grease, hot liquids, cold liquids and other substances that normally affects a cellulose product formed from only cellulose fibres. By applying the plastic layer between the dry-formed cellulose fibres layer and the second tissue layer and not as the outer layer, a product with the same feel as a product formed from only cellulose fibres is provided.

[0013] The plastic layer or plastic film may be relatively thin, with a thickness of e.g. between 5-200 micrometres. The plastic layer should be as thin as possible but should still be possible to handle in the production line. Since the only purpose of the plastic layer is to protect the dry-formed cellulose fibres layer from moist, grease etc, under a relatively short time period, the plastic layer must not be vapor tight. The cellulose product may e.g. be a spoon, a lid, a tray or a salad bowl that is intended to be used as a disposable product for a short time period. The plastic layer may be made from a fossil or non-fossil plastic. Suitable plastic types may e.g. be PE, PLA, PP, PVC, bio-based polymers such as viscose, lyocell, cellophane, etc, and the like.

[0014] One advantage of using a plastic layer between the dry-formed cellulose fibres layer and the second tissue layer is that the impression of the product by a user is familiar, such that the user does not notice any difference of the rear side and the front side of the product. Having e.g. a tissue layer as the rear side layer and a plastic layer as the front side layer would create an unpleasant impression for a user. The first tissue layer and the second tissue layer may also be treated with an additive if desired. By treating the first tissue layer and the second tissue layer with the same additive, the impression for a user will be the same.

[0015] Another advantage of using a plastic layer between the dry-formed cellulose fibres layer and the second tissue layer is that the plastic layer will improve the adherence of the second tissue layer to the dry-formed cellulose fibres layer. The plastic layer can act as a glue layer between the dry-formed cellulose fibres layer and the second tissue layer. This will ensure that the second tissue layer does not delaminate during use, e,g, when the cellulose product is a food tray or a salad bowl. Depending on the type of plastic layer, the plastic layer may also increase the strength of the cellulose product.

[0016] The dry-formed cellulose fibres layer preferably has a fibre composition of 95- 100% cellulose fibres or natural cellulose fibres. The first tissue layer and the second tissue layer preferably have a fibre composition of 95-100% cellulose fibres or natural cellulose fibres.

[0017] The dry-formed cellulose fibres layer is formed in a dry-forming process where the cellulose fibres are carried and formed to the fibre layer structure by air as carrying medium.

[0018] The cellulose product is formed in the forming mould during a forming time period in the range of 0.1 to 20 seconds, and preferably 1 to 10.0 seconds. The forming time together with the forming temperature and the forming pressure are important parameters in the forming of the cellulose product.

[0019] The first tissue layer and / or the second tissue layer and / or the dry-formed cellulose fibres layer may comprise one or more additives that are altering the mechanical, hydrophobic, and / or oleophobic properties of the cellulose product. The one or more additives of the first tissue layer and / or the second tissue layer may be starch compounds, rosin compounds, butanetetracarboxylic acid, gelatin compounds, alkyl ketene dimer (AKD), Alkenyl Succinic Anhydride (ASA). By using additives, the properties of the cellulose product can be efficiently steered and controlled. The additives can alter the mechanical, hydrophobic, and / or oleophobic properties so that the cellulose product can be used for different purposes. For example, it can be possible to create a scratch free surface by the use of a starch compound as an additive. It should be noted that the list of additives is not exhaustive in the meaning that other additives and / or chemical substances can be added for a designed property of the final product.

[0020] According to other aspects of the disclosure, the one or more additives of the first tissue layer and / or the second tissue layer and / or the dry-formed cellulose fibres layer have been added to the layers before forming the multi-layer cellulose blank structure. In this way, the additives could be added to the respective layer during the production of the tissue layers, or in a process step before the multi-layer cellulose blank structure is formed. The additives may also be added to the layers when the multi-layer cellulose blank structure has been formed in the production line before the cellulose product is pressed.

[0021] The cellulose product according to the invention is provided with a base layer made from air-laid dry-formed cellulose fibres that forms a dry-formed cellulose fibres layer. The cellulose product further comprises a first tissue layer arranged on a first side of the dry-formed cellulose fibres layer, a plastic layer arranged on a second side of the dry-formed cellulose fibres layer and a second tissue layer arranged on plastic layer.

[0022] The plastic layer will ensure that the cellulose product can withstand various substances, such as grease, hot liquids or cold liquids. The cellulose product is preferably a product that normally is exposed to a substance from one side, such as a food tray, a lid for e.g. a coffee cup, a salad bowl or the like.

[0023] According to an aspect of the disclosure, the multi-layer cellulose blank structure is heated in the forming mould. This provides an efficient heating of the multi-layer cellulose blank structure. According to another aspect of the disclosure, the cellulose product is shaped into a three-dimensional structure from the multi-layer cellulose blank structure during the forming in the forming mould. During the forming of the cellulose product in the forming mould, the cellulose product will achieve its three- dimensional shape.

[0024] According to another aspect of the disclosure, the plastic layer is a polyethylene (PE) film, polyamide (PA) film, polypropylene (PP) film, polylactic acid (PLA) film, coated aluminium structure, cellulose structure laminated with a thermoplastic material, cellulose structure coated with wax, or cellulose structure coated with silicon.

[0025] According to a further aspect of the disclosure, the plastic layer is biodegradable.

[0026] BRIEF DESCRIPTION OF DRAWINGS

[0027] The disclosure will be described in greater detail in the following, with reference to the attached drawings, in which

[0028] Fig. 1 shows schematically, a method for producing a cellulose product from a multi-layer cellulose blank structure according to the disclosure, and

[0029] Fig. 2a-b shows schematically, a cellulose product produced from a multilayer cellulose blank structure according to the disclosure.

[0030] DESCRIPTION OF EXAMPLE EMBODIMENTS

[0031] 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 product from a multi-layer cellulose blank structure will be described.

[0032] Embodiments of sheet materials or blanks according to the disclosure are mainly discussed with reference to a multi-layer cellulose blank structure placed in position for forming in a forming mould, where the multi-layer cellulose blank structure has a flat shape. It should be noted that this will not limit the scope of the present disclosure, which for example may include, a multi-layer cellulose blank structure pre-shaped into a three-dimensional shape. The multi-layer cellulose blank structure may be presented to the forming mould in a shape similar to the desired final shape of the object if desired.

[0033] A cellulose product according to the disclosure may be made in a three- dimensional shape or formed into a three-dimensional shape from a two- dimensional blank or sheet material.

[0034] Figure 1 schematically shows a method for producing a cellulose product 1 from a multi-layer cellulose blank structure 2, where the multi-layer cellulose blank structure 2 comprises a dry-formed cellulose fibres layer 3, a first tissue layer 4, a second tissue layer 5 and a plastic layer 6.

[0035] With a dry-formed cellulose fibres layer is meant a cellulose fibre layer that is formed in a dry-forming process in which cellulose fibres are air-laid to form the cellulose fibre layer. When forming the cellulose fibre layer in the air-laid process, the cellulose fibres are carried and formed to the fibre layer structure by air as carrying medium. In the air-laid process, small amounts of water or other substances may if desired be added to the cellulose fibres in order to change the properties of the cellulose product, but air is still used as carrying medium in the forming process. The layer of dry-formed cellulose fibres may have a dryness that is mainly corresponding to the ambient humidity in the atmosphere surrounding the layer of dry-formed cellulose fibres. To produce the cellulose products, the multi-layer cellulose blank structure may be arranged as a layered continuous web. The multi-layer continuous web may be formed from the layers in a continuous process step, where the continuous web is fed to the forming mould to form the cellulose products.

[0036] In the embodiment shown in Fig. 1 , the dry-formed cellulose fibres layer 3 is produced from loose and separated fibres produced in a mill 11 in a known manner, where defibrated fibres are fed by air as a carrying medium from the mill to a suitable substrate (not shown) to form the dry-formed cellulose fibres layer. The first tissue layer 4 is provided on a first tissue roll 8, the second tissue layer 5 is provided on a second tissue roll 9 and the plastic layer 6 is provided on a third roll 10.

[0037] As shown in figure 1 , a first pair of pressure feed rollers 13 may be used for compacting the dry-formed cellulose fibres layer 3 if required. A second set of pressure feed rollers 14 may be used to compact and unwind the first tissue layer 4, the second tissue layer 5, and the plastic layer 6.

[0038] In this embodiment the first tissue layer 4 is arranged below the dry-formed cellulose fibres layer 3, and the plastic layer 6 and the second tissue layer 5 are arranged above the dry-formed cellulose fibres layer 3, but the layers may suitably be arranged in the opposite order, depending on the used forming mould.

[0039] The second pair of pressure feed rollers 14 may be arranged so that the rollers are pushed against each other with a force Fi , and when the layers are passing between the pair of pressure feed rollers 14, the layers are compacted and forming the multi-layer cellulose blank structure 2. The force Fi may be chosen so that a desired compacting of the layers is achieved. Other suitable means may be used instead of the pair of pressure feed rollers 14, such as for example motorized unwinders for the web rolls.

[0040] As a non-limiting example, in order to achieve a desired compacting of the multi-layer cellulose blank structure, the force Fi of the pair of pressure feed rollers 10 may be in the range 2000 N to 17000 N, and the multi-layer cellulose blank structure may have a width of 0.6 m. The pair of pressure feed rollers 14 may be heated, for example to a temperature in the range of 70 °C to 170 °C, so that the multi-layer cellulose blank structure is heated during the compression in the pair of pressure feed rollers 14. The heating of the multilayer cellulose blank structure during compression will form a compressed ductile web structure that is suitable for being transported to and formed in the forming mould.

[0041] In one example (not shown), a plastic layer 6 is also arranged between the first tissue layer 4 and the first side of the dry-formed cellulose fibres layer 3. By applying a plastic layer on each side of the dry-formed cellulose fibres layer 3 in a symmetrical manner, where each plastic layer is covered by a tissue layer, a product that can withstand grease, liquids etc from both sides of the cellulose product is obtained. This is e.g suitable for cutlery where both sides are exposed to food.

[0042] Further according to the method, the multi-layer cellulose blank structure is arranged in the forming mould 7. The multi-layer cellulose blank structure may be arranged in the forming mould in any suitable way, and as an example, the multi-layer cellulose blank structure may be manually fed to and arranged in the forming mould.

[0043] The multi-layer cellulose blank structure could as an alternative be intermittently fed to the forming mould by a suitable feeding unit if the multilayer cellulose blank structure is arranged as a continuous web transported with a constant speed, and the forming of the cellulose products in the forming mould may take place in intermittent process steps. The multi-layer cellulose blank structure may for example be intermittently fed to the forming mould via a feeding unit in the form of a buffer zone arrangement, where a pivot roller arm with a lift roller lifts and bends the multi-layer cellulose blank structure in a gentle arc with a synchronized servo controlled movement. In this way, a suitable length of the multi-layer cellulose blank structure is buffered to enable on-demand incremental feeding of the multi-layer cellulose blank structure into the forming mould. When the pivot roller arm is lowered, the buffered multilayer cellulose blank structure can be fed intermittently to the forming mould. The pivot roller arm is thus lifted and lowered in a repeated manner to accomplish the buffering of the multi-layer cellulose blank structure, so that the multi-layer cellulose blank structure is intermittently fed to the forming mould, via for example feeding rollers arranged after the pivot roller arm.

[0044] The multi-layer cellulose blank structure is according to the disclosure further heated to a forming temperature in the range of 100°C to 300°C. The cellulose product is formed from the multi-layer cellulose blank structure in the forming mould by pressing the heated multi-layer cellulose blank structure with a forming pressure of at least 1 MPa, preferably 4-20 MPa. By heating the multilayer cellulose blank structure and pressing the multi-layer cellulose blank structure in the forming mould, the cellulose product is formed, where during the forming the multi-layer cellulose blank structure is shaped into a three- dimensional fibre composite structure having a single-layer configuration.

[0045] In the embodiment shown in figure 1 , the multi-layer cellulose blank structure 2 is heated and formed into the cellulose product 1 , where the cellulose product

[0046] 1 is having a three-dimensional bowl-shaped product configuration. However, as described above, the cellulose product 1 may have any desired three- dimensional shape. The first tissue layer 4 and the second tissue layer 5 are unwound from the first tissue roll 8 and the second tissue roll 9 respectively, and the plastic layer 6 is unwound from the third roll 10, and the layers may be compressed by the second set of pressure feed rollers 14. In this way, the multi-layer cellulose blank structure 2 is formed.

[0047] In order to form the cellulose product, the multi-layer cellulose blank structure

[0048] 2 is positioned in the forming mould 5, where the multi-layer cellulose blank structure 2 is heated to a forming temperature in the range of 100°C to 300°C and then pressed in the forming mould 7 with a forming pressure of at least 1 MPa, preferably 4-20 MPa. The heating of the multi-layer cellulose blank structure 2 may take place before arranging the multi-layer cellulose blank structure 2 in the forming mould 7 or at least partly before the pressing in the forming mould 7. This may for example be accomplished through arranging a suitable heating unit in the manufacturing process. As an alternative, the heating of the multi-layer cellulose blank structure 2 may take place in the forming mould 7 when being pressed. The heating of the multi-layer cellulose blank structure 2 may for example be accomplished through heating the forming mould 7 before pressing the multi-layer cellulose blank structure 2.

[0049] When pressing the cellulose fibres, the cellulose fibres will be bonded to each other in a way so that the resulting cellulose product will have good mechanical properties. Tests have shown that higher forming temperatures will give stronger bonding between the cellulose fibres when being pressed at a specific forming pressure. With forming temperatures above 100°C together with a forming pressure of at least 1 MPa, preferably 4-20 MPa, the cellulose fibres will be strongly bonded to each other with hydrogen bonds. At temperatures higher than 300°C, the cellulose fibres will be thermally degraded and therefore temperatures above 300°C should be avoided. The forming pressure and the forming temperature may be chosen to be suitable for the specific cellulose product to be produced.

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

[0051] An example of a cellulose product 1 is shown in Figs. 2a and 2b. In this embodiment, the cellulose product is a food tray. The cellulose product comprises a first tissue layer 4, a dry-formed cellulose fibres layer 3, a plastic layer 6 and a second tissue layer 5. The first tissue layer 4 is arranged on one side of the dry-formed cellulose fibres layer 3, in the shown example below the dry-formed cellulose fibres layer 3. The plastic layer 6 is arranged on the other side of the dry-formed cellulose fibres layer 3, in the shown example above the dry-formed cellulose fibres layer 3, and the second tissue layer 5 is arranged on the plastic layer 6.

[0052] By applying the plastic layer 6 between the dry-formed cellulose fibres layer 3 and the second tissue layer 5 and not as the outer layer, a product with the same feel as a product formed from only cellulose fibres is provided. One such product is cutlery, where the product is used both with the hands of a user and in the mouth of a user. A user will be sensible to the feel and “taste” of the product, and will appreciate the same feel on both sides of the product. A further advantage is that the plastic layer adheres to both the dry-formed cellulose fibres layer 3 and the second tissue layer 5 in an improved way, i.e. the plastic layer 6 increases the bonding between the dry-formed cellulose fibres layer 3 and the second tissue layer 5. Since the second tissue layer 5 adheres to the plastic layer 4 in a reliable way, the cellulose product can be used for liquids without the need for additional additives, and the second tissue layer will not delaminate during use.

[0053] The food tray shown in Figs. 2a and 2b comprises a bottom 15, side walls 16 and an upper rim section 17 that will increase the strength of the food tray and that can be used for a sealing film. Other cellulose products comprising a plastic layer are of course also possible, such as cups, lids, cutlery etc. Products that must withstand heat, grease, liquids etc are especially suitable for this type of cellulose product.

[0054] 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.

[0055] REFERENCE SIGNS

[0056] 1 : Cellulose product

[0057] 2: Multi-layer cellulose blank structure

[0058] 3: Dry-formed cellulose fibres layer

[0059] 4: First tissue layer

[0060] 5: Second tissue layer

[0061] 6: Plastic layer

[0062] 7: Forming mould

[0063] 8: First tissue roll

[0064] 9: Second tissue roll

[0065] 10: Third roll

[0066] 11 : Mill

[0067] 12: Pressing unit

[0068] 13: First set of application roller

[0069] 14: Second set of application roller

[0070] 15: Bottom

[0071] 16: Side wall

[0072] 17: Rim

Claims

CLAIMS1 . A method for producing a cellulose product (1 ) from a multi-layer cellulose blank structure (2), wherein the method comprises the steps of; forming the multi-layer cellulose blank structure (2) from a dry- formed cellulose fibres layer (3); arranging a first tissue layer (4) on a first side of the dry-formed cellulose fibres layer (3), arranging a plastic layer (6) on a second side of the dry-formed cellulose fibres layer (3), arranging a second tissue layer (5) on the plastic layer (6); and heating the multi-layer cellulose blank structure (2) to a forming temperature in the range of 100°C to 300°C, and forming the cellulose product (1 ) from the multi-layer cellulose blank structure (2) in a forming mould (7), by pressing the heated multilayer cellulose blank structure (2) with a forming pressure of at least 1 MPa, preferably 4-20 MPa, wherein the multi-layer cellulose blank structure (2) is shaped into the three-dimensional cellulose product (1 ).

2. A method according to claim 1 , wherein the method further comprises the step of arranging a plastic layer (6) between the first tissue layer (4) and the first side of the dry-formed cellulose fibres layer (3).

3. A method according to claim 1 or 2, wherein the plastic layer (6) has a thickness between 5 - 200 micrometres.

4. A method according to any of claims 1 to 3, wherein the dry-formed cellulose fibres layer (3) is formed in a dryforming process where the cellulose fibres are carried and formed to the dry-formed cellulose fibres layer (3) by air as carrying medium.

5. A method according to any of the preceding claims, wherein the cellulose product (1 ) is formed in the forming mould (7) during a forming time period in the range of 1 to 10 seconds.

6. A method according to any of the preceding claims, wherein one or more additives are applied on the first tissue layer (4) and / or the second tissue layer (5) and / or the dry-formed cellulose fibres layer (3).

7. A cellulose product (1 ) formed from a multi-layer cellulose blank structure (2), where the cellulose product (1 ) is formed in a heated forming mould (7) by pressing the multi-layer cellulose blank structure (2) with a forming pressure of at least 1 MPa, c h a r a c t e r i z e d i n that the cellulose product (1 ) comprises a first tissue layer (4) arranged on a first side of a dry-formed cellulose fibres layer (3), a plastic layer (6) arranged on a second side of the dry-formed cellulose fibres layer (3), and a second tissue layer (5) arranged on the plastic layer (6).

8. A cellulose product (1 ) according to claim 7, wherein the cellulose product (1 ) further comprises a plastic layer (6) arranged between the first tissue layer (4) and the first side of the dry-formed cellulose fibres layer (3).

9. A product according to claim 7 or 8, wherein the cellulose product (1 ) is a food tray having a bottom (15), side walls (16) and a rim (17).

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