SE545966C2

SE545966C2 - Method for obtaining a coated fiber-based product comprising cellulose fibers

Info

Publication number: SE545966C2
Application number: SE2151158A
Authority: SE
Inventors: Chuantao Zhu; Frank Peng; Sohrab Kazemahvazi
Original assignee: Stora Enso Oyj
Priority date: 2021-09-22
Filing date: 2021-09-22
Publication date: 2024-03-26
Also published as: SE2151158A1

Abstract

A method for obtaining a coated fiber-based product comprising cellulose fibers, said method comprising the steps of providing a fiber-based product (1) comprising cellulose fibers; providing a printing plate (2) comprising at least one recess (3); providing a volume (40) of a liquid material (4) to said recess of said printing plate; applying a printing pad (6) into said recess; allowing said liquid material comprised in the recess to adhere to an outside surface (60) of said printing pad, moving the printing pad comprising said adhered liquid material on said outside surface of said printing pad from the recess; and contacting a surface of said fiber-based product with said printing pad and allowing the adhered liquid material to leave said outside surface of the printing pad and to instead adhere to a surface (10; 100) of said fiber-based product thereby creating a coating layer (8).

Description

Technical field The present invention relates to a method for obtaining a coated fiber-based product comprising cellulose fibers.

The present invention also relates to a three-dimensional molded pulp structure made by means of the method.

Background There is a growing interest for producing cellulose-based products for use as packaging applications for foodstuff, tableware, trays, technical products, electronic equipment and/or consumer goods. Several advantages are associated with the use of natural fibers (such as cellulose fibers) for manufacturing packages. Being a renewable resource, natural fibers provide a sustainable alternative to other packaging materials such as aluminum and plastics, and furthermore natural fibers are both recyclable and biodegradable. Natural fibers include cellulose fibers of any natural origin, such as derived from wood pulp and/or plants.

Molding of cellulose fiber materials provides a way of achieving renewable articles with various three-dimensional shapes, which may be used to differentiate products available for sale in a given market place.Manufacturing molded fiber products can be done by wet forming, wherein a forming tool is dipped into an aqueous pulp composition followed by compression-molding performed under heat, resulting in a dried fiber product having a shape complementary to the shape of the mold. Typically, said tool is perforated or porous so that water can be removed from the suspension or wet pulp during forming during a dewatering/drying step.

It is also possible to dry mold products such as trays from a cellulose fiber sheet or web. Dry molding can be done in various ways, e.g. by press-forming a wetted sheet combined with applied heat using a forming tool.

While there is a demand for environmentally friendly packaging products, especially single-use food packaging products, a known problem with moulded pulp products is it has proven difficult to provide barrier properties. Packages for food requires adequate grease resistance, or water repellence properties, or both. To impart such properties to a moulded article of cellulose, a surface treatment or coating method is often required. In addition, the coating should preferably have properties that not only improves the properties but also facilitates the manufacturing of the moulded articles without compromising repulpability and recyclability. Prior art discloses ideas to provide desired properties to the moulded products, e.g. post-coating the moulded product with barrier coating layer.

An example is disclosed in WO11/O65911 wherein a resilient pad is submerged into a bath containing a liquid surface barrier material for uptake of said liquid surface barrier material onto theresilient pad whereafter the pad is pressed against the surface of a fiber product for creating a barrier layer. The fiber product is placed inside of and supported by a porous mold during the application of the liquid surface barrier material. A suction is applied through the pores of the mold during the application of the liquid surface barrier material. However, there are several disadvantages with this technology for creating a barrier. For instance, using a bath with a large excess of liquid surface barrier material leads to an extensive waste of liquid surface barrier material. The amount of liquid surface barrier material applied to the fibrous product cannot be controlled meaning that no proper controlthe amount of the surface barrier layer is possible during the production and further that optimization of the application is not possible. Moreover, the coating barrier material could be sucked into the formed product, either destroying the functional coating layer on the surface or Wasting more barrier materials going into the bulk. Therefore, this is not a sustainable and economical way of applying barrier properties to fibrous products.

There is a remaining need for cellulose-based, surface treated or coated products where the coating preferably has properties that not only improves the product properties but also facilitates the manufacturing of the articles as well as sustainability, repulpability and recycling. There is also a need of reducing the total amount usage of coating chemicals, leading to a more reusable and environmentally friendly products.

Obiect of the inventionIt is an object of the present invention, to provide an improved method for obtaining a coated fiber-based product comprising cellulose fibers.

Summary The object of the invention is at least partially obtained by means of a method for obtaining a coated fiber-based product comprising cellulose fibers according to c|aim 1. Said method comprises at least the steps of: -providing a fiber-based product comprising cellulose fibers; -providing a printing plate comprising at least one recess; -providing a volume of a liquid material to said recess of said printing plate; -applying a printing pad into said recess; -allowing said liquid material comprised in the recess to adhere to an outside surface of said printing pad, -moving the printing pad comprising said adhered liquid material on said outside surface of said printing pad from the recess; -contacting a surface of said fiber-based product with said printing pad and allowing the adhered liquid barrier material to leave said outside surface of the printing pad and to instead adhere to the surface of said fiber-based product thereby creating a coating layer.

Thanks to the inventive method, there is achieved a very accurate way of creating a coating layer due to that the volume of the liquid material provided to the recess is directly proportional to the thickness of the coating layer. That is, by controlling/adjustingthe volume of liquid material provided to the recess, the thickness of the coating layer may also be controlled/adjusted.

Furthermore, the method results in a surprisingly even thickness of the obtained coating layer, aiming for the bottom and side wall parts, also effective at difficult parts of the fiber-based material, e.g. at edges, corners, on both smooth and rough su rfaces.

These are all great improvements as compared to the coating methods described in the background prior art.

The dependent claims are related to preferred embodiments. They may be combined freely unless the context clearly indicates otherwise.

Brief description of the drawincls The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: Fig. 1a is a schematic view of technical parts comprised in a pad printing device for performing the inventive method for obtaining a coated fiber-based product; Fig. 1b shows, in a schematic way, a fiber-based product ready to undergo the inventive method; Figs. 2a-2f schematically show a number of steps comprised in the inventive method.

Detailed description Before the invention is disclosed and described in detail, it is to be understood that the terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting since the scope of the present invention is limited only by the appended claims and equivalents thereof.

"Printing plate" is in its broadest sense a flat surface comprising a recess. The printing plate typically offers a smooth and flat, most often horizontal, surface into which a cavity has been created. In this context the cavity is termed a recess, in other contexts the recess is often denoted a relief. The printing plate may typically be made from steel or polymers, but other materials are conceivable too, and the invention is not limited to the choice of material of the plate.

"Recess" is used herein to denote a three-dimensional space having a volume in the plate. Said volume is defined by a bottom surface and one or more wall surface/-s, the number of walls depending on the shape of the recess, which can be of an irregular shape, or a more well-defined shape, e.g. rectangular, square, cylindrical etc. The shape may further comprise concave and/or convex parts. Said volume is an open volume having no upper ceiling closing the volume.

"Printing pad" or "pad" is used herein to denote a cushion, which is made of a resilient and flexible material, typically of, but not limited to, silicone. Thanks to the flexible material the pad can easily adapt its shape to a surrounding shape of a recess whenbeing pressed/applied/submerged into the recess. The hardness of the pad may be determined by the amount of silicon oil used when the pad is manufactured, i.e. the harder the pad, the less silicone oil was added during manufacture.

"Pad printing" is used herein to denote a process for printing of two- or three-dimensional objects by making use of a flexible printing pad. Pad printing is an indirect offset printing process. Conventionally, the pad printing process is used for transferring an image from a printing plate (often termed cliché) via a printing pad onto a substrate.

"Liquid material" is used herein to denote a material in liquid form. The liquid material is applied to a surface of fiber-based products such as paper or board to form a solid, non-porous film after drying covering essentially the whole surface, i.e. covering more than 900/0, preferably 95% or more and most preferred 98% or more of the surface to be covered (coated) by the applied liquid material.

"Coating" and "coating layer" as used herein denotes covering more than 900/0, preferably 95% or more and most preferred 98% or more of a surface with a continuous layer of a coating, i.e. a coating layer.

Fig. 1a is a schematic view of a pad printing device D. Said pad printing device D comprises a printing plate 2 and a printing pad 6 held by a holderThe printing plate 2 may in its simplest form be any flat surface which preferably is also a horizontal surface. Said printing plate 2 may be a surface of a table or a plate resting on a table or a stand. The printing plate 2 comprises a recess 3 having a well- defined volume 30, said volume 30 may be a variable volume or a fixed volume. In embodiments where the volume 30 is a variable volume, a bottom surface and/or a wall surface of the volume 30 may preferably be arranged to be adjustable. The recess 3 is arranged to comprise a volume 40 of a liquid material The recess 3 is typically created in the printing plate 2 by any therefore appropriate process, e.g. laser etching or acid etching. The inventive idea is not limited to the kind of process of creating the recess.

Preferably the bottom surface and the wall surfaces of the recess 3 are smooth.

Embodiments are however conceivable where said surfaces of the recess 3 are textured.

Preferably, the printing pad 6 is a resilient and flexible pad having a vertical center axis A. Said vertical center axis A is preferably coinciding with a vertical center axis of said recess 3, and preferably also with a vertical center axis of the holder The printing pad 6 has an outside surface In Fig. 1A, said printing pad 6 is arranged in a position such that said printing pad 6 is ready to be dipped or pressed (dependingon a relation between a size of the printing pad 6 and the volume 30 of said recess 3) into the recess 3 comprising the volume 40 of the liquid material Fig. 1b is a schematic view of a fiber-based product 1 comprising cellulose fibers. As can be seen the fiber-based product 1 shown in Fig. 1b has a convex shape and is an example of a three-dimensional (3D) fiber-based product.

For three-dimensional (3D) fiber-based products, it may be an advantage if the shape of the printing pad 6 has a complementary shape to a shape of a surface 10 of the fiber-based product 1, as shown in Figs. 1a and 1b. Adapting the shape of the printing pad 6 to the shape of the 3D fiber-based product 1 may result in a more uniform adherence of the liquid material 4 from the outside surface 60 of the printing pad 6 to the surface 10 of the fiber-based product For 3D fiber-based products 1 it may further be preferred that also the recess 3 has a shape that is essentially of the same shape as the shape of the surface 10 of the 3D fiber-based product 1, or at least similar to the shape of the surface 10 of the 3D fiber-based product 1. A shape of the recess 3 adapted to the shape of the 3D fiber-based product 1 may result in a more uniform adherence of the liquid material 4, first to the outside surface 60 of the printing pad 6, and then to the surface 10 of the 3D fiber-based product 1, thereby resulting in a more even coating layer on the surface 10 of the 3D fiber-based product From reading the above it is understood that for 3D fiber- based products 1 it is preferred that all of the shapes, i.e. of the recess 3, printing pad 6, and the fiber-based product 1, may be the same or at least similar with regards to their dimensions.

For the 3D fiber-based product as shown in Fig. 1b, the surface 10 of the fiber-based product 1 to be contacted with the printing pad 6 is preferably an inside surface 100 of said fiber- based product 1, i.e. herein the concave surface.

In other embodiments, not shown, said fiber-based productmay be a two-dimensional (2D) fiber-based product.

Figs. 2a-2f schematically show the main steps of the method according to the invention.

In Fig. 2a the printing pad 6 is arranged by the holder 7 in a starting position above the recess 3 comprised in the printing plate 2 (the same position as shown in Fig. 1a). The liquid material 4 preferably occupies 90 vol-O/o or more of said volume 30 of the recess 3, and most preferred at least 98 vol-O/o or more. Said liquid material 4 preferably fills the total volume 30 of said recess 3. In embodiments where the volume 30 of the recess 3 is completely filled with liquid material 4, the volume 40 of the liquid material equals the volume of the recess Fig. 2b shows that a movement of the printing pad 6 in a downwardly direction towards the recess 3 occurs. The printing pad 6 is pressed into said recess 3 and a step of applying the printing pad 6 into the recess 3 has thereby been performed.The printing pad 6 is, as already discussed, preferably made of a flexible material and due to this flexibility, said printing pad 6 adapts its shape to the shape of the recess 3 when being pressed into the recess 3, i.e. it deforms to some extent during pressing into the recess. When the printing pad 6 is pressed into the recess 3, the liquid material 4 kept in the recess 3 adheres to the outside surface 60 of the printing pad Preferably 90 vol-O/o or more, more preferred 95 vol-O/o or more, and most preferred 98 vol-% or more, of the volume 40 of liquid material 4 comprised in the recess 3 is adhered to said outside surface 60 of said printing pad Fig. 2c illustrates an upward movement of the printing pad 6, now comprising said adhered liquid material 4 on its outside surface 60. The holder 7 vertically lifts the printing pad 6 up from the recess 3. Preferably the movement is at least initially performed along the center axis A of the printing pad 6 / holder After having lifted the printing pad 6 upwardly, the holder 7 moves the printing pad 6 and positions the printing pad 6 in a position above the fiber-based product 1, as shown in Fig. 2d. Preferably the vertical center axis A of the printing pad 6 coincides with a vertical center axis of the fiber-based product 1. (The skilled person understands the fiber-based product 1 may be moved to the printing pad 6 instead of the other way around.) An adhered layer of liquid material 4 on the surface 60 of the printing pad 60 is shown in Fig. 2d. An area of the liquid materialon the surface 60 preferably corresponds essentially to an area of the surface 10 of the fiber-based product 1 intended to be coated.

In Fig. 2e a downward, and preferably vertical, movement of the printing pad 6 is performed by the holder 7 such that the printing pad 6 comes into a direct contact with the surface 10, 100 of said fiber-based product 1 thereby allowing the adhered liquid material 4 to leave said outside surface 60 of the printing pad 6 and to instead adhere to the surface 10, 100 of said fiber-based product 1. Upon contacting the surface 10, 100 of the fiber-based product, the printing pad 6 is pressed towards said surface such that it is at least slightly deformed, securing that the liquid material 4 is properly transferred from the pad 6 to the fiber-based product 1, i.e. the liquid material 4 is transferred from the pad 6 to the surface 10, 100 of said fiber-based product under applied pressure. Thereby, a creating coating layer 8 is created on the surface 10, 100 of said fiber-based product Fig. 2f schematically shows the vertical movement of the printing pad 6 upwardly and away from the fiber-based productnow comprising the coating layer Preferably, 90 vol-O/o or more of the volume 40 of said liquid material 4 adhered to said outside surface 60 of said printing pad 6 will in the direct contact with the surface 10, 100 of the fiber-based product 1 adhere to said surface 10, 100 of the fiber-based product 1. More preferred, 98 vol-O/o or more of the volume 40 of said liquid material 4 adhered to said outside surface 60 of said printing padwill instead adhere to said surface 10,Preferably 90 %, and more preferred 95 % or more of the area of the surface 10, 100 of said fiber-based product 1 has now been covered by said adhered liquid material 40 resulting in one layer 8 of a continuously coating on said fiber-based product 1, i.e. one layer 8 of coating has been applied to the fiber-based product For fiber-based products comprising only one coating layer 8, the method for obtaining a coated fiber-based product is completed after the step shown in Fig. 2f. A coated fiber-based product comprising cellulose fibers has hereby been obtained.

However, it is conceivable, most often a reality, that the fiber- based product 1 may have two or more layers of coatings. The cycle of the method for obtaining a coated fiber-based product as shown in the Figs. 2a-2f may then repeated as many times as the number of coating layers 8 needed.

Preferably, one layer of coating will have a dry weight in an interval of 1-20 gsm, more preferred 5-15 gsm and most preferred 9-11 gsm.

Said pad printing device D comprises at least one container comprising liquid material 4. Said container is preferably arranged in a sealing contact with the printing plate 2 such that the container is moveable over a surface of the printing plate 2 while still keeping the sealed contact. The container delivers liquid material 4 to the recess 3 before immersion of the printing pad 6 into the recess 3. The container may preferably be closed and performs a doctoring function over the printing plate 2 during operation. Delivery of theliquid material 4 to the recess 3 takes place when the container has moved from a starting position and is positioned in a delivery position above the recess 3. Scraping off of any delivered excess liquid material 4 to the recess 3 occurs when the container moves from the delivery position back to the starting position thereby securing delivery of a controlled and exact volume 40 of the liquid material 4 to the volume 30 of the recess It is conceivable that the container, in some embodiments, does not move, but instead the printing plate 3 moves under the container. Irrespective which of the printing plate 3 or the container is moveable, the end result is that the surface of the printing plate 2 is cleaned up and the recess 3 has been filled with a controlled volume 40 of the liquid material In some embodiments the pad printing device may comprise two containers. A first container may comprise a liquid precoating material, e.g. a varnish, and a second container may comprise a liquid barrier material.

It is conceivable that the pad printing device further comprises a third container comprising e.g. a post-coating liquid.

The working operation of the moveable container will not be described in more detail here since that operation may be performed in any conventional and known way.

Preferably, the inventive method for obtaining a coated fiber- based product further comprises at least one cleaning step. This cleaning step may be performed by a cleaning station comprised in or outside the printing device D. In said cleaning step the outside surface 60 of the printing pad 6 may be cleaned. Preferably said cleaning step is performed after the printing pad 6 has contacted the surface 10, 100 of the said fiber-based product 1 and the adhered liquid barrier material has left the outside surface 60 of the printing pad 6 and instead adhered to the surface 10, 100 of said fiber-based product 1. During the cleaning step any rest of liquid material (4) that may still remain on the outside surface 60 of the printing pad 6 after the contact with the surface 10, 100 of the fiber-based product 1, i.e. that has not adhered to the surface 10, 100 of the fiber-based product 1, will be removed from the outside surface 60. After the performed cleaning step the outside surface 60 of the printing pad 6 is free, or at least essentially free, from liquid material 4 and ready to undergo a next cycle of the method.

In some embodiments it is conceivable that the cleaning step of the outside surface 60 of the printing pad 6 may not be performed after every delivery of liquid material 4 to the surface 10, 100 of the fiber-based product 1, but only when there is a change of a chemical composition of the liquid material Embodiments are conceivable wherein the fiber-based product 1 is supported/held by a mold during contacting the surface 10, 100 of said fiber-based product 1 with said printing pad The method preferably comprises at least one drying step for drying of the of the fiber-based product comprising one or more coating layer/-s and/or the coated fiber-based product. Said drying step may comprise hot air drying, microwave and/or IR drying but other drying techniques are however conceivable.The method may comprise additional method steps without departing from the scope of the invention.

For example, said method for obtaining a coated fiber-based product may further comprise a spraying step for spray coating and /or a dipping step for dip coating one or more parts of said fiber- based product wherein said one or more parts may be chosen from any of edges and /or corners and / or flat parts of said fiber-based product.

According to one aspect of the invention, the fiber-based product is a molded fiber-based product. In the following, an example of a wet molding method for manufacturing a 3D molded fiber-based product will be described, which manufactured 3D molded fiber-based product will obtain a coating layer according to the inventive method.

An aqueous pulp suspension (also referred to as “composition”) is provided with the consistency of O.O5-1Owt°/0. The pulp may be any one of wood pulps, non-wood pulps, unbleached chemical pulp, defibrated fiber material, bagasse, straws, bamboo, spruce CTMP, eucalyptus CTMP, spruce HT CTMP, kraft pulp, sulphate, sulphite, PGW, GW, DIP, recycled paper and board, broke, RMP, TMP, CMP, CSP NSSC nanopulp, dissolving pulp, and regenerated fibers or mixtures thereof. A 3D shaped forming tool comprising a forming portion is brought into contact with the pulp suspension, for instance by dipping or immersing said tool into the slurry bath. Said forming portion is arranged to represent a 3D mirror image of the article to be formed. Pulp is drawn onto theforming portion e.g. by means of vacuum suction until a layer of desired thickness has been formed, whereupon the forming tool is removed from the slurry. At this stage, the forming portion is covered with a wet layer of pulp, said wet layer comprising between 5-150 gsm (g/m2) in dry weight. Next, the wet layer of pulp is dewatered to a dry content of at least 70 wt°/0. Dewatering and/or drying can be done in various ways. In a wet curing procedure, the wet layer is pressed under elevated temperatures to be compressed and dried to a certain thickness, thereby yielding a smooth external surface for the end structure. In a dry curing process, the wet layer is subjected to heated air thereby removing moisture, which results in an end structure with a more textured finish. This way, a single layer molded fiber product is formed.

Manufacturing multilayered molded fiber products can be accomplished for instance by applying more than one fibrous layer on top of each other in consecutive molding production steps. For instance, a layer of metal salt-containing pulp can be molded onto a pre-molded pulp layer already present on the forming tool. The various layers of a multilayered product may hereby provide different functions, such as rigidity, barrier properties, etc.

According to the invention, the hot press temperature range for a wet molded procedure is around 150-220 degrees C, with a press range around 1-10 bar.

A dry grammage of the molded product is preferably 100-500 gsm or more preferably 200-400 gsm, and a dry density is between 100-1200 kg/m3, preferably 200-1000 kg/m3 or most preferably 400-800 kg/mOnce the 3D molded fiber-based product has been dried to a desired dryness, said 3D molded fiber-based product will undergo the method according to the invention as defined in claim 1 and any one of the dependent claims so as to obtain a coating layer on an inside of the 3D molded fiber-based product.

The coated fiber-based products made by means of the method of the present invention may be referred to as packages and/or packaging material, and include in a non-limiting way bowls, cups, capsule, pots, containers, trays and packages.

Examples of fiber-based products suitable for the inventive method are fiber-based products having irregular surfaces and/or surfaces characterized by high surface roughness.

The invention is not limited to any special kind of manufacturing method of the fiber-based product comprising cellulose fibers.

The skilled person appreciates that the invention may contemplate any fiber-based manufacturing method, including conventional wet forming procedures and dry forming procedures, wet molding procedures, dry molding procedures, three- dimensional (3D) printing techniques and air laid techniques.

The invention is not limited to the chemical composition of the liquid material. The liquid material may be chosen from a variety of chemical compositions and the choice depends on the properties wanted for the specific application/product.In some embodiments, the fiber-based product may be intended to contain foodstuff in which case the liquid material is a liquid barrier material, and the obtained coating layer is a barrier layer preferably arranged at the food-contacting side of the product, for instance on the inside of a tray.

Commonly, there is a most often a need to improve the barrier properties of the surface (inside and/or outside surface) of the fiber-based product against grease, oil, liquid, moisture and/or oxygen. It is advantageous that the formed barrier layer is impervious, or at least resistant, to grease, oil, liquid, moisture, aroma and/or oxygen.

When barrier properties are desirable for the fiber-based product, the liquid barrier material may preferably be a dispersion barrier material, an emulsion barrier material or any other kind of liquid barrier material that provides barrier properties to the fiber- based product when applied to a surface of said fiber-based product.

The dispersion barrier material may comprise fine polymer particles, such as latex and optionally pigments. Alternatively, the dispersion barrier material may comprise starch and hydrophobic polymers such as Wax, styrene maleic anhydride (SMA) and/or or an alkyl ketene dimer (AKD) or a copolymer of ethylene and PVOH further including optionally hydrophobic polymers. Such a dispersion coating applied on the surface of the fiber-based product may serve as a sufficiently efficient barrier against moisture arising from condensation. In addition, the barrier layer provides good optical properties resulting in a surface of a thereof formed packaging suitable for printing.

The liquid barrier material may preferably have a Brookfield viscosity in a range of 100 - 2000 mpa.s, more preferred 200-1200 mpa.s, and most preferred 350 - 800 mpa.s using spindle 4, atFpm meaSUFement.

It may further be advantageous that the formed barrier is biodegradable.

The liquid material may further be chosen from a pigment coating liquid material, a varnish, e.g. a food-contacting varnish, and/ or a Wax in liquid form.

The present invention has been described with regard to preferred embodiments. However, it will be obvious to a person skilled in the art that a number of variations and modifications can be made without departing from the scope of the invention as described herein.

The printing pad may be used not only for delivery of barrier layers but also for delivery of functional materials, such as, but not limited to, conductive inks, adhesives, dyes, flavours, nutritional additives, conservatives, and lubricants, to the surface of the fiber- based product.

The method may further be used also for delivery of aqueous starch solution, protein solution, styrene-based polymers, styrene acrylate-based polymers, styrene butadiene polymers, non-ionicacryl polymers, ammonia salt of modified acrylic polymers, proteins, and/or cellulose derivatives to the surface of the fiber- based product.

It is conceivable to firstly deliver liquid functional materials to the surface of the fiber-based product followed by delivery of one or more liquid barrier materials on top of the delivered liquid functional materials. Any drying step may be performed between and/or after the deliveries. It is also conceivable to deliver liquid functional materials as a middle-layer or a finishing layer on an already barrier coated fiber-based product.

Claims

1. A method for obtaining a coated fiber-based product comprising cellulose fibers, said method -~__providing a fiber-based product (1) comprising cellulose fibers; -providing a printing plate (2) comprising at least one recess (3); -providing a volume (40) of a liquid material (4) to said recess (3) of said printing plate (2); -applying a printing pad (6) into said recess (3); -allowing said liquid material (4) comprised in the recess (3) to adhere to an outside surface (60) of said printing pad (6), -moving the printing pad (6) comprising said adhered liquid material (4) on said outside surface (60) of said printing pad (6) from the recess (3); -contacting a surface of said fiber-based product (1) with said printing pad (6) and allowing the adhered liquid material (4) to leave said outside surface (60) of the printing pad (6) and to instead adhere to a surface (10; 100) of said fiber-based product (1), thereby creating a coating layer (8).

2. A method according to claim 1, Wherein the printing pad (6), upon contacting the surface of said fiber-based product (1), is pressed against said surface such that it is deformed, for transferring said liquid material (4) from the pad (6) to the surface (10; 100) of said fiber-based product (1).

3. A method according to claim 1 or 2, wherein 90 vol-O/o or more of said volume (40) of liquid material (4) comprised in the recess (3) is adhered to said outside surface (60) of said printing pad (6).

4. A method according to any one of the previous claims, wherein 90 vol-O/o or more of the volume (40) of said liquid material (4) adhered to said outside surface (60) of said printing pad (6) will, in contact with the surface (10; 100) of the fiber-based product (1), adhere to said surface (10; 100) of the fiber-based product (1).

5. A method according to any one of the previous claims, wherein 90 % or more of an area of the surface (10; 100) of said fiber-based product (1) is being covered by said adhered liquid material (4) resulting in one layer of coating (8) on said fiber-based product (1).

6. A method according to any one of the previous claims, wherein one layer of coating (8) preferably will have a dry weight in an interval of 1-20 gsm.

7. A method according to any one of the previous claims, wherein the method is repeated for one and the same fiber-based product (1) such that the surface (10; 100) of the fiber-based product (1) will have two or more coating layers (8).

8. A method according to any one of the previous claims, wherein a cleaning step is arranged for cleaning said outside surface (60) of said printing pad (6), preferably said cleaning stepis arranged after the printing pad (6) has been in contact with said surface (10; 100) of said fiber-based product (1).

9. A method according to any one of the previous claims, wherein the method further comprises a spraying step for spray coating one or more parts of said fiber-based product (1); said one or more parts is/ are chosen from any of edges and /or corners and/ or flat parts of said fiber-based product.

10. A method according to any one of the previous claims, wherein said method further comprises a dipping step for dip coating one or more parts of said fiber-based product; said one or more parts is/ are chosen from any of edges and /or corners and / or flat parts of said fiber-based product.

11. A method according to any one of the previous claims, wherein at least one drying step is arranged for drying said fiber- based product comprising one or more coating layer/-s.

12. A method according to any one of the previous claims, wherein at least one drying step is arranged for drying said coated fiber-based product.

13. A method according to any one of the previous claims, wherein said liquid material is chosen from dispersion barriers, emulsion barriers, suspension barriers, pigment coatings, varnishes, pre-coating liquids, post-coating liquids.

14. A method according to any one of the previous claims, wherein said fiber-based product is a three-dimensional molded fiber-based product.

15. A method according to any one of the previous claims, wherein the steps of the method are being performed on an inside surface of said three-dimensional molded fiber-based product.

16. A method according to any one of the previous claims, wherein said fiber-based product comprises ce||u|ose pulp selected from the group comprising: wood pulps, non-wood pulps, unbleached chemical pulp, defibrated fiber material, bagasse, straws, bamboo, spruce CTMP, eucalyptus CTMP, spruce HT CTMP, kraft pulp, sulphate, sulphite, PGW, GW, DIP, recycled paper and board, broke, RMP, TMP, CMP, CSP NSSC nanopulp, dissolving pulp, and regenerated fibers and mixtures thereof.

17. A method according to any one of the previous claims, wherein the grammage of the molded product is

18. A method according to any one of the previous claims, wherein said molded product comprises a density between 100- 1200 kg/m3, preferably 200-1000 kg/m3 or most preferably 400- 800 kg/m

19. A method according to any one of the previous claims, wherein a viscosity of a liquid barrier material is Within the range of 100-2000 mpa.s using spindle 4, at 100 rpm measurement.