A method for producing a fiber based article

Abstract

There is provided a method for producing a moulded fiber based article. There is also provided a moulded fiber based article.

Description

TECHNICAL FIELD The present disclosure generally relates to a method for producing a fiber based article. The disclosure relates particularly, though not exclusively, to a method for producing a fiber based article by moulding a fiber stock. BACKGROUND This section illustrates useful background information without admission of any technique described herein representative of the state of the art. Pollution caused by single use plastic containers and packaging materials is epidemic, scarring the global landscape and threatening delicate ecosystems and the life forms that inhabit them. Single use containers migrate along waterways to the oceans in the form of Styrofoam and expanded polystyrene (EPS) packaging, to-go containers, bottles, thin film bags and photo-degraded plastic pellets. Sustainable solutions for reducing plastic pollution are gaining momentum. However, continuing adoption requires that these solutions not only be good for the environment, but also competitive with plastics from both a performance and a cost standpoint. By way of brief background, molded paper pulp (molded fiber) has been used since the 1930’s to make containers, trays and other packages, but experienced a decline in the 1970s after the introduction of fossil based plastic foam packaging. Paper pulp can be produced from old newsprint, corrugated boxes and other plant fibers. Today, molded pulp packaging is widely used for electronics, household goods, automotive parts and medical products, and as an edge / corner protector or pallet tray for shipping electronic and other fragile components. Cellulose fiber-based packaging products are biodegradable, compostable and, unlike fossil based plastics, do not migrate into the ocean. However, presently known fiber technologies are not well suited for use with meat and poultry, prepared food, produce, microwavable food, or as lids for beverage containers such as hot coffee. In particular, selectively integrating one or more oil, water, vapor, and / or oxygen barriers into the slurry, and / or selectively applying one or more of the barrier layers to all or a portion of the surface of the finished packaging product, can be cumbersome, time consuming, and expensive. Depending on molded pulp application, oil, grease, water, water vapor, oxygen and / or other gas or liquid barrier properties are needed in different container types. Use of suitable slurry chemicals can improve process efficiency, mechanical properties, barrier properties and / or surface coatability and therefore, make production of molded pulp products more competitive against products made from planar board. SUMMARY In a first aspect the present invention provides a method for producing a moulded fiber based article, the method comprising providing a fibre stock comprising cellulosic fibers; introducing to the fiber stock cationic emulsion polymer; and moulding the fiber stock. In a second aspect the present invention provides a moulded fiber based article, wherein the moulded fiber based article comprises cationic emulsion polymer and alkyl ketene dimer (AKD), or wherein the moulded fiber based article is produced with the method according to the present invention. In a third aspect the present invention provides a use of cationic emulsion polymer and AKD for improving dryness and Cobb values of a moulded fiber based article. It has now been surprisingly found that moulded, such as thermoformed, fiber based articles comprising cationic emulsion polymer has high dryness in vacuum dewatering, wet / cold pressing and / or hot press drying. The cationic emulsion polymer provides high dryness in vacuum dewatering, wet / cold pressing and / or hot press drying for the molded fiber based article. It has also been found that moulded, such as thermoformed, fiber based articles comprising cationic emulsion polymer haslow Cobb value. The lower the Cobb value is the better is water resistance, i.e. hydrophobicity. The cationic emulsion polymer provides low Cobb value for the molded fiber based article. The fiber based articles of the present invention are at least partly biodegradable and compostable, preferably mostly biodegradable and compostable, more preferably almost totally biodegradable and compostable, most preferably biodegradable and compostable. The appended claims define the scope of protection. BRIEF DESCRIPTION OF FIGURES Figure 1 shows effect of different cationic emulsion polymers (=Products 1 -4) on Cobb30min with 3 different AKD products. Figure 2 shows effect of different cationic emulsion polymers (=Products 1-4) on dryness after wet / cold press. Figure 3 shows effect of different cationic polymer product types on dryness after hot press. AKD dosage with all cationic polymers was 1.2 AKD wax 11 dry pulp. Figure 4 shows effect of cationic emulsion polymer on dryness after vacuum dewatering. DETAILED DESCRIPTION In a first aspect the present invention provides a method for producing a moulded fiber based article, the method comprising providing a fibre stock comprising cellulosic fibers; introducing to the fiber stock cationic emulsion polymer; and moulding the fiber stock. In one embodiment alkyl ketene dimer (AKD) is introduced to the fiber stock. In one embodiment the cationic emulsion polymer and AKD are introduced as a blend to the fiber stock. In one embodiment the cationic emulsion polymer and AKD are introduced sequentially to the fiber stock. In one embodiment the cationic emulsion polymer is introduced to the fiber stock prior introducing AKD to the fiber stock. In one embodiment the AKD is introduced to the fiber stock prior introducing the cationic emulsion polymer to the fiber stock. In one embodiment the cationic emulsion polymer and AKD are introduced simultaneously but separately to the fiber stock. In one embodiment the cationic emulsion polymer is water-soluble cationic emulsion polymer. The term “water-soluble” is understood in the context of the present application that the polymer product is fully miscible with water. When mixed with excess of water, the cationic emulsion polymer in the polymer product is preferably fully dissolved and the obtained polymer solution is preferably essentially free from discrete polymer particles or granules. Excess of water means that the obtained polymer solution is not a saturated solution. The cationic emulsion polymer has a net cationic charge as measured at pH 7. In one embodiment a net cationic charge of the polymer is in the range of 1.1 to 4.5 meq / g (dry), preferably 1.5 to 4.5 meq / g (dry), more preferably 3.5 to 4.5 meq / g (dry), measured at pH 7. The higher the charge of the polymer, the greater hydrophobics, ash, dyes, fines and / or starch fixation efficiencies are achieved. In one embodiment the cationic emulsion polymer has standard viscosity of 1.5-5.6 mPas, preferably 1.7 - 3.3 mPas, more preferably 1.7 - 3.0 mPas, even more preferably 1.7 - 2.5 mPas, most preferably 1.7 - 2.0 mPas, measured in a Brookfield viscometer with a LIL adapter at 25°C on a 0.1 percent, by weight, polymer solution in 1 M NaCI at 60 rpm. Standard (i.e. solution) viscosity SV values are relatively easier, i.e., less cumbersome and time consuming, to obtain than intrinsic viscosity values. Moreover, SV values can be correlated to IV values for a particular polymer. Thus, polymeric molecular weights can be approximated by reference to the solution viscosity of the polymer. That is, the higher the SV value for a particular polymer, the higher its molecular weight. Commonly, 5 mPas of standard viscosity is equal to about 10 million Dalton of polymer molecular weight, and 2 mPas is about 2 million Dalton expressed as molecular weight. According to an embodiment of the present invention, 1.7 - 2.5 mPas of SV corresponds about 2-3 million Dalton of polymer molecular weight. The cationic emulsion polymer is obtained by emulsion polymerization. Emulsion polymerization techniques are widely known to persons skilled in the art. The water-soluble cationic emulsion polymer is prepared by reverse phase emulsion polymerization and the obtained reverse phase emulsion of cationic polymer is inverted into an aqueous solution. Therefore the cationic polymers used in the method of the present invention are inverse emulsion polymers. In one embodiment the water-soluble cationic emulsion polymer is prepared by polymerizing a monomer blend comprising ethylenically unsaturated monomers. The watersoluble cationic polymer can be prepared by polymerizing a monomer blend comprising at least non-ionic and cationic monomers, preferably non-ionic and cationic ethylenically unsaturated monomers. In one embodiment a monomer blend may comprise non-ionic monomers, cationic monomers and anionic monomers. In one embodiment a water-soluble cationic polymer may be obtained by polymerizing a monomer blend comprising ethylenically unsaturated nonionic monomers, wherein 15-50 mol-%, preferably 15-40 mol-%, and more preferably 20 - 40 or 20 - 30 mol-% of the monomers are cationic or to be modified cationic, e.g. by hydrolyzing units originating from N-vinyl formamide monomer into vinylamine. In one embodiment, the cationic groups in the cationic polymer may originate from monomers selected from diallyldimethylammonium chloride (DADMAC); acryloyloxyethyltrimethylammonium chloride; methacrylates of N,N- dialkylaminoalkyl compounds; and quaternaries and salts thereof, such as N,N- dimethylaminoethylacrylate methyl-chloride salt; monomers of N,N- dialkylaminoalkyl (meth)acrylamides; and salts and quaternaries thereof, such as N,N-dialkylaminoethylacrylamides; methacrylamidopropyltrimethylammonium chloride; 1 -methacryloyl-4-methyl piperazine and the like. Quaternary amines are preferred cationic monomers because their charge is not pH dependent. In oe embodiment nonionic monomers may comprise acrylamide; methacrylamide; N-alkyl acrylamides, such as N- methylacrylamide, N,N-dialkylacrylamides, such as N,N-dimethylacrylamide; methyl acrylate; methyl methacrylate; acrylonitrile; N-vinylmethylacetamide or formamide; N-vinyl acetate or vinyl pyrrolidone, and the like. In one embodiment water-soluble polymers comprise acrylamide and at least one ethylenically unsaturated cationic monomer. In one embodiment the cationic emulsion polymer is cationic polyacrylamide emulsion polymer. In one embodiment a chain-transfer agent is used in the polymerization. Examples of chain transfer agents are alcohols; mercaptans; thioacids; phosphites and sulfites, such as isopropyl alcohol and sodium hypophosphite, although many different chain-transfer agents may be employed. In one embodiment a cross-linking agent is used in the polymerization. Examples of crosslinking agents are compounds containing at least two double bonds, such as methylenebisacrylamide; methylenebismethacrylamide; polyethyleneglycol diacrylate; polyethyleneglycol dimethacrylate; N-vinyl acrylamide; divinylbenzene; triallylammonium salts; N-methylallylacrylamide; and the like. Polyfunctional crosslinking agents containing at least one double bond and at least one reactive group include glycidyl acrylate; acrolein; methylolacrylamide; and the like. In one embodiment the cationic emulsion polymer is cross-linked cationic emulsion polymer or non-crosslinked cationic emulsion polymer. In one embodiment the cationic emulsion polymer is cross-linked cationic emulsion polymer. In one embodiment the cationic emulsion polymer is non-crosslinked cationic emulsion polymer. In one embodiment the cationic emulsion polymer is linear cationic emulsion polymer or branched cationic emulsion polymer. In one embodiment the cationic emulsion polymer is linear cationic emulsion polymer. In one embodiment the cationic emulsion polymer is branched cationic emulsion polymer. In one embodiment the cationic emulsion polymer is an interpenetrating polymer network polymer. In one embodiment the cationic emulsion polymer is introduced to the fiber stock in an amount of 0.01-40 kg / ton of dry fiber stock, preferably 0.05-1.5 kg / ton of dry fiber stock, more preferably 0.1-0.5 kg / ton of dry fiber stock. In one embodiment the AKD is introduced to the fiber stock in an amount of 0.1-40 kg / ton of dry fiber stock, preferably 0.1-10 kg / ton of dry fiber stock, more preferably 1-4 kg / ton of dry fiber stock, even more preferably 1-4 kg / ton of dry fiber stock. In one embodiment pigment material is introduced to the fiber stock. In one embodiment the pigment material is introduced to the fiber stock at the same time as cationic emulsion polymer and optional AKD. In one embodiment the pigment material, the cationic emulsion polymer and optional AKD are introduced as a mixture to the fiber stock. In one embodiment the pigment material, the cationic emulsion polymer and optional AKD are introduced sequentially to the fiber stock. In one embodiment the pigment material comprises talc, kaolin clay, calcium carbonate, titanium dioxide or a mixture thereof. In one embodiment, sizing agent, fixative, retention aid, drainage aid, wet strength agent, dry strength agent, barrier agent or a mixture thereof is introduced to the fiber stock, preferably before introducing the cationic emulsion polymer and optional AKD to the fiber stock. In one embodiment the sizing chemical comprises alkenyl succinic anhydride (ASA). In one embodiment the retention aid comprises cationic polyacryl amide (CPAM), cationic starch, polyamidoamine-epichlorohydrin (PAE), polyvinyl alcohol (PVA), polyvinylamine (PVAm), poly ethylenimine (PEI) or a mixture thereof. In one embodiment ASA is introduced in an amount of 0.1 -4%, preferably 0.5-1.5% based on dry weight of the fiber stock. In one embodiment the fixative, drainage aid or a mixture thereof comprises aluminium sulphate (ALS), polyaluminium chloride (PAC), poly(diallyldimethylammonium chloride) (PDACMAC), cationic polyacrylamide (CPAM), polyethylenimine (PEI), polyamine (PA), polyvinylalcohol (PVA), polyvinylamine (PVAm), silica sol or a mixture thereof. In one embodiment the dry strength agent comprises cationic starch, polyamidoamineepichlorohydrin (PAE), polyamine, polyvinyl alcohol (PVA) or a mixture thereof. The barrier agent are agents that provide oil, grease, water, vapor, oxygen and / or other gas or liquid barrier properties for the moulded fiber based article. Examples of such agents are per- and polyfluoroalkyl and silicon substances for water, oil and grease barrier and styrene butadiene, ethyl vinyl acetate, ethyl vinyl alcohol and / or polyvinyl acetate for the other barriers respectively. In one embodiment pH of the fiber stock comprising cellulosic fibers is 4-5.5 when the resin is introduced to the fiber stock. In one embodiment pH of the fiber stock comprising cellulosic fibers is 4-8 when a blend comprising the resin and AKD is introduced to the fiber stock. In one embodiment consistency of the fiber stock comprising cellulosic fibers is 0.1 %-10 %, preferably 0.1 %-5 %, more preferably 0.2 %-1.0 %. The moulding, i.e. moulding step or moulding process, can be any suitable method known in the art. In one embodiment the moulding comprises wet forming, wet moulding, vacuum forming, vacuum forming coating, vacuum moulding, extrusion forming, extrusion moulding, compression molding, thermoforming, dry forming, air forming, dry moulding, hot pressing, hot press drying, hot moulding, heat pressing, heat moulding, thermomoulding, foam forming or a combination thereof. In one embodiment the moulding is thermoforming, preferably heat pressing, hot pressing, hot press drying, thermomoulding, compression moulding or a combination thereof. In one embodiment the moulding is a combination of vacuum forming, wet moulding and moulding using both heat and mechanical pressure, such as thermoforming, compression moulding, hot press drying or thermoforming drying. In one embodiment the fiber stock is moulded to a sheet. In one embodiment the fiber stock is formed to a sheet, preferably thermoformed to a sheet. In the context of the present application by term “sheet” is meant an article having smaller thickness than length and width. In the context of the present application by term “two-dimensional, 2D, article” is meant a 2D-article originally been made to planar shape and has a smaller thickness than length and width. The 2D-article can be folded or bended to a three-dimensional, 3D, article. In the context of the present application by term “three-dimensional, 3D, article” is meant an article having three dimensions. In the context of the present application a sheet is not considered to be a three-dimensional, 3D, article. In one embodiment the sheet is formed to a three-dimensional, 3D, article. In one embodiment the fiber stock is moulded to a three-dimensional, 3D, article. In one embodiment the fiber stock with or without foam is vacuum formed, extrusion formed, injection formed, blow formed, wet pressed and / or drained by help of vacuum, unrestrained and / or restrained dried, compacted in one or more directions, polymer impregnated, polymer laminated, polymer coated or a combination thereof, to a two-dimensional, 2D, sheet having thickness of 0.1 mm -10 mm, preferably 0.3 mm - 2 mm. In one embodiment the 2D sheet is further thermoformed (i.e. dry moulded, i.e. dry formed) to a threedimensional, 3D, article having preferably length and width of 5 cm - 50 cm, depth of 2 cm -20 cm and wall thickness of 0.1 mm - 2 mm. In one embodiment the fiber stock is wet moulded and the wet moulded fiber stock is moulded to a three-dimensional, 3D, article. In one embodiment temperature of mould(s) in heat pressing, hot pressing, hot press drying, heat compression, hot compression, thermoforming or thermomoulding is 100 °C - 400 °C, preferably 130 °C-220 °C. In one embodiment mechanical pressure applied on fiber stock or two- or three-dimensional fiber based article in heat pressing, hot pressing, hot press drying, heat compression, hot compression, thermoforming or thermomoulding is 0.1 bar - 1000 bar, preferably 1-250 bar and pressure can alternate during heat pressing, hot pressing, hot press drying, heat compression, hot compression, thermoforming or thermomoulding depending on manufacturing technology, equipment and moulded fiber product application. In one embodiment the moulding is thermoforming, heat pressing, thermomoulding, hot pressing, hot press drying, heat compression moulding, hot compression moulding, wet or dry moulding and / or wet or dry forming to form densifying or a combination thereof, to a three dimensional article. In one embodiment the fiber stock comprising the cationic emulsion polymer and AKD is vacuum forming coated on a vacuum forming coated fiber stock that is substantially free, preferably free of resin and AKD, followed by moulding the fiber stocks. In one embodiment the fiber stock comprising the cationic emulsion polymer and AKD is vacuum forming coated on 2-10 vacuum forming coated fiber stocks stock that are substantially free, preferably free of the cationic emulsion polymer and AKD followed by moulding the fiber stocks. In one embodiment the fiber stock comprising cellulosic fibers comprises natural fibers, synthetic fibers or a mixture thereof. Preferably the fibers are plant origin comprising recycled, chemical and / or mechanical hardwood and softwood pulps, sugar cane (such as bagasse), bamboo, marley, wheat, maize, corn, oats, barley, rice, rye, tomato, sorghum, rape seed, palm oil plants, flax, hemp, ramie, cotton, kenaf, jute, banana, cannabis, peat, moss or a mixture thereof. In a second aspect the present invention provides a moulded fiber based article, wherein the moulded fiber based article comprises cationic emulsion polymer and AKD, or wherein the moulded fiber based article is produced with the method according to the present invention. In one embodiment total amount of the cationic emulsion polymer in the moulded fiber based article is 0.001-4.0 wt.%, preferably 0.01-0.1 wt.%, more preferably 0.015-0.05 wt.%, based on the dry weight of the moulded fiber based article. In one embodiment amount of the AKD in the moulded fiber based article is 0.001-4.0 wt.%, preferably 0.1-1.0 wt.%, more preferably 0.1-0.4 wt.%, based on dry weight of the moulded fiber based article. In one embodiment the moulded fiber based article comprises pigment material. In one embodiment the moulded fiber based article is thermoformed fiber based article, preferably hot pressed, hot pressed dried, heat pressed, heat compression moulded, hot compression moulded fiber based article or thermomoulded fiber based article. In one embodiment amount of the fiber in the moulded fiber based article is 50 wt.%-99 wt.%, preferably 80 wt.%-97 wt.%, more preferably 90 wt.%-97 wt.%, based on dry weight of the moulded fiber based article. In one embodiment amount of the pigment material in the moulded fiber based article is 0.01 wt.%-10 wt.%, preferably 0.5 wt.%-5 wt.%, based on dry weight of the moulded fiber based article. In one embodiment the moulded fiber based article comprises sizing agent, a fixative, retention aid, drainage aid, wet strength agent, dry strength agent, barrier agent or a mixture thereof. In one embodiment amount of the sizing agent, fixative, retention aid, drainage aid, wet strength agent, dry strength agent, barrier agent or a mixture thereof in the moulded fiber based article is 0.01 wt.%-5 wt.%, preferably 0.1 wt.%-2.0 wt.%, based on dry weight of the moulded fiber based article. In one embodiment the moulded fiber based article comprises food packages, food service items, drink packages, goods packages, preferably oven proof trays, microwave safe trays, clamshell boxes, other food boxes, cups, trays, plates, bottles or cup lids. In one embodiment the moulded fiber based article is produced with the method according to the present invention. In a third aspect the present invention provides use of cationic emulsion polymer and AKD for improving dryness and Cobb values such as Cobb 5 min value and / or Cobb 30 min value of a moulded fiber based article. In one embodiment pigment material is used in addition to the cationic emulsion polymer and AKD for improving dryness and Cobb values such as Cobb 5 min value and / or Cobb 30 min value of a moulded fiber based article. In one embodiment sizing agent, fixative, retention aid, drainage aid, wet strength agent, dry strength agent or a mixture thereof is used in addition to the cationic emulsion polymer, AKD and optional pigment material for improving dryness and Cobb values, such as Cobb 5 min value and / or Cobb 30 min value of a moulded fiber based article. EXAMPLES Example 1, according to the present invention The chemicals as shown in Figures 1-4 are introduced to the fiber stock by adding AKD (AKD 1-3) first and then the cationic emulsion polymer (Product 1-4). The features of the Product 1-4 are shown in Table 1. After each introduction of a chemical to the fiber stock the fiber stock is mixed for 1.5 minutes. The AKD products had different wax qualities. Table 1. Product Charge density Student vhcoshy Molecular .....................m..................... ............................ 1 W 1.2 '■ TO 2 2.1 - 3.8 '34 3 20 4.5 ■■ 8.6 -15-12 4 22 2..2 - 3..2 '34 Product 1-3 are crosslinked cationic emulsion polymers. Product 4 is a non-crosslinked cationic emulsion polymer. Preparation of two-dimensional, 2D, article / sheet according to the present invention 2D molded sheets were prepared with Rapid Kothen former and hot press dried at 150200°C between steel plates under vacuum suction and mechanical pressure. Dryness’ of the sheets after vacuum drainage, wet press and hot press were -20-25%, -27-33% and -93-99% respectively. Grammage of the RK sheets was 200-800 g / m2 and density was 0.50.7 g / cm3. Preparation of three-dimensional, 3D, article according to the present invention After introducing the chemicals to the fiber stock according to the Example 1 a 3D shaped forming wire with suction mould is dipped into the fiber stock and fiber stock material is drawn / formed against the 3D wire with 200 - 500 micron openings under up to 900 mBar vacuum. Formed 3D article is lifted up from the fiber stock and vacuum suction assisted drainage with very short and light wet press is continued until dryness of wet moulded 3D article is 33 % on average. Wet moulded 3D article is then transferred on to heated counter mould (130-200 °C) and hot press dried and thermoformed to 0.2 - 1.2 mm thickness and final dryness of 90 - 96%. The 3D article is hot press dried and thermoformed to a wall thickness of 0.2 mm-1.2 mm, such as 0.5 mm- 0.8 mm, length of 5 cm-50 cm, width of 5 cm-50 cm and depth of 2 cm-20 cm. Cobb test Cobb test was performed using the test method based on standard ISO 535. Results show that all tested 4 different cationic emulsion polymers (Product 1-4) can decrease Cobb 30min values with all tested AKD products. Table 2. Cobb 30min results of Figure 1. AKD 1 AKD 2 AKD 3 Product 1 Product 2 Product 3 Product 4 Cobb 30min kg AKD wax / 1 dry kg cat. emulsion polymer / 1 dry [g / m2] 1,60 149 1,60 0,10 98 1,60 97 1,60 0,10 100 1,60 94 1,60 0,10 96 1,60 0,10 100 1,60 108 1,60 0,10 97 1,60 103 1,60 0,10 102 1,60 0,10 99 1,60 0,10 94 1,60 248 1,60 0,10 104 1,60 106 1,60 0,10 101 1,60 0,10 106 1,60 0,10 101 Dryness after wet / cold press Dryness of a sheet after wet / cold press was performed using the test method based on 5 standard ISO 638-1:2022. Results show that all tested 4 different cationic emulsion polymers (Product 1-4) can increase dryness in wet / cold press. 10 Table 3. Dryness results of Figure 2. AKD 1 Product 1 Product 2 Product 3 Product 4 Dryness after wet / cold press kg AKD wax / 1 dry pulp kg cationic emulsion polymer / 1 dry pulp [%] 1,60 30,0 1,60 0,10 30,8 1,60 0,10 31,3 1,60 0,10 30,6 1,60 0,10 30,9 Dryness after hot press Dryness after hot press test was performed using the test method based on standard ISO 5   638-1:2022. Results show that cationic emulsion polymer can increase dryness in hot pressing more than other product type chemically similar cationic polymers when AKD is used. 10 15 Table 4. Dryness after hot press results of Figure 3. AKD Cationic salt dispersion polymer Cationic emulsion polymer Cationic dry polymer Dryness after hot press kg AKD wax / t dry pulp kg polymer / t dry pulp [%] 1,2 95,4 1,2 0,15 95,6 1,2 0,30 95,2 1,2 1,00 96,5 1,2 0,15 97,7 1,2 0,30 96,0 1,2 1,00 98,1 1,2 0,15 94,6 1,2 0,30 93,7 1,2 1,00 93,9 1,2 95,3 1,2 94,6 1,2 92,9 Sheet dryness after forming Sheet dryness after forming test was performed using the test method based on standard 5 standard ISO 638-1:2022. Results show that cationic emulsion polymer can increase dryness in vacuum forming / drainage. Table 5. Dryness after vacuum forming results of Figure 4. AKD Cationic emulsion polymer Dryness after vacuum forming kg AKD wax / 1 dry pulp kg polymer / 1 dry pulp [%] [S.D.] 2,0 22,8 0,1 2,0 0,50 23,6 0,1 The foregoing description has provided by way of non-limiting examples of particular 10 implementations and embodiments a full and informative description of the best mode presently contemplated by the inventors for carrying out the invention. It is however clear to a person skilled in the art that the invention is not restricted to details of the embodiments presented in the foregoing, but that it can be implemented in other embodiments using equivalent means or in different combinations of embodiments without deviating from the characteristics of the invention. Furthermore, some of the features of the afore-disclosed example embodiments may be 5 used to advantage without the corresponding use of other features. As such, the foregoing description shall be considered as merely illustrative of the principles of the present invention, and not in limitation thereof. Hence, the scope of the invention is only restricted by the appended patent claims.

Claims

1. A method for producing a moulded fiber based article, the method comprising providing a fibre stock comprising cellulosic fibers;introducing to the fiber stock cationic emulsion polymer; and moulding the fiber stock.

2. The method according to claim 1, wherein the cationic emulsion polymer has a standard viscosity of 1.5 - 5.6 mPas, preferably 1.7 - 3.3 mPas, more preferably 1.7- 3.0 mPas, even more preferably 1.7 - 2.5 mPas, most preferably 1.7 - 2.0 measured by Brookfield viscometer with LIL adapter at 25 °C on a 0.1 % by weight polymer solution in 1 M NaCI.

3. The method according to claim 1 or 2, wherein a net cationic charge of the cationic emulsion polymer is in the range of 1.1 to 4.5 meq / g (dry), preferably 1.5 to 4.5 meq / g (dry), more preferably 3.5 to 4.5 meq / g (dry), at pH 7.

4. The method according to any of claims 1-3, wherein the cationic emulsion polymer is crosslinked cationic emulsion polymer or non-crosslinked cationic emulsion polymer.

5. The method according to any of claims 1-4, wherein the cationic emulsion polymer is linear cationic emulsion polymer or branched cationic emulsion polymer.

6. The method according to any of claims 1-5, wherein the cationic emulsion polymer is cationic polyacrylamide emulsion polymer.

7. The method according to any of claims 1-3, wherein the cationic emulsion polymer is interpenetrating polymer network polymer.

8. The method according to any of claims 1-7, wherein additionally alkyl ketene dimer (AKD) is introduced to the fiber stock.

9. The method according to any of claims 1-8, wherein the cationic emulsion polymer is introduced to the fiber stock in an amount of 0.01-40 kg / ton of dry fiber stock, preferably 0.05-1.5 kg / ton of dry fiber stock, more preferably 0.1-0.5 kg / ton of dry fiber stock.

10. The method according to any of claims 1 -9, wherein the AKD is introduced to the fiber stock in an amount of 0.01-40 kg / ton of dry fiber stock, preferably 0.1-10 kg / ton of dry fiberstock, more preferably 1-4 kg / ton of dry fiber stock, even more preferably 1-3 kg / ton of dry fiber stock.

11. The method according to any of claims 1-10, wherein the cationic emulsion polymer and AKD are introduced as a mixture, sequentially or simultaneously but separately to the fiber stock.

12. The method according to any of claims 1-11, wherein the fiber stock is formed to a sheet.

13. The method according to claim 12, wherein the sheet is formed to a threedimensional, 3D, article.

14. The method according to any of claims 1-11, wherein the fiber stock is moulded to a three-dimensional, 3D, article.

15. The method according to any of claims 1-14, wherein the fiber stock is wet moulded and the wet moulded fiber stock is moulded to a three-dimensional, 3D, article16. The method according to any of claims 1-15, wherein the moulding comprises wet forming, wet moulding, vacuum forming, vacuum forming coating, vacuum moulding, extrusion forming, dry forming, air forming, extrusion moulding, compression molding, thermoforming, dry moulding, hot pressing, hot press drying, hot moulding, heat pressing, heat moulding, thermomoulding, foam forming or a combination thereof.

17. The method according to any one of claims 1-16, wherein pigment material is introduced to the fiber stock.

18. The method according to any of claims 1-17, wherein a sizing agent, fixative, retention aid, drainage aid, wet strength agent, dry strength agent, barrier agent or a mixture thereof is introduced to the fiber stock.

19. A moulded fiber based article, wherein the moulded fiber based article comprises cationic emulsion polymer, and optionally AKD, orwherein the moulded fiber based article is produced with the method according to any of claims 1-18.

20. The moulded fiber based article according to claim 19, wherein the moulded fiber based article comprises food packages, food service items, drink packages, goods packages, preferably oven proof trays, microwave safe trays, clamshell boxes, other food boxes, cups, trays, plates, bottles or cup lids.5   21. Use of cationic emulsion polymer and AKD for improving dryness and Cobb values ofa moulded fiber based article.

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