TECHNICAL FIELD

The present disclosure generally relates to a method for increasing grease resistance and oil resistance of a fiber based article. The disclosure relates particularly, though not exclusively, to a method for improving grease resistance and oil resistance of 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 fossil-based 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, produced food, microwavable food, or as lids for beverage containers such as hot coffee.

Depending on molded pulp application, oil, grease, water, water vapor, oxygen and/or other gas or liquid barrier properties are needed in different product 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 improving grease and oil resistance of a moulded fiber based article comprising obtaining a fibre stock comprising cellulosic fibers, introducing to the fiber stock a composition comprising

- at least one anionic polymer having molecular weight at least 100 kDa, and

- cationic polymer, wherein the anionic polymer having molecular weight at least 100 kDa and the cationic polymer provide the composition with a charge density in the range of

• 0.1- 1 .5 meq/g, when measured at pH 2.8, and

• -0.1 - -3 meq/g, preferably -0.3 - -2.5 meq/g, more preferably

-0.5 - -2.0 meq/g, when measured as an aqueous solution at pH 7.0, optionally introducing polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof to the fiber stock, 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 a composition comprising

- at least one anionic polymer having molecular weight at least 100 kDa, and

- cationic polymer, wherein the anionic polymer having molecular weight at least 100 kDa and the cationic polymer provide the composition with a charge density in the range of

• 0.1- 1 .5 meq/g, when measured at pH 2.8, and

• -0.1 - -3 meq/g, preferably -0.3 - -2.5 meq/g, more preferably

-0.5 - -2.0 meq/g, when measured as an aqueous solution at pH 7.0, optionally polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof, and optionally pigment material, 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 a composition comprising

- at least one anionic polymer having molecular weight at least 100 kDa, and

- cationic polymer, wherein the anionic polymer having molecular weight at least 100 kDa and the cationic polymer provide the composition with a charge density in the range of

• 0.1- 1 .5 meq/g, when measured at pH 2.8, and

• -0.1 - -3 meq/g, preferably -0.3 - -2.5 meq/g, more preferably

-0.5 - -2.0 meq/g, when measured as an aqueous solution, at pH 7.0, optionally polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof, and in addition optionally pigment material for improving grease and oil resistance a moulded fiber based article.

It has now been surprisingly found that moulded, such as thermoformed, fiber based articles comprising a composition comprising at least one anionic polymer having molecular weight at least 100 kDa and cationic polymer, wherein the composition has a special charge density has increased oil resistance. It was surprisingly found that the composition acts as oil barrier in the fiber based article. It is also believed that the composition acts also as a grease barrier in the fiber based article.

It has been found that the composition increased olive oil resistance, i.e. penetration time of a moulded fiber based article by approximately 60 min compared to a moulded fiber based article without the composition. It is also believed that grease resistance in terms of grease penetration time and/or uptake are increased as well as oil uptake.

It has been also surprisingly found that moulded fiber based articles comprising the composition and polyamidoamine-epichlorohydrin (PAAE), glyoxalated polyacrylamide, starch or a mixture thereof has even better oil resistance. It is also believed that grease resistance is even better.

It has been found that the composition together with polyamidoamine- epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof increased oil resistance, i.e. penetration time and uptake of a moulded, such as thermoformed, fiber based article by approximately 200 min compared to a moulded fiber based article without the composition and the polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide or a mixture thereof. It is also believed that grease resistance is also enhanced.

Without bounding to any theory, it is believed that the moulded fiber products comprising the composition comprising the anionic and cationic components, will trap, i.e. uptake i.e. absorbs and adsorbs grease and oil components and acts as grease and oil barrier. The fiber-based articles of the present invention are at least partly biodegradable and compostable, preferably mostly biodegradable and compostable, more preferably biodegradable and compostable.

It has been also surprisingly found that moulded fiber based articles having oil and/or grease resistance can be produced with a simple and low-cost method. It has been found that moulded fiber based articles having grease and/or oil resistance can be produced by introducing to a fiber stock comprising cellulosic fibers the composition comprising at least one anionic polymer and cationic polymer, wherein the composition has a special charge density and optionally introducing polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof, and moulding, such as thermoforming, the fiber stock.

It has been surprisingly found that by introducing the composition in high amounts (such as 5-50 kg/t based on dry weight of the fiber stock) to a fiber stock the produced moulded articles have high oil resistance. The oil resistance is increased even more when additionally polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof is introduced to the fiber stock. It is believed that grease resistance is also enhanced.

It has been additionally surprisingly found that the moulded, such as thermoformed, fiber based articles have improved tensile bending stiffness compared to moulded fiber based articles not comprising the composition or the composition and polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof. The improved tensile bending stiffness enables reducing mass per square of the moulded fiber based article since thickness of the moulded fiber based article can be reduced.

As the thickness and mass per square can be reduced the weight of the moulded fiber based article can be reduced, and therefore reduction in the cost of fibrous raw material.

It is also believed that addition of the composition or the composition and polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof to a fiber stock of a process for manufacturing board will provide grease and oil resistance for the board.

It has been also found that addition of pigments and/or other additives to the composition before its addition to the fiber stock improves gloss, smoothness, coatability and/or barrier properties of the moulded fiber based article.

The appended claims define the scope of protection.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows olive oil resistance at 40 °C for 500 and 400 g/m ² hot press dried 2D molded fiber article with different fiber stock chemistries.

Figure 2 shows dry tensile properties of 500 g/m ² hot press dried 2D molded fiber article with different fiber stock chemistries.

Figure 3 shows high moisture tensile properties of 500 g/m ² hot press dried 2D molded fiber article with different fiber stock chemistries.

Figure 4 shows olive oil resistance at 40 °C for 400 g/m ² hot press dried 2D molded fiber article with different fiber stock chemistries.

Figure 5 shows dry tensile properties of 400 g/m ² hot press dried 2D molded fiber article with different fiber stock chemistries.

Figure 6 shows vacuum formed fiber based two-dimensional articles/sheets.

Figure 7 shows molded fiber based three-dimensional article.

DETAILED DESCRIPTION

In a first aspect the present invention provides a method for improving grease and oil resistance of a moulded fiber based article comprising obtaining a fibre stock comprising cellulosic fibers, introducing to the fiber stock a composition comprising

- at least one anionic polymer having molecular weight at least 100 kDa, and

- cationic polymer, wherein the anionic polymer having molecular weight at least 100 kDa and the cationic polymer provide the composition with a charge density in the range of

• 0.1- 1 .5 meq/g, when measured at pH 2.8, and

• -0.1 - -3 meq/g, preferably -0.3 - -2.5 meq/g, more preferably

-0.5 - -2.0 meq/g, when measured as an aqueous solution at pH 7.0, optionally introducing polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof to the fiber stock, and moulding the fiber stock.

The anionic polymer and the cationic polymer of the composition provide the charge densities to the composition.

In one embodiment polyamidoamine-epichlorohydrin (PAAE), glyoxalated polyacrylamide, starch or a mixture thereof is introduced to the fiber stock, preferably polyamidoamine-epichlorohydrin is introduced to the 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 before addition of the composition. In one embodiment the pigment material is introduced to the fiber stock after addition of the composition. In one embodiment the pigment material is introduced to the fiber stock at the same time as the composition. In one embodiment the pigment material and the composition are introduced as a mixture to the fiber stock.

In one embodiment the pigment material comprises talc, kaolin clay calcium carbonate or a mixture thereof. 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 moulding, extrusion forming, extrusion moulding, thermoforming, dry forming, dry moulding, hot pressing, hot press drying, hot moulding, heat pressing, heat forming, heat moulding, thermomoulding or a combination thereof, preferably thermoforming, more preferably heat pressing, hot pressing, hot press drying or thermomoulding.

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.

The fiber stock can be thermoformed to a sheet by any suitable method known in the art. An example of a suitable method is heat pressing in which elevated mechanical pressure and elevated temperature is applied to two metal plates having fiber stock there between.

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, bended, formed or moulded 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 or moulded 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 is formed 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 three- dimensional, 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 with or without foam is vacuum formed, extrusion 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 three-dimensional, 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 the fiber stock is vacuum formed i.e. wet moulded to a three- dimensional, 3D, article having preferably length and width of 5 cm - 50 cm and depth of 2 cm - 20 cm and then thermoformed and dried, preferably to wall thickness of 0.1 mm - 3 mm, preferably 0.3 mm - 1 .0 mm.

In one embodiment temperature of mould(s) in heat pressing, hot pressing, hot press drying, thermoforming or thermomoulding is 100 °C - 400 °C, preferably 130 °C - 200 °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, thermoforming or thermomoulding is 0.1 bar - 1000 bar, preferably up to 20 bar and pressure can alternate during heat pressing, hot pressing, hot press drying, thermoforming or thermomoulding depending on manufacturing technology, equipment and moulded fiber product application.

In one embodiment the moulding is thermoforming, heat pressing, thermomoulding, wet or dry moulding and/or wet or dry forming, densifying or a combination thereof, to a three dimensional article.

In one embodiment the polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof and the composition are introduced sequentially to the fiber stock, preferably the polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof is introduced to the fiber stock before introducing the composition to the fiber stock.

In one embodiment the composition is introduced to the fiber stock followed by introducing the polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof to the fiber stock.

In one embodiment the at least one anionic polymer and the cationic polymer are introduced sequentially to the fiber stock, preferably the at least one cationic polymer is introduced to the fiber stock before introducing the anionic polymer to the fiber stock.

In one embodiment the anionic polymer is introduced to the fiber stock followed by introducing the at least one cationic polymer.

In one embodiment the at least one anionic polymer, the cationic polymer and the polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof are introduced sequentially to the fiber stock.

In one embodiment the at least one anionic polymer and the cationic polymer are introduced sequentially to the fiber stock followed by introducing the polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof to the fiber stock. In one embodiment the polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof is introduced to the fiber stock followed by introducing the at least one anionic polymer and the cationic polymer sequentially to the fiber stock.

In one embodiment the at least one anionic polymer is introduced to the fiber stock followed by introducing the polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof to the fiber stock followed by introducing the cationic polymer to the fiber stock.

In one embodiment the cationic polymer is introduced to the fiber stock followed by introducing the polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof to the fiber stock followed by introducing the at least one anionic polymer to the fiber stock.

The composition comprises a mixture of anionic polymer and cationic polymer. The anionic polymer and cationic polymer may be mixed with each other before the addition of the composition as an aqueous solution to the fibre stock, i.e. before the addition as a single solution. The mixing may be performed in any suitable way of combining the anionic polymer and cationic polymer. For example, it is possible to mix the anionic polymer and the cationic polymer in dry form or as aqueous solutions, or the anionic polymer or the cationic polymer in dry form may be dissolved to an aqueous solution of the other component.

In one embodiment the composition is in form of an aqueous solution, and it is introduced to the fibre stock as an aqueous mixture. The term “aqueous solution” encompasses here not only true solutions but also aqueous dispersions. Preferably, the composition in form of an aqueous solution contains at most minor amounts of incompletely dissolved residue, or is completely free of solid matter and/or incompletely dissolved residues.

Alternatively, the composition may be in form of a dry particulate material. This reduces the risk of degradation of the composition during transportation and storage, and thus improves the shelf life. Especially cationic starch as the cationic polymer may be vulnerable to microbiological degradation, which could lead to loss of performance. The composition may preferably be a mixture of solid particulate anionic polymer and solid particulate cationic polymer. Such mixture in particulate form is easy and economically advantageous to store and transport. The composition in form of a dry particulate material may have a moisture content of at most 25 weight-%. The particle size of the dry particulate material may vary for example between 5 and 2000 microns.

When the composition is in form of dry particulate material, it can be dissolved into water in order to obtain an aqueous composition, for example, by using effective high-shear dissolution, such as rotor-stator mixer, and optional application of heat, or by using jet-cooker. The dissolving may be done e.g. at the site of application. According to one preferred embodiment the composition in form of a dry particulate material is dissolved into water, preferably by using a high-shear dissolution, in order to obtain an aqueous composition. The obtained aqueous composition may then be optionally diluted and then introduced, after the optional dilution, to the fibre stock.

In one embodiment an amphoteric polymer having both anionic and cationic groups providing the charge density in the range of

0.1-1 .5 meq/g, when measured at pH 2.8, and

-0.1 - -3 meq/g, preferably -0.3 - -2.5meq/g, more preferably -0.5 - -2.0 meq/g, when measured at pH 7.0 is introduced to the fiber stock, preferably instead of the composition.

In one embodiment an IPN (interpenetrating polymer network) material having both anionic and cationic groups providing the charge density in the range of

0.1-1 .5 meq/g, when measured at pH 2.8, and

-0.1 - -3 meq/g, preferably -0.3 - -2.5meq/g, more preferably -0.5 - -2.0 meq/g, when measured at pH 7.0 is introduced to the fiber stock, preferably instead of the composition. In one embodiment a polymer having both anionic and cationic groups, preferably amphoteric polymer and/or an interpenetrating polymer network material providing the charge densities is/are introduced to the fiber stock, preferably instead of the composition.

In one embodiment the composition is introduced in an amount of 5-50 kg/t, preferably 10-40 kg/t, more preferably 20-30 kg/t, based on dry weight of the fiber stock.

In one embodiment the polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide or a mixture thereof is introduced in an amount of 1 kg/t - 8 kg/t, preferably 2 kg/t - 6 kg/t, more preferably 2 kg/t - 4 kg/t as dry weight, based on the dry weight of the fiber stock.

In one embodiment the starch comprises native starch, cooked starch, uncooked starch, cationic starch, native chemically modified starch, physically modified polymer grafted starch, enzyme modified starch, anionic starch, amphoteric starch, crosslinked starch, pre-gelled starch, swelled starch, granule starch or a mixture thereof.

In one embodiment the starch is introduced in an amount of 1 kg/t - 100 kg/t as dry weight, based on the dry weight of the fiber stock.

In one embodiment cationic starch is introduced in an amount of 1 kg/t - 20 kg/t as dry weight, based on the dry weight of the fiber stock.

In one embodiment non-ionic starch is introduced in an amount of 1 kg/t - 100 kg/t as dry weight, based on the dry weight of the fiber stock.

In one embodiment before introducing the composition and the polyamidoamine- epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof to the fiber stock pH of the fiber stock is adjusted to pH value 5-9, preferably 7-8. In one embodiment conductivity of the fiber stock is adjusted to 0.05 mS/cm - 6mS/cm, preferably 0.1 mS/cm - 1 mS/cm before introducing the composition and the polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof to the fiber stock. In one embodiment the conductivity is adjusted with a composition comprising 70% calcium acetate, 20% sodium sulphate and 10% sodium bicarbonate.

In one embodiment sizing chemical, fixative, wet strength agent, drainage aid or a mixture thereof is introduced to the fiber stock after or before introducing the composition and polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof to the fiber stock

In one embodiment sizing chemical, fixative, wet strength agent, drainage aid or a mixture thereof is introduced to the fiber stock before introducing the composition and polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof to the fiber stock.

In one embodiment sizing chemical, fixative, wet strength agent, drainage aid or a mixture thereof is introduced to the fiber stock after introducing the composition and polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof to the fiber stock.

In one embodiment polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof is introduced to the fiber stock before introducing a sizing chemical to the fiber stock.

In one embodiment a sizing chemical and polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof is introduced to the fiber stock at the same time but separately.

In one embodiment a sizing chemical and polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide or a mixture thereof is introduced to the fiber stock as a mixture. In one embodiment the sizing chemical comprises alkyl ketene dimer (AKD), alkenyl succinic anhydride (ASA), rosin or a mixture thereof.

In one embodiment AKD, ASA, rosin or a mixture thereof and polyamidoamineepichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof are introduced as a mixture to the fiber stock, preferably before introducing the composition to the fiber stock.

In one embodiment AKD, ASA, rosin or a mixture thereof and polyamidoamineepichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof are introduced as a mixture to the fiber stock, preferably after introducing the composition to the fiber stock.

In one embodiment AKD, ASA, rosin, polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof are introduced as a mixture to the fiber stock, preferably before introducing the composition to the fiber stock.

In one embodiment AKD, ASA, rosin, polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof are introduced as a mixture to the fiber stock, preferably after introducing the composition to the fiber stock.

In one embodiment AKD, ASA, rosin or a mixture thereof 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 polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide or a mixture thereof is introduced in an amount of 1 -8 kg/t, preferably 2-4 kg/t as dry weight, 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) or a mixture thereof. In one embodiment the wet strength agent comprises polyamide-epichlorohydrin (PAE), glyoxalated polyacrylamide (GPAM), starch or a mixture thereof. In one embodiment the wet strength agent is added after addition of a sizing agent but before addition of the composition to the fiber stock.

In one embodiment consistency of the obtained fiber stock comprising cellulosic fibers is 0.1 %-10 %, preferably, preferably 0.2-1 .0, more preferably 0.2 %-0.5 %.

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 one embodiment the anionic polymer has molecular weight of at least 100 kDa, preferably at least 300, more preferably from 100 kDa to 10000 kDa, even more preferably from 100 kDa to 700 kDa, even more preferably 100 kDa to 600 kDa.

In one embodiment the anionic polymer comprises carboxymethyl cellulose, microfibrillated cellulose, microfibrillated lignocellulose, anionic starch, chitosan, pectin, fatty acid esters, other anionic and or anionically derivatized polysaccharides or a mixture thereof, preferably anionic starch, carboxymethyl cellulose, microfibrillated cellulose, microfibrillated lignocellulose or a mixture thereof.

In one embodiment the cationic polymer comprises starch derivate such as hydroxypropylated starch, nanocellulose, microfibrillated cellulose, lignocellulose based derivatives, chitosan, alfaglucan, polyhydroxy alkanoate, polylactic acid, cationic starch or a mixture thereof, preferably cationic starch, chitosan, nanocellulose, microfibrillated cellulose, lignocellulose based derivatives or a mixture thereof. Polysaccharides, as known, are natural polymers formed from polymeric carbohydrate molecules, which comprise long chains of monosaccharide units as repeating units bound together by covalent bonds. Polysaccharides may be extracted from various botanical sources, microorganisms, etc. Polysaccharide chains contain multiple hydroxyl groups capable of hydrogen bonding.

In the present context the term "anionically derivatized" is understood to refer not only to chemical modification of a polysaccharide by reactions which result in covalently bonded anionic groups in the polysaccharide structure, but also to any sufficient association of anionic groups with the polysaccharide structure, which provide the desired properties, such as charge density, for the composition. Such sufficient association of anionic groups may be achieved, for example, by adsorption or by other processing of the polysaccharide starting material, such as mechanical processing. It is possible to obtain anionically derivatized polysaccharide by combination of other processing, such as mechanical processing, and chemical modification. Chemical modification of the polysaccharide is preferred for providing anionically derivatized polysaccharide suitable for use in the present invention. Anionic groups may be provided e.g. by incorporating to the polysaccharide structure carboxyl, sulphate, sulphonate, phosphonate or phosphate groups, including their salt forms, or combinations thereof. Anionic groups may be introduced to the polysaccharide structure by suitable chemical modification including carboxymethylation, oxidation, sulphation, sulphonation and phosphorylation.

In one embodiment the anionically derivatized polysaccharide which is suitable for use in the present invention may have a charge density value in the range of -0.05 - -5.0 meq/g, such as -0.3 - -5.0 meq/g or -0.5 - -5.0 meq/g, preferably -0.7 - -4.5 meq/g, more preferably -1.0 - -4.0 meq/g, measured at pH 7. Measured charge density values are calculated per weight as dry.

Anionically derivatized polysaccharide may comprise water-soluble and/or water- dispersible anionically derivatized polysaccharide(s). In the present context aqueous solution of anionically derivatized polysaccharide covers not only true solutions but also aqueous dispersions of anionically derivatized polysaccharide(s). Preferably the anionically derivatized polysaccharides are water-soluble, meaning that they contain at most 30 weight-%, preferably at most 20 weight-%, more preferably at most 15 weight-%, even more preferably at most 10 weight-%, of water-insoluble material. The water-solubility may improve the availability of the functional groups of the polysaccharide, thereby improving the interaction with the cationic polymer, such as cationic starch of the composition, as well as the other constituents present in the fibre stock.

In one embodiment the anionically derivatized polysaccharide comprises anionically derivatized celluloses, anionically derivatized starches, or any combinations thereof, including modified celluloses and starches, such as hydroxyethyl cellulose, hydroxyethyl starch, ethyl hydroxyethyl cellulose, ethyl hydroxyethyl starch, hydroxypropyl cellulose, hydroxypropyl starch, hydroxypropyl hydroxyethyl cellulose, hydroxypropyl hydroxyethyl starch, methyl cellulose, methyl starch, and the like.

In one embodiment the anionically derivatized polysaccharide comprises cellulose, preferably carboxymethylated cellulose, even more preferably carboxymethyl cellulose. Anionically derivatized polysaccharide may comprise, for example, purified carboxymethyl cellulose or technical grade carboxymethyl cellulose. The carboxymethyl cellulose may be manufactured by any process known in the art. It is believed that when the composition comprises anionically derivatized polysaccharide, which comprises cellulose, the backbone structure of the polysaccharide is similar than the cellulosic fibres in the pulp, i.e. the structure showing 1 ,4-beta glycosidic linkages in the backbone. This matching configuration may provide stronger interaction between the composition and the fibres.

In one embodiment the anionically derivatized polysaccharide comprises carboxymethylated cellulose, preferably carboxymethyl cellulose, which may have a degree of carboxymethyl substitution > 0.2, preferably in the range of 0.3 - 1 .2, more preferably 0.4 - 1 .0 or 0.5 - 1 .0, providing further enhanced water-solubility. In one preferable embodiment the carboxymethylated cellulose may have a degree of carboxymethyl substitution in the range of 0.5 - 0.9, which provides essentially complete water-solubility for the carboxymethyl cellulose.

In one embodiment of the anionically derivatized polysaccharide comprises carboxymethylated cellulose, preferably carboxymethyl cellulose, which may have a charge density value < -1 .1 meq/g, preferably in the range of -1 .6 - -4.7 meq/g, more preferably -2.1 - -4.1 meq/g, even more preferably -2.5 - -3.8 meq/g, when measured at pH 7. All measured charge density values are calculated per weight as dry.

In one embodiment the anionically derivatized polysaccharide comprises carboxymethylated cellulose, preferably carboxymethyl cellulose, which may have viscosity in the range of 100 - 30 000 mPas, preferably 200 - 20 000 mPas, more preferably 500 - 10 000 mPas, measured from 2 weight-% aqueous solution at 25 °C, by using Brookfield LV DV1 .

In one embodiment the anionically derivatized polysaccharide comprises carboxymethylated cellulose, preferably carboxymethyl cellulose.

In one embodiment the anionically derivatized polysaccharide may be at least partly in microfibrillar form. Preferably the anionically derivatized polysaccharide comprises anionic microfibrillar cellulose. Microfibrillar cellulose is sometimes referred to as nanocellulose, but as used herein, by microfibrillar cellulose or nanocellulose it is not meant crystalline cellulose derivatives known e.g. as microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC), or cellulose nanowhiskers. Crystalline cellulose derivatives are thus excluded from anionic microfibrillar cellulose. Microfibrils may have an average diameter of 2 - 60 nm, preferably 4 - 50 nm, more preferably 5 - 40 nm, and an average length of several micrometers, preferably less than 500 pm, more preferably less than 300 pm, more preferably 2 - 200 pm, even more preferably 10 - 100 pm, most preferably 10 - 60 pm. Microfibrillated cellulose comprises often bundles of 10 - 50 microfibrils.

In one embodiment the anionically derivatized polysaccharide is free from microfibrillar cellulose. In one embodiment the composition comprises cationic starch, which of natural origin and has an amylopectin content at least 80 weight-%. Amylopectin is a branched starch molecule, where branching typically occurs with a(1 ^6) bonds about at every 15 - 30 anhydroglucose units of the starch backbone, which contains a(1 ^4) bonds. Amylopectin content of the cationic starch ensures that that the size of the polyion complex to be formed has appropriate dimensions, required for good oil and grease resistance.

In one embodiment the cationic starch of the composition may have an amylopectin content > 85 weight-%, preferably > 90 weight-%, more preferably > 95 weight-%. Cationic starch of the composition may originate from potato, waxy potato, rice, waxy corn, sweet potato, arrowroot or tapioca starch, or any combination thereof. Preferably the cationic starch originates from waxy corn starch and/or waxy potato starch.

The cationic starch may comprise starch units, i.e. starch molecules, of which at least 70 weight-%, preferably at least 80 weight-%, more preferably at least 85 weight-%, even more preferably at least 90 weight-%, sometimes even more preferably at least 95 weight-%, have an average molecular weight MW over 20 000 000 g/mol, preferably over 50 000 000 g/mol, more preferably over 100 000 000 g/mol, sometimes even over 200 000 000 g/mol, such as 200 000 000 g/mol - 500 000 000 g/mol.

In one embodiment the composition comprises cationic starch, which comprises cationic non-degraded starch. The cationic non-degraded starch provides an optimal interaction with the anionically derivatized polysaccharide as well as with other constituents of the fibre stock, e.g. fibres and/or inorganic fillers. In the present context, the term “non-degraded starch” denotes starch which is essentially untreated by oxidative, thermal, enzymatical and/or acid treatment in a manner that would cause hydrolysis of glycosidic bonds or degradation of starch molecules or units. In case the starch is solubilized by cooking, the temperature during cooking is less than 140 °C, preferably less than 120 °C, often less than 110 °C or 105 °C. For example, after solubilization the non-degraded cationic starch has a viscosity at least of 20% preferably at least 50% of a viscosity of a corresponding native starch, solubilized by cooking at 97 °C for 30 min. The viscosity measurement is made by Brookfield LV-DVI viscometer, at 2 % solids content and at room temperature.

Cationic starch suitable for use in the composition may be obtained by cationizing starch by any suitable method. Preferably cationic starch is obtained by using 3- chloro-2-hydroxypropyltrimethylammonium chloride or 2,3- epoxypropyltrimethylammonium chloride. It is also possible to cationize starch by using cationic acrylamide derivatives, such as (3-acrylamidopropyl)- trimethylammonium chloride. Various methods for cationization of starch are known for a person skilled in the art.

In one embodiment the cationic starch has been obtained by using cationization as the sole chemical derivatization of starch, and the cationic starch is thus non-cross- linked, non-grafted, or it has not been otherwise chemically modified.

The cationic starch of the composition may have a substitution degree of 0.025 - 0.3, preferably 0.03 - 0.16, more preferably 0.045 - 0.1 . The substitution degree is relative to the cationicity of the starch, the higher substitution degree indicating a higher cationicity. Cationic starches having relatively high substitution degree, and cationicity, are preferred for use in the composition as they may provide additional benefits.

In one preferable embodiment the composition is free of cationic synthetic polymers.

In one embodiment the composition, the cationic starch and/or the anionically derivatized polysaccharide may comprise further auxiliaries or additives, such as preservatives, biocides, stabilizers, antioxidants, pH adjusting agents or the like.

In one embodiment the composition comprises anionically derivatized polysaccharide and cationic starch in weight ratio (dry/dry) 10:90 - 90:10, preferably 30:70 - 70:30. The weight ratio is given as dry weights. Preferably the weight ratio of the anionically derivatized polysaccharide to the cationic starch is chosen so that the composition is net anionic at the pH of the fibre stock.

In a second aspect the present invention provides a moulded fiber based article, wherein the moulded fiber based article comprises a composition comprising

- at least one anionic polymer having molecular weight at least 100 kDa, and

- cationic polymer, wherein the anionic polymer having molecular weight at least 100 kDa and the cationic polymer provide the composition with a charge density in the range of

• 0.1- 1 .5 meq/g, when measured at pH 2.8, and

• -0.1 - -3 meq/g, preferably -0.3 - -2.5 meq/g, more preferably

-0.5 - -2.0 meq/g, when measured as an aqueous solution at pH 7.0, optionally polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof, and optionally pigment material, or wherein the moulded fiber based article is produced with the method according to the present invention.

In one embodiment the moulded fiber based article comprises polyamidoamine- epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof.

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 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 70 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 composition in the moulded fiber based article is 0.5 wt.%-10 wt.%, preferably 1 wt.%-3 wt.%, based on the dry weight of the moulded fiber based article.

In one embodiment amount of the polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof in the moulded fiber based article is 0.05 wt.%-0.8 wt.%, preferably 0.2 wt.%-0.4 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.%-5 wt.%, preferably 0.5 wt.%-4 wt.%, based on dry weight of the moulded fiber based article.

In one embodiment the moulded fiber based article comprises a sizing chemical, fixative, wet strength agent, drainage aid or a mixture thereof. In one embodiment amount of the sizing chemical, fixative or a mixture thereof in the moulded fiber based article is 0.1 wt.%-5 wt.%, preferably 0.5 wt.%-2.5 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, drink service items, goods packages or goods service items, preferably food service and packaging items such as ovenable trays, microwavable trays, clamshell boxes, other food boxes, soup cups, fresh meat and poultry trays, plates or cup lids.

In one embodiment the moulded fiber based article is produced with the method of the present invention.

In a third aspect the present invention provides a use of a composition comprising

- at least one anionic polymer having molecular weight at least 100 kDa, and

- cationic polymer, wherein the anionic polymer having molecular weight at least 100 kDa and the cationic polymer provide the composition with a charge density in the range of 0.1- 1 .5 meq/g, when measured at pH 2.8, and

• -0.1 - -3 meq/g, preferably -0.3 - -2.5 meq/g, more preferably

-0.5 - -2.0 meq/g, when measured as an aqueous solution, at pH 7.0, and in addition optionally polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof, and optionally pigment material for improving grease and oil resistance a moulded fiber based article.

In one embodiment the composition is used for improving grease resistance. In one embodiment the composition is used for improving oil resistance. In one embodiment the composition is used for improving oil and grease resistance.

In one embodiment the polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof is used in addition to the composition for improving oil resistance of a thermoformed fiber based article.

In one embodiment the pigment material is used in addition to the polyamidoamine- epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof and the composition for improving grease and oil resistance of a thermoformed fiber based article.

In one embodiment a sizing chemical, fixative or a mixture thereof is used in addition to the polyamidoamine-epichlorohydrin, glyoxalated polyacrylamide, starch or a mixture thereof, the composition and the pigment material for improving grease and oil resistance of a thermoformed fiber based article. EXAMPLES

Example 1 according to the present invention

AKD, 0.1 - 0.3 % (by dry weight) is first added to fiber stock with 0-3 - 0.5 % consistency made from 100% birch kraft pale pulp and fiber stock. Then 0.2 - 0.4 % (by dry weight) of polyamide-epichlorohydrin (PAE) is added to fiber stock. Then 0.2 - 0.4 % (by dry weight) PDACMAC + CPAM is added to the fiber stock. Then 1 - 3 % (by dry weight) of the composition comprising at least one anionic polymer having molecular weight at least 300 - 500 kDa and cationic polymer and optionally PAAE is added to the fiber stock. After addition of each chemical to the fiber stock the stock is mixed for at least 1 minute under turbulent conditions before addition of next chemical.

Example 2, comparative example(s)

Same method and chemicals were used to prepare and determine characteristics of a 2D molded fiber article/sheet as in Example 1 but now PAAE and cationic starch were tested as alone and together by adding PAAE first and then cationic starch to fiber stock. The composition comprising at least one anionic polymer having molecular weight 300-500 kDa and cationic polymer and PAAE were tested as in Example 1 . PAAE was also tested with the anionic polymer of the composition by adding PAAE first and then the anionic polymer to fiber stock.

Preparation of two-dimensional, 2D, article/sheet

After introducing the chemicals according to example 1 and 2 to the fiber stock the fiber stock is vacuum formed to dryness of 20 - 30 % using dynamic drainage analyzer under 200 - 650 mBar vacuum against planar round shaped 10 cm in diameter, forming wire with 200 - 400 micron openings. Wet 2D article/sheet with grammage of 200 - 800 g/m2 as dry is hot press dried and thermoformed to 0.2 - 1.2 mm thickness between 130-200 °C metal plates until dryness of 94 - 99% is reached. Hot press dried and thermoformed 2D moulded fiber articles/sheets are shown in Figure 6. The 2D fiber moulded article may be hot pressed and/or thermoformed to a density of 0.5 g/cm ³ -1 .5 g/cm ³ , preferably 1 .0 - 1 .2 g/cm ³ and thickness of 0.1 - 1 .2 mm, preferably 0.3 - 0.8 mm.

Preparation of three-dimensional, 3D, article

After introducing the chemicals to the fiber stock 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 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%. Dried 3D moulded fiber article is shown in Figure 7.

The 3D article may be 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.

Oil and grease resistance test

Oil and grease testing was performed using the test method based on standard ASTM F119-82:2015. Grease testing was performed using the test method based on standard TAPPI T559: 2012.

As can be seen from Figures 1 and 4 the thermoformed article (2D article/sheet) of the present invention exhibits increased oil resistance compared to the zero test (only fiber stock comprising cellulosic fibers, no chemicals added) and to the comparative thermoformed articles. As can be seen from Figures 2 and 5 the thermoformed article (2D article/sheet) of the present invention exhibits increased dry tensile properties. As can be seen from Figure 3 the thermoformed article (2D article/sheet) of the present invention exhibits increased high moisture tensile properties. Various embodiments have been presented. It should be appreciated that in this document, words comprise, include, and contain are each used as open-ended expressions with no intended exclusivity.

The foregoing description has provided by way of non-limiting examples of particular 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 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.