A method and a moulded multi-layered fibrous product

Abstract

According to an example aspect of the present invention, there is provided a method comprising: providing a first fibrous composition and a second fibrous composition and one or more further fibrous compositions, each comprising independently from each other cellulosic fibres and water, wherein at least one of the further fibrous compositions further comprises starch or a starch derivative; in a mould, forming and dewatering the first fibrous composition, the second fibrous composition and the one or more further fibrous compositions to obtain a first fibrous layer, a second fibrous layer and, between them, one or more inner fibrous layers, respectively, in a stacked configuration, whereby at least one of the inner fibrous layers comprises starch or a starch derivative; and hot pressing the stack comprising the first fibrous layer, the second fibrous layer and, between them, the one or more inner fibrous layers, to obtain a moulded multi-layered fibrous product.

Description

A method and a moulded multi-layered fibrous productFIELD

[0001] The present application relates to moulded multi-layered fibrous products.BACKGROUND

[0002] In the manufacturing of moulded fibre products, good retention is needed for high and efficient production with low defects and to avoid overdosing the chemicals. With stable and optimized retention control it is possible to achieve more efficient production while saving costs. Too high levels and variating amounts of fines, fillers, and chemicals in the white water system is a risk which can cause accumulation of deposits and create breaks, a dirty system, unstable quality and runnability issues.

[0003] In foam forming methods, retention of wet-end chemicals or additives has been particularly difficult due to the charge environment and the interference caused by surfactants that are typically used to produce the foam. The vacuum-assisted water removal during the forming also challenges the efficient retention of chemicals.

[0004] Starch is a commonly used additive in the manufacturing of fibrous products. However, there are certain limitations to its use. When adding large amounts of cationic starch to a papermaking furnish, in order to achieve a high paper strength, two major problems arise. The first is that the cationic starch molecules tend to saturate the anionic charge on the cellulose fibres, thus setting a limit to the amount of cationic starch which can be added to the slurry. If an excess of cationic starch is added, only a portion of the starch added will be retained in the sheet, and the rest will circulate in the paper or board machine white water system. A second problem is that fibres which are made cationic by excessive cationic starch addition will not be able to adsorb other cationic additives which may be desired to be added to the pulp slurry, such as sizing agents and retention aids. Furthermore, high amounts of starch often cause problems with runnability, microbiology and foaming during the production process.

[0005] Generally, in both wet forming method and foam forming methods, use of contact drying, such as hot pressing, may impose limitations to the use of additives, such asretention aids, since exposure to hot pressing plates may affect the chemical structure of the retention aid and / or lead to contamination of the pressing plates.

[0006] It is an aim of the present invention to solve at least some of the above discussed problems and to provide an improved method for manufacturing moulded fibre products.SUMMARY OF THE INVENTION

[0007] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0008] According to a first aspect of the present invention, there is provided a method comprising: providing a first fibrous composition and a second fibrous composition and one or more further fibrous compositions, each comprising independently from each other cellulosic fibres and water, wherein at least one of the further fibrous compositions further comprises starch or a starch derivative; in a mould, forming and dewatering the first fibrous composition, the second fibrous composition and the one or more further fibrous compositions to obtain a first fibrous layer, a second fibrous layer and, between them, one or more inner fibrous layers, respectively, in a stacked configuration, whereby at least one of the inner fibrous layers comprises starch or a starch derivative; and hot pressing the stack comprising the first fibrous layer, the second fibrous layer and, between them, the one or more inner fibrous layers, to obtain a moulded multi-layered fibrous product.

[0009] According to a second aspect of the present invention, there is provided a moulded multi-layered fibrous product obtained by the method according to the first aspect.

[0010] According to a third aspect of the present invention, there is provided a moulded multi-layered fibrous product comprising: a first fibrous layer; a second fibrous layer; and at least one fibrous inner layer between the first and the second fibrous layers, wherein each fibrous layer comprises, independently from each other, a cellulosic fibrous material; and wherein at least one of the fibrous inner layers further comprises starch or a starch derivative, wherein the moulded multi-layered fibrous product has been obtained by a method in which a moulded stack comprising said fibrous layers is hot pressed between two shaped pressing plates of which at least one is in a temperature of 150 to 270 °C.

[0011] According to a fourth aspect of the present invention, there is provided use of the moulded multi-layered fibrous product according to the second or the third aspect as a food or liquid packaging or a food or liquid serving product or as a part thereof, or in packaging, serving, storing, cooking and / or heating of food or liquid.

[0012] Various embodiments of the first aspect or the second aspect or the third aspect or the fourth aspect may comprise one or more features from the following bulleted list:• Said at least one of the further fibrous compositions comprises at least 1 wt-%, such as at least 2 wt-%, for example 3 to 10 wt-% of starch or a starch derivative, calculated from the total dry weight of fibres.• All inner fibrous layers comprise starch or a starch derivative.• The first fibrous composition and / or the second fibrous composition are substantially free from starch and starch derivatives.• During the hot pressing, heat is applied from both sides of the stack.• During the hot pressing, heat is applied only from one side of the stack, or one side of the stack is exposed to a higher temperature than the other side.• The outermost fibrous layer on said one side of the stack is substantially free from starch and starch derivatives.• The hot pressing comprises pressing the stack between two shaped pressing plates, of which at least one, preferably both, has a temperature of at least 150 °C, such as 150 to 270 °C, such as 180 to 250 °C, such as 190 to 225 °C.• The first fibrous composition and the second fibrous composition are substantially free from starch and starch derivatives; and the hot pressing comprises pressing the stack between two shaped pressing plates, of which at least one, preferably both, has a temperature of at least 150 °C.As a result of said hot pressing, the starch or the starch derivative becomes gelatinized.The starch or the starch derivative comprises or consists of ungelatinized starch or uncooked starch or non-solubilised starch.• The starch or the starch derivative has not been gelatinized before the hot pressing.• The starch or the starch derivative becomes gelatinized during the hot pressing.• The starch or the starch derivative comprises starch originating from one or more of the following: com, potato, maize, wheat, tapioca, barley, quinoa, pea, rice.• The starch has a high amylose content, such as at least 10 wt-%, such as at least 15 wt-%, such as at least 20 wt-%, such as at least 25 wt-%, such as at least 28 wt-%, such as at least 30%, or 15 to 35 wt-%, calculated from dry matter.• The starch has a degree of substitution (DS), defined as the number of substituents per glucopyranosyl unit, of at least 0.005, such as in the range of 0.005 to 1, such as 0.01 to 0.5, such as 0.02 to 0.2.• The starch or the starch derivative comprises unmodified starch or modified starch, such as oxidized starch, hydroxyethylated starch, cationic starch, anionic starch, grafted starch, hydrophobic starch, aldehyde starch, mechanically-modified starch, thermally modified starch, or any combination thereof.• The starch derivative comprises a chemically modified starch or a decomposition product of starch, such as dextrin, such as thermally modified dextrin.• The average particle size of the starch is 1 to 50 pm, such as 5 to 25 pm.• The method comprised adding starch to the respective fibrous composition in the form of a solid composition, such as a powder or granules or flakes.• The method comprised adding starch to the respective fibrous composition in the form of a dry composition comprising at least 40 wt-%, such as at least 60 wt-%, such as at least 80 wt-%, such as at least 90 wt-%, calculated from the total weight of the composition.• The method comprises adding starch to the respective fibrous composition in the form of a water solution, in a dissolved form, the solution comprising at least 5 wt- %, such as 10 to 50 wt-% starch, calculated from the total weight of the solution.• At least one of the fibrous compositions comprises fibrillated fibres, such as microfibrillated cellulose (MFC), nanofibrillated cellulose (NFC), microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC), cellulose microfibrils (CMF), cellulose nanofibers (CNF), cellulose nanocrystals (CNC), cellulose nanowhiskers or any combinations thereof.• At least one of the fibrous compositions comprises starch and a size.• At least one of the fibrous compositions comprises starch, a size, and a retention aid and optionally fibrillated fibres, such as microfibrillated cellulose.• The method comprises adding to at least one of the fibrous compositions, such as to all fibrous compositions independently from each other, a foaming agent; foaming said at least one fibrous composition; and forming said at least one foamed fibrous composition in the mould.• All fibrous layers of the product are foam-formed in the mould.• The density of the foam is in the range of 100 to 700 kg / dm3, such as 250 to 500 kg / dm3, such as 300 to 400 kg / dm3.• The stability of the foam is in the range 10 to 400 ml, such as 20 to 300 ml, such as 50 to 250 ml, such as 60 to 200 ml, measured as the water volume separated from the foam volume of 1 litre during 10 minutes.• The turbidity of the foam is in the range 0 to 550 NTU, such as 2 to 300 NTU, such as 3 to 200 NTU, such as 5 to 100 NTU.• Each foamed fibrous composition comprises, independently from each other, at least one surface-active foaming agent, such as an anionic surfactant, a zwitterionic surfactant, a non-ionic surfactant or any combination thereof.• The foaming agent is selected from the following group: sodium dodecyl sulphate (SDS), alkyl polyglycosides (APG), glycinates, glucamides, polyvinyl alcohol (PVA), and any combinations thereof.In each fibrous composition, independently from each other, at least 80 wt-%, such as at least 95 wt-% of the cellulosic fibres originate from perennial and / or annualplants, such as from wood, such as from wood pulp, calculated from the total dry weight of cellulosic fibres in said layer.• The first fibrous layer and the second fibrous layer are the outermost fibrous layers of the product.• The first fibrous layer and the second fibrous layer are both substantially free from starch and starch derivatives, for example comprising less than 0.1 wt-%, such as less than 0.05 wt-% of starch and starch derivatives, calculated from the dry weight of fibres.• At least one of the fibrous inner layers comprises at least 1 wt-%, such as at least 2 wt-%, for example 3 to 10 wt-% of starch, calculated from the dry weight of fibres.• At least 50 wt-%, such as at least 80 wt-% of the total dry weight of each fibrous layer, independently from each other, consists of cellulosic fibres originating from perennial and / or annual plants.• The first fibrous layer, which is the uppermost fibrous layer, comprises chemical pulp.• A fibrous inner layer comprises CTMP or BCTMP and additionally starch.• The second fibrous layer, which is the lowermost fibrous layer, comprises chemical pulp.• The density of the moulded multi-layered fibrous product is at least 200 kg / m3, such as in the range of 200 to 900 kg / m3, such as 500 to 850 kg / m3, calculated as dry solids weight per volume.

[0013] Advantages of the invention

[0014] The present invention may provide an improved method for manufacturing of moulded multi-layered fibrous products, particularly multi-layered foam-formed moulded fibrous products.

[0015] Some embodiments of the present invention may provide increased retention of wet-end chemicals, which results in a decrease in turbidity from the foam filtrate and a decrease in the water Cobb value of the fibrous product. Turbidity measures the cloudinessof the water in the foam filtrate caused by free wet-end chemicals and fines and is desired to be reduced. The turbidity decreases when the wet-end chemicals and fines are secured to the fibres in the foam. Water Cobb value is a measure of water resistance determined by the amount of water absorbed into the product after a given time.

[0016] Some embodiments of the present invention may improve oil and grease barrier properties of the product. Oil and grease barrier properties are advantageous in food contact products. The present invention may increase the density of the structure, which may improve oil and grease barrier performance.

[0017] Some embodiments of the present invention may increase foam stability, typically by limiting the bubble size growth in the foam so that undesired interactions between different chemicals, such as sizes and surfactants, become reduced. Also, by means of the present method, the amount of a foaming agent required to achieve a foam with a particular foam density and foam stability may be decreased. Since the foaming agents typically interfere with the retention of chemicals in the fibrous composition, the reduced use of surfactant may lead to improved retention of chemicals.

[0018] The reduced use of foaming agents may reduce foaming agent residues found in the final product. This is advantageous when considering food contact regulations that regulate the acceptable surfactant residue levels in the end product.

[0019] Some embodiments of the present invention may improve retention of wetend chemicals, such as sizes.

[0020] Some embodiments of the present invention may increase foam stability, typically by limiting the bubble size growth in the foam so that undesired interactions between different chemicals, such as sizes and surfactants, become reduced.

[0021] The present invention may facilitate incorporation of starch in moulded fibre products, by simplifying equipment requirements and by lowering water and energy consumption.

[0022] In some embodiments of the present invention, due to the multi-layered structure, it is possible to incorporate starch while still enabling effective use of elevated temperatures in contact drying, such as hot pressing.BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIGURE 1 schematically illustrates a multi-layered fibrous product in accordance with at least some embodiments of the present invention.EMBODIMENTS

[0024] DEFINITIONS

[0025] Unless otherwise stated herein or clear from the context, any percentages referred to herein are expressed as percent by weight based on the total dry weight of the respective composition.

[0026] The amounts of additives are usually expressed as percent by weight, calculated from the weight of dry fibres in the respective composition.

[0027] In the present context, the term “hot pressing” typically refers to a method of applying increased pressure and increased temperature for a period of time. Hot pressing may involve several successive cycles or steps of applying increased pressure and temperature. In some instances, hot pressing may involve application of sub-atmospheric pressure. Typically, an aim of a hot pressing step is to obtain a strong and dimensionally stable product with smooth product surfaces.

[0028] In the present context, the term “moulded fibrous product” refers to a product obtained by shaping and dewatering a fibrous composition, such as a slurry or a foam, inside a closed or closable cavity of a mould.

[0029] In the present context, the term “cellulosic fibrous material” or “cellulosic fibres” may refer to a material or fibres comprising cellulosic and / or lignocellulosic fibres.

[0030] Unless otherwise stated herein or clear from the context, the term “fibres” refers to cellulosic and / or lignocellulosic fibres.

[0031] Typically, the term “top fibrous layer” or “the uppermost fibrous layer” refers to the fibrous surface layer that is to be located nearest to or in contact with the content of the package, such as food.

[0032] Typically, the term “bottom fibrous layer” or “the lowermost fibrous layer” refers to the fibrous surface layer that is located on the opposite side of the fibrous structure with regard to the top fibrous layer.

[0033] Typically, the term “surface-active foaming agent” refers to a surfactant.

[0034] In the present context, the term “fibrillated fibres” may refer to any of the following: microfibrillated cellulose (MFC), nanofibrillated cellulose (NFC), microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC), cellulose microfibrils (CMF), cellulose nanofibers (CNF), cellulose nanocrystals (CNC), cellulose nanowhiskers and any combinations thereof.

[0035] Typically, the term “fibrillated fibres” or the term “microfibrillated cellulose (MFC)” refers to a cellulosic fibrous material which has undergone supplemental or additional fibrillation in comparison to conventional cellulosic pulp fibres originating from a papermaking process. For example, the Schopper-Riegler number of the fibrillated fibres may be at least 90.

[0036] The present products are typically three-dimensional moulded single- or multi-layered fibrous products obtained by using a foam-forming process.

[0037] We have observed that adding starch to the fibrous furnish may provide unexpected benefits in the manufacturing of moulded fibre products, such as foam-formed moulded fibre products. Particularly, the presence of starch in the furnish may alleviate or solve problems related to retention of additive chemicals that tend to interact with each other or with the cellulosic fibres. Starch may interact with additive chemicals and fibres for example via hydrogen and / or ionic bonding. Also starch derivatives or other suitable polysaccharides, such as glycogen, galactogen or inulin, may be used in the present invention.

[0038] The increased retention of wet-end chemicals may be observed for example as a decrease of turbidity of the foam filtrate and as a decrease in the water Cobb value of the fibrous product.

[0039] Advantageously, incorporation of starch into a fibrous layer of a multilayered moulded fibrous product may impart an oil and grease barrier due to the increase in density of said fibrous layer.

[0040] Also, incorporation of starch into a fibrous layer of a multi-layered moulded fibrous product may enhance barrier properties of said layer due to improved retention of barrier agents.

[0041] We have also observed that the foam forming method is particularly suited to accommodate incorporation of starch as one component of the fibrous furnish.

[0042] By means of the present process, a more varied selection of additive chemicals may become available.

[0043] In an embodiment, the present invention provides a method comprising: providing a first fibrous composition and a second fibrous composition and one or more further fibrous compositions, each comprising independently from each other cellulosic fibres and water, wherein at least one of the further fibrous compositions further comprises starch or a starch derivative; in a mould, forming and dewatering the first fibrous composition, the second fibrous composition and the one or more further fibrous composition to obtain a first fibrous layer (the uppermost fibrous layer), a second fibrous layer (the lowermost fibrous layer) and inner fibrous layers, respectively, in a stacked configuration; and hot pressing the stack comprising the first fibrous layer, the second fibrous layer and the one or more inner fibrous layers, to obtain a moulded multi-layered fibrous product.

[0044] Preferably, the method comprises: providing a first fibrous composition and a second fibrous composition and one or more further fibrous compositions, each comprising independently from each other cellulosic fibres, water, and optionally additive chemicals, wherein at least one of the fibrous compositions further comprises starch or a starch derivative; in a mould, forming and dewatering the first fibrous composition, the second fibrous composition and the one or more further fibrous composition to obtain a first fibrous layer, a second fibrous layer and inner fibrous layers, respectively, in a stacked configuration; and hot pressing the stack comprising the first fibrous layer, the second fibrous layer and the one or more inner fibrous layers, to obtain a moulded multi-layered fibrous product.

[0045] In preferred embodiments, the first fibrous layer is the uppermost fibrous layer, and the second fibrous layer is the lowermost fibrous layer in the product.

[0046] Cellulosic fibres

[0047] The cellulosic fibres may comprise wood pulp, such as hardwood pulp and / or softwood pulp.

[0048] In each fibrous layer, independently from each other, at least 80 wt-%, such as at least 95 wt-% of the cellulosic fibres may originate from perennial and / or annual plants, such as from wood, such as from wood pulp, calculated from the total dry weight of cellulosic fibres in said layer.

[0049] In an embodiment, at least 50 wt-%, such as at least 70 wt-%, such as at least 80 wt-% of the total dry weight of each fibrous layer, independently from each other, consists of cellulosic fibres originating from perennial and / or annual plants.

[0050] The softwood pulp may be made from spruce or pine or mixtures thereof.

[0051] The hardwood pulp may be made from birch, poplar, aspen, alder, maple, eucalyptus tropical hardwood, or mixtures thereof.

[0052] The wood pulp may be a mixture of hardwood and softwood pulp.

[0053] In one embodiment, the cellulosic fibres may comprise pulp made from any annual plants, such as straw, common reed, reed canary grass, bamboo, sugarcane, bagasse or any grass plant.

[0054] In an embodiment, the cellulosic fibres comprise hardwood pulp and softwood pulp at a weight ratio in the range 1 :5 to 5 : 1 , such as in the range 1 :3 to 3 : 1 , such as in the range 1 :2 to 2: 1.

[0055] The cellulosic fibres may comprise wood pulp selected from the following group: chemical pulp, mechanical pulp, and any combinations thereof.

[0056] Chemical pulp is manufactured by a chemical pulping method. Examples of chemical pulping methods included kraft (sulphate) pulping, sulphite pulping, polysulphide pulping, organosolv pulping, and soda pulping.

[0057] Mechanical pulps are exemplified by ground wood and pressure ground wood, refiner mechanical pulp, thermomechanical pulp, chemi-thermomechanical pulp, and bleached chemi-thermomechanical pulp. The pulp can be bleached, for example by methods involving oxidizing bleaching chemicals, such as chlorine dioxide, ozone, peroxide and peroxo acids and combinations thereof.

[0058] The cellulosic fibres may comprise recycled fibres, broke fibres, such as trim waste, agricultural fibrous waste streams, annual plant fibres, fibrous by-products, regenerated cellulose fibres, and combinations thereof. In an embodiment, the cellulosic fibres comprise broke from a paper, paperboard or moulded pulp manufacturing process.

[0059] Preferably, at least one of the fibrous layers, such as the uppermost fibrous layer, comprises refined cellulosic fibres. The fibres may be refined to have a Canadian Standard Freeness (CSF) of less than 350, such as less than 250.

[0060] Advantageously, at least one of the fibrous layers, for example an inner layer or the lowermost layer, comprises chemi-thermomechanical wood pulp (CTMP) and / or bleached chemi-thermomechanical wood pulp (BCTMP). The CTMP or BCTMP may be refined to a Canadian Standard Freeness of less than 800 ml, such as 450 to 800 ml. The CTMP or BCTMP may also be unrefined.

[0061] In an embodiment, the uppermost fibrous layer comprises chemical pulp.

[0062] In an embodiment, a fibrous inner layer comprises CTMP, such as BCTMP, and / or chemical pulp. Preferably said inner layer comprises starch.

[0063] In an embodiment, a fibrous inner layer comprises CTMP, such as BCTMP, and / or broke. Preferably said inner layer comprises starch.

[0064] In an embodiment, the lowermost fibrous layer comprises CTMP, such as BCTMP, and / or chemical pulp.

[0065] The cellulosic fibrous material may also comprise non-wood pulp, such as straw pulp.

[0066] In some embodiments, the cellulosic fibrous material comprises or substantially consists of virgin wood pulp, such as virgin bleached chemical pulp that is substantially free from lignin, which makes the product particularly suitable for food contact, for example for cooking, heating, ovening and micro-ovening. Preferably, at least one of the fibrous layers, such as the uppermost fibrous layer, comprises virgin cellulosic fibres.

[0067] In an embodiment, in at least one of the fibrous layers, such as the uppermost fibrous layer, at least 80 wt-%, such as at least 95 wt-% of the cellulosic fibres consists of virgin cellulosic fibres, such as virgin wood pulp.

[0068] An advantage of virgin pulp is that it is free from pigments and other undesired chemicals. Recycled waste materials often contain chemical and microbiological contaminants, which may affect their safe use. Mixtures of chemical compounds and microbial products may leach out from recycled materials and cause a variety of negative health or environmental impacts. Not only the harmfulness of individual chemical compounds, but also their interactions with other chemical compounds and microbial products may increase the toxicity of recycled materials and their emissions. Therefore, the present invention preferably avoids use of recycled materials.

[0069] In some embodiments, recycled materials may be used.

[0070] An advantage of chemical pulp, such as bleached chemical pulp, is that it is substantially free from lignin. A further advantage of chemical pulp is that inter-fibre bonding in the end product may be better than in the case of mechanical pulp.

[0071] Lignin-containing pulps often have an insufficient organoleptic quality for direct food contact. In addition, lignin-containing pulps are sensitive to ageing and yellowing of the material.

[0072] Starch

[0073] In an embodiment, said at least one of the fibrous compositions comprises at least 1 wt-%, such as 1 to 20 wt-%, such as 1 to 5 wt-%, or 5 to 10 wt-% starch, calculated from the total dry weight of fibres.

[0074] In an embodiment, said at least one of the fibrous compositions comprises at least 1 wt-%, such as at least 2 wt-%, for example 3 to 10 wt-% of starch, calculated from the total dry weight of fibres.

[0075] For example, the fibrous composition for an inner layer of the multi-layered fibrous product may comprise starch or a starch derivative.

[0076] In an embodiment, all inner fibrous layers comprise starch or a starch derivative.

[0077] In an embodiment, only one or more inner fibrous layers comprise starch. In this way it is possible to increase the density of these fibrous layers and to improve for example their grease barrier properties. The other fibrous layers, particularly the outermost fibrous layers, are preferably substantially free from starch and starch derivatives.

[0078] A significant advantage of including starch only in inner fibrous layers is that problems related to hot pressing starch-containing fibrous layers may be reduced or avoided. Starch is sticky in the wet phase and therefore prone to adhere or stick to heated plates of a hot press. By incorporating starch only in inner parts of the structure to be hot pressed, it may be possible to avoid contact between starch and the hot plates. The outer layers may effectively protect the starch from migrating to outer surfaces of the structure during the hot pressing. For example, the outer layers of a three-layer structure protect the starch dosed to the middle layer from the hot press surfaces. This may allow the hot press device to run smoothly.

[0079] The starch or the starch derivative may comprise or consist of ungelatinized starch or uncooked starch or non-solubilised starch.

[0080] Preferably, the starch or the starch derivative in said at least one fibrous composition comprises or consists of ungelatinized starch or uncooked starch or nonsolubilised starch.

[0081] For example, the starch or the starch derivative has not been pre-gelatinized, such as gelatinized before the hot pressing step.

[0082] The starch or the starch derivative may become gelatinized during the hot pressing. Typically, the gelatinization takes place as a consequence of the water and the high temperatures and pressures present in the hot pressing stage.

[0083] In some embodiments, the starch comprises starch originating from one or more of the following: com, potato, maize, wheat, tapioca, barley, quinoa, pea, rice.

[0084] In some embodiments, the starch comprises a waxy starch.

[0085] In some embodiments, the starch has a high amylose content, such as at least10 wt-%, such as at least 15 wt-%, such as at least 20 wt-%, such as at least 25 wt-%, such as at least 28 wt-%, such as at least 30%, for example 15 to 35 wt-%, calculated from dry matter.

[0086] In some embodiments, the starch has a low amylose content, such as less than 5 wt-%, calculated from dry matter.

[0087] Typically, the starch has a degree of substitution (DS), defined as the number of substituents per glucopyranosyl unit, of at least 0.005, such as in the range 0.005 to 1, such as 0.01 to 0.5, such as 0.02 to 0.2.

[0088] In some embodiments, the starch or the starch derivative comprises unmodified starch or modified starch, such as oxidized starch, hydroxyethylated starch, cationic starch, anionic starch, grafted starch, hydrophobic starch, aldehyde starch, mechanically-modified starch, thermally modified starch, or any combination thereof.

[0089] The starch derivative may comprise a chemically modified starch or a decomposition product of starch, such as dextrin, such as thermally modified dextrin.

[0090] In an embodiment, the average particle size of the starch is 1 to 50 pm, such as 5 to 40 pm, such as 10 to 30 pm.

[0091] Forming

[0092] One or more of the fibrous layers of the product, or the entire product, may be obtained by moulding, either by a wet forming method (water forming) or by a foam forming method. The method preferably comprises a drying step by hot pressing.

[0093] Advantageously, one or more of the fibrous layers of the product are obtained by a foam forming method. In an embodiment, all fibrous layers are foam-formed in the mould.

[0094] In an embodiment, the method comprises adding to at least one of the fibrous compositions, such as to all fibrous compositions independently from each other, a foaming agent; foaming the fibrous composition(s); and forming the foamed fibrous composition(s) in the mould.

[0095] In foam forming, the fibrous layer is formed of a foamed fibrous composition comprising cellulosic fibres, water and a foaming agent. In an embodiment, the foamed fibrous composition for at least one fibrous layer further comprises starch.

[0096] The multi-layered product is preferably obtained so that all cellulosic fibres to be included in the end structure undergo a foam forming process.

[0097] For example, at least the fibrous layer comprising starch has been obtained by a foam forming method in a mould. Such a fibrous layer may be one or more of the inner fibrous layers.

[0098] During foam forming, the starch particles may become entrapped within the fibrous structure or matrix. In the hot pressing step, the starch may gelatinize and the voids in the foam-formed fibrous matrix may become filled.

[0099] The advantage of foam forming is that lighter and bulkier products may be prepared. Additionally, a more homogeneous formation may be achieved. Use of foam enables facile preparation of multi-layered structures in a modular process, i.e. all layers may be formed in the same mould but still with an individually tailored composition and selection of fibrous raw materials and additives in each layer to form a multi-layered shape or structure in the mould, which structure is then hot pressed. Advantageously, one or more of the fibrous layers may be tailored to comprise starch, while the other fibrous layers may be free from starch.

[0100] An advantage of dewatering the entire multilayer structure in the same mould is that inter-layer bonding may be enhanced also during the dewatering in comparison to dewatering the layers individually.

[0101] In some embodiments, in addition to foam-formed layers, the end product may further comprise water-formed layers. Such water-formed layer or layers may be formed in a separate process and combined with the foam-formed layer or the foam- formed multi-layered structure by hot pressing. An advantage of water forming is that foaming chemicals are absent and therefore do not interfere with the functioning of sizes. In water forming methods, the individual layers are typically formed and removed from the mould independently from each other. Separate moulds may be used. After being removed from the mould(s), the layers may be piled into a stack and joined to each other and / or to other layers by hot pressing.

[0102] In some embodiments, in addition to foam-formed layers, the end product may further comprise water-formed layers, and all layers, i.e. the water-formed layer or layers and the foam-formed layer or layers, are formed in the same mould, to form a multilayered shape or structure in the mould, which structure is then hot pressed.

[0103] In one embodiment, the product comprises several fibrous layers that are prepared by water forming processes and combined to each other and optionally additionally to at least one foam-formed fibrous layer. Advantageously, the foam-formed layer or layers constitute one or more of the inner fibrous layers, such as the middle layer of the product and advantageously comprise starch.

[0104] In an embodiment, the product may comprise one or more water-formed layers and one or more foam-formed layers. In an embodiment, an inner fibrous layer or inner fibrous layers have been water-formed, and the top and bottom fibrous layers have been foam-formed.

[0105] The steps of preparing a foamed composition and forming a fibrous layer from the foamed composition may be carried out in different alternative ways.

[0106] Preferably, the starch may be added, such as dosed, in the form of a dry composition, such as a powder. An advantage of dosing dry starch is that additional preparation steps, such as dissolving starch in water or other solvent for example by heating, may be avoided.

[0107] When dosing starch in the form of a dry composition, such as in powder form, it is preferred to use foam forming for the respective fibrous layer. In the foam, it may be easy to achieve a homogeneous distribution of the dosed dry starch on surfaces of bubbles.

[0108] In some embodiments, the starch is dosed directly to a foaming tank. An advantage is that effective mixing of the starch, particularly dry starch, with the other components of the foam may be achieved.

[0109] The starch may be added to the respective fibrous composition in the form of a solid composition, such as a powder or granules or flakes, comprising starch.

[0110] For example, the starch may be added in the form of a solid or dry composition comprising at least 40 wt-%, such as at least 60 wt-%, such as at least 80 wt- %, such as at least 90 wt-% starch, calculated from the total weight of the composition.

[0111] Alternatively, the starch may be added to the respective fibrous composition in the form of an aqueous composition comprising starch.

[0112] In some embodiments, the starch is added in the form of a water solution, in a dissolved form, comprising at least 5 wt-%, such as 10 to 50 wt-% starch, calculated from the total weight of the solution.

[0113] Various method sequences may be applied to achieve generation of a foamed mixture:

[0114] In some embodiments, cellulosic fibres and starch are mixed first. The starch may be added in the form of a dry powder. For example, a composition such as a fibre slush comprising cellulosic fibres and water and having a consistency of at least 0.5% may be mixed with a dry powder of starch. Thereafter, wet-end additive chemicals and a foaming agent are added to the mixture. Finally, the mixture is turned into a foamed composition by applying mixing.

[0115] In some embodiments, the cellulosic fibres and at least one additive chemical are mixed first. Thereafter, starch is added to the mixture, followed by adding a foaming agent and optionally further additive chemicals. Finally, the mixture is turned into a foamed composition by applying mixing.

[0116] In some embodiments, the cellulosic fibres, for example in the form of a fibre slush with a consistency of at least 0.5%, additive chemicals and a foaming agent are mixed first. The mixture is turned into a foamed composition by applying mixing. Thereafter, starch, such as dry starch powder, is added to the foamed composition.

[0117] Generally, before adding starch, the fibre slush has a consistency of approximately 0.5 to 7% by weight, calculated as the weight of fibres in relation to the total weight of the slush.

[0118] A different type of foamed fibrous composition may be used for preparing each layer of a multi-layered product. Each foamed composition may comprise a dedicated set of foaming agents and other additives, such as hydrophobic agents. By “different type” it is referred to having a different composition, such as different foaming agents and additive selections and / or different concentrations.

[0119] The foaming agent preferably comprises a surface-active foaming agent, such as a surfactant, and / or a non-ionic polymeric foaming agent or a mixture thereof. In an embodiment, the foaming agent comprises a surfactant.

[0120] In an embodiment, the surfactant has been synthesized at least partly, preferably entirely from renewable raw materials. The surfactant may be at least partially bio-based, such as 100% (entirely) bio-based.

[0121] One or more foaming agents may be used in each of the fibrous layers independently from each other.

[0122] The surfactant may be non-ionic, anionic, cationic or amphoteric. Preferably, the surfactant is a non-ionic surfactant or an anionic surfactant, or a combination of a nonionic surfactant and an anionic surfactant is used.

[0123] The total amount of foaming agents in each foamed fibrous composition may be in the range 0.1 to 50 wt-%, for example 5 to 20 wt-% or for example 1 to 3 wt-% or for example 0.1 to 1 wt-%, calculated from the mass of dry fibres in said foamed fibrous composition.

[0124] A suitable amount of a surfactant, such as an anionic surfactant is 0.2 to 5 g / L (grams per one litre of fibrous stock).

[0125] A suitable amount of a surfactant, such as an anionic surfactant is 1 to 20 wt- % per dry fibre.

[0126] The anionic surfactant may be selected from the following group: sodium dodecyl sulphate (SDS), alpha-olefin sulphonates, alkyl sulphates, alkylbenzene sulphonates, alkyl ethersulphates, taurates, isethionates, and combinations thereof.

[0127] Examples of non-ionic foaming agents include non-ionic polymeric foaming chemicals, such as polyvinyl alcohol, and non-ionic surfactants, such as glycosides.

[0128] The foaming agent may be selected from the following group: SDS, polyvinyl alcohol (PVA), polyethylene glycol dodecyl ether (Brij), polyethylene glycol sorbitan monolaurate (Tween 20), PEG-6 lauramide, alkyl polyglycosides (APG), such as alkyl polyglucosides, fatty alcohol ethoxylates, alkylphenol ethyxolates, fatty acid ethyxolates, fatty amide ethyxolates, alkyl glycosides, such as alkyl glucosides, sugar based non-ionic polymers, such as sorbitan alkanoates, and combinations thereof.

[0129] In some embodiments, the foaming agent may be selected from anionic surfactants and non-ionic surfactants.

[0130] In an embodiment, the foamed fibrous composition for at least one fibrous layer comprises an anionic surfactant, such as SDS, and a non-ionic surfactant, such as a glucamide. In an embodiment, the foamed fibrous composition for at least one fibrous layer comprises SDS and an alkyl polyglycoside (APG). In some embodiments, the foaming agent may be selected from the following group: SDS, alkyl polyglycosides (APG), glycinates, glucamides and any combinations thereof.

[0131] Advantageously, by dosing starch to fibre slush prior to adding any foaming agents, the amount of foaming agent required may be decreased. Since foaming agents and surfactants may interfere with retention of chemicals in the fibrous structure, use of starch may improve retention in this way indirectly.

[0132] Foaming agents such as surfactants, and additives more generally, may be arranged to recirculate in the present method.

[0133] The density of the foam may be in the range 100 to 700 kg / dm3.

[0134] Preferably, the stability of the foam is in the range 10 to 400 ml, such as 20 to300 ml, such as 50 to 250 ml, such as 60 to 200 ml, measured as the water volume separated from the foam volume of 1 litre during 10 minutes.

[0135] The turbidity of the foam may be in the range of 0 to 550 NTU, such as 2 to 300 NTU, such as 3 to 200 NTU, such as 5 to 100 NTU.

[0136] Typically, the bubble size (diameter) in the foam is approximately 10 to 300 pm, for example 50 to 250 pm, usually approximately 100 to 150 pm.

[0137] The temperature of the foam may be in the range of 15 to 55 °C, such as 20 to 40 °C, such as 24 to 30 °C.

[0138] In one embodiment, a composition suitable for foaming is obtained by mixing fibre slush (fibre stock), which may already contain starch, with a foam which is formed from water and a foaming agent and the air content of which is approximately 10 to 90% by volume, for example 20 to 80%, such as 50 to 75%, such as 60 to 70% by volume. A foamed fibre slush is generated, and it may have a fibre content of approximately 0.1 to 3% by weight.

[0139] In one embodiment, instead of mixing the fibre slush with a pre-generated foam, a foaming agent may be added to the fibre slush, which may already contain starch. The mixture is thereafter foamed to obtain a foamed fibre slush. The mixture to be foamed may have a consistency in the range 0.5 to 3%, such as 0.8 to 2.7%, such as 1.0 to 2.5%.

[0140] In the present context, “forming”, typically foam forming, refers to the process of giving the foamed composition a shape, such as a three-dimensional shape, in a mould.

[0141] In the preferred method, a foamed fibrous composition is fed to a mould, typically to a cavity in a mould. The mould typically comprises a cavity or an inner space defined by the mould’s inner surfaces. In the cavity the fed foamed composition is shaped. The cavity may have a dimension, such as the shortest dimension, in the range 0.1 to 100 mm, such as 3 to 100 mm, such as 5 to 60 mm, in the closed configuration of the mould.

[0142] Said shortest dimension or smallest dimension typically refers to the thickness of the product or layer to be moulded.

[0143] The foamed composition may be fed to the mould to provide an amount of the foamed composition, such as a layer of the foamed composition, onto at least one inner surface of the mould. The layer is typically non-planar and may be understood as a thickness, such as a variable thickness or a substantially constant thickness, of the foamed composition lying on the inner surface of the mould and conforming to the shape of said surface.

[0144] Typically, the shaping step comprises pressing said fibrous composition in the inner space of the mould by making parts of the mould approach each other.

[0145] The step of forming a multi-layered foamed structure may comprise feeding a first fibrous composition in a foamed form into the mould, and shaping said first fibrous composition in the mould, to prepare a first foamed fibrous layer. Thereafter, without removing the first fibrous layer from the mould, the process is continued by feeding a further fibrous composition in a foamed form into the mould, and shaping said further fibrous composition in the mould, to prepare a further foamed fibrous layer. As a result, a two-layered moulded foamed structure is obtained in the mould. The process may be continued to add yet further fibrous layers to the moulded foamed structure.

[0146] The fibrous compositions may differ from each other for example with regard to the foaming agents and additives such as barrier agents or hydrophobic agents, and / or with regard to the cellulosic fibres. Importantly, they may differ from each other with regard to the concentration and / or the type of starch present, if any.

[0147] If not otherwise stated, by “parts of the mould” it is referred to such parts of the mould that serve to define the inner space and thus contribute to shaping the foamed fibrous composition.

[0148] The further foamed fibrous layer may be fed and thus become located either on top of or alternatively under the first foamed fibrous layer in the mould. Also, said feeding steps may be carried out in either order: either the first layer or the further layer may be formed first into the mould.

[0149] For example, when preparing a multi-layered moulded foamed structure, the layers may be formed in any suitable order. An inner (to-be) fibrous layer may be formed first, and the top and bottom fibrous layers thereafter on both sides of the inner fibrous layer. Alternatively, the top (to-be) fibrous layer or the bottom (to-be) fibrous layer may be formed first, and the other fibrous layers thereafter.

[0150] It may also be envisaged that the product is obtained by using separate moulds for preparing said first and further foamed fibrous layers, and the obtained first and further fibrous layers are joined in said hot pressing step.

[0151] In one embodiment, said feeding into the mould comprises feeding the foamed fibrous composition in a foamed form into an inner space or inner volume of the mould, wherein said inner space is limited by inner surfaces of the mould.

[0152] Application of vacuum in the dewatering step is preferably enabled.

[0153] The final multi-layered foamed structure is removed from the mould by opening the mould.

[0154] Adjusting the distance between the parts of the mould during feeding and shaping of the foamed compositions is preferably enabled.

[0155] Before starting to feed a further fibrous composition into the mould, it is typically necessary to enlarge the inner space of the mould by moving the parts of themould farther from each other. The volume of the inner space may be diminished or enlarged to shape the already-fed foam and, respectively, to make room for the foam to be fed next.

[0156] In all adjustments of the volume of the inner space of the mould, some parts of the mould may remain stationary while other parts are moved.

[0157] In one example, one or more parts of the mould remain stationary and one or more other parts of the mould move during said approaching or during said enlarging.

[0158] For example, the mould may comprise two submoulds, such as two halves, that are arranged to face each other and to be movable with regard to each other. The submoulds may be approached towards each other to shape the product. The submoulds may be moved apart from each other to enlarge the inner space or even farther to open the mould and to remove the shaped product from the mould.

[0159] In one example, the product is obtainable by using a mould comprising two parts: a negative mould and a positive mould, which may be arranged to face each other to encase an inner space, also referred to as a moulding space or moulding cavity, between the two parts. The composition to be moulded or shaped is fed into the moulding space and the negative mould and / or the positive mould are approached toward each other to give the composition the shape corresponding to the shape of the moulding space. By ‘approaching’, it is referred to a process in which the inner space is diminished by means of moving one or both of the positive and negative moulds.

[0160] Dewatering of the structure may be carried out by applying a vacuum to the inner space of the mould containing the fed foamed composition(s).

[0161] The dewatering step precedes the hot pressing step, which hot pressing leads to the final, typically smooth and dry product in which all layers have been joined to each other.

[0162] In the hot pressing, the temperature, such as the temperature of a pressing plate or pressing plates of a hot press, is typically higher than room temperature, for example at least 50 °C, such as at least 100 °C, for example in the range at least 150 to 250

[0163] In some embodiments, the hot pressing comprises pressing the stack between two shaped pressing plates, of which at least one, preferably both, has a temperature of at least 150 °C, such as 150 to 270 °C, such as 180 to 250 °C, such as 190 to 225 °C.

[0164] In the hot pressing, a sub-atmospheric pressure may be applied, for example a pressure of 600 kPa or less.

[0165] The hot pressing may comprise two or more successive steps of hot pressing. Said hot pressing steps may have a combined duration of less than 60 seconds, such as less than 30 seconds.

[0166] During hot pressing, heat (elevated temperature) may be applied from one or both sides of the material to be pressed. In an embodiment, heat is applied only from one side.

[0167] During hot pressing, heat may applied only from one side of the multilayered fibrous structure, and the outermost fibrous layer on said side of the multi-layered fibrous structure may be substantially free from starch.

[0168] For example, the hot pressing may involve two hot pressing steps in both of which heat is applied from the same side. Alternatively, the hot pressing may involve two hot pressing steps in which heat is applied from different sides.

[0169] Hot pressing may contribute to development of the barrier or other functional properties, for example via chemical reactions taking place in elevated temperatures, such as cross-linking and curing reactions. Therefore, hot pressing may be advantageous when using additive chemicals the action of which becomes enhanced by cross-linking or curing.

[0170] Hot pressing may also contribute to the flow of additives such as barrier agents or hydrophobic agents within the multi-layered fibrous structure.

[0171] Hot pressing may contribute to the flow of barrier chemicals. For example, hot pressing from one side may direct flow of a barrier chemical within the layers in a different way when compared to hot pressing symmetrically from both sides.

[0172] Hot pressing preferably comprises impulse drying.

[0173] Impulse drying typically comprises wet-pressing with the application of heat. The applied heat may have two roles: It may reduce the viscous resistance of the water andit may soften the structure of the pulp, so that it becomes more compressible, resulting in a smooth surface. If the heat transfer rate is sufficiently high, a vapor phase may be generated on the wet side in contact with the high temperature medium. This may assist in the dewatering process as the expanding steam can displace the bound water.

[0174] Optionally, after the hot pressing step the product may be incubated at a temperature of 50 to 110 °C, for example for 5 to 60 min, to further improve or stabilize the barrier properties of the product.

[0175] Additives, barrier properties and sizing

[0176] At least one of the fibrous layers may comprise one or more of the following optional additives: pigments, such as talc, clay, and calcium carbonate; retention aids; fixatives; barrier agents; latex binders; water-soluble binders, wet strength agents, CMC; sizes, such as AKD and waxes; nanostructured or microstructured cellulose; and any combinations thereof. The layer containing an optional additive may be a layer containing starch or a layer not containing starch. The amount of an optional additive may be in the range 0.01 to 30 wt-%, such as 0.01 to 10 wt-%, such as 0.1 to 8 wt-%, for example 1 to 5 wt-%, calculated from the weight of dry fibres in the fibrous layer. In each individual fibrous layer the amount and nature or function of optional additives may be selected individually from each other. Preferably via contribution of optional additives via their presence or absence in each fibrous layer individually, the properties of the entire product can be optimised.

[0177] Preferably, at least one of the fibrous layers, such as the uppermost fibrous layer, comprises fibrillated fibres, such as microfibrillated fibres, such as nanostructured cellulose or microstructured cellulose, as an optional additive.

[0178] In an embodiment, at least one of the fibrous layers may comprise 0.1 to 5 wt-% starch and 0.1 to 5 wt-% fibrillated fibres, such as microfibrillated fibres, calculated from the total dry weight of fibres.

[0179] In the present context, the term “fibrillated fibres ” may refer to any of the following: microfibrillated cellulose (MFC), nanofibrillated cellulose (NFC), microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC), cellulose microfibrils (CMF), cellulose nanofibers (CNF), cellulose nanocrystals (CNC), cellulose nanowhiskers and any combinations thereof.

[0180] Preferably, at least one of the fibrous layers comprises micro fibrillated cellulose. In an embodiment, at least one of the fibrous compositions may comprise 0.1 to 5 wt-% starch and 0.1 to 5 wt-% micro fibrillated cellulose, calculated from the total dry weight of fibres.

[0181] Typically, the term “fibrillated fibres”, such as the term “microfibrillated cellulose (MFC)”, refers to a cellulosic fibrous material which has undergone supplemental or additional fibrillation in comparison to conventional cellulosic pulp fibres originating from a papermaking process.

[0182] Microfibrillated cellulose may be referred to by any of the following synonymous terms: cellulose microfibrils, fibrillated cellulose, nanofibrillated cellulose, fibril aggregates, nanoscale cellulose fibrils, cellulose nanofibers, cellulose nanofibrils, cellulose microfibers, cellulose fibrils, microfibrillar cellulose, microfibril aggregrates and cellulose microfibril aggregates.

[0183] The starch and microfibrillated cellulose (MFC) may be added separately to the furnish, with the starch first and then MFC or vice versa. They can be mixed together before adding to the furnish.

[0184] The combination of microfibrillated cellulose and starch may make it possible for the product to retain larger amounts of starch. The combination of microfibrillated cellulose and starch may have a synergistic effect in increasing the strength of the product without increasing the density of the product to the same degree. In some embodiments, the microfibrillated cellulose and the starch do not bond to each other through chemical reactions when combined. Instead, starch and microfibrillated cellulose may help form cross-links of the pulp fibres in the foam, thereby improving the mechanical properties, such as strength, of the product.

[0185] Any of the fibrous layers of the product may be provided with improved barrier properties by refining the fibres and / or by adding barrier agents or hydrophobic agents or strengthening agents and / or by selecting suitable foaming agents. Different barrier properties may be provided to the fibrous layers. For example, one of the fibrous layers may exhibit oil and grease resistance while another fibrous layer may exhibit water resistance.

[0186] An example of a barrier additive is a size or a hydrophobic agent, typically for internal sizing and / or for surface sizing, preferably for internal sizing. In an embodiment, the size is configured to not inhibit or reduce the foaming action of the foaming chemicals.

[0187] The barrier additives may be added to the fibrous furnish or slush before the foaming step, at a consistency of for example 0.5 to 15%, such as 2 to 10%, and / or before the foam forming step, to the foam or to be mixed with the fibrous slush with said consistency.

[0188] The barrier additives are preferably added to the fibrous furnish or slush at a consistency of less than 10%, such as less than 5%.

[0189] In an embodiment, at least one of the fibrous layers comprises a size.

[0190] In some embodiments, different amounts of a size may be dosed to the fibrous compositions for individual layers of a multilayer product. For example, at least before the hot pressing, the fibrous composition for the bottom fibrous layer of the product may comprise less hydrophobic agent or size than the fibrous compositions for the other layers, particularly the top fibrous layer of the product. For example, the fibrous composition for the bottom fibrous layer may comprise 50 wt-% less size than the fibrous composition for the top fibrous layer. Preferably, during hot pressing or impulse drying, a part of the size dosed to the top fibrous layer will migrate to other fibrous layers.

[0191] The size may be a cationic size, an anionic size and / or a reactive size.

[0192] In some embodiments, the size is selected from the following group: styrene acrylate copolymers (SA), polyurethanes, alkylated urethanes, carboxymethylcellulose and its salts, alkyl celluloses, such as methyl cellulose and ethyl cellulose, styrene / maleic acid copolymer (SMA), di-isobutylene / maleic anhydride, acrylonitrile / acrylate copolymers, a rosin, a wax, such as alkyl ketene dimer (AKD) or paraffin wax, an oil, such as alkenyl succinic anhydride (ASA), and styrene acrylate emulsion (SAE).

[0193] An advantage of using a size is that undesired absorption of liquid and / or water and / or moisture into the foam-formed structure may be reduced. Thus, moistureresistance or water-resistance of the product is improved.

[0194] A preferred size is AKD, paraffin wax or a similar wax.

[0195] In one embodiment, at least one of the fibrous layers comprises barrier agents selected from the following group: polyolefins, polyesters, other thermoplastic polymers, biodegradable polymers, such as polylactic acid, plastomers, elastomers, ethylene vinyl alcohol, and any derivatives, co-polymers and mixtures thereof.

[0196] In one embodiment, at least one of the fibrous layers comprises 0.1 to 15 wt- %, such as 0.1 to 10 wt-%, such as 0.1 to 5 wt-% barrier agents. Such barrier agents typically provide said barrier properties throughout the structure of the fibrous layer.

[0197] In one embodiment, at least one of the fibrous layers comprises 0.1 to 5 wt-% polyamide-epichlorohydrin (PAE). Preferably said fibrous layer also comprises a size, such as AKD. PAE may be capable of enhancing binding of the size to the fibres.

[0198] In one embodiment, at least one of the fibrous layers comprises a retention aid, for example 0.1 to 5 wt-% of a retention aid. The retention aid may be an anionic polymeric retention aid. The retention aid may be a cationic polymeric retention aid, such as cationic polyacrylamide. The retention aid may comprise microparticles, such as silica microparticles.

[0199] In one embodiment, at least one of the fibrous layers comprises a wet strength agent. The wet strength agent may be selected from the group consisting of polyamide epichlorohydrin, polyethylene imine, dialdehyde starch, polyacryl amides, glyoxal or melamine formaldehyde, polyamidoamineepichlorohydrin and urea formaldehyde melamine and any combinations thereof.

[0200] In one embodiment, at least one of the fibrous layers comprises a dispersion agent or a flotation agent.

[0201] Particularly, each fibrous layer may comprise less than 10 wt-%, such as less than 5 wt-%, such as less than 2 wt-% of thermoplastic materials, such as thermoplastic polymers, calculated from the total dry weight of the fibrous layer.

[0202] Preferably, the fibrous layers of the product comprise less than 10 wt-%, such as less than 5 wt-%, such as less than 2 wt-% of waxes, plastics and fluorochemicals. In one embodiment, the fibrous layers of the product comprise less than 2 wt-% of waxes. In one embodiment, the fibrous layers of the product comprise less than 2 wt-%, such as less than 1 wt-% of plastics. In one embodiment, the fibrous layers of the product comprise lessthan 2 wt-%, such as less than 1 wt-% of fluorochemicals. In some embodiments, the product is substantially free of waxes, plastics, such as thermoplastic materials, and fluorochemicals, particularly free of fluorochemicals.

[0203] For ovenable applications, the additives and the foaming chemicals may be selected among additives which are approved for use in food contact materials or packages and which additionally are approved for ovenable food packaging materials intended for heating. Preferably, the additives are selected among those approved in BfR XXXVI / 2. Paper and Paperboard for Baking Purposes: https: / / www.bfr.bund.de / cm / 349 / XXXVI-2- Paper-and-Paperboard-for-Baking-Purposes.pdf.

[0204] For products not intended for oven, the additives and the foaming chemicals may be selected more freely among all additives that are approved for use in food contact materials or packages.

[0205] By ‘food contact materials’ it is referred to all materials and articles intended to come into contact with food, such as packaging and containers and dishes.

[0206] Preferably, the present product complies with Regulation (EC) No 1935 / 2004.

[0207] In one embodiment, the starch as well as the optional additives are compliant with ovenable products.

[0208] Product

[0209] In some embodiments, the present invention provides a moulded multilayered fibrous product comprising: a first fibrous layer; a second fibrous layer; and at least one fibrous inner layer between the first and the second fibrous layers, wherein each fibrous layer comprises, independently from each other, a cellulosic fibrous material; and wherein at least one of the fibrous inner layers further comprises starch or a starch derivative, wherein the moulded multi-layered fibrous product has been obtained by a method in which a moulded stack comprising said fibrous layers is hot pressed between two shaped pressing plates of which at least one is in a temperature of 150 to 270 °C.

[0210] The first fibrous layer and the second fibrous layer may be the outermost fibrous layers and both may be substantially free from starch.

[0211] Preferably, at least one of the fibrous inner layers comprises at least 1 wt-%, such as at least 2 wt-%, for example 3 to 10 wt-% of starch, calculated from the dry weight of fibres.

[0212] In some embodiments, the product has a dry grammage in the range of 5 to 900 g / m2, for example in the range of 100 to 900 g / m2, such as in the range of 200 to 750 g / m2, such as 300 to 550 g / m2, such as 350 to 500 g / m2.

[0213] In an embodiment, each of the fibrous layers may have a dry grammage in the range of 30 to 500 g / m2, such as 40 to 400 g / m2, such as 50 to 350 g / m2, such as 60 to 300 g / m2.

[0214] In one embodiment, the lowermost fibrous layer and / or the inner fibrous layers of the product has a dry grammage in the range of 20 to 400 g / m2, such as 100 to 400 g / m2, such as 200 to 300 g / m2.

[0215] In one embodiment, the lowermost and the uppermost fibrous layers of the product each have a dry grammage in the range of 20 to 150 g / m2.

[0216] In one embodiment, an inner fibrous layer or the middle fibrous layer of the product has a dry grammage in the range of 100 to 400 g / m2, such as 150 to 250 g / m2.

[0217] In one embodiment, the first fibrous layer and / or the second fibrous layer of the product has a dry grammage in the range of 10 to 150 g / m2, such as 60 to 150 g / m2, or for example 20 to 60 g / m2, such as 30 to 50 g / m2.

[0218] In an embodiment, the density of the moulded multi-layered product is at least 200 kg / m3, such as in the range of 200 to 900 kg / m3, such as 500 to 850 kg / m3, calculated as dry solids weight per volume.

[0219] In an embodiment, the density of an inner fibrous layer or inner fibrous layers is larger than 100 kg / m3.

[0220] In some embodiments, the product may comprise 3 to 20 fibrous layers, for example exactly three fibrous layers.

[0221] Preferably, the product is a three-dimensional moulded multi-layered fibrous product, obtained by using a mould comprising at least one three-dimensional, non-planarmould surface, wherein said product exhibits a three-dimensional shape conforming to the shape of said three-dimensional, non-planar mould surface.

[0222] For example, the product may have a shape of a cup, a plate, a bowl, a pan, a clam-shell or a tray.

[0223] Typically, the product is a food or liquid packaging or container or a food or liquid serving product, such as a cup for a beverage or a food tray or plate or a baking pan or a disposable lasagne tray type product.

[0224] In some embodiments, the product is ovenable, such as ovenable to a temperature of at least 100 °C, preferably to at least 220 °C.

[0225] In some embodiments, the product is a micro-ovenable food or liquid packaging or container, such as a food tray.

[0226] In one example, the product is a container for baking, such as an ovenable pan.

[0227] The product may be used for packaging, storing, serving, preparing, cooking and / or heating of food or liquid. The liquid may be drinkable liquid, such as a beverage.

[0228] More generally, the product may be used for packaging and storing any oilcontaining and / or water-containing products.

[0229] The product may be a product intended to be used or located on greasy or oily and / or wet surfaces or in humid environments.

[0230] The product may have a thickness, i.e. the smallest dimension, in the range 300 to 1000 pm, such as 350 to 850 pm, such as 400 to 800 pm, such as 450 to 650 pm.

[0231] The product may have a Bendtsen roughness in the range of 50 to 4000 ml / min, such as 75 to 2000 ml / min, such as 100 to 1000 ml / min, such as 200 to 500 ml / min.

[0232] The product may have a tensile strength index in the range of 10 to 65 Nm / g, such as 20 to 60 Nm / g, such as 30 to 55 Nm / g in the machine and cross directions.

[0233] The product may have a modulus of elasticity in the range of 2 to 8 GPA, such as 3 to 6 GPA, such as 3.5 to 5.5 GPA in the machine and cross directions.

[0234] The product may have a bending stiffness (Taber 15°) in the range of 8 to 80 mNm, such as 10 to 50 mNm, such as 11 to 40 mNm, such as 15 to 30 mNm in the machine and cross directions.

[0235] The moulded multi-layered fibrous product typically comprises at least one surface that is heat-sealable, for example to PE, bio-PE, PP, PET and / or PLA from at least one surface.

[0236] The moulded multi-layered fibrous product may be substantially bio-based. For example, at least 95 wt-%, such as at least 99 wt-% of the product is free from fossilbased materials.

[0237] Further exemplary product properties

[0238] In the following, we list various product properties achievable according to some embodiments of the present invention.

[0239] The moulded multi-layered fibrous product may have a grammage, according to ISO 536, in the range of 50 to 800 g / m2, such as 150 to 600 g / m2, such as 250 to 500 g / m2, such as 300 to 475 g / m2, such as 320 to 460 g / m2.

[0240] The moulded multi-layered fibrous product may have a thickness, according to ISO 534, in the range of 200 to 850 pm, such as 300 to 750 pm, such as 350 to 700 pm, such as 400 to 600 pm, such as 450 to 550 pm.

[0241] The moulded multi-layered fibrous product may have a Bendtsen roughness, according to SCAN-P 84:1, DIN53108, in the range 50 to 5000 ml / min, such as 100 to 4000 ml / min, such as 125 to 2000 ml / min, such as 150 to 1000 ml / min, such as 200 to 600 ml / min.

[0242] The moulded multi-layered fibrous product may have a density, according to ISO 534, at least 200 kg / m3, such as in the range 200 to 900 kg / m3, such as 500 to 850 kg / m3.

[0243] The moulded multi-layered fibrous product may have a tensile strength index, according to ISO1924-2 and ISO1924-3, in the range of 15 to 65 Nm / g, such as 20 to 55 Nm / g, such as 25 to 50 Nm / g, such as 30 to 45 Nm / g.

[0244] The moulded multi-layered fibrous product may have a modulus of elasticity in the range 2 to 8 GPa, such as 2.5 to 7 GPa, such as 3 to 6 GPa , such as 3.5 to 5.5 GPa.

[0245] The moulded multi-layered fibrous product may have a bending stiffness (Taber 15°), according to DIN-53121 (Bending stiffness) and TAPPI T 489 (Bending resistance), in the range 5 to 60 mNm, such as 10 to 55 mNm, such as 15 to 50 mNm, such as 20 to 45 mNm, such as 25 to 40 mNm.

[0246] The moulded multi-layered fibrous product may have a rigidity, force at 0.5 inch bending according to Paper Plate Rigidity Testing (FPI) (samples 4 h 23 °C, 50 % RH, force lOkN + 500 N with Zwick / Roell Z010 instrument) in the range 1.0 to 6.0 N, such as 1.5 to 5.5 N, such as 2.0 to 5.0 N, such as 2.5 to 4.5 N.

[0247] The moulded multi-layered fibrous product may have a rigidity, maximum force according to Paper Plate Rigidity Testing (FPI) (samples 4 h 23 °C, 50 % RH, force lOkN + 500 N with Zwick / Roell Z010 instrument) in the range of 1.0 to 8.0 N, such as 2.5 to 7.0 N, such as 3.5 to 6.0 N, such as 4.0 to 6.5 N.

[0248] The moulded multi-layered fibrous product may have the energy (the loss of energy divided by the surface area, J / m2) needed to delaminate the structure, according to Scott-Bond ISO 16260, in the range of 50 to 300 J / m2, such as 100 to 200 J / m2, such as 115 to 160 J / m2, such as 120 to 145 J / m2, such as 125 to 140 J / m2.

[0249] The moulded multi-layered fibrous product may have an air permeance, according to SCAN-P 26:78, of at least 20 Gurley s, such as at least 50 Gurley s, such as at least 100 Gurley s, such as at least 500 Gurley s, or in the range 5 to 1000 Gurley s, such as 10 to 500 Gurley s.

[0250] The moulded multi-layered fibrous product may have a 300 s water Cobb value, according to ISO 535, of less than 120 g / m2, such as in the range 15 to 100 g / m2, such as 15 to 60 g / m2, such as 15 to 40 g / m2.

[0251] The moulded multi-layered fibrous product may have a water contact angle of at least 70°, such as at least 80°, such as at least 85°, such as at least 95°, such as at least 105°, such as at least 115°.

[0252] The moulded multi-layered fibrous product may have a 60 s olive oil Cobb value in the range of 1 to 120 g / m2, such as 2 to 50 g / m2, such as 5 to 40 g / m2, such as 10 to 30 g / m2, as determined according to ISO 535.

[0253] The moulded multi-layered fibrous product may have an oil and grease resistance, according to ASTM Fl 19-82 with olive oil at 40 °C, of at least 10 min, such as at least 20 min, such as at least 6 h, such as at least 36 h, such as at least 7 days.

[0254] The moulded multi-layered fibrous product may have a total surface free energy at least 10 mN / m, such as at least 15 mN / m, such as at least 20 mN / m, such as at least 25 mN / m, such as at least 30 mN / m, such as at least 35 mN / m.

[0255] The moulded multi-layered fibrous product may have a polar surface free energy of less than 10 mN / m, such as less than 8 mN / m, such as less than 6 mN / m, such as less than 4 mN / m, such as less than 1 mN / m .

[0256] The moulded multi-layered fibrous product may have a disperse surface free energy of at least 10 mN / m, such as at least 15 mN / m, such as at least 20 mN / m, such as at least 25 mN / m, such as at least 30 mN / m, such as at least 35 mN / m.

[0257] The moulded multi-layered fibrous product may have a water vapour transmission rate, according to ISO 2528, ASTM E96 in standard conditions 23°C, 50% RH, of less than 500 g / m2 / 24h, such as 150 to 500 g / m2 / 24h, or 40 to 150 g / m2 / 24h, or 10 to 40 g / m2 / 24h, or less than 10 g / m2 / 24h.

[0258] The moulded multi-layered fibrous product may have a water vapour transmission rate, according to ISO 2528, ASTM E96 in standard conditions 38°C, 90% RH, of less than 2500 g / m2 / 24h, such as 750 to 2500 g / m2 / 24h, or 200 to 750 g / m2 / 24h, or 50 to 200 g / m2 / 24h, or less than 50 g / m2 / 24h.

[0259] The cellulosic fibres of the lowermost fibrous layer and / or the inner fibrous layers may have an average fibre length Lc(l), analyzed with Valmet Fiber Image Analyzer (Valmet FS5), in the range of 0.6 to 2.3 mm, such as 0.8 to 1.6 mm, such as 1.2 to 1.4 mm and / or an average fibre width in the range 10 to 40 pm, such as 15 to 35 pm, such as 20 to 30 pm, such as 22 to 28 pm.

[0260] The pulp for the lowermost fibrous layer of the moulded multi-layered fibrous product may have a water retention value according to ISO 23714:2014. in the range 0.8 to 3.5 g / g, such as 1.0 to 2.0 g / g, such as 1.25 to 1.65 g / g.

[0261] The pulp for the uppermost fibrous layer of the moulded multi-layered fibrous product may have a water retention value according to 180 23714:2014, in the range 0.8 to 3.5 g / g, such as 1.1 to 3.4 g / g, such as 1.2 to 3.0 g / g, such as 1.6 to 2.8 g / g.

[0262] In the moulded multi-layered fibrous product, the standard deviation of the basis weight, according to ISO 536, may be in the range 1 to 45 g / m2, such as 2 to 35 g / m2, such as 3 to 25 g / m2, such as 4 to 20 g / m2, or less than 18 g / m2.

[0263] The moulded multi-layered fibrous product, for example an inner layer thereof, may have an ISO brightness, according to ISO 2470-2, of at least 60%, such as at least 65%, such as at least 75%, such as at least 80%, such as at least 82%. The other layers may have an ISO brightness of at least 80%.

[0264] The fibrous composition containing CTMP and / or BCTMP may have a Canadian Standard Freeness (CSF) in the range 400 to 800, such as 440 to 570, such as 470 to 540.

[0265] The fibrous composition for the uppermost fibrous layer, typically containing bleached chemical pulp, may have a Canadian Standard Freeness (CSF) in the range 0 to 750, such as 10 to 600, such as 50 to 500, such as 100 to 400, such as 150 to 350.

[0266] The fibrous composition for the lowermost fibrous layer, typically containing bleached chemical pulp, may have a Canadian Standard Freeness (CSF) in the range 100 to 800, such as 200 to 750, such as 300 to 700, such as 400 to 600, such as 450 to 550.

[0267] The moulded multi-layered fibrous product may have an SDS surfactant residue, as measured by LCK 432 test for anionic surfactants (ISO 7875-1), in the range 0 to 1000 mg / m2, such as 20 to 800 mg / m2, such as 50 to 700 mg / m2, such as 75 to 600 mg / m2, such as 200 to 450 mg / m2.

[0268] The moulded multi-layered fibrous product may comprise less than 5 mg / g, such as less than 2 mg / g, such as less than 1 mg / g of AKD which is not chemically bound, for example by ester bonds, to cellulose in the fibres. The amount of unreacted AKD may be analyzed with gas chromatography (initial temperature 210 °C 1 min, temperatureincrease 5 °C / min and end temperature is 300 °C) and soxhlet extraction equipment 6 hours 90 °C.

[0269] The moulded multi-layered fibrous product may have the following recyclability, according to CEPI recyclability laboratory test method version 2, October 2022: yield score in the range of 90 to 100% (poses no repulpability issues in the standard mill) and visual impurities Level 1 (poses no visual quality issues) and sheet adhesion Level 1 (poses no adhesion issues).

[0270] FIGURE 1 schematically illustrates a multi-layered fibrous product in accordance with at least some embodiments of the present invention. The product comprises a first fibrous layer 101, which is the uppermost fibrous layer, a second fibrous layer 102, which is the lowermost fibrous layer, and an inner fibrous layer 103 between the first fibrous layer 101 and the second fibrous layer 102.

[0271] Examples

[0272] We prepared moulded three-layered fibre products by a foam forming method. Starch and various additives (AKD, PAE, MFC) were added to the fibrous composition for the middle layer.

[0273] Example 1 : Adding starch before additives (samples A and C)

[0274] The fibrous composition (fibre stock) for the middle layer comprised BCTMP and was adjusted to the desired consistency and a pH between 8.5 and 9.5. Dry powdered starch was added to the fibrous composition and the consistency after the addition of the dry starch was 1.6%. The ratio was 7.2 wt-% dry powdered starch and 92.8 wt-% dry BCTMP fibres. PAE was added to the fibrous composition and mixed at high shear for 5 minutes. Next, AKD was added to the fibrous composition and mixed at high shear for 5 minutes. Finally, SDS surfactant was added to the fibrous composition and mixed at high shear for 5 minutes to generate a foam in the target range of 300-400 g / 1 foam density. The temperature of the fibrous composition and the subsequent foam was 30 °C. The fibrous compositions for the top and bottom layers were the same for the reference and all samples and comprised chemical pulp, AKD and PAE and were free from starch. A three-layered moulded fibrous product was prepared from the three fibrous compositions by foam forming in a mould, dewatering and hot pressing.

[0275] Example 2: Adding starch after additives (sample B)

[0276] The fibrous composition (fibre stock) for the middle layer comprised BCTMP and was adjusted to the desired consistency and a pH between 7 and 8. PAE was added to the fibrous composition and mixed at high shear for 5 minutes. Next, AKD was added to the fibrous composition and mixed at high shear for 5 minutes. Next, dry powdered starch was added to the fibrous composition. The consistency after the addition of the dry starch was 1.6%. The ratio was 7.2 wt-% dry powdered starch and 92.8 wt-% dry BCTMP fibres. Finally, SDS surfactant was added to the fibrous composition and mixed at high shear for 5 minutes to generate a foam in the target range of 300-400 g / 1 foam density. The temperature of the fibrous composition and the subsequent foam was 30 °C. The fibrous compositions for the top and bottom layers were the same for the reference and all samples and comprised chemical pulp, AKD and PAE and were free from starch. A three-layered moulded fibrous product was prepared from the three fibrous compositions by foam forming in a mould, dewatering and hot pressing.

[0277] Table 1 presents properties of the foamed composition for the middle layer.

[0278] Table 1 : Properties of the foamed composition for the middle layer.

[0279] It was observed that foam stability was increased and turbidity was decreasedas a result of adding starch to the fibrous composition.

[0280] Tables 2 and 3 present properties of the obtained three-layered moulded products.

[0281] Cobb values were determined either with water or with olive oil. The measurement was otherwise performed according to ISO 535 but the amount of liquid in the cylinder was 10 ml, and it was poured on an area of 10 cm2.

[0282] Water contact angles were measured with KRUSS Mobile Surface Analyzer, with a measurement time of 0.1 seconds.

[0283] Measurements were carried out in standard conditions according to ISO 187.

[0284] Table 2: Properties of the three-layered moulded product.

[0285] Table 3. Properties of the three-layered moulded product.

[0286] It was observed that barrier properties of the product were improved as a result of adding starch to the fibrous composition, presumably due to improved retention and sizing.

[0287] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0288] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment.

[0289] As used herein, a plurality of items, structural elements, compositional elements, and / or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and examples of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0290] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practised without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0291] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementationcan be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0292] The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.INDUSTRIAL APPLICABILITY

[0293] The present invention is industrially applicable at least in the manufacturing of moulded fibrous products.ACRONYMS LISTSDS sodium dodecyl sulphatePVA polyvinyl alcoholAKD alkyl ketene dimerPAE polyamide-epichlorohydrinMFC micro fibrillated celluloseAPG alkyl polyglycosideCTMP chemi-thermomechanical pulpBCTMP bleached chemi-thermomechanical pulpREFERENCE SIGNS LIST101 first fibrous layer102 second fibrous layer103 inner fibrous layer

Claims

CLAIMS:

1. A method comprising:- providing a first fibrous composition and a second fibrous composition and one or more further fibrous compositions, each comprising independently from each other cellulosic fibres and water, wherein at least one of the further fibrous compositions further comprises starch or a starch derivative;- in a mould, forming and dewatering the first fibrous composition, the second fibrous composition and the one or more further fibrous compositions to obtain a first fibrous layer, a second fibrous layer and, between them, one or more inner fibrous layers, respectively, in a stacked configuration, whereby at least one of the inner fibrous layers comprises starch or a starch derivative; and- hot pressing the stack comprising the first fibrous layer, the second fibrous layer and, between them, the one or more inner fibrous layers, to obtain a moulded multilayered fibrous product.

2. The method according to any of the preceding claims, wherein said at least one of the further fibrous compositions comprises at least 1 wt-%, such as at least 2 wt-%, for example 3 to 10 wt-% of starch or a starch derivative, calculated from the total dry weight of fibres.

3. The method according to any of the preceding claims, wherein all inner fibrous layers comprise starch or a starch derivative.

4. The method according to any of the preceding claims, wherein the first fibrous composition and the second fibrous composition are substantially free from starch and starch derivatives.

5. The method according to any of the preceding claims, wherein during the hot pressing, heat is applied from both sides of the stack.

6. The method according to any of the preceding claims, whereinduring the hot pressing, heat is applied only from one side of the stack, or one side of the stack is exposed to a higher temperature than the other side, and the outermost fibrous layer on said one side of the stack is substantially free from starch and starch derivatives.

7. The method according to any of the preceding claims, wherein the hot pressing comprises pressing the stack between two shaped pressing plates, of which at least one, preferably both, has a temperature of at least 150 °C, such as 150 to 270 °C, such as 180 to 250 °C, such as 190 to 225 °C.

8. The method according to any of the preceding claims, wherein as a result of said hot pressing, the starch or the starch derivative becomes gelatinized.

9. The method according to any of the preceding claims, wherein the starch or the starch derivative comprises or consists of ungelatinized starch or uncooked starch or nonsolubilised starch.

10. The method according to any of the preceding claims, wherein the starch or the starch derivative has not been gelatinized before the hot pressing.

11. The method according to any of the preceding claims, wherein the starch or the starch derivative becomes gelatinized during the hot pressing.

12. The method according to any of the preceding claims, wherein the starch or the starch derivative comprises starch originating from one or more of the following: com, potato, maize, wheat, tapioca, barley, quinoa, pea, rice.

13. The method according to any of the preceding claims, wherein the starch has a high amylose content, such as at least 10 wt-%, such as at least 15 wt-%, such as at least 20 wt- %, such as at least 25 wt-%, such as at least 28 wt-%, such as at least 30%, or 15 to 35 wt- %, calculated from dry matter.

14. The method according to any of the preceding claims, wherein the starch has a degree of substitution (DS), defined as the number of substituents per glucopyranosyl unit, of at least 0.005, such as in the range of 0.005 to 1, such as 0.01 to 0.5, such as 0.02 to 0.2.

15. The method according to any of the preceding claims, wherein the starch or the starch derivative comprises unmodified starch or modified starch, such as oxidized starch, hydroxyethylated starch, cationic starch, anionic starch, grafted starch, hydrophobic starch, aldehyde starch, mechanically-modified starch, thermally modified starch, or any combination thereof.

16. The method according to any of the preceding claims, wherein the starch derivative comprises a chemically modified starch or a decomposition product of starch, such as dextrin, such as thermally modified dextrin.

17. The method according to any of the preceding claims, wherein the average particle size of the starch is 1 to 50 pm, such as 5 to 25 pm.

18. The method according to any of the preceding claims, comprising adding starch to the respective fibrous composition in the form of a solid composition, such as a powder or granules or flakes.

19. The method according to any of the preceding claims, comprising adding starch to the respective fibrous composition in the form of a dry composition comprising at least 40 wt- %, such as at least 60 wt-%, such as at least 80 wt-%, such as at least 90 wt-%, calculated from the total weight of the composition.

20. The method according to any of the preceding claims, comprising adding starch to the respective fibrous composition in the form of a water solution, in a dissolved form, the solution comprising at least 5 wt-%, such as 10 to 50 wt-% starch, calculated from the total weight of the solution.

21. The method according to any of the preceding claims, wherein at least one of the fibrous compositions comprises fibrillated fibres, such as microfibrillated cellulose (MFC), nanofibrillated cellulose (NFC), microcrystalline cellulose (MCC), nanocrystallinecellulose (NCC), cellulose microfibrils (CMF), cellulose nanofibers (CNF), cellulose nanocrystals (CNC), cellulose nanowhiskers or any combinations thereof.

22. The method according to any of the preceding claims, wherein at least one of the fibrous compositions comprises starch, a size, a retention aid and optionally microfibrillated cellulose.

23. The method according to any of the preceding claims, wherein the method comprises adding to at least one of the fibrous compositions, such as to all fibrous compositions independently from each other, a foaming agent, foaming said at least one fibrous composition, and forming said at least one foamed fibrous composition in the mould.

24. The method according to any of the preceding claims, wherein all fibrous layers of the product are foam-formed in the mould.

25. The method according to any of the preceding claims, wherein the density of the foam is in the range of 100 to 700 kg / dm3, such as 250 to 500 kg / dm3, such as 300 to 400 kg / dm3.

26. The method according to any of the preceding claims, wherein the stability of the foam is in the range 10 to 400 ml, such as 20 to 300 ml, such as 50 to 250 ml, such as 60 to 200 ml, measured as the water volume separated from the foam volume of 1 litre during 10 minutes.

27. The method according to any of the preceding claims, wherein the turbidity of the foam is in the range 0 to 550 NTU, such as 2 to 300 NTU, such as 3 to 200 NTU, such as 5 to 100 NTU.

28. The method according to any of the preceding claims, wherein each foamed fibrous composition comprises, independently from each other, at least one surface-active foaming agent, such as an anionic surfactant, a zwitterionic surfactant, a non-ionic surfactant or any combination thereof.

29. The method according to any of the preceding claims, wherein the foaming agent is selected from the following group: sodium dodecyl sulphate (SDS), alkyl polyglycosides (APG), glycinates, glucamides, polyvinyl alcohol (PVA), and any combinations thereof.

30. The method according to any of the preceding claims, wherein in each fibrous composition, independently from each other, at least 80 wt-%, such as at least 95 wt-% of the cellulosic fibres originate from perennial and / or annual plants, such as from wood, such as from wood pulp, calculated from the total dry weight of cellulosic fibres in said layer.

31. A moulded multi-layered fibrous product comprising:- a first fibrous layer;- a second fibrous layer; and- at least one fibrous inner layer between the first and the second fibrous layers, wherein each fibrous layer comprises, independently from each other, a cellulosic fibrous material; and wherein at least one of the fibrous inner layers further comprises starch or a starch derivative, wherein the moulded multi-layered fibrous product has been obtained by a method in which a moulded stack comprising said fibrous layers is hot pressed between two shaped pressing plates of which at least one is at a temperature of 150 to 270 °C.

32. The moulded multi-layered fibrous product according to claim 31, wherein the first fibrous layer and the second fibrous layer are the outermost fibrous layers of the product, and wherein the first fibrous layer and the second fibrous layer are both substantially free from starch and starch derivatives.

33. The moulded multi-layered fibrous product according to claim 31 or claim 32, wherein at least one of the fibrous inner layers comprises at least 1 wt-%, such as at least 2 wt-%, for example 3 to 10 wt-% of starch, calculated from the dry weight of fibres.

34. The moulded multi-layered fibrous product according to any of claims 31 to 33, wherein at least 50 wt-%, such as at least 80 wt-% of the total dry weight of each fibrouslayer, independently from each other, consists of cellulosic fibres originating from perennial and / or annual plants.

35. The moulded multi-layered fibrous product according to any of claims 31 to 34, wherein: the first fibrous layer, which is the uppermost fibrous layer, comprises chemical pulp, a fibrous inner layer comprises CTMP or BCTMP and additionally starch, and the second fibrous layer, which is the lowermost fibrous layer, comprises chemical pulp.

36. The moulded multi-layered fibrous product according to any of claims 31 to 35, wherein the density of the moulded multi-layered fibrous product is at least 200 kg / m3, such as in the range of 200 to 900 kg / m3, such as 500 to 850 kg / m3, calculated as dry solids weight per volume.

37. Use of the moulded multi-layered fibrous product according to any of claims 31 to 36 as a food or liquid packaging or a food or liquid serving product or as a part thereof, or in packaging, serving, storing, cooking and / or heating of food or liquid.

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