Method, molded multilayer fibrous product and use thereof

Abstract

In accordance with an example aspect of the present invention, there is provided a method comprising: forming a multi-layer foamed fiber structure from foamed fiber compositions, where each of the foamed fiber compositions comprises cellulosic fibers, water, air, and at least one blowing agent in a mold; dehydrating the foam fiber structure; the dehydrated structure is hot pressed to obtain a molded fibrous product wherein the at least one blowing agent comprises at least one surface active blowing agent and / or at least one polymeric blowing agent, and wherein the at least one foamed fibrous composition comprises a hydrophobic agent.

Description

Technical Field

[0001] The present invention relates to molded fiber products. Background Art

[0002] In the known technology for preparing molded fiber products, foam is deposited into a basin-shaped mold with a headbox. Since the molding and pressing sequences are separate, the molding and dewatering processes are slow, and the foam may be unevenly distributed within the mold. This method is mainly suitable for products such as filters or insulators. Typically, the obtained structures (e.g. egg trays) have thick walls (>500μm), are porous, and have uneven and rough surfaces. In addition, compared with water molding, foam molding leads to larger pores in the structure of the molded fiber product, which can impair the development of internal and external barrier properties of the product. In addition, due to the charged foam environment at the wet end, the compatibility of the blowing agent and the barrier additive is difficult to achieve.

[0003] Another known alternative is to use hydroforming processes to prepare molded fiber products, but these processes are only suitable for forming a single, substantially thin-walled layer at a time and can be cumbersome if more complex structures (e.g., multi-layer structures) are required. In addition, hydroformed molded fiber products generally have a non-uniform structure and, for example, flocculation formation increases significantly with increasing fiber length and furnish consistency when attempting to avoid excessive use of water.

[0004] It is well known that barrier properties are important for molded fiber products, especially in the case of food packaging. However, the microscopic roughness of the molded fiber surface obtained by the molding process and the natural hydrophilicity of the fiber pose a challenge to the development of barrier properties. To overcome this problem, large amounts of sizing chemicals are usually required in the molding process compared to similar functional products produced from, for example, folding box board.

[0005] Furthermore, the curing time of the sizing agent in the thermoforming process is significantly shorter than in the conventional dry section of a paper and board machine and overdosing of the sizing agent is not feasible.

[0006] Known technologies are not yet sufficient for producing demanding geometries, such as walls with variable or thin thickness, deep-drawn walls, edge structures and low-friction surfaces.

[0007] It is an object of the present invention to provide improved moulded fibre products, in particular fibre products obtained by a foam moulding process. Summary of the invention

[0008] The invention is defined by the features of the independent claims. Some particular embodiments are defined in the dependent claims.

[0009] According to a first aspect of the present invention, a method is provided, comprising: in a mold, forming a multilayer foam fiber structure from a foam fiber composition, wherein each foam fiber composition comprises cellulose fibers, water, air and at least one foaming agent; dehydrating the foam fiber structure; and hot pressing the dehydrated structure to obtain a molded fiber product, wherein the at least one foaming agent comprises at least one surfactant foaming agent and / or at least one polymer foaming agent, and wherein at least one foam fiber composition comprises a hydrophobic agent.

[0010] According to a second aspect of the present invention, there is provided a moulded fibre product obtained by the method of the first aspect.

[0011] According to a third aspect of the invention, there is provided the use of a product according to the second aspect as or as part of a food or liquid packaging or food or liquid serving product, or for packaging, serving, storing, preparing, cooking and / or heating food or liquids.

[0012] According to a fourth aspect of the present invention there is provided the use of a non-ionic polymer as a foaming agent and AKD as an internal sizing agent for making a moulded fibre product or a part thereof (eg a layer) by a process comprising foam moulding and subsequent hot pressing.

[0013] According to a fifth aspect of the present invention, a method is provided, comprising: forming a multi-layer foam fiber structure from a foam fiber composition in a mold, wherein each foam fiber composition comprises cellulose fibers, water, air and a foaming agent; dehydrating the foam fiber structure, for example after forming each layer; and hot pressing the dehydrated structure to obtain a molded multi-layer fiber product, wherein at least two different foaming agents are applied, wherein the at least two different foaming agents are independently selected from the group consisting of surfactant foaming agents and polymer foaming agents.

[0014] According to a sixth aspect of the present invention, there is provided a moulded multi-layer fibrous product obtained by the method of the fifth aspect, the product being preferably a food or liquid packaging or a food or liquid serving product or a part thereof.

[0015] Various embodiments of the first and fifth aspects may include one or more features from the following list: - Each layer is formed from a respective foam fiber composition. - Each foam fiber composition comprises, independently of one another, at least one surface-active blowing agent, such as an anionic surfactant, and / or at least one polymer blowing agent, such as a nonionic polymer. - At least two different blowing agents, such as at least three different blowing agents, such as at least four different blowing agents are used in the process. - At least one foam fiber composition comprises a surface active blowing agent and a polymer blowing agent. - At least two foam fiber compositions, such as at least three foam fiber compositions, comprising a surface active blowing agent and a polymer blowing agent. - At least two of the foamed fiber compositions comprise different blowing agents. - the total amount of blowing agent in each foamed fiber composition is in the range of 0.1 to 35 wt%, such as 5 to 20 wt% or such as 1 to 3 wt% or such as 0.1 to 1 wt%, calculated on the dry fiber weight in the foamed fiber composition. - The total amount of anionic surfactant in the foamed fiber composition comprising anionic surfactant is at least 0.1 wt%, such as at least 0.5 wt%, for example at least 1 wt%, such as 0.1 to 1 wt% or 1 to 5 wt%, calculated on the dry fiber weight in the foamed fiber composition. The foamed fibre composition for at least one fibre layer comprises as foaming agent at least 0.5 wt%, such as at least 1 wt%, such as at least 5 wt%, such as 5 to 35 wt% of a nonionic polymer, calculated on the dry fibre weight in the fibre composition. - the foamed fiber composition for at least one fiber layer comprises at least 0.1 wt%, such as at least 0.5 wt%, such as at least 1 wt%, such as 0.1 to 1 wt% or 1 to 5 wt% of anionic surfactant as foaming agent, calculated on the dry fiber weight in the fiber composition. - The amount of each blowing agent in the foamed fibre composition is at most 1 wt. %, calculated on the weight of dry fibres in said fibre composition. - The at least one nonionic polymer is selected from the following group: polyvinyl alcohol (PVA), polyoxyethylene lauryl ether (Brij), polyethylene glycol sorbitan monolaurate (Tween 20), PEG-6 lauramide (PEG means polyethylene glycol), alkyl polyglycosides (APG), such as alkyl polyglucoside, fatty alcohol ethoxylates, alkylphenol ethoxylates, fatty acid ethoxylates, fatty amide ethoxylates, alkyl glycosides, such as alkyl glucoside, sugar-based nonionic polymers, such as sorbitan alkanoates, sorbitan fatty acid esters (Span) and combinations thereof. - The at least one anionic surfactant is selected from the group consisting of sodium lauryl sulfate, alpha-olefin sulfonates, alkyl sulfates, alkylbenzene sulfonates, alkyl ether sulfates, taurates, isethionates, and combinations thereof. - The at least one anionic surfactant comprises or consists of sodium lauryl sulfate. - The at least one non-ionic polymer comprises or consists of PVA. The foamed fibre composition used for at least one fibre surface layer of the product comprises at least 0.5 wt%, such as at least 1 wt%, such as 1 to 50 wt% polyvinyl alcohol, calculated on the weight of dry fibres in said fibre composition. The foamed fibre composition used for at least one inner fibre layer of the product comprises at least 0.5 wt%, such as at least 1 wt%, such as 1 to 50 wt% polyvinyl alcohol, calculated on the weight of dry fibres in said fibre composition. The foam fiber composition comprises a nonionic polymer and an anionic surfactant in a molar ratio of 5:95 to 50:50, such as 10:90 to 30:70. - At least two, for example at least three, of the foamed fiber compositions further comprise a hydrophobizing agent or a sizing agent. - at least one foamed fiber composition does not contain any hydrophobizing agent or sizing agent. - The hydrophobic agent is contained at least in the last formed fiber layer. - A hydrophobic agent is contained at least in the top fibrous layer. - The hydrophobic agent is contained at least in the inner fiber layer. - All inner fiber layers of the product comprise a hydrophobic agent, preferably imparting barrier properties to the product, such as water resistance. - All fibrous layers of the product comprise a hydrophobic agent, preferably imparting barrier properties to the product, such as water resistance. - The hydrophobic agent is alkyl ketene dimer (AKD). The foamed fiber composition of at least one fiber layer comprises at least 0.1 wt%, such as 0.1 to 1 wt%, such as 0.2 to 0.8 wt%, of a hydrophobizing agent, preferably AKD, calculated on the weight of dry fibers in the fiber composition. The moulded fibre product comprises at least two fibre layers, such as 2 to 5 layers, for example exactly three fibre layers. - Each fiber layer is formed by foaming a respective foam fiber composition, and preferably each composition independently of the others comprises one or more foaming agents. - The foamed fiber composition for the top and bottom fiber layers comprises from 1 to 50% by weight of a nonionic polymer as a foaming agent, calculated on the weight of dry fibers in the fiber composition. The foamed fibre composition for the middle fibre layer or the inner fibre layer comprises from 0.1 to 5% by weight of at least one anionic surfactant, calculated on the weight of dry fibres in the fibre composition. - The foamed fiber composition for at least one fiber layer comprises a surface active blowing agent, a hydrophobic agent and a wet strength agent. - The foamed fiber composition for at least one fiber layer comprises SDS, AKD and PAE. - The foamed fiber composition for at least one fiber layer comprises SDS and AKD. - The foamed fiber composition for at least one fiber layer comprises PVA and AKD. The cellulose fibres of the top and bottom fibre layers have been refined, preferably with a Schopper-Riegler value of at least 20, such as at least 40, such as at least 50. The cellulose fibers of the top fibrous layer have been refined and have a Schopper-Riegler value of at least 40, such as at least 50. The cellulose fibers of the bottom fiber layer have been refined and have a Schopper-Riegler value of at least 20, such as 20 to 40. The obtained molded fiber product is further coated or configured to be coated with a non-fibrous barrier coating which imparts water resistance, water vapor resistance, gas resistance (e.g. oxygen resistance) and / or grease resistance. - The cellulosic fibers comprise bleached or unbleached chemical pulp and / or bleached or unbleached chemithermomechanical pulp. Each fibrous layer is formed from a respective foamed fiber composition, preferably from foamed fiber compositions having different compositions, by a foam forming process in a mold. - Each foamed fiber composition independently of one another comprises cellulose fibers, water, air and at least one foaming agent. - The foamed fiber composition for at least one fiber layer (eg the inner fiber layer) comprises a surface-active blowing agent. - The foamed fiber composition for at least one fiber layer (eg, the fiber surface layer) includes a polymer foaming agent. - The foamed fiber composition for the fiber layer (eg, the fiber surface layer) includes a surface active foaming agent and a polymer foaming agent. - At least two foamed fiber compositions contain different blowing agent selections or different blowing agent groups. - The total amount of blowing agent in each foamed fiber composition is in the range of 0.1 to 50 wt%, such as 0.1 to 20 wt%, such as 5 to 20 wt% or such as 1 to 3 wt% or such as 0.1 to 1 wt%, calculated based on the dry fiber mass in the foamed fiber composition. - The at least two blowing agents consist of two blowing agents. The at least two blowing agents consist of or comprise three blowing agents. - The at least two foaming agents comprise PVA and sodium lauryl sulfate. - The at least two blowing agents comprise polyoxyethylene lauryl ether (Brij) and sodium lauryl sulfate. - The at least two foaming agents include an anionic surfactant and two nonionic surfactants. - The foamed fiber compositions for at least the surface fiber layers, preferably for all fiber layers, each comprise an anionic surfactant and two nonionic surfactants. - The at least two foaming agents include polyoxyethylene lauryl ether (Brij), sodium lauryl sulfate and PVA. The foamed fibre composition of at least one fibre layer of the product comprises at least 10% by weight of polyvinyl alcohol, calculated on the mass of dry fibres in said fibre composition. - The foamed fiber composition of at least one fiber layer comprises a nonionic polymer and an anionic surfactant in a molar ratio of 5:95 to 50:50, such as 10:90 to 30:70. The foamed fiber composition for at least one fiber layer comprises polyoxyethylene lauryl ether and sodium lauryl sulfate in a molar ratio of 5:95 to 50:50, such as 10:90 to 30:70. - At least one of the foamed fiber compositions (preferably used for the top fiber layer) further comprises a hydrophobizing agent or a sizing agent, such as AKD. The hydrophobic agent is contained at least in the last formed layer. The foamed fiber composition for at least one fiber layer comprises at least 0.1 wt. %, such as 0.1 to 1 wt. %, such as 0.2 to 0.8 wt. %, of a hydrophobizing agent, preferably AKD, calculated on the dry fiber mass in the fiber composition. - The moulded fibre product comprises at least three fibre layers. - Either or both of the foamed fibre compositions for the top and bottom fibre layers contain from 1 to 50 wt% of a nonionic polymer as a foaming agent, calculated on the weight of dry fibres in the fibre composition. - The foamed fiber composition for the inner fiber layer comprises 0.1 to 5% by weight of anionic surfactant, calculated on the dry fiber mass in the fiber composition. - Either or both of the foamed fibre compositions for the top and bottom fibre layers comprises from 0.1 to 5 wt% of anionic surfactant, calculated on the weight of dry fibres in the fibre composition. The foamed fiber composition for the inner fiber layer comprises 1 to 50% by weight of a nonionic polymer as a foaming agent, calculated on the dry fiber mass in the fiber composition. - Cellulosic fibers consist of or contain wood pulp. - Hot pressing comprises two hot pressing steps, preferably with pulse drying. - The total duration of heat pressing (all heat pressing steps combined) is less than 2 minutes, such as less than 1 minute. - The foamed fibre composition for at least one fibre layer comprises 0.1 to 1 wt-%, such as 0.2 to 0.8 wt-%, of AKD, calculated on the dry fibre mass in said fibre composition. The molded fiber product comprises at least three fiber layers, and the foamed fiber composition for at least one fiber layer comprises SDS as a surface active blowing agent, AKD as a hydrophobic agent and PAE as a wet strength agent. -The molded fiber product comprises at least three fiber layers, the foam fiber composition for the top and bottom fiber layers comprises a non-ionic polymer as a foaming agent, the foam fiber composition for the inner fiber layer comprises an anionic surfactant as a foaming agent, and the foam fiber composition for the top fiber layer further comprises a hydrophobic agent, such as sizing, and / or the foam fiber composition for the bottom fiber layer further comprises a hydrophobic agent, such as sizing. The molded fiber product comprises at least three fiber layers, the foam fiber composition for the top and bottom fiber layers comprises an anionic surfactant as a foaming agent, the foam fiber composition for the inner fiber layer comprises a nonionic polymer as a foaming agent, and the foam fiber composition for the inner fiber layer further comprises a hydrophobic agent, such as a size. - The foamed fibre composition for at least one fibre layer comprises a nonionic surfactant, such as glucose amide, optionally in combination with an anionic surfactant, such as SDS. - at least two foam fiber compositions independently of each other comprise a nonionic surfactant, optionally in combination with an anionic surfactant.

[0016] Various embodiments of the second or sixth aspects may include one or more features from the following bulleted list: - The product comprises at least two fiber layers, for example 2 to 5 layers. -The product is a three-dimensional molded product. -The product includes curved or non-planar surfaces. - The dry weight of each fiber layer is between 30 and 700 g / m 2 within the range. The Schopper-Riegler number of the cellulose fibres of the inner fibre layer or layers of the product is less than 50, for example less than 30. The cellulose fibres of the top and / or bottom fibre layer of the product have a Schopper-Riegler number of at least 20, such as at least 40, such as at least 50. The Schopper-Riegler number of the cellulose fibres of the bottom fibre layer of the product is at least 20, for example 20 to 40. The cellulose fibres of the top fibrous layer of the product have a Schopper-Riegler number of at least 40, such as at least 50. - The product is a food or liquid packaging or a food or liquid serving product or a part thereof, and preferably at least the top fibrous layer arranged to be in contact with the food or liquid comprises a hydrophobic agent to impart barrier properties. - The product is a thin-walled moulded fibre product obtained by a foam moulding process, preferably with a variable or substantially constant thickness of less than 2 mm. - Products are configured such that surfaces that come into contact with food or liquids exhibit water repellency and / or oil and grease repellency. - The product is configured such that the surface that comes into contact with food or liquids is coated or configured to be coated with a non-fibrous barrier coating. - The non-fibrous barrier coating provides or enhances the water, water vapour, gas (eg oxygen) and / or grease resistance of the surface. - The product has a thickness in the range of 300 to 1000 μm, such as 300 to 700 μm, such as 450 to 900 μm. - The product has a Bendtsen smoothness in the range of 50 to 4000 ml / min, for example 100 to 1000 ml / min. - The tensile index of the product in the machine direction and the transverse direction ranges from 25 to 60 Nm / g. -The elastic modulus of the product in the machine direction and transverse direction ranges from 3.0 to 6.5 GPA. The product has a bending stiffness (Taber 15°) in the machine and transverse directions in the range of 40 to 80 mNm. - The product is heat-sealable with or can be heat-sealable with a thermoplastic material, such as a thermoplastic packaging material. the cellulose fibers of the inner fibrous layer or layers of the product have a Schopper-Riegler number of less than 30, the cellulose fibers of the bottom fibrous layer of the product have a Schopper-Riegler number of 20 to 40, and the cellulose fibers of the top fibrous layer of the product have a Schopper-Riegler number of at least 40.

[0017] Advantages of the present invention

[0018] The present invention can provide an improved internal sizing method for molded fibrous products, particularly multi-layer foam-formed molded fibrous products.

[0019] In particular, the present invention may be advantageous in situations where molded fiber products require coating (e.g., by a water-based barrier coating). Such coated products include, for example, barrier-coated food packaging. Some embodiments provide an effective method for adequate internal sizing of such products.

[0020] Some embodiments may optimize the location of sizing chemicals within a multi-layer molded fiber product.

[0021] In the case of molded fiber product surface modification (e.g., dispersion of barrier coatings), wettability of the molded fiber surface may be critical, and excessive hydrophobic structure due to internal sizing may prevent coating film formation.

[0022] Some embodiments may utilize thermoplastic materials to enhance heat sealing performance.

[0023] In some embodiments, by optimizing foaming, sizing, and additive chemicals separately in each foam layer, for example by using higher loadings of sizing and additive chemicals in the inner layer (e.g., the middle layer), a combination of internal and external barriers can be achieved, thereby providing high functionality in the molded fiber product.

[0024] In some embodiments, the properties of the molded final product can be better customized and controlled because each layer can carry a different set of foaming agents and hydrophobic agents in combination with the cellulose fibers. Specifically, the hydrophobicity and related barrier effects can be limited to the desired portion / layer of the product, while the choice of surfactant in each layer can also be varied to be compatible with the presence or absence of the hydrophobic agent in that layer. Therefore, the present invention can better control and customize the properties of the foamed molded article, especially the barrier properties, while maintaining good foaming properties of the ingredients.

[0025] The present invention can avoid the need for a separate non-fibrous barrier coating. Problems associated with coating adhesion can be avoided.

[0026] The present invention avoids the need for a separate plastic barrier coating.

[0027] The present invention can rapidly prepare multi-layer molded fiber products. The cycle time can be shorter. Wetting or rewetting of the product due to a separate coating step can be avoided.

[0028] The present invention allows for easy customization of the properties of each layer.

[0029] In the product of the invention, the distribution of cellulose fibers may be more uniform.

[0030] In the present invention, fiber flocculation and cloudy appearance can be avoided or reduced.

[0031] The present invention may provide a biodegradable, compostable and recyclable multi-layer molded fiber product suitable for food contact, such as an ovenable and / or micro-bakeable product.

[0032] The present invention can reduce energy consumption because the need for dehydration and drying of the product is reduced, especially when foam forming is used.

[0033] The present invention can reduce production costs associated with cycle time, dehydration, drying and chemicals. Chemical retention can be enhanced, especially when using foam molding.

[0034] The present invention can provide a fiber product with good internal barrier properties.

[0035] The present invention can provide fiber products with complex geometric shapes without creases and cracks.

[0036] The invention may be advantageous in the production of demanding geometries, such as walls of variable thickness or thin walls, deep drawn walls, edge structures and low friction surfaces.

[0037] The present invention may provide plastic-free fiber packaging that is recyclable in existing fiber recycling infrastructure.

[0038] The present invention may provide a biodegradable and / or compostable product.

[0039] The present invention can replace existing packaging solutions, which are usually based on plastics. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 schematically illustrates a multi-layer fiber product according to at least some embodiments of the present invention;

[0041] Figures 2 to 4 Stereomicroscope images of the fiber structures are shown;

[0042] Figure 5 A flow chart is shown showing process steps for making a multi-layer foam molded product according to at least some embodiments of the present invention; and

[0043] Figure 6 Foam forming of a three-layer fiber structure according to at least some embodiments of the present invention is shown. Example

[0044] definition

[0045] Unless otherwise stated herein or clear from the context, any percentages mentioned herein are expressed as weight percentages based on the total dry weight of the corresponding composition.

[0046] The amount of additives is usually expressed as a weight percentage, calculated on the basis of the dry fiber weight in the respective composition.

[0047] As used herein, the term "hot pressing" generally refers to a process in which increased pressure and increased temperature are applied over a period of time. Hot pressing may involve several consecutive cycles or steps of applying increased pressure and temperature. In some cases, hot pressing may involve applying sub-atmospheric pressure. Typically, the purpose of the hot pressing step is to obtain a strong and dimensionally stable product with a smooth product surface.

[0048] In the present context, the term "molded product" refers to a product obtained by forming or giving shape to a product in a closed or closable cavity of a mold. Usually, "molding" does not mean simply pressing a product between two plates.

[0049] In the present context, the term "cellulosic fiber material" may refer to a material comprising cellulose and / or lignocellulosic fibers.

[0050] Generally, the term "top fiber layer" or "uppermost fiber layer" refers to the fiber surface layer that is closest to or in contact with the contents of the package (eg, food).

[0051] Generally, the term "bottom fiber layer" or "lowest fiber layer" refers to a fiber surface layer located on the opposite side of the fiber structure relative to the top fiber layer.

[0052] Typically, the term "surface active foaming agent" refers to surfactants.

[0053] This product is usually a three-dimensional molded single-layer or multi-layer fiber product obtained using a foam molding process.

[0054] We have observed that specific combinations of additives are advantageous when preparing molded fiber products by foam molding. The additives are typically added to the fiber slurry, for example before or after foaming the fiber slush, or before or after adding the foaming composition to the fiber slush. In yet another embodiment, the additives are added to the structure after the foam molding step but before the hot pressing step.

[0055] Specifically, we have observed that specific combinations of blowing agents (e.g., surfactants) and additives (e.g., retention aids, fixatives, and wet strength agents) in addition to the size can be used to successfully internally size foamed molded fiber products (typically using a hydrophobic size).

[0056] Furthermore, we have observed that advantages can be gained by using multiple foaming chemistries in the manufacture of foam-formed multi-layer fiber products. Each layer of such a product can be manufactured with an optimized combination of foaming chemicals and optional other additives.

[0057] At least one layer of the product is a fibrous layer comprising cellulosic fiber material.

[0058] Cellulose fiber materials

[0059] The cellulosic fiber material may include wood pulp, such as hardwood pulp and / or softwood pulp.

[0060] Softwood pulp can be made from spruce or pine, or a mixture of these.

[0061] Hardwood pulp may be made from birch, poplar, aspen, alder, maple, eucalyptus tropical hardwoods or mixtures thereof.

[0062] The wood pulp may be a mixture of hardwood and softwood pulp.

[0063] In one embodiment, the cellulosic fiber material may include pulp made from any annual plant, such as straw, reed, reed canary grass, bamboo, sugar cane, bagasse, or any herbaceous plant.

[0064] In one embodiment, the cellulosic fiber material comprises hardwood pulp and softwood pulp in a weight ratio ranging from 1:2 to 2:1.

[0065] The cellulosic fiber material may include wood pulp selected from the group consisting of chemical pulp, mechanical pulp, and any combination thereof.

[0066] The cellulosic fiber material may include one or more of chemical wood pulp, mechanical wood pulp (eg, chemithermomechanical pulp), fibrillated cellulose (eg, microfibrillated cellulose (MFC)), nanocellulose, and any other cellulosic material comprising cellulose fibers or cellulose fiber fractions.

[0067] MFC and nanocellulose can come from wood or non-wood sources.

[0068] Advantageously, at least one fiber layer (eg, inner layer) comprises bleached chemithermomechanical pulp (BCTMP). The BCTMP may be refined to a Canadian Standard Freeness of less than 800 ml, such as 600 to 800 ml. The BCTMP may also be unrefined.

[0069] The cellulosic fiber material may also include non-wood pulps, such as straw pulp.

[0070] In some embodiments, the cellulosic fiber material comprises or consists essentially of virgin wood pulp, such as virgin bleached chemical pulp that is substantially free of lignin, which makes the product particularly suitable for food contact, such as for cooking, heating, baking, and light toasting.

[0071] In one embodiment, at least 80% by weight, such as at least 95% by weight, of the cellulosic fiber material of the product consists of virgin cellulosic fibers, such as virgin wood pulp.

[0072] The advantage of virgin pulp is that it does not contain pigments and other unwanted chemicals. Recycled waste materials often contain chemical and microbial contaminants, which may affect their safe use. Mixtures of chemical compounds and microbial products may seep out of recycled materials and cause various negative health or environmental effects. 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 the use of recycled materials.

[0073] In some embodiments, recycled materials may be used.

[0074] An advantage of chemical pulp (eg bleached chemical pulp) is that it is substantially free of lignin. Another advantage of chemical pulp is that the interfiber bonding in the final product may be better than that of mechanical pulp.

[0075] Pulps containing lignin are often not of sufficient organoleptic quality for direct food contact. In addition, pulps containing lignin are very sensitive to aging and yellowing of the material.

[0076] Foam molding

[0077] Advantageously, one or more fiber layers of the product are obtained by a foam forming process.

[0078] The multilayer product is preferably obtained in such a way that all the fibers to be included in the final structure undergo a foaming process. In some embodiments, all the fibers to be included in the layer exhibiting barrier properties undergo a foaming process.

[0079] For example, at least the fiber layer showing barrier properties has been obtained by a foam forming process in a mold. Such a fiber barrier layer can be any fiber layer, such as the uppermost fiber layer, the lowermost fiber layer and / or one or more inner fiber layers.

[0080] The advantage of foam molding is that lighter and less bulky products can be produced. In addition, more uniform forming can be achieved. The use of foam enables the easy production of multi-layer structures in a modular process, i.e., all layers can be formed in the same mold, but each layer still has an individually tailored composition and choice of fiber raw materials and additives to form a multi-layer shape or structure in the mold, which is then hot-pressed.

[0081] An advantage of dehydrating the entire multilayer structure in the same mold is that the interlayer bonding can also be enhanced during the dehydration process compared to dehydrating each layer individually.

[0082] In some embodiments, in addition to the foam-formed layers, the final product may also include a water-formed layer. Such water-formed layers may be formed in a separate process and combined with the foam-formed layers or foam-formed multilayer structures by heat pressing. The advantage of water forming is that there are no foaming chemicals, so the function of the sizing material is not interfered with. In the water forming process, the individual layers are usually formed independently of each other and removed from the mold. A separate mold can be used. After removal from the mold, the layers can be stacked into a pile and connected to each other and / or to other layers by heat pressing.

[0083] In some embodiments, the final product may include a hydroformed layer in addition to the foam-formed layer, and all layers (i.e., the hydroformed layers and the foam-formed layers) are formed in the same mold to form a multi-layer shape or structure in the mold, which is then heat pressed.

[0084] In one embodiment, the product comprises a plurality of fibrous layers which are prepared by a hydroforming process and combined with each other and optionally with at least one foam-formed fibrous layer. Advantageously, the foam-formed layer constitutes one or more inner fibrous layers, for example a middle layer of the product, and advantageously exhibits barrier properties.

[0085] In an embodiment, the product may comprise one or more hydroformed layers and one or more foam formed layers. In an embodiment, one or more inner fiber layers have been hydroformed and the top and bottom fiber layers have been foam formed.

[0086] An advantage of the multilayer product according to some embodiments is that migration of substances can occur during molding and / or hot pressing. For example, the dosage of additives, such as the dosage of sizing, can be concentrated or increased in the last prepared and molded layer, such as the top fiber layer. During dehydration and / or hot pressing, for example, pressure and / or temperature gradients can guide the migration of substances within the multilayer structure to a desired direction.

[0087] One embodiment provides a product obtained by the following method.

[0088] In some embodiments, the product or at least one of its fiber layers can be obtained by a method comprising the following steps: providing a fiber pulp comprising fibers; refining the fibers of the fiber pulp and / or adding additives, such as barrier agents, to the fiber pulp; converting the fiber pulp into a foam composition; forming the foam composition in a mold, such as molding and pressing the foam composition; dehydrating; and hot pressing.

[0089] In some embodiments, the barrier agent or any other additive may alternatively or additionally be added at a later stage of the process, for example by applying a composition comprising the barrier agent to the fiber foam or an already formed fiber layer, preferably a foam-formed layer.

[0090] In the method, a foam composition comprising fibers, water, air and one or more blowing agents is first provided. The foam may also include fillers, additives, retention aids, fixatives, pigments, adhesives, strength agents, barrier dispersants and / or sizing agents. The foam composition is then formed in a mold.

[0091] In one embodiment, the method comprises: forming a multi-layer foam fiber structure from a foam fiber composition in a mold, wherein each foam fiber composition comprises cellulose fibers, water, air and at least one foaming agent; dehydrating the foam fiber structure; and hot pressing the dehydrated structure to obtain a molded fiber product. The at least one foaming agent comprises at least one surface active foaming agent, such as an anionic surfactant, and / or at least one polymer foaming agent, such as a nonionic polymer. Preferably, at least one foam fiber composition comprises a hydrophobic agent.

[0092] In another embodiment, the method comprises: forming a multi-layer foam fiber structure from a foam fiber composition in a mold, wherein each foam fiber composition comprises cellulose fibers, water, air and a foaming agent; dehydrating the foam fiber structure; and hot pressing the dehydrated structure to obtain a molded multi-layer fiber product, wherein at least two different foaming agents are applied. The at least two different foaming agents are independently selected from the group consisting of a surfactant foaming agent and a polymer foaming agent.

[0093] Typically, different types of foam fiber compositions are used to prepare each layer of a multi-layer product. Each foam composition may include a dedicated set of blowing agents and other additives, such as hydrophobic agents. "Different types" means having different compositions, such as different blowing agents and additives selections and / or different concentrations.

[0094] The blowing agent preferably comprises a surface active blowing agent, such as a surfactant, and / or a nonionic polymer blowing agent or a mixture thereof.

[0095] Surfactants are generally molecules with two parts: a polar or hydrophilic head group and a hydrophobic tail.

[0096] Gemini surfactants have two polar head groups attached to a spacer and can be anionic, nonionic, cationic or zwitterionic.

[0097] In one embodiment, the surfactant comprises a gemini surfactant.

[0098] In one embodiment, the surfactant is cleavable, for example at a specific pH or enzymatically. If desired, the foaming properties of such cleavable surfactants can be eliminated by cleavage at a later stage of the production process, for example in the water cycle.

[0099] In one embodiment, the surfactant is at least partially, preferably completely, synthesized from renewable raw materials.The surfactant may be at least partially bio-based, such as 100% (completely) bio-based.

[0100] The surfactant may include a zwitterionic surfactant selected from the group consisting of betaines, amidobetaines, imidazolines, amide oxides, and combinations thereof. The advantages of these surfactants are that they are broadly compatible with other classes of surfactants and are generally stable at different pHs.

[0101] One or more foaming agents may be used independently in each fiber layer.

[0102] Surfactants can be nonionic, anionic, cationic or amphoteric.

[0103] Surfactants used in foam formation may have anionic, nonionic, cationic or zwitterionic polar head groups.

[0104] The surfactant may have a hydrocarbon tail, which may be linear, branched or double-tailed.

[0105] For foam forming, hydrophilic surfactants with linear or double chain tails are preferred.

[0106] In one embodiment, at least one anionic surfactant is used.

[0107] In one embodiment, at least one non-ionic polymer is used.

[0108] In one embodiment, at least one anionic surfactant and at least one nonionic polymer are used as foaming agents, particularly for improving foaming. For example, the anionic surfactant may be sodium dodecyl sulfate (SDS), and the nonionic polymer may be polyoxyethylene (23) lauryl ether or polyoxyethylene sorbitan fatty acid esters and sorbitan esters.

[0109] In one embodiment, at least one hydrophilic surfactant and at least one lipophilic or hydrophobic foaming agent are used as foaming agents. For example, the hydrophilic surfactant can be Tween, which is a nonionic hydrophilic surfactant, and the lipophilic foaming agent can be a sorbitol-based foaming agent.

[0110] A suitable amount of anionic surfactant is 0.2 to 5 g / L (grams per liter of fiber raw material).

[0111] Suitable amounts of anionic surfactants are from 1 to 20% by weight based on dry fiber.

[0112] The anionic surfactant may be selected from the group consisting of sodium dodecyl sulfate (SDS), α-olefin sulfonates, alkyl sulfates, alkylbenzene sulfonates, alkyl ether sulfates, taurates, isethionates, and combinations thereof.

[0113] Examples of nonionic foaming chemicals include nonionic polymer foaming chemicals such as polyvinyl alcohol.

[0114] The nonionic polymer can be selected from the following group: polyvinyl alcohol (PVA), polyoxyethylene lauryl ether (Brij), polyethylene glycol sorbitan monolaurate (Tween 20), PEG-6 lauramide, alkyl polyglycosides (APG), such as alkyl polyglucoside, fatty alcohol ethoxylates, alkylphenol ethoxylates, fatty acid ethoxylates, fatty amide ethoxylates, alkyl glycosides, such as alkyl glucoside, sugar-based nonionic polymers, such as sorbitan alkanoate, and combinations thereof.

[0115] In some embodiments, the at least one foaming agent may be selected from anionic surfactants and nonionic surfactants.

[0116] In an embodiment, the foam fiber composition for at least one fiber layer includes an anionic surfactant, such as SDS, and a nonionic surfactant, such as glucamide.

[0117] In one embodiment, the foam fiber composition used in at least one fiber layer includes SDS and glucamide.

[0118] In one embodiment, the foam fiber composition for at least one fiber layer includes SDS and alkyl polyglycoside (APG).

[0119] In some embodiments, the at least one foaming agent may be selected from the group consisting of SDS, alkyl polyglycoside (APG), glycinate, glucamide, and any combination thereof.

[0120] In the present process, blowing agents such as surfactants and more generally additives may be arranged for recycling.

[0121] Typically, the size (diameter) of the bubbles in the foam is about 10 to 300 μm, such as 50 to 250 μm, typically about 100 to 150 μm.

[0122] In one embodiment, a composition suitable for foaming is obtained by mixing a fiber slurry (fiber raw material) having a consistency of about 0.5 to 7% (relationship between the amount of fiber and the weight of the slurry) with a foam formed by water and a foaming agent, wherein the air content of the foam is about 10 to 90% (volume), such as 20 to 80%, such as 50 to 70% (volume), in which case the fiber content of the resulting foamed fiber slurry is about 0.1 to 3% (weight).

[0123] In one embodiment, instead of mixing the fiber slurry with pre-generated foam, a foaming agent may be added to the fiber slurry and the mixture is then foamed to obtain a foamed fiber slurry. The mixture to be foamed typically has a consistency in the range of 0.5 to 3%, such as 1.0 to 2.5%.

[0124] For example, a fiber slurry having a consistency of 0.5 to 7%, such as 1 to 3%, is first provided. Optionally, the pH of the fiber slurry is adjusted to above 7, such as 7 to 9. Thereafter, at least one foaming agent and optional additives (such as a wet strength agent) are added to the fiber slurry. For example, a wet strength agent (such as PAE) may be added first, followed by a foaming agent (such as a surfactant). The fiber slurry is then foamed, after which other additives, typically a hydrophobic agent and / or a wet strength agent, may be added to the foamed mixture.

[0125] Fibers may include all types of fibers from chemical and / or mechanical pulping, recycled fibers, waste fibers, agricultural waste streams, annual plant fibers, by-products, woody or non-woody micro- or nanofibrillated cellulose fibers, regenerated cellulose fibers, and combinations thereof.

[0126] In one embodiment, a molded multi-layer fibrous product is obtained by forming a molded multi-layer foam structure from at least one foamed fibrous composition, the foamed fibrous composition comprising cellulose fibers, water, air and a foaming agent, and optionally further comprising a barrier agent and an additive; dehydrating the structure, preferably by applying a vacuum; and hot pressing the dehydrated structure to obtain a molded multi-layer fibrous product. At least one fiber layer of the multi-layer fibrous product may exhibit barrier properties throughout its structure.

[0127] In the present context, "forming", typically foam forming, refers to the process of giving a foam composition a shape (eg, a three-dimensional shape) in a mold.

[0128] In a preferred method, the foam fiber composition is fed into a mold, typically into a cavity in the mold. The mold typically includes a cavity or interior space defined by the inner surface of the mold. The fed foam composition is formed in the cavity. In the closed configuration of the mold, the size (e.g., the shortest dimension) of the cavity may be in the range of 0.1 to 100 mm, such as 3 to 100 mm, such as 5 to 60 mm.

[0129] The shortest or smallest dimension generally refers to the thickness of the product or layer to be molded.

[0130] The foam composition can be fed into the mold to provide a certain amount of foam composition, such as a layer of foam composition, on at least one inner surface of the mold. The layer is usually non-planar and can be understood as the thickness of the foam composition located on the inner surface of the mold and conforming to the shape of the surface, such as a variable thickness or a substantially constant thickness.

[0131] Typically, the shaping step comprises pressing the fiber composition into the interior space of the mold by bringing the parts of the mold closer to each other.

[0132] The step of forming the multilayer foam structure may comprise feeding a first fiber composition in foam form into a mold and shaping the first fiber composition in the mold to produce a first foam fiber layer. Thereafter, without removing the first fiber layer from the mold, the process is continued by feeding a second fiber composition in foam form into the mold and shaping the second fiber composition in the mold to produce a second foam fiber layer. As a result, a two-layer molded foam structure is obtained in the mold. The process may be continued to add further fiber layers to the molded foam structure.

[0133] The first fiber composition and the second fiber composition may differ from each other, for example in terms of foaming agents and additives, such as barrier agents or hydrophobic agents, or in terms of the cellulose fibers.

[0134] If not otherwise specified, "components of the mold" refer to the components of the mold that are used to define the interior space and thus help shape the foamed fiber composition.

[0135] The second foam fiber layer can be supplied so as to be located on top of or below the first foam fiber layer in the mold. In addition, the supply step can be carried out in any order: the first layer or the second layer can be formed in the mold first.

[0136] For example, when preparing a multi-layer molded foam structure, the layers may be formed in any suitable order. The inner (to be) fiber layer may be formed first, and then the top and bottom fiber layers may be formed on both sides of the inner fiber layer. Alternatively, the top (to be) fiber layer or the bottom (to be) fiber layer may be formed first, and then the other fiber layers may be formed.

[0137] It is also conceivable to obtain the product by preparing the first and second foamed fiber layers using separate molds, and to connect the first and second fiber layers obtained during the hot pressing step.

[0138] In an embodiment, the feeding into the mold comprises feeding the foam fiber composition in foam form into an inner space or inner volume of the mold, wherein the inner space is bounded by an inner surface of the mold.

[0139] Preferably a vacuum can be applied during the dehydration step.

[0140] The final multilayer foam structure is removed from the mold by opening the mold.

[0141] It is advantageous to be able to adjust the distance between the mould parts during feeding and shaping of the foam composition.

[0142] Before starting to feed another fiber composition (e.g., a second fiber composition) into the mold, it is usually necessary to expand the interior space of the mold by moving the mold parts away from each other. The volume of the interior space can be reduced or expanded to shape the foam that has been fed and to make room for the foam to be fed next.

[0143] In all adjustments to the volume of the interior space of the mold, some parts of the mold may remain stationary while other parts move.

[0144] In an example, one or more portions of the mold remain stationary while one or more other portions of the mold move during the approximating or the expanding.

[0145] For example, the mold may include two sub-molds, such as two halves, which are arranged to face each other and can move relative to each other. The sub-molds can be close to each other to form the product. The sub-molds can be moved away from each other to expand the internal space, or even moved further away to open the mold and remove the molded product from the mold.

[0146] In one example, the product can be obtained by using a mold comprising two parts, a female mold and a male mold, which can be arranged to face each other to enclose an internal space between the two parts, also called a molding space or molding cavity. The composition to be molded or formed is fed into the molding space, and the female mold and / or the male mold are approached to each other so that the composition has a shape corresponding to the shape of the molding space. "Approaching" refers to the process of reducing the internal space by moving one or both of the male and female molds.

[0147] Dehydration of the structure may be performed by applying a vacuum to the interior space of the mold containing the fed foaming composition.

[0148] The dehydration step precedes the hot pressing step, which produces a final, generally smooth and dry product in which all layers have been connected to each other.

[0149] In hot pressing, the temperature is typically above room temperature, such as at least 50°C, such as at least 100°C, such as in the range of at least 150 to 240°C.

[0150] In hot pressing, subatmospheric pressure, for example, a pressure of 600 kPa or less, may be applied.

[0151] The hot pressing may comprise two or more consecutive hot pressing steps. The total duration of the hot pressing may be less than 60 seconds, such as less than 30 seconds.

[0152] During hot pressing, heat can be applied from one side or both sides of the material to be pressed. In one embodiment, heat is applied from only one side.

[0153] For example, the hot pressing may include two hot pressing steps, wherein both hot pressing steps apply heat from the same side. Alternatively, the hot pressing may include two hot pressing steps, wherein heat is applied from different sides.

[0154] Heat pressing can help develop barrier or other functional properties, for example, through chemical reactions that occur at high temperatures, such as cross-linking and curing reactions. Therefore, heat pressing can be advantageous when using additive chemistries whose effects are enhanced by cross-linking or curing.

[0155] Heat pressing can also aid in the flow of additives, such as barrier or hydrophobic agents, within the multi-layer fiber structure.

[0156] Heat pressing can help the flow of the barrier chemical. For example, heat pressing from one side can direct the flow of the barrier chemical within the layer differently than heat pressing symmetrically from two sides.

[0157] Heat pressing preferably includes pulse drying.

[0158] Pulse drying usually involves wet pressing with applied heat. The applied heat may have two effects: it may reduce the viscous drag of the water, and it may soften the structure of the pulp, making it more compressible, thus producing a smooth surface. If the heat transfer rate is high enough, a vapor phase may be generated on the wet side in contact with the high temperature medium. This may aid the dehydration process, as the expanding vapor may displace bound water.

[0159] Additives, Barrier Properties and Sizing

[0160] At least one fiber layer may include one or more of the following additives: pigments, such as talc, clay and calcium carbonate; retention aids; fixatives; barrier agents; latex binders; water-soluble binders, starch, wet strength agents, CMC; sizing, such as AKD.

[0161] The amount of the additive may be in the range of 0.01 to 30 wt %, such as in the range of 0.01 to 10 wt %, such as in the range of 0.1 to 8 wt %, such as in the range of 1 to 5 wt %, these ranges being calculated based on the weight of the dry fibers in the fiber layer. In each individual fiber layer, the amount and the nature or function of the additive may be selected independently of one another. Preferably, the performance of the entire product may be optimized by the presence or absence of the additive in each fiber layer.

[0162] Barrier properties can be provided to any fiber layer of the product by refining the fibers and / or by adding barrier or hydrophobic or reinforcing agents and / or by selecting a suitable foaming agent. Different barrier properties can be provided to the fiber layers. For example, one fiber layer can exhibit grease resistance while another fiber layer can exhibit water resistance.

[0163] An example of a barrier additive is a sizing agent or a hydrophobic agent, which is usually used for internal sizing and / or surface sizing, preferably for internal sizing. Preferably, the sizing agent is a foamable sizing agent, such as a resin sizing agent. In one embodiment, the sizing agent is configured to not inhibit or reduce the foaming effect of the foaming chemical.

[0164] The barrier additive may be added to the fiber furnish or fiber slurry at a consistency of, for example, 0.5 to 15% (eg, 2 to 10%) before the foaming step and / or added to the foam or mixed with the fiber slurry at said consistency before the foam forming step.

[0165] The barrier additive is preferably added to the fiber furnish or fiber slurry at a consistency of less than 10%, such as less than 5%.

[0166] In an embodiment, at least one fiber layer comprises sizing.

[0167] In some embodiments, different amounts of sizing may be applied to the fiber compositions of the various layers of the multi-layer product. For example, at least before hot pressing, the fiber composition of the bottom fiber layer of the product may contain less hydrophobic agent or sizing than the fiber compositions of the other layers (particularly the top fiber layer of the product). For example, the fiber composition of the bottom fiber layer may contain 50% less sizing by weight than the fiber composition of the top fiber layer. Preferably, during hot pressing or pulse drying, part of the sizing applied to the top fiber layer will migrate to the other fiber layers.

[0168] The size can be a cationic size, anionic size and / or reactive size.

[0169] Suitable cationic sizes include cationic starch and starch derivatives and corresponding natural carbohydrate-based polymers.Synthetic polymers may be used, such as styrene / acrylate copolymers (SA), polyurethanes and alkylated urethanes.

[0170] Suitable anionic sizing materials include anionic starch and starch derivatives and corresponding carbohydrate-based natural polymers, such as carboxymethylcellulose and its salts, alkylcelluloses, such as methylcellulose and ethylcellulose. Synthetic polymers include: styrene / maleic acid copolymers (SMA), diisobutylene / maleic anhydride, styrene acrylate copolymers, acrylonitrile / acrylate copolymers, and polyurethanes and similar latex products containing the same chemical functional groups.

[0171] Nonionic starches may also be used.

[0172] In some embodiments, the size is a modified rosin, wax, oil, or polymer.

[0173] The advantage of using a glue is that the undesired absorption of liquids and / or water and / or moisture by the foamed structure can be reduced. As a result, the moisture or water resistance of the product is improved.

[0174] An example of a wax compound is alkyl ketene dimer (AKD).

[0175] AKD may be cationic AKD or anionic AKD, preferably cationic AKD.

[0176] The AKD may be in the form of a dispersion, such as an aqueous dispersion of AKD and a polymer. The polymer may be a cationically modified starch.

[0177] An example of an oil is alkenyl succinic anhydride (ASA).

[0178] An example of a polymer sizing compound is styrene acrylate emulsion (SAE).

[0179] The preferred size is AKD or similar wax.

[0180] Examples of only slightly cationic or nonionic sizings include: AKD dispersions that do not contain cationic polymers, and resin binders, such as foamable resin binders. The advantage of such sizings is that they are less likely to inhibit or reduce the foaming action of foaming chemicals, and may even enhance the foaming action of foaming chemicals.

[0181] An example of a sizing compound is a mixture of a resin binder and AKD.

[0182] For example, the size can be selected from the group consisting of AKD, ASA, rosin products and polymer and copolymer products.

[0183] In some embodiments, the size is AKD that has been stabilized or emulsified with cationic starch or other cationic polymers.

[0184] In some embodiments, the size is AKD that is not stabilized or emulsified with any cationic starch or other cationic polymer.

[0185] In some embodiments, the ultimate adverse effect of the sizing on foam stability and quality can be mitigated by selecting the appropriate foaming chemical combination and location. In particular, it is advantageous to mutually optimize the charge states or charge environments of the sizing and foaming chemicals.

[0186] For example, in the case of cationic sizes, it may be advantageous to use anionic surfactants and / or nonionic polymers as blowing agents.

[0187] As another example, in the case of a combination of cationic and nonionic sizes, it may be advantageous to use anionic surfactants as the foaming chemical.

[0188] In some embodiments, at least one fiber layer comprises a sizing agent, optionally in combination with one or more other additives. Preferably, the fiber layer further comprises PAE. PAE may be able to enhance the binding of the sizing agent, particularly AKD, to the fibers.

[0189] Typically, a hydrophobic agent, such as a size, is added to the foamed fiber composition after the foaming step.

[0190] In one embodiment, the hydrophobic agent, such as size, is added later in the process than other additives, such as blowing agents and optional retention aids.

[0191] In a multilayer product, one or more layers may be free of anionic surfactants, while one or more other layers may contain anionic surfactants. Optionally, the layer free of anionic surfactants may contain a size, such as a cationic size, and optionally also a nonionic polymer.

[0192] For example, the fibrous surface layer of the product may comprise a nonionic polymer.

[0193] For example, the inner layer of the product may be free of anionic surfactants. The inner layer may comprise a sizing material.

[0194] For example, the back layer of the product may contain anionic surfactants.

[0195] In one embodiment, at least one fiber layer comprises talc, for example 0.1 to 5 wt % talc.

[0196] In one embodiment, at least one fiber layer comprises clay, such as 0.1 to 5 wt % clay.

[0197] In an embodiment, at least one fiber layer comprises calcium carbonate, for example 0.1 to 5 wt % calcium carbonate.

[0198] In an embodiment, at least one fiber layer comprises a barrier agent selected from the group consisting of polyolefins, polyesters, other thermoplastic polymers, biodegradable polymers such as polylactic acid, starch and its derivatives, plastomers, elastomers, ethylene vinyl alcohol and any derivatives, copolymers and mixtures thereof.

[0199] In one embodiment, at least one fiber layer comprises 0.1 to 15 wt%, such as 0.1 to 10 wt%, such as 0.1 to 5 wt% of a barrier agent, such as a dispersed polymer barrier agent. Such barrier agents generally provide the barrier properties throughout the fiber layer structure, especially without any refining.

[0200] In one embodiment, at least one fiber layer comprises 0.1 to 5 wt % of a polymer latex binder, such as styrene butadiene latex, styrene acrylate latex, polyvinyl acetate latex.

[0201] In one embodiment, at least one fiber layer comprises 0.1 to 25 wt %, such as 5 to 15 wt %, of polyvinyl alcohol (PVA).

[0202] In an embodiment, at least one fiber layer comprises 0.1 to 20 wt %, such as 0.1 to 5 wt %, of starch.

[0203] The starch may be native, modified, cooked or expanded cationic starch.

[0204] In one embodiment, at least one fiber layer comprises 0.1 to 5 wt % CMC.

[0205] In one embodiment, at least one fiber layer contains 0.1 to 5 wt% polyamide-epichlorohydrin (PAE). Preferably, the fiber layer further comprises a sizing agent, such as AKD. PAE can enhance the bonding of the sizing agent to the fiber.

[0206] In one embodiment, at least one fiber layer comprises a retention aid, such as 0.1 to 5 wt % of a retention aid.

[0207] The retention aid may be an anionic polymer retention aid.

[0208] In one embodiment, at least one of the fiber layers comprises a wet strength agent.

[0209] The wet strength agent may be selected from the group consisting of polyamide epichlorohydrin, polyethyleneimine, dialdehyde starch, polyacrylamide, glyoxal or melamine formaldehyde, polyamide epichlorohydrin and urea formaldehyde melamine and any combination thereof.

[0210] In one embodiment, at least one fiber layer comprises a dispersant or a flotation agent.

[0211] In an embodiment, at least one fiber layer comprises a mineral filler, for example 0.1 to 20 wt % of a mineral filler.

[0212] In an embodiment, the fiber layer of the product comprises less than 5 wt%, such as less than 1 wt%, of mineral filler.

[0213] In an embodiment, all or at least one of the fiber layers comprises 0.1 to 20 wt% of a strengthening additive, such as nanocellulose or microfibrillated cellulose (MFC) or other strengthening cellulose based materials.

[0214] Preferably, the fiber layer of the product comprises less than 10 wt %, for example less than 5 wt %, for example less than 2 wt % wax, plastic and fluorochemical. In one embodiment, the fiber layer of the product comprises less than 2 wt % wax. In one embodiment, the fiber layer of the product comprises less than 2 wt %, for example less than 1 wt % plastic. In one embodiment, the fiber layer of the product comprises less than 2 wt %, for example less than 1 wt % fluorochemical. In some embodiments, the product is substantially free of wax, plastic (for example thermoplastic material) and fluorochemical, particularly free of fluorochemical.

[0215] For bakeable applications, additives and foaming chemicals can be selected from additives approved for food contact materials or packaging and which are also approved for bakeable food packaging materials for heating. Preferably, the additives are selected from the following approved additives: BfRXXXVI / 2. Paper and paperboard for baking: https: / / www.bfr.bund.de / cm / 349 / XXXVI-2-Paper-and-Paperboard-for-Baking-Purposes.pdf.

[0216] For products not intended for oven use, additives and foaming chemicals can be chosen more freely among all additives approved for use in food contact materials or packaging.

[0217] The amount of barrier additive may be in the range of 0.5 to 25 wt%, such as 1 to 10 wt%, such as 2 to 10 wt%, such as 5 to 8 wt%, calculated on the dry fiber weight in the fiber layer.

[0218] “Food contact materials” refers to all materials and articles intended to come into contact with food, such as packaging and containers.

[0219] Preferably, the product complies with Regulation (EC) No 1935 / 2004.

[0220] In one embodiment, additives such as pigments, binders, and sizing agents are provided to meet the requirements of the bakeable product.

[0221] Product and weight

[0222] In some embodiments, the dry weight of the product is between 5 and 900 g / m 2 In the range of, for example, 100 to 900 g / m 2In the range of, for example, 200 to 750 g / m 2 In the range of, for example, 300 to 600 g / m 2 within the range.

[0223] In one embodiment, the dry weight of each fiber layer may be in the range of 40 to 400 g / m 2 In the range of, for example, 80 to 300 g / m 2 within the range.

[0224] In one embodiment, the dry weight of the bottom fiber layer and / or the inner fiber layer of the product is 80 to 400 g / m 2 In the range of, for example, 100 to 400 g / m 2 , for example 200 to 300 g / m 2 .

[0225] In one embodiment, the dry weights of the bottom and top fiber layers of the product are respectively between 80 and 150 g / m 2 within the range.

[0226] In one embodiment, the dry weight of the inner fiber layer or the middle fiber layer of the product is 150 to 250 g / m 2 within the range.

[0227] In one embodiment, the dry weight of the first fiber layer and / or the second fiber layer of the product is 10 to 150 g / m 2 In the range of, for example, 60 to 150 g / m 2 , or for example 20 to 60 g / m 2 , for example 30 to 50 g / m 2 .

[0228] In one embodiment, the average density of the product is greater than 500 kg / m 3 , for example, greater than 600kg / m 3 , for example, greater than 700kg / m 3 .

[0229] In one embodiment, the density of the inner fiber layer or the inner fiber layer is greater than 100 kg / m 3 .

[0230] In some embodiments, the product may comprise 2 to 20 fiber layers, such as at least three fiber layers, such as exactly three fiber layers.

[0231] In some embodiments, the product includes exactly two fiber layers or exactly three fiber layers.

[0232] Preferably, the product is a three-dimensional moulded multilayer fibre product obtained by using a mould comprising at least one three-dimensional non-planar mould surface, wherein said product exhibits a three-dimensional shape conforming to the shape of said three-dimensional non-planar mould surface.

[0233] For example, the product may have the shape of a cup, plate, bowl, pan, clamshell, or tray.

[0234] Typically, the product is a food or liquid package or container or a food or liquid serving product, such as a beverage cup or a food tray or a plate or a baking tray or a disposable lasagna tray type product.

[0235] In some embodiments, the product may be baked, for example, may be baked to a temperature of at least 100°C, preferably at least 220°C.

[0236] In some embodiments, the product is a micro-bakeable food or liquid package or container, such as a food tray.

[0237] In one example, the product is a container for baking, such as an ovenable pan.

[0238] The product can be used for packaging, storing, serving, preparing, cooking and / or heating food or liquid. The liquid can be a drinkable liquid, such as a beverage.

[0239] More generally, the product can be used to package and store any product containing oil and / or water.

[0240] The product may be a product that is intended for use on or located on greasy or oily surfaces or in a moist environment.

[0241] The thickness of the product, ie the smallest dimension, ranges from 300 to 1000 μm, such as 450 to 900 μm.

[0242] The product has a Bendtsen slip range of 50 to 4000 ml / min, such as 100 to 1000 ml / min.

[0243] The product has a tensile index in the range of 10 to 60, such as 20 to 60 Nm / g, in the machine and transverse directions.

[0244] The elastic modulus of this product ranges from 3.0 to 6.0 GPa in both the machine and cross directions.

[0245] The product may have a bending stiffness (Taber 15°) in the machine and transverse directions in the range of 20 to 80 mNm, such as 20 to 50 mNm, or 40 to 80 mNm.

[0246] In a first exemplary embodiment, the following blowing agents and additives are used in the manufacture of a three-layer fiber product: Top fiber layer: SDS, PAE and AKD Middle fiber layer: PVA Bottom fiber layer: SDS and AKD

[0247] In a second exemplary embodiment, the following blowing agents and additives are used in the manufacture of a three-layer fiber product: Top fiber layer: PVA and AKD Middle fiber layer: SDS, PAE and AKD Bottom fiber layer: PVA and AKD

[0248] In a third exemplary embodiment, the following foaming agents and additives are used in the manufacture of a three-layer fiber product: Top fiber layer: SDS, PAE and AKD Middle fiber layer: SDS Bottom fiber layer: PVA

[0249] Now turning to the accompanying drawings:

[0250] Figure 1 A multi-layer fiber product according to at least some embodiments of the present invention is schematically shown, comprising a first fiber layer 101 (lowermost fiber layer), a second fiber layer 102 (uppermost fiber layer), and an inner fiber layer 103 located between the first fiber layer 101 and the second fiber layer 102 .

[0251] Figure 2 (Reference) shows a stereomicroscope image of a three-layer structure obtained by foam molding using SDS as a foaming agent. Scale: 1000 μm (left), 1000 μm (middle) and 100 μm (right).

[0252] Figure 3 Stereoscopic microscope images of a three-layer structure obtained by foaming using PVA as a foaming agent, AKD as a hydrophobic agent and additionally a retention agent are shown. Scale: 1000 μm (left), 1000 μm (middle) and 100 μm (right).

[0253] Figure 4 Stereoscopic microscope images of a single-layer structure obtained by foaming using PVA as a blowing agent, AKD as a hydrophobic agent and additionally a retention agent are shown. Scale: 1000 μm (left), 1000 μm (middle) and 100 μm (right).

[0254] Figure 5 A flow chart is shown, which shows the process steps for manufacturing a multi-layer foam molded product according to an embodiment of the present invention. The method comprises the following steps: 501: Preparing a fiber raw material having a fiber consistency of, for example, 1 to 3% 502: Processing of raw materials, e.g. by refining, adjusting pH and / or adding chemicals, e.g. PAE, retention aids, MFC, pigments and any mixture thereof 503a, 503b, 503c: Foams 504a, 504b, 504c (not shown) are prepared from the processed raw materials, respectively. 505: Foams 504a, 504b, 504c are molded to obtain a multi-layer foam molding structure 506: Hot pressed multi-layer foam molding structure from one or both sides 507: Optional finishing such as coating, printing, cutting and / or packaging

[0255] Figure 6 Foaming of a three-layer fiber structure according to at least some embodiments of the present invention is shown. Pressure may be applied from only one side of the fiber structure or layer. Vacuum may be applied from the opposite side of the fiber structure or layer. Figure 6 In the left part of the , a fiber layer that will eventually become the middle fiber layer is formed. Figure 6 In the middle part of the , a further fiber layer is formed which will eventually become the top fiber layer. Figure 6 In the right part of , a further fiber layer is formed which will eventually become the bottom fiber layer, so that a three-layer fiber structure is obtained.

[0256] Example

[0257] The following three-layer samples 1 to 4 were prepared and tested. The upper and lower fiber layers of all samples consisted of 50% BHKP (bleached hardwood kraft pulp) and 50% BSKP (bleached softwood kraft pulp), and the middle layer consisted of 100% BCTMP (bleached chemi-thermomechanical pulp).

[0258] Sample 1 is a reference sample. SDS was used as a foaming agent. No retention aid, PAE or AKD was used.

[0259] Sample 2 used SDS as the blowing agent and PAE and AKD as additives.

[0260] Sample 3 used PVA as a foaming agent, and a retention aid and AKD as additives.

[0261] SDS and PVA were used as foaming agents in sample 4. Retention aids and AKD were used as additives.

[0262] In these tests, SDS was used as a surface active blowing agent (as anionic surfactant), PVA was used as a polymer blowing agent (as nonionic polymer), AKD was used as a hydrophobic agent (as internal sizing agent), and PAE was used as a wet strength agent. A retention aid was applied.

[0263] Table 1 provides the values ​​for the individual layers, labeled top / middle / bottom. The contact angle values ​​refer to the surface free energy (Kruss) contact angle in one second (1 s).

[0264] Table 1

[0265] Based on the experiments, we made the following observations: The hydrophobicity of AKD increased significantly, as shown by the increased contact angle and decreased Cobb value. The reduction in polar components also supports the conclusion that wettability decreases when the total surface energy of the sample decreases. By carefully selecting surfactants, hydrophobic agents and additives to be incorporated into the various layers of the fibrous multilayer product, the surface and functionality of the product can be modified to match the final further processing steps (e.g. coating) or end-use application (e.g. food packaging).

[0266] It should be understood that the embodiments of the present invention disclosed are not limited to the specific structures, process steps or materials disclosed herein, but are extended to their equivalents recognized by ordinary technicians in the relevant field. It should also be understood that the terms used herein are only used to describe specific embodiments and are not intended to be limiting.

[0267] References to "one embodiment" or "an embodiment" in this specification mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing in various places in this specification do not necessarily refer to the same embodiment.

[0268] As used herein, for convenience, multiple items, structural elements, constituent elements and / or materials may be presented in a common list. However, these lists should be interpreted as if each member of the list is individually identified as a separate and unique member. Therefore, unless otherwise stated, it should not be interpreted as being in fact equivalent to any other member in the same list based solely on the fact that a single member in such a list appears in the same group. In addition, various embodiments and examples of the present invention and alternatives to its various components may be cited herein. It should be understood that such embodiments, examples and alternatives should not be interpreted as being in fact equivalent to each other, but should be regarded as independent and autonomous representations of the present invention.

[0269] In addition, the features, structures or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, many specific details, such as examples of lengths, widths, shapes, etc., are provided to provide a thorough understanding of embodiments of the present invention. However, those skilled in the relevant art will recognize that the present invention may be implemented without one or more of the specific details, or using other methods, components, materials, etc. In other cases, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the present invention.

[0270] Although the above examples illustrate the principles of the present invention in one or more specific applications, it will be apparent to those skilled in the art that many modifications may be made to the form, use and implementation details without departing from the principles and concepts of the present invention without exercising creative ability. Therefore, the present invention is not limited to the following claims.

[0271] The verbs "comprise" and "include" are used in this document as open limitations, neither excluding nor requiring the presence of unrecited features. Unless expressly stated otherwise, the features recited in the dependent claims may be freely combined with each other. Furthermore, it should be understood that the use of "a" or "an" (i.e. the singular) in this document does not exclude a plurality. Industrial Applicability

[0272] The present invention has industrial applicability at least in the manufacture of molded fiber products. Acronyms SDS Sodium dodecyl sulfate PVA polyvinyl alcohol AKD Alkyl Ketene Dimer PAE polyamide-epichlorohydrin MFC Microfibrillated Cellulose APG alkyl polysaccharide BHKP bleached hardwood kraft pulp BSKP bleached softwood kraft pulp BCTMP bleached chemical thermomechanical pulp Reference Symbols List 101 First Fiber Layer 102 second fiber layer 103 inner fiber layer 501 Preparing a fiber raw material having a fiber consistency of, for example, 1 to 3% 502 Processing of raw materials, e.g. by refining, adjusting pH and / or adding chemicals, e.g. PAE, retention aids, MFC, pigments and any mixture thereof 503a, 503b, 503c prepare foams 504a, 504b, 504c (not shown) from the processed raw materials respectively. 505 forms foams 504a, 504b, 504c to obtain a multi-layer foam molding structure. 506 Hot pressed multi-layer foam molding structure from one or both sides 507 optionally performs finishing, such as coating, printing, cutting and / or packaging

Claims

1. A method comprising: - forming a multilayer foam fiber structure from foam fiber compositions in a mold, wherein each of the foam fiber compositions comprises cellulose fibers, water, air and at least one foaming agent; - dehydrating the foam fiber structure; - hot pressing the dehydrated structure to obtain a molded fiber product; wherein the at least one blowing agent comprises at least one surfactant blowing agent and / or at least one polymer blowing agent, and Wherein, at least one of the foam fiber compositions includes a hydrophobic agent.

2. The method according to claim 1, wherein: Each layer is formed from a respective foam fiber composition.

3. The method according to any one of the preceding claims, wherein Each foam fiber composition comprises, independently of one another, at least one surface-active blowing agent, such as an anionic surfactant, and / or at least one polymer blowing agent, such as a nonionic polymer.

4. The method according to any one of the preceding claims, wherein At least two different blowing agents, such as at least three different blowing agents, such as at least four different blowing agents are used in the process.

5. The method according to any one of the preceding claims, wherein At least one of the foam fiber compositions comprises a surface active blowing agent and a polymer blowing agent.

6. The method according to any one of the preceding claims, wherein: At least two of the foamed fiber compositions comprise different blowing agents, such as a different set of blowing agents.

7. The method according to any one of the preceding claims, wherein The total amount of blowing agent in each foamed fiber composition ranges from 0.1 to 35 wt%, such as 5 to 20 wt% or such as 1 to 3 wt% or such as 0.1 to 1 wt%, calculated on the weight of dry fibers in the foamed fiber composition.

8. The method according to any one of the preceding claims, wherein The foamed fiber composition for at least one fiber layer comprises at least 0.5 wt. %, such as at least 1 wt. %, such as at least 5 wt. %, such as 5 to 35 wt. % of a nonionic polymer as a foaming agent, calculated on the dry fiber weight in the fiber composition, and The foamed fiber composition for at least one fiber layer comprises at least 0.1 wt. %, such as at least 0.5 wt. %, such as at least 1 wt. %, such as 0.1 to 1 wt. % or 1 to 5 wt. % of anionic surfactant as a foaming agent, calculated on the weight of dry fibers in the fiber composition, wherein The at least one fiber layer may be the same or different fiber layers.

9. The method according to any one of the preceding claims, wherein: The at least one nonionic polymer is selected from the following group: polyvinyl alcohol (PVA), polyoxyethylene lauryl ether (Brij), polyethylene glycol sorbitan monolaurate (Tween 20), PEG-6 lauramide, alkyl polyglycosides (APG), fatty alcohol ethoxylates, alkylphenol ethoxylates, fatty acid ethoxylates, fatty amide ethoxylates, alkyl glucosides, sugar-based nonionic polymers such as sorbitan alkanoates, sorbitan fatty acid esters (Span) and combinations thereof.

10. The method according to any one of the preceding claims, wherein: The at least one anionic surfactant is selected from the group consisting of sodium lauryl sulfate, alpha-olefin sulfonates, alkyl sulfates, alkylbenzene sulfonates, alkyl ether sulfates, taurates, isethionates, and combinations thereof.

11. The method according to any one of the preceding claims, wherein The foamed fibre composition for at least one fibre layer of the product comprises at least 0.5 wt%, such as at least 1 wt%, such as 1 to 50 wt% polyvinyl alcohol, calculated on the weight of dry fibres in the fibre composition.

12. A method according to any one of the preceding claims, wherein: The foamed fiber composition for at least one fiber layer comprises a nonionic polymer and an anionic surfactant in a molar ratio of 5:95 to 50:50, such as 10:90 to 30:

70.

13. The method according to any one of the preceding claims, wherein: At least two, such as at least three, of the foamed fiber compositions further comprise a hydrophobizing agent or a sizing agent.

14. The method according to any one of the preceding claims, wherein: The hydrophobic agent is contained at least in the finally formed fiber layer.

15. The method according to any one of the preceding claims, wherein The hydrophobic agent is contained at least in the top fiber layer.

16. The method according to any one of the preceding claims, wherein: The hydrophobic agent is contained at least in the inner fiber layer.

17. A method according to any one of the preceding claims, wherein: All inner fiber layers, for example all fiber layers of the product, contain a hydrophobic agent to impart barrier properties, for example water resistance, to the product.

18. A method according to any one of the preceding claims, wherein: The hydrophobic agent is alkyl ketene dimer (AKD).

19. A method according to any one of the preceding claims, wherein: The foamed fiber composition for at least one fiber layer comprises at least 0.1 wt%, such as 0.1 to 1 wt%, such as 0.2 to 0.8 wt%, of a hydrophobizing agent, preferably AKD, calculated on the dry fiber weight in the fiber composition.

20. A method according to any one of the preceding claims, wherein: The moulded fibre product comprises at least three fibre layers, such as exactly three fibre layers.

21. A method according to any one of the preceding claims, wherein: The foamed fiber composition of at least one fiber layer comprises a surface active blowing agent, a hydrophobic agent and a wet strength agent, preferably SDS, AKD and PAE, respectively.

22. A method according to any one of the preceding claims, wherein: The resulting molded fiber product is further coated or configured to be coated with a non-fibrous barrier coating that imparts water resistance, water vapor resistance, gas resistance, such as oxygen resistance, and / or grease resistance.

23. A method according to any one of the preceding claims, wherein: The cellulose fibers consist of or include bleached chemical pulp and / or bleached chemithermomechanical pulp.

24. A method according to any one of the preceding claims, wherein: The foamed fiber composition for at least one fiber layer comprises 0.1 to 1 wt. %, such as 0.2 to 0.8 wt. % AKD, calculated on the dry fiber weight in the fiber composition.

25. The method according to any one of the preceding claims, in, The molded fiber product comprises at least three fiber layers, and Therein, the foam fiber composition for at least one fiber layer comprises SDS as a surface active foaming agent, AKD as a hydrophobic agent and PAE as a wet strength agent.

26. The method according to claim 1, in, The molded fiber product comprises at least three fiber layers, wherein the foam fiber composition for the top fiber layer and the bottom fiber layer comprises a nonionic polymer as a foaming agent, and The foam fiber composition for the inner fiber layer includes an anionic surfactant as a foaming agent, and The foamed fiber composition for the top fiber layer further comprises a hydrophobic agent, such as a size, and / or the foamed fiber composition for the bottom fiber layer further comprises a hydrophobic agent, such as a size.

27. The method according to claim 1, in, The molded fiber product comprises at least three fiber layers, wherein the foam fiber composition for the top fiber layer and the bottom fiber layer comprises an anionic surfactant as a foaming agent, and The foam fiber composition for the inner fiber layer includes a nonionic polymer as a foaming agent, and The foamed fiber composition used for the inner fiber layer may also include a hydrophobic agent, such as a size.

28. A method according to any one of the preceding claims, wherein: The foamed fiber composition for at least one fiber layer comprises a nonionic surfactant, such as glucose amide, optionally in combination with an anionic surfactant, such as SDS.

29. A moulded multi-ply fibrous product obtainable by the process as claimed in any one of the preceding claims.

30. The molded multi-layer fibrous product of claim 29, wherein: The dry weight of each fiber layer is between 30 and 700 g / m 2 within the range.

31. A moulded multi-layer fibrous product according to any one of claims 29 to 30, wherein The Schopper-Riegler number of the cellulose fibers of the one or more inner fiber layers of the product is less than 50, such as less than 30.

32. A moulded multi-layer fibrous product according to any one of claims 29 to 31, wherein The Schopper-Riegler number of the cellulose fibers of the bottom fiber layer of the product is at least 20, such as from 20 to 40.

33. A moulded multi-layer fibrous product according to any one of claims 29 to 32, wherein: The cellulose fibres of the top fibrous layer of the product have a Schopper-Riegler number of at least 40, such as at least 50.

34. A molded multilayer fibrous product according to any one of claims 29 to 33, which is a food or liquid packaging or a food or liquid serving product or a part thereof, and preferably at least the top fibrous layer configured to be in contact with the food or liquid comprises a hydrophobic agent to impart barrier properties.

35. A moulded multilayer fibrous product according to any one of claims 29 to 34, being a thin walled moulded fibrous product obtained by a foam moulding process, the product having a variable or substantially constant thickness, typically less than 2 mm in its shortest dimension.

36. A moulded multi-layer fibrous product according to any one of claims 29 to 35, wherein The product has a Bendtsen smoothness in the range of 50 to 4000 ml / min, for example 100 to 1000 ml / min, and a bending stiffness (Taber 15°) in the range of 40 to 80 mNm in the machine and transverse directions.

37. A moulded multi-layer fibrous product according to any one of claims 29 to 36, in, The Schopper-Riegler number of the cellulose fibers of the one or more inner fiber layers of the product is less than 30, wherein the Schopper-Riegler number of the cellulose fibers of the bottom fiber layer of the product is from 20 to 40, and The cellulose fibers of the top fiber layer of the product have a Schopper-Riegler number of at least 40.

38. Use of a product according to any one of claims 29 to 37 as a food or liquid packaging or a food or liquid serving product or a part thereof, or for packaging, serving, storing, preparing, cooking and / or heating food or liquids.

39. Use of a nonionic polymer as blowing agent and AKD as internal sizing agent for the manufacture of a molded fiber product or a part thereof, such as a layer, by a process comprising foam forming and subsequent hot pressing.

Images