A method and a molded multilayer fibrous product

Abstract

According to an embodiment of the present application, there is provided a method comprising: providing a first fibrous composition and a second fibrous composition, each independently comprising cellulose fibers and water; adding fibrillated fibers and a blowing agent to at least one of the fibrous compositions in any order, wherein the fibrillated fibers are added in the form of a water suspension having a concentration of at least 2%; foaming at least one of the first fibrous composition and the second fibrous composition; shaping and dewatering the first fibrous composition and the second fibrous composition in a mold to obtain a first fibrous layer and a second fibrous layer, respectively, in a stacked configuration; and hot pressing the shaped and dewatered stack comprising the first fibrous layer and the second fibrous layer to obtain a molded multi-layer fibrous product.

Description

Technical Field

[0001] This application relates to molded multilayer fiber products. Background Technology

[0002] In the manufacturing of molded fiber products, a good retention rate is required to achieve high-yield, high-efficiency production with a low defect rate, while avoiding excessive addition of chemical agents. Stable and optimized retention rate control can achieve higher and more efficient production while saving costs. Excessive or fluctuating levels of fines, fillers, and chemicals in the white water system pose a risk, especially in closed systems, potentially leading to sediment buildup, paper breaks, system contamination, unstable quality, and operational problems.

[0003] In foam molding processes, the retention of wet-end chemicals has always been particularly difficult due to interference from the charged environment and surfactants typically used to generate foam. Vacuum-assisted dehydration during molding also poses a challenge to the efficient retention of chemicals.

[0004] The purpose of this invention is to solve at least some of the above-mentioned problems and to provide an improved method for manufacturing molded fiber products, particularly products obtained by foam molding methods. Summary of the Invention

[0005] This invention is defined by the features defined in the independent claims. Specific embodiments are defined in the dependent claims.

[0006] According to a first aspect of the invention, a method is provided, comprising: providing a first fiber composition and a second fiber composition, each independently comprising cellulose fibers and water; adding fibrillating fibers and a foaming agent to at least one fiber composition in any order, wherein the fibrillating fibers are added in the form of an aqueous suspension with a consistency of at least 2%; foaming at least one of the first and second fiber compositions; shaping and dehydrating the first and second fiber compositions in a mold to obtain a first fiber layer and a second fiber layer in a stacked configuration, respectively; and hot-pressing the shaped and dehydrated stack comprising the first fiber layer and the second fiber layer to obtain a molded multilayer fiber product.

[0007] According to a second aspect of the present invention, a molded multilayer fiber product obtained by the method of the first aspect is provided.

[0008] According to a third aspect of the invention, a molded multilayer fiber product is provided, comprising: a first fiber layer; a second fiber layer; and optionally, at least one inner fiber layer located between the first fiber layer and the second fiber layer, wherein each fiber layer comprises: each independently comprising a cellulose fiber material, wherein at least one fiber layer comprises fibrillated fibers, wherein the fiber layers comprising at least fibrillated fibers (preferably all fiber layers of the product) are formed by a foaming method in a mold, and the fibrillated fibers are activated by high-shear mixing during the foaming process of the foaming method.

[0009] According to a fourth aspect of the invention, it is provided to use the molded multilayer fiber product according to the second or third aspect as a food or liquid packaging, food or liquid container product or a component thereof, or in the packaging, containerization, storage, cooking and / or heating of food or liquid.

[0010] Various embodiments of the first, second, third, or fourth aspect may include one or more features from the following list: At least one fiber composition contains at least 1 wt% (e.g., at least 5 wt%), such as 5 to 15 wt% of fibrillated fibers (e.g., microfibrillated cellulose (MFC)), the content being calculated based on the dry weight of the cellulose fibers.

[0011] The fiber composition used for the outermost fiber layer (e.g., the uppermost fiber layer) comprises fibrillated fibers.

[0012] The method also includes activating the fibrillated fibers.

[0013] The method also includes activating the fibrillated fibers, wherein the activation includes increasing the accessibility of cellulose in the fibrillated fibers so that they can interact with solvents and / or chemical reactants and / or other fiber ingredient components.

[0014] The activation includes increasing the specific surface area of ​​the fibrillated fibers through mechanical treatment, such as exposing the fibrillated fibers to mechanical shear forces or high-shear stirring, or through alkali treatment.

[0015] The activation includes high-shear mixing during the foaming process.

[0016] The method includes: adding fibrillated fibers to a fiber composition; optionally, performing high-shear mixing on the fiber composition, particularly for at least partially activating the fibrillated fibers; adding a foaming agent to the fiber composition; and performing high-shear mixing on the fiber composition to foam the fiber composition and activate the fibrillated fibers.

[0017] fibrillated fibers can improve the retention rate of wet-end additives in the fiber layer.

[0018] fibrillated fibers can improve the oil resistance of the fiber layer.

[0019] The fibrillated fibers are selected from the following group: microfibrillated cellulose (MFC), nanofibrillated cellulose (NFC), microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC), cellulose microfibrils (CMF), cellulose nanofibrils (CNF), cellulose nanocrystals (CNC), cellulose nanofibers, and any combination thereof.

[0020] fibrillated fibers comprise microfibrillated cellulose prepared from wood fibers (e.g., wood pulp, such as chemical pulp and / or mechanical pulp), which may be bleached or unbleached.

[0021] The fibrillated fiber has a Schopper-Riegler value of at least 90.

[0022] The average aspect ratio of the fibrillated fiber is at least 5, for example at least 10, for example at least 30, for example at least 50, for example at least 70, for example at least 90.

[0023] The minimum size of fibrillated fibers is less than 5µm, for example, in the range of 2nm to 1µm.

[0024] The longest dimension (typically the average length) of fibrillated fibers is less than 500µm, for example, in the range of 100nm to 500µm.

[0025] The method includes: providing a first fiber composition, a second fiber composition, and one or more other fiber compositions, each composition independently comprising cellulose fibers and water; adding fibrillated fibers and a foaming agent to at least one fiber composition in any order, wherein the fibrillated fibers are added in the form of an aqueous suspension at a concentration of 2% to 20%; foaming the at least one fiber composition comprising fibrillated fibers and a foaming agent; molding and dehydrating the first fiber composition, the second fiber composition, and one or more other fiber compositions in a mold to obtain a first fiber layer, a second fiber layer, and one or more inner fiber layers therebetween in a stacked configuration; and hot-pressing the stack comprising the first fiber layer, the second fiber layer, and one or more inner fiber layers therebetween to obtain a molded multilayer fiber product.

[0026] The method includes: adding a foaming agent to each fiber composition; foaming each fiber composition; and molding each foamed fiber composition in a mold.

[0027] The density of the foam is in the range of 100 to 700 kg / dm³, for example, 300 to 400 kg / dm³.

[0028] The stability of the foam is in the range of 10 to 400 ml, for example 20 to 300 ml, for example 50 to 250 ml, for example 60 to 200 ml, and is measured by the volume of water separated from 1 liter of foam in 10 minutes.

[0029] The turbidity of the foam is in the range of 0 to 550 NTU, for example 2 to 300 NTU, for example 3 to 200 NTU, for example 5 to 100 NTU.

[0030] The foaming agent is selected from the following group: sodium dodecyl sulfate (SDS), polyvinyl alcohol (PVA), alkyl polyglycoside (APG), glycine salt, glucamide, and any combination thereof.

[0031] Cellulose fibers comprise wood pulp selected from the group consisting of chemical pulp, mechanical pulp, and any combination thereof.

[0032] At least one cellulose fiber in the fiber composition (preferably at least the uppermost fiber layer) has been pulped and has a Schubert-Riegel number of at least 40, for example at least 45, for example at least 52, for example at least 60, for example at least 65.

[0033] The fiber composition containing fibrillated fibers also contains one or more additives selected from the group consisting of sizing agents, starch, wet strength agents, retention aids, and any combination thereof.

[0034] The fiber composition containing fibrillated fibers also contains an additive that has an affinity for cellulose fibers, such as an affinity for anionic groups / sites in cellulose fibers.

[0035] At least one fiber composition (preferably a fiber composition for an inner fiber layer) comprises fibrillated fibers, such as microfibrillated cellulose, and also contains starch, and optionally contains a sizing agent.

[0036] Hot pressing includes pressing a stacked body between two forming plates, wherein the temperature of at least one, preferably both, plates is not less than 150°C, for example, 150 to 270°C, for example, 180 to 250°C, for example, 190 to 225°C.

[0037] In each fiber composition, independently of each other, at least 80 wt%, for example at least 95 wt%, of the cellulose fibers are derived from perennial and / or annual plants, such as wood, such as wood pulp, based on the total dry weight of the cellulose fibers.

[0038] The at least one fiber layer contains at least 1 wt%, for example at least 5 wt%, for example 5 to 15 wt% fibrillated fibers, the content of which is calculated based on the dry weight of the cellulose fibers.

[0039] At least one of the fiber layers comprises fibrillated fibers and an additive with affinity for cellulose fibers, such as affinity for anionic groups / sites in cellulose fibers.

[0040] The additive is present in the fiber layer at a content of at least 0.1 wt%, for example at least 1 wt%, for example at least 5 wt%, calculated based on the dry weight of the fiber.

[0041] The first and second fiber layers are the outermost fiber layers of this product.

[0042] The outermost fiber layer (e.g., the uppermost fiber layer) contains fibrillated fibers, and preferably all other fiber layers are substantially free of fibrillated fibers.

[0043] Of the total dry weight of each fiber layer, at least 50 wt%, for example at least 70 wt%, for example at least 80 wt% (calculated independently for each layer), is composed of cellulose fibers derived from perennial and / or annual plants, such as wood pulp.

[0044] The first fibrous layer (i.e., the uppermost fibrous layer) is composed of chemical pulp and microfibrillated cellulose.

[0045] The inner fiber layer is composed of CTMP or BCTMP.

[0046] The second fiber layer (i.e., the bottommost fiber layer) is composed of chemical pulp.

[0047] The density of this molded multilayer product is at least 200 kg / m³. 3 For example, in the range of 200 to 900 kg / m 3 Within the range, for example, 500 to 850 kg / m 3 Calculated based on the weight of dry solids per unit volume.

[0048] Advantages of the present invention The present invention provides an improved method for manufacturing molded multilayer fiber products, particularly a method for manufacturing multilayer foam molded fiber products.

[0049] Certain embodiments of the present invention can improve the retention rate of wet-end chemicals, thereby reducing the turbidity of the foam filtrate and lowering the water Cobb value of the fiber product. Turbidity measures the degree of cloudiness in the foam filtrate caused by free wet-end chemicals and fine fibers, and it is generally desirable to reduce it. Turbidity decreases when wet-end chemicals and fine particles are fixed to the fibers in the foam. The water Cobb value is a measure of water resistance, determined by the amount of water absorbed by the product after a given time.

[0050] Certain embodiments of the present invention can improve the oil and grease resistance of products. Oil and grease resistance is advantageous in food packaging products. The present invention can increase structural density, thereby improving oil and grease resistance.

[0051] Some embodiments of the present invention can improve foam stability, typically by limiting the growth of bubble size within the foam, thereby reducing undesirable interactions between different chemicals, such as sizing agents and surfactants. Furthermore, this method can reduce the amount of blowing agent required to achieve foams with specific foam densities and stability. Since blowing agents typically interfere with the retention of chemicals in fiber compositions, reducing the amount of surfactant used may help improve chemical retention.

[0052] Reducing the amount of foaming agent used can lower the amount of foaming agent residue in the final product. This is advantageous considering food contact regulations that limit the migration levels of surfactants in the final product.

[0053] Some embodiments of the present invention can improve the retention of wet-end chemicals (such as sizing agents) and starch.

[0054] Some embodiments of the present invention can improve foam stability, typically by limiting the growth of bubble size in the foam, thereby reducing undesirable interactions between different chemicals, such as sizing agents and surfactants.

[0055] Some implementations may improve wrinkling and hinge-forming capabilities during folding due to the high surface strength.

[0056] MFC can form a physical oil barrier due to the increased surface density. Fine pulping of MFC can make the fibrillated fibers in MFC compact and reduce the porosity that is usually visible in foamed fiber products.

[0057] In this method, since MFC can be added only to a single layer or part of the layers, the dewatering efficiency can be maintained at a sufficiently high level during the foaming process. Since fiber flocculation is generally not a problem, the dewatering effect of the MFC-containing layer can be further improved by using retention aids.

[0058] In some embodiments, MFCs can be added at high concentrations without the need for an additional separate activation step, which is more environmentally friendly and saves energy and water resources.

[0059] In some embodiments, the problem of loose fibers (i.e., "powdering") on the product surface can be alleviated due to better integration with MFC.

[0060] Some embodiments can minimize the tendency for surface cracking during hot pressing.

[0061] Some embodiments can improve the adhesion of coatings (such as plastic coatings).

[0062] In some embodiments, the surface smoothness resulting from the presence of MFC can have a positive impact on printing, varnishing, lamination, and coating processes.

[0063] While a smooth surface is necessary for achieving high-resolution printing and vibrant images during the printing process, it doesn't necessarily need to be as smooth as possible. For satisfactory printing results, consistent smoothness across the entire surface is more crucial.

[0064] In some embodiments, the product may not contain dust and fibrous debris particles that could affect printing and coating.

[0065] Some embodiments can reduce water consumption in the manufacturing process of molded fiber products because a more closed system can be used and the retention rate of chemicals can be controlled.

[0066] Brief description of the attached figures Figure 1 A multi-layer fiber product according to at least some embodiments of the present invention is illustrated schematically.

[0067] Example definition Unless otherwise stated herein or clearly indicated in the context, any percentages mentioned herein are expressed as wt% based on the total dry weight of the respective composition.

[0068] The amount of additives used is usually expressed in wt%, and it is calculated based on the weight of dry fibers in each formulation.

[0069] In this specification, the term "hot pressing" generally refers to a method of applying high pressure and high temperature for a specified period of time. Hot pressing may involve multiple consecutive cycles or steps during which high pressure and temperature are applied. In some cases, hot pressing may involve applying pressure below atmospheric pressure. Typically, the purpose of hot pressing is to obtain products with high strength, dimensional stability, and smooth surfaces.

[0070] In this specification, the term "molded fiber product" refers to a product obtained by shaping and dehydrating a fiber composition (e.g., slurry or foam) within a closed or enclosed cavity of a mold.

[0071] In this specification, the term "cellulose fiber material" or "cellulose fiber" may refer to a material or fiber composed of cellulose and / or lignocellulose fibers.

[0072] Unless otherwise stated herein or the context clearly defines it, the term "fiber" refers to cellulose and / or lignocellulose fibers.

[0073] In this specification, the terms “fiber pulp”, “fiber suspension”, “fiber formulation” and “fiber composition” are used interchangeably.

[0074] Generally, the terms "top fiber layer" or "top fiber layer" refer to the fiber surface layer that is closest to or in contact with the contents of the package (such as food).

[0075] Generally, the term "bottom fiber layer" or "bottom fiber layer" refers to the fiber surface layer located on the side opposite to the top fiber layer in a fiber structure.

[0076] The term "surfactant" usually refers to a surfactant.

[0077] In this specification, the term "fibrillated fiber" may refer to any of the following: microfibrillated cellulose (MFC), nanofibrillated cellulose (NFC), microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC), cellulose microfibrils (CMF), cellulose nanofibrils (CNF), cellulose nanocrystals (CNC), cellulose nanofibers, and any combination thereof.

[0078] Generally, the terms "fibrillated fiber" or "microfibrillated cellulose (MFC)" refer to cellulose fiber materials that have undergone supplemental or additional fibrillation treatment compared to traditional cellulose pulp fibers derived from papermaking processes. For example, the Schubert-Regler number of fibrillated fibers may be at least 90.

[0079] The products of this invention are typically three-dimensional single-layer or multi-layer fiber products obtained through a foam forming process.

[0080] We have observed that the addition of fibrillated fibers to fiber raw materials can bring unexpected benefits in the manufacture of molded fiber products, such as foam-molded fiber products. In particular, the presence of fibrillated fibers in cellulose pulp can alleviate or resolve problems associated with additive chemicals that tend to interact or react with cellulose fibers.

[0081] Typically, fibrillated fibers increase fiber surface area, thus providing more reaction space for cationic additives. This results in more binding sites for these chemicals, leading to properties such as hydrophobicity. Increased wet-end chemical retention can be observed through phenomena such as reduced turbidity in the foam filtrate and a decrease in the water bleach value.

[0082] Advantageously, incorporating fibrillated fibers into the fiber layers of multilayer molded fiber products can create a physical oil-resistant barrier due to the increased density of the fiber layers. Fine pulping of MFC allows for tight packing of the filaments, filling the pores typically present in foam-molded fiber products. Furthermore, the high specific surface area of ​​fibrillated fibers enhances hydrogen bonding within the fiber structure, resulting in a more compact aggregation of fibers within a dense network.

[0083] We also observed that foam forming methods are particularly suitable for incorporating fibrillated fibers as one of the fiber ingredients.

[0084] This process allows for a wider variety of additive options.

[0085] In one embodiment, the present invention provides a method comprising: providing a first fiber composition and a second fiber composition, both of which independently comprise cellulose fibers and water; adding fibrillated fibers and a foaming agent to at least one fiber composition in any order, wherein the fibrillated fibers are added in the form of an aqueous suspension with a concentration of at least 2%; foaming at least one of the first and second fiber compositions; molding and dehydrating the first and second fiber compositions in a mold to obtain a first fiber layer and a second fiber layer in a stacked structure, respectively; and hot-pressing the molded and dehydrated stack comprising the first fiber layer and the second fiber layer to obtain a molded multilayer fiber product.

[0086] Cellulose fiber Cellulose fibers may contain wood pulp, such as hardwood pulp and / or softwood pulp.

[0087] In each fiber layer, the layers are independent of each other, and at least 80 wt%, for example at least 95 wt%, of the cellulose fibers may be derived from perennial and / or annual plants, such as from wood, such as from wood pulp, and this proportion is calculated based on the total dry weight of the cellulose fibers in the layer.

[0088] In one embodiment, at least 50 wt% (e.g., at least 70 wt%, or at least 80 wt%) of the total dry weight of each fiber layer consists of cellulose fibers derived from perennial and / or annual plants, and the layers are independent of each other.

[0089] Cork pulp can be made from spruce or pine or a mixture thereof.

[0090] Hardwood pulp can be made from birch, poplar, white poplar, alder, maple, eucalyptus, tropical hardwoods or mixtures thereof.

[0091] Wood pulp can be a mixture of hardwood pulp and softwood pulp.

[0092] In one embodiment, the cellulose fibers may comprise pulp made from any annual plant, such as straw, common reed, reed paspalum, bamboo, sugarcane, bagasse, or any herbaceous plant.

[0093] In one embodiment, the cellulose fibers comprise hardwood pulp and softwood pulp in a weight ratio ranging from 1:5 to 5:1, for example from 1:3 to 3:1, or for example from 1:2 to 2:1.

[0094] Cellulose fibers may comprise wood pulp selected from the group consisting of chemical pulp, mechanical pulp, and any combination thereof.

[0095] Chemical pulps are produced through chemical pulping processes. Examples of chemical pulping processes include sulfate pulping (Kraft pulping), sulfite pulping, polysulfide pulping, organic solvent pulping, and soda pulping.

[0096] Typical examples of mechanical pulps include groundwood pulp and pressurized groundwood pulp, refining mechanical pulp, thermomechanical pulp, chemithermomechanical pulp, and bleached chemithermomechanical pulp.

[0097] The slurry can be bleached, for example using methods involving oxidizing bleaching chemicals such as chlorine dioxide, ozone, peroxides, and peroxy acids, and combinations thereof.

[0098] Cellulose fibers may include regenerated fibers, waste paper fibers (such as trimming waste), agricultural fiber waste streams, annual plant fibers, fiber by-products, regenerated cellulose fibers, and combinations thereof. In one embodiment, cellulose fibers comprise waste paper from paper, paperboard, or molding pulp manufacturing processes.

[0099] In one embodiment, at least one cellulose fiber in the fiber composition (preferably at least the uppermost fiber layer) has been pulped, for example to achieve a Schubert-Riegel number of at least 40, for example at least 45, for example at least 52, for example at least 60, for example at least 65.

[0100] Preferably, at least one fiber layer (e.g., the outermost fiber layer) comprises pulped cellulose fibers. These fibers may be pulped to give them a Canadian Standard Freeness (CSF) of less than 350, for example, less than 250.

[0101] Preferably, at least one fiber layer (e.g., the innermost or bottommost layer) is composed of chemithermomechanical pulp (CTMP) and / or bleached chemithermomechanical pulp (BCTMP). The CTMP or BCTMP may be refined to achieve a Canadian standard freeness of less than 800 ml, for example, 450 to 800 ml. The CTMP or BCTMP may also be unrefined.

[0102] In one embodiment, the uppermost fiber layer comprises chemical pulp and fibrillated fibers, preferably MFC.

[0103] In one embodiment, the inner fiber layer comprises CTMP (e.g., BCTMP) and / or chemical pulp.

[0104] In one embodiment, the inner fiber layer comprises CTMP (e.g., BCTMP) and / or waste pulp.

[0105] In one embodiment, the bottommost fiber layer contains CTMP (e.g., BCTMP) and / or chemical pulp.

[0106] The cellulose fiber material may also contain non-wood pulp, such as straw pulp.

[0107] In some embodiments, the cellulose fiber material comprises or is substantially composed of virgin wood pulp, such as virgin bleached chemical pulp that is substantially lignin-free, making the product particularly suitable for food contact, such as for cooking, heating, oven heating, and microwave heating. Preferably, at least one fiber layer (e.g., the outermost fiber layer) comprises virgin cellulose fibers.

[0108] In one embodiment, in at least one fiber layer (e.g., the uppermost fiber layer), at least 80 wt% (e.g., at least 95 wt%) of the cellulose fibers are composed of virgin cellulose fibers (e.g., virgin wood pulp).

[0109] The advantage of virgin pulp lies in its absence of pigments and other undesirable chemicals. Recycled waste typically contains chemical and microbial contaminants, which can affect its safe use. Mixtures of chemical compounds and microbial products can leach from recycled materials, causing various negative health or environmental impacts. Not only the hazards of individual chemical compounds, but also their interactions with other chemical compounds and microbial products, can increase the toxicity of recycled materials and their emissions. Therefore, this invention preferably avoids the use of recycled materials.

[0110] In some embodiments, recycled materials may be used.

[0111] One advantage of chemical pulps (such as bleached chemical pulps) is that they are essentially lignin-free. Another advantage of chemical pulps is that the interfiber bonding in the final product may be superior to that of mechanical pulps.

[0112] Lignin-containing pulp typically lacks sufficient sensory quality and is unsuitable for direct food contact. Furthermore, lignin-containing pulp is prone to aging and yellowing.

[0113] fibrillated fibers In this specification, the term "fibrillated fiber" may refer to any of the following: microfibrillated cellulose (MFC), nanofibrillated cellulose (NFC), microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC), cellulose microfibrils (CMF), cellulose nanofibrils (CNF), cellulose nanocrystals (CNC), cellulose nanofibers, and any combination thereof.

[0114] In particular, the term “fibrillated fiber” (e.g., “microfibrillated cellulose (MFC)”) refers to a cellulose fiber material that has undergone supplemental or additional fibrillation treatment compared to conventional cellulose pulp fibers derived from papermaking processes.

[0115] MFC can be defined according to the TAPPI standard W13021.

[0116] Microfibrillated cellulose can be referred to using any of the following synonyms: cellulose microfibrils, fibrillated cellulose, nanofibrillated cellulose, filament aggregates, nanoscale cellulose filaments, cellulose nanofibers, cellulose nanofibrils, cellulose microfibers, cellulose filaments, microfibrillated cellulose, microfibrillated cellulose, and cellulose microfibril aggregates.

[0117] The fibrillated fibers can be selected from the following group: microfibrillated cellulose (MFC), nanofibrillated cellulose (NFC), microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC), cellulose microfibrils (CMF), cellulose nanofibrils (CNF), cellulose nanocrystals (CNC), cellulose nanofibers, and any combination thereof.

[0118] Preferably, the fibrillated fibers comprise or consist of microfibrillated fibers, such as microfibrillated cellulose (MFC). Microfibrillated cellulose may also contain fine powder, nanocrystalline cellulose, or micron-sized fiber particles.

[0119] Preferably, at least one fiber layer comprises microfibrillated cellulose.

[0120] Preferably, at least the uppermost fiber layer contains fibrillated fibers, such as MFC.

[0121] In one embodiment, only one fiber layer contains fibrillated fibers, such as MFC. This single fiber layer can be the uppermost, innermost, or lowermost layer.

[0122] In one embodiment, only the outermost fiber layer contains fibrillated fibers. This increases the density of the outermost fiber layer and improves its oil-barrier properties. The other fiber layers are preferably substantially free of fibrillated fibers, particularly microstructured or nanostructured fibrillated fibers, thus maintaining greater bulk and facilitating dehydration. For example, the content of fibrillated fibers (such as microfibrillated cellulose) in the other fiber layers may be less than 0.1 wt%, for example less than 0.05 wt%, calculated based on the dry weight of the cellulose fibers.

[0123] In one embodiment, at least one fiber composition comprises at least 0.1 wt% (e.g., at least 1 wt%, at least 5 wt%, or 5 to 15 wt%) of fibrillated fibers (e.g., microfibrillated cellulose (MFC)), the content being calculated based on the total dry weight of the cellulose fibers.

[0124] In one embodiment, at least one fiber composition may comprise 0.1 to 10 wt% starch and 0.1 to 15 wt% fibrillated fibers (e.g., microfibrillated cellulose), the content being calculated based on the total dry weight of the cellulose fibers.

[0125] fibrillated fibers can improve the retention rate of wet-end additives in the first fiber layer.

[0126] fibrillated fibers may improve the oil resistance and even water resistance of the first fiber layer.

[0127] Cellulose fibers can be plant-based, such as those based on wood, beets, wheat straw, bamboo, or bagasse, or derived from microorganisms.

[0128] For example, fibrillated fibers can be made from wood fibers, such as wood pulp, including chemical pulp, thermomechanical pulp, and / or mechanical pulp, which can be bleached or unbleached. Fibrillated fibers can comprise virgin fibers, recycled fibers, or waste paper.

[0129] Fibrous fibers can be prepared by mechanical processes, such as mechanical processes based on single or multiple pulping treatments, pre-hydrolysis and pulping treatments, high-shear crushing, or any combination of the above processes. In addition, fibrillated fibers can also be prepared by chemical processes. Fibrous fibers can be chemically modified, for example, by functionalization with carboxymethyl, aldehyde, ammonium, and / or carbonyl groups, or by enzymatic modification.

[0130] Typically, the average aspect ratio of fibrillated fibers is at least 5, for example at least 10, for example at least 30, for example at least 50, for example at least 70, for example at least 90.

[0131] The minimum fiber size of fibrillated fibers can be less than 5µm, for example less than 1µm, for example less than 300nm, for example less than 100nm, or in the range of 2nm to 5µm, for example 20nm to 1µm.

[0132] The minimum fiber size of fibrillated fibers can be at least 2 nm, for example at least 20 nm, for example at least 100 nm, for example at least 200 nm, for example at least 500 nm.

[0133] The longest dimension (typically the average length) of fibrillated fibers can be less than 500µm, for example, in the range of 100nm to 500µm.

[0134] Forming One or more fiber layers of the product, or the entire product, can be obtained by molding, specifically by wet molding (water molding) or foam molding methods. This method preferably includes a drying step by hot pressing.

[0135] Preferably, one or more fiber layers of the product are obtained by a foam forming method. In one embodiment, all fiber layers are formed by foam forming in a mold.

[0136] In one embodiment, the method includes adding a foaming agent to at least one fiber composition (e.g., to all fiber compositions that are separate from each other); foaming the fiber composition; and forming the foamed fiber composition in a mold.

[0137] In the foam forming process, the fiber layer is formed from a foamed fiber composition comprising cellulose fibers, water, and a foaming agent. In this invention, the foamed fiber composition used to form at least one fiber layer further comprises fibrillated fibers.

[0138] The preferred method for preparing multilayer products is to ensure that all cellulose fibers in the final structure undergo a foam forming process.

[0139] For example, a fiber layer comprising at least fibrillated fibers is produced by a foam forming method in a mold. This fiber layer can be any single fiber layer, such as an uppermost fiber layer, a lowermost fiber layer, and / or one or more inner fiber layers.

[0140] The advantages of foam molding include the ability to produce lighter, larger products. Furthermore, it allows for more uniform structures. Using foam molding technology, multi-layered structures can be easily fabricated in a modular process, meaning all layers can be formed in the same mold, but the composition, fiber raw materials, and additives of each layer can be customized individually. This creates a multi-layered shape or structure in the mold, which is then hot-pressed. Advantageously, one or more fiber layers can be designed to contain fibrillated fibers, forming a dense layer, while other fiber layers do not contain fibrillated fibers, forming a fluffy layer.

[0141] The advantage of dehydrating the entire multi-layer structure in the same mold is that it can also enhance interlayer adhesion during the dehydration process, compared to dehydrating layer by layer.

[0142] In some embodiments, in addition to the foam forming layer, the final product may further include a hydroforming layer. This hydroforming layer, or multiple hydroforming layers, can be formed in a separate process and bonded to the foam forming layer or foam forming multilayer structure by hot pressing. A major advantage of hydroforming is that it does not use foaming chemicals, thus not interfering with the action of sizing agents. In hydroforming methods, individual layers are typically formed independently and demolded from a mold. Individual molds can be used. After demolding, the layers can be stacked into a stack and interconnected and / or bonded to other layers by hot pressing.

[0143] In some embodiments, in addition to the foam-formed layers, the final product may further include water-formed layers, and all layers (i.e., water-formed layers and foam-formed layers) are formed in the same mold to form a multi-layered shape or structure within the mold, which is then subjected to hot pressing.

[0144] In one embodiment, the product includes a plurality of fiber layers prepared by a water-forming process, these fiber layers being bonded together and optionally additionally bonded to at least one foam-formed fiber layer. Preferably, the foam-formed layer or the layers constitute one or both of the outermost fiber layers, such as the topmost fiber layer of the product.

[0145] In one embodiment, the product may include one or more water-forming layers and one or more foam-forming layers. In one embodiment, the inner fiber layer is formed using a water-forming process, while the top and bottom fiber layers are formed using a foam-forming process.

[0146] The steps of preparing the foamed composition and forming a fibrous layer using the foamed composition can be carried out by different alternative methods.

[0147] Cellulose fibers are preferably added in suspension form (e.g., metered addition) at a concentration of at least 2%, for example at least 5%, or 2% to 20%, for example 10% to 20%. The advantages of metered addition of high-concentration cellulose fibers include easier transportation and on-site storage, and greater sustainability.

[0148] Alternatively, fibrillated fibers can be added (e.g., metered) in the form of a dry composition (e.g., powder). The advantages of metered dry fibrillated fibers include savings in freshwater consumption and a reduced carbon footprint.

[0149] Typically, fibrillated fibers are directly metered into the foam tank.

[0150] An advantage of some embodiments is that the method can activate fibrillated fibers during the foam preparation process, typically using the same mixing equipment as that used to generate the foam.

[0151] The term "activating fibrillated fibers" usually refers to the process of breaking down the aggregates or networks of fibrillated fibers.

[0152] In one embodiment, the method further includes activating fibrillated fibers (e.g., microfibrillated cellulose), wherein the activation includes increasing the accessibility of cellulose in the fibrillated fibers to enable them to interact with solvents and / or chemical reactants and / or other fiber ingredient components.

[0153] In one embodiment, the activation includes increasing the specific surface area of ​​the fibrillated fibers by mechanical treatment (e.g., subjecting the fibrillated fibers, such as microfibrillated cellulose, to mechanical shear force or high shear stirring) or by alkali treatment.

[0154] The activation may include high-shear mixing of at least one foamed fiber composition comprising fibrillated fibers. This mixing may be carried out at a rotational speed of at least 500 rpm (e.g., at least 1000 rpm) for at least 5 minutes to activate the fibrillated fibers. Turbulence is preferably created.

[0155] The activation may include increasing the polydispersity of fibrillated fibers and / or disrupting the network / aggregates of fibrillated fibers.

[0156] Various processes can be used to generate foamed mixtures and activate the fibrillated fibers in the mixtures: In some embodiments, cellulose fibers are first mixed with fibrillated fibers. The fibrillated fibers may be added in the form of an aqueous suspension. For example, a composition comprising a fiber slurry at a concentration of at least 0.5% cellulose fibers may be mixed with a composition comprising fibrillated fibers at a concentration of at least 2%. Subsequently, a wet-end additive and a foaming agent are added to the mixture. Finally, the mixture is converted into a foamed composition by stirring. Typically, the cellulose fibers are activated during the foaming step.

[0157] In some embodiments, cellulose fibers are first mixed with at least one additive. Subsequently, fibrillated fibers are added to the mixture, followed by further additives and a foaming agent. Finally, the mixture is converted into a foamed composition by mixing. During the foaming step, the fibrillated fibers may be activated.

[0158] In some embodiments, the method includes: adding fibrillated fibers to a fiber composition; optionally, performing high-shear mixing on the fiber composition to activate the fibrillated fibers; adding a foaming agent to the fiber composition; and performing high-shear mixing on the fiber composition to foam the fiber composition and activate the fibrillated fibers.

[0159] In some embodiments, cellulose fibers in the form of a fibrous paste with a concentration of at least 0.5% are first mixed with additives and a foaming agent. The mixture is then stirred to form a foam composition. Subsequently, fibrillated fibers are added to the foam composition. The fibrillated fibers can be added in the form of an aqueous suspension with a concentration of at least 2% or in dry powder form. After the addition of the fibrillated fibers, the foam mixture is further stirred to activate the fibrillated fibers.

[0160] Typically, before the addition of fibrillated fibers, the concentration of the fiber slurry is approximately 0.5% to 7% (by weight), which is calculated based on the proportion of fiber weight to the total weight of the slurry.

[0161] Different types of foamed fiber compositions can be used to prepare each layer of a multilayer product. Each foamed composition may contain a dedicated set of foaming agents and other additives, such as hydrophobic agents. The term "different types" refers to having different compositions, such as different choices of foaming agents and additives and / or different concentrations.

[0162] The blowing agent preferably comprises a surface-active blowing agent (e.g., a surfactant) and / or a nonionic polymer blowing agent, or a mixture of both. In one embodiment, the blowing agent comprises a surfactant.

[0163] In one embodiment, the surfactant is synthesized at least partially, preferably entirely, from renewable raw materials. The surfactant may be at least partially bio-based, for example, 100% (completely) bio-based.

[0164] One or more foaming agents may be used independently in each fiber layer.

[0165] The surfactant can be nonionic, anionic, cationic, or amphoteric. Preferably, the surfactant is a nonionic surfactant or anionic surfactant, or a combination of nonionic and anionic surfactants.

[0166] The total content of the foaming agent in each foamed fiber composition may be in the range of 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 based on the mass of dry fibers in the foamed fiber composition.

[0167] The appropriate amount of surfactant (e.g., anionic surfactant) is 0.2 to 5 g / L (grams per liter of fiber pulp).

[0168] The appropriate amount of surfactant (e.g., anionic surfactant) is 1 to 20 wt% per dry fiber.

[0169] Anionic surfactants may be selected from the following group: sodium dodecyl sulfate (SDS), α-olefin sulfonates, alkyl sulfates, alkylbenzene sulfonates, alkyl ether sulfates, taurines, hydroxyethyl sulfonates, and combinations thereof.

[0170] Examples of nonionic blowing agents include nonionic polymer blowing agents (such as polyvinyl alcohol) and nonionic surfactants (such as glycosides).

[0171] The foaming agent may be selected from the following group: SDS, polyvinyl alcohol (PVA), polyoxyethylene lauryl ether (Brij), polyoxyethylene sorbitan monolaurate (Tween 20), PEG-6 lauramide, alkyl glycosides (APG) (e.g., alkyl polyglucoside), fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, fatty acid polyoxyethylene ester, fatty amide polyoxyethylene ether, glycine salt, alkyl glycoside (e.g., alkyl glucoside), sugar-based nonionic polymers (e.g., sorbitan alkyl ester), and combinations thereof.

[0172] In some embodiments, the foaming agent may be selected from anionic surfactants and nonionic surfactants. For example, each foamed fiber composition may independently contain at least one surfactant, such as anionic surfactants, amphoteric surfactants, nonionic surfactants, or any combination thereof.

[0173] In one embodiment, the foamed fiber composition for at least one fiber layer comprises an anionic surfactant (e.g., SDS) and a nonionic surfactant (e.g., glucamide). In another embodiment, the foamed fiber composition for at least one fiber layer comprises SDS and an alkyl polyglycoside (APG). In some embodiments, the foaming agent may be selected from the group consisting of SDS, alkyl polyglycosides (APG), glycine salts, glucamide, PVA, and any combination thereof. Adding glucamide together with SDS can improve foaming properties and foam stability. The combination of SDS and APG also exhibits good foam stability. Using the combination of SDS and glucamide can reduce the amount of SDS used, thereby improving sizing performance in the process.

[0174] In this method, foaming agents such as surfactants and a wider range of additives can be recycled.

[0175] The density of foam can range from 100 to 700 kg / dm³. 3 Within the range.

[0176] Preferably, the stability of the foam is in the range of 10 to 400 ml, for example 20 to 300 ml, for example 50 to 250 ml, for example 60 to 200 ml, and is measured by the volume of water separated from 1 liter of foam within 10 minutes.

[0177] The turbidity of the foam can range from 0 to 550 NTU, for example 2 to 300 NTU, for example 3 to 200 NTU, for example 5 to 100 NTU.

[0178] Typically, the bubble size (area-weighted average bubble radius) in foam is approximately 10 to 300 µm, for example 50 to 250 µm, for example 70 to 150 µm, for example 75 to 120 µm.

[0179] The temperature of the foam can be in the range of 15 to 55°C, for example 20 to 40°C, for example 24 to 30°C.

[0180] In one embodiment, a composition suitable for foaming is obtained by mixing fiber pulp (fiber raw material)—which may already contain fibrillated fibers—with foam formed from water and a foaming agent; the foam has an air content of about 10 to 90% (volume percentage), for example 20 to 80%, for example 50 to 75%, for example 60 to 70% (volume percentage). This produces a foamed fiber pulp with a fiber content of about 0.1% to 3% (by weight).

[0181] In one embodiment, instead of mixing the fiber slurry with the pre-made foam, a foaming agent is added to the fiber slurry (which may already contain cellulized fibers), and the mixture is then foamed to obtain a foamed fiber slurry. The concentration of the mixture to be foamed is typically in the range of 0.5% to 3%, for example, 1.0% to 2.5%.

[0182] In this specification, “forming” generally refers to foam forming, which is the process of shaping a composition (usually a foamed composition) into a shape (e.g., a three-dimensional shape) in a mold.

[0183] In a preferred method, the foamed fiber composition is fed into a mold, typically into a cavity of the mold. The mold generally includes a cavity or internal space defined by an inner surface of the mold. Within the cavity, the fed foamed composition is shaped. With the mold closed, a dimension of the cavity (e.g., the shortest dimension) can range from 0.1 to 100 mm, for example, 3 to 100 mm, or 5 to 60 mm.

[0184] The shortest or minimum dimension usually refers to the thickness of the product or layer to be formed.

[0185] A foaming composition may be fed into a mold to form a quantity of the foaming composition, such as a layer of foaming composition, on at least one inner surface of the mold. This layer is typically nonplanar and can be understood as the thickness of the foaming composition covering the inner surface of the mold and conforming to the shape of said surface, such as a variable thickness or a substantially constant thickness.

[0186] Typically, the forming process involves pressing the fiber composition within the internal space of the mold by bringing the various parts of the mold close together.

[0187] The steps for forming a multilayer foamed structure may include feeding a first fiber composition in a foamed form into a mold and shaping the first fiber composition in the mold to prepare a first foamed fiber layer. Subsequently, without removing the first fiber layer from the mold, the process continues by feeding another fiber composition in a foamed form into the mold and shaping the other fiber composition in the mold to prepare another foamed fiber layer. As a result, a double-layer molded foamed structure is obtained in the mold. The process can continue to add more fiber layers to the molded foamed structure.

[0188] Differences may exist between the various fiber compositions, for example, in terms of foaming agents and additives (such as barrier agents or hydrophobic agents), or in terms of cellulose fibers. Importantly, they may also differ in terms of the concentration and / or type of fibrillated fibers (if any) contained therein.

[0189] Unless otherwise stated, “parts of the mold” refers to the mold portion used to define the internal space, thereby facilitating the shaping of the foamed fiber composition.

[0190] Subsequent foamed fiber layers can be fed into the mold, thereby positioned above or below the first foamed fiber layer. Furthermore, the feeding steps can be performed in any order: either the first layer or subsequent layers can be formed in the mold first.

[0191] For example, in the fabrication of multilayer molded foam structures, the forming sequence of the layers can be any suitable order. The inner (to be formed) fiber layer can be formed first, followed by the top and bottom fiber layers formed on either side of the inner fiber layer. Alternatively, the top (to be formed) fiber layer or the bottom (to be formed) fiber layer can be formed first, followed by the remaining fiber layers.

[0192] It is also conceivable that the product is obtained by preparing the first layer and the subsequent foamed fiber layer using a separate mold, and that the obtained first layer and the subsequent fiber layer are combined together in the hot pressing step.

[0193] In one embodiment, feeding the mold includes delivering a foamed fiber composition in a foamed form into the internal space or internal volume of the mold, wherein the internal space is defined by the inner surface of the mold.

[0194] In the dehydration step, it is preferable to be able to apply a vacuum.

[0195] The final multi-layered foamed structure is removed from the mold by opening it.

[0196] During the feeding and shaping of the foamed composition into the mold, it is best to be able to adjust the distance between the various parts of the mold.

[0197] Before injecting the next batch of fiber composition into the mold, it is usually necessary to expand the internal space of the mold by moving the mold components away from each other. The volume of the internal space can be reduced or expanded accordingly to shape the already injected foam or to make room for the next batch of foam to be injected.

[0198] During any adjustment of the internal volume of the mold, some parts of the mold may remain stationary while others move.

[0199] In one embodiment, during the approach or expansion process, one or more components of the mold remain stationary while one or more other components of the mold move.

[0200] For example, a mold may include two sub-molds (such as two half-molds) arranged opposite each other and capable of moving relative to each other. The sub-molds may approach each other to form a product. The sub-molds may separate from each other to expand the internal space, or even further separate to open the mold and remove the formed product from the mold.

[0201] In one embodiment, the product can be obtained using a two-part mold: a female mold and a male mold, which can be arranged opposite each other to form an internal space between them, also referred to as a forming space or forming cavity. The composition to be formed or shaped is fed into the forming space, and then the female mold and / or male mold move closer together, causing the composition to acquire a shape corresponding to the shape of the forming space. "Moving closer together" refers to the process of reducing the internal space by moving one or both of the male and female molds.

[0202] The structure can be dehydrated by applying a vacuum to the internal space of a mold containing the injected foaming composition.

[0203] The dehydration step occurs before the hot pressing step, which ultimately forms a generally smooth and dry product in which all layers have been bonded together.

[0204] During hot pressing, the temperature (e.g., the temperature of the hot press plate) is typically above room temperature, for example at least 50°C, for example at least 100°C, for example in the range of at least 150 to 250°C.

[0205] In some embodiments, hot pressing includes pressing the stacked layers between two forming plates, wherein the temperature of at least one plate (preferably two plates) is not less than 150°C, for example 150 to 270°C, for example 180 to 250°C, for example 190 to 225°C.

[0206] During hot pressing, pressures below atmospheric pressure can be applied, such as 600 kPa or lower.

[0207] Hot pressing may include two or more consecutive hot pressing steps. The total duration of the hot pressing steps may be less than 60 seconds, for example less than 30 seconds.

[0208] During hot pressing, heat can be applied (temperature increased) from one or both sides of the material to be pressed. In one embodiment, heat is applied from only one side.

[0209] During the hot pressing process, heat can only be applied from one side of the multilayer fiber structure, and preferably, the outermost fiber layer on that side of the multilayer fiber structure is substantially starch-free.

[0210] For example, hot pressing may include two hot pressing steps in which heat is applied from the same side in both steps. Alternatively, hot pressing may include two hot pressing steps in which heat is applied from different sides in each step.

[0211] Hot pressing may facilitate the formation of barrier properties or other functional properties, for example, through chemical reactions that occur at high temperatures, such as crosslinking and curing. Therefore, hot pressing may be advantageous when using additives whose effects are enhanced by crosslinking or curing.

[0212] Hot pressing also facilitates the flow of additives such as barrier agents or hydrophobic agents within the multilayer fiber structure.

[0213] Hot pressing helps to block the flow of chemicals. For example, hot pressing from only one side may guide the flow of barrier chemicals within each layer in a different way than hot pressing symmetrically from both sides.

[0214] Hot pressing preferably includes pulse drying.

[0215] Pulse drying typically involves wet pressing under heat. The applied heat can serve two purposes: it can reduce the viscous resistance of water and soften the pulp structure, making it more compressible and thus creating 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 hot medium. This aids the dehydration process because the expanding vapor can displace the bound water.

[0216] Optionally, after the hot pressing step, the product can be kept at a temperature of 50 to 110°C for, for example, 5 to 60 minutes, to further improve or stabilize the barrier properties of the product.

[0217] Additives, barrier properties and sizing At least one fiber layer may contain one or more of the following optional additives: starch; pigments, such as talc, clay, and calcium carbonate; retention aids; fixing agents; barrier agents; latex adhesives; water-soluble adhesives, wet strength agents, CMC; sizing agents, such as AKD or waxes; and any combination thereof. The layer containing optional additives may be a layer containing fibrillated fibers or a layer not containing fibrillated fibers. Therefore, in this application, fibrillated fibers are not classified as optional additives. The amount of optional additives may range from 0.01 to 30 wt%, for example, 0.01 to 10 wt%, for example, 0.1 to 8 wt%, for example, 1 to 5 wt%, calculated based on the weight of dry fibers in the fiber layer. In each individual fiber layer, the amount of optional additives and their properties or functions may be selected independently. Preferably, the performance of the overall product can be optimized by adding or not adding optional additives to each fiber layer separately.

[0218] Preferably, at least one fiber layer comprises starch or a starch derivative as an optional additive. For example, the fiber composition used for the inner layer comprises starch, such as ungelatinized starch. Preferably, the starch gelatinizes during hot pressing.

[0219] At least one fiber composition may comprise fibrillated fibers, starch, and optionally a sizing agent. Furthermore, the fiber composition may also comprise a wet strength agent.

[0220] Starch and microfibrillated cellulose (MFC) can be added to the ingredients separately, either first or second. They can also be mixed together before being added to the pulp. The combination of MFC and starch may allow the product to retain a greater amount of starch. This combination may also produce a synergistic effect, increasing the product's strength without requiring an equivalent increase in density. When MFC and starch are mixed, they typically do not chemically bind together. Instead, starch and MFC may help form cross-links within the pulp fibers of the foam, thereby improving the product's mechanical properties, such as strength.

[0221] The combination of microfibrillated cellulose and starch may allow the product to retain a greater amount of starch. This combination may produce a synergistic effect, enhancing the product's strength without requiring an equivalent increase in density. In some embodiments, the microfibrillated cellulose and starch do not chemically bind to each other upon mixing. Instead, starch and microfibrillated cellulose may contribute to the formation of crosslinks between pulp fibers within the foam, thereby improving the product's mechanical properties, such as strength.

[0222] Improved barrier properties can be achieved in any fiber layer of a product by pulping the fibers and / or adding barrier agents, hydrophobic agents, or reinforcing agents, and / or selecting suitable foaming agents. Different fiber layers can exhibit different barrier properties. For example, one fiber layer may exhibit oil and grease resistance, while another may exhibit water resistance.

[0223] An example of a barrier additive is a sizing agent or hydrophobic agent, typically used for internal and / or surface sizing, preferably for internal sizing. In one embodiment, the sizing agent is designed not to inhibit or reduce the foaming effect of the foaming chemicals.

[0224] The barrier additive may be added to the fiber slurry or slurry prior to the foaming step, in a content of, for example, 0.5% to 15%, or, for example, 2% to 10%; and / or may be added to the foam at the aforementioned content or mixed with the fiber slurry prior to the foam forming step.

[0225] Preferably, the barrier additive is added to the fiber pulp or slurry at a concentration of less than 10% (e.g., less than 5%).

[0226] In one embodiment, at least one fiber layer contains an sizing agent.

[0227] In some embodiments, different amounts of sizing agent may be added to the fiber compositions of each individual layer of a multilayer product. For example, at least before hot pressing, the fiber composition of the bottom fiber layer may contain less hydrophobic agent or sizing agent than the fiber compositions of other layers (particularly the top fiber layer). For example, the fiber composition used for the bottom fiber layer may contain 50 wt% less sizing agent than the fiber composition used for the top fiber layer. Preferably, during hot pressing or pulse drying, some of the sizing agent applied to the top fiber layer will migrate to the other fiber layers.

[0228] The sizing agent can be a cationic sizing agent, anionic sizing agent, and / or a reactive sizing agent.

[0229] In some embodiments, the sizing agent is selected from the group consisting of: styrene-acrylate copolymers (SA), polyurethanes, alkylated polyurethanes, carboxymethyl cellulose and its salts, alkyl celluloses (such as methyl cellulose and ethyl cellulose), styrene / maleic acid copolymers (SMA), diisobutylene / maleic anhydride, acrylonitrile / acrylate copolymers, rosin, waxes (such as alkyl ketene dimers (AKD) or paraffin wax), oils (such as alkenyl succinic anhydride (ASA)), and styrene-acrylate emulsions (SAE).

[0230] One advantage of using sizing agents is that it reduces the undesirable absorption of liquids and / or water and / or moisture by the foamed structure. Therefore, the product's moisture resistance or water resistance is improved.

[0231] Preferred sizing agents are AKD, paraffin wax, or similar waxes.

[0232] In one 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), plasmids, elastomers, ethylene-vinyl alcohol copolymers, and any derivatives, copolymers, and mixtures thereof.

[0233] In one embodiment, at least one fiber layer contains 0.1 to 15 wt% (e.g., 0.1 to 10 wt%, e.g., 0.1 to 5 wt%) of a barrier agent, such as a dispersible polymer barrier agent. Such barrier agents typically provide the barrier properties throughout the structure of the fiber layer.

[0234] In one embodiment, at least one fiber layer comprises 0.1 to 5 wt% polyamide-epoxychloropropane (PAE). Preferably, the fiber layer also comprises a sizing agent, such as AKD. PAE may enhance the bonding between the sizing agent and the fiber.

[0235] In one embodiment, at least one fiber layer comprises a retention aid, such as 0.1 to 5 wt% of a retention aid. The retention aid may be an anionic polymer retention aid. The retention aid may be a cationic polymer retention aid, such as cationic polyacrylamide. The retention aid may comprise microparticles, such as silica microparticles.

[0236] In one embodiment, at least one fiber layer comprises a wet strength agent. The wet strength agent may be selected from the group consisting of: polyamide epichlorohydrin, polyethyleneimine, dialdehyde starch, polyacrylamide, glyoxal or melamine-formaldehyde, polyamide amine epichlorohydrin, and urea-formaldehyde melamine, and any combination thereof.

[0237] In one embodiment, at least one fiber layer contains a dispersant or flotation agent.

[0238] In particular, each fiber layer may contain less than 10 wt% (e.g., less than 5 wt%, or less than 2 wt%) of thermoplastic material (e.g., thermoplastic polymer), calculated based on the total dry weight of the fiber layer.

[0239] Preferably, the fiber layer of the product contains less than 10 wt% wax, plastic, and fluorochemicals, for example less than 5 wt%, for example less than 2 wt%. In one embodiment, the fiber layer of the product contains less than 2 wt% wax. In one embodiment, the fiber layer of the product contains less than 2 wt% plastic, for example less than 1 wt%. In one embodiment, the fiber layer of the product contains less than 2 wt% fluorochemicals, for example less than 1 wt%. In some embodiments, the product is substantially free of wax, plastics (e.g., thermoplastic materials), and fluorochemicals, particularly free of fluorochemicals.

[0240] For oven-safe applications, additives and foaming agents can be selected from additives approved for both food contact materials or packaging and oven-safe food packaging materials intended for heating. Preferably, the additives are selected from BfRXXXVI / 2. Paper and paperboard for baking: Additives approved in https: / / www.bfr.bund.de / cm / 349 / XXXVI-2-Paper-and-Paperboard-for-Baking-Purposes.pdf

[0241] For products not intended for oven use, there is greater freedom to choose additives and foaming agents from all approved additives for use in food contact materials or packaging.

[0242] "Food contact materials" refers to all materials and articles intended to come into contact with food, such as packaging, containers, and tableware.

[0243] Preferably, this product complies with Regulation No. 1935 / 2004 (EC).

[0244] In one embodiment, the fibrillated fibers and optional additives both meet the requirements for a bakeable product.

[0245] product In some embodiments, the present invention provides a molded multilayer fiber product comprising: a first fiber layer; a second fiber layer; and optionally, at least one inner fiber layer located between the first and second fiber layers, wherein each fiber layer comprises, independently comprises, a cellulose fiber material, wherein at least one fiber layer comprising fibrillated fibers (preferably all fiber layers of the product) is obtained by a foaming method in a mold, and the fibrillated fibers have been activated by high-shear mixing during the foaming process of the foaming method.

[0246] The first and second fiber layers can be the outermost fiber layers of the product. Either one or both layers can contain fibrillated fibers.

[0247] In one embodiment, at least one fiber layer contains 0.1 to 15 wt% (e.g., 0.5 to 4 wt%, e.g., 1 to 3 wt%) of fibrillated fibers (e.g., microfibrillated cellulose (MFC)), the content being calculated based on the dry weight of the fibers.

[0248] In one embodiment, at least one fiber layer (e.g., a first fiber layer) contains at least 0.1 wt% (e.g., at least 1 wt%, at least 5 wt%, or 5 to 15 wt%) of fibrillated fibers, the content being calculated based on the dry weight of the fibers.

[0249] In one embodiment, at least one fiber layer comprises fibrillated fibers and an additive with affinity for cellulose fibers, such as an additive with affinity for anionic groups / sites in cellulose fibers.

[0250] In one embodiment, the outermost fiber layer (e.g., the uppermost fiber layer) contains fibrillated fibers, and preferably all inner fiber layers are substantially free of fibrillated fibers.

[0251] In some embodiments, the dry weight of the product is between 5 and 900 g / m³. 2 Within the range, for example, from 100 to 900 g / m 2 Within the range, for example, between 200 and 750 g / m 2 Within the range, for example, between 300 and 550 g / m 2 Within the range, for example, between 350 and 500 g / m 2 Within the range.

[0252] In one embodiment, the dry basis weight of each fiber layer can be between 30 and 500 g / m². 2 Within the range, for example, 40 to 400 g / m 2 For example, 50 to 350 g / m 2 For example, 60 to 300 g / m 2 .

[0253] In one embodiment, the dry weight of the bottom fiber layer and / or the inner fiber layer of the product is between 20 and 400 g / m². 2 Within the range, for example, 100 to 400 g / m 2 For example, 200 to 300 g / m 2 .

[0254] In one embodiment, the dry weight of both the bottom and top fiber layers of the product is between 20 and 150 g / m². 2 Within the range.

[0255] In one embodiment, the dry basis weight of the inner fiber layer or intermediate fiber layer of the product is between 100 and 400 g / m². 2 Within the range, for example, 150 to 250 g / m 2 .

[0256] In one embodiment, the dry basis weight of the first fiber layer and / or the second fiber layer of the product is between 10 and 150 g / m². 2 Within the range, 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 .

[0257] In one embodiment, the density of the molded multilayer product is at least 200 kg / m³. 3 For example, in the range of 200 to 900 kg / m 3 Within the range, for example, 500 to 850 kg / m 3 Calculated based on the weight of dry solids per unit volume.

[0258] In one embodiment, the inner fiber layer or the density of the inner fiber layer is greater than 100 kg / m³. 3 .

[0259] 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.

[0260] In some embodiments, the product comprises exactly two or exactly three fiber layers.

[0261] Preferably, the product is a three-dimensional molded multilayer fiber product, which is obtained by using a mold containing at least one three-dimensional non-planar mold surface, wherein the product presents a three-dimensional shape that conforms to the shape of the three-dimensional non-planar mold surface.

[0262] For example, the product can be in the shape of a cup, plate, bowl, frying pan, clam shell, or tray.

[0263] Typically, the product is a food or liquid packaging or container, or a food or liquid holding product, such as a beverage cup, food tray or plate, baking pan, or disposable lasagna tray.

[0264] In some embodiments, the product can be placed in an oven, for example, at a temperature of at least 100°C, preferably at a temperature of at least 220°C.

[0265] In some embodiments, the product is a microwave-safe food or liquid package or container, such as a food tray.

[0266] In one example, the product is a container for baking, such as a baking pan that can be placed in an oven.

[0267] This product can be used for packaging, storing, serving, preparing, cooking, and / or heating food or liquids. The liquid can be a drinkable liquid, such as a beverage.

[0268] More generally, this product can be used for packaging and storing any product containing oil and / or water.

[0269] This product is designed for use or placement on oily or wet surfaces, or for use in humid environments.

[0270] The thickness (i.e. minimum dimension) of this product can range from 300 to 1000µm, for example 350 to 850µm, for example 400 to 800µm, for example 450 to 650µm.

[0271] The Bendtsen roughness of this product is in the range of 50 to 4000 ml / min, for example 75 to 2000 ml / min, for example 100 to 1000 ml / min, for example 200 to 500 ml / min.

[0272] The tensile strength index of this product in the machine direction and transverse direction can be in the range of 10 to 65 Nm / g, for example 20 to 60 Nm / g, and for example 30 to 55 Nm / g.

[0273] The product has an elastic modulus in the machine and transverse directions ranging from 2 to 8 GPA, for example 3 to 6 GPA, or 3.5 to 5.5 GPA.

[0274] The product’s bending stiffness (Taber 15º) is in the range of 8 to 80 mNm in both the machine and transverse directions, for example 10 to 50 mNm, for example 11 to 40 mNm, for example 15 to 30 mNm.

[0275] The molded fiber product typically contains at least one heat-sealable surface, such as that which can be heat-sealable with polyethylene (PE), bio-based polyethylene (bio-PE), polypropylene (PP), polyethylene terephthalate (PET), and / or polylactic acid (PLA).

[0276] This molded fiber product can be substantially based on biomass. For example, the product contains at least 95 wt%, or at least 99 wt%, of fossil-based materials.

[0277] Other exemplary product performance The following will list various product performance characteristics that can be achieved according to certain embodiments of the present invention.

[0278] The weight of this molded fiber product, according to ISO 536 standard, is between 50 and 800 g / m². 2 Within the range, for example, 150 to 600 g / m 2 For example, 250 to 500 g / m 2 For example, 300 to 475 g / m 2 For example, 320 to 460 g / m 2 .

[0279] The thickness of the molded multilayer fiber product, according to ISO 534 and ISO 187 standards, is in the range of 200 to 850 µm, for example 300 to 750 µm, for example 350 to 700 µm, for example 400 to 600 µm, for example 450 to 550 µm.

[0280] According to SCAN-P 84:1 and DIN 53108 standards, the Bentsen roughness of this molded multilayer fiber product is in the range of 50 to 5000 ml / min, for example 100 to 4000 ml / min, for example 125 to 2000 ml / min, for example 150 to 1000 ml / min, for example 200 to 600 ml / min.

[0281] According to ISO 534 standard, the density of this molded multilayer fiber product can be at least 200 kg / m³. 3 For example, in the range of 200 to 900 kg / m 3 Within the range, for example, 500 to 850 kg / m 3 .

[0282] According to ISO 1924-2 and ISO 1924-3 standards, the tensile strength index of this molded multilayer fiber product can be in the range of 15 to 65 Nm / g, for example 20 to 55 Nm / g, for example 25 to 50 Nm / g, for example 30 to 45 Nm / g.

[0283] The elastic modulus of the molded multilayer fiber product can be in the range of 2 to 8 GPa, for example 2.5 to 7 GPa, for example 3 to 6 GPa, for example 3.5 to 5.5 GPa.

[0284] The bending stiffness (Taber 15°) of this molded multilayer fiber product, according to DIN-53121 (bending stiffness) and TAPPIT 489 (bending strength) standards, can be in the range of 5 to 60 mNm, for example 10 to 55 mNm, for example 15 to 50 mNm, for example 20 to 45 mNm, for example 25 to 40 mNm.

[0285] The stiffness of this molded multilayer fiber product, measured by the paper tray stiffness test (FPI) at a 0.5-inch bend (sample placed at 23°C and 50%RH for 4 hours, measured using a Zwick / Roell Z010 instrument with an applied force of 10kN+500N), can be in the range of 1.0 to 6.0N, for example 1.5 to 5.5N, for example 2.0 to 5.0N, for example 2.5 to 4.5N.

[0286] The stiffness of this molded multilayer fiber product (measured by paper disc stiffness test (FPI), with the sample placed at 23°C and 50%RH for 4 hours and a force of 10kN+500N applied using a Zwick / Roell Z010 instrument) can be in the range of 1.0 to 8.0N, for example 2.5 to 7.0N, for example 3.5 to 6.0N, for example 4.0 to 6.5N.

[0287] The energy required for the structural delamination of this molded multilayer fiber product (energy loss divided by surface area, J / m²) 2 According to the Scott-Bond ISO 16260 standard, this value ranges from 50 to 300 J / m³. 2 Within a range, for example, 100 to 200 J / m 2 For example, 115 to 160 J / m 2 For example, 120 to 145 J / m 2 For example, 125 to 140 J / m 2 .

[0288] According to SCAN-P 26:78, the air permeability of the molded multilayer fiber product can be at least 20 galley seconds, for example at least 50 galley seconds, for example at least 100 galley seconds, for example at least 500 galley seconds, or in the range of 5 to 1000 galley seconds, for example 10 to 500 galley seconds.

[0289] According to ISO 535 standard, the 300-second water permeability value of this molded multilayer fiber product can be less than 120 g / m². 2 For example, in the range of 15 to 100 g / m 2 Within a range, for example, 15 to 60 g / m 2 For example, 15 to 40 g / m 2 .

[0290] The water contact angle of the molded multilayer fiber product can be at least 70°, for example at least 80°, for example at least 85°, for example at least 95°, for example at least 105°, for example at least 115°.

[0291] The 60-second olive oil saturation value of this molded multi-layer fiber product can range from 1 to 120 g / m². 2 Within a range, for example, 2 to 50 g / m 2 For example, 5 to 40 g / m 2 For example, 10 to 30 g / m 2 This value was determined according to ISO 535 standard.

[0292] The molded multilayer fiber product exhibits oil and grease resistance in olive oil at 40°C, as determined by ASTM F119-82, for at least 10 minutes, for example, at least 20 minutes, for example, at least 6 hours, for example, at least 36 hours, for example, at least 7 days.

[0293] The total surface free energy of the molded multilayer fiber product can be at least 10 mN / m, for example at least 15 mN / m, for example at least 20 mN / m, for example at least 25 mN / m, for example at least 30 mN / m, for example at least 35 mN / m.

[0294] The polar surface free energy of this molded multilayer fiber product can be less than 10mN / m, for example less than 8mN / m, for example less than 6mN / m, for example less than 4mN / m, for example less than 1mN / m.

[0295] The dispersion surface free energy of the molded multilayer fiber product can be at least 10 mN / m, for example at least 15 mN / m, for example at least 20 mN / m, for example at least 25 mN / m, for example at least 30 mN / m, for example at least 35 mN / m.

[0296] The water vapor transmission rate of this molded multilayer fiber product (according to ISO 2528 and ASTM E96 standards, under standard conditions of 23°C and 50% RH) is less than 500 g / m³. 2 / 24h, for example 150 to 500 g / m 2 / 24h, or 40 to 150g / m 2 / 24h, or 10 to 40g / m 2 / 24h, or less than 10g / m 2 / 24h.

[0297] Under standard conditions (38℃, 90%RH), the water vapor transmission rate of this molded multilayer fiber product is less than 2500 g / m². 2 / 24h, for example 750 to 2500 g / m 2 / 24h, or 200 to 750g / m 2 / 24h, or 50 to 200g / m 2 / 24h, or less than 50g / m 2 / 24h.

[0298] The average fiber length Lc(l) of the cellulose fibers in the bottommost fiber layer and / or the inner fiber layer (determined using a Valmet Fiber Image Analyzer (ValmetFS5)) is in the range of 0.6 to 2.3 mm, for example 0.8 to 1.6 mm, for example 1.2 to 1.4 mm, and / or the average fiber width is in the range of 10 to 40 micrometers, for example 15 to 35 micrometers, for example 20 to 30 micrometers, for example 22 to 28 micrometers.

[0299] The pulp of the bottom fiber layer of molded multilayer fiber products has a water retention value in the range of 0.8 to 3.5 g / g, for example 1.0 to 2.0 g / g, or 1.25 to 1.65 g / g, as determined by ISO 23714:2014.

[0300] The pulp of the top layer of molded multilayer fiber products, according to ISO 23714:2014, can have a value in the range of 0.8 to 3.5 g / g, for example 1.1 to 3.4 g / g, for example 1.2 to 3.0 g / g, for example 1.6 to 2.8 g / g.

[0301] In this molded multilayer fiber product, the standard deviation of basis weight, as determined according to ISO 536, ranges from 1 to 45 g / m². 2 Within a range, for example, 2 to 35 g / m 2 For example, 3 to 25 g / m 2 For example, 4 to 20 g / m 2 or less than 18g / m 2 .

[0302] The ISO brightness (according to ISO 2470-2) of the molded multilayer fiber product (e.g., its inner layer) may be at least 60%, for example at least 65%, for example at least 75%, for example at least 80%, for example at least 82%. The ISO brightness of the other layers may be at least 80%.

[0303] The Canadian Standard Freeness (CSF) of fiber compositions containing CTMP and / or BCTMP can be in the range of 400 to 800, for example 440 to 570, or 470 to 540.

[0304] The fiber composition used for the outermost fiber layer typically contains bleached chemical pulp with a Canadian Standard Freeness (CSF) ranging from 0 to 750, for example 10 to 600, for example 50 to 500, for example 100 to 400, for example 150 to 350.

[0305] Fiber compositions used for the bottom fiber layer typically contain bleached chemical pulp with a Canadian Standard Freeness (CSF) ranging from 100 to 800, such as 200 to 750, 300 to 700, 400 to 600, or 450 to 550.

[0306] The residual SDS surfactant in this molded multilayer fiber product (determined according to LCK432 anionic surfactant test method (ISO 7875-1)) ranges from 0 to 1000 mg / m². 2 For example, 20 to 800 mg / m² 2 For example, 50 to 700 mg / m 2 For example, 75 to 600 mg / m² 2 For example, 200 to 450 mg / m 2 .

[0307] This molded multilayer fiber product may contain less than 5 mg / g, for example less than 2 mg / g, or for example less than 1 mg / g of AKD, which is not bound to cellulose in the fiber by chemical bonds such as ester bonds. The content of unreacted AKD can be analyzed by gas chromatography (initial temperature 210°C, hold for 1 minute; heating rate 5°C / min; endpoint temperature 300°C) and Soxhlet extraction (90°C, 6 hours).

[0308] According to CEPI Recyclability Laboratory Test Methods, Version 2 (October 2022), this molded multilayer fiber product may have the following recyclability: a recycling score between 90% and 100% (no repulping issues in a standard paper mill), a visual impurity grade of 1 (no visual quality issues), and a paper adhesion grade of 1 (no adhesion issues).

[0309] Figure 1 A molded multilayer fiber product according to at least some embodiments of the present invention is illustrated schematically. The product includes a first fiber layer 101 as the uppermost fiber layer, a second fiber layer 102 as the lowermost fiber layer, and an inner fiber layer 103 located between the first fiber layer 101 and the second fiber layer 102.

[0310] Example We prepared molded three-layer fiber products using a foam forming method.

[0311] The preparation process of samples A through D and their corresponding control samples A through D will be described below. In these samples, MFC was added to a single layer (i.e., the middle layer or the top layer) of the three-layer molded fiber product. The control samples were identical to the samples except that no MFC was added to any layer.

[0312] Sample A and control group A In sample A, MFC was added to the intermediate layer. No MFC was added to the control sample. The fiber pulp in the intermediate layer consisted of BCTMP, adjusted to the desired concentration, with the pH controlled between 7 and 8. PAE was added to the fiber pulp and mixed under high shear conditions for 5 minutes. Subsequently, AKD was added to the fiber pulp and mixed under high shear conditions for 5 minutes. Then, SDS surfactant was added to the fiber pulp and high shear mixing was performed for 5 minutes to produce foam with a density in the range of 300-400 g / L. A certain dose of a 2% solids MFC suspension was directly added to the foamed fiber pulp. The amount of MFC added was controlled to achieve a total dry fiber content of 8 wt% MFC and a BCTMP fiber content of 92 wt%. The concentration of the foamed fiber pulp was adjusted to the target concentration of 1.6%. High shear mixing was performed on the foamed fiber pulp to activate the MFC. The top and bottom fiber compositions of the control and sample layers were the same, consisting of chemical pulp, AKD, and PAE. A three-layer molded fiber product was prepared using these three fiber components by foaming, dehydrating and hot pressing in a mold.

[0313] Sample B and control group B In Sample B, MFC was added to the surface layer. No MFC was added to the control sample. The surface pulp consisted of kraft pulp and was adjusted to the desired concentration with a pH controlled between 7 and 8. A 2% solids MFC suspension was added directly to the pulp. The amount of MFC added was controlled to achieve a total dry fiber content of 15 wt% MFC and 85 wt% kraft fiber in the pulp. The concentration of the MFC-containing pulp was adjusted to the target concentration of 1.2%. The pulp was subjected to high-shear mixing to activate the MFC. Subsequently, PAE was added to the pulp and subjected to high-shear mixing for 5 minutes. AKD was then added to the pulp and subjected to high-shear mixing for 5 minutes. Finally, SDS surfactant was added to the pulp and subjected to high-shear mixing for 5 minutes to produce foam with a density in the range of 300-400 g / L. The middle and bottom layers of the reference and test samples had the same fiber composition, consisting of BCTMP (middle layer) or chemical pulp (bottom layer), with the additional addition of AKD and PAE. Three-layer molded fiber products were prepared using these three fiber components by foaming, dehydration and hot pressing in a mold.

[0314] Sample C and control group C In sample C, MFC was added to the intermediate layer. The fiber pulp of the intermediate layer consisted of BCTMP, adjusted to the desired concentration and pH between 7 and 8. In this sample, a 20% solids MFC suspension was directly added to the BCTMP fiber pulp. High-shear mixing of the fiber pulp activated the MFC. Subsequently, PAE was added to the fiber pulp, followed by 5 minutes of high-shear mixing. Next, AKD was added to the fiber pulp, followed by 5 minutes of high-shear mixing. Then, starch was added to the fiber pulp, followed by 5 minutes of high-shear mixing. The addition of MFC and starch was controlled to achieve a total dry content of fiber + starch in the pulp of: 5 wt% MFC, 7.2 wt% starch, and 87.8 wt% BCTMP fiber. The concentration of the resulting fiber pulp was adjusted to the target concentration of 1.6%. Finally, SDS surfactant was added to the fiber pulp, and the mixture was mixed under high-shear conditions for 5 minutes to produce foam with a foam density in the range of 300-400 g / L. No MFC or starch was added in the control sample. The top and bottom layers of both the control and test samples had the same fiber composition, consisting of chemical pulp, AKD, and PAE. A three-layer molded fiber product was prepared using this three-fiber composition by foaming, dehydration, and hot pressing in a mold.

[0315] Sample D and control sample D The preparation method of sample D was basically the same as that of sample B, but the solid content of the MFC suspension added to the top layer was 10%. The amount of MFC added was controlled so that the total dry fiber content of MFC in the pulp was 10 wt% and that of kraft paper fiber was 90 wt%. No MFC was added to the control sample.

[0316] Table 1 lists the properties of the foaming compositions containing the MFC layer.

[0317] Table 1: Properties of foam compositions containing MFC layers.

[0318]

[0319] It was observed that adding MFC to the fiber composition improved foam stability and reduced turbidity.

[0320] Tables 2 and 3 list the properties of the obtained three-layer molded products.

[0321] Cobb value was determined using water and olive oil, respectively. Except for the liquid volume being 10 ml and poured into a 10 square centimeter area, all other measurement procedures were performed according to ISO 535.

[0322] The water contact angle was measured using a KRÜSS portable surface analyzer in 0.1 seconds.

[0323] Measurements were performed under standard conditions as specified in ISO 187.

[0324] Table 2. Performance of three-layer molded products.

[0325]

[0326] Table 3: Performance of three-layer molded products.

[0327]

[0328] It was observed that the barrier properties of the product were improved after adding MFC to the fiber composition, which may be due to the improvement in retention and sizing performance.

[0329] In addition, adding MFC to the fiber composition also improves the strength of the product.

[0330] Adding MFC to the fiber composition significantly improved the oil resistance of the product.

[0331] It should be understood that the embodiments of the present invention disclosed herein are not limited to the specific structures, process steps, or materials disclosed herein, but extend to equivalents recognized by those skilled in the art. It should also be understood that the terminology used herein is for describing specific embodiments only and is not intended to be limiting.

[0332] The terms "an embodiment" or "an implementation" used in this specification refer to specific features, structures, or characteristics associated with that embodiment that are included in at least one embodiment of the invention. Therefore, phrases such as "in an embodiment" or "in an implementation" appearing throughout this specification do not necessarily refer to the same embodiment.

[0333] In this specification, for convenience, multiple items, structural elements, constituent elements, and / or materials may be listed in the same list. However, these lists should be understood as follows: each item in the list is individually identified as a separate and distinct item. Therefore, unless otherwise stated, any single item in a list should not be considered a substantial equivalent of other items in the same list simply because the items are listed in the same group. Furthermore, various embodiments and examples of the invention, as well as alternatives to its components, may be mentioned herein. It should be understood that such embodiments, examples, and alternatives should not be construed as factual equivalents of each other, but should be regarded as independent and autonomous expressions of the invention.

[0334] Furthermore, the features, structures, or characteristics described herein may be combined in any suitable manner in one or more embodiments. Numerous specific details, such as examples of length, width, shape, etc., are provided in the following description to provide a full understanding of embodiments of the invention. However, those skilled in the art will recognize that the invention may be practiced without including one or more of these specific details, and may employ other methods, components, materials, etc. In other instances, well-known structures, materials, or operations have not been shown or described in detail to avoid obscuring various aspects of the invention.

[0335] While the foregoing examples illustrate the principles of the invention in one or more specific applications, it will be apparent to those skilled in the art that numerous modifications can be made to the form, use, and details of implementation without requiring inventive thinking and without departing from the principles and concepts of the invention. Therefore, the invention should not be limited except as defined by the claims set forth below.

[0336] In this specification, the verbs "compose of" and "comprising" are used as open-ended qualifiers, neither excluding nor requiring the presence of features not listed. Unless otherwise expressly stated, the features listed in the dependent claims can be freely combined. Furthermore, it should be understood that the use of "a" or "an" (i.e., the singular form) in this specification does not exclude the plural form.

[0337] Industrial applicability This invention has industrial applicability, at least in the manufacture of molded fiber products.

[0338] abbreviations SDS Sodium dodecyl sulfate PVA (Polyvinyl alcohol) AKD alkyl ketene dimer PAE polyamide-epoxychloropropane MFC microfibrillated cellulose APG alkyl polyglycosides CTMP chemical thermomechanical plasma BCTMP Bleached Chemical Thermomechanical Pulp Reference tag list 101 First fiber layer 102 Second fiber layer 103 Inner Fiber Layer

Claims

1. A method comprising: A first fiber composition and a second fiber composition are provided, each independently comprising cellulose fibers and water; Fibrous fibers and a foaming agent are added to at least one fiber composition in any order, wherein the fibrillated fibers are added in the form of an aqueous suspension with a concentration of at least 2%; At least one of the first fiber composition and the second fiber composition is foamed; In a mold, the first fiber composition and the second fiber composition are shaped and dehydrated to obtain a first fiber layer and a second fiber layer with a stacked structure, respectively; and Hot pressing is performed on the shaped and dehydrated stack containing the first and second fiber layers to obtain a molded multilayer fiber product.

2. The method according to claim 1, wherein, At least one of the fiber compositions contains at least 1 wt%, such as at least 5 wt%, such as 5 to 15 wt% fibrillated fibers, such as microfibrillated cellulose (MFC), the content being calculated based on the dry weight of the cellulose fibers.

3. The method according to any one of the preceding claims, wherein the fiber composition for the outermost fiber layer, such as the uppermost fiber layer, comprises fibrillated fibers.

4. The method according to any one of the preceding claims, wherein, The method also includes activating the fibrillated fibers, the activation including improving the accessibility of the fibrillated fibers to the interaction of cellulose with solvents and / or chemical reactants and / or other fiber ingredient components.

5. The method according to any one of the preceding claims, wherein, The activation includes increasing the specific surface area of ​​the fibrillated fibers through mechanical treatment, such as exposing the fibrillated fibers to mechanical shear forces or high-shear stirring, or through alkali treatment.

6. The method according to any one of the preceding claims, wherein, The activation includes high-shear mixing during the foaming process.

7. The method according to any one of the preceding claims, comprising: - Add fibrillated fibers to the fiber composition. - Optionally, the fiber composition may be subjected to high-shear mixing, particularly in order to at least partially activate the fibrillated fibers. - Add a foaming agent to the fiber composition. - The fiber composition is subjected to high-shear mixing to foam the fiber composition and activate the fibrillated fibers.

8. The method according to any one of the preceding claims, wherein, The fibrillated fibers can improve the retention rate of wet-end additives in the fiber layer.

9. The method according to any one of the preceding claims, wherein, The fibrillated fibers can improve the oil resistance of the fiber layer.

10. The method according to any one of the preceding claims, wherein, The fibrillated fibers are selected from the following group: microfibrillated cellulose (MFC), nanofibrillated cellulose (NFC), microcrystalline cellulose (MCC), nanocrystalline cellulose (NCC), cellulose microfibrils (CMF), cellulose nanofibrils (CNF), cellulose nanocrystals (CNC), cellulose nanofibers, and any combination thereof.

11. The method according to any one of the preceding claims, wherein, fibrillated fibers comprise microfibrillated cellulose prepared from wood fibers, such as wood pulp, like chemical pulp and / or mechanical pulp, which may be bleached or unbleached.

12. The method according to any one of the preceding claims, wherein, The fibrillated fiber has a Schubert-Regler value of at least 90.

13. The method according to any one of the preceding claims, wherein, The average aspect ratio of the fibrillated fibers is at least 5, for example at least 10, for example at least 30, for example at least 50, for example at least 70, for example at least 90.

14. The method according to any one of the preceding claims, in, The minimum size of fibrillated fibers is less than 5µm, for example, in the range of 2nm to 1µm, and The longest dimension of fibrillated fibers, typically the average length, is less than 500µm, for example, in the range of 100nm to 500µm.

15. The method according to any one of the preceding claims, wherein, The method includes: A first fiber composition, a second fiber composition, and one or more other fiber compositions are provided, each composition independently comprising cellulose fibers and water; Add fibrillated fibers and a foaming agent to at least one fiber composition in any order, wherein the fibrillated fibers are added in the form of an aqueous suspension with a concentration of 2% to 20%; Foaming the fiber composition comprising at least one of the fibrillated fibers and a foaming agent; In a mold, the first fiber composition, the second fiber composition, and one or more other fiber compositions are shaped and dehydrated to obtain a first fiber layer, a second fiber layer, and one or more inner fiber layers in a stacked configuration; and A stack comprising the first fiber layer, the second fiber layer, and one or more inner fiber layers located therebetween is hot-pressed to obtain a molded multilayer fiber product.

16. The method according to any one of the preceding claims, wherein, The method includes: Foaming agents are added independently to each fiber composition. Foaming each fiber composition, and In a mold, each foamed fiber composition is shaped.

17. The method according to any one of the preceding claims, wherein, The density of the foam ranges from 100 to 700 kg / dm³. 3 Within the range, for example, 300 to 400 kg / dm 3 .

18. The method according to any one of the preceding claims, wherein, The stability of the foam is in the range of 10 to 400 ml, for example 20 to 300 ml, for example 50 to 250 ml, for example 60 to 200 ml, which is measured based on the volume of water separated from 1 liter of foam volume in 10 minutes.

19. The method according to any one of the preceding claims, wherein, The turbidity of the foam is in the range of 0 to 550 NTU, for example 2 to 300 NTU, for example 3 to 200 NTU, for example 5 to 100 NTU.

20. The method according to any one of the preceding claims, wherein the foaming agent is selected from the group consisting of sodium dodecyl sulfate (SDS), polyvinyl alcohol (PVA), alkyl polyglycosides (APG), glycine salts, glucamide, and any combination thereof.

21. The method according to any one of the preceding claims, wherein, Cellulose fibers comprise wood pulp selected from the group consisting of chemical pulp, mechanical pulp, and any combination thereof.

22. The method according to any one of the preceding claims, wherein, At least one of the fiber compositions, preferably at least the uppermost fiber layer, wherein the cellulose fibers are pulped to achieve a Schubert-Riegel number of at least 40, for example at least 45, for example at least 52, for example at least 60, for example at least 65.

23. The method according to any one of the preceding claims, wherein, The fiber composition containing fibrillated fibers also includes one or more additives selected from the group consisting of sizing agents, starch, wet strength agents, retention aids, and any combination thereof.

24. The method according to any one of the preceding claims, wherein, The fiber composition containing fibrillated fibers also contains additives that have an affinity for cellulose fibers, such as an affinity for anionic groups / sites in cellulose fibers.

25. The method according to any one of the preceding claims, wherein, At least one of the fiber compositions, preferably a fiber composition for an inner fiber layer, comprises microfibrillated cellulose, starch, and a sizing agent.

26. The method according to any one of the preceding claims, wherein, The hot pressing includes pressing the stack between two forming plates, wherein the temperature of at least one, preferably both plates, is not lower than 150°C, for example, 150 to 270°C, for example, 180 to 250°C, for example, 190 to 225°C.

27. The method according to any one of the preceding claims, wherein, In each fiber composition, independently of each other, at least 80 wt%, for example at least 95 wt%, of the cellulose fibers are derived from perennial and / or annual plants, such as wood, such as wood pulp, based on the total dry weight of the cellulose fibers.

28. A molded multilayer fiber product, comprising: First fiber layer; Second fiber layer; as well as Optionally, at least one inner fiber layer is located between the first fiber layer and the second fiber layer. Each layer of fiber independently contains a type of cellulose fiber material. At least one of the fiber layers comprises fibrillated fibers. The fiber layer, which contains at least fibrillated fibers, preferably all fiber layers of the product, is produced by a foam molding method in a mold. In this process, the fibrillated fibers are activated by high-shear mixing during the foaming process of the foam forming method.

29. The molded multilayer fiber product according to claim 28, wherein, The at least one fiber layer contains at least 1 wt%, for example at least 5 wt%, specifically 5 to 15 wt%, of fibrillated fibers, the content of which is calculated based on the dry weight of the cellulose fibers.

30. The molded multilayer fiber product according to any one of claims 28 to 29, wherein, At least one of the fiber layers comprises fibrillated fibers and an additive with affinity for cellulose fibers, such as an additive with affinity for anionic groups / sites in cellulose fibers.

31. The molded multilayer fiber product according to any one of claims 28 to 30, wherein, The additive content in the fiber layer is at least 0.1 wt%, for example at least 1 wt%, for example at least 5 wt%, calculated based on the dry weight of the fiber.

32. The molded multilayer fiber product according to any one of claims 28 to 31, in, The first fiber layer and the second fiber layer are the outermost fiber layers of the product, and The outermost fiber layer, such as the uppermost fiber layer, contains fibrillated fibers, and preferably all other fiber layers are substantially free of fibrillated fibers.

33. The molded multilayer fiber product according to any one of claims 28 to 32, wherein, Of the total dry weight of each fiber layer, at least 50 wt%, for example at least 70 wt%, for example at least 80 wt%, is derived from cellulose fibers derived from perennial and / or annual plants, such as wood pulp. It is composed of independent fiber layers.

34. The molded multilayer fiber product according to any one of claims 28 to 33, wherein: The first fiber layer, i.e., the uppermost fiber layer, comprises chemical pulp and microfibrillated cellulose. The inner fibrous layer contains CTMP or BCTMP, and The second fiber layer, which is the bottommost fiber layer, contains chemical pulp.

35. The molded multilayer fiber product according to any one of claims 28 to 34, wherein, The density of the molded multilayer fiber product is at least 200 kg / m³. 3 For example, in the range of 200 to 900 kg / m 3 Within the range, for example, 500 to 850 kg / m 3 Calculated based on the weight of dry solids per unit volume.

36. The molded multilayer fiber product according to any one of claims 28 to 35, for use as food or liquid packaging, food or liquid container products or components thereof, or for use in the packaging, containerization, storage, cooking and / or heating of food or liquid.

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