Cellulose foam

Abstract

The present invention relates to a cellulose foam comprising a microfibrillated cellulose material, at least one gelling agent and at least one plasticiser, which foam is lightweight, porous, flexible, robust, thermally stable, moisture-resistant and biodegradable / compostable, possesses thermal insulation properties and can be moulded into any shape, and thus constitutes a natural, sustainable and non-synthetic alternative to petroleum-based foams. The invention also relates to a process for producing the cellulose foam.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: CELLULOSIC FOAM

[0003] TECHNICAL DOMAIN

[0004] The present invention relates to a cellulosic foam and a process for its production.

[0005] PREVIOUS TECHNIQUE

[0006] Foams are everyday materials used in various applications such as packaging, cosmetics, cleaning products, and construction. However, they are mostly manufactured from fossil-based polymers, such as polyurethane and polystyrene, and are therefore neither renewable nor biodegradable.

[0007] A more sustainable alternative is polylactic acid (PLA) foam. This option has become popular in the last decade because PLA is a naturally occurring, biodegradable polymer that can be used to form various plastic-like materials, including foams. However, PLA is only biodegradable under specific industrial conditions, as it takes at least 80 years to fully degrade in a normal landfill environment, therefore it cannot be considered compostable. Therefore, it is necessary to develop more sustainable alternatives.

[0008] Similarly, among other widespread options, cellulose-based foams appear promising, since cellulose is an abundant, renewable, and economical raw material with unique chemical and mechanical characteristics. US patent 10450435 B2 describes a process for producing sponges and foams from cellulose fibers, involving the treatment of cellulose fibers with periodate to transform them into dialdehyde cellulose fibers. After adjusting the pH to a specific range, the fibers are frozen and thawed to create a three-dimensional structure, which constitutes the sponge or foam. The material produced can also be modified through simple chemical modification pathways to have different properties and be used in various applications, such as thermal and / or acoustic insulation, packaging, and protective equipment.

[0009] Patent application WO2018177878A1 describes the possibility of producing lightweight, porous cellulose structures from suspensions of microfibrillated cellulose in water by adding water-soluble salt particles of a predetermined size, such as sodium chloride, to said suspension to aid in pore formation. The porous structure is then stabilized by conventional oven drying, followed by leaching of the water-soluble salt from the dried and cured microfibrillated cellulose foam. The resulting porous materials are lightweight and can be adapted for specific applications, particularly applications where polyurethane foams are commonly used.

[0010] Patent application US20200392301A1 describes the production of an ultralight foam by mixing nanocellulose with a water-soluble polymer, such as polyvinyl alcohol, polyethylene glycol, or polyacrylic acid, and a crosslinking agent, such as 1,2,3,4-butanetetracarboxylic acid, oxalic acid, or succinic acid. The foam can be made by freeze-drying or freeze-drying, in which the mixture is frozen and then the water is removed. Patent application WO2014011112A1 describes a method for producing a hydrophobized nanofibrillated cellulose foam, which involves reacting said nanofibrils with a hydrophobic amine, forming a foam by introducing a gas into said aqueous dispersion, and drying the resulting foam without resorting to freeze-drying. The resulting foam exhibits high porosity and a good pore size distribution, a prerequisite for application in insulation products.

[0011] Patent application US20220389659A1 describes a microfibrillated cellulose foam, thickening agents such as, for example, polyvinyl alcohol, polyacrylic acid or polyacrylamide, and / or at least one adhesive biopolymer, such as egg white protein. The foam can be molded into any shape, is environmentally friendly and can be produced economically. The method of producing the foam is described as agitating and pressurizing a suspension with the components in a foam-forming apparatus, where gas is applied to it. Finally, the suspension is discharged through an outlet of the foam-forming apparatus to form the microfibrillated cellulose foam.

[0012] The current state of the art shows a lack of solutions for cellulosic foams that do not comprise compounds of fossil origin, but are nevertheless lightweight, porous, flexible, robust, thermally stable and / or possess thermal insulation properties, without compromising their biodegradability / compostability profile, are easy to produce and have a competitive cost. SUMMARY OF THE INVENTION

[0013] The present invention relates to a cellulosic foam comprising 10-60% w / w of a microfibrillated cellulosic material, 5-45% w / w of at least one gelling agent and 20-65% w / w of at least one plasticizer.

[0014] In a preferred embodiment of the invention, the cellulosic foam further comprises 0.1-3% w / w of at least one crosslinking agent.

[0015] In a preferred embodiment of the invention, the cellulosic foam further comprises 0.1-5% w / w of at least one hydrophobic additive.

[0016] In a preferred embodiment of the invention, the cellulosic foam further comprises 0.1-3% w / w of at least one crosslinking agent and 0.1-5% w / w of at least one hydrophobic additive.

[0017] In a preferred embodiment of the invention, the cellulosic foam consists of 13.1% w / w of at least one gelling agent, 41.8% w / w of microfibrillated cellulosic material, 32.6% w / w of at least one plasticizer, 0.6% w / w of at least one crosslinking agent, and 1.3% w / w of at least one hydrophobic additive, the remaining percentage being water.

[0018] In a preferred embodiment of the invention, the microfibrillated cellulosic material is selected from the group consisting of microfibrillated Kraft pulp cellulosic material, high-yield microfibrillated Kraft pulp cellulosic material, unbleached microfibrillated Kraft pulp cellulosic material, bleached microfibrillated Kraft pulp cellulosic material, semi-bleached microfibrillated Kraft pulp cellulosic material, sulfite pulp cellulosic material, unbleached microfibrillated sulfite pulp cellulosic material, bleached microfibrillated sulfite pulp cellulosic material, semi-bleached microfibrillated sulfite pulp cellulosic material, and combinations thereof.

[0019] In a preferred embodiment of the invention, Kraft cellulose pulps are eucalyptus cellulose pulps.

[0020] In a preferred embodiment of the invention, the gelling agent is selected from the group consisting of sodium alginate, xanthan gum, gum arabic, and combinations thereof.

[0021] In a preferred embodiment of the invention, the plasticizer is selected from the group consisting of polyvinyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, glycerol, sorbitol, polyols and combinations thereof.

[0022] In a preferred embodiment of the invention, the crosslinking agent is selected from the group consisting of zinc chloride, magnesium chloride, calcium chloride, potassium chloride, aluminum trichloride, iron chloride, aluminum sulfate, copper sulfate, nickel sulfate, epichlorohydrin, glutaraldehyde, citric acid and combinations thereof. In a preferred embodiment of the invention, the hydrophobic additive is selected from the group consisting of alkyl ketene dimer, alkenyl succinic anhydride, oils, waxes, resins, rosin and combinations thereof.

[0023] In a preferred embodiment of the invention, the gelling agent is sodium alginate, the plasticizer is glycerol, the crosslinking agent is zinc chloride, and the hydrophobic additive is alkyl ketene dimer.

[0024] Another aspect of the present invention is the process for producing cellulose foam.

[0025] The process comprises the following steps:

[0026] a) constitution of an aqueous formulation comprising 0.25-3% w / w of a microfibrillated cellulosic material, 0.25-2% w / w of at least one gelling agent and 1-3% w / w of at least one plasticizer;

[0027] b) stirring the resulting formulation from step a) at room temperature until a hydrogel is formed; c) dispensing the hydrogel resulting from step b) into molds;

[0028] d) drying the hydrogel resulting from step c) by means of freeze-drying until the total removal of the initial water volume and formation of the cellulose foam.

[0029] In a preferred embodiment of the invention, the process further comprises, after step b) and before step c), a step of adding 0.02-0.08% w / w of a crosslinking agent to the hydrogel resulting from step b) by homogenization and at room temperature until a hydrogel is formed.

[0030] In a preferred embodiment of the invention, the formulation of step a) further comprises 0.01–0.15% w / w of at least one hydrophobic additive.

[0031] In a preferred embodiment of the invention, the formulation of step a) further comprises 0.01-0.15% w / w of at least one hydrophobic additive, and after step b) and before step c) there is a further step of adding 0.02-0.08% w / w of a crosslinking agent to the hydrogel resulting from step b) by homogenization and at room temperature until a hydrogel is formed.

[0032] BRIEF DESCRIPTION OF THE FIGURES

[0033] Figure 1. Schematic representation of the gradual organization of cellulose in the wood fiber wall. A-Cross-section / longitudinal section of wood fibers; B-Fiber fraction formed by macrofibrils; C-Macrofibrils; D-Microfibrils; E-Elementary fibril; F-Set of elementary crystallites; G-Organization of cellulose molecules: the crystalline unit or unit cell (Krassig, HA, "The Fiber Structure", Cellulose, Structure, Accessibility and Reactivity, Gordon and Breach Science Publishers, Polymer Monographs Vol. 11, Yverdon, Switzerland, 1993, Chapter 2, pp. 6-4; Parham, RA, "Ultrastructure and Chemistry", Pulp and Paper Manufacturers, Vol. 1: Properties of Fibrous Raw Materials and their Preparation for Pulping, MJ Kocurek and F. Stevens (eds.), Canadian Pulp and Paper Association, Canada, 1983, Chapter 2, pp. 6-4.

[0034] Figure 2. Transmission optical microscope images of cellulose fibers without mechanical treatment (a) and after refining (b) and (c).

[0035] Figure 3. Images of the compostability tests performed.

[0036] DETAILED DESCRIPTION OF THE INVENTION

[0037] The present invention surprisingly provides a cellulosic foam based on abundant natural resources, without fossil-based products in its composition, which proves to be lightweight, porous, flexible, robust, thermally stable, moisture-resistant, biodegradable / compostable, with thermal insulation properties and the ability to be molded into any shape—properties normally seen only in similar products based on fossil-derived components. In fact, the cellulosic foam of the present invention, based on a microfibrillated cellulosic material (MCM), at least one gelling agent, and at least one plasticizer, is an unexpected and innovative product, since the expert would not expect to obtain a foam with the described properties, but rather a material with low porosity, compact, fragile, and with poor thermal and mechanical performance.

[0038] The cellulose foam of the present invention is also easily adaptable to customized designs, with the added possibility of functionalization for unlimited extra features. The foam of the present invention can thus be used in different applications such as packaging, thermal insulation, electronics, and medical and / or stimulus-sensitive devices. In fact, the base formulation of the foam of the present invention is also compatible with 3D extrusion printing and other differentiation processes for the development of intelligent applications based on sensors, stimulus-responsive devices, or energy storage.

[0039] For the first time, and in this invention, polysaccharides that are used in the pharmaceutical and food industries, already established in the market, easily accessible and available in large quantities, surprisingly constitute the cellulose foam that is the scope of the present invention.

[0040] Furthermore, the foam of the present invention is mostly based on cellulose, a natural, abundant, versatile, biodegradable and renewable polymer with excellent chemical and mechanical properties. Cellulose fibers, in particular, can form various types of structures and materials that can be adapted to market needs.

[0041] Thus, the present invention involves the use of a microfibrillated cellulosic material, produced from cellulose pulp fibers, as a bio-based raw material to design a new sustainable and high-performance cellulosic foam that is an alternative to petroleum-based foams. The microfibrillated cellulosic material exhibits relevant chemical and mechanical properties, which can act alone or in combination with other natural and renewable materials to form robust networks. Furthermore, an MCM production line can be easily adapted to an industrial cellulose pulp production unit.

[0042] Additionally, when in the presence of at least one crosslinking agent or at least one hydrophobic additive, the cellulosic material of the present invention exhibits a robust structure without compromising its lightness, porosity, flexibility, thermal stability, biodegradability, and thermal insulation properties, with improved moisture resistance.

[0043] Additionally, when in the presence of at least one crosslinking agent and at least one hydrophobic additive, the cellulosic foam of the present invention exhibits a very robust structure without compromising its lightness, porosity, flexibility, thermal stability, biodegradability, and thermal insulation properties, with an improved hydrophobic character (greater angle of contact with water).

[0044] Another aspect of the present invention is the process for producing cellulosic foam, which is simple, water-based (without organic solvents or petroleum-derived products), and does not require the use of toxic or polluting chemicals.

[0045] The cellulosic foam of this invention solves the problems of the prior art, consisting of a naturally based, biodegradable and compostable cellulosic foam with excellent performance and composed of readily available and abundant compounds. In particular, the microfibrillated cellulosic material can be produced on a larger scale when integrated into existing industrial units for the production of pulp and paper. Within the scope of the present invention, and according to the definition provided by IUPAC, a foam is characterized as a dispersion in which a large proportion of gas by volume is dispersed in a solid, in the form of gas bubbles (see IUPAC, 1972, 31, 577: Manual of Symbols and Terminology for Quantities and Physical Units, Appendix II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry, on page 606).

[0046] Within the scope of the present invention, the term "cellulosic foam" refers to a foam composed of cellulose fibers, wherein these fibers result from the treatment of a cellulose pulp by any chemical, biological or mechanical process for that purpose, or by a combination of these three approaches. In turn, cellulose pulps are obtained by disintegrating the three-dimensional structure of wood and individualizing the cellulose fibers that constitute its matrix. Generally, this can be done in two ways, mechanically or chemically, or by a combination of these two approaches.

[0047] Within the scope of the present invention, the term "formulation" refers to a mixture of materials that compose it, as well as to reaction products and decomposition products formed from the materials of the composition.

[0048] Within the scope of the present invention, the mass ratio of the aqueous formulation refers to the quotient between the mass of a compound in the formulation and the total mass of the formulation:

[0049] Mass ratio, % m / m = (mass of compound in the formulation / total mass of the formulation x 100) where the mass ratio of the aqueous formulation is made up of water.

[0050] Within the scope of the present invention, the composition of the cellulose foam refers to the ratio between the mass of a compound in the cellulose foam and the total mass of the cellulose foam:

[0051] Composition of cellulose foam, % w / w = (mass of compound in cellulose foam / total mass of cellulose foam*) x 100

[0052] * in equilibrium with the relative humidity of the environment (a measure of the amount of water vapor present in the air in relation to the maximum amount that the air could contain at the same temperature)

[0053] The total and final mass of the cellulose foam includes the mass of all compounds present in the initial formulation and a mass of water that is acquired according to the ambient relative humidity.

[0054] Within the scope of the present invention, a gelling agent refers to, for example, polysaccharides, that is, macromolecular polymers composed of complex carbohydrates, including at least ten monosaccharides linked by glycosidic bonds that may be linear or branched.

[0055] Within the scope of the present invention, sodium alginate is a natural hydrophilic polysaccharide derived from and isolated from brown seaweed. Due to its biocompatible and biodegradable nature, it is commonly used in the field of drug delivery. It is also frequently used as a food additive, gelling agent, emulsifier, and stabilizer.

[0056] Within the scope of the present invention, xanthan gum is a polysaccharide secreted by the bacterium Xanthomonas campestris. It is composed of repeating units of pentasaccharides, including glucose, mannose, and glucuronic acid. It is also used as a stabilizer and thickening agent in a wide range of food, beverage, and pharmaceutical applications.

[0057] Within the scope of the present invention, gum arabic is a complex, naturally occurring, branched-chain polysaccharide found in the stems and branches of acacia trees. Gum arabic is widely used in the food and pharmaceutical industries (e.g., emulsification, texture control, and flavor encapsulation).

[0058] Within the scope of the present invention, a plasticizer refers to the class of organic compounds belonging to the alcohol family, in which in the glycol molecule two hydroxyl groups (-OH) are attached to different carbon atoms.

[0059] Within the scope of the present invention, a crosslinking agent is an additive that links two polymer chains through a covalent or ionic bond.

[0060] Within the scope of the present invention, hydrophobic additives refer to additives added to enhance hydrophobic properties.

[0061] Within the scope of the present invention, a Kraft cooking process refers to Kraft cooking or sulfate cooking. This is a well-known chemical process in the art that consists of cooking wood in a cooking liquor usually composed of sodium hydroxide and sodium sulfide, at temperatures of the order of 140 to 180 °C, in pressurized reactors. A conventional Kraft process is understood here as a typical chemical cooking process that yields a pulp production rate of about 45-55%.

[0062] Within the scope of the present invention, Kraft cellulose pulp refers to a cellulose pulp obtained by conventional Kraft cooking.

[0063] Within the scope of the present invention, high yield corresponds to yields > 60% within the context of a Kraft cooking chemical process.

[0064] Within the scope of the present invention, the cooking yield is calculated using the following formula:

[0065] dough / wood dough × 100

[0066] (weights on a completely dry basis)

[0067] Thus, within the scope of the present invention, a high-yield Kraft cooking process corresponds to a Kraft chemical cooking process where yields > 60% are obtained.

[0068] Within the scope of the present invention, high-yield Kraft pulp refers to Kraft pulp produced through a Kraft cooking process with a yield greater than > 60%. Within the scope of the present invention, unbleached Kraft pulp corresponds to Kraft pulp that is not subjected to any bleaching process, that is, any process of removing residual lignin and contaminants from the pulp after its Kraft cooking.

[0069] Within the scope of the present invention, a bleached Kraft pulp corresponds to a Kraft pulp that is subjected to at least one bleaching process until it reaches an ISO (ISO 2470) brightness of ≥ 90%. The bleaching step aims to continue the delignification by the action of oxidizing agents, such as oxygen, chlorine dioxide and hydrogen peroxide.

[0070] Within the scope of the present invention, a semi-bleached Kraft pulp corresponds to a pulp that is subjected to at least one bleaching process until it reaches an ISO whiteness (ISO 2470) between that of unbleached pulp and that of bleached pulp.

[0071] Within the scope of the present invention, sulfite cooking refers to a well-known process in the art consisting of cooking wood with sulfites or bisulfite salts of sodium, calcium, potassium, magnesium, and ammonium. Solutions of these sulfites or bisulfites are used to treat wood chips, leading to the cleavage of the chemical bonds between cellulose and lignin. During this process, lignin is converted into soluble lignosulfonates, and this compound is then easily separated from the cellulose fibers. Within the scope of the present invention, sulfite pulp refers to a cellulose pulp obtained by sulfite cooking.

[0072] Within the scope of the present invention, an unbleached sulfite pulp corresponds to a sulfite pulp that is not subjected to any bleaching process, that is, any process of removing residual lignin and contaminants from the pulp after its sulfite cooking.

[0073] Within the scope of the present invention, a bleached sulfite pulp corresponds to a sulfite pulp that is subjected to at least one bleaching process until it reaches an ISO (ISO 2470) whiteness of ≥ 90%. The bleaching step aims to continue the delignification by the action of oxidizing agents, such as molecular oxygen, chlorine dioxide and hydrogen peroxide.

[0074] Within the scope of the present invention, a semi-bleached sulfite pulp corresponds to sulfite pulp that is subjected to at least one bleaching process until it reaches an ISO whiteness (ISO 2470) between that of unbleached pulp and that of bleached pulp.

[0075] Wood and plant fibers are morphological cellular elements. As plant cells, wood and plant fibers possess a cell wall. The cell wall presents a structural hierarchy that begins with the cellulose chain, hence the specific designation of cellulosic fiber, due to its composition being mainly cellulose, a linear polysaccharide composed of O-D-glucopyranose units, and may also include other polysaccharides and lignin. Cellulose chains group together to form elementary cellulosic fibrils. In turn, elementary fibrils group together, and the resulting unit from each group of elementary fibrils is designated as a cellulosic microfibril. The orientation of the microfibril in the cell wall relative to the cell axis is one of the factors that allows the differentiation of the cell wall into distinct layers (Figure 1).Microfibrils are obtained by fibrillating cellulosic fibers, in which the microfibril is physically detached from the cellulosic fiber. This occurs when cellulosic fibers from wood and plants, obtained from a cellulose pulp of cellulosic fibers (the pulp being obtained by disaggregating the three-dimensional structure of the wood and individualizing the cellulose fibers that constitute its matrix – this disaggregation can be carried out by three methods: mechanical, chemical, biological, or enzymatic, or by any combination of these methods), are mechanically treated, preceded or not by at least one other auxiliary treatment (chemical, enzymatic treatments, or any combination of these treatments).This fibrillation can be complete, that is, with physical separation of a microfibril or set of microfibrils from the cell wall along its entire longitudinal dimension, or the fibrillation can be partial, resembling a branching, which may involve a microfibril or a set of microfibrils from each cellulosic fiber. The two fibrillation processes can coexist and may not encompass the entirety of the fibers. Also resulting from fibrillation is material resulting from microfibrils cut longitudinally at points of greater fragility, resulting in fractions of shorter length than the fiber or fibril that originated them.

[0076] Thus, within the scope of the present invention, a microfibrillated cellulosic material refers to the cellulosic material resulting from treatments of cellulose pulps for their fibrillation. In fact, the term microfibrillated has the associated effect on the fiber that promotes the (partial or total) separation of microfibrils from the cell wall from which they originated.

[0077] The term "cellulosic material" is associated with its fibrous and cellulosic origin, but it must be distinguished from cellulosic fiber, a plant cell, due to the changes resulting from its processing, as this compromises the structural hierarchy underlying the concept of a plant cell.

[0078] Processes for fibrillating cellulosic fibers consist of processes that result in the application of compression and shear forces in an aqueous medium, also causing the cellulosic fibers to swell. The specialist in the technique has various techniques and means to promote the mechanical treatment of cellulosic fibers in order to promote their fibrillation. Examples of this type of mechanical process are refining, grinding, maceration, and shearing. Additionally, cellulosic fibers can be pre-treated enzymatically or chemically, for example, to reduce the amount of hemicellulose or lignin and / or to create zones more susceptible to the action of subsequent mechanical treatments, thus making them more targeted and effective.

[0079] The Shopper-Riegler (SR) degree, which reflects the drainage rate of a given volume of water through a suspension of a cellulose fiber pulp, is one of the first parameters to be measured in microfibrillated cellulosic material and compared with the cellulose pulp from which it originated through processing that promotes fibrillation. It corresponds to an empirical measure of cellulose pulp refining, in which a quantity of 1000 mL corresponds to 0 o SR, while a zero amount of drained liquid corresponds to 100°SR (ISO 5267 / 1).

[0080] Other parameters relevant to identifying the effect of fibrillation on cellulosic fibers are the morphological parameters of the resulting microfibrillated cellulosic material, herein referred to as fibrillation parameters, such as the average fibril length, the average fibrillar area %, the average fibrillar perimeter %, and the total fines content %, parameters in accordance with ISO 16065-2 (Pulps - Determination of fiber length by automated optical analysis. Part 2: Unpolarized light method). The equipment used for these measurements, and within the scope of the present invention, was the L&W FiberTester Plus+, in which the characterization of the microfibrillated cellulosic material is performed without requiring prior sample treatment, allowing analysis in aqueous medium, a medium in which the material is applied within the scope of this invention.

[0081] The percentage of fines also refers to the percentage of fibers with a length less than or equal to 0.2 mm, measured using an L&W Fiber Tester Plus+, relative to the average length of the entire sample.

[0082] Indeed, the effect of fibrillation on the production of microfibrillated cellulosic material is observed in the final product when compared to cellulosic fibers that are not subjected to fibrillation for the production of a microfibrillated cellulosic material, as observed in the images in Figure 2 (using a transmission optical microscope (Leica brand, Dialux 20EB model)).Figure 2 represents in a) a cellulosic fiber obtained after Kraft cooking of eucalyptus followed by a bleaching process, without refining (Shopper-Riegler degree of 20 °SR, average fibril length 0.807 mm, total fines content 17%, average fibrillar area 0.8% and average fibrillar perimeter 1.6%), in b) a microfibrillated cellulosic material obtained from a mechanical treatment of bleached Kraft eucalyptus pulp (Shopper-Riegler degree of 74 °SR, average fibril length 0.707 mm, total fines content 23%, average fibrillar area 3% and average fibrillar perimeter 8%) and in c) a microfibrillated cellulosic material obtained from a mechanical treatment of unbleached Kraft eucalyptus pulp (Degree Shopper-Riegler above 70°SR, average fibril length 0.693 mm, total fines content 48%, average fibrillar area 20%, and average fibrillar perimeter 36%).That is, Figure 2, in a), b) and c), and in that order, represents an increasing degree of severity with respect to the fibrillation of a cellulose pulp for the production of a microfibrillated cellulose material. The effect of fibrillation is clearly visible in the final product, reflected both in the fibrillation parameters, which undergo a significant increase with the severity of the fibrillation applied, and visually by observing, in b) and c): 1) microfibril or set of microfibrils completely detached, or disaggregated, from the cell wall along its entire longitudinal dimension; 2) branched fiber resulting from the partial detachment of a microfibril or a set of microfibrils; 3) material resulting from microfibrils cut longitudinally at points of greater fragility, resulting in fractions of shorter length than the fiber from which they originated.

[0083] The microfibrillated cellulosic material of the present invention can further be defined by a Schopper-Riegler degree (°SR) greater than 70, an average fibril length of 0.357-0.700 mm, an average fibril width of 20-35 µm, an average fibrillar area of ​​3-32%, an average fibrillar perimeter of 8-60%, and a total fines content of 23-100% (L&W FiberTester Plus+, per ISO 16065-2 (Pulps - Determination of fiber length by automated optical analysis. Part 2: Unpolarized light method)).

[0084] The resulting microfibrillated cellulosic material also exhibits greater flexibility and a larger surface area compared to cellulosic pulp that is not subjected to any fibrillation process for the production of a microfibrillated cellulosic material.

[0085] The microfibrillated cellulosic material of the present invention may additionally be composed of nanofibrils (or nanofibers), or other cellulosic nanomaterials, as defined in the ISO / TS 20477 2023-05 standard Nanotechnologies - Vocabulary for cellulose nanomaterial, resulting from the fibrillation process of a cellulose pulp.

[0086] The microfibrillated cellulosic material of the present invention thus presents technical characteristics conferred upon it by the process for its fibrillation, these being differentiating and unequivocally identifiable in the final product. Thus, a person skilled in the art can identify and differentiate, within the scope of the present invention, a microfibrillated cellulosic material, distinguishing it from other types of cellulosic fibers.

[0087] It is also common in the field of this technique to designate microfibrillated cellulosic material according to the raw material from which it originates, that is, the type of cellulose pulp from which the material is obtained. Since it is chemically composed of the same elements as the cellulose pulp from which it originates, the intrinsic characteristics of microfibrillated cellulosic material depend directly on the process and raw material used for its production. Thus, it is impossible to characterize it through its chemical constituents, due to their similar nature. The expert in the specialty identifies the type of cellulosic material in question, and its intrinsic characteristics, by its designation based on the raw material from which it originates and the production method of the raw material and the cellulosic material.

[0088] Microfibrillated cellulosic material can be produced from Kraft pulp or from sulfite pulp of softwood and hardwood.

[0089] Within the scope of the present invention, softwood fibers refers to cellulosic fibers from woods of, but not limited to, pine, fir and their combinations.

[0090] Within the scope of the present invention, hardwood fibers refers to cellulosic fibers from, but not limited to, eucalyptus, birch, acacia, poplar and combinations thereof.

[0091] Within the scope of the present invention, a microfibrillated cellulosic material from Kraft pulp refers to a microfibrillated cellulosic material produced from Kraft pulp.

[0092] Within the scope of the present invention, a microfibrillated cellulosic material of unbleached Kraft pulp relates to a microfibrillated cellulosic material produced from unbleached Kraft pulp.

[0093] Within the scope of the present invention, a microfibrillated cellulosic material from bleached Kraft pulp relates to a microfibrillated cellulosic material produced from bleached Kraft pulp.

[0094] Within the scope of the present invention, a microfibrillated cellulosic material from semi-bleached Kraft pulp relates to a microfibrillated cellulosic material produced from semi-bleached Kraft pulp.

[0095] Within the scope of the present invention, a high-yield Kraft pulp microfibrillated cellulosic material relates to a microfibrillated cellulosic material produced from a high-yield Kraft pulp.

[0096] Within the scope of the present invention, a microfibrillated cellulosic material of sulfite cellulose pulp relates to a microfibrillated cellulosic material produced from a sulfite cellulose pulp.

[0097] Within the scope of the present invention, a microfibrillated cellulosic material of unbleached sulfite pulp relates to a microfibrillated cellulosic material produced from an unbleached sulfite pulp.

[0098] Within the scope of the present invention, a microfibrillated cellulosic material from bleached sulfite pulp relates to a microfibrillated cellulosic material produced from bleached sulfite pulp.

[0099] Within the scope of the present invention, a microfibrillated cellulosic material from semi-bleached sulfite pulp relates to a microfibrillated cellulosic material produced from a semi-bleached sulfite pulp.

[0100] Within the scope of the present invention, hydrogel refers to gel-based structures consisting of three-dimensional networks of hydrophilic polymers with high water retention capacity. They can be classified based on composition (natural vs. synthetic), physical structure (amorphous, semi-crystalline, crystalline) and type of crosslinking (ionic vs. covalent). Depending on the ratio of their formulation and degree of crosslinking, hydrogels with different properties are obtained, such as their viscosity, a crucial parameter for their performance and applicability.Additionally, hydrogels can be maintained and used in their initial form, dried at room temperature or higher to form films / layers / barriers, or dried using different techniques, such as freeze-drying or supercritical drying, to remove all water without damaging / collapsing their structure and forming porous materials with low densities, designated as aerogels, which resemble and behave like foams / sponges. Thus, in all cases, their flexibility / softness, density, and porosity are defined by their original hydrogel formulation. Some hydrogels may be flexible, soft, and brittle, while others may be more robust and / or brittle; this opens the opportunity to design these materials tailored to specific applications.

[0101] Within the scope of the present invention, a natural-based material is understood to be a material whose main constituent is a substance or substances originally derived from living organisms (e.g., plants, microorganisms), or from components thereof (e.g., enzymes), or biochemicals (i.e., chemical substances found naturally in living organisms, such as sucrose, glucose, starch, or natural polyesters).

[0102] Within the scope of the present invention, moisture resistance consists of the ability of a material to maintain its structure intact, without undergoing complete or partial disintegration or deformation, when subjected to an environment with relative humidity above 50% and / or when in direct contact with water. Within the scope of the present invention, biodegradable material refers to a material that, in contact with water, oxygen, nutrients and suitable temperature, is capable of decomposing into carbon dioxide and water through the action of microorganisms. Some biodegradable materials are compostable (but not all), meaning that they degrade under aerobic conditions, typically within a period of 6 to 12 weeks. Composting of industrial products typically occurs in industrial composting facilities, where controlled conditions are provided (e.g., temperature, humidity, aeration).Microorganisms, such as bacteria or fungi and their enzymes, are able to "digest" the chain structure of compostable polymers as a source of nutrition. The resulting end products are water, carbon dioxide (CO2), and residual biomass.

[0103] Within the scope of the present invention, compostable materials preferably meet specific compostability requirements according to at least one accepted standardization system, such as ASTM 6400, ASTM 6868, ISO 17088, ISO 18606, EN 13432, EN 14995, or at least one accepted certification system, such as certificates for compostable plastics issued by DIN Certco, Vincotte, Biodegradable Products Institute (BPI, USA), Japan BioPlastics Association (JBPA, Japan), as well as other less commonly used organizations. More particularly, these standardization and certification systems correspond to the latest version in effect on the priority date of this patent application.

[0104] In the context of the present invention, density refers to the mass of a material compared to its volume, and is calculated as follows:

[0105] Density (g / cm³) 3 ) = sample mass (g) / sample volume (cm³) 3 )

[0106] Within the scope of the present invention, porosity refers to the fraction of the volume of voids in relation to the total volume, between 0 and 1, or as a percentage between 0% and 100%, and is calculated as follows:

[0107] Porosity (%) = (pore volume / total volume) x 100 Where:

[0108] Pore ​​volume = Total volume - Volume of water in the final formulation

[0109] Within the scope of the present invention, contact angle (θ) C) refers to the angle between a liquid surface and a solid surface where and when they meet. Contact angle measurements on foam samples were performed with ultrapure water (4µL drops) in a dataphysics OCA 15EC with dpiMAX software, from which the θ values ​​were obtained. C over time (up to 150 seconds) were recorded directly.

[0110] Within the scope of the present invention, the hydrophobic character of the foams refers to their tendency to repel water molecules, which is evaluated by measuring the contact angle between a drop of water and the surface of the foams.

[0111] Within the scope of the present invention, mechanical compression tests refer to the resistance to compression that a sample of a flexible foam, standardized in terms of its dimensions, offers against a total surface compression of 25% relative to its initial height. According to ISO 3386-1.

[0112] Within the scope of the present invention, thermogravimetric analysis (TGA) refers to a method of thermal analysis in which changes in the physical and chemical properties of materials are measured as a function of increasing temperature (with a constant heating ramp) or as a function of time (with constant temperature and / or constant mass loss). The TGA curves of the foam samples were recorded on a Hitachi STA200RV (Japan) with a constant heating ramp of 10°C / min up to 800°C.

[0113] Within the scope of the present invention, the thermal insulation properties were evaluated considering the thermal conductivity, thermal diffusivity, and specific heat of the foams. The measurements were performed using the transient flat probe method in accordance with ISO standards 22007-1: 2022 and 22007-2: 2022.

[0114] Within the scope of the present invention, elemental analysis refers to an analytical technique applied in chemistry to determine the elemental composition of chemical compounds and their composites. In the case of the foam samples, the percentages of carbon (C), nitrogen (N), and oxygen (O) were evaluated using a ThermoFisher Scientific Flash 2000 (United States of America).

[0115] Within the scope of the present invention, biodegradability tests relate to compostability tests in accordance with ISO 23517: 2021, from the cultivation of catnip (Nepeta cataria) in contact with foam samples (2x2x2cm) for 12 weeks, after which their biodegradation (%) in relation to their initial mass was evaluated.

[0116] Within the scope of the present invention, lyophilization is a process of water sublimation, the transition from the solid to the gaseous state without passing through the liquid state, of a given product / formulation. It is also known as a noble dehydration process. This process allows the total or partial removal of water present in a medium without deforming its structure, unlike drying processes by heat or convection, for example, which alter the structure / morphology of the final product / material. Lyophilization is a common procedure in the production of pharmaceuticals and some foods (fruits, ready meals, animal feed, etc.). In practice, it consists of two stages: lowering the ambient temperature until the water freezes completely (to -50°C) and lowering the pressure until the water sublimates (to 0.01 mbar) in cycles of 24-72 hours, depending on the volume of water to be removed and the capacity of the lyophilizer.In some cases, a slight heating is used after the pressure is reduced to speed up the process, controlling the temperature and pressure so that the frozen water sublimates without breaking the molecular structure of the material.

[0117] Within the scope of the present invention, ambient temperature refers to a temperature between about 15 °C and about 30 °C, or more particularly between about 20 °C and about 25 °C.

[0118] The mass ratios of the components of the cellulosic foam of the present invention allow adjusting the foam properties depending on the intended application, with the gelling agents allowing the incorporation of gelling properties with the use of natural-based compounds.

[0119] The cellulosic foam of the present invention consists of at least one gelling agent, a microfibrillated cellulosic material, and at least one plasticizer, comprising 10 to 60% w / w of a microfibrillated cellulosic material, preferably 10 to 50% w / w, more preferably 20 to 60% w / w, more preferably 25 to 45% w / w and even more preferably 30 to 40% w / w. The cellulosic foam comprises 5 to 45% w / w of at least one gelling agent, preferably 10 to 45% w / w, more preferably 5 to 40% w / w, more preferably 15 to 40% w / w and even more preferably 20 to 30% w / w. Cellulosic foam comprises 20 to 65% w / w of at least one plasticizer, preferably 20 to 55% w / w, more preferably 25 to 65% w / w, more preferably 35 to 55% w / w and even more preferably 40 to 50% w / w.

[0120] In one embodiment of the invention, the cellulosic foam further comprises at least one crosslinking agent or at least one hydrophobic additive, comprising 0.1 to 3% w / w of at least one crosslinking agent, preferably 0.1 to 2% w / w, more preferably 0.5 to 3% w / w, more preferably 1 to 2.5% w / w and even more preferably 1.5 to 2% w / w. The cellulosic foam comprises 0.1 to 5% w / w of at least one hydrophobic additive, preferably 0.1 to 4% w / w, more preferably 0.5 to 5% w / w, more preferably 1 to 3% w / w and even more preferably 1.5 to 2% w / w.

[0121] In another embodiment of the invention, the cellulosic foam further comprises at least one crosslinking agent and at least one hydrophobic additive in the same compositions as the embodiments described above.

[0122] Another aspect of the present invention relates to a process for producing the cellulosic foam of the present invention. The process starts from an aqueous formulation consisting of at least one gelling agent, a microfibrillated cellulosic material, at least one hydrophobic additive, at least one plasticizer, and at least one crosslinking agent.

[0123] The formulation consists of at least one gelling agent, a microfibrillated cellulosic material, and at least one plasticizer. The formulation comprises a mass ratio of a microfibrillated cellulosic material of 0.25 to 3% w / w, preferably 0.5 to 3% w / w, more preferably 0.25 to 2% w / w, and even more preferably 0.5 to 1% w / w. The formulation comprises a mass ratio of at least one gelling agent of 0.25 to 2% w / w, preferably 0.5 to 2% w / w, more preferably 0.25 to 1.5% w / w, and even more preferably 0.5 to 1% w / w. The formulation comprises a mass ratio of at least one plasticizer of 1 to 3% w / w, more preferably 1.5 to 3% w / w, more preferably 1 to 2% w / w and even more preferably 1.5 to 2.5% w / w.

[0124] In one embodiment of the invention, the formulation further comprises at least one crosslinking agent or at least one hydrophobic additive. The formulation comprises a mass ratio of at least one crosslinking agent of 0.02 to 0.08% w / w, preferably 0.04 to 0.08% w / w, more preferably 0.02 to 0.06% w / w, and even more preferably 0.04 to 0.06% w / w. Or the formulation comprises a mass ratio of at least one hydrophobic additive of 0.01 to 0.15% w / w, preferably 0.03 to 0.15% w / w, more preferably 0.01 to 0.1% w / w, and even more preferably 0.05 to 0.1% w / w.

[0125] In another embodiment of the invention, the formulation further comprises at least one crosslinking agent and at least one hydrophobic additive in the same compositions as the embodiments described above.

[0126] The process comprises the steps of agitating the formulation at room temperature until a hydrogel is formed, followed by dispensing the resulting hydrogel into molds, and then drying the resulting hydrogel through lyophilization until all initial water volume is removed and the cellulose foam is formed.

[0127] In one embodiment of the invention, the process further comprises a step of adding at least one crosslinking agent to the hydrogel.

[0128] It is observed that these mass ratios used in the aforementioned aqueous formulation, when subjected to the production process of the present invention, result in the compositions previously disclosed for the cellulosic base material of the present invention. This is to be expected, since, after the drying stage of the process, the resulting proportions of the material obtained are those that were disclosed in this description.

[0129] It should be noted that when specifying any weight range or mass ratio, any particular upper value can be associated with any particular lower value, as well as with any included subranges. In this respect, it should be noted that all ranges disclosed here include endpoints, and endpoints are independently combinable.

[0130] In one embodiment of the present invention, the gelling agent is selected from the group consisting of sodium alginate, xanthan gum, gum arabic and their combinations (including their various degrees of sulfation and molecular weights).

[0131] In one embodiment of the present invention, the plasticizer is selected from the group consisting of polyvinyl alcohol (PVOH), ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), propylene glycol (PG), glycerol, sorbitol, polyols and combinations thereof.

[0132] In a preferred embodiment of the invention, the crosslinking agent is selected from the group consisting of zinc chloride, magnesium chloride, calcium chloride, potassium chloride, aluminum trichloride, iron chloride, aluminum sulfate, copper sulfate, nickel sulfate, epichlorohydrin, glutaraldehyde, citric acid and combinations thereof.

[0133] In one embodiment of the invention, the hydrophobic additive is selected from the group consisting of alkyl ketene dimer (AKD), an alkenyl succinic anhydride (ASA), oils, waxes, resins, rosin, and combinations thereof.

[0134] In one embodiment of the present invention, the microfibrillated cellulosic material is selected from the group consisting of microfibrillated cellulosic material from Kraft pulp, high-yield microfibrillated cellulosic material from Kraft pulp, unbleached microfibrillated cellulosic material from Kraft pulp, bleached microfibrillated cellulosic material from Kraft pulp, semi-bleached microfibrillated cellulosic material from Kraft pulp, sulfite pulp microfibrillated cellulosic material, unbleached sulfite pulp microfibrillated cellulosic material, bleached sulfite pulp microfibrillated cellulosic material, semi-bleached sulfite pulp microfibrillated cellulosic material, and combinations thereof.Additionally, this microfibrillated cellulosic material can be produced by any mechanical and / or biological and chemical wood treatments, such as enzymatic treatments, individually or in any preferred sequence.

[0135] In one embodiment of the present invention, the microfibrillated cellulosic material is eucalyptus Kraft cellulose pulp.

[0136] The cellulose foam of the present invention has uses in different areas and applications such as, but not limited to, thermal insulation, protection in the transport of fragile, sensitive products, or those requiring temperature control, water retention, pressure sensors, cosmetic products and biomedical devices such as biosensors and intelligent systems for controlled release of active substances for atopic applications.

[0137] It has been found that the combination of microfibrillated cellulosic material, at least one gelling agent and at least one plasticizer in the proportions defined in the present invention is crucial for the formation of a stable three-dimensional hydrogel network and for obtaining a lightweight, porous and mechanically resistant cellulosic foam.

[0138] Compositions outside the ranges defined here, or formulations that do not include at least one of these components, tend to result in denser, less porous, or structurally weaker materials, with inferior mechanical, thermal, or insulation performance.

[0139] Examples: Although the invention is described with reference to several exemplary embodiments, those skilled in the art will understand that various alterations can be made and equivalent elements can be substituted without affecting the scope of the present invention. Furthermore, modifications can be made to adapt a specific situation or material to the teachings of the invention without departing from its scope as defined by the appended claims. Therefore, the invention is not limited to the specific embodiments disclosed for the realization of the present invention, but includes all embodiments disclosed in this description and others covered by the scope of its claims.

[0140] Materials

[0141] Microfibrillated cellulosic material was produced from unbleached eucalyptus Kraft pulp.

[0142] In a conical refiner, unbleached eucalyptus Kraft pulp was previously disintegrated and subjected to refining, with the following refining parameters: rotation speed 1230 rpm, edge length 0.574 km / s, power 0.918 kW, SEL (specific energy load applied by the edge of the bars) 1.6 Ws / m and specific energy 350 kWh / ton. The resulting product was further refined in a disc refiner, with the following refining parameters: rotation speed 700 rpm, edge length 39.48 km / s, power 5.922 kW, SEL 0.15 Wm / m and specific energy 1150 kWh / ton. Sodium alginate (CEAMTEX 1691, Ceamsa, Spain) and glycerol (Merck, United States of America) were used directly in the formulation. A 13% AKD suspension (for every 100g of suspension, 13g are AKD and 87g are water) was also added directly to the formulation.In the examples presented here, the amount of AKD added corresponded to 5% of the total dry fiber mass (MCM+MC) used in the final formulation (example: for 3g of dry fiber, 0.15g of AKD was added).

[0143] Finally, in the examples presented here, zinc chloride (ZnCl) in a 2% w / v aqueous solution was used as a crosslinking agent at a mass ratio of 0.02% w / w relative to the total formulation mass.

[0144] In order to standardize the analysis of the results with respect to their characterization in terms of properties, for all freeze-dried samples, 12g of formulation were prepared in 2x2x2cm cubic molds.

[0145] Example 1 - Sodium alginate, MCM and glycerol, without the use of a crosslinking agent and without the use of a hydrophobic additive. Cellulosic foams were produced with varying compositions of sodium alginate (NALG), microfibrillated cellulose material (MCM) and glycerol (GOL) between 5 to 45% w / w, 10 to 60% w / w, and 20 to 65% w / w, respectively. The cellulosic foams were uniform, very lightweight and very porous, with density values ​​of ~0.03 g / cm³. 3and porosity above ~60%. Regarding the hydrophobicity / hydrophilicity of the cellulosic foams produced from a lower mass ratio, they proved to be highly absorbent. When the mass ratio increased, they showed a greater hydrophobic character. Their thermal stability was verified with thermogravimetric degradation values ​​(30% mass loss) above 180 °C. Regarding their compression resistance (maximum compression force for 25% deformation), the foams showed flexibility that depends on the mass ratio of the formulation used, presenting values ​​between 1 and 8 N.

[0146] During biodegradability tests according to ISO 23517:2021, cellulosic foams prepared with a lower formulation mass ratio showed complete disintegration and biodegradation of over 90% of the initial mass, confirming their compostability profile. In the case of cellulosic foams prepared with a higher formulation mass ratio, disintegration was not complete, and biodegradation values ​​were above 70%.

[0147] Three illustrative examples of this type of cellulosic foam are presented below.

[0148] An aqueous formulation consisting of sodium alginate (NALG), microfibrillated cellulosic material (MCM), and glycerol (GOL) was considered, according to the following mass ratios (Table 1):

[0149] Table 1. Mass ratio of the aqueous formulations of Example 1.

[0150] Mass ratio, % m / m NALG: MCM: GOL: H2O

[0151] A 0, 25: 0, 5: 0, 75: 98, 5

[0152] B 0.5:1:1.25:97.250

[0153] C 1, 5: 2, 5: 3: 93

[0154]

[0155] The cellulose foam was prepared according to the following steps: a) all components were mixed with stirring at 1000 rpm at room temperature for 4 hours until total and uniform dispersion of all compounds in the formulation and formation of a hydrogel;

[0156] b) The hydrogel formed in step a) was distributed into molds for drying by freeze-drying until all of its initial water volume was removed and the cellulose foam was formed.

[0157] The resulting cellulosic foams presented a composition m / m % of (Table 2):

[0158] Table 2. Compositions of the cellulosic foams of Example 1.

[0159] Composition* of cellulosic foams, % w / w NALG / MCM / GOL

[0160] A' 15, 4: 30, 9: 46, 3

[0161] B' 14, 2: 45, 4: 35, 5

[0162] C 18, 5: 30, 9: 37, 0

[0163]

[0164] * The total percentage of cellulosic foams is made up of a percentage of water that is acquired in equilibrium with the ambient relative humidity (RH) (in the case of these examples, 50% RH at 23°C for 24h).

[0165] Example 2 - Sodium alginate, MCM and glycerol, with the use of a crosslinking agent and without the use of a hydrophobic additive. Cellulosic foams were produced with varying compositions of sodium alginate (NALG), microfibrillated cellulosic material (MCM), glycerol (GOL) and crosslinking agent in the ranges between 5 to 45% w / w, 10 to 60% w / w, 20 to 65% w / w and 0.1 to 3% w / w, respectively. The products obtained were uniform, lightweight and porous, with density values ​​of ~0.05 g / cm³. 3and porosity above ~55%, due to the presence of the crosslinking agent. Regarding the hydrophobicity / hydrophilicity of the cellulosic foams produced from a lower mass ratio, they proved to be absorbent. When the mass ratio increased, they showed a greater hydrophobic character and resistance to humidity, even in relation to the foams of example 1, due to the presence of the crosslinking agent. Their thermal stability was also verified with thermogravimetric degradation values ​​(30% mass loss) above 190 °C. Regarding their compression resistance (maximum compression force for 25% deformation), the foams showed flexibility depending on the mass ratio of the formulation used, presenting slightly higher values ​​compared to the foams of example 1, between 1 and 10 N, due to the presence of the crosslinking agent.

[0166] During biodegradability tests according to ISO 23517:2021, cellulosic foams prepared with a lower formulation mass ratio showed complete disintegration and biodegradation of over 90% of the initial mass, confirming their compostability profile. In the case of cellulosic foams prepared with a higher formulation mass ratio, disintegration was not complete, and biodegradation values ​​were above 50%.

[0167] Three illustrative examples of this type of cellulosic foam are presented below.

[0168] An aqueous formulation consisting of sodium alginate (NALG), microfibrillated cellulosic material (MCM), glycerol (GOL), and zinc chloride (ZnCl) was considered according to the following mass ratios (Table 3): Table 3. Mass ratio of the aqueous formulations of Example 2.

[0169] Mass ratio, % m / m

[0170] NALG: MCM: GOL: ZnCl: H20

[0171] D 0.25:0.5:0.75:0.02:98.480

[0172] E 0, 5: 1: 1, 25: 0, 02: 97, 230

[0173] F 1.5:2.5:3:0.02:92.980

[0174]

[0175] The cellulose foam was prepared according to the following steps:

[0176] a) All components were mixed with stirring, except for the crosslinking agent, at 1000 rpm at room temperature for 4 hours until complete and uniform dispersion of all compounds in the formulation and formation of a hydrogel;

[0177] b) ZnCl (2% w / v solution) was added to the hydrogel at 15,000 rpm (using an Ultra-Turrax® homogenizer) for 10 minutes at room temperature to ensure complete and uniform dispersion of all formulation components and formation of a hydrogel; c) The hydrogel formed in step b) was distributed into molds for lyophilization drying until all of its initial water volume was removed and the cellulose foam was formed.

[0178] The resulting cellulosic foams presented a composition w / w % of (Table 4):

[0179] Table 4. Compositions of the cellulosic foams of Example 2.

[0180] Composition* of cellulosic foams! m / m

[0181]

[0182] NALG / MCM / GOL / ZnCl

[0183] D' 14, 2: 28, 3: 42, 5: 1, 3

[0184] E ' 13, 3: 42, 5: 33, 2: 0, 6

[0185] F' 18, 5:30, 8:37, 0:0, 3

[0186]

[0187] * The total percentage of the cellulose foam is made up of a percentage of water that is acquired in equilibrium with the ambient relative humidity (RH) (in the case of these examples, 50% RH at 23°C for 24h).

[0188] Example 3 - Sodium alginate, MCM and glycerol, using a crosslinking agent and a hydrophobic additive. Cellulosic materials were produced with varying amounts of sodium alginate (NALG), microfibrillated cellulosic material (MCM) and glycerol (GOL) in the ranges of Example 1 and, additionally, with the crosslinking agent zinc chloride and the hydrophobic additive AKD in varying amounts between 0.1 to 3% w / w and 0.1 to 5% w / w, respectively. The products obtained were uniform, denser and more compact compared to the cellulosic foams of Example 2, with density values ​​of ~0.1 g / cm³. 3and porosity above ~50%, due to the presence of the crosslinking agent and the hydrophobic additive. Regarding the hydrophobicity / hydrophilicity of the cellulosic foams produced from a lower mass ratio, they proved to be absorbent. When the mass ratio increased, they showed a greater hydrophobic character, even in relation to the foams of examples 1 and 2, due to the presence of the crosslinking agent and the hydrophobic additive. Their thermal stability was also verified with thermogravimetric degradation values ​​(30% mass loss) above 200 °C. Regarding their compression resistance (maximum compression force for 25% deformation), the foams showed flexibility depending on the mass ratio of the formulation used, presenting slightly higher values ​​compared to the foams of examples 1 and 2, between 1 and 12 N, due to the presence of the crosslinking agent and the hydrophobic additive.

[0189] During biodegradability tests according to ISO 23517:2021, cellulosic foams prepared with a lower formulation mass ratio showed complete disintegration and biodegradation of over 90% of the initial mass, confirming their compostability profile. In the case of cellulosic foams prepared with a higher formulation mass ratio, disintegration was not complete, and biodegradation values ​​were above 40%.

[0190] Three illustrative examples of this type of cellulosic foam are presented below.

[0191] An aqueous formulation consisting of sodium alginate (NALG), microfibrillated cellulosic material (MCM), glycerol (GOL), ZnCl and AKD was considered according to the following mass ratios (Table 5):

[0192] Table 5. Mass ratio of the aqueous formulations of Example 3.

[0193] Mass ratio, % m / m

[0194] NALG: MCM: GOL: ZnCl: AKD: H20

[0195] G 0.25:0.5:0.75:0.02:0.025:98.455

[0196] H 0.5:1:1, 25:0, 02:0, 05:97, 180

[0197] I 1, 5: 2, 5: 3: 0, 02: 0, 125: 92, 855

[0198]

[0199] The cellulose foam was prepared according to the following steps:

[0200] a) All components were mixed with stirring, except for the crosslinking agent, at 1000 rpm at room temperature for 4 hours until complete and uniform dispersion of all compounds in the formulation and formation of a hydrogel;

[0201] b) ZnCl was added to the hydrogel at 15,000 rpm (using an Ultra-Turrax) for 10 minutes at room temperature in order to ensure complete and uniform dispersion of all components of the formulation and formation of a hydrogel;

[0202] c) The hydrogel formed in step c) was distributed into molds for drying by freeze-drying until all of its initial water volume was removed and the cellulose foam was formed.

[0203] The resulting cellulosic foams had a composition m / m % of (Table 6):

[0204] Table 6. Compositions of the cellulosic foams of Example 3

[0205] Composition* of cellulosic foams, % w / w

[0206] NALG: MCM: GOL: ZnCl: AKD

[0207] G' 13, 4: 26, 9: 40, 3: 1, 3: 1, 3

[0208] H' 13, 1: 41, 8: 32, 6: 0, 6: 1, 3

[0209] I' 18, 0: 29, 9: 35, 9: 0, 3: 1, 5

[0210]

[0211] * The total percentage of cellulose foam is made up of a percentage of water that is acquired in equilibrium with the ambient relative humidity (RH) (in the case of these examples, 50% RH at 23°C for 24h).

[0212] Example 4 - Sodium alginate, MCM and glycerol, with the use of a hydrophobic additive and without the use of a crosslinking agent. Cellulosic foams were produced with varying compositions of sodium alginate (NALG), microfibrillated cellulosic material (MCM), glycerol (GOL) and hydrophobic additive in the ranges between 5 to 45% w / w, 10 to 60% w / w, 20 to 65% w / w and 0.1 to 5%.

[0213]

[0214] m / m, respectively. The products obtained were uniform, lightweight, and porous. Regarding the hydrophobicity / hydrophilicity of the cellulosic foams produced from a lower mass ratio, they proved to be absorbent. When the mass ratio increased, they showed greater resistance to moisture, even compared to the foams in Example 1, due to the presence of the hydrophobic additive. Their thermal stability was also verified, with thermogravimetric degradation values ​​(30% mass loss) above 190 °C. Regarding their compression resistance (maximum compression force for 25% deformation), the foams showed flexibility depending on the mass ratio of the formulation used, presenting values ​​in line with the foams in Example 1.

[0215] During biodegradability tests according to ISO 23517:2021, cellulosic foams prepared with a lower formulation mass ratio showed complete disintegration and biodegradation of over 90% of the initial mass, confirming their compostability profile. In the case of cellulosic foams prepared with a higher formulation mass ratio, disintegration was not complete, and biodegradation values ​​were above 50%.

[0216] Three illustrative examples of this type of cellulosic foam are presented below.

[0217] An aqueous formulation consisting of sodium alginate (NALG), microfibrillated cellulosic material (MCM), glycerol (GOL), and AKD was considered according to the following mass ratios (Table 7): Table 7. Mass ratio of the aqueous formulations of Example 4.

[0218] Mass ratio, % m / m

[0219] NALG: MCM: GOL: AKD: H20

[0220] J 0.25:0.5:0.75:0.025:98.475

[0221] K 0.5:1:1.25:0.05:97.2

[0222] L 1, 5: 2, 5: 3: 0, 125: 92, 875

[0223]

[0224] The cellulose foam was prepared according to the following steps:

[0225] a) All components were mixed with stirring at 1000 rpm at room temperature for 4 hours until complete and uniform dispersion of all compounds in the formulation and formation of a hydrogel;

[0226] b) The hydrogel formed in step a) was distributed into molds for drying by lyophilization until all of its initial water volume was removed and the cellulose foam was formed.

[0227] The resulting cellulosic foams had a composition m / m % of (Table 8):

[0228] Table 8. Compositions of the cellulosic foams of Example 4.

[0229] Composition* of cellulosic foams, % w / w NALG / MCM / GOL / AKD

[0230] John 14:9-29, 8:44, 7:1-5

[0231] K' 16, 2: 32, 5: 40, 6: 1, 6

[0232] L' 19, 1: 31, 9: 38, 3: 1, 6

[0233]

[0234] * The total percentage of the cellulose foam is made up of a percentage of water that is acquired in equilibrium with the ambient relative humidity (RH) (in the case of these examples, 50% RH at 23°C for 24 hours). Characterization of the examples

[0235] Density and Porosity

[0236] Table 9 presents the density and porosity results for the different examples.

[0237] Table 9. Density and porosity values ​​for the different examples.

[0238] Examples Product Density Porosity (%)

[0239] g / cm 3

[0240] 1 A' 0.03 ± 0.002 64.8 ± 1.8

[0241] B' 0.03 ± 0.002 62.9 ± 1.5 C' 0.02 ± 0.001 59.6 ± 0.8 2 D' 0.04 ± 0.004 59.8 ± 1.7

[0242] E' 0.05 ± 0.005 58.2 ± 2.4 F' 0.05 ± 0.003 58.6 ± 1.3 3 G' 0.09 ± 0.004 55.0 ± 1.1

[0243] H' 0.09 ± 0.006 54.0 ± 1.5 I' 0.09 ± 0.004 53.2 ± 0.8

[0244]

[0245] The cellulosic foams resulting from Example 1 (A', B' and C') proved to be uniform, very lightweight and very porous according to density values ​​of ~ 0.03 g / cm³. 3 and porosity above ~60%.

[0246] The resulting cellulosic foams from Example 2 (D', E' and F') proved to be uniform, lightweight and porous compared to the cellulosic foams from Example 1, according to density values ​​of ~0.05 g / cm³. 3 and porosity above ~55%, due to the presence of the crosslinking agent.

[0247] The cellulosic foams resulting from Example 3 (G', H' and I') were uniform, denser and more compact compared to the cellulosic foams from Example 2, according to density values ​​of ~0.09 g / cm³. 3 and porosity above ~50%, due to the presence of the crosslinking agent and the hydrophobic additive.

[0248] The cellulosic foams resulting from Example 4 (J', K' and L') did not reveal significant differences in relation to the cellulosic foams of examples 1 and 2.

[0249] The values ​​obtained are close to the density values ​​of other insulating foams available on the market, such as rigid PU boards for thermal insulation (between 0.03-0.1 g / cm³). 3 ) or expanded polystyrene (0.02 g / cm³) 3 ).

[0250] Contact angles in water

[0251] Table 10 presents the results for contact angles for the different examples.

[0252] Table 10. Contact angle values ​​for the different examples.

[0253] Examples Product Angle of

[0254] Angle of contact with contact with the

[0255] water (°)

[0256] water (°)

[0257] ( 150s )

[0258] ( 0s )

[0259] 1 A' 0 - B' 0 - C' 108.1 ± 12. 0 0

[0260] H' 126.2 ± 12.0 77.5 ± 7.5 I' 116.0 ± 5.0 57.0 ± 10.2

[0261]

[0262] In the cellulosic foams A' and B' from example 1 and in the cellulosic foam D' from example 2, it was not possible to measure the water contact angle, as these foams proved to be highly absorbent. However, in the cellulosic foam C', with a higher formulation mass ratio, it was possible to measure the water contact angle, above 100°, demonstrating a lower water absorption / penetration rate compared to cellulosic foams A', B', and D'. Cellulosic foams E' and F' showed water contact angles above 115°, also demonstrating a lower water absorption / penetration rate compared to cellulosic foam C' due to the presence of the crosslinking agent. In the case of G' cellulosic foam, despite a lower formulation mass ratio, it was already possible to measure the contact angle with water, due to the effect of adding a crosslinking agent and a hydrophobic additive to the formulation.As the mass ratio of the formulation increased, contact angles with water above 115° were observed in the H' and I' cellulosic foams.

[0263] The cellulosic foams resulting from Example 4 (J', K' and L') showed behavior in line with the cellulosic foams from Example 2.

[0264] Thus, a higher mass ratio of the formulation and the addition of the crosslinking agent and hydrophobic additive increased the hydrophobic character of the cellulosic foams and decreased their water absorption / penetration capacity.

[0265] Fossil-based foams currently on the market, such as PU or expanded polystyrene boards, have exhibited higher water contact angles because they are impermeable. However, most cellulosic foams of the present invention have demonstrated satisfactory moisture resistance and hydrophobicity for a wide range of applications. Importantly, their partial hydrophilicity is essential for their biodegradability / compostability profile (unlike fossil-based insulating foams).

[0266] TGA Table 11 presents the results for the temperatures corresponding to 10% (mostly related to the water present in the samples) and 30% mass loss of the different examples.

[0267] Table 11. Temperature values ​​corresponding to 10% and 30% mass loss for the different examples.

[0268] Examples Product T (°C)

[0269] T ( ° C )

[0270] 10% loss of

[0271] 30% loss of more know more know

[0272] 1 A' 146. 09 ± 6. 1 204. 6 ± 1. 3

[0273] B' 82. 0 ± 11. 2 196. 9 ± 3. 5 C' 89. 1 ± 5. 8 202. 2 ± 3. 4 2 D' 125. 6 ± 5. 3 202. 8 ± 5. 2

[0274] E' 78. 6 ± 6. 0 191. 1 ± 7. 1 F' 98. 1 ± 10. 8 200. 9 ± 2. 1 3 G' 130. 2 ± 8. 1 201. 3 ± 0. 1

[0275] H' 108. 7 ± 8. 0 201. 7 ± 3. 4 I' 83. 8 ± 3. 8 199. 9 ± 6. 4

[0276]

[0277] Polyurethane foams exhibited thermogravimetric degradation values ​​above 300 °C, demonstrating excellent thermal stability. In turn, the cellulosic foams resulting from examples 1 to 4, even when composed solely of materials of natural origin, showed thermogravimetric degradation values ​​(30% mass loss) between 190 and 205 °C, demonstrating the high thermal stability of the materials of the present invention. Mechanical Compression Tests

[0278] Table 12 presents the results for the compressive forces at 25% deformation for the different examples.

[0279] Table 12. Compressive force values ​​for 25% deformation for the different examples.

[0280] Examples Product Compression force for 25

[0281] % deformation (N)

[0282] 1 A' 0. 8 ± 0. 1

[0283] B' 3.4 ± 0.5

[0284] C' 6. 6 ± 0.2

[0285] 2 D' 1. 1 ± 0. 1

[0286] E' 6.4 ± 0.5

[0287] F' 7.2 ± 0.7

[0288] 3 G' 0.9 ± 0.1

[0289] H' 6.2 ± 0.5

[0290] I' 8.0 ± 0.1

[0291]

[0292] Through compression tests, it was observed that all cellulosic foams from examples 1 to 4 were flexible cellulosic foams with shape memory at different levels, according to the compression forces recorded. In all cellulosic foams from examples 1 to 4, the compression force for 25% deformation increases with the increase in the mass ratio of the formulations and with the subsequent addition of the crosslinking agent and the hydrophobic additive.

[0293] Images WITHOUT

[0294] Table 13 presents the SEM images of the different examples.

[0295] Table 13. SEM images for the different examples.

[0296] Product A' D' G'

[0297]

[0298] Image

[0299] WITHOUT WWW

[0300] iiil « ■I Product B' HE' inh H'

[0301] Image

[0302] WITHOUT ■MBÍI A

[0303] í?, W

[0304] Product CF' i'

[0305] Image ■■

[0306] WITHOUT

[0307] ■■■■■■■ liíll l ■MMI

[0308]

[0309] ■MÍMNBk ■illBiioM MW

[0310] In all cellulosic foams from examples 1 to 4, SEM images demonstrated highly uniform and porous cellulosic foams, except that porosity decreases with increasing mass ratio of the formulations and with the subsequent addition of the crosslinking agent and hydrophobic additive. Thus, porosity can be adjusted according to the desired application within the same values ​​as other insulating and non-insulating foams available on the market.

[0311] Elementary analysis

[0312] Table 14 presents the results for the elemental analysis of the different examples.

[0313] Table 14. Elemental analysis values ​​for the different examples.

[0314] Examples Product N / C / H (%, dry mass) 1 A' 0.37:40.6:6.1

[0315]

[0316] B' 0,32:40,2:6,3

[0317] C' 0.34:40.3:6.3

[0318] 2 D' 0,34:38,3:5,9

[0319] E' 0,32:40,2:6,1

[0320] F' 0,36:39,8:6,5

[0321] 3 G' 0.45:40.1:6.3

[0322] H' 0,33:40,6:6,4

[0323] I' 0,38:41,4:6,6

[0324]

[0325] All the cellulosic foams from the different examples (1 to 4) showed a percentage of ~40% carbon and ~0.35% nitrogen, which corresponds to a C / N ratio of ~100:1, comparable with other compostable materials such as, for example, wood (100-500:1) or paper (150-200:1).

[0326] Biodegradability / Compostability Tests

[0327] Compostability tests of cellulosic foams from the different examples (1 to 4), according to ISO 23517: 2021, revealed, in 12 weeks, complete disintegration and biodegradation of 95-100% of the initial mass of the cellulosic foams from the lowest formulation mass ratios. For the remaining examples, where higher formulation mass ratios were used, total disintegration was not observed, and biodegradation between 50 and 75% was observed, which means that they would require more than 12 weeks for complete compostability (Figure 3).

[0328] Synthetic polyurethane or polystyrene foams are not compostable or biodegradable, according to ISO 23517:2021. Table 15 presents the compostability results of the different examples according to ISO 23517:2021.

[0329] Table 15. Compostability values ​​for the different examples according to ISO 23517: 2021.

[0330] Examples: Product 6 weeks (%, dry mass) 12 weeks (%, dry mass)

[0331] 1 A' 95 95

[0332] B' 50 95

[0333] C' 10 75

[0334] 2 D' 95 95

[0335] E' 50 95

[0336] F' 10 60

[0337] 3 G' 95 95

[0338] H' 50 95

[0339] I' 10 50

[0340]

[0341] Thermal insulation properties

[0342] For measuring thermal insulation properties, the cellulosic foam F' from example 2 was selected as representative of the cellulosic foams from the remaining examples with respect to this property, taking into account its mass ratio and the presence of a crosslinking agent.

[0343] Table 16 presents the results for thermal conductivity and diffusivity, and specific heat of example F'.

[0344] Table 16. Thermal conductivity and diffusivity values, and specific heat of example F'.

[0345] Heat Conductivity Diffusivity

[0346] specific thermal (mm 2 / s)

[0347] (W / m. K) (MJm -3 K -1 )

[0348]

[0349] F' 0.059 ± 0.001 0.672 ± 0.010 0.088 ± 0.001

[0350]

[0351] The cellulosic foam F' from example 2 showed a thermal conductivity close to that of expanded polystyrene (0.035-0.037 W / m.K), demonstrating that these foams can be used as thermal insulators and more sustainable alternatives to fossil-based solutions.

Claims

1. CLAIMS 1. Cellulosic foam characterized by comprising 10-60% w / w of a microfibrillated cellulosic material, 5-45% w / w of at least one gelling agent and 20-65% w / w of at least one plasticizer.

2. Cellulosic foam according to claim 1, characterized by further comprising 0.1-3% w / w of at least one crosslinking agent.

3. Cellulosic foam according to claim 1 or 2, characterized by further comprising 0.1-5% w / w of at least one hydrophobic additive.

4. Cellulosic foam according to claim 3, characterized by consisting of 13.1% w / w of at least one gelling agent, 41.8% w / w of microfibrillated cellulosic material, 32.6% w / w of at least one plasticizer, 0.6% w / w of at least one crosslinking agent and 1.3% w / w of at least one hydrophobic additive, the remaining percentage being water.

5. Cellulosic foam according to any of the preceding claims, characterized in that the microfibrillated cellulosic material is selected from the group consisting of microfibrillated Kraft pulp cellulosic material, high-yield microfibrillated Kraft pulp cellulosic material, unbleached microfibrillated Kraft pulp cellulosic material, bleached microfibrillated Kraft pulp cellulosic material, semi-bleached microfibrillated Kraft pulp cellulosic material, sulfite pulp microfibrillated cellulosic material, unbleached microfibrillated sulfite pulp cellulosic material, bleached microfibrillated sulfite pulp cellulosic material, and semi-bleached microfibrillated sulfite pulp cellulosic material. their combinations.

6. Cellulosic foam according to any of the preceding claims, characterized in that the Kraft cellulose pulps are eucalyptus cellulose pulps.

7. Cellulosic foam according to any of the preceding claims, characterized in that the gelling agent is selected from the group consisting of sodium alginate, xanthan gum, gum arabic and combinations thereof.

8. Cellulosic foam according to any of the preceding claims, characterized in that the plasticizer is selected from the group consisting of polyvinyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, glycerol, sorbitol, polyols and combinations thereof.

9. Cellulosic foam according to any one of claims 2 to 8, characterized in that the crosslinking agent is selected from the group consisting of zinc chloride, magnesium chloride, calcium chloride, potassium chloride, aluminum trichloride, iron chloride, aluminum sulfate, copper sulfate, nickel sulfate, epichlorohydrin, glutaraldehyde, citric acid and combinations thereof.

10. Cellulosic foam according to any one of claims 3 to 9, characterized in that the hydrophobic additive is selected from the group consisting of alkyl ketene dimer, alkenyl succinic anhydride, oils, waxes, resins, rosins and combinations thereof.

11. Cellulosic foam according to any one of claims 3 to 10, characterized in that the gelling agent is sodium alginate, the plasticizer is glycerol, the crosslinking agent is zinc chloride, and the hydrophobic additive is alkyl ketene dimer.

12. A process for producing the cellulose foam claimed in any one of claims 1 to 11, characterized by comprising the following steps: a) constitution of an aqueous formulation comprising 0.25-3% w / w of a microfibrillated cellulosic material, 0.25-2% w / w of at least one gelling agent and 1-3% w / w of at least one plasticizer; b) stirring the resulting formulation from step a) at room temperature until a hydrogel is formed; c) dispensing the hydrogel resulting from step b) into molds; d) drying the hydrogel resulting from step c) by means of freeze-drying until the total removal of the initial water volume and formation of the cellulose foam.

13. Process according to claim 12, characterized by further comprising, after step b) and before step c), a step of adding 0.02-0.08% w / w of at least one crosslinking agent to the hydrogel resulting from step b) by homogenization and at room temperature until a hydrogel is formed.

14. Process according to claim 12, characterized in that the formulation of step a) further comprises 0.01-0.15% w / w of at least one hydrophobic additive.

15. Process according to claim 12, characterized in that the formulation of step a) further comprises 0.01-0.15% w / w of at least one hydrophobic additive and after step b) and before step c) there is also a step of adding 0.02-0.08% w / w of at least one crosslinking agent to the hydrogel resulting from step b) by homogenization and at room temperature until a hydrogel is formed.

Images