EP4036307A1 - Appareil et procédé de préparation d'un produit de réseau de fibres biodégradables tridimensionnel de fibres organiques naturelles, ledit produit et son utilisation - Google Patents

Appareil et procédé de préparation d'un produit de réseau de fibres biodégradables tridimensionnel de fibres organiques naturelles, ledit produit et son utilisation Download PDF

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Publication number
EP4036307A1
EP4036307A1 EP22154829.0A EP22154829A EP4036307A1 EP 4036307 A1 EP4036307 A1 EP 4036307A1 EP 22154829 A EP22154829 A EP 22154829A EP 4036307 A1 EP4036307 A1 EP 4036307A1
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EP
European Patent Office
Prior art keywords
mould
pores
electromagnetic energy
natural organic
aqueous solution
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EP22154829.0A
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German (de)
English (en)
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EP4036307C0 (fr
EP4036307B1 (fr
Inventor
Rafal Brzyski
Michal Ziólkowski
Mateusz Szafranski
Andrii Holovin
Monika Jezak
Jakub Sosinski
Pawel Przybyszewski
Tomasz CIAMULSKI
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Fibritech Sp Z OO
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Organic Disposables Sp zoo
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Priority to EP24187389.2A priority Critical patent/EP4435179A2/fr
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Application granted granted Critical
Publication of EP4036307C0 publication Critical patent/EP4036307C0/fr
Publication of EP4036307B1 publication Critical patent/EP4036307B1/fr
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    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21J—FIBREBOARD; MANUFACTURE OF ARTICLES FROM CELLULOSIC FIBROUS SUSPENSIONS OR FROM PAPIER-MACHE
    • D21J3/00—Manufacture of articles by pressing wet fibre pulp, or papier-mâché, between moulds

Definitions

  • the present invention relates to an apparatus and a method for the preparation of a biodegradable three-dimensional fibre network product from defibrated natural organic fibres using electromagnetic (EM) energy.
  • the invention relates also to said product and use thereof as a plant growth substrate, filtration medium, filling and/or acoustic and mechanical damping structure.
  • Natural organic fibres of plants or animal origin have been widely used for many years in many industries, such as paper and wood industry, due to advantageous mechanical properties including good tensile strength, low weight and specific stiffness, but also due to its renewable character and ability to be broken down by bacteria making them environment friendly.
  • cellulose fibres used as raw material are wetted, converted into a pulp, pressed, and dried giving sheets of paper having a substantially flat shape, wherein the fibres are oriented substantially in the sheet-plane direction, which results in a product having a good tensile strength in said sheet-plane direction. Compression into thin sheets of paper allows for effective removal of water from the material, whereas production of thicker sheets is limited and requires more energy to dry the final product.
  • Timofeev, et al. "Drying of foam-formed mats from virgin pine fibers", (2016), Drying Technology, 34:10, 1210-1218 , describes drying of foam-formed mats from virgin pine fibres using the steps of fibre foam preparation, draining of the liquid, and drying with the use of different drying methods, namely convective drying in the oven, impingement drying assisted by vacuum, combined impingement-infrared drying, and through-air drying. Shrinkage of the final product was observed in all tested drying methods with the lowest shrinkage observed for combined techniques.
  • Wood fibres are widely used for the manufacturing of fibreboards (such as MDF or HDF), however, in order to obtain desired properties of the fibreboard, fibres are mixed with a synthetic binder and formed into panels by hot-pressing. Synthetic binders used in the production of fibreboards are not environmentally friendly and such materials have limited uses.
  • US 2001024716A1 discloses a method of producing an open low-density absorbent fibrous structure comprising combining hydrophilic fibres with a structuring composition to form a mixture, said structuring composition comprising a binder material and a removable phase; producing a foam within said mixture and binding said fibres together with substantially water-insoluble bonds into a continuous, porous network, wherein said binder material stabilizes the porous network.
  • Various noncompressive drying techniques including air drying and microwave drying are disclosed to evacuate removable phase. However, said drying techniques require that essentially all of the removable phase is transformed from a liquid phase into a vapour phase, which is either time consuming or expensive in terms of energy demand.
  • WO 2018237279 discloses perforated structures such as molds for manufacturing fibre-based materials by passing gas or liquid through the perforated structure, where different sets of perforations are grouped in zones to form a shape that is conformal to the product, Examples of the products that may be obtained with said molds are limited to structures of relatively small thickness such as carton, trays, conformal packaging, feminine hygiene products or diapers.
  • An aspect of the present invention is to provide an apparatus for the preparation of a three-dimensional biodegradable fibre network product using electromagnetic energy.
  • Another aspect of the present invention is to provide a method for the preparation of a three-dimensional biodegradable fibre network product using electromagnetic energy.
  • the apparatus and method allow to control density and anisotropy inside the product and forming it into any shape.
  • the apparatus and method allow very short forming times of the product.
  • the apparatus allows automation and large-scale production of a three-dimensional biodegradable fibre network product.
  • Another aspect of the present invention is to provide a three-dimensional biodegradable fibre network product prepared by the method according the invention.
  • Yet another aspect of the present invention is to provide a use of said product as a plant growth substrate, filtration medium, filling and/or acoustic and mechanical damping structure.
  • references in the specification to "an embodiment”, “one embodiment”, “another embodiment”, etc., indicate that the embodiment described may include one or more features. Additionally, when features are described in connection with one embodiment, it should be understood that such features may also be used in connection with other embodiments whether or not explicitly described unless clearly stated to the contrary.
  • an apparatus for the preparation of a three-dimensional biodegradable fibre network product comprising: a mould comprising a plurality of pores and configured to be filled with foamed natural organic fibres in aqueous solution, an electromagnetic energy provider for providing electromagnetic energy to the foamed natural organic fibres inside the mould, and a controller component configured to control the electromagnetic energy provided by the electromagnetic energy provider to control a pressure build-up internally within the mould, wherein the three-dimensional biodegradable fibre network product is prepared based on evacuating liquid and steam from the mould through the pores by the provided electromagnetic energy.
  • the pores of the mould are small enough that evaporated liquid within the mould results in a pressure build-up within the mould by the application of the electromagnetic energy.
  • the electromagnetic energy provider is thus preferentially capable of dielectrically heating the aqueous solution within the mould until steam is formed which causes the pressure build-up.
  • the liquid and steam evacuate through the pores of the mould, thereby shaping the natural organic fibres into their three-dimensional network and drying the solution.
  • a surface share of the pores with regard to the surface encapsulating the volume within the mould is small such that internal pressure can build up, wherein the ideal share is preferentially dependent on a size of the mould. This is the case because the surface to volume ratio differs among different mould volumes.
  • the surface share of the pores is in an embodiment between 0.2% and 20%, preferably between 1% and 15% and most preferably between 4% and 12%.
  • the surface share of the pores is in an embodiment between 0.5% and 40%, preferably between 2% and 20% and most preferably between 6% and 14%, and for the volume between 10 litres and 100 litres the surface share of the pores is in an embodiment between 1% and 60%, preferably between 4% and 40% and most preferably between 10% and 30%.
  • the shape of the mould is considered in addition to its volume for determining the most appropriate surface share of the pores.
  • controller component is configured to control the electromagnetic energy dependent on a distribution and/or size of the pores of the mould and a desired pressure within the mould.
  • one hole (pore) with an area of 2 mm 2 is capable to suppress the flow of gas (steam) or fluid (water or liquid) less than two holes with the same surface sum, i.e., 1 mm 2 + 1 mm 2 .
  • the pore size is between 0.2 mm and 3 mm, preferably between 0.5 mm and 2 mm and most preferably between 0.8 mm and 1.5 mm.
  • the pores are shaped as round holes and a diameter of the pores is between 0.2 mm and 3 mm, preferably between 0.5 mm and 2 mm and most preferably between 0.8 mm and 1.5 mm. While also other shapes of pores are feasible, it has been shown that the optimum shape of the pores is round.
  • the mould comprises or consists of a dielectric material having a softening point above 100°C
  • the dielectric material does not interfere with the (alternating) electromagnetic field and allows that the electromagnetic energy is not absorbed by the mould but by the content of the mould.
  • the mould comprises or consists of metal, wherein the mould is a functional part of the electromagnetic energy provider.
  • the mould comprises or consists of metal, it may for instance help to generate an electromagnetic field for providing the electromagnetic energy.
  • Fig. 6 illustrates different embodiments a), b), c) and d) of a mould integration with the electromagnetic energy provider, referred to as electromagnetic field delivery device (EM), in cross-sectional view:
  • EM electromagnetic field delivery device
  • the EM device preferably comprises a "closed cavity”
  • the electromagnetic energy may be provided to the cavity using a cavity magnetron as known from microwave ovens.
  • the cavity needs to be opened to access the finished product.
  • Mould is introduced between parallel plates of EM capacitor or into a EM tunnel.
  • the tunnel cavity formed by the parallel plates of the EM tunnel is not limited in one spatial direction, in the example of Fig. 6 in the horizontal direction.
  • the mould material can be inserted into the cavity without need to open the cavity. For instance, this allows a continuous process of moving the mould through the tunnel, or, in a different embodiment, of moving only the fibrous material through mould and tunnel.
  • not only the EM tunnel cavity is open in one spatial direction but also the mould is open in the same spatial direction.
  • Mould is missing upper and lower walls which are replaced by EM device parts; this embodiment may also not have vertical mould walls for continuous bulk material production captured between parallel plates or through the EM tunnel.
  • a perspective view of this example is also illustrated in Fig. 7 and will be described below.
  • the electromagnetic energy provider comprises a cavity and is configured to provide electromagnetic energy, in particular a radio frequency (RF) alternating electromagnetic field, radio wave or microwave electromagnetic radiation, over the cavity.
  • RF radio frequency
  • the cavity is a closed cavity or a tunnel cavity and the electromagnetic radiation causing a dielectric heating is generated as appropriate based on the selected electromagnetic device.
  • the wavelengths of the electromagnetic radiation are not particularly limited.
  • a wavelength which acts to efficiently heat the foamed natural organic fibrous material is chosen.
  • a frequency of the electromagnetic radiation is preferably chosen below 300 GHz and in particular between 10 MHz and 300 GHz.
  • the mould limits at least part of the cavity such that the foamed natural organic fibres in aqueous solution fully fill the cavity of the electromagnetic energy provider.
  • This example is illustrated in view a) of Fig. 6 .
  • the mould is implemented as closed porous mould, wherein the final product is removed from the mould after opening the closed porous mould.
  • the mould according to this embodiment may optionally integrate parts of the walls of the cavity of the electromagnetic energy provider or not. It may be used with closed cavity and tunnel cavity electromagnetic energy providers.
  • the electromagnetic energy provider comprises two substantially parallel plates acting as electrodes. These electrodes can also be integral part of the mould and then comprise pores, cf. view d) of Fig. 6 , or be separate from the mould, cf. view c) of the mould.
  • the mould is made separate from the electromagnetic energy provider and insertable into and removable therefrom.
  • This embodiment is an alternative to integrating the mould and the electromagnetic energy provider and makes it easier to change the shape and layout of the final product.
  • At least one of the faces of the mould is integrally formed by one of the electrodes.
  • the mould is open in one spatial direction such as to enable continuous bulk material production along that direction.
  • FIG. 7 which further develops view d) of Fig. 6 , an exploded perspective view of an apparatus 10 for the preparation of a three-dimensional biodegradable fibre network product is illustrated.
  • the apparatus 10 comprises a mould 20 which is partially integrated with a tunnel cavity of an electromagnetic energy provider 30.
  • a bulk material 40 of foamed natural organic fibres in aqueous solution is inserted into the tunnel cavity along a direction indicated with an arrow A.
  • the electromagnetic energy provider 30 comprises in this example two parallel plate electrodes 32, 34. Together with dielectric faces 22, 24 the material 40 is restricted in four directions and only direction A is open. The size of the open surfaces is small compared to the remaining surfaces such that pressure as desired can build up.
  • the material 40 While passing through the tunnel cavity, the material 40 is provided with electromagnetic energy, the required pressure builds up and steam evacuates through pores 26, 36 on the electrodes 32, 34 and the dielectric faces 22, 24, respectively.
  • controller 50 which, in this example, is illustrated in wired connection with electrodes 32, 34. It should be noted that the distribution of pores 26, 36 is only exemplary and schematic. Also, the form and shape of the electrodes 32, 34 and the remaining faces 22, 24 are not limiting and may be varied as desired.
  • Fig. 8 illustrates the apparatus 10 of Fig. 7 in an assembled view.
  • the present invention provides a method for the preparation of a three-dimensional biodegradable fibre network product, the method comprising the following steps:
  • step c) during proving of the electromagnetic energy to the foamed natural organic fibres in step c) at least a portion of the liquid and steam evacuating through the plurality of pores is removed outside of the area of electromagnetic energy operation.
  • the plurality of pores allows to discharge not only steam, but also water or liquid comprised in a mould outside of the area of the operation of electromagnetic energy. Due to the fact, that this phenomenon take places at early stages of electromagnetic energy provision, a portion of liquid evacuating through the pores is of relatively low temperature and therefore significant portion of water contained in the form is evacuated without the need of its evaporation. Therefore, energy demand is reduced by energy needed to heat all the liquid to a boiling point of water and energy needed for phase transition of this mass into a gaseous state (steam).
  • the method according to an embodiment of the invention allows to use fibrous suspensions having high water content, that can be easily transported during initial phases of formation of a fibrous product, as said water can be efficiently removed during the step of providing of electromagnetic energy to the foamed aqueous solution in a porous mould. Therefore, formation of the fibrous product and removal of water is combined in one step, which significantly reduces energy consumption and simplifies the process.
  • viscosity of a foamed aqueous solution in step a) is kept low during provision of electromagnetic energy in step c).
  • Viscosity of a foamed aqueous solution obtained in step a) is preferably controlled by the use of biodegradable non-fibrous additives, such as those described herein.
  • Low viscosity of the foam facilitates discharging of liquid and steam from pores of the mould during pressure build-up within the mould. At least portion of a liquid and steam evacuating from the pores can be continuously removed outside of an area of electromagnetic energy operation. This portion of a liquid and steam no longer absorbs electromagnetic energy, which significantly improves energy efficiency of the process.
  • the mould has a plurality of pores each having a pore size of 0.01 to 3 mm, preferably of 0.5 to 2 mm, most preferably from 0.8 to 1.5 mm.
  • a share of a total pore area in relation to a internal mould volume is between 0.05 and 0.15 cm -1 , preferably is between 0.05 and 0.1 cm -1 , most preferably is 0.1 cm -1 .
  • a surface share of the pores with regard to the surface encapsulating the volume within the mould is small such that internal pressure can build up, wherein
  • a power density of electromagnetic energy provided to the foamed natural organic fibres in step c) is of 0.5 to 100 kW per kg of the foamed aqueous solution obtained in step a), preferably is of 1 to 25 kW per kg of the foamed aqueous solution obtained in step a), most preferably of 2 to 5 kW per kg of the foamed aqueous solution obtained in step a).
  • foaming natural organic fibres is performed in aqueous solution.
  • the parameters of the foam, and particularly the degree of foaming, have a significant effect on the internal structure of the final fibre network product prepared by the method of the present invention.
  • Foam is a good dispersing medium for fibres in the three-dimensional network and any suitable method of foaming known in the prior art can be used for the method according to the present invention.
  • the size of the foam bubbles determines the distribution of fibres in the three-dimensional space. Therefore, controlling the bubbles allow for obtaining a controlled density gradient in the fibre network product prepared by the method of the present invention.
  • foaming natural organic fibres in aqueous solution is performed by introducing a gas into the pulp.
  • the size and homogeneity of the foam bubbles are influenced by the different phases of the forming process.
  • the stage of preparing the batch of material gives the possibility of shaping the character of the foam by adding to the mass some additives: blowing agents increase the amount of the gas filling the bubbles, surfactants control the foam's susceptibility to foaming.
  • blowing agents increase the amount of the gas filling the bubbles
  • surfactants control the foam's susceptibility to foaming.
  • foam stabilizers allows the foam to maintain the desired properties until the fibres stiffen and take over the role of a supporting skeleton a structure that has so far been held by vanishing bubbles.
  • an aqueous solution used for foaming natural organic fibres comprises at least one biodegradable non-fibrous additive comprising a foam stabilizer, foaming agent, biodegradable blowing agent or combination thereof.
  • Biodegradable foam stabilizers in form of polysaccharides can be used with the method of the present invention.
  • chitosan and/or agar are preferable biodegradable foam stabilizers.
  • Their main goal of foam stabilizers is to extend the life of wet foam, and to support the mechanical stability of the final product.
  • Biodegradable foaming agents meeting environmental standards can be used with the method of the present invention.
  • coco glucoside is a preferred foaming agent.
  • Biodegradable blowing agents introduced into the water solution can also be used as an aid in the formation of foam.
  • the preferred blowing agents are sodium carbonate and sodium bicarbonate, which have minimal impact on the environment.
  • aqueous solution used for foaming natural organic fibres further comprises at least one further additive for controlling biomechanical properties of the obtained fibre network product, wherein said further additive comprise a polysaccharide, polysaccharide derivative, lignin, lignin derivative, cellulose, and a cellulose derivative.
  • non-fibrous additives can be used with the method of the present invention to define end parameters of the material.
  • Some of the additives have a double role, as a material stabilizer and foam enhancers.
  • biomaterials that are at least partially dissolvable in water are used.
  • Preferred non-fibrous additives are agar and chitosan, polysaccharides, that are helping with moisture control and stiffness of the product.
  • Agar gel acts as a foam stabilizer, that extends the life of wet foam, and after electromagnetic forming it acts as a gluing agent, improving the strength of bonds between fibres.
  • Hydrophilic additives e.g., chitosan
  • Hydrophilic additives can be added for agricultural uses of the product obtained by the method according to the present invention, for maintaining moisture for a prolonged time.
  • Biological additives e.g., grapefruit extract
  • Water insoluble, hydrophobic additives e.g., mineral powders
  • mineral powders can be added for creating solutions for construction applications for water repellence.
  • polysaccharides are used as a foam additive to increase the durability of the fibre network product after the forming process.
  • the suitable polysaccharides comprise agarose, chitosan and combination thereof. Agarose mechanically stabilizes the material after forming, by strengthening the bonds between the fibres and securing their surface mechanically. Chitosan, in addition to performing the function of mechanical strengthening, is known for its biocidal properties, protects the material against excessive biological aging.
  • starch is also used as a foam additive, which increases the stiffness of the material after the molding process.
  • Starch is a potential additive, that has impact on mechanical properties of the final material. It makes the outer layer more rigid and brittle.
  • lignin is used as an additive. Lignin may be introduced to increase mechanical strength and water resistance of final product.
  • chemical and mechanical derivatives of cellulose can be used as mechanical stabilizers or modifiers of the fibre surface.
  • examples include cellulose ethers, for example, methyl cellulose and ethyl cellulose, known for their use as industrial rheology modifiers. They can be used as foam stabilizing agents and modifier of interactions between the fibre network product and solvents, either polar or nonpolar.
  • Other cellulose derivatives including hydroxypropylmethylcellulose and cellulose nanofibrils are suitable additives using the method according with the present invention.
  • the method according to an embodiment of the invention allows for controlling of density gradient of the three-dimensional biodegradable fibre network product in any direction in the whole space of the mould.
  • Density gradient of the three-dimensional biodegradable fibre network product prepared by the method according to the present invention is controlled by the arrangement of the plurality of pores in a mould. Density gradient of the three-dimensional biodegradable fibre network product prepared by the method according to the present invention is also controlled by the kind and/or power density of electromagnetic energy provided to the foamed natural organic fibres. Preferably, density gradient of the three-dimensional biodegradable fibre network product prepared by the method according to the present invention is controlled by the arrangement of the plurality of pores in a mould and by the kind and/or power density of electromagnetic energy provided to the foamed natural organic fibres. Mould with fewer pores having foamed fibres subjected to electromagnetic energy with higher power densities of electromagnetic energy results in obtaining higher density gradient in the three-dimensional biodegradable fibre network product.
  • the density of the fibre network product prepared by the method according to the present invention is also controlled by the density of the foam. Lowering foam density, leads to a fibre network product with lower density, and with higher density gradient.
  • Providing electromagnetic energy to the foamed natural organic fibres in a mould with a plurality of pores results in volumetric heating of the foamed natural organic fibres, that leads to the generation of steam and increase in pressure. This results in reorientation of the fibres in certain direction from the inside of the mould.
  • These directions are controlled by the arrangement of the pores adapted to evacuate water and steam. More generally, the pores are adapted to evacuate liquid and steam.
  • the arrangement of the pores comprises pore size, pore shape, pore direction, number of pores in the mould, distance from the pores.
  • the arrangement of the pores sets direction of the steam release path causing compaction of the fibres at the walls of the mould, leading to reinforcement of the final fibre network product. Density gradient of the fibre network product is therefore controlled in a wide range.
  • the method provides a three-dimensional biodegradable fibre network product, which is empty inside. Also, the density of the structure is controlled by the amount of natural organic fibres put into the mould.
  • Providing electromagnetic energy comprises one or more phases, preferably an initial phase and a final phase.
  • electromagnetic energy is delivered intensively to reach water boiling point, which results in forcing the excess of water out of the mould.
  • This initial phase saves energy and time required to evaporate the remaining water, which should be removed and preserves the fibrous web/mesh structure from collapsing/shrinking inside the mould.
  • bonds between natural organic fibres are created forming fibre network product.
  • different electromagnetic energy levels can be required in consecutive phases, for instance, in order to prevent local overheating of the material.
  • pure cellulose fibres as well as ligno-cellulose fibres that have been defibrated mechanically can be used as natural organic fibres for the present invention.
  • Cellulose fibres similar to those used in paper production (after removing the lignin), plant fibres, and other organic fibres, multiversity of which is expected due to their nature can be used.
  • ligno-cellulose fibres that are fractioned mechanically (without removing the lignin) are suitable.
  • Natural organic fibres of one type or as mixture of different type of fibres can be used with the present invention (e.g., by weight: 50% cellulose fibres, 50% hemp fibres - a composition that is more crack resistant than 100% cellulose). Crack resistance is achieved by incorporating long (up to 30mm) natural fibres into the foam. The likely mechanism is that there is an increase in the interaction between a greater number of fibres per volume of the product.
  • the content of natural organic fibres in three-dimensional fibre network product is at least 95% on a dry basis.
  • the length of natural organic fibres is from 0.1 cm to 3.0 cm.
  • natural organic fibres are cellulose fibres.
  • natural organic fibres are ligno-cellulose fibres.
  • natural organic fibres are a combination of cellulose fibres and ligno-cellulose fibres.
  • Fig. 1 the method of the present invention is illustrated, wherein in the initial fibres preparation step, stock natural organic fibres, such as cellulose fibres are being defibrated using already known methods.
  • the obtained defibrated natural organic fibres are suspended in water to obtain an aqueous solution.
  • aggregation and foaming of the natural organic fibres in aqueous solution is performed.
  • foam creation There are many methods supporting the foam creation during this phase. It could be done by injecting a gas through nozzles, shaking/ultrasounds, mechanical mixing or increasing the gas saturation by increasing the pressure in the mixing chamber (generating overpressure relative to the forming process pressure).
  • additional additives can be added.
  • mould filing is performed and foamed natural organic fibres are placed in a mould of arbitrary size and shape.
  • Three-dimensional mould is used to control the of shape the fibre network product as well as to limit the foamed material expansion during the fast thermodynamical process (scaling of production speed).
  • the mould has a plurality of pores to allow for evaporation of steam and gases during forming. The number of pores and its size allows for control of the density gradient and other physical characteristics of the fibre network product obtained in the method according to the present invention. Pores can be small, but also can have a form of missed walls or parts of the walls of the mould.
  • the mould is made of material, having a softening point above 100°C.
  • the mould is at least partially made of a dielectric material selected from PVC, PVL, silicon, PTFE, PTFE GF30, PP-H, PEEK, ceramics, or combination thereof.
  • the mould is made of dielectric material, having a softening point above 100°C.
  • EM material forming is performed as depicted in Fig. 1 .
  • electromagnetic energy is provided to the foamed natural organic fibres in the mould.
  • kind of electromagnetic energy in terms of frequency and power density is adapted to desired properties of the final fibre network product prepared.
  • electromagnetic energy having a frequency in a range of 10 - 100 MHz is provided to the foamed natural organic fibres.
  • This frequency range is preferable for implementation of electromagnetic energy delivery device in a form of parallel plate capacitor or almost parallel plate capacitor. Relation of wavelength to the device size allows for such implementation. Such implementation allows for automation of the material forming in continuous process, while the material is moving along parallel plates.
  • the capacitor is popular implementation in the industry around 27 - 35 MHz frequency range. Another advantage of this frequency range is that electromagnetic energy can be better dissipated in losses in natural organic fibrous material and polymer additives.
  • electromagnetic energy having a frequency in a range of 300 MHz - 25 GHz is provided to the foamed natural organic fibres.
  • This frequency range is preferable for implementation of electromagnetic energy delivery device in a form of a resonator, usually built as a closed cavity or a tunnel with the resonance inside the tunnel.
  • Another advantage of this frequency range is that electromagnetic energy can be better dissipated in water, especially at 2.4 GHz resonance of water particles.
  • the tunnel resonances are popular implementation in the industry around 900 MHz frequency.
  • electromagnetic energy used for forming a three-dimensional biodegradable fibre network product has a frequency in a range of 24.00 GHz - 24.25 GHz.
  • electromagnetic energy is provided uniformly. This can be achieved by a combination of uniform electromagnetic field generation technique and physical movement (longitudinal or rotations) of the mould within the semi-uniform electromagnetic field.
  • a ventilation system is used, allowing for removal of moisture from the space surrounding the form.
  • the efficiency of the ventilation increases for shorter forming times (higher powers of electromagnetic energy can be applied).
  • the delivery of warm air can further optimize the forming process in combination with the delivery of electromagnetic energy.
  • mould may be optionally unpacked and further drying of the obtained fibre network product can be done by applying a flow of dry air and conventional heating (with or without applying of electromagnetic energy). This optional step is marked as auxiliary drying on Fig. 1 .
  • Fig. 2 the shape of a closed mould according to an embodiment is illustrated.
  • Three of the four walls are flat and perpendicular to each other, the fourth is spherical. All of the outer surfaces have different normal vectors.
  • On the two flat walls and the spherical one there are pores in a form of round holes drilled through the walls. Diameters of those holes and distribution density are varied.
  • Fig. 3 the interior of a mould from Fig. 2 is illustrated for better understanding of the invention.
  • the walls of the mould limit and determine the shape of the formed material. They are themselves impermeable to water vapor, but thanks to the holes, water vapor escapes through three of the four walls of the mould.
  • Fig. 4 shows a cross section of the mould according to an embodiment (the same as shown in Fig. 3 and Fig. 4 ) with an indication of pressure gradients depending on mould shape and pore placements.
  • the temperature of the foamy material inside the mould increases simultaneously throughout the entire volume of the mould. It is because EM energy is accumulated over the entire volume of foamy material, i.e. by all the mass contained in the mould.
  • the temperature reaches the boiling point of water, an intense process of water vapor formation begins, the more intense the higher the power density used in the process. This creates a pressure build-up that seeks to escape through the pores in the mould walls.
  • the lines of the steam flow currents are shaped by pressure gradients, and those in the area of the pores coincide with the vectors normal to the wall surfaces in these places. Those lines of steam flow generate pressure on fibres, which are wet in the first phase of the process and susceptible to displacement and crushing. That is why the density of the final fibre network product may be non-uniform. Moreover, we can distinguish many directions along which the density increases. These density gradients coincide with the pressure gradients shown in Fig. 4 .
  • the steam leakage rate also depends on the size of individual pores, their shape, and the density of their distribution. As illustrated in Fig. 4 , more steam will flow through the area of the pores on the spherical wall at the same time than through the remaining open areas of the mould. This is due to the much larger diameter of the pores on the spherical wall and a relatively large number of them.
  • the density distribution in the product obtained from such mould has a smaller material density gradient from the spherical side, but it remains much more even over a large area - similar to the pressure gradient distribution shown in Fig. 4 .
  • Fragments of a final fibre network product obtained according to an embodiment, which was located adjacent to the flat walls in the regions corresponding to the pores in the mould have a greater density of the material, the fibre network product is strengthened, but only in a small area covered by the "action" of the mould pores. It is significant that from the side of the third flat wall, which is adjacent to the solid wall (without pores) of the mould, it is more difficult to distinguish a clear differentiation of density, the density gradient is absent, and the obtained fibre network product is softer.
  • pores in bottom part of the mould could normally serve as drainage holes for water excess removal by gravitation or by additional application of vacuum.
  • such process usually leads to some degradation of the foam.
  • the draining step is not used and excess of water is forced out of the mould by application of electromagnetic energy at a level which causes water boiling inside the mould.
  • parts of the mould are composed of metal parts of the electromagnetic field delivery device.
  • parallel metal plates of a capacitor can also serve as upper or lower walls of the mould allowing to form larger sheets of material.
  • parts of the mould or electromagnetic field delivery device have movable elements which allow automatizing the manufacturing process of material filling into the mould, travelling through the mould or removing it out of the mould after the formation of the final fibre network product.
  • a three-dimensional biodegradable fibre network product wherein the fibre network product is prepared from foamed natural organic fibres using electromagnetic energy, wherein the fibre network product has a density of 8 - 150 kg/m 3 and total porosity of more than 90%.
  • the product has a density of 8 - 90 kg/m 3 , preferably a density of 8 - 70 kg/m 3 , more preferably a density of 8 - 50 kg/m 3 , the most preferably a density of 8 - 30 kg/m 3 .
  • the physical properties of the structure according to the invention can be determined by the method described by the Research Station in Naaldwijk, Netherlands (Wever '2002). Used standards: PN-EN 13039 - determination of organic matter content, PN-EN 13041 - determination of total porosity, volume density, shrinkage, water and air capacity at a water potential of -10 cm H 2 O.
  • a fibre network product prepared by the method of the present invention having the following characteristics:
  • Fig. 5 shows water retention curve for the fibre network product according to an embodiment of the present invention.
  • the X-axis represents a potential from 0 to -10 cm H 2 O
  • the Y-axis represents water volume (vol %).
  • the fibre network product according to the embodiment of the present invention is characterized by high water and air capacity of more than 45%, which favours the growth of young plants such as seedlings.
  • the tested fibre network product in a form of cubes also have an appropriate pH of 6 - 7 and are characterized by a very low EC, which greatly facilitates the selection of optimal fertilization.
  • the preferred density of the fibre network product is about 70 kg/m 3 (in the range of 65 - 75 kg/m 3 ).
  • the fibre network product with such a density has the most advantageous air-water properties, similar to those of mineral wool.
  • the three-dimensional biodegradable fibre network product of the present invention can be preferably used as a plant growth substrate, filtration medium, filling and/or acoustic and mechanical damping structure.
  • the product was prepared according to the following steps:
  • the method presented in example 1 makes it possible to obtain structures with high mechanical strength and high impact strength in relation to their mass.
  • the product was prepared according to the following steps:
  • the highest density gradient is at the outer walls of the product and reaches 15 kg/m 3 on each 1 mm towards outside direction.
  • the method in example 2 allows to obtain a material with higher flexibility and is characterized by high acoustic insulation.
  • the product was prepared according to the following steps:
  • the method provided in example 3 allows to obtain a material with good water absorption and favourable air-water relation for plant growth.
  • the sample of the product was prepared according to the following steps:

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  • Manufacturing & Machinery (AREA)
  • Nonwoven Fabrics (AREA)
EP22154829.0A 2021-02-02 2022-02-02 Appareil et procédé de préparation d'un produit de réseau de fibres biodégradables tridimensionnel de fibres organiques naturelles Active EP4036307B1 (fr)

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EP24187389.2A Pending EP4435179A2 (fr) 2021-02-02 2022-02-02 Appareil et procédé de préparation d'un produit de réseau de fibres biodégradable tridimensionnel de fibres organiques naturelles
EP22154829.0A Active EP4036307B1 (fr) 2021-02-02 2022-02-02 Appareil et procédé de préparation d'un produit de réseau de fibres biodégradables tridimensionnel de fibres organiques naturelles

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EP24187389.2A Pending EP4435179A2 (fr) 2021-02-02 2022-02-02 Appareil et procédé de préparation d'un produit de réseau de fibres biodégradable tridimensionnel de fibres organiques naturelles

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Cited By (2)

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US20230074870A1 (en) * 2019-12-31 2023-03-09 Kimberly-Clark Worldwide, Inc. Foam-based manufacturing system and process
WO2024051915A1 (fr) * 2022-09-05 2024-03-14 Storopack Hans Reichenecker Gmbh Procédé permettant de fabriquer un article composé au moins en partie de fibres de cellulose, et article composé au moins en partie de fibres de cellulose

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Publication number Priority date Publication date Assignee Title
US20230074870A1 (en) * 2019-12-31 2023-03-09 Kimberly-Clark Worldwide, Inc. Foam-based manufacturing system and process
US11932988B2 (en) * 2019-12-31 2024-03-19 Kimberly-Clark Worldwide, Inc. Foam-based manufacturing system and process
WO2024051915A1 (fr) * 2022-09-05 2024-03-14 Storopack Hans Reichenecker Gmbh Procédé permettant de fabriquer un article composé au moins en partie de fibres de cellulose, et article composé au moins en partie de fibres de cellulose

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EP4036306A1 (fr) 2022-08-03
EP4036307C0 (fr) 2024-07-10
EP4036307B1 (fr) 2024-07-10

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