Method and system for producing a thermal insulator

Abstract

The present invention refers to a method and a system (1) for the preparation of a thermal insulator, a thermal insulator obtainable by said method and the use of the thermal insulator.

Description

[0001] METHOD AND SYSTEM FOR PRODUCING A THERMAL INSULATOR

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the area of thermal insulators. More specifically, the present invention relates to a method and a system for producing a thermal insulator.

[0004] BACKGROUND

[0005] Thermal insulation materials have received considerable interest for their use in many domestic and industrial applications, such as energy efficient buildings, household appliances, and many others. Ceramic materials have good thermal properties and are commonly used for applications where resistance to high temperatures is required.

[0006] Ceramic insulation materials are based in a blend of ceramic fibers and a suitable binder, processed with vacuum forming techniques. Vacuum forming is characterized by the use of a mold head which has a vacuum, or suction, applied to one side thereof. The mold head is applied to a fiber and binder slurry. As the slurry is drawn through the mold head the fibers deposit and the solvent is evacuated from the slurry.

[0007] Yet, this technique has significant drawbacks. The vacuum generates a flow of solvent through a void, frequently resulting in an inhomogeneous distribution of the fibers within the slurry. This ultimately leads to variations in the thickness and non-uniform material properties in the final product.

[0008] Some approaches to mitigate these deficiencies include modifying vacuum parameters or introducing an air flow into the slurry to disrupt the local flow. However, these techniques are time consuming and difficult to set up. In addition, vacuum forming cannot achieve high compaction of the final material, which typically displays low density and insufficient strength. The final product may have a rigid surface, but an interior often weak and friable.

[0009] Therefore, there is still a need in the industry of ceramic fiber insulation technology for an improved insulating material, having both desirable strength and insulation properties. Further, it would be desirable to provide such a product without relying on complex or costly processing techniques.

[0010] BRIEF DESCRIPTION OF THE INVENTION The authors of the present invention have developed a method for producing a thermal insulator, a system for carrying out the method and a thermal insulator obtainable by the method.

[0011] The method of the present invention allows the production of a robust and homogeneous thermal insulator with less defects and a reduced amount of free-powder. The method is intended to have great variability, with respect to the usable components and the properties of the thermal insulator which can be achieved therewith. Furthermore, since the method for the preparation of a thermal insulator of the present invention is a simple and cost-effective procedure, it can be applied for large-scale production of thermal insulators.

[0012] In addition, the method of the present invention allows a high degree of precision in the density and dimensions of the thermal insulator obtained. For example, the thickness values of the thermal insulators obtained by the method of the present invention have a dispersion percentage of less than 6% with respect to the desired central thickness value. Similarly, the density values obtained for the thermal insulators, with respect to the desired central density value, have a dispersion percentage of less than 10%.

[0013] In addition, the method of the present invention produces a reduced amount of scrap or waste material, in particular less than 8% by weight of the final weight of the thermal insulator obtained is waste material, thereby reducing production costs.

[0014] Therefore, a first aspect of the invention is directed to a method for producing a thermal insulator comprising the steps of:

[0015] (i) providing a first dispersion comprising: ceramic fibers; optionally, at least one inorganic filler; at least one first binder; optionally, at least one thickening agent; and a solvent;

[0016] (ii) subjecting the dispersion of step (i) to vacuum and / or pressure in a holder of a compaction system to obtain a first layered structure;

[0017] (iii) providing a further dispersion on top of the first layered structure obtained in step (ii), said dispersion comprising: optionally ceramic fibers; at least one inorganic filler; at least one second binder; optionally, at least one thickening agent; and a solvent;

[0018] (iv) subjecting the said dispersion and first layered structure to vacuum and / or pressure, and optionally heat, in the holder of the compaction system to obtain a second layered structure; wherein at least one binder is provided in the dispersion of step (i) and / or (iii);

[0019] (v) optionally performing steps (i)-(ii) and / or (iii)-(iv) a number “n” of times, wherein “n” is an integer, to obtain a further layered structure;

[0020] (vi) optionally applying an external layer onto the structure obtained in step (iv) or step (v);

[0021] (vii) heating the structure obtained in step (iv), step (v) and / or step (vi) at a temperature below 400 °C, preferably below 300 °C, to obtain a thermal insulator;

[0022] (viii) optionally performing step (vii) a number “m” of times, wherein “m” is an integer; wherein the compaction system comprises; a vessel comprising a holder configured for holding a dispersion; at least one pressing plate configured to be arranged facing the holder; feeding means configured for providing the dispersion within the vessel and onto the holder; drainage means configured for extracting a fluid phase of the dispersion out of the vessel such that a vacuum is applied to the dispersion provided onto the holder; and actuating means configured to: a. move the holder closer to the pressing plate; and / or b. move the pressing plate closer to the holder; such that a pressure is exerted onto the dispersion provided onto the holder; wherein the holder comprises a surface; and wherein the feeding means are adapted for pouring a dispersion at an angle nonperpendicular to the holder surface.

[0023] In a second aspect, the present invention is directed to a thermal insulator obtainable by the method as defined in the first aspect. In a third aspect, the present invention is directed to a compaction system for carrying out the method as defined in the first aspect, said compaction system comprising a vessel comprising a holder configured for holding a dispersion; at least one pressing plate configured to be arranged facing the holder; feeding means configured for providing the dispersion within the vessel and onto the holder; drainage means configured for extracting a fluid phase of the dispersion out of the vessel such that a vacuum is applied to the dispersion provided onto the holder; and actuating means configured to: a. move the holder closer to the pressing plate; and / or b. move the pressing plate closer to the holder; such that a pressure is exerted onto the dispersion provided onto the holder; wherein the holder comprises a surface; and wherein the feeding means are adapted for pouring a dispersion at an angle nonperpendicular to the holder surface.

[0024] In another aspect, the present invention is directed to the use of the thermal insulator of the invention, in boilers, water heaters and / or cooking burners.

[0025] In yet another aspect, the present invention is directed to the use of the thermal insulator of the invention in electric batteries.

[0026] These aspects and preferred embodiments thereof are additionally defined hereinafter in the detailed description and in the claims.

[0027] FIGURES

[0028] Figure 1 : Schematic representation of a compaction system.

[0029] Figure 2: Photograph showing a thermal insulator according to the invention.

[0030] Figure 3: Photograph showing thermal insulators according to the invention with different external layers. Figure 4 shows a scanning electron microscope (SEM) micrograph of a two-layer thermal insulator made by the method described in Example 1 wherein a binder was added in the first and the second dispersion of said method.

[0031] Figure 5 shows two thermal insulators: (a) one formed after pouring the dispersion no- perpendicularly to the holder flat surface and (b) another one formed after pouring the dispersion perpendicularly to the holder flat surface.

[0032] DETAILED DESCRIPTION OF THE INVENTION

[0033] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. As used herein, the singular forms “a” “an” and “the” include plural reference unless the context clearly dictates otherwise.

[0034] Method

[0035] In a first aspect, the present invention is directed to a method for producing a thermal insulator comprising the steps of

[0036] (i) providing a first dispersion comprising: ceramic fibers; optionally, at least one inorganic filler; at least one first binder; optionally, at least one thickening agent; and a solvent;

[0037] (ii) subjecting the dispersion of step (i) to vacuum and / or pressure in a holder of a compaction system to obtain a first layered structure;

[0038] (iii) providing a further dispersion on top of the first layered structure obtained in step (ii), said further dispersion comprising:

[0039] -optionally ceramic fibers;

[0040] -at least one inorganic filler;

[0041] -at least one second binder;

[0042] -optionally, at least one thickening agent; and

[0043] -a solvent;

[0044] (iv) subjecting said dispersion and first layered structure to vacuum and / or pressure in the holder of the compaction system to obtain a second layered structure; optionally applying heat; wherein at least one binder is provided in the dispersion of step (i) or (iii);

[0045] (v) optionally performing steps (i)-(ii) and / or (iii)-(iv) a number “n” of times, wherein “n” is an integer, to obtain a further layered structure;

[0046] (vi) optionally applying an external layer onto the structure obtained in step (iv) or step (v);

[0047] (vii) heating the structure obtained in step (iv), step (v) and / or step (vi) at a temperature below 400 °C, preferably below 300 °C, to obtain a thermal insulator;

[0048] (viii) optionally performing step (vii) a number “m” of times, wherein “m” is an integer; wherein the compaction system comprises; a vessel comprising a holder configured for holding a dispersion; at least one pressing plate configured to be arranged facing the holder; feeding means configured for providing the dispersion within the vessel and onto the holder; drainage means configured for extracting a fluid phase of the dispersion out of the vessel such that a vacuum is applied to the dispersion provided onto the holder; and actuating means configured to: a. move the holder closer to the pressing plate; and / or b. move the pressing plate closer to the holder, such that a pressure is exerted onto the dispersion provided onto the holder; wherein the holder comprises a surface; and wherein the feeding means are adapted for pouring a dispersion at an angle nonperpendicular to the holder surface.

[0049] The authors of the present invention have observed that the use of the compaction system in the process of the present invention leads to a specific microstructure on the final thermal insulator. Moreover, the use of the compaction system reduces the time employed in the process over other types of techniques.

[0050] Step (i)

[0051] The method of the present invention comprises a step (i) of providing a dispersion comprising: ceramic fibers; optionally, at least one inorganic filler; at least one first binder; optionally, a thickening agent; and a solvent.

[0052] Ceramic fibers

[0053] In the context of the present invention, the term “ceramic fibers” refers to fibers of ceramic materials such as ceramic oxides, non-oxide ceramics or combinations thereof. Nonlimiting examples of “ceramic oxides” are alumina, alumina-silica, alumina-boria-silica, aluminum borosilicate, alumina-mullite, silica, zirconia, zirconia-silica, titania, titania- silica, rare earth oxides, alkaline earth silicate (AES) or a combination thereof. Non limiting examples of “non-oxide ceramics” are silicon carbide, silicon carbonitride, silicon oxycarbide, silicon titanium oxycarbide, silicon nitride, aluminum nitride, silicon titanium, silicon alumina nitride or a combination thereof.

[0054] The dispersion of step (i) comprises ceramic fibers.

[0055] In a particular embodiment, the ceramic fibers are selected from commercially available ceramic fibers. Non-limiting examples of commercially available ceramic fibers include glass fibers, quartz fibers, aluminum borosilicate fibers, silica fibers, non-oxide fibers (for example, silicon carbide, silicon carbonitride, silicon oxycarbide, silicon titanium oxycarbide), as well as those ceramic oxide fibers marketed by 3M Company (Saint Paul, MN) under the trade designation "NEXTEL" (for example, "NEXTEL 312", "NEXTEL 440", "NEXTEL 550", "NEXTEL 610", "NEXTEL 650", and "NEXTEL 720"), by BelChem Fiber Materials GmbH (Freiberg, Germany) under the trade designation "BELCOTEX", by COI Ceramics Company under the trade designation of “NICALON FIBER” (for example, “NICALON”, “HI-NICALON” and “Hi-Nicalon Type S”), by UBE Industries under the trade designation of “Tyranno fiber”, by Hitco Carbon Composites, Inc. (Gardena, CA) under the trade designation "REFRASIL" or by Unifrax Corporation under the trade designation “FIBERFRAX”.

[0056] In a more particular embodiment, the ceramic fibers are selected from silicon carbide (SiC) fibers, silicon carbonitride (SiCN) fibers, alumina (AI2O3) fibers, alumina-mullite fibers, aluminum borosilicate fibers and silica (SiO2) fibers; preferably selected from silicon carbide (SiC) fibers, silicon carbonitride (SiCN) fibers, aluminium borosilicate fibers and silica fibers (SiO2); more preferably silicon carbide (SiC) fibers. In a particular embodiment, the ceramic fibers are in the form of individual fibers, bundles, yarns or a fabric; preferably in the form of individual fibers.

[0057] In the context of the present invention, the term “dispersed” means the opposite of aggregated or agglomerated.

[0058] In a particular embodiment, the ceramic fibers have diameters between 0.5 and 50 microns; preferably between 1 and 30 microns; more preferably between 5 and 15 microns.

[0059] In a particular embodiment, the ceramic fibers have lengths between 0.1 and 50 mm; preferably between 0.2 and 30 mm; more preferably between 0.5 and 15 mm.

[0060] In the context of the present invention, the expressions “fiber thickness” or “fiber diameter” are synonyms. In the context of the present invention the expression “fiber diameter” or “fiber diameters” relates to the shorter dimension of a fiber. In the context of the present invention the expression “fiber length” or “fiber lengths” relates to the longer dimension of a fiber.

[0061] In a particular embodiment, the ceramic fibers have aspect ratios of between 30 and 3000, preferably between 200 and 1000, more preferably between 300 and 800, even more preferably between 400 and 600.

[0062] In the context of the present invention, the expression “aspect ratio” relates to the ratio of the fiber sizes in different dimensions. As a non-limiting example the aspect ratio of a fiber is the ratio of its longer side or its length to its shorter side or its diameter or thickness, i.e. if a fiber has a length of 40000 microns and a diameter of 20 microns, its aspect ratio is 2000.

[0063] In a particular embodiment, the ceramic fibers are in a concentration between 0.1 and 20 g / L; preferably between 0.5 and 10 L, more preferably between 1 and 5 g / L.

[0064] In a particular embodiment, the ceramic fibers are in a concentration between 0.01 and 2 wt% relative to the total weight of the dispersion; preferably between 0.05 and 1 wt%, more preferably between 0.1 and 0.5 wt% relative to the total weight of the dispersion.

[0065] In an embodiment, the ceramic fibers comprise Si; preferably comprise Al and Si; more preferably comprise SiC>2 and AI2O3.

[0066] In an embodiment, the ceramic fibers are man-made.

[0067] In a particular embodiment, the ceramic fibers are hydrophobic. In a more particular embodiment, at least part of the ceramic fibers are a plurality of manmade inorganic fibers not comprising hydroxyl groups (OH) on their surface such as annealed man-made inorganic fibers; preferably wherein said plurality of man-made inorganic fibers have a mean diameter equal or over 6 microns. In a more particular embodiment, part of the ceramic fibers are a plurality of man-made inorganic fibers not comprising hydroxyl groups (OH) on their surface such as annealed man-made inorganic fibers; and the rest of the ceramic fibers comprise hydroxyl groups (OH) on their surface.

[0068] In another more particular embodiment, all the ceramic fibers are a plurality of man-made inorganic fibers not comprising hydroxyl groups (OH) on their surface such as annealed man-made inorganic fibers; preferably wherein said plurality of man-made inorganic fibers have a mean diameter equal or over 6 microns

[0069] In the context of the present invention, the expression “man-made fibers” refers to fibers not occurring naturally, such as artificial fibers, that consist essentially of inorganic materials such as ceramic oxides, non-oxide ceramics or combinations thereof.

[0070] Filler

[0071] In the context of the invention, the term “filler” refers to a particulate material of inorganic nature that is added to the dispersion to provide a particular property or reduce cost. In particular, the inorganic filler may provide for further improved mechanical properties such as a reduced shrinkage rate of the obtained thermal insulator.

[0072] The dispersion of step (iii) comprises at least an inorganic filler. In a particular embodiment, the dispersion of step (i) comprises at least an inorganic filler.

[0073] Exemplary inorganic fillers include, but are not limited to kaolin clay, metakaolin clay, talc, mica, mullite, phlogopite, muscovite montmorillonite, smectite, bentonite, illite, chlorite, sepiolite, attapulgite, halloysite, vermiculite, laponite, rectorite, perlite, silicon dioxide (e. g. fumed silica), alumina, and combinations thereof.

[0074] In a particular embodiment, the filler is selected from the group consisting of kaolin clay, metakaolin clay, perlite, vermiculite, silicon dioxide, alumina, and combinations thereof. Preferably, the filler is selected from the group consisting of silicone dioxide such as fumed silica; alumina and combinations thereof.

[0075] The filler may be in granular or powder form. In a particular embodiment, the filler has a particle size of between 1 and 80 pm, preferably between 4 and 15 pm.

[0076] In a particular embodiment, the at least one filler is at a concentration between 0.1 and 20 g / L of the dispersion, preferably between 0.5 and 15 g / L, more preferably between 1 and 10 g / L.

[0077] In a particular embodiment, the at least one filler is at a concentration between 0.01 and 2 wt% relative to the total weight of the dispersion, preferably between 0.05 and 1.5 wt%, more preferably between 0.1 and 1 wt% relative to the total weight of the dispersion.

[0078] In a particular embodiment, the at least one filler is hydrophobic; preferably the at least one inorganic filler is hydrophobic. In a more particular embodiment, at least part of the at least one filler is hydrophobic; preferably the at least one inorganic filler is hydrophobic.

[0079] In an embodiment, the term “hydrophobic” is understood as commonly known in the art, in particular, a material such as a filler or a ceramic fiber, is considered hydrophobic when the angle formed between a droplet of liquid (usually water) and its surface is greater than 90 degrees when measured by a contact angle measurement technique, for example as the one often described in ISO 19403-1 :2017 and related standards.

[0080] Binder

[0081] In the context of the present invention, the term “binder” refers to a substance that helps the ceramic particles to stick together by adhesion or cohesion. In the context of the present invention the expression “first binder” refers to a binder in the dispersion of step (i) and the expression “second binder” refers to a binder added in step (iii).

[0082] As used herein, either one of a first binder or a second binder may be organic or inorganic. The first and second binder may be the same binder or binder mixture, or a different binder or binder mixture.

[0083] Non-limiting examples of organic binders are carbohydrates, thermoplastic polymers, polyacrylates, polyurethanes, epoxy resins, phenol resins, thermo curing resins, light sensitive resins, polyester resins and / or a combination thereof.

[0084] Non-limiting examples of inorganic binders include colloidal silica, colloidal alumina, water-soluble silicates such as sodium silicate and potassium silicate, and phosphates such as aluminum phosphate.

[0085] In a particular embodiment, the at least one first binder of step (i) is an organic binder. In a more particular embodiment, the first binder is preferably selected from a carbohydrate, thermoplastic polymer, polyacrylate, polyurethane, epoxy resin, phenol resin, thermocuring resin, light sensitive resin, polyester resin and / or a combination thereof.

[0086] In a particular embodiment, the carbohydrate is a monomeric or polymeric carbohydrate; more preferably cellulose, starch or dextrin; even more preferably cellulose.

[0087] In a particular embodiment, the thermoplastic polymer is selected from polyvinylalcohol (PVA), polyhydroxyethyl methacrylate polyvinylalcohol (PVA), poly(methyl methacrylate) (PMMA), polycarbonate (PC), polystyrene (PS), polypropylene (PP), polyethylene (PE), polyglycolide (PGA), poly(propylenefumarate) (PPF), polycyanoacrylate (PCA), polycaprolactone (PCL), poly(glycerol sebacate) (PGS), poly(glycerol sebacate acrylate) (PGSA), polyvinylidenefuoride (PVDF), polyvinylidene chloride (PVDC), polyethylene terephthalate (PET), polybutylene therephtalate (PBT), polyphenylene oxide (PPG), polyimide (PI), polyvinyl chloride (PVC), cellulose acetate (CA), cyclic olefin copolymer (COC), ethylene vinyl acetate (EVA), ethylene vinyl alcohol (EVOH), polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), perfluoroalkoxy (PEA), ethylene tetrafluoroethylene (ETFE), polyethersulfone (PES), chlorinated poly ethylene (CPE), polylactic acid (PLA), poly 3-hydroxybutyrate (P3HB), polybutylene adipate (PBA), polyethylene adipate (PEA), polybutylene succinate (PBS), polyphenylene sulfide (PPS), polysulfone (PSU), polytrimethylene terephthalate (PTT), polyurethane (Pll), polyvinyl acetate (PVA), polyvinylidene chloride (PVDC), styrene acrylonitrile (SAN), polyetherketones (PEEK), polyhydroxyethylmethacrylate (PHEMA), poly(N-isopropylacrylamide) (PNIPAAm) and mixtures thereof.

[0088] In a particular embodiment, the at least one first binder of step (i) is a vinyl polymer selected from polyvinyl chloride (PVC), poly(vinyl acetate) and polyvinyl alcohol (PVA); preferably polyvinyl alcohol (PVA).

[0089] In a particular embodiment, the at least one first binder of step (i) is an inorganic binder.

[0090] In a more particular embodiment, the inorganic binder is a water-soluble silicate. Nonlimiting examples of water-soluble silicates include alkali metal silicates and polysilicates, such as potassium silicate or sodium silicate, also referred to as water glass.

[0091] In a more particular embodiment, the inorganic binder is a phosphate, preferably selected from phosphoric acid or a metal phosphate salt such as an aluminum phosphate.

[0092] In a particular embodiment, the inorganic binder is selected from colloidal silica or colloidal alumina. In a more particular embodiment, the inorganic binder is selected from silica sols commercially available under trade name LUDOX® from DuPont Corporation or alumina sols commercially available under trade name ALUMINASOL® from Nissan Chemical.

[0093] In a particular embodiment, the first binder of step (i) is a combination of an organic binder and an inorganic binder.

[0094] In a particular embodiment, the at least one first binder of step (i) is at a concentration between 0.1 and 10 g / L, preferably between 0.2 and 5 g / L, more preferably between 0.5 and 2 g / L of the dispersion.

[0095] In a particular embodiment, the at least one first binder of step (i) is at a concentration between 0.005 and 1 wt% relative to the total weight of the dispersion, preferably between 0.01 and 0.5%, more preferably between 0.05 and 0.2 wt% relative to the total weight of the dispersion.

[0096] Thickener

[0097] In a particular embodiment, the dispersion comprises at least one thickener; preferably the dispersion of step (i). In the context of the present invention, the term “thickener” refers to a compound that increases the density of the dispersion of step (i). Suitable thickeners according to the present invention include alginates, modified starches, a gum such as guar gum, xanthan gum, acacia, synthetic thickeners, or the like. In a preferred embodiment, the thickener is a gum selected from guar gum, xanthan gum, acacia or a combination thereof.

[0098] In a particular embodiment, the at least one first binder of step (i) is at a concentration between 0.1 and 20 g / L, preferably between 1 and 10 g / L of the dispersion.

[0099] In a particular embodiment, the at least one thickener of step (i) is at a concentration between 0.01 and 2% wt% relative to the total weight of the dispersion, preferably between 0.1 and 1 % wt% relative to the total weight of the dispersion.

[0100] Dispersion

[0101] In the context of the present invention, the expression “dispersion” refers to a mixture or a slurry of at least one solid element, such as ceramic fibers, dispersed in a solvent.

[0102] In a particular embodiment, the solids of the dispersion consist of all the components of the dispersion except the solvent. Non-limiting examples of solvents suitable for the present invention are methanol, 2- propanol, chloroform, toluene, anisole, cyclohexane, dimethyl formamide, methanol, dichloromethane, trichloroethane, water, acetone, ethyl acetate, N-methyl-2-pyrrolidone and mixtures thereof.

[0103] In a particular embodiment, the dispersion comprises a solvent selected from methanol, ethanol and water; preferably water. Preferably, the solvent of the dispersion is water.

[0104] In another particular embodiment, the dispersion comprises an amount of solids of less than 30 g / L of the dispersion; preferably less than 25 g / L; more preferably less than 20 g / L; even more preferably less than 15 g / L of dispersion.

[0105] In a particular embodiment, the dispersion of step (i) has a viscosity between 1 mPa-s (Cps) and 10000 mPa-s (Cps), preferably of between 10 and 5000 mPa-s (Cps), more preferably of between 50 and 2000 mPa-s (Cps), even more preferably between 50 and 1000 mPa-s (Cps).

[0106] In a particular embodiment, the dispersion of step (i) is stable.

[0107] The dispersion provided in step (i) may be prepared by dispersing the ceramic fibers and the at least one first binder and / or thickening agent and, optionally, other additives, in a suitable solvent by applying energy via mechanical methods known in the art for example by means of dispersers, agitators or by ultrasonic baths and or probes. Other alternatives known in the art to prepare stable dispersions that are suitable for the invention include the addition of surface tension control additives (surfactants) to the dispersion, or modification of the ceramic fibers surface by bound or unbound ligand molecules. The dispersion quality may be assessed by the stability of the dispersions during a certain time without flocculation or precipitation. In particular, the ceramic fibers should not aggregate and flocculate in the time frame of the fabrication process, i.e.: from several minutes to hours. Turbidimetry or nephelometry and / or dynamic light scattering can be used for monitoring the stability of the dispersions.

[0108] In a particular embodiment, the dispersion of step (i) further comprises at least one surfactant. Suitable surfactants include anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants or combinations thereof. Exemplary of the anionic surfactant are carboxylic acid, sulfuric acid ester, sulfonic acid, and phosphoric acid ester type surfactants. Exemplary of the cationic surfactant are amine salt, primary amine salt, secondary amine salt, tertiary amine salt, and quaternary amine salt type surfactants. Exemplary of the nonionic surfactant are ester, ester-ether, and ether type surfactants. Exemplary of the amphoteric surfactant are amino acid and sulfo-betaine type surfactants.

[0109] In a more preferred embodiment, the dispersion of step (i) comprises: about 2 to 5 g / L of ceramic fibers; about 5 to 7 g / L of inorganic filler; about 0.5 to 1 .5 g / L of a first binder; and water.

[0110] In another more preferred embodiment, the dispersion of step (i) consists of: about 2 to 5 g / L of ceramic fibers; about 5 to 7 g / L of inorganic filler; about 0.5 to 1 .5 g / L of a first binder; and water.

[0111] Step (ii)

[0112] The step (ii) of the method of the invention is directed to subjecting the dispersion of step (i) to vacuum and / or pressure in a holder of a compaction system to obtain a first layered structure.

[0113] In the context of the present invention, the term “layered structure” refers to a planar element comprising physically entangling ceramic fibers. Additionally, in the context of the present invention the expression “layered structure” refers to a planar element that may be a monolayer structure, a bi-layer structure or a multi-layer structure. As will be understood by those skilled in the art each step of the method of the invention involving subjecting to pressure and / or vacuum a dispersion comprising ceramic fibers will lead to the formation of a further layer in the layered structure.

[0114] In a particular embodiment, the pressure of step (ii) is applied by moving the holder closer to the at least one pressing plate and / or moving the at least one pressing plate closer to the holder to a final closed position within the vessel through the actuating means. In a more particular embodiment, the holder and the pressing plate are moved to a predetermined final position where they are spaced apart by less than 30 mm, preferably less than 25 mm, more preferably less than 20 mm such that an equivalent thickness is imparted to the structure of step (ii).

[0115] In a preferred embodiment, the pressure applied onto the dispersion in step (ii) is between 0.1 and 100 bar, preferably between 1 and 10 bar.

[0116] In a particular embodiment, the vacuum of step (ii) is applied by extracting a fluid phase of the dispersion out of the vessel through the draining means. In a preferred embodiment, the vacuum is applied by extracting the fluid phase, e. g., the solvent of the dispersion, at a rate between 0.1 and 10 L / s, preferably between 0.5 and 3 L / s, more preferably at a rate of about 1 L / s.

[0117] In a preferred embodiment, the dispersion is subjected to pressure and vacuum simultaneously.

[0118] In a particular embodiment, step (ii) is performed during a period of between 1 and 100 seconds, preferably between 5 and 50 seconds, more preferably between 10 and 40 seconds.

[0119] In a particular embodiment, step (i) and step (ii) are performed sequentially.

[0120] In a particular embodiment of the method for providing a thermal insulator of the present invention, step (i) of providing a dispersion; and step (ii) of subjecting said dispersion to pressure and / or vacuum in a compaction system are performed simultaneously. Without being bound to any theory in particular, the authors believe that subjecting the dispersion of step (i) to vacuum and pressure in the compaction system improves the uniformity in the deposition of the fibers in the resulting material and its homogeneity, and thus it improves the strength and resistance to high temperatures of the thermal insulator of the present invention.

[0121] Step (Hi)

[0122] The step (iii) of the method of the present invention is directed to providing a further dispersion on top of the first layer structure obtained in step (ii).

[0123] The dispersion of step (iii) comprises: at least one inorganic filler; at least one second binder; and a solvent.

[0124] The at least one inorganic filler of the dispersion of step (iii) may be the same or different from the optional at least one inorganic filler of the dispersion of step (i) as defined above.

[0125] In an embodiment, the at least one inorganic filler of step (i) and / or of step (iii) is selected form the group consisting of kaolin clay, metakaolin clay, talc, mica, mullite, phlogopite, muscovite montmorillonite, smectite, bentonite, illite, chlorite, sepiolite, attapulgite, halloysite, vermiculite, laponite, rectorite, perlite, fumed silic a, alumina, and combinations thereof.

[0126] The at least one second binder of the dispersion of step (iii) may be the same or different from the first binder of the dispersion of step (i) as defined above.

[0127] In an embodiment, the at least one second binder of the dispersion of step (iii) is an inorganic binder. Suitable examples of inorganic binders are those as described above for the dispersion of step (i). In a preferred embodiment, the inorganic binder of the dispersion of step (iii) is selected from colloidal silica, colloidal alumina, a water-soluble silicate, a phosphate binder or a mixture thereof.

[0128] In a particular embodiment, the inorganic binder is selected from colloidal silica or colloidal alumina.

[0129] In another particular embodiment, the inorganic binder is selected from sodium silicate, potassium silicate or a mixture thereof. In a more particular embodiment, the inorganic binder is sodium silicate.

[0130] In a further particular embodiment, the inorganic binder is a phosphate, preferably selected from phosphoric acid or a metal phosphate salt. In a more preferred embodiment, the inorganic binder is aluminum phosphate.

[0131] In another particular embodiment, the at least one second binder of the dispersion of step (iii) is an organic binder. Suitable examples of organic binders are those as described above for the dispersion of step (i). In a more particular embodiment, the second binder is preferably selected from a carbohydrate, thermoplastic polymer and a combination thereof.

[0132] In a more particular embodiment, the at least one second binder is a carbohydrate, preferably a monomeric or polymeric carbohydrate; more preferably cellulose, starch or dextrin; even more preferably cellulose.

[0133] In another more particular embodiment, the at least one second binder of the dispersion of step (iii) is a vinyl polymer selected from polyvinyl chloride (PVC), poly(vinyl acetate) and polyvinyl alcohol (PVA); preferably polyvinyl alcohol (PVA).

[0134] In a particular embodiment, the at least one second binder of step (iii) is at a concentration between 5 and 35% wt% relative to the total weight of the dispersion, preferably between 10 and 30% wt% relative to the total weight of the dispersion.

[0135] In another particular embodiment, the at least one second binder of step (iii) is at a concentration of between 0.1 and 10 g / L, preferably at a concentration of between 0.5 and 5 g / L.

[0136] In another particular embodiment, the dispersion of step (iii) comprises at least one thickening agent. Suitable thickening agents are those as described above for the dispersion of step (i).

[0137] Suitable solvents for the dispersion of step (iii) are those as described above in step (i). In a particular embodiment, the solvent of the dispersion of step (iii) is the same solvent as in the dispersion of step (i). In another particular embodiment, the solvent of the dispersion of step (iii) is a different solvent from the solvent in the dispersion of step (i). Preferably, the solvent of the dispersion of step (iii) is water.

[0138] In a particular embodiment, the dispersion of step (iii) further comprises ceramic fibers. Suitable ceramic fibers are those as described above for the dispersion of step (i) in any of its particular embodiments. In a particular embodiment, the ceramic fibers of the dispersion of step (iii) are the same ceramic fibers as in the dispersion of step (i). In another particular embodiment, the ceramic fibers of the dispersion of step (iii) are different from the ceramic fibers in the dispersion of step (i).

[0139] In a preferred embodiment, the dispersion of step (iii) does not comprise ceramic fibers.

[0140] In a more preferred embodiment, the dispersion of step (i) comprises: at least one inorganic filler; about 0.5 to 5 g / L of colloidal silica or colloidal alumina as a second binder; and water.

[0141] In another more preferred embodiment, the dispersion of step (i) comprises: at least one inorganic filler; about 10 to 30% wt% of sodium silicate as a second binder relative to the total weight of the dispersion; and water.

[0142] Step (iv)

[0143] The step (iv) of the method of the present invention is directed to subjecting the dispersion of step (iii) and first layered structure of step (ii) to vacuum and / or pressure in the holder of the compaction system including the structure obtained in the previous step to obtain a second layered structure; optionally applying heat.

[0144] In a particular embodiment, the pressure of step (iv) is applied by moving the holder closer to the at least one pressing plate and / or moving the pressing plate closer to the holder to a final closed position within the vessel through the actuating means. In a more particular embodiment, the holder and the pressing plate are moved to a predetermined final position where they are spaced apart by less than 30 mm, preferably less than 25 mm, more preferably less than 20 mm within the vessel such that a target thickness is imparted to the structure of step (iv).

[0145] In a preferred embodiment, the pressure applied onto the dispersion in step (iv) is between 0.1 and 100 bar, preferably between 1 and 10 bar.

[0146] In a particular embodiment, the vacuum of step (iv) is applied by extracting a fluid phase of the dispersion out of the vessel through the draining means. In a preferred embodiment, the vacuum is applied by extracting the fluid phase, e. g., the solvent of the dispersion, at a rate between 0.1 and 10 L / s, preferably between 0.5 and 3 L / s, more preferably at a rate of about 1 L / s.

[0147] In a preferred embodiment, the dispersion is subjected to pressure and vacuum simultaneously.

[0148] In a particular embodiment, step (iv) further comprises applying heat. In a particular embodiment, heat is applied by passing a flow of air at a temperature of 50 to 400 °C, preferably at temperature of 200-250 °C through the vessel of the compaction system comprising the holder. In a more particular embodiment, the flow of air is of 1000 to 3000 L / min.

[0149] In a particular embodiment, step (iv) is performed during a period of between 1 and 300 seconds, preferably between 1 and 100 seconds, preferably between 5 and 50 seconds, more preferably between 10 and 40 seconds.

[0150] In a particular embodiment of the method of the present invention, step (iii) of providing a further dispersion into a compaction system including the structure obtained in the previous step; and step (iv) of subjecting said dispersion to pressure and / or vacuum are performed simultaneously. In another particular embodiment, step (iii) and step (iv) are performed sequentially.

[0151] In a particular embodiment, the layered structure obtained in step (iv) is a bilayer structure wherein each layer has the same ceramic fibers and a different binder or binder mixture in its composition. In another particular embodiment, the layered structure obtained in step (iv) is a bilayer structure wherein each layer has different ceramic fibers and a different binder or binder mixture in its composition. In a preferred embodiment, the layered structure obtained in step (iv) is a one-layer structure comprising ceramic fibers and a binder mixture in its composition.

[0152] In the process of the present invention, at least one first or second binder is provided in either the dispersion of step (i) or (iii).

[0153] The authors of the present invention have observed that the use of at least one first binder in the dispersion improves the stability of said dispersion, i.e. reduces the precipitation and / or flocculation of the ceramic fibers.

[0154] Additionally, the authors of the present invention believe that the use of a first and a second binder in separate steps reduces or eliminates problems associated to chemical incompatibility and improves adhesion between the fibers. This leads to fewer defects and improved properties of the final thermal insulator.

[0155] Step (v)

[0156] In the present invention, the method described above may comprise a step (v) of performing steps (i)-(ii) and / or (iii)-(iv) a number “n” of times to obtain a further layered structure, wherein “n” is an integer.

[0157] In a particular embodiment, steps (i)-(ii) and / or (iii)-(iv) are performed from 1 to 10 times, preferably between 1 and 5 times. In another particular embodiment, steps (i)-(ii) are performed 1 , 2, or 3 times. In a further particular embodiment, steps (iii)-(iv) are performed 1 , 2, or 3 times. In a particular embodiment, step (v) comprises performing steps (i)-(ii) and (iii)-(iv) 1 , 2 or 3 times.

[0158] In a particular embodiment, the layered structure obtained in step (v) has from 2 to 8 layers. In a more particular embodiment, the layered structure has 2 layers, 3 layers, 4 layers or 5 layers.

[0159] In a particular embodiment, each layer of the layered structure has the same ceramic fibers and a different binder or binder mixture in its composition. In another particular embodiment, each layer of the layered structure has different ceramic fibers and a different binder or binder mixture in its composition.

[0160] In a particular embodiment, each layer of the layered structure has the same thickness. In another particular embodiment, each layer of the layered structure has a different thickness.

[0161] Without being bound to any particular theory, the authors believe that the addition of multiple layers subject to pressure and vacuum in the compaction system of the present invention, results in a better adhesion between the layers in the layered structure respect to other techniques known in the art.

[0162] Step (vi)

[0163] In the present invention, the method described above may comprise a step (vi) of applying an external layer onto the structure obtained in step (iv) or step (v).

[0164] In a particular embodiment, step (vi) comprises: a. placing an external layer on top of the layered structure of step (iv) or (v) b. joining the external layer and the layered structure by applying pressure.

[0165] In a particular embodiment, the pressure of step (b) is applied by moving the holder closer to the at least one pressing plate and / or moving a pressing plate closer to the holder to a final closed position within the vessel through the actuating means. In a more particular embodiment, the holder and the pressing plate are moved to a final position within the vessel where said holder and pressing plate are spaced apart by less than 30 mm, preferably less than 25 mm, more preferably less than 20 mm.

[0166] In a preferred embodiment, the pressure applied in step (vi) is between 0.1 and 100 bar, preferably between 1 and 10 bar.

[0167] In a particular embodiment, step (vi) is performed during a period of between 1 and 100 seconds, preferably between 5 and 50 seconds, more preferably between 10 and 40 seconds.

[0168] In a particular embodiment, the external layer of step (vi) is a metallic substrate such as a metal plate or a metal mesh. In a preferred embodiment, the external layer is a metal mesh, preferably a metal mesh with a mesh size of 30 or more, preferably 40 or more, more preferably 60 or more, even more preferably 80 or more. In another particular embodiment, the metal mesh has a wire diameter of 0.3 mm or less. In a more particular embodiment, the metal of the metallic substrate is selected from steel, nickel, copper or mixtures thereof, preferably steel such as stainless steel. In another particular embodiment, the external layer is a non-woven substrate.

[0169] In a further particular embodiment, the external layer is a coating material, preferably a coating material comprising hollow glass microspheres, more preferably with a bulk density between 0.10 and 0.80 g / cm3 and / or a particle size between 1 and 30 pm.

[0170] In a particular embodiment, the external layer has a thickness of between 0.01 and 2 mm.

[0171] In an embodiment, the external layer partially covers one surface of the layered structure. In a preferred embodiment, the external layer totally covers one surface of the layered structure.

[0172] Step (vii)

[0173] In the present invention the method described above comprises a step (vii) of heating the structure obtained in step (iv), (v) or (vi) at a temperature below 400 °C, preferably below 300 °C to obtain a thermal insulator.

[0174] In a particular embodiment, the heating of step (vii) is performed under pressure. In a preferred embodiment, the pressure is applied by moving the holder holding the structure obtained in step (iv), (v) or (vi) closer to a pressing plate and / or moving a pressing plate closer to the holder to a predetermined final position within the vessel through the actuating means, preferably to a final position within the vessel where said holder and pressing plate are spaced apart by less than 30 mm, preferably less than 25 mm, more preferably less than 20 mm, such that an equivalent thickness is imparted to the thermal insulator.

[0175] In a preferred embodiment, the pressure applied onto the structure in step (vii) is between 0.1 and 100 bar, preferably between 1 and 10 bar.

[0176] In a particular embodiment, the heating of step (vii) is performed during a period of between 1 and 100 seconds, preferably between 10 and 50 seconds, more preferably between 10 and 40 seconds.

[0177] In a particular embodiment, the heating of step (vii) is performed under air. In a more particular embodiment, the heating of step (vii) is performed by applying a flow of air to the layered structure of step (iv), (v) or (vi) at a temperature of 50 to 400 °C, preferably at temperature of 200-250 °C. In a more particular embodiment, the flow of air is of 1000 to 3000 L / min. Step (viii)

[0178] The method of the present invention optionally comprises a step (viii) of repeating step (vii) a number “m” of times, wherein “m” is an integer;

[0179] Preferably, m is 1 , 2 or 3.

[0180] In a particular embodiment, step (viii) is performed by applying a flow of air at a temperature of 50 to 400 °C, preferably at temperature of 200-250 °C for each repetition of step (vii). In a more particular embodiment, the flow of air is of 1000 to 3000 L / min.

[0181] In a particular embodiment, step (viii) is performed under pressure for each repetition of step (vii). In a preferred embodiment, the pressure is applied by moving the holder closer to a pressing plate and / or moving a pressing plate closer to the holder to a predetermined final position within the vessel through the actuating means. In a more particular embodiment, the holder and the pressing plate are moved to a final position within the vessel where said holder and pressing plate are spaced apart by less than 300 mm, preferably less than 25 mm, more preferably less than 20 mm, such that an equivalent thickness is imparted to the thermal insulator.

[0182] In a particular embodiment, the heating is performed during a period of between 1 and 100 seconds, preferably between 5 and 50 seconds, more preferably between 10 and 40 seconds for each repetition of step (vii).

[0183] The heating of step (vii), and optionally step (viii) allows to stabilize and dry the layered structure by removing any residual solvent present therein.

[0184] In a particular embodiment, the method of the present invention may further comprise a step (ix) of subjecting the thermal insulator obtained in step (vii) or (viii) to thermal curing.

[0185] In the context of the present invention, the term “thermal curing” refers to heating the thermal insulator obtained in step (vii) or (viii) at a temperature high enough to at least partially decompose any organic components present in the thermal insulator such as the first and / or second binder, thickening agents or other organic additives used in the method of the invention.

[0186] In a particular embodiment, the thermal curing is performed at a temperature between 300 and 800 °C, preferably for a period between 0.5 and 24 hours, preferably between 1 and 12 hours.

[0187] In the context of the present invention the expression “to decompose” in relation to said at least one first binder from said nonwoven layer refers to a thermal decomposition.

[0188] In a particular embodiment, the curing is performed in a furnace; preferably in a vacuum furnace; more preferably in a hot wall vacuum furnace.

[0189] In a particular embodiment, the curing is performed under inert gas or under air; preferably under inert gas; more preferably under N2 gas.

[0190] In an embodiment, step (ix) comprises: a. coating the stabilized structure obtained in step (vii) or (viii) with a further binder; and b. heating the structure of step (a) at a temperature of between 300 and 800 °C to obtain a cured thermal insulator.

[0191] The coating of step (a) may be performed by any coating technique known in the art. Non-limiting examples of coating techniques include dip coating, spray-coating, vapor deposition and brush coating techniques. In a particular embodiment, the coating of step (b) is performed by spray-coating.

[0192] The binder of step (a) may be any binder as described herein. In a particular embodiment, the binder is an inorganic binder. In a more particular embodiment, the binder is an inorganic binder comprising colloidal silica. In a preferred embodiment, the inorganic binder is selected from colloidal silica, colloidal alumina, water-soluble silicates, phosphates or a combination thereof.

[0193] In another embodiment, the binder is an organic binder. In a more particular embodiment, the organic binder is a carbohydrate, thermoplastic polymer, polyacrylate, polyurethane, epoxy resin, phenol resin, thermocuring resin, light sensitive resin, polyester resin and / or a combination thereof. In a preferred embodiment, the organic binder is a polyacrylate, a polyester resin and / or a combination thereof.

[0194] The authors have observed that coating the material with a further binder helps ceramic fibers to stick together by adhesion and / or cohesion. Furthermore, the authors of the present invention have observed that coating the material with a further binder has a stabilizing effect and improves durability of the thermal insulator.

[0195] Without being bound by any particular theory, the authors of the present invention have observed that a thermal insulator obtained by the method of the invention has a homogeneous structure with very few defects and a highly uniform thickness. This improves the strength, durability and resistance to high temperatures of the material. The authors of the present invention have observed that the final properties of the thermal insulator obtained by the method of the invention, might be modulated by modifying the characteristics of the dispersions and the number of pressure / vacuum steps.

[0196] In a particular embodiment, the method of the present invention comprises the steps of:

[0197] (i) providing a first dispersion comprising: ceramic fibers; optionally, at least one inorganic filler; at least one first binder; and a solvent;

[0198] (ii) subjecting the dispersion of step (i) to vacuum and pressure in a holder of a compaction system to obtain a first layered structure;

[0199] (iii) providing a further dispersion on top of the first layered structure obtained in step (ii), said dispersion comprising: optionally ceramic fibers; at least one inorganic filler; at least one second binder; and a solvent;

[0200] (iv) subjecting said dispersion and first layered structure to vacuum and pressure in the holder of the compaction system to obtain a second layered structure;

[0201] (v) performing steps (i)-(ii) and / or (iii)-(iv) a number “n” of times, wherein “n” is an integer, to obtain a further layered structure;

[0202] (vii) heating the structure obtained in step (v) at a temperature below 400 °C, preferably below 300 °C, to obtain a thermal insulator.

[0203] In a more particular embodiment, the process of the invention further comprises step (viii) of performing step (vii) a number “m” of times, wherein “m” is an integer selected from 1 , 2 or 3.

[0204] In an alternative embodiment, the method of the present invention comprises of the steps of:

[0205] (i) providing a first dispersion comprising: ceramic fibers; optionally, at least one inorganic filler, at least one first binder; and a solvent;

[0206] (ii) subjecting the dispersion of step (i) to vacuum and pressure in a holder of a compaction system to obtain a first layered structure;

[0207] (iii) providing a further dispersion on top of the first layered structure obtained in step (ii), said dispersion comprising: optionally ceramic fibers; at least one inorganic filler; at least one second binder; and a solvent;

[0208] (iv) subjecting said dispersion and first layered structure to vacuum and pressure in the holder of the compaction system to obtain a second layered structure;

[0209] (vi) applying an external layer onto the structure obtained in step (iv);

[0210] (vii) heating the structure obtained in step (vi) at a temperature below 400 °C, preferably below 300 °C, to obtain a thermal insulator.

[0211] In a more particular embodiment, the process of the invention further comprises step

[0212] (viii) of performing step (vii) a number “m” of times, wherein “m” is an integer selected from 1, 2 or 3.

[0213] In a more particular embodiment, in step (v) n is 1 , 2 or 3.

[0214] In a more particular embodiment, in step (v) n is 1 and steps (i) and (ii) are repeated once. In another more particular n is 1 and steps (iii) and (iv) are repeated once. In a further more particular embodiment, n is 2 and steps (i)-(ii) are repeated once and steps (iii)-(iv) are repeated once.

[0215] In another particular embodiment, the method of the present invention comprises of the steps of:

[0216] (i) providing a first dispersion comprising: ceramic fibers; optionally, at least one inorganic filler; at least one first binder; and a solvent;

[0217] (ii) subjecting the dispersion of step (i) to vacuum and pressure in a holder of a compaction system to obtain a first layered structure;

[0218] (iii) providing a further dispersion on top of the first layered structure obtained in step (ii), said dispersion comprising: at least one inorganic filler; at least one second binder; and a solvent;

[0219] (iv) subjecting said dispersion and first layered structure to vacuum and pressure in the holder of the compaction system to obtain a second layered structure;

[0220] (v) performing steps (i)-(ii) and / or (iii)-(iv) a number “n” of times, wherein “n” is an integer, to obtain a further layered structure;

[0221] (vi) applying an external layer onto the structure obtained in step (v);

[0222] (vii) heating the structure obtained in step (vi) at a temperature below 400 °C, preferably below 300 °C, to obtain a thermal insulator.

[0223] In a more particular embodiment, in step (v) n is 1, 2 or 3.

[0224] In a more particular embodiment, in step (v) n is 1 and steps (i) and (ii) are repeated once. In another more particular n is 1 and steps (iii) and (iv) are repeated once. In a further more particular embodiment, n is 2 and steps (i)-(ii) are repeated once and steps (iii)-(iv) are repeated once.

[0225] In a preferred embodiment, the method of the present invention comprises the steps of

[0226] (i) providing a first dispersion comprising: ceramic fibers; optionally, at least one inorganic filler; at least one first binder; and a solvent;

[0227] (ii) subjecting the dispersion of step (i) to vacuum and pressure in a holder of a compaction system to obtain a first layered structure;

[0228] (iii) providing a further dispersion on top of the first layered structure obtained in step (ii), said dispersion comprising: at least one inorganic filler; at least one second binder; and a solvent;

[0229] (iv) subjecting said dispersion and first layered structure to vacuum and pressure in the holder of the compaction system to obtain a second layered structure;

[0230] (vii) heating the structure obtained in step (iv) at a temperature below 400 °C, preferably below 300 °C, to obtain a thermal insulator; preferably wherein the at least one first binder is an organic binder and the at least one second binder is an inorganic binder.

[0231] More preferably, the process of the invention further comprises step (viii) of performing step (vii) a number “m” of times, wherein “m” is an integer selected from 1, 2 or 3.

[0232] In another preferred embodiment, the method of the present invention consists of the steps of:

[0233] (i) providing a first dispersion comprising: ceramic fibers; optionally, at least one inorganic filler; at least one first binder; and a solvent;

[0234] (ii) subjecting the dispersion of step (i) to vacuum and pressure in a holder of a compaction system to obtain a first layered structure;

[0235] (iii) providing a further dispersion on top of the first layered structure obtained in step (ii), said dispersion comprising: at least one inorganic filler; at least one second binder; and a solvent;

[0236] (iv) subjecting said dispersion and first layered structure to vacuum and pressure in the holder of the compaction system to obtain a second layered structure;

[0237] (vii) heating the structure obtained in step (iv) at a temperature below 400 °C, preferably below 300 °C, to obtain a thermal insulator; preferably wherein the at least one first binder is an organic binder and the at least one second binder is an inorganic binder.

[0238] In an embodiment, the compaction system of the method of the invention comprises: a vessel comprising a holder configured for holding a dispersion; at least one pressing plate configured to be arranged facing the holder; feeding means configured for providing the dispersion within the vessel and onto the holder; drainage means configured for extracting a fluid phase of the dispersion out of the vessel such that a vacuum is applied to the dispersion provided onto the holder; and actuating means configured to: a. move the holder closer to the pressing plate (4); and / or b. move the pressing plate closer to the holder, such that a pressure is exerted onto the dispersion provided onto the holder ; wherein the holder comprises a surface; and wherein the feeding means are adapted for pouring a dispersion at an angle non-perpendicular to the holder surface.

[0239] In an embodiment, the steps of providing a first and / or subsequent dispersion(s) of the method of the present invention comprise pouring said first or subsequent dispersion(s) through the feeding means into the holder of the vessel of the compaction system at an angle non-perpendicular to the holder surface of the compaction system; preferably at an angle of less than 85 degrees; preferably of less than 80 degrees; more preferably at an angle of between 10 and 80 degrees.

[0240] In a particular embodiment, feeding means are adapted for pouring a dispersion at an angle non-perpendicular to the holder surface, wherein the intersection between the dispersion being poured and the holder surface does not form a right angle. In the context of the present invention, “right angles” are understood as in the art, such as angles that are about 90 degrees.

[0241] In a particular embodiment, the feeding means comprises a surface with a plurality of through apertures; wherein the longitudinal axis of the through apertures is not perpendicular to the surface of the feeding means; preferably wherein the angle formed between longitudinal axis of the through apertures and the surface is of less than 85 degrees; preferably of less than 80 degrees; more preferably is between 10 and 80 degrees.

[0242] In the context of the present invention, it is understood that the angle formed between the longitudinal axis of the through apertures and the surface of the feeding means is the angle formed by the longitudinal axis of the through apertures with its orthogonal projection over said surface.

[0243] In a more particular embodiment, the feeding means comprises a surface with a plurality of through apertures; wherein the longitudinal axis of the through apertures is not perpendicular to the surface of said feeding means, and wherein the through apertures are concentrically situated among each other. The longitudinal axis of the through apertures is understood as the axis that connects one side of the surface of the feeding means to the opposite side of the surface.

[0244] In a particular embodiment, the feeding means comprises a surface formed by a plurality of blades joined among them in the central axis of said surface such that they form a plurality of through apertures; preferably wherein the longitudinal axis of the through apertures is not perpendicular to the surface. In a more particular embodiment, the blades are flat or curved; preferably curved.

[0245] In a particular embodiment, a vessel comprising a holder of the compaction system is arranged in a rotary rack and a plurality of pressing plates is arranged circumferentially such that said vessel may be relocated to regularly spaced positions about a central axis of the rotary rack.

[0246] In a more particular embodiment, the vessel comprising a holder of the compaction system is relocated to a different position about the central axis of the rotary rack after completion of each step (i)-(viii) of the method.

[0247] In a particular embodiment, the method of the invention comprises: a) performing step (i) while maintaining a vessel comprising a holder of the compaction system in a first position about a central axis of the rotary rack such that a first pressing plate is facing the holder; b) relocating the vessel from the first position to a second position about a central axis of the rotary rack such that a second pressing plate is facing the holder; and performing step (ii) while maintaining the vessel comprising a holder of the compaction system in said second position; c) relocating the vessel to a third position about a central axis of the rotary rack, where a third pressing plate is facing the holder; and performing step (iii) while maintaining the vessel comprising a holder of the compaction system in said third position; d) relocating the vessel to a fourth position about a central axis of the rotary rack, where a fourth pressing plate is facing the holder; and performing step (iv) while maintaining the vessel comprising the holder in said fourth position; e) relocating the vessel to a fifth position about a central axis of the rotary rack, preferably where a further pressing plate is facing the holder; and performing step (vii) while maintaining the vessel comprising the holder in said fifth position. In a more particular embodiment, the method of the invention further comprises performing step (viii) of repeating step (vii) a number “m” of times, wherein “m” is an integer, preferably being “m” 1 , 2 or 3; wherein the vessel comprising a holder of the compaction system is relocated to a further position about the central axis of the rotary rack for each instance of step (vii).

[0248] In a further particular embodiment, the method of the invention comprises: a') performing steps (i) and (ii) simultaneously while maintaining a vessel comprising a holder of the compaction system in a first position about a central axis of the rotary rack such that a first pressing plate is facing the holder; b’) relocating the vessel from the first position to a second position about a central axis of the rotary rack such that a second pressing plate is facing the holder; and performing steps (iii) and (iv) simultaneously while maintaining the vessel comprising a holder of the compaction system in said second position; c’) relocating the vessel to a final position about a central axis of the rotary rack, preferably where a further pressing plate is facing the holder; and performing step (vii), while maintaining the vessel comprising a holder of the compaction system in said final position.

[0249] In more particular embodiment, after step (b’), the method comprises: d) relocating the vessel from a second position to a third position about a central axis of the rotary rack, preferably such that a third pressing plate is facing the holder; and performing step (vi), while maintaining the vessel comprising a holder of the compaction system in said third position.

[0250] In an alternative embodiment, after step (b’) the method comprises: e) performing step (v) of repeating steps (i)-(ii) or (iii)-(iv), wherein n is 1 , 2 or 3, wherein the vessel comprising a holder of the compaction system is relocated to a different position about the central axis of the rotary rack where a further pressing plate is facing the holder for each repetition of step (i)-(ii) or (iii)-(iv) .

[0251] In a more particular embodiment, after step (e) the method comprises: f) relocating the vessel from a third position to a further position about a central axis of the rotary rack, preferably such that a further pressing plate is facing the holder; and performing step (vi).

[0252] In a particular embodiment, each stage of (a) to (f) is performed during an equal period of time, preferably a period of between 1 and 100 seconds, preferably between 5 and 50 seconds, more preferably between 10 and 40 seconds.

[0253] In a particular embodiment, the vessel comprising a holder of the compaction system is repositioned to the first position about the central axis of the rotary rack after ejection of the thermal insulator of step (vii) or step (viii). In a further particular embodiment, the vessel comprising a holder is repositioned to the first position about the central axis of the rotary rack after a cleaning process of the compaction system.

[0254] The thermal insulator of step (vii) or step (viii) may be ejected by moving the holder containing said structure out of the vessel through the actuating means. A cleaning process of the compaction system may be performed by passing therethrough a cleaning fluid such as pressurized water or air.

[0255] In a particular embodiment, a plurality of vessels is arranged in said rotary rack and a plurality of pressing plates is arranged circumferentially, wherein each of the plurality of vessels is located in a position wherein the holder of said vessel faces a pressing plate; and wherein a step (i)-(viii) of the method is performed in each vessel simultaneously.

[0256] Particular and preferred embodiments of the compaction system are described below.

[0257] Thermal insulator

[0258] According to a third aspect, the present invention is directed to a thermal insulator obtainable by the method for the preparation of thermal insulators as defined above in any of its embodiments.

[0259] In a particular embodiment, the thermal insulator of the present invention has one layer. In another particular embodiment, the thermal insulator has two layers. In a further particular embodiment, the thermal insulator has multiple layers, preferably three to eight layers, more preferably three, four or five layers.

[0260] In a particular embodiment, each layer the thermal insulator has different ceramic fibers in their composition. In an alternative embodiment, each layer of the thermal insulator has the same ceramic fibers in their composition.

[0261] In a more particular embodiment, each layer of the thermal insulator has a different binder or binder mixture in their composition. In an alternative embodiment, each layer of the thermal insulator has the same binder or binder mixture in their composition. In a particular embodiment, each layer the thermal insulator has the same thickness. In an alternative embodiment, each layer of the thermal insulator has a different thickness.

[0262] In a particular embodiment, the thermal insulator has a thickness between 10 and 30 mm, preferably between 10 and 25 mm, more preferably between 15 and 20 mm.

[0263] In a particular embodiment, the thermal insulator has a density between 10 kg / m3 y 500 kg / m3, preferably between 50 kg / m3 y 350 kg / m3, more preferably between 150 and 300 kg / m3.

[0264] Compaction system

[0265] In another aspect, the invention is directed to a compaction system (1) for carrying out the method as defined in the previous aspect, said compaction system comprising a vessel (2) comprising a holder (3) configured for holding a dispersion; at least one pressing plate (4) configured to be arranged facing the holder; feeding means (5) configured for providing the dispersion within the vessel and onto the holder; drainage means (6) configured for extracting a fluid phase of the dispersion out of the vessel such that a vacuum is applied to the dispersion provided onto the holder; and actuating means (7) configured to: a. move the holder (3) closer to the pressing plate (4); and / or b. move the pressing plate (4) closer to the holder (3), such that a pressure is exerted onto the dispersion provided onto the holder (3); wherein the holder (3) comprises a surface; and wherein the feeding means (5) are adapted for pouring a dispersion at an angle nonperpendicular to the holder (3) surface.

[0266] An exemplary embodiment of the compaction system according to the invention is illustrated in Figure 1. The reference numbers used throughout the description relate to the attached Figures.

[0267] The compaction system suitable for the present invention includes a vessel, a holder receivable in one end of the vessel and a pressing plate receivable in the opposite end of the vessel so as to form an enclosure, said holder and pressing plate being spaced at a predetermined distance and arranged substantially parallel. The holder and the pressing plate are mounted such that they can independently move axially inward and outward of the vessel.

[0268] Vessel

[0269] In the context of the present invention, the term “vessel” refers to any size or shape receptacle suitable for carrying out the method of the invention.

[0270] In a particular embodiment, the vessel is a tubular receptacle. In a more particular embodiment, the vessel is a tubular receptacle with a rectangular, square or circular cross section. In a preferred embodiment the cross section is circular. In a particular embodiment, the diameter of the cross section is between 10 and 50 cm, preferably between 15 and 30 cm.

[0271] Holder

[0272] As used herein, the term holder refers to a component suitable for holding and, in some embodiments, containing a dispersion.

[0273] In a particular embodiment, the holder comprises a planar of flat surface arranged to be facing a dispersion. In a more particular embodiment, the planar surface of the holder has a circular shape, preferably with a diameter between 10 and 50 cm, preferably between 15 and 30 cm.

[0274] In a preferred embodiment, the planar surface comprises a plurality of perforations such as holes, channels and / or slits.

[0275] In a more preferred embodiment, the holder is a first punch. As used herein, the term "punch" refers to a tool that is movable in a bore and functions as a piston for compacting a material.

[0276] Pressing plate

[0277] As used herein, the term pressing plate reefers to any component suitable for being pressed against a dispersion.

[0278] In a particular embodiment, the pressing plate comprises a planar surface arranged to be facing a dispersion. In a more particular embodiment, the planar surface of the pressing plate has a circular shape, preferably with a diameter between 10 and 50 cm, preferably between 15 and 30 cm.

[0279] In a preferred embodiment, the planar surface comprises a plurality of perforations such as holes, channels and / or slits.

[0280] In a preferred embodiment, the pressing plate is a second punch.

[0281] The holder and the pressing plate can be manufactured from materials common in the art including, but not limited to, steel, aluminum, brass, stainless steel and composites.

[0282] In a particular embodiment, the holder is a first punch and the pressing plate is a second punch, each comprising a planar surface having a plurality of perforations such as holes, channels and / or slits. The perforations may arranged in a variety of patterns such as a series of concentric circles, a spiral-shape or a non-regular pattern. In a preferred embodiment.

[0283] In a particular embodiment, the size, type and / or number of perforations is different in the first punch and in the second punch. Preferably, the size of the perforations is larger in the second punch than in the first punch.

[0284] Feeding means

[0285] The compaction system further comprises feeding means. The feeding means can be any means suitable for providing a dispersion within the vessel and into the holder.

[0286] The feeding means are adapted for pouring a dispersion at an angle non-perpendicular to the holder surface; preferably at an angle of less than 85 degrees; more preferably at an angle of less than 80 degrees; more preferably at an angle of between 10 and 80 degrees.

[0287] In a particular embodiment, feeding means are adapted for pouring a dispersion at an angle non-perpendicular to the holder surface, wherein the intersection between the dispersion being poured and the holder surface does not form a right angle.

[0288] In a particular embodiment, the feeding means comprises a surface with a plurality of through apertures; wherein the longitudinal axis of the through apertures is not perpendicular to said surface; preferably wherein the longitudinal axis of the through apertures is not perpendicular to said surface; more preferably wherein the angle formed in the intersection between longitudinal axis of the through apertures and the surface is of less than 85 degrees; preferably of less than 80 degrees; more preferably is between 10 and 80 degrees. In the context of the present invention, it is understood that the angle formed between the longitudinal axis of the through apertures and a surface, is the angle formed by the longitudinal axis of the through apertures with its orthogonal projection over said surface.

[0289] In a more particular embodiment, the feeding means comprises a surface with a plurality of through apertures; wherein the longitudinal axis of the through apertures is not perpendicular to said surface and wherein the through apertures are concentrically situated among each other in the surface.

[0290] The longitudinal axis of the through apertures is understood as the axis that connects one side of the surface of the feeding means to the opposite side of the surface.

[0291] In a particular embodiment, the feeding means is provided on the holder and / or the pressing plate. In a preferred embodiment, the feeding means are provided in the pressing plate.

[0292] In a particular embodiment, the feeding means further comprises pressure regulating means configured for modifying the dispersion supply pressure. In another particular embodiment, the feeding means further comprises flow regulating means configured for modifying the dispersion supply flow.

[0293] Draining means

[0294] The compaction system further comprises draining means. The draining means can be any means suitable for suctioning a fluid phase of the dispersion out of the vessel.

[0295] In a preferred embodiment, the drainage means are provided in the holder and / or the pressing plate. In a more preferred embodiment, the drainage means are provided in the holder. In an even more preferred embodiment the drainage means comprises a plurality of holes.

[0296] In a particular embodiment, the drainage means comprises pumping means configured for suctioning the fluid phase of the dispersion out of the vessel.

[0297] Actuating means

[0298] Actuating means are provided on the compaction system. The actuating means can be any means suitable for moving the holder and / or the pressing plate to the different positions they hold in the method of the invention.

[0299] In one embodiment, the actuating means are automated means, preferably automated means with a hydraulic, pneumatic or electric system. In a preferred embodiment, the actuating means are electrically operated servomechanisms. In a more preferred embodiment, the actuating means comprises at least one servo-motor.

[0300] In a particular embodiment, the compaction system further comprises control means configured to control the actuating means such that the holder and the pressing plate are arranged so as to be separated by a predetermined distance.

[0301] In a preferred embodiment, the vessel comprises a first punch configured for holding a dispersion and a second punch configured to be arranged facing the first punch.

[0302] In an embodiment, said first and second punches each has a planar surface comprising perforations.

[0303] In an embodiment, the feeding means comprise a plurality of holes.

[0304] In an embodiment, the drainage means comprise a plurality of holes.

[0305] In an embodiment, the actuating means are electrically operated servomechanisms.

[0306] In a particular embodiment, the compaction system comprises a plurality of vessels arranged in a rotary rack and a plurality of pressing plates arranged circumferentially, wherein the rotary rack is configured to rotate such that each of the plurality of vessels is located in a position wherein the holder of the vessel faces a pressing plate.

[0307] In a particular embodiment, the rotary rack comprises control means configured for controlling the rotation of the rotary rack to locate each of the plurality of vessels in a position wherein the holder of the vessel faces a pressing plate.

[0308] Uses

[0309] In another aspect, the present invention is directed to the use of a thermal insulator as defined in any of the embodiments above in boilers, water heaters and / or cooking burners using a gas or a mixture of gases; but preferably using hydrogen or mixtures of gases comprising hydrogen. In a particular embodiment, the thermal insulator is used in burner doors.

[0310] In a particular embodiment, the mixture of gases is a mixture of gases comprising a hydrocarbon or hydrogen; preferably is a hydrocarbon / air mixture or a hydrogen / air mixture. Non limited examples of hydrocarbons suitable for the present invention are propane, butane or methane.

[0311] In another aspect, the present invention is directed to the use of a thermal insulator as defined in any of the embodiments above in electric batteries applications, preferably as a separator, as a partition member adapted for forming a partition between two battery cells or between a single battery cell and a member other than said single battery cell, and / or as part of a battery housing.

[0312] In an embodiment, the use of a thermal insulator as defined in any of the embodiments above is for thermal insulation of batteries; preferably of electric vehicles.

[0313] The uses described above may be also drafted as methods comprising a step of thermal isolating at least part of boiler, water heater and / or cooking burner, or an electric battery using the thermal insulator as defined in any of the embodiments of above.

[0314] All the features described in this specification (including the claims, description and drawings) and / or all the steps of the described method can be combined in any possible combination, with the exception of combinations of such mutually exclusive features and / or steps. In addition, all the embodiments and preferred characteristics of the ceramic fibers, inorganic fillers, binders, thickening agents may apply to the ceramic fibers, inorganic fillers, binders, thickening agents of the thermal insulator or of different method steps with the exception of combinations of such mutually exclusive features and / or steps. The invention will be further illustrated by means of examples which should not be interpreted as limiting the scope of the claims.

[0315] EXAMPLES

[0316] The invention is illustrated by means of the following examples which in no case limit the scope of the invention.

[0317] Example 1 : Preparation of a thermal insulator.

[0318] A thermal insulator was prepared as follows.

[0319] Ceramic fibers obtained under the trademark designation “BELCOTEX®” from BELCH EM were used. The fibers were dispersed in 20 L water at a concentration of 4 g / L by applying mechanical energy using a disperser in an open vessel. Alumina powder of 5 pm mean diameter was added to the dispersion as a filler to a concentration of 6 g / L, and cationic starch (Vector® SC from Roquette) as a binder to a concentration of 1 g / L.

[0320] A compaction system as shown in Figure 1 was used to create a one layer structure.

[0321] The first dispersion was poured into a holder in the vessel of the compaction system and a layered structure comprising the ceramic fibers, alumina and starch with a thickness below 30 mm was formed by pressing against and suction dewatering the dispersion. Said layer structure was formed on the holder of the compaction system under a pressure of between 0.1 bar and 10 bar during 20 seconds created applying pressure by forcing a pressing plate against the dispersion to a final target thickness of the layered structure within the vessel and onto the holder while suction dewatering the dispersion by a vacuum pump.

[0322] Then, a second dispersion was prepared adding water glass, / . e., sodium silicate (Nasil® 3.35 from IQE) to 1 L water as a second binding agent at a 10% in weight over the total weight of the dispersion.

[0323] The second dispersion was poured into a holder in the vessel of the compaction system and forced through the first layered structure previously formed by suction dewatering and pressing against the dispersion. A second layered structure was formed on the holder of the compaction system comprising the ceramic fibers, alumina, starch and water glass with a thickness below 20 mm (aprox. 19 mm). The layered structure was formed under a pressure of between 0.1 bar and 10 bar during 20 seconds created applying pressure by forcing a pressing plate against the dispersion to the final target thickness of the layered structure within the vessel and onto the holder while suction dewatering the dispersion by a vacuum pump.

[0324] The layered structure was stabilized and dried under heating at a temperature between 200-250 °C to stabilize and dry the thermal insulator, while applying a pressure of 0.1 bar to 10 bar by forcing a pressing plate against the layered structure. Then, the stabilized structure was demolded by ejecting the holder from the vessel.

[0325] Figure 2 shows a thermal insulator obtained according to Example 1.

[0326] Example 2: Preparation of a thermal insulator with an external layer. A thermal insulator was prepared according to Example 1 , but adding a metallic mesh (stainless steel, wire diameter <0.3 mm) as an external layer onto the layered structure before stabilization and drying. Alternatively, a glass microspheres coating (TiC>2 coated hollow glass microspheres from Cospheric) was applied.

[0327] The metallic mesh was deposited on top of the layered structure formed by ceramic fibers, alumina, starch and glass water on the holder of the compaction system with a thickness of approximately 19 mm, and joined by forcing a pressing plate against the layered structure to a final target position within the vessel and onto the holder. A layered structure with an external metallic mesh was formed under a pressure of between 0.1 bar and 10 bar during 20 seconds.

[0328] Figure 3 shows a thermal insulator obtained according to Example 2 with (a) an external metallic mesh or (b) glass microspheres coating material for the external layer. The insert in Figure 3 shows a detail of the surface microstructure of a thermal insulator coated with an external layer of hollow glass microspheres.

[0329] Example 3: Preparation of a thermal insulator with different binder distribution

[0330] Three different two-layer thermal insulators made by the method described in Example 1 were compared. All of them comprised alumina as inorganic binder. However, said inorganic binder was added in different steps of the process of example 1 : in the first dispersion; in the second dispersion or in both of them.

[0331] Scanning electron microscope (SEM) and chemical analysis results (not shown herein) showed that when the binder is added to only one of the dispersions of the process, the final two-layer thermal insulators obtained have most of the binder on one of their faces. However, when the binder is added in the first and second dispersions of the process, the two-layer thermal insulator obtained has a more homogeneous distribution of the binder, an improved chemical compatibility within and between the layers as well as an improved adhesion between the fibers and the rest of the components, resulting in fewer defects, lees-free powder and better mechanical properties. Figure 4 shows a scanning electron microscope (SEM) micrograph of a two-layer thermal insulator made by the method described in Example 1 wherein alumina was added in the first and the second dispersion of said method. The micrograph shows a homogeneous dispersion and good interaction between the binder, the fillers and the ceramic fibers.

[0332] Example 4: Preparation of a thermal insulator using a compaction system with different feeding means Two-layer thermal insulators, produced using the method described in Example 1 , but wherein the first dispersion was poured into the holder of the compaction system using different feeding means, were compared.

[0333] Results showed that when the feeding means are adapted for pouring the corresponding dispersion at an angle which is not perpendicular to the holder surface, the final thermal insulator has less defects.

[0334] Figure 5 shows two thermal insulators: (a) one formed after pouring the dispersion no- perpendicularly to the holder surface and (b) another one formed after pouring the dispersion perpendicularly to the holder surface. A few creaks and defects can be observed on the thermal insulator of the figure 5b. Figure 5a shows a thermal insulator, formed pouring the dispersion not perpendicularly to the longitudinal dimension of the final layer structure, and having less defects and a better dispersion of the components leading to less free powder.

Claims

CLAIMS1 . Method for producing a thermal insulator comprising the steps of:(i) providing a first dispersion comprising:-ceramic fibers;-optionally, at least one inorganic filler;-at least one first binder;-optionally, at least one thickening agent; and-a solvent;(ii) subjecting the dispersion of step (i) to vacuum and / or pressure in a holder of a compaction system to obtain a first layered structure;(iii) providing a further dispersion on top of the first layer structure obtained in step (ii), said further dispersion comprising:-optionally ceramic fibers;-at least one inorganic filler;-at least one second binder;-optionally, at least one thickening agent; and-a solvent;(iv) subjecting said dispersion and first layered structure to vacuum and / or pressure in the holder of the compaction system to obtain a second layered structure; optionally applying heat; wherein at least one binder is provided in the dispersion of steps (i) or (iii);(v) optionally performing steps (i)-(ii) and / or (iii)-(iv) a number “n” of times, wherein “n” is an integer, to obtain a further layered structure;(vi) optionally applying an external layer onto the structure obtained in step (ii), step (iv) or step (v);(vii) heating the structure obtained step (iv), step (v) and / or step (vi) at a temperature below 400 °C, preferably below 300 °C, to obtain a thermal insulator;(viii) optionally performing step (vii) a number “m” of times, wherein “m” is an integer; wherein the compaction system (1) comprises: a vessel (2) comprising a holder (3) configured for holding a dispersion; at least one pressing plate (4) configured to be arranged facing the holder;feeding means (5) configured for providing the dispersion within the vessel and onto the holder; drainage means (6) configured for extracting a fluid phase of the dispersion out of the vessel such that a vacuum is applied to the dispersion provided onto the holder; and actuating means (7) configured to: a. move the holder (3) closer to the pressing plate (4); and / or b. move the pressing plate (4) closer to the holder (3), such that a pressure is exerted onto the dispersion provided onto the holder (3); wherein the holder (3) comprises a surface; and wherein the feeding means (5) are adapted for pouring a dispersion at an angle non-perpendicular to the holder (3) surface.

2. The method according to claim 1 , wherein a vessel comprising a holder of the compaction system is arranged in a rotary rack and a plurality of pressing plates is arranged circumferentially such that the vessel may be relocated to regularly spaced positions about a central axis of the rotary rack; and wherein the vessel comprising a holder of the compaction system is relocated to a different position about the central axis of a rotary rack after completion of each step (i)-(viii) of the method.

3. The method according to claim 1 or 2, wherein in said compaction system the vessel comprises a first punch configured for holding a dispersion and a second punch configured to be arranged facing the first punch; wherein the feeding means and / or drainage means comprise a plurality of holes; and wherein the actuating means are electrically operated servomechanisms.

4. The method according to any of the previous claims, wherein the process further comprises a step (ix) of subjecting the thermal insulator obtained in step (vii) or (viii) to thermal curing at a temperature of 300 to 800 °C.

5. The method according to any of the previous claims, wherein the at least one inorganic filler of step (i) and / or of step (iii) is selected form the group consisting of kaolin clay, metakaolin clay, talc, mica, mullite, phlogopite, muscovitemontmorillonite, smectite, bentonite, illite, chlorite, sepiolite, attapulgite, halloysite, vermiculite, laponite, rectorite, perlite, fumed silica, alumina, and combinations thereof.

6. The method according to any of the previous claims, wherein the at least one first binder in step (i) is an organic binder.

7. The method according to any of the previous claims, wherein the at least one second binder in step (iii) is an inorganic binder.

8. The method according to any of the previous claims, wherein the at least one first binder in step (i) is an organic binder and wherein the at least one second binder in step (iii) is an inorganic binder.

9. The method according to any of the previous claims, wherein the inorganic binder comprises colloidal alumina, colloidal silica, water glass, or a mixture thereof.

10. The method according to any of the previous claims, wherein the organic binder is selected from the group consisting of a polymeric binder, preferably selected from a carbohydrate, thermoplastic polymer, polyacrylate, polyurethane, epoxy resins, phenol resins, thermocuring resins, light sensitive resins, polyester resins or a combination thereof.11 . The method according to any of the previous claims, wherein the ceramic fibers are made of ceramic oxides, non-oxide ceramics or combinations thereof, preferably, wherein the ceramic fibers are made of silicon carbide (SiC), silicon carbonitride (SiCN), alumina (AI2O3), alumina-mullite, aluminum borosilicate, silica (SiO2), alkaline earth silicate (AES) or combinations thereof.

12. The method according to any of the previous claims, wherein the external layer of step (vi) is selected from a metallic mesh, a non-woven substrate or a coating material, preferably a coating material comprising hollow glass microspheres.

13. A thermal insulator obtainable by the method according to any of claims 1 to 12.

14. Compaction system (1) for carrying out the method according to any of claims 1 to 12 comprising: a vessel (2) comprising a holder (3) configured for holding a dispersion; at least one pressing plate (4) configured to be arranged facing the holder; feeding means (5) configured for providing the dispersion within the vessel and onto the holder; drainage means (6) configured for extracting a fluid phase of the dispersion out of the vessel such that a vacuum is applied to the dispersion provided onto the holder; and actuating means (7) configured to: a. move the holder (3) closer to the pressing plate (4); and / or b. move the pressing plate (4) closer to the holder (3); wherein the holder (3) comprises a surface; and wherein the feeding means (5) are adapted for pouring a dispersion at an angle non-perpendicular to the holder (3) surface.

15. The compaction system according to claim 14, wherein the vessel comprises a first punch configured for holding a dispersion and a second punch configured to be arranged facing the first punch; wherein the feeding means and / or drainage means comprise a plurality of holes; and wherein the actuating means are electrically operated servomechanisms.

16. The system according to any one of claims 14 or 15, further comprising a plurality of vessels arranged in a rotary rack and a plurality of pressing plates arranged circumferentially, wherein the rotary rack is configured to rotate such that each of the plurality of vessels is located in a position wherein the holder of the vessel faces a pressing plate.

17. Use of the thermal insulator as defined in claim 13 in boilers, water heaters and / or cooking burners.

18. Use of the thermal insulator as defined in claim 13 in electric batteries.

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